Finished Student Theses at Communication Systems
Student theses (BSc, MSc)
@mastersthesis{diva2:1519509,
author = {Svensson, Carolin},
title = {{Anomaly Detection in Encrypted WLAN Traffic}},
school = {Linköping University},
type = {{LiTH-ISY-EX--20/5342--SE}},
year = {2020},
address = {Sweden},
}
This thesis studies the physical layer (PHY layer) of the IEEE 802.11n wireless local area network (WLAN) standard. The possibility of integrating a receiver designed according to the standard with software-defined radios is investigated. The proposed design was implemented in MATLAB and tested using two softwaredefined radios. One of the radios transmitted IEEE 802.11n signals whilst the other one captured them and sent them to a computer for decoding. In this way, evaluation of the proposed receiver design was done. The tests resulted in successfully decoded WLAN packets, although errors occured regularly due to distortions in the air. The proposed MATLAB design can be developed further, with more features, for future tests and research.
@mastersthesis{diva2:1477401,
author = {Ödquist, Matilda},
title = {{Software-Defined Radio Receiver for IEEE 802.11n}},
school = {Linköping University},
type = {{LiTH-ISY-EX--20/5338--SE}},
year = {2020},
address = {Sweden},
}
Synchronization of distributed time difference of arrival (TDOA) sensor networks can be performed using reference signals from GPS satellites. This method provides high accuracy, but is vulnerable to jamming, and is not reliable enough to be used in military applications. A solution that does not depend on any signals transmitted from external actors is preferred. One way to achieve this is to use reference signals transmitted from a UAV. A UAV is suitable since only local synchronization for a geographically restricted area is necessary. The local synchronization is achieved by estimating the time-delay between the transmission and reception of a reference signal. The estimated time-delay can be used to detect drifts in the clocks of the TDOA sensors. This thesis analyzes com- mon reference signals, to evaluate which provide high accuracy for time-delay estimation, and what properties of the signals influence the estimation accuracy the most. The simulations show that the time-delay estimation performance can reach the same accuracy as synchronization against GPS for different types of signals. An increased bandwidth is more important than an increased signal length or signal-to-noise ratio to improve the estimation accuracy.
@mastersthesis{diva2:1443875,
author = {Hult, Alfred},
title = {{Time Synchronization of TDOA Sensors Using a Local Reference Signal}},
school = {Linköping University},
type = {{LiTH-ISY-EX--20/5318--SE}},
year = {2020},
address = {Sweden},
}
Wireless underwater acoustic (UWA) communications is a developing field with various applications. The underwater acoustic communication channel is very special and its behavior is environment-dependent. The UWA channel is characterized by low available bandwidth, and severe motion-introduced Doppler effectcompared to wireless radio communication. Recent literature suggests that machine learning (ML)-based channel estimation and equalization offer benefits overtraditional techniques (a decision feedback equalizer), in UWA communications. ML can be advantageous due to the difficultly in designing algorithms for UWA communication, as finding general channel models have proven to be difficult. This study aims to explore if ML-based channel estimation and equalization as a part of a sophisticated physical layer structure can offer improved performance. In the study, supervised ML using a deep neural network and a recurrent neural network will be utilized to improve the bit error rate. A channel simulator with environment-specific input is used to study a wide range of channels. The simulations are utilized to study in which environments ML should be tested. It is shown that in highly time-varying channels, ML outperforms traditional techniques if trained with prior information of the channel. However, utilizing ML without prior information of the channel yielded no improvement of the performance.
@mastersthesis{diva2:1442845,
author = {Allander, Martin},
title = {{Channel Equalization Using Machine Learning for Underwater Acoustic Communications}},
school = {Linköping University},
type = {{LiTH-ISY-EX--20/5301--SE}},
year = {2020},
address = {Sweden},
}
In order to achieve Full Duplex (FD) communication, currently studied solutionsfor the commercial sector rely on advanced Self-Interferece Cancellation (SIC)techniques to remove the transmitted signal from the received one. This thesis expandsthe research of these techniques by evaluating their potential usage in militarycommunication scenarios where requirements and conditions are distinct,firstly, by identifying, categorizing and describing a set of previously proposedsic techniques and secondly, by performing a comprehensive simulation andanalysis of two suggested sic techniques as part of a FD transceiver. Though themajority of the considered SIC techniques was determined to be potentially implementablein military FD transceivers, some frequency-dependent techniquesand techniques prohibiting omnidirectional communication could not be used.The simulation and analysis of the two suggested SIC techniques show that undercertain conditions, such as limited transmission power and/or reflective environment,close to complete suppression could be realized even with high nonlineardistortion in the transmit chain.
@mastersthesis{diva2:1376474,
author = {Ranström, Thomas},
title = {{Full Duplex in a Military Scenario:
Feasibility of Practical Implementation}},
school = {Linköping University},
type = {{LiTH-ISY-EX--18/5146--SE}},
year = {2019},
address = {Sweden},
}
A common trend, in general as well as in the field of combat vehicles, is the rapidly increasing demand for data network capacity and even more in transferred data. To handle this increased demand, different countries with their armed forces and equipment manufacturers evaluate methods to increase the data transmission capacity in combat vehicles. The different types of transmitted data are of different criticality and have different security demands. An easy solution to this is to have separated networks for each type of traffic, but that is quite expensive and uses a lot of hardware. This thesis focuses on a different solution, with a shared network for all types of data transmissions.
This is done by evaluating different types of data networks and add-on protocols and then testing the networks practically with varying transmission rates. In the thesis, all the practical testing is done with data networks according to the Ethernet standard, which is the standard evaluated with a throughput that is high enough for the use case. Ethernet as a standard is not suitable for critical data traffic and therefore add-on protocols for Ethernet to optimize the system for critical data traffic are tested. With these optimizations made, Ethernet can be considered more suitable for critical traffic, but this depends entirely on the system requirements.
@mastersthesis{diva2:1375044,
author = {Nilsson, Håkan},
title = {{Reliable Communication of Time- and Security-Sensitive Information over a Single Combat Vehicle Network}},
school = {Linköping University},
type = {{LiTH-ISY-EX--19/5268--SE}},
year = {2019},
address = {Sweden},
}
As wireless communications is becoming an increasingly important part of ourevery day lives, the amount of transmitted data is constantly growing, creating ademand for ever-increasing data rates. One of the technologies used for boostingdata rates is carrier aggregation, which allows for wireless units to combine multipleconnections to the cellular network. However, there is a limited number ofpossible combinations defined, meaning that there is a need to search for the bestcombination in any given setup. This thesis introduces software capable of organizingthe defined combinations into tree structures, simplifying the search foroptimal combinations as well as allowing for visualizations of the connectionspossible. In the thesis, a proposed method of creating these trees is presented,together with suggestions on how to visualize important combination characteristics.Studies has also been made on different tree traversal algorithms, showingthat there is little need for searching through all possible combinations, but thata greedy approach has a high performance while substantially limiting the searchcomplexity.
@mastersthesis{diva2:1349222,
author = {Helders, Fredrik},
title = {{Visualizing Carrier Aggregation Combinations}},
school = {Linköping University},
type = {{LiTH-ISY-EX--19/5231--SE}},
year = {2019},
address = {Sweden},
}
Drone usage is increasing, both in recreational use and in the industry. With it comes a number of problems to tackle. Primarily, there are certain areas in which flying drones pose a security threat, e.g., around airports or other no-fly zones. Other problems can appear when there are drones in mobile networks which can cause interference. Such interference comes from the fact that radio transmissions emitted from drones can travel more freely than those from regular UEs (User Equipment) on the ground since there are few obstructions in the air. Additionally, the data traffic sent from drones is often high volume in the form of video streams. The goal of this thesis is to identify so-called "rogue drones" connected to an LTE network. Rogue drones are flying drones that appear to be regular UEs in the network. Drone identification is a binary classification problem where UEs in a network are classified as either a drone or a regular UE and this thesis proposes machine learning methods that can be used to solve it. Classifications are based on radio measurements and statistics reported by UEs in the network. The data for the work in this thesis is gathered through simulations of a heterogenous LTE network in an urban scenario. The primary idea of this thesis is to use a type of cascading classifier, meaning that classifications are made in a series of stages with increasingly complex models where only a subset of examples are passed forward to subsequent stages. The motivation for such a structure is to minimize the computational requirements at the entity making the classifications while still being complex enough to achieve high accuracy. The models explored in this thesis are two-stage cascading classifiers using decision trees and ensemble learning techniques. It is found that close to 60% of the UEs in the dataset can be classified without errors in the first of the two stages. The rest is forwarded to a more complex model which requires more data from the UEs and can achieve up to 98% accuracy.
@mastersthesis{diva2:1326033,
author = {Alesand, Elias},
title = {{Identification of Flying Drones in Mobile Networks using Machine Learning}},
school = {Linköping University},
type = {{LiTH-ISY-EX--19/5222--SE}},
year = {2019},
address = {Sweden},
}
With wireless signals, it is possible to send all kind of data through a communication system. Many companies today having problems implementing wireless communication system because of big areas and many obstacles that blocks the wireless signals. Recent releases of mesh network standards that has the main objective to provide a network over a large area. Toyota Material Handling Europe (TMHE) that develops and produce trucks is one company that wants to use this new network topology to get to the next level of communication.
TMHE is developing a new communication system between their trucks and the goal is to be independent of Wi-Fi and fixed structures in an industry. The aim is to establish communication through Bluetooth and create a mesh network between the trucks at a site. This kind of communication can create many new possibilities for new features, which can make the daily work easier.
The problem with obstacles and interferences is still a problem and TMHE created a thesis to research Bluetooth mesh networks to see if this kind of implementation is suitable for the environments that exists in an industry. This thesis research the architecture of a Bluetooth mesh network and different setups of a network and tests how it stands in an industry with many different surrounding.
@mastersthesis{diva2:1277256,
author = {berglund, Mattias},
title = {{Bluetooth LE Mesh Network in an Industrial Environment}},
school = {Linköping University},
type = {{LiTH-ISY-EX-ET--18/0483--SE}},
year = {2018},
address = {Sweden},
}
This project consists of analyzing and finding solutions to the effect of non-linear distortionon the performance of a Massive Multiple Input Multiple Output (MIMO) system interms of Spectral Efficiency (SE) and Symbol Error Rate (SER). Massive MIMO is one ofthe technologies that are considered the backbone of the 5th generation of wireless communicationsand therefore this technology has gathered much interest from researchersand companies alike [19], as it is proven that this kind of system greatly improves thecapacity of the wireless connection [8]. Since Massive MIMO is still a relatively newtechnology and it is yet to be implemented for commercial use, there are several challengesthat arise when trying to implement such a system. One of these problems arisefrom the fact that the Power Amplifiers (PAs) in the transmitters of Massive MIMO systemsare non-linear and thus impose a distortion on the transmitted signals of the system[12]. The thesis aims to study this non-linear effect on the performance of massive MIMOsystems by first modelling the distortion effect on the transmitted signals using two differentnon-linear models. Moreover, closed-form expressions for one of the models areformed to facilitate the simulation of the non-linear model and facilitate the analysis ofthe distortion effect on the performance metrics. Then the established system model issimulated and based on the results, the effect of each of the power amplifier non-lineardistortion models on the performance metrics of the Massive MIMO system is studied.Furthermore, based on the analysis of the simulation results, a compensation mechanismis introduced to the Massive MIMO system in order to mitigate the distortion effect onthe system performance in terms of SER and SE.
@mastersthesis{diva2:1273924,
author = {Fayad, Adel},
title = {{Analysis and Compensationfor Clipping-like Distortion of the Transmitted Signal in Massive MIMO Systems}},
school = {Linköping University},
type = {{LiTH-ISY-EX--18/5161--SE}},
year = {2018},
address = {Sweden},
}
When transmitting data from an aircraft being prepared at the apron (the area in front of the hangar) telemetry data is transmitted to ground personnel. The transmitted data is subject to severe distortion due to multipath propagation created by the surroundings, resulting in erroneous detection. By equalizing the signal using the Constant Modulus Algorithm a significant increase in detection performance has been observed, both in simulations and tests on collected data. The most sufficient parameters were chosen after testing a set of different parameter combinations on simulations with single delays. These parameters were then used to equalize simulated multipath as well as collected data. The results show that short delays with low power can be resolved without any equalizer. Longer delays with relatively low power can be resolved using the proposed equalizer but long delays with high power cannot be resolved by the equalizer at all. The thesis shows that it is worth investigating implementation of the equalizer.
@mastersthesis{diva2:1252119,
author = {Söderström, Emma},
title = {{Reducing Effects of Multipath Propagation With a Blind Equalizer}},
school = {Linköping University},
type = {{LiTH-ISY-EX--18/5171--SE}},
year = {2018},
address = {Sweden},
}
From the first generation, 1G, to the fourth generation, 4G, the development and technological advancements in telecommunications network systems have been remarkable. Faster and better connections have opened up for new markets, ideas and possibilities, to that extent that there now is a demand that surpasses the supply. Despite all these advancements made in the mobile communications field most of the concept of how the technology works and its infrastructure has remained the same. This however, is about to change with the introduction of the fifth generation (5G) mobile communication.
With the introduction of 5G much of the technology introduced will be different from that of previous generations. This change extends to include the entire infrastructure of the mobile communications system. With these major changes, many of the tools available today for telecommunications network evaluation do not really suffice to include the 5G network standard. For this reason, there is a need to develop a new kind of tool that will be able to include the changes brought by this new network standard.
In this thesis a simulation framework adapted for the next generation telecommunication standard 5G is set to be developed. This framework should include many of the characteristics that set 5G aside from previous generations.
@mastersthesis{diva2:1230756,
author = {Olsson, Joel and Asante, Junior},
title = {{5G Simulation Framework}},
school = {Linköping University},
type = {{LiTH-ISY-EX--18/5149--SE}},
year = {2018},
address = {Sweden},
}
In video transmission there is a need to compose a wide-band signal from a numberof narrow-band sub-signals. A flexible solution offers the possibility to place any narrow-band sub-signal anywhere in the wide-band signal, making better use of the frequency space of the wide-band signal. A multi-standard supportive solution will also consider the three standard bandwidths of digital and analog video transmissions, both terrestrial and cable (6; 7 and 8 MHz), in use today.
This thesis work will study the efficiency of a flexible aggregation solution, in terms of computational complexity and error vector magnitude (EVM). The solution uses oversampled complex modulated filter banks and inner channelizers, to reduce the total workload on the system.
Each sub-signal is channelized through an analysis filter bank and together all channelized sub-signals are aggregated through one synthesis filter bank to form the wide-band composite signal. The EVM between transmitted and received sub-signals are investigated for an increasing number of sub-signals.
The solution in this thesis work is performing good for the tested number of up to 100 narrow-band sub-signals. The result indicates that the multi-standard flexible aggregation solution is efficient for an increasing number of transmitted sub-signals.
@mastersthesis{diva2:1228296,
author = {Nor\'{e}n, Andreas},
title = {{All-Digital Aggregator for Multi-Standard Video Distribution}},
school = {Linköping University},
type = {{LiTH-ISY-EX--18/5129--SE}},
year = {2018},
address = {Sweden},
}
Radio networks are expanding, becoming more advanced, and pushing the limits of what is possible. Services utilizing the radio networks are also being developed in order to provide new functionality to end-users worldwide. When discussing 5G radio networks, concepts such as driverless vehicles, drones and near zero communication delay are recurrent. However, measures of delay are needed in order to verify that such services can be provided -- and measuring this is an extensive task. Ericsson has developed a platform for simulating a radio environment surrounding a radio base station. Using this simulator, this project involved measuring one-way packet delay in a radio network, and performing a Quality of Service evaluation of a radio network with a number of network applications in concern. Application data corresponding to video streams, or Voice over IP conversations, were simulated and packet delay measurements were used to calculate and evaluate the Quality of Service provided by a radio network. One of the main conclusions of this project was that packet delay variations are asymmetric in uplink, which suggests usage of non-conventional jitter measurement techniques.
@mastersthesis{diva2:1218215,
author = {Fahlborg, Daniel},
title = {{Measuring one-way Packet Delay in a Radio Network}},
school = {Linköping University},
type = {{LiTH-ISY-EX--18/5144--SE}},
year = {2018},
address = {Sweden},
}
The work is devoted in the development and the exploration of the capabilities of the state of art unlicensed 60GHz (V-Band) mm-wave band that has raised so much interest and attention from numerous companies and laboratories for implementing Multi-gigabit communications [17] and especially for the 5th generation of cellular network and wireless systems. Implementing a high wireless data transfer system requires a high bandwidth and the one around the 60GHz frequency turned out to be a very promising candidate [13]. In this thesis, different protocols were investigated and simulated on MATLAB and implemented on low-cost Field-Programmable Gate Arrays (FPGAs) in order to test its performance with different transmission protocols and systems and insure a robust communication system at the frequency band around 60GHz. Furthermore, the system was tested with a series of different binary sequences such as pseudo-random bi-nary sequences (PRBS-7, PRBS-15, PRBS-23 and PRBS-31) and a high data rate communication link also in the design. The link has been tested in the lab environment and two systems have successfully achieved a relatively low bit-error rate.
@mastersthesis{diva2:1203832,
author = {Jaoua, Mohamed},
title = {{Development of an FPGA-based High-Speed Wireless Communication System in the 60GHz Frequency Band For CERN facilities and 5G deployment}},
school = {Linköping University},
type = {{LiTH-ISY-EX--18/5112--SE}},
year = {2018},
address = {Sweden},
}
Screen content coding is used to improve coding efficiency of synthetic contents in videos, such as text and UI elements, as opposed to contents captured using photo-graphic equipment, which most video codecs are optimized for. One way of improving screen content coding efficiency is to utilize mixed block coding with matching pursuit. By separating the prediction and transformation steps for overlay and background elements, better contrast and signal-to-noise ratio can be achieved. The paper describes the implementation of such algorithm within the HEVC reference encoder, and discusses the experimental results on several test images.
@mastersthesis{diva2:1181918,
author = {Yang, Ching-Hsiang},
title = {{Screen Content Coding in HEVC:
Mixed Raster Content with Matching Pursuit}},
school = {Linköping University},
type = {{LiTH-ISY-EX--17/5105--SE}},
year = {2017},
address = {Sweden},
}
Narrowband Internet-of-Things (NB-IoT) is a new wireless technology designed to support cellular networks with wide coverage for a massive number of very cheap low power user devices. Studies have been initiated for deployment of NB-IoT in unlicensed frequency bands, some of which demand the use of a frequency-hopping scheme with a short channel dwell time. In order for a device to connect to a cell, it must synchronize well within the dwell time in order to decode the frequency-hopping pattern. Due to the significant path loss, the narrow bandwidth and the device characteristics, decreasing the synchronization time is a challenge. This thesis studies different methods to decrease the synchronization time for NB-IoT without increasing the demands on the user device. The study shows how artificial fast fading can be combined with denser reference signalling in order to achieve improvements to the cell acquisition and synchronization procedure sufficient for enabling unlicensed operation of NB-IoT.
@mastersthesis{diva2:1134090,
author = {Jörgensen, Eskil},
title = {{Cell Acquisition and Synchronization for Unlicensed NB-IoT}},
school = {Linköping University},
type = {{LiTH-ISY-EX--17/5082--SE}},
year = {2017},
address = {Sweden},
}
In this thesis a known heuristic for decreasing a node's centrality scores while maintaining influence, called ROAM, is compared to a modified version specifically designed to decrease eigenvector centrality. The performances of these heuristics are also tested against the Shapley values of a cooperative game played over the considered network, where the game is such that influential nodes receive higher Shapley values. The modified heuristic performed at least as good as the original ROAM, and in some instances even better (especially when the terrorist network behind the World Trade Center attacks was considered). Both heuristics increased the influence score for a given targeted node when applied consecutively on the WTC network, and consequently the Shapley values increased as well. Therefore the Shapley value of the game considered in this thesis seems to be well suited for discovering individuals that are assumed to actively trying to evade social network analysis.
@mastersthesis{diva2:1117970,
author = {Abrahamsson, Olle},
title = {{Hide and Seek in a Social Network}},
school = {Linköping University},
type = {{LiTH-ISY-EX--17/5038--SE}},
year = {2017},
address = {Sweden},
}
The next generation of mobile networks (5G) is currently being standardized, and massive MIMO (Multiple-Input-Multiple-Output) is a strong candidate to be part of this standard. Other than providing higher data rates and lower latency, high accuracy positioning is also required. In this thesis, we evaluate the achievable performance of positioning using massive MIMO systems in open highway scenarios. Relevant theory from sensor array signal processing and Bayesian filtering is presented, and is used in a simulation environment on large antenna arrays representing massive MIMO base stations. Positioning is done by utilizing the uplink pilot reference signals, where the Direction of Arrival (DOA) of the pilot signal is estimated, and then used for position estimation. Estimation of the DOA is done by both a maximum-likelihood method and by using an Extended Kalman Filter (EKF). A positioning error of less than 8 m is achieved with absolute certainty when the vehicle is less than 300 m from the base station. It is also concluded that this result could be improved by using more sophisticated filtering algorithms.
@mastersthesis{diva2:1117917,
author = {Petersson, Markus},
title = {{Performance Assessment of Massive MIMO Systems for Positioning and Tracking of Vehicles in Open Highways}},
school = {Linköping University},
type = {{LiTH-ISY-EX--17/5049--SE}},
year = {2017},
address = {Sweden},
}
Kollektiva beslut blir en del av vardagen när grupper av människor står inför val. Vi anpassar ofta våra personliga övertygelser med hänsyn till våra vänner. Vi är naturligt beroende av lyckan hos dem som står oss nära.
I det här exjobbet undersöker vi en befintlig empatimodell som används för att välja en vinnare från en uppsättning alternativ genom att använda poängbaserade omröstningsprocedurer. Vi visar att en liten modifikation av modellen är tillräcklig för att kunna använda överlägsna omröstningsprocedurer som bygger på parvisa jämförelser av alternativen.
Sammanfattningsvis visar vi att det i grunden inte finns någon anledning att använda poängbaserade omröstningsprocedurer i de föreslagna modellerna, eftersom ett mer önskvärt resultat uppnås genom att använda de överlägsna omröstningsprocedurerna.
@mastersthesis{diva2:1117841,
author = {Becirovic, Ema},
title = {{On Social Choice in Social Networks}},
school = {Linköping University},
type = {{LiTH-ISY-EX--17/5042--SE}},
year = {2017},
address = {Sweden},
}
To enable wireless control of factories, such that sensor measurements can be sent wirelessly to an actuator, the probability to receive data correctly must be very high and the time it takes to the deliver the data from the sensor to the actuator must be very low. Earlier, these requirements have only been met by cables, but in the fifth generation mobile network this is one of the imagined use cases and work is undergoing to create a system capable of wireless control of factories. One of the problems in this scenario is when all data in a packet cannot be sent in one transmission while ensuring the very high probability of reception of the transmission. This thesis studies this problem in detail by proposing methods to cope with the problem and evaluating these methods in a simulator. The thesis shows that splitting the data into multiple segments and transmitting each at an even higher probability of reception is a good candidate, especially when there is time for a retransmission. When there is only one transmission available, a better candidate is to send the same packet twice. Even if the first packet cannot achieve the very high probability of reception, the combination of the first and second packet might be able to.
@mastersthesis{diva2:1111797,
author = {Fax\'{e}n, Linnea},
title = {{A Study on Segmentation for Ultra-Reliable Low-Latency Communications}},
school = {Linköping University},
type = {{LiTH-ISY-EX--17/5039--SE}},
year = {2017},
address = {Sweden},
}
The positioning performance with the LVC (Last Visited Cells) report is evaluated and compared with extended reports with signal strength data. The LVC report contains cell identities and time spent in the last cells listened to. This is an off-line data source and the purpose of the positioning is to extract information about users’ whereabouts, which for example can be used to optimize the cellular network or vehicular traffic. The positioning evaluation is done in Matlab with a log-distance model, a fingerprinting algorithm, and a new LVC specific algorithm. A particle filter and a particle smoother is used to process simulated LVC reports and extended reports with different amount of information. The results are compared and evaluated with regard to the positioning accuracy and the information density of the reports.
@mastersthesis{diva2:1111258,
author = {Olofsson, Tor},
title = {{Network-Based Positioning Using Last Visited Cells Report}},
school = {Linköping University},
type = {{LiTH-ISY-EX--17/5040--SE}},
year = {2017},
address = {Sweden},
}
A radar works by radiating electromagnetic energy and detecting the reflected signal returned from the target. The nature of the reflected signal provides information about the target’s distance or speed. In this thesis, we will be using a UWB radar and a CW radar to help detect the presence and rough location of trapped survivors by detecting their motions. Range is estimated in the UWB radar using clutter removal with SVD and for the dual frequency CW Radar using STFT and median filtering. The effect of the algorithm parameters on their performance was analyzed. The performance of the implemented algorithms with regards to small motion detection, distance estimation and penetration capability was analyzed. Both systems are certainly capable of human detection and tracking.
@mastersthesis{diva2:1105224,
author = {Ahmed, Atheeq},
title = {{Human Detection Using Ultra Wideband Radar and Continuous Wave Radar}},
school = {Linköping University},
type = {{LiTH-ISY-EX--17/5026--SE}},
year = {2017},
address = {Sweden},
}
One option for enabling mobility between 5G nodes is to use a set of area-fixed reference beams in the downlink direction from each node. To save power these reference beams should be turned on only on demand, i.e. only if a mobile needs it. An User Equipment (UE) moving out of a beam's coverage will require a switch from one beam to another, preferably without having to turn on all possible beams to find out which one is the best.
This thesis investigates how to transform the beam selection problem into a format suitable for machine learning and how good such solutions are compared to baseline models. The baseline models considered were beam overlap and average Reference Signal Received Power (RSRP), both building beam-to-beam maps. Emphasis in the thesis was on handovers between nodes and finding the beam with the highest RSRP. Beam-hit-rate and RSRP-difference (selected minus best) were key performance indicators and were compared for different numbers of activated beams.
The problem was modeled as a Multiple Output Regression (MOR) problem and as a Multi-Class Classification (MCC) problem. Both problems are possible to solve with the random forest model, which was the learning model of choice during this work. An Ericsson simulator was used to simulate and collect data from a seven-site scenario with 40 UEs. Primary features available were the current serving beam index and its RSRP. Additional features, like position and distance, were suggested, though many ended up being limited either by the simulated scenario or by the cost of acquiring the feature in a real-world scenario.
Using primary features only, learned models' performance were equal to or worse than the baseline models' performance. Adding distance improved the performance considerably, beating the baseline models, but still leaving room for more improvements.
@mastersthesis{diva2:1088857,
author = {Ekman, Björn},
title = {{Machine Learning for Beam Based Mobility Optimization in NR}},
school = {Linköping University},
type = {{LiTH-ISY-EX--17/5024--SE}},
year = {2017},
address = {Sweden},
}
Localization is one of the most interesting research areas in wireless networks. It is mostly used for tracking and monitoring applications such as traffic monitoring, search and rescue, navigation and so on. A good quality system can be defined from its accuracy when operating in severe interference environments that contaminate the signals and therefore reduce the system performance. The main issue for localization is channel propagation, e.g., line of sight or non-line of sight channel which should be studied in order to improve the system efficiency.
In order to perform a localization, most algorithms use two steps: ranging and positioning. For ranging, the two popular techniques that are widely used for distance measurement are received signal strength (RSS) and time of arrival (TOA). RSS ranging technique uses the power of the received signals to identify the distance between a transmitter and a receiver. TOA ranging technique uses time of the signal traveling between a transmitter and a receiver to identify the distance, thus it requires synchronization. The measurements are processed by using a localization algorithm afterwards. However, these techniques suffer from multipath fading and other errors, so there always exists error in the estimated position.
In this thesis, TOA ranging technique is used for different estimation methods. Simulation results are performed using MATLAB, while the real results are obtained from Pozyx indoor positioning platform. Several estimation algorithms comprising of maximum likelihood (ML), linearized least square (LLS), weighted centroid (WC), and fingerprinting (FP) are studied in detail. The testing area is indoor environment which is suitable for LOS, NLOS and combined situations. The measured data is then used for ranging and localization. We concentrate on comparing and discussing these results in this thesis.
@mastersthesis{diva2:1055816,
author = {Sookyoi, Thiti},
title = {{Experimental Analysis of Indoor Positioning System Based on Ultra-Wideband Measurements}},
school = {Linköping University},
type = {{LiTH-ISY-EX--16/4991--SE}},
year = {2016},
address = {Sweden},
}
This report presents an implementation of the software part in a software definedradio. The radio is not entirely implemented in software and therefore there arecertain limitations on the received signal. The parts implemented are oscillator,decimation filter, carrier synchronization, time synchronization, package detection,and demodulation. Different algorithms were tested for the different partsto measure the power consumption. To understand how the number of bits usedto represent the signal affects the power consumption, the number of bits wasreduced from 20 bits to 10 bits. This reduction reduced the power consumptionfrom 2.57mW to 1.89mW. A small change in the choice of algorithms was thenmade which reduced the power consumption to 1.86mW. Then the clock rate wasreduced for some parts of the system which reduced the power consumption to1.05mW.
@mastersthesis{diva2:1044579,
author = {Skärpe, Anders},
title = {{Implementation of an SDR in Verilog}},
school = {Linköping University},
type = {{LiTH-ISY-EX--16/5001--SE}},
year = {2016},
address = {Sweden},
}
By using existing radio network infrastructure, a user can be positioned even where GPS and other positioning technologies lack coverage. The LTE Positioning Protocol (LPP) supports user Reference Signal Time Difference (RSTD) reports based on the Time of Arrival (TOA) for a Positioning Reference Signal (PRS). In the current reporting format, only one RSTD for each base station is considered, but for indoor environments this is easily biased due to fading and multipath issues, resulting in a Non-Line of Sight (NLOS) bias. With a rich User Equipment (UE) feedback that can represent the multipath channel for each Base Station (BS), the positioning accuracy can be increased. This thesis develops and evaluates a UE reporting format representing multiple TDOA candidates, and a probabilistic positioning algorithm, in terms of positioning accuracy and amount of data reported. By modeling time measurements as Gaussian Mixture (GM), the time information can be compressed with arbitrary resolution and used in a Maximum-Likelihood (ML) estimation to find the position. Results were obtained through simulation in a radio network simulator and post-processing of simulation data in Matlab. The results suggest that several TOA candidates improve the positioning accuracy, but that the largest improvement comes from a noise based threshold by increasing LOS detectability reducing the NLOS bias, while suppressing noise. The results also suggest that the accuracy for the method can be further improved by combining multiple time measurement occasions.
@mastersthesis{diva2:1033724,
author = {Olofsson, Ivar},
title = {{Enhancements in LTE OTDOA Positioning for Multipath Environments}},
school = {Linköping University},
type = {{LiTH-ISY-EX--16/4950--SE}},
year = {2016},
address = {Sweden},
}
The 5th generation mobile telecommunication system (5G) is currently being specified and developed, with large expectations on throughput and efficiency. While 4G and more specifically LTE might constitute a basis of the design of the network, there are some parts that should be improved. One thing to improve is the static signalling that occurs very frequently in a 4G network, of which system information such as synchronization signals, detection of network frequencies, operators, configurations etc. is a part. It has been shown that the static signalling requires both much energy and time-frequency resources. Since the system information is not intended for a single user it is always broadcast so that any user, and any amount of users can read it when needed. 5G will use a technique called massive MIMO, where the base station is equipped with a large number of antennas which can be used to direct signals in space, called beamforming. This thesis presents a new method for distribution of system information that can utilize the beamforming capabilities of massive MIMO. A simple model together with simulated user channel statistics from urban 4G scenarios are used to show that the new method outperforms the classical method of only broadcasting the information, with respect to time-frequency resources. Especially if there are high requirements on the latency of the system information, the new method results in a large gain.
@mastersthesis{diva2:937593,
author = {Sörman, Simon},
title = {{System Information Distribution in Massive MIMO Systems}},
school = {Linköping University},
type = {{LiTH-ISY-EX--16/4952--SE}},
year = {2016},
address = {Sweden},
}
The ability for base stations to be able to beam-form their signals, directing the signal energy to specific users, is a topic of research that has been heavily studied during the last decades. The beam-forming technique aims to increase the signal-to-interference-and-noise-ratio of the user and, consequently, increase the capacity and coverage of the communication system. One such method is the Differential Beam-Forming technique, that has been developed at Ericsson Research. In this version of beam-forming, the beams can be dynamically sharpened and widened when tracking a specific terminal, to try to optimize the signal energy sent to that terminal.
Beam-forming, however, makes the link-adaptation algorithm process substantially harder to perform. The reason for this is that the link-adaptation algorithm now has to take into account not only the changing radio environment, but also the changing transmit signal that is being beam-formed. Fortunately, since the beam-formed signal is known at the point of transmission, there should be a potential to utilize this knowledge to make the link-adaptation more efficient.
This thesis, investigates how the link-adaptation algorithm could be changed to perform better in beam-forming setups, as well as what information from the beam-forming algorithm that could be included and utilized in the link-adaptation algorithm. This is done by designing and investigating three new link-adaptation algorithms, in the context of Differential Beam-Forming in an LTE FDD system. The algorithms that has been designed are both of a beam-forming-aware and beam-forming-unaware character, meaning if the beam-forming information is utilized within the algorithm, or not. These algorithms have been simulated for different base station antenna array-sizes. Unfortunately, due to simulator restrictions, the terminals have been simulated in a stationary environment, which has proven to be a limiting factor for the results. However, the results still show that smarter beam-forming-aware link-adaptation could possibly be used to increase the performance of the link-adaptation when using beam-forming.
@mastersthesis{diva2:935754,
author = {Karlsson, Mikael},
title = {{Beam-Forming-Aware Link-Adaptation for Differential Beam-Forming in an LTE FDD System}},
school = {Linköping University},
type = {{LiTH-ISY-EX--16/4946--SE}},
year = {2016},
address = {Sweden},
}
Internet of Things (iot) is a growing field enabled by many different technologies. One of these technologies is Bluetooth Low Energy (ble). It is of interest to investigate the potential of ble and one interesting, currently unsupported, feature is mesh networking. This thesis work aims to investigate whether it is possible to design and implement a mesh network protocol using ble. To verify the implemented mesh network protocols functionality an indoor localization system has been implemented upon the BLE mesh network protocol. Furthermore this thesis work investigates if an indoor localization system can benefit from using a mesh network. The results of the investigation is a proof of concept of a functional ble mesh network protocol implemented on hardware and tested in a real environment. Tests show that the implemented localization system has similar accuracy as other rssi based indoor localization systems. The largest advantage found for a mesh based indoor localization is the ability to localize objects outside of the radio propagation range of the user. This feature is enabled by multi-hop messaging in the mesh network.
@mastersthesis{diva2:935745,
author = {Silver, Oscar},
title = {{An Indoor Localization System Based on BLE Mesh Network}},
school = {Linköping University},
type = {{LiTH-ISY-EX--16/4948--SE}},
year = {2016},
address = {Sweden},
}
Massive multiple-input-multiple-output (MIMO) is a wireless communication technologythat usesa large number of antennas at the base station and servesmultiple terminals over the same time-frequency resource.This technique can achievehigher data rates than existing communication technology, which only serves one terminal per resource. That is why Massive MIMO is considered a promising candidate for 5G. Orthogonal frequency division multiplexing (OFDM) can be used for transmitting information at different sub-channels. The cyclic prefix (CP) is a repetition of the last samples in a symbol, which is appended at the beginning of the symbol.It serves as a guard interval between consecutive symbols to avoid inter-symbol interference (ISI) and to make sub-channels orthogonal. In this thesis it is proposed to shorten the CP length in Massive MIMO. The shortening of the CP length will increase the effective spectral efficiency but also create additional interference. This trade-off is investigated. A simulation based study is performed to analyse the effective achievable rate of anuplink Massive MIMO system in a single-cell scenario when 10000 Gaussian symbols are transmitted.In the simulation, the number of sub-channels is 128. They are transmitted through a channel with 10 taps. With the classical CP length9samples and a massive MIMO base stationwith 50 antennas serving 3 terminals,the effective achievable rate was 3.863 bits/s/Hz. It was found thatthe effective achievable rate is maximized when the CP length is shortened to 6 samples; the effective achievable rate then became 4.112 bits/s/Hz.In the same system when 100 antennas are used, the corresponding effective achievable rates are 4.791 bits/s/Hz and 4.895 bits/s/Hz with an optimum CP lengthof5 samples. It is shown that the optimum CP length in Massive MIMO is not equal to the number of taps minus one which is the conventional choice. Yes, the CP is needed in Massive MIMO, but it can be shorter than conventionally.
@mastersthesis{diva2:934227,
author = {Nsengiyumva, Valens},
title = {{Is the Cyclic Prefix Needed in Massive MIMO?}},
school = {Linköping University},
type = {{LiTH-ISY-EX--16/4936--SE}},
year = {2016},
address = {Sweden},
}
Loudness is a subjective measure of how loud an audio signal is perceived. Due to commercial pressures loudness has been exploited in broadcasts to attract and reach viewers and listeners. By means of signal processing it is possible to increase the loudness of an audio signal and still meet the contemporary legislated signal levelling requirements. With an aspiration to achieve equal average loudness between all broadcasting programmes the European Broadcasting Union have issued a standard that proposes methods to quantify loudness. This thesis applies those loudness quantities and proposes an online algorithm that adaptively normalises the loudness of audiovisual broadcasts without affecting the dynamics within programmes. The main application of the algorithm is to normalise the audio in broadcasting and distributing equipment with real-time requirements. The results were derived from simulations in Matlab using commercial broadcasts. The results showed that for certain types of broadcasts the algorithm managed to reduce the variation in average programme loudness with minor effects on dynamics within programmes.
@mastersthesis{diva2:932719,
author = {Molinder, Herman},
title = {{Adaptive Normalisation of Programme Loudness in Audiovisual Broadcasts}},
school = {Linköping University},
type = {{LiTH-ISY-EX--16/4947--SE}},
year = {2016},
address = {Sweden},
}
Wireless technologies and networks are a part of our daily lives and we are surrounded by a constant stream of wireless signals. Unfortunately, there are a lot of limitations. At Toyota Material Handling Europe, future demands and expectations are raising but the technologies available today are not adapting fast enough. Indoor factory environments, moving network nodes and rapidly changing topologies are demanding situations. In this new Internet of Things day and age, transferring information in these challenging environments, the standard master and slave configuration is not enough.
This report looks at the specific challenges establishing a wireless communication link between trucks in an indoor factory and warehouse environment. There are many factors to consider. Antennas, noise, frequency bands, different network technologies, propagation and path loss modeling to mention a few.
Antennas and on-the-truck antenna positioning require design choices to be made. If we want to benefit from using high gain antennas, positioning is an important factor. Noise, in the highly congested 2.4 GHz band is a problem, especially considering safety critical applications. The license free ISM frequency bands have all different advantages in range, available communication protocols and amount of other technologies sharing the spectrum.
The Wi-Fi, Bluetooth, ZigBee and V2X technologies looked at, tailored to the particular case of a warehouse environment like the Toyota factory, and the final selection relates to potential use case scenarios. Prioritizing, scalability, ad hoc network topologies, low latencies and short connection times together with long range, the new V2X technology building upon the IEEE 802.11p standard stands out.
This report evaluates the IEEE 802.11p wireless standard running the ETSI ITS G5 V2X protocol in an indoor factory and warehouse environment. Thanks to Kapsch and their EVK-3300 V2X Evaluation Kit it was possible to evaluate transferring information between nodes, the PSR, and looking at how useful different path loss models are for estimating relative distances between trucks.
@mastersthesis{diva2:926722,
author = {Mustovic, Adam},
title = {{Wireless Information Transfer in an Indoor Factory or Warehouse Environment}},
school = {Linköping University},
type = {{LiTH-ISY-EX--16/4934--SE}},
year = {2016},
address = {Sweden},
}
Digital predistortion is a signal processing technique used to remove undesired distortions caused by nonlinear system effects. This method is predominately used to linearize power amplifiers in communication systems in order to achieve efficient transmitter circuits. However, the technique can readily be applied to cancel undesired nonlinear behavior in other types of systems.
This thesis investigates the effectiveness of digital predistortion in the context of a wideband arbitrary waveform generator. A theoretical foundation discussing nonlinear system models, predistortion architectures and system identification methods is complemented with a simulation study and followed by verification on a real system.
The best predistorter is able to fully suppress the undesired distortions for any fixed two-tone sinusoidal signal. Furthermore, the results indicate the existence of a wideband predistorter which yield acceptable suppression over a frequency range of several hundred MHz.
@mastersthesis{diva2:897079,
author = {Eriksson, Marcus},
title = {{Analysis of Digital Predistortion in a Wideband Arbitrary Waveform Generator}},
school = {Linköping University},
type = {{LiTH-ISY-EX--15/4909--SE}},
year = {2015},
address = {Sweden},
}
The usage of wireless technology has in the past decade vastly increased and it continues to do so as well. Because of this, we become more and more reliant on this considerably fragile technology. Wireless technology, which uses radio waves to transmit data from one point to another can easily be interfered by radio jammers. This thesis work is about the detection and classification of the interference that is produced by jammers over the Global System for Mobile Communications (GSM) air interface. A typical GSM jammer that can be found on the Internet is analyzed but also more advanced GSM jammers are analyzed. The GSM standard is analyzed to find vulnerabilities that a jammer can take advantage of. The result is an interference detector that can be used to detect and classify interference over the GSM networks. The detector is constructed with an Universal Software Radio Peripheral (USRP) but is also portable to other software-defined radio (SDR) platforms.
@mastersthesis{diva2:888209,
author = {Ring, Christoffer},
title = {{Detection and Classification of Interference in Mobile Communication Systems}},
school = {Linköping University},
type = {{LiTH-ISY-EX--15/4920--SE}},
year = {2015},
address = {Sweden},
}
Internet of Things (IoT) is a scenario that theorizes objects and people as potential nodes in an ever-growing wireless network. This idea pushes the development of low-cost wireless technologies that can run on portable power sources for months, or even years. One candidate technique that has shown promising results in this area thru the last years is BluetoothLow Energy (BLE). This thesis studies various techniques to enable and maintain large scale mesh networks over BLE communication. The initial study puts focus on an existing flooding based BLE mesh protocol. The thesis later presents an improved protocol that reduces power consumption with respect to the packet delivery ratio. Other enhancements which are added to the improved protocol are a self-adapting procedure and a packet routing algorithm. Simulations show that the improved protocol can save up to 50 % of the power consumption for a device, compared to the original protocol.
@mastersthesis{diva2:867937,
author = {Hinrichsen, Oscar},
title = {{An Evaluation of Network Protocols for Bluetooth Low Energy Mesh Networks}},
school = {Linköping University},
type = {{LiTH-ISY-EX--15/4898--SE}},
year = {2015},
address = {Sweden},
}
Voice over IP (VoIP) is the group of techniques for delivering voice communications over Internet Protocol (IP) networks. It has mainly served as the possible substitution for regular PSTN over the last decades, but has recently gained an increased interest in various areas such as alarm applications and customer service. Acoustic echo is the situation were a distorted version of the sent signal is transmitted back to the sender, due to acoustic feedback between loudspeaker and microphone. There already exists several algorithms to solve this problem, and this thesis provides a study of the performance in relation to the computational complexity of the algorithms. This is in order to indicate which approaches are better suited for implementation in an embedded system, where resources are limited. During the thesis a number of algorithms were tested, including variations of the LMS algorithm, some other approaches utilizing the correlation between echo and signal, and the RLS algorithm. They were first tested in MATLAB, on speech signals recorded at Syntronic and distorted by adding echo, then tested by implementation in C, and run on speech signals recorded in a simulated VoIP system at Syntronic. The results were then evaluated in terms of efficiency and computational complexity.
@mastersthesis{diva2:860584,
author = {Eriksson, Anton},
title = {{Robust Echo-Cancellation for Simple VoIP-Applications in Embedded Systems}},
school = {Linköping University},
type = {{LiTH-ISY-EX--15/4886--SE}},
year = {2015},
address = {Sweden},
}
Basstationer med flera antenner kan aktivt styra signalenergi mot en mottagare med hjälp av lobformning, vilket ger högre datatakt och lägre strömförbrukning än med en enda antenn. Lobformning kräver dock att kanalen skattas till varje antenn och i ett FDD-system måste denna skattning återkopplas till basstationen från mottagaren, vilket innebär en opraktiskt stor overhead, speciellt när loberna blir smalare. Differentiell lobformning är en robust teknik som med begränsad overhead möjliggör smala och välriktade lober genom differentiella justeringar av lobformen. Med hjälp av två förkodade referenssignaler från basstationen skattar mottagaren kanalen och rapporterar iterativt hur lobformningen ska förbättras så att SINR hos den mottagna signalen ökar. Den här uppsatsen utvecklar en algoritm som utökar differentiell lobformning till användandet av tvådimensionella antennuppställningar, vilket möjliggör justering av lobformen i två dimensioner och därmed potentiellt sett ökar mottagen signalstyrka. Algoritmen alternerar mellan att differentiellt justera lobformen horisontellt och vertikalt, utan ökad overhead. Algoritmen har testats för olika antennuppställningar i ett stadsscenario och ett landsbygdsscenario med horisontell användarfördelning, vilken dock har visat sig vara en begränsande faktor för att påvisa de potentiella vinster som differentiell lobformning i två dimensioner för med sig. Resultatet visar att det är viktigare att kunna erhålla en smal lob i den dimension där det finns många användare, i detta fall den horisontella dimensionen, än i den ortogonala dimensionen.
@mastersthesis{diva2:853478,
author = {Stenmark, Fredrik},
title = {{Differential Beam-Forming Using Two-Dimensional Antenna Arrays in an LTE FDD System}},
school = {Linköping University},
type = {{LiTH-ISY-EX--15/4851--SE}},
year = {2015},
address = {Sweden},
}
The next generation of mobile telecommunication, 5G, will be specified in the near future. One of the proposed changes relative to the previous generation, 4G,is the inclusion of a new system control plane (SCP). The purpose of the SCP is to improve system scalability, forward compatibility, peak performance and to enable a higher degree of support for advanced antenna techniques. This is done by logically separating data transmitted explicitly from and to the user, the dynamic transmissions, from the broadcasted transmissions that remain constant regardless of user activity, the static transmissions, and by then redesigning the static part to make it more lean. This is expected to have several positive effects such as considerably more free resources, resulting in energy savings and potentially increased usage of MIMO. Knowing what effect the SCP has upon aspects such as random access is of importance when designing the solution that will go into the standard.
Simulations show that there is potential in the inclusion of the new SCP. While the simulated 5G candidate systems that include the SCP have an increased delay when running the random access procedure, some aspects of the procedure have been improved. The main differences relative to the simulated 4G system are the performance of the first message in the procedure, which increased, and the performance of the second message in the procedure, which decreased. The deficiencies found in the handling of the second message, however, can be alleviated by using a more proper algorithm and channel design than what was used in this study.
@mastersthesis{diva2:846229,
author = {Thal\'{e}n, Magnus},
title = {{A Study on Random Access Performance in Next Generation Mobile Network Systems}},
school = {Linköping University},
type = {{LiTH-ISY-EX--15/4850--SE}},
year = {2015},
address = {Sweden},
}
Baseband processing is an important and computationally heavy part of modern mobile cellular systems. These systems use specialized hardware that has many digital signal processing cores and hardware accelerators. The algorithms that run on these systems are complexand needs to take advantage of this hardware. Developing software for these systems requires domain knowledge about baseband processing and low level programming on parallel real time systems. This thesis investigates if the programming language Julia can be used to implement algorithms for baseband processing in mobile telephony base stations. If it is possible to use a scientific language like Julia to directly implement programs for the special hardware in the base stations it can reduce lead times and costs.
In this thesis a uplink receiver is implemented in Julia. This implementation is written usinga domain specific language. This makes it possible to specify a number of transformations that use the metaprogramming capabilities in Julia to transform the uplink receiver such that it is better suited to execute on the hardware described above. This is achieved by transforming the program such that it consists of functions that either can be executed on single digital signal processing cores or hardware accelerators.
It is concluded that Julia seems suited for prototyping baseband processing algorithms. Using metaprogramming to transform a baseband processing algorithm to be better suited for baseband processing hardware is also a feasible approach.
@mastersthesis{diva2:788484,
author = {Mellberg, Linus},
title = {{Baseband Processing Using the Julia Language}},
school = {Linköping University},
type = {{LiTH-ISY-EX--14/4812--SE}},
year = {2015},
address = {Sweden},
}
Sectorization is a well-established method of increasing the capacity of telecommunicationnetworks. With modern Active Antenna Systems (AAS) comes the abilityto change sectorization order dynamically, both in horizontal and vertical plane.The purpose of this thesis is to investigate when (and what type of) sectorizationis benficial. A theoretical analysis as well as simulations are performed in orderto determine which quantities to look at when making the decision to apply sectorization.Based on the conclusions from these investigations, a self-optimizingalgorithm that only turns on sectorization when it increases network performanceis developed and evaluated. It is shown that large gains can be achieved by onlyturning on sectorization when the right conditions are met. Further, we show thatadditional gains can be seen if antenna parameters such as downtilt and distributionof transmission power between sectors are set properly. Self-optimizingalgorithms for tuning of these parameters are developed and evaluated as well.NyckelordKeywords
@mastersthesis{diva2:792666,
author = {Fax\'{e}r, Sebastian},
title = {{Self-optimization of Antenna Sectorization}},
school = {Linköping University},
type = {{LiTH-ISY-EX--14/4763--SE}},
year = {2014},
address = {Sweden},
}
With the increase of the number of radios and antennas on today’s systems, the risk of co-site interference is very high. Intermodulation product and antenna coupling are two common sources of interference. The thesis investigates some features of a radio system, like antenna types, receiver parameters, intermodulation products and isolation, and suggests how this knowledge can be used to minimize the risk of co-site interference. The goal is to maximize the isolation between the antennas, by good frequency planning, the use of filters and taking great care in antenna placement. A first version of an analysis software was developed where transmitters and receivers can be paired and evaluated. An intermodulation product calculator was also implemented, to easily find which products are an issue and where they originate. The goal of the software is to be simple to use and easy to adapt to different setups and situations. It should also be easy to upgrade with new features.
@mastersthesis{diva2:772435,
author = {Carlsson, Robin},
title = {{Investigation and Implementation of Coexistence Tool for Antennas}},
school = {Linköping University},
type = {{LiTH-ISY-EX--14/4785--SE}},
year = {2014},
address = {Sweden},
}
In large warehouses, there are a lot of articles that needs do be kept track of. As the number of articles grows larger, the administrative complexity increases. Thus, a solution that automatically keeps track of the position of each article in real-time is of interest. That is, if an item in the warehouse is moved, no manual administration should be needed to know the new position of the item.
Radio detection and ranging (RADAR) is a ranging technique that doesn’t need to communicate with an object to find the distance to it, instead signals are sent and when they are reflected off the object and returned to the sender, the distance to the object may be calculated. However, you cannot tell two equally shaped objects apart purely based on RADAR techniques. There are many other techniques for ranging, sound navigation and ranging (SONAR) is another example, but they all lack the possibility of detecting the identity of the object.
So, in order to find a specific item’s position, some kind of communication with the item is necessary. Radiofrequency identification (RFID) is a neat technology with which this is possible. An RFID reader can send radio signals out in the air, and objects that are in the vicinity of the reader and are tagged with an RFID tag can receive that signal and respond with it’s unique identification number. This way, the RFID reader can identify the RFID tagged object from a distance. There are also a variety of ways to approximate the distance between reader and tag. Unfortunately this is a rather difficult task, especially in indoor environments.
There are already some existing products on the market that uses RFID for different kinds of positioning. In this thesis, the theory behind positioning, the fundamentals of RFID and different positioning solutions will be analysed and presented.
A number of tests were carried out with an RFID system within the ultra-high frequency (UHF) band, which is around 866 MHz. The test system only supported range estimation based on the received signal strength indicator (RSSI) and the test results showed that narrowband RSSI measurements are highly disturbed by multipath propagation which make the overall positioning performance insufficient. Further analysis of time based range estimation techniques, such as time of arrival (TOA), time of flight (TOF) and time difference of arrival (TDOA), revealed that better positioning accuracy is possible, especially if ultra-wide bandwidth (UWB) is used.
@mastersthesis{diva2:761874,
author = {Karhu, Jonas},
title = {{3-D Positioning in Large Warehouses using Radio-frequency identification}},
school = {Linköping University},
type = {{LiTH-ISY-EX-14/4795-SE}},
year = {2014},
address = {Sweden},
}
Mobile data traffic is growing exponentially due to the popularization of smart phones, tablets and other data traffic appliances. One way of handling the increased data traffic is to deploy large antenna arrays at the base station, also known as Massive MIMO. In Massive MIMO, the base station having excessive number of transmit antennas, can achieve increased data rate by spatial-multiplexing terminals into the same time-frequency resource.
This thesis investigates Massive MIMO in LTE in a single-cell deployment with up to 100 base station antennas. The benefits of more antennas are investigated with single-antenna terminals in a typical urban environment. The terminal transmitted sounding reference signals (SRS) are used at the base station to calculate channel state information (CSI) in order to generate an MRT precoder. With perfect CSI, the results showed that the expected terminal SINR depends on the antenna-terminal ratio. It was also showed that with spatial-multiplexed terminals and 100 base station antennas, the maximum cell throughput increased 13 times compared with no spatial-multiplexed terminals.
Channel ageing causes inaccuracy in the CSI, the thesis showed that the variation in terminal SINR increased rapidly with less frequent SRS transmissions. When having moving terminals at 3 km/h, the difference between the 10th and 90th SINR percentile is 1 dB with an SRS transmission periodicity of 20 ms, and 17 dB with an SRS transmission periodicity of 80 ms. With 100 base station antennas and moving terminals at 3 km/h with an SRS periodicity of 20 ms, the maximum cell throughput decreased with 13% compared to when the base station has perfect CSI.
The result showed that the maximum cell throughput scaled linearly with the number of base station antennas. It also showed that having the number of spatial-multiplexed terminals equal to the number of antennas is a reasonable assumption when maximizing the cell throughput.
@mastersthesis{diva2:748921,
author = {Ryd\'{e}n, Henrik},
title = {{Massive MIMO in LTE with MRT Precoder:
Channel Ageing and Throughput Analysis in a Single-Cell Deployment}},
school = {Linköping University},
type = {{LiTH-ISY-EX--14/4762--SE}},
year = {2014},
address = {Sweden},
}
@mastersthesis{diva2:726764,
author = {Sven, Ahlberg},
title = {{Evaluation of Different Radio-Based Indoor Positioning Methods}},
school = {Linköping University},
type = {{LiTH-ISY-EX--14/4760--SE}},
year = {2014},
address = {Sweden},
}
Trådlösa sensornätverk byggs upp av trådlösa sensorer, som gemensamt arbetar för att lösa en viss uppgift. Ett exempel på en sådan uppgift kan vara insamling av pollennivåer i luften över en stor yta. Sensornoderna vidarebefordrar datan sinsemellan tills den når en datainsamlingsnod någonstans i nätverket där den sedan lagras och efterbehandlas. Generellt gäller att sensornoder är små, billiga, kommunicerar trådlöst och har en väldigt lång livslängd. Traditionellt sett har sen- sornoder också antagits vara statiska (stillastående), vilket medför begränsningar om noderna bärs av exempelvis människor eller monteras på fordon.
I detta examensarbete presenteras matmac , ett mac-protokoll som designats för att hantera mobila noder i trådlösa sensornätverk. En referensimplementa- tion av matmac har implementerats i operativsystemet Contiki och utvärderats med varierande konfigurationsparametrar, rörelsehastigheter och dataintensitet i simulatorn Cooja. Resultatet från utvärderingen visar att mekanismerna för mo- bilitetshantering i matmac främjar sensornodernas förmåga att pålitligt överföra data trots att de är mobila.
@mastersthesis{diva2:719453,
author = {Östlund, Pierre},
title = {{Design, implementation och simulering av ett MAC-protokoll för mobila trådlösa sensornätverk}},
school = {Linköping University},
type = {{LiTH-ISY-EX--14/4757--SE}},
year = {2014},
address = {Sweden},
}
Cognitive radio is an autonomous transceiver that is continuously sensing theongoing communication in its environment, it then starts the communication whenever it is appropriate. Therefore, cognitive radio helps improving the spectrum utilization of the overall communication system. However, without suitable spectrum sensing techniques, cognitive radio would fail. Hence, in this thesis we investigate and implement various spectrum sensing algorithms via software defined radio for both single antenna and multiple antenna cases. The main communi-cation scheme that we are using is OFDM. Moreover, both computer simulations and real-world measurements, have also been done for comparison and analysis ofthe detector’s performance. The detectors we are using are based on correlationfunction of the received signal and generalized likelihood ratio test with its eigen-value. The results from the simulations and measurements are then representedas probability of missed detection curves for different signal to noise ratios. Ourresults show that the performance of the generalized likelihood ratio test baseddetectors are at least 2 dB better than the correlation based detector in our mea-surement. Moreover, our simulations show that they are able to outperform thecorrelation function detector by more than 6 dB. Although, generalized likelihoodratio test based detectors seem to be better than the correlation function baseddetector, it requires more computational power which may limit its practical use.
@mastersthesis{diva2:653113,
author = {Eamrurksiri, Techin},
title = {{Implementation and Analysis of Spectrum Sensing Algorithms for SIMO Links}},
school = {Linköping University},
type = {{LiTH-ISY-EX--13/4696--SE}},
year = {2013},
address = {Sweden},
}
Storskaliga fleranvändar-MIMO-system, med hundratals basstationsantenner, studeras med allt större intresse både inom akademin och industrin. En anledning är att sådana system kan betjäna flera enantennsanvändare samtidigt över samma tids-frekvens-resurs med fleranvändarförkodning. Det innebär högre datahastigheter och bättre spektral effektivitet. En annan anledning är att basstationens energiförbrukning förväntas avta linjärt med antalet antenner tack vare den ökade antennförstärkningen. För att möjliggöra den stora ökningen av antalet antenner, måste priset per antenn, med dess sändtagarkedja, vara lågt. Vore det möjligt att tillverka basstationsantenner av billiga, massproducerade mobiltelefonskomponenter, som effektförstärkare utan avancerad linearisering, då skulle storskalig fleranvändar-MIMO kunna bli verklighet.
Effektförstärkare i mobiltelefoner är generellt anpassade att ha hög verkningsgrad och har, i och med detta, kraftigt olinjära överföringsegenskaper. Det är fördelaktigt att sända signaler med lågt toppvärde genom sådana effektförstärkare, för att undvika svår distortion och för att maximera verkningsgraden genom att endast använda en liten avbackning från arbetspunkten. Konventionellt förkodade signaler har tyvärr högt toppvärde (ca. 10 dB). Detta arbete har undersökt en av Mohammed m.fl. (2013a) föreslagen förkodning för storskalig MIMO som resulterar i sändarsignaler med lågt toppvärde. Det visas att denna förkodning ger signaler med ett toppvärde på 4 dB, och att toppvärdet kan göras godtyckligt litet genom att dessutom begränsa fasvariationen. Ju mer fasen begränsas, desto lägre blir emellertid antennförstärkning. Till exempel om fasvariationen begränsas till π/2, sänks toppvärdet till 2,6 dB, men 2-3 dB högre sändareffekt behövs för att bibehålla samma prestanda eller, likvärdigt, så måste basstationen utrustas med 1,6-2,0 gånger fler antenner. Kontinuerlig fasmodulering som ett sätt att få sändarsignaler med konstant envelopp har studerats kort. Lågtoppvärdesförkodning, där sändarsignalerna ligger innanför en cirkel, föreslås som ett sätt att minska den erfodrade sändareffekten utan att öka toppvärdet märkvärt (<4,5 dB) relativt Mohammeds m.fl. förkodning. Förkodningsalgoritmen som utvecklades för detta fastnade dock i lokala minima, vilket försämrade dess prestanda. Sändareffekten kunde därför endast minskas lite grand (<1 dB) vid höga datahastigheter.
En preliminär länkbudget baserad på en enkel effektförstärkarmodell har visat att, med fullständig kanalkännedom och i frekvensplatt fädning, skulle lågtoppvärdesförkodning kunna minska energiförbrukningen med 33 % jämfört med konventionell, linjär förkodning i en basstation med 100 antenner. Analysen antyder att olineariserade klass AB mobiltelefonseffektförstärkare kan vara ett alternativ för storskalig fleranvändar-MIMO-basstationer.
@mastersthesis{diva2:633750,
author = {Moll\'{e}n, Christopher},
title = {{Low-PAR Precoding for Very-Large Multi-User MIMO Systems}},
school = {Linköping University},
type = {{LiTH-ISY-EX--13/4671--SE}},
year = {2013},
address = {Sweden},
}
Localization in wireless network sensors is an attractive research area nowadays. It is widely used in many applications e.g., indoor/outdoor asset tracking, intrusion detection, search-and-rescue, road traffic monitoring, and water quality monitoring. An accuracy and robustness to noise are important issues for localization which is needed to study and research to find the best solution. This thesis compares a ranging and localization techniques in indoor, urban and tunnel through a high performance ray-tracing simulator, Wireless InSiteR . Ranging techniques are based on two standard distance related measurement schemes e.g., RSS and TOA. A linearized least squares technique with reference node selection approach is chosen to estimate unknown nodes positions. Indoor and urban area are built-in floor plan and terrain available in simulator program, while tunnel is designed. In general, localization accuracy suffers from multipath and NLOS condition. This thesis also observes characteristic of them from ray-tracing method perspective. Firstly, important simulation parameters such as number ofreflections/diffractions, types of waveform, and types of antenna are analyzed oneach environments. Then, the models for distance estimation based on RSS and TOA measurements are created using measurements in simulated environments. The thesis proposes four scenarios for distance estimation model. They are line-of-sight (LOS), non-line-of-sight (NLOS), combination of LOS and NLOS, and NLOS with obstacle. All four scenarios models are derived along with model error distribution to observe characteristic of noise due to multipath and NLOS condition. Finally, the localization using only LOS condition measurements, is tested on each environment and compared results in term of accuracy.
@mastersthesis{diva2:632725,
author = {Chuasomboon, Sasit},
title = {{A comparison of ranging and localization techniques in indoor, urban, and tunnel environments}},
school = {Linköping University},
type = {{LiTH-ISY-EX--13/4695--SE}},
year = {2013},
address = {Sweden},
}
For most time-based positioning techniques, synchronization between the objectsin the system is of great importance. GPS (global positioning system) signalshave been found very useful in this area. However, there are some shortcomingsof these satellite signals, making the system vulnerable. The aim of this masterthesis is to investigate an alternative method for synchronization, independent ofGPS signals, which could be used as a complement. The proposed method takesadvantage of the broadcast signals from telecommunication towers, and use themfor calculation of the synchronization error between two receivers. By looking atthe time difference between arrival times at the receivers, and compare it to thetrue time difference, the synchronization error can be found. A precondition isthat the locations of the receivers as well as the tele tower are known beforehand,so that the true time difference can be calculated using geometry.The arrival times are determined through correlation between the received signalsand known training bits, which are a part of the transmission sequence. Forverification, experiments were made on localization of a mobile phone in theGSM (global system of mobile communications) network.This researchwas a collaboration with FOI, the Swedish Defense Research Agency,where most of the work was done.
@mastersthesis{diva2:631177,
author = {Nordzell, Andreas},
title = {{Double Differential TOA Positioning for GSM}},
school = {Linköping University},
type = {{LiTH-ISY-EX--13/4681--SE}},
year = {2013},
address = {Sweden},
}
The interest of Machine Type Communication (MTC) is increasing and is expected to play an important role in the future network society. In the process of increasing the number of connected devices, the coverage plays an important role. This thesis work aims to study the possibility of supporting coverage limited MTC-devices within LTE by extending the LTE coverage.
It shows that coverage increase by means of repetition is a good candidate, which allows for a significant increase without hardware upgrades at a low cost in terms of radio resources. For inter-site distances up to 2500 m, the proposed repetition scheme with an increase of 20 dB allows for almost complete coverage where today’s LTE have significant lack of coverage. It also shows that even though the increased coverage implies higher resource usage, the limitation is not in the number of users supported, but rather the coverage at longer inter-site distances.
@mastersthesis{diva2:631143,
author = {Berglund, Joel},
title = {{Extended LTE Coverage For Indoor Machine Type Communication}},
school = {Linköping University},
type = {{LiTH-ISY-EX--13/4683--SE}},
year = {2013},
address = {Sweden},
}
Nowadays, multiuser Multiple-In Multiple-Out systems (MU-MIMO) are used in a new generation wireless technologies. Due to that wireless technology improvement is ongoing, the numbers of users and applications increase rapidly. Then, wireless communications need the high data rate and link reliability at the same time. Therefore, MU-MIMO improvements have to consider 1) providing the high data rate and link reliability, 2) support all users in the same time and frequency resource, and 3) using low power consumption. In practice, the interuser interference has a strong impact when more users access to the wireless link. Complicated transmission techniques such as interference cancellation should be used to maintain a given desired quality of service. Due to these problems, MU-MIMO with very large antenna arrays (known as massive MIMO) are proposed. With a massive MU-MIMO system, we mean a hundred of antennas or more serving tens of users. The channel vectors are nearly orthogonal, and then the interuser interference is reduced significantly. Therefore, the users can be served with high data rate simultaneously. In this thesis, we focus on the performance of the massive MU-MIMO downlink where the base station uses linear precoding techniques to serve many users over Rayleigh and Nakagami-m fading channels.
@mastersthesis{diva2:630516,
author = {Pakdeejit, Eakkamol},
title = {{Linear Precoding Performance of Massive MU-MIMO downlink System}},
school = {Linköping University},
type = {{LiTH-ISY-EX--13/4705--SE}},
year = {2013},
address = {Sweden},
}
The purpose of this master thesis was to investigate how effiecient the extractionof radiofrequency quality metrics from digital video broadcast (DVB) streamscan become using software defined radio. Software defined radio (SDR) is a fairlynew technology that offers you the possibility of very flexible receivers and transmitters where it is possible to upgrade the modulation and demodulation overtime.
Agama is interested in SDR for use in the Agama Analyzer, a widely deployedmonitoring probe running on top of standard services. Using SDR, Agama coulduse that in all deployments, such as DVB by cable/terrestrial/satellite (DVBC/T/S), which would simplify logistics.
This thesis is an implementation of a SDR to be able to receive DVB-C. TheSDR must perform a number of adaptive algorithms in order to prevent the received symbols from being significantly different from the transmitted ones. Themain parts of the SDR include timing recovery, carrier recovery and equalization.Timing recovery performs synchronization between the transmitted and receivedsymbols and the carrier recovery performs synchronization between the carrierwave of the transmitter and the local oscillator in the receiver. The thesis discusses various methods to perform the different types of synchronizations andequalizations in order to find the most suitable methods.
@mastersthesis{diva2:630021,
author = {Eriksson, Viktor},
title = {{Extraction of radio frequency quality metric from digital video broadcast streams by cable using software defined radio}},
school = {Linköping University},
type = {{LiTH-ISY-EX--13/4676--SE}},
year = {2013},
address = {Sweden},
}
To allow faster and more reliable wireless communication a technique is to use multiple antennas in the transmitter and receiver. This technique is called MIMO. The usage of MIMO adds complexity to the receiver that must determine what the transmitter actually sent. This thesis focuses on hardware implementation suitable for an FPGA of a detection algorithm called SUMIS.
A background to detection and SUMIS in particular is given as a theoretical aid for a better understanding of how an algorithm like this can be implemented. An introduction to hardware and digital design is also presented.
A subset of the operations in the SUMIS algorithm such as matrix inversion and sum of logarithmic values are analyzed and suitable hardware architectures are presented. These operations are implemented in RTL hardware using VHDL targeted for an FPGA, Virtex-6 from Xilinx.
The accuracy of the implemented operations is investigated showing promising results alongside of a presentation of the necessary resource usage.
Finally other approaches to hardware implementation of detection algorithms are discussed and more suitable approaches for a future implementation of SUMIS are commented on. The key aspects are flexibility through software reprogrammability and area efficiency by designing a custom processor architecture.
@mastersthesis{diva2:626323,
author = {Frostensson, Tomas},
title = {{Hardware Implementation and Assessment of a Soft MIMO Detector Based On SUMIS}},
school = {Linköping University},
type = {{LiTH-ISY-EX--13/4664--SE}},
year = {2013},
address = {Sweden},
}
Localization of individual nodes in a wireless network is useful in many applications, e.g for tracking patients in hospitals. Using the Received Signal Strength Indicator, RSSI, for this purpose has been explored in numerous studies. It is energy efficient and rarely requires customised hardware of configuration. The possibility to use pre-configured, off-the-shelf products is especially important in large scale sensor network deployments. Using RSSI has, however, many drawbacks, since the radio signal is heavily affected by the surrounding envi- ronment. Most studies in this area discuss the impact of multipath effects. Our study on range based distance estimations, using the Telos hardware, shows that individual profiling requirements and antenna quality are equally challenging.
Still, RSSI based indoor localization systems remains an active field of research. A multitude of approaches and algorithms have been proposed to gain accuracy in position estimations. The most common of these techniques are explored in this report. Based on previous work at The Polytechnic University of Catalonia, the Telos hardware has been integrated successfully with existing software to form local wireless sensor networks for indoor localization. We present applications developed on top of TinyOS, an operating system for embedded systems. These applications serve as a platform for related future work at The Polytechnic University of Catalonia and elsewhere.
@mastersthesis{diva2:619303,
author = {Pehrson Skid\'{e}n, Petter},
title = {{Range Based Indoor Localization in Wireless Sensor Networks with Telos}},
school = {Linköping University},
type = {{LiTH-ISY-EX--13/4138--SE}},
year = {2013},
address = {Sweden},
}
OFDM is a fast growing technology in the area of wireless communication due to its numerous advantages and applications. The current and future technologies in the area of wireless communications like WiMAX, WiFi, LTE, MBWA and DVB-T uses the OFDM signals. The OFDM technology is applicable to the radio communication as well as the acoustic communication.
Though the licensed spectrum is intended to be used only by the spectrum owners, Cognitive radio is a concept of reusing this licensed spectrum in an unlicensed manner. Cognitive radio is motivated by the measurements of spectrum utilization . Cognitive radio must be able to detect very weak primary users signal and to keep the interference level at a maximum acceptable level. Hence spectrum sensing is an essential part of the cognitive radio. Spectrum is a scarce resource and spectrum sensing is the process of identifying the unused spectrum, without causing any harm to the existing primary user’s signal. The unused spectrum is referred to as spectrum hole or white space and this spectrum hole could be reused by the cognitive radio.
This thesis work focuses on implementing primary acoustic transmitter to transmit the OFDM signals from a computer through loudspeaker and receive the signals through a microphone. Then by applying different detection methods on the received OFDM signal for detection of the spectrum hole, the performance of these detection methods is compared here. The commonly used detection methods are power spectrum estimation, energy detection and second–order statistics (GLRT approach, Autocorrelation Function (ACF) detection and cyclostationary feature detection ). The detector based on GLRT approach exploits the structure of the OFDM signal by using the second order statistics of the received data. The thesis mainly focuses on GLRT approach and ACF detectors and compare their performance.
@mastersthesis{diva2:582746,
author = {Malkireddy, Sivakesava Reddy},
title = {{Spectrum Sensing of acoustic OFDM signals}},
school = {Linköping University},
type = {{LiTH-ISY-EX--12/4638--SE}},
year = {2012},
address = {Sweden},
}
The goal of this Master's thesis was to solve resource allocation problems in wireless networks through the implementation of a lightweight simulation platform. The spectrum and power resources of wireless networks have to be efficiently used to accommodate the growing number of wireless terminals and the massive increase of data transferred by their applications. The major problem that needs to be tackled is interference, which significantly limits the performance of wireless systems. In this thesis, the resource allocation of interest was the joint problem of scheduling and power control with Quality of Service (QoS) constraints. The Signal-to-Interference-plus-Noise Ratio (SINR) was used to quantify QoS. This thesis studied the recently proposed mixed-integer linear programming (MILP) formulation of the problem. Due to the scheduling component, the problem is inherently combinatorial and NP-hard, therefore computationally expensive and difficult to solve in tractable time. A simulation platform was implemented in order to automate and facilitate the solving process.As a starting point, wireless channels and channel modeling issues were studied. Then, the platform was implemented to simulate random instances of multi-cellular wireless networks, with several mobile stations per cell, and generate the corresponding channels. Finally, the platform was extended to use the GNU Linear Programming Kit (GLPK) API in order to optimally solve the aforementioned formulated problem for various inputs of generated channels.Tests of the simulation platform were performed to check the consistency of the results. Indeed, the output results satisfied the initial expectations regarding the SINR constraints and the formulation. Moreover, they were produced in reasonable time. An analysis of the output results was presented.This thesis resulted in a configurable and lightweight simulation platform which is able to solve the MILP-formulated resource allocation problem. The simulation platform is basic and does not cover all the aspects of multi-cellular wireless networks and wireless channels. Due to its modularity, it can be extended in a future project.
@mastersthesis{diva2:567538,
author = {Khosravi Dehkourdi, Tony},
title = {{Simulation Platform for Resource Allocation in Multi-Cellular Wireless Networks}},
school = {Linköping University},
type = {{LiTH-ISY-EX--12/4631--SE}},
year = {2012},
address = {Sweden},
}
Load control design is one of the major cornerstones of radio resource management in today's UMTS networks. A WCDMA cell's ability to utilize available spectrum efficiently, maintain system stability and deliver minimum quality of service (QoS) requirements to in-cell users builds on the algorithms employed to manage the load. Admission control (AC) and congestion control (CC) are the two foremost techniques used for regulating the load, and differing environments will place varying requirements on the AC and CC schemes to optimize the QoS for the entire radio network. This thesis studies a real-life situation where cells are put under strenuous conditions, investigates the degrading effects a high-speed train has on the cell's ability to maintain acceptable levels of QoS, and proposes methods for mitigating these effects.
The scenario is studied with regard to voice traffic where the limiting radio resource is downlink power. CC schemes that take levels of fairness into account between on-board train users and outdoor users are proposed and evaluated through simulation. Methods to anticipatorily adapt radio resource management (RRM) in a cell to prepare for a train is proposed and evaluated through simulation. A method to detect a high-speed train in a cell, and the users on it, is outlined and motivated but not simulated.
Simulation results are promising but not conclusive. The suggested CC schemes show a surprising tendency towards an increase in congestion avoidance performance. Proactive RRM shows a significant increase in QoS for on-board users. No negative effects to users in the macro environment is noticed, with regard to the studied metrics.
@mastersthesis{diva2:560891,
author = {Joshi, Raoul and Sundström, Per},
title = {{WCDMA Cell Load Control in a High-speed Train Scenario:
Development of Proactive Load Control Strategies}},
school = {Linköping University},
type = {{LiTH-ISY-EX--12/4614--SE}},
year = {2012},
address = {Sweden},
}
Indoor positioning is a rapidly growing research area, enabling new innovative location-aware applications and user-oriented services. Location Fingerprinting (LF) is the positioning technique of coupling a physical location with observed radio signal measurements. In the terms of indoor LF using Wireless Local Area Network (WLAN) it refers to the use of network measurements from the WLAN Access Points (APs) to tag known locations. A data set is created containing reference fingerprints for the area of interest and is known as a radio map. A radio map can later be used to find a user's location in the area of interest. WLAN infrastructures are vulnerable to many kinds of faults and malicious attacks, including, an attacker jamming the signal from an AP, or an AP becoming unavailable during positioning due to power outage. These faults can be collectively characterized as an AP-failure. In LF positioning systems, AP-failure faults can significantly degrade the performance of a LF system due to the difference between the current fingerprints and radio map created with all APs being available. It is desirable to detect such faulty APs, in order to take actions towards fault-mitigation and restoration, in case of a malicious attack. In this work, we have developed a fault detection algorithm that uses inertial sensors (i.e., accelerometer, magnetometer) available in smartphones to detect AP-failure faults in LF systems. Inertial Measurement Unit (IMU) has become an integral part of all high-end smartphones. IMU can be used to infer location information on the smartphone. The main idea is to have two parallel position streams, the LF positioning and the IMU positioning, and to compare the mean positioning error between the two. Since IMU positioning is fairly accurate once provided with starting coordinates, we use it to detect abnormal behaviour in LF positioning system, such as highly erroneous estimates signifying an AP-failure fault present in the system. The performance of the proposed detection algorithm is evaluated with several real-life AP-related faults. The proposed algorithm exhibits low probability of false alarms in the detection of faulty APs. The conclusion is that using IMU based positioning is an effective and robust solution in terms of fault detection in LF systems.
@mastersthesis{diva2:556698,
author = {Haider, Raja Umair},
title = {{Fault Detection in WLAN Location Fingerprinting Systems Using Smartphone Inertial Sensors}},
school = {Linköping University},
type = {{LiTH-ISY-EX--12/4601--SE}},
year = {2012},
address = {Sweden},
}
Inter-site interference distribution acts as a basic limitation on how much performance a network service provider can achieve in an urban network scenario. There are many different ways of controlling this interference levels. One such method is tuning the antenna downtilt depending on the network situation. Antenna downtilt can also be seen as a powerful tool for load balancing in the network.
This thesis work involves a study of the impact of the antenna downtilt in an urban environment, involving non-uniform user distribution. A realistic dual ray propagation model is used to model the path gain from the base station to a UE. Such a propagation model is used along with a directional antenna radiation pattern model to calculate the overall path gain from the base station to a UE. Under such modeling, the results of the simulations show that the antenna downtilt plays a crucial role in optimizing the network performance. The results show that the optimal antenna downtilt angle is not very sensitive to the location of the hotspot in the network. The results also show that the antenna downtilt sensitivity is very much dependent on the network scenario. The coupling between the antenna downtilt and the elevation half power beamwidth is also evaluated.
@mastersthesis{diva2:547010,
author = {Ramachandra, Pradeepa},
title = {{A Study on the Impact of Antenna Downtilt on theOutdoor Users in an Urban Environment}},
school = {Linköping University},
type = {{LiTH-ISY-EX--12/4585--SE}},
year = {2012},
address = {Sweden},
}
In a wireless network, the medium is a shared resource. The nodes in the network negotiate access of the shared resource using the Medium Access Control (MAC) protocol. The design of a MAC protocol for a sensor node is not the same as that for a wireless transceiver. Due to the transceiver characteristics, the MAC protocol design is limited in terms of medium access methods. However, in most cases, the protocols rely on simple access methods i.e. Time Division Multiple Access (TDMA) or Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA).
Control and monitoring applications, running over a wireless network, are typical examples of Wireless Sensor Actuator Network (WSAN) application in industries. In an industrial network, the message deliveries must be time-bounded otherwise, they are of no use.
This report aims to present the thesis work carried out at ABB AB, Västerås. The purpose of this thesis was to compare the performance of WLAN and WirelessHART when it comes to control applications. For the purpose of WLAN, the media access schemes are analyzed in terms of deadline misses. There are other metrices for the performance evaluation but our focus was on the latency, since it is very important in the field of industrial automation. NS-2 was used for the purpose of MAC layer analysis and it is also shown that PCF gives better performance as compared to DCF, in terms of deadline misses. Finally, WLAN is proven to accommodate more control loops as compared to WirelessHART for a given scenario.
@mastersthesis{diva2:540925,
author = {Nabi, Muaz Un},
title = {{Media Access Control for Wireless Sensor and Actuator Networks}},
school = {Linköping University},
type = {{LiTH-ISY-EX--12/4603--SE}},
year = {2012},
address = {Sweden},
}
In the LTE mobile system, all cells use the same set of frequencies. This means that a user could experience interference from other cells. A method that has been studied in order to reduce this interference and thereby increase data rate or system throughput is to coordinate scheduling between cells. Good results of this have been found in different studies. However, the interference is generally assumed to be known. Studies using estimated interference and simulating more than one cluster of cells have found almost no gain.
This thesis will focus on how to use information from coordinated scheduling and other traffic estimates to do better interference estimation and link adaption. The suggested method is to coordinate larger clusters and use the coordination information, as well as estimates of which cells will be transmitting, to make estimates of interference from other cells. The additional information from interference estimation is used in the link adaptation. Limitations in bandwidth of the backhaul needed to send data between cells are considered, as well as the delay it may introduce. A limitation of the scope is that MIMO or HetNet scenarios have not been simulated.
The suggested method for interference estimation and link adaptation have been implemented and simulated in a system simulator. The method gives a less biased estimate of SINR, but there are no gains in user bit rate. The lesser bias is since the method is better at predicting high SINR than the base estimate is. The lack of gains regarding user bit rate may result from the fact that in the studied scenarios, users where not able to make use of the higher estimated SINR since the base estimate is already high.
The conclusion is that the method might be useful in scenarios where there are not full load, but the users either have bad channel quality or are able to make use of very high SINR. Such scenarios could be HetNet or MIMO scenarios, respectively.
@mastersthesis{diva2:535791,
author = {Örn, Sara},
title = {{Realistic Multi-Cell Interference Coordination in 4G/LTE}},
school = {Linköping University},
type = {{LiTH-ISY-EX--12/4586--SE}},
year = {2012},
address = {Sweden},
}
Electrical wiring on board aircraft has raised serious weight and safety concerns in the aerospace industry. Wires are antenna. It may also cause interference to radio-based systems on the aircraft, or, in the case of military aircraft, create a "signature" that can be detected by enemy receivers. Wireless application in avionic system helps reducing the total weight and reconfigurable of the aircraft; hence, lower the fuel costs, installation cost and maintenance costs, as well as the “signature” of the aircraft. The focus of this thesis, therefore, is to study the feasibility of different wireless standards, namely Wi-Fi, Bluetooth and ultra-wide band (UWB), on replacing the wired data connection in the EW countermeasure or chaff/flare dispenser systems.
The study was constructed under the supervision of the department of Electronic Defense System, Saab AB in Järfalla, Stockholm. The discussion will be based on the resource availability, the reliability, the stability and the security of the wireless system relative to an avionic application; i.e., whether wireless links will negatively affect the overall reliability and safety of the aircrafts. Due to the theoretical studies and results from the simulation, we studied the feasibility issue and concluded that UWB is the most appropriate choice of wireless communication for non-critical aerospace applications, comparing with Wi-Fi and Bluetooth. UWB links can have reasonable immunity to interferences, low interference to other on-board wireless systems, and good security performance.
@mastersthesis{diva2:516683,
author = {Pinsuvan, Sukanya and Pinitchun, Rawin},
title = {{Feasibility Study for Wireless Control on The Countermeasure Dispenser System}},
school = {Linköping University},
type = {{LiTH-ISY-EX--12/4544--SE}},
year = {2012},
address = {Sweden},
}
When a radio signal traverses the atmosphere it will be delayed by not only thedistance between transmitter and receiver, but also the atmosphere. Given knowl-edge of the characteristics of the sent signal the effect of the atmosphere can beobtained from the received signal. This concept is called radio occultation. Radiooccultation can provide high accuracy profiles of temperature, pressure and watervapour troughout the atmosphere.This report aims to present the work and results from a thesis performed atRUAG Space in Göteborg. The purpose of the thesis was to implement a simulatorwhich with high accuracy could generate a signal as it would have been receivedhad it propagated through the atmosphere.We will show that the generated signal passes the requirements that have beenset.
@mastersthesis{diva2:506639,
author = {Rönnberg Sjödin, Oskar and Ahlsin, David},
title = {{Development of Simulation Tool and New Tracking Algorithms for Radio Occultation Receivers}},
school = {Linköping University},
type = {{LiTH-ISY-EX--11/4473--SE}},
year = {2011},
address = {Sweden},
}
A Tactical Data Link (TDL) system has been deployed in many military missions as a winning strategy. The performance of a TDL system is governed by the MAC protocol. The MAC protocol that is able to provide more flexibility and high quality of services is more desirable. However, most MAC protocols implemented in current TDL systems are based on a preprogramming TDMA protocol, in which a time slot schedule is fixed. This thesis presents the new self-organized TDMA protocol based on the existing self-organized slot assignment algorithms and the practical military scenarios as the alternative solution to the current preprogramming TDMA protocol. The self-organized TDMA protocol presented in this thesis is based on the Node Activation Polling Access (NAPA), Virtual Slot (VSLOT), and message based slot assignment algorithms. To evaluate the performance of the designed self-organized TDMA protocol over the preprogramming TDMA protocol, the simulation models for both protocols were implemented and simulated with NS-2 under the specific study scenarios. The results show that the self-organized TDMA protocol offers more flexibility and higher performance than the preprogramming TDMA protocol. In addition, the aspects of stability and security for the self-organized TDMA protocol were discussed. The overall conclusion is that the self-organized TDMA protocol could be a viable alternative for a future TDL system.
@mastersthesis{diva2:459572,
author = {Pawgasame, Wichai and Sa-Ad, Wuttisak},
title = {{Self-Organized TDMA protocol for Tactical Data Links}},
school = {Linköping University},
type = {{LiTH-ISY-EX--11/4527--SE}},
year = {2011},
address = {Sweden},
}
The cellular networks are evolving to meet the future requirements of data rate,coverage and capacity. The fourth generation mobile communication system, LTEhas been developed to meet these goals. LTE uses multiple antenna features andlarger bandwidths in order to accomplish this task. These features will furtherextend the requirements of data rate, coverage, latency and flexibility.
LTE also utilizes the varying quality of the radio channel and the interferencefrom other transmitters by adapting the data rate to the instantaneous channelquality at all the time. This is typically referred to as Link Adaptation. Thelink adaptation fails from time to time due to the varying channel quality as wellas the interference from other transmitters. In order to counteract these failures,retransmission methods are employed. These methods detect the errors on thereceiver side and signals the transmitter for the retransmission of the erroneousdata. The efficiency of link adaptation increases if combined with a properly designedretransmission scheme at the expense of delays due to retransmissions.
This master thesis focuses on the study of the retransmission schemes with fasterfeedback, resulting in a reduction in delay. The feedback is generated by makingan early estimate of the decoding outcome and sending it early to the transmitterresulting in faster retransmission. This is important in certain applications wherethe data transmission is intolerant to delays.The thesis work shows by system performance simulations that fast packet retransmission,precisely called Early HARQ Feedback, significantly affects the systemperformance together with the utilization of the link adaptation. The study alsoshows that the link adaptation, in certain scenarios, can be optimized to improvethe system performance. In that respect, it is also possible to increase the numberof retransmissions within the same resource utilization. That optimization is basicallycalled aggressive link adaptation. Consequently, Early HARQ Feedback incombination with aggressive link adaptation provides a large improvement in thedownlink performance of the studied cases.
@mastersthesis{diva2:457862,
author = {Tamoor-ul-Hassan, Syed and Demir, Serkan},
title = {{Fast Packet Retransmissions in LTE}},
school = {Linköping University},
type = {{LiTH-ISY-EX--11/4529-SE}},
year = {2011},
address = {Sweden},
}
One technique that is used to reduce the errors brought upon signals, when transmitted over noisy channels, is error control coding. One type of such coding, which has a good performance, is turbo coding. In some of the TMS320C64xTM digital signal processors there is a built in coprocessor that performs turbo decoding.
This thesis is performed on the account of Communication Developments, within Saab AB and presents an evaluation of this coprocessor. The evaluation deals with both the memory consumption as well as the data rate. The result is also compared to an implementation of turbo coding that does not use the coprocessor.
@mastersthesis{diva2:451918,
author = {Ahlqvist, Johan},
title = {{Evaluation of the Turbo-decoder Coprocessor on a TMS320C64x Digital Signal Processor}},
school = {Linköping University},
type = {{LiTH-ISY-EX--11/4522--SE}},
year = {2011},
address = {Sweden},
}
The OFDM technology has been extensively used in many radio communicationtechnologies. For example, OFDM is the core technology applied in WiFi, WiMAXand LTE. Its main advantages include high bandwidth utilization, strong noise im-munity and the capability to resist frequency selective fading. However, OFDMtechnology is not only applied in the field of radio communication, but has alsobeen developed greatly in acoustic communication, namely the so called acousticOFDM. Thanks to the acoustic OFDM technology, the information can be em-bedded in audio and then transmitted so that the receiver can obtain the requiredinformation through certain demodulation mechanisms without severely affectingthe audio quality.This thesis mainly discusses how to embed and transmit information in audioby making use of acoustic OFDM. Based on the theoretical systematic structure, italso designs a simulation system and a measurement system respectively. In thesetwo systems, channel coding, manners of modulation and demodulation, timingsynchronization and parameters of the functional components are configured in themost reasonable way in order to achieve relatively strong stability and robustnessof the system. Moreover, power control and the compatibility between audio andOFDM signals are also explained and analyzed in this thesis.Based on the experimental results, the author analyzes the performance of thesystem and the factors that affect the performance of the system, such as the typeof audio, distance between transmitter and receiver, audio output level and so on.According to this analysis, it is proved that the simulation system can work steadilyin any audio of wav format and transmit information correctly. However, dueto the hardware limitations of the receiver and sender devices, the measurementsystem is unstable to a certain degree. Finally, this thesis draws conclusions of theresearch results and points out unsolved problems in the experiments. Eventually,some expectations for this research orientation are stated and relevant suggestionsare proposed.
@mastersthesis{diva2:448449,
author = {Wang, Shuai},
title = {{Embedding data in an audio signal, using acoustic OFDM}},
school = {Linköping University},
type = {{LiTH-ISY-EX--11/4518--SE}},
year = {2011},
address = {Sweden},
}
The CPR3 is a handheld radar device. This device is capable of detecting movement through walls and is mainly intended for police and military use. It is equipped with a Bluetooth module that enables remote control. To enhance the mobility of the users that utilize this functionality, a Windows Mobile application is developed. This application is meant to replace the already existing Windows application used for remotely controlling these radar devices. Furthermore, a small evaluation of the framework used for the development of the application is performed.
Also, a theoretical performance analysis is performed on the ZigBee standard. The goal is to find out whether or not ZigBee is a suitable replacement technology for Bluetooth as the primary means of communication within the system.
@mastersthesis{diva2:439145,
author = {Wichers, Ragnar},
title = {{A GUI Application for Controlling Handheld Radar Devices via Bluetooth and a Suitability Study of ZigBee}},
school = {Linköping University},
type = {{LiTH-ISY-EX--11/4384--SE}},
year = {2011},
address = {Sweden},
}
Server Based Computing (SBC) technology allows applications to be deployed, managed, supported and executed on the server and not on the client; only the screen information is transmitted between the server and client. This architecture solves many fundamental problems with application deployment, technical support, data storage, hardware and software upgrades.
This thesis is targeted at upgrading and evaluating performance of thin clients in scientific Server Based Computing (SBC). Performance of Linux based SBC was assessed via methods of both quantitative and qualitative research. Quantitative method used benchmarks that measured typical-load performance with SAR and graphics performance with X11perf, Xbench and SPECviewperf. Structured interview, a qualitative research method, was adopted in which the number of open-ended questions in specific order was presented to users in order to estimate user-perceived performance.
The first performance bottleneck identified was the CPU speed. The second performance bottleneck, with respect to graphics intensive applications, includes the network latency of the X11 protocol and the subsequent performance of old thin clients. An upgrade of both the computational server and thin clients was suggested.
The evaluation after the upgrade involved performance analysis via quantitative and qualitative methods. The results showed that the new configuration had improved the performance.
@mastersthesis{diva2:400152,
author = {Azhar, Rizwan},
title = {{Upgrading and Performance Analysis of Thin Clients in Server Based Scientific Computing}},
school = {Linköping University},
type = {{LiTH-ISY-EX--11/4388--SE}},
year = {2011},
address = {Sweden},
}
Long Term Evolution (LTE) is becoming the first choice of operators when constructingthe new network infrastructure, because of its high throughput and lowlatency. Although the LTE can offer high speed data service as a benefit of widebandapplication, the large bandwidth also results in huge control signaling cost.This thesis studies how the available radio resources should be allocated todifferent users for the particular purpose. Three proposals are presented in thisthesis. The first two aim at maximizing the overall net capacity. The factors ofchannel conditions and control signaling cost are considered in the first proposalwhereas power control is supplemented as an additional factor in the second one.The third proposal aims at achieving a tradeoff between subframe efficiency andaverage data rate. Channel conditions and control signaling cost are taken intoconsideration.Resource blocks scheduling under a control signaling cost constraint is feasiblewith the knowledge of the channel condition of users. This is obtained from channelstate information directly. The first proposal studies how this scheduling isdone. The second proposal takes power allocation scheme into account. In termsof computational complexity, the methods of internal water-filling and externalwater-filling are described in the second proposal. The simulation results illustratethat the net capacity in the first proposal can be enhanced by about 5% -60% in the second proposal. The exact percentage of increase depends on differentcontrol signaling penalty.The third proposal discusses how to implement flexible subframe length underthe Rayleigh fading channel condition in the LTE system. The objective is toachieve subframe efficiency as high as possible, while maintaining the maximumaverage data rate. The simulation results illustrate that the optimal subframelength depends on control signaling cost penalty as well as on Doppler frequency.Finally, the fairness of the first proposal is compared with the improved versionsof Round Robin, Dynamic Allocation and Proportional Fair scheduling algorithms.The simulation results show that Round Robin and Dynamic Allocationoutperform the first proposal under a certain condition.
@mastersthesis{diva2:393400,
author = {Tang, Zhiqiang},
title = {{Traffic Scheduling for LTE Advanced}},
school = {Linköping University},
type = {{LiTH-ISY-EX--10/4413--SE}},
year = {2010},
address = {Sweden},
}
The new mobile standard Long Term Evolution delivers high data rates, small delay and a more efficiently utilized RF spectrum. A solution to maintain this performance in user dense areas or areas with bad reception is the deployment of so-called femtocells. Femtocells are small base stations that are deployed indoors and share the RF spectrum with the whole mobile network. The idea is that femtocells will increase mobile operators network coverage and capacity while it at the same time increase users data throughput. There are several challenges with femtocells, both technical and economical ones. The most debated issues is how femtocells should schedule users while operating in an environment where other femtocells and base stations are interfering. In this work we developed a simulation tool to simulate the scheduling interaction between femtocells and base stationsin order to show the performance of radio resource schedulers. This rapport also aims to evaluate an approach to a femtocell scheduler to solve this issue in a satisfying way. The report gives a description of the structure of the implemented simulation tool together with some reflections on how future designs of similar or more complex simulation environments could be done.
@mastersthesis{diva2:352930,
author = {Roberg, Kristoffer},
title = {{Simulation of scheduling algorithms for femtocells in an LTE environment}},
school = {Linköping University},
type = {{LiTH-ISY-EX--10/4396--SE}},
year = {2010},
address = {Sweden},
}
For a long time radio devices have been constructed in hardware with a fixed functionality. This way of constructing radio devices is starting to change with the concept of Software Defined Radio (SDR) evolving. The SDR concept leads to more flexible and long lasting radio devices. In order to make the radio software more standardized and portable, the U.S. military has defined the Software Communication Architecture (SCA). Internal communication within the SCA is done by CORBA, which limit waveforms to be only distributed over CORBA-capable hardware. The U.S. military has defined the Modem Hardware Abstraction Layer(MHAL) to enable distribution over devices not supporting CORBA. This thesis presents an implementation of MHAL and an underlying transport mechanism based on Ethernet. The implementation is done for the OSSIE package. The implementation is evaluated both in terms of real-time and throughput performance. The results show that MHAL achieves good performance, in comparison to CORBA, and can greatly be used to distribute waveforms over both CORBA and non-CORBA capable devices.
@mastersthesis{diva2:348232,
author = {Dackenberg, Jens},
title = {{Software Communication Architecture - Waveform Distribution with MHAL}},
school = {Linköping University},
type = {{LiTH-ISY-EX--10/4363--SE}},
year = {2010},
address = {Sweden},
}
In this thesis we investigate different algorithms for dynamic resource allocation in wireless networks. We introduce a general framework for modeling systems whichis applicable to many scenarios. We also analyze a specific scenario with adaptivebeamforming and show how it fits into the proposed framework. We then studytwo different resource allocation problems: Quality-of-Service (QoS) constraineduser scheduling and sum-rate maximization. For user scheduling, we select some“good” set of users that is allowed to use a specific resource. We investigatedifferent algorithms with varying complexities. For the sum-rate maximizationwe find the global optimum through an algorithm that takes advantage of thestructure of the problem by reformulating it as a D.C. program, i.e., a minimizationover a difference of convex functions. We validate this approach by showing that itis more efficient than an exhaustive search at exploring the space of solutions. Thealgorithm provides a good benchmark for more suboptimal algorithms to comparewith. The framework in which we construct the algorithm, apart from being verygeneral, is also very flexible and can be used to implement other low complexitybut suboptimal algorithms.
@mastersthesis{diva2:326290,
author = {Eriksson, Kristoffer},
title = {{Dynamic Resource Allocation in Wireless Networks}},
school = {Linköping University},
type = {{LiTH-ISY-EX--10/4345--SE}},
year = {2010},
address = {Sweden},
}
New high quality mobile telecommunication services are offered everyday and the demand for higher data rates is continuously increasing. To maximize the uplink throughput in HSPA when transmission is propagated through a dispersive channel causing self-interference, equalizers are used. One interesting solution, where the equalizer and decoder exchange information in an iterative way, for improving the equalizer performance is Turbo equalization.
In this thesis a literature survey has been performed on Turbo equalization methods and a chosen method has been implemented for the uplink HSPA standard to evaluate the performance in heavily dispersive channels. The selected algorithm has been adapted for multiple receiving antennas, oversampled processing and HARQ retransmissions. The results derived from the computer based link simulations show that the implemented algorithm provide a gain of approximately 0.5 dB when performing up to 7 Turbo equalization iterations. Gains up to 1 dB have been obtained by disabling power control, not using retransmission combining and utilizing a single receiver antenna. The algorithm has also been evaluated considering alternative dispersive channels, Log-MAP decoding, different code rates, number of Turbo equalization iterations and number of Turbo decoding iterations.
The simulation results do not motivate a real implementation of the chosen algorithm considering the increased computational complexity and small gain achieved in a full featured receiver system. Further studies are needed before concluding the HSPA uplink Turbo equalization approach.
@mastersthesis{diva2:321458,
author = {Konuskan, Cagatay},
title = {{Turbo Equalization for HSPA}},
school = {Linköping University},
type = {{LiTH-ISY-EX- -10/4301- - SE}},
year = {2010},
address = {Sweden},
}
Communication over today’s IP-based networks are to some extent subject to packet loss. Most real-time applications, such as video streaming, need methods to hide this effect, since resending lost packets may introduce unacceptable delays. For IP-based video streaming applications such a method is referred to as a packet loss concealment scheme.
In this thesis a recently proposed mixture model and least squares-based packet loss concealment scheme is implemented and evaluated together with three more well known concealment methods. The JM reference software is used as basis for the implementation, which is a public available software codec for the H.264 video coding standard. The evaluation is carried out by comparing the schemes in terms of objective measurements, subjective observations and a study with human observers.
The recently proposed packet loss concealment scheme shows good performance with respect to the objective measures, and careful observations indicate better concealment of scenes with fast motion and rapidly changing video content. The study with human observers verifies the results for the case when a more sophisticated packetization technique is used.
A new packet loss concealment scheme, based on joint modeling of motion vectors and pixels, is also investigated in the last chapter as an additional contribution of the thesis.
@mastersthesis{diva2:311618,
author = {Cooke, Henrik},
title = {{Implementation and evaluation of packet loss concealment schemes with the JM reference software}},
school = {Linköping University},
type = {{LiTH-ISY-EX - -10/4339 - -SE}},
year = {2010},
address = {Sweden},
}
VDL mode 4 is a digital data link operating in the VHF band, its mainly use is for the aviation industry.VDL4 can as an example provide with positioning data, speed information of aircrafts or vehicles equipped with a VDL4 transponder. A connection between the groundsystem and the airborne system is called a point to point connection, which can be used for various applications. This data link needs to be transferred between groundstations during flights in order maintain the connection, which is called handoff.
The handoff process needs to be quick enough to not drop the link and at the same time a low rate of handoffs is desirable. The data link is regarded as a narrow resource and link management data for handoff is considered as overhead.
This thesis studies how to make the handoff procedure optimal with respect to involved aspects. Previous research of handoff algorithms and models of the VHF-channel are treated. Standardized parameters and procedures in VDL4 and are explored in order to find an optimal solution for the handoff procedure in VDL4.
The studied topics are analyzed and it is concluded to suggest an algorithm based on an adaptive hysteresis including signal quality and positioning data provided in VDL4. Standardized parameters which could be useful in the handoff procedure are commented, since the VDL4 standards are under development.
@mastersthesis{diva2:310985,
author = {Andersson, Rickard},
title = {{Algorithm for Handoff in VDL mode 4}},
school = {Linköping University},
type = {{LiTH-ISY-EX--10/4332--SE}},
year = {2010},
address = {Sweden},
}
The wide spread use of IEEE Wireless LAN 802.11 in battery operated mobile devices introduced the need of power consumption optimization while meeting Quality-of-Service (QoS) requirements of applications connected through the wireless network. The IEEE 802.11 standard specifies a baseline power saving mechanism, hereafter referred to as standard Power Save Mode (PSM), and the IEEE 802.11e standard specifies the Automatic Power Save Delivery (APSD) enhancement which provides support for real-time applications with QoS requirements. The latest amendment to the WLAN 802.11 standard is the IEEE 802.11n standard which enables the use of much higher data rates by including enhancements in the Physical and MAC Layer. In this thesis, different 802.11n MAC power saving and QoS optimization possibilities are analyzed comparing against existing power saving mechanisms.
Initially, the performance of the existing power saving mechanisms PSM and Unscheduled-APSD (UAPSD) are evaluated using the 802.11n process model in the OPNET simulator and the impact of frame aggregation feature introduced in the MAC layer of 802.11n was analyzed on these power saving mechanisms. From the performance analysis it can be concluded that the frame aggregation will be efficient under congested network conditions. When the network congestion level increases, the signaling load in UAPSD saturates the channel capacity and hence results in poor performance compared to PSM. Since PSM cannot guarantee the minimum QoS requirements for delay sensitive applications, a better mechanism for performance enhancement of UAPSD under dynamic network conditions is proposed.
The functionality and performance of the proposed algorithm is evaluated under different network conditions and using different contention settings. From the performance results it can be concluded that, by using the proposed algorithm the congestion level in the network is reduced dynamically thereby providing a better power saving and QoS by utilizing the frame aggregation feature efficiently.
@mastersthesis{diva2:309897,
author = {Gomony, Manil Dev},
title = {{An adaptive solution for power efficiency and QoS optimization in WLAN 802.11n}},
school = {Linköping University},
type = {{LiTH-ISY-EX--10/4276--SE}},
year = {2010},
address = {Sweden},
}
The use of relays is seen as a promising way to extend cell coverage and increase rates in LTE Advanced networks. Instead of increasing the number of base stations (BS), relays with lower cost could provide similar gains. A relay will have a wireless link to the closest BS as only connection to the core network and will cover areas close to the cell edge or other areas with limited rates.
Performing transmissions in several hops (BS-relay & relay-user) requires more radio resources than using direct transmission. This thesis studies how the available radio resources should be allocated between relays and users in order to maximize throughput and/or fairness. Time and frequency multiplexed backhaul is investigated under a full buffer traffic assumption. It is shown that the system will be backhaul limited and that the two ways of multiplexing will perform equally when maximising throughput and/or fairness. The analysis results in a set of throughput/fairness suboptimal solutions, dependant on how many relays are used per cell. The results are verified by simulations, which also show the limiting effects on throughput caused by interference between relays.
It is also analysed how the resource allocation should be done given non-fullbuffer traffic. A resource allocation that minimises packet delay given a certain number of relays per cell is presented. The analysis is based on queuing theory.
Finally some different schedulers and their suitability for relay networks are discussed. Simulation results are shown, comparing the throughput and fairness of Round Robin, Weighted Round Robin, Proportional Fairness and Weighted Proportional Fairness schemes. It is shown that allocating the resource among the relays according to the number of users served by the relays improves the fairness.
@mastersthesis{diva2:305955,
author = {Roth, Stefan},
title = {{Frame Allocation and Scheduling for Relay Networks in the LTE Advanced Standard}},
school = {Linköping University},
type = {{LiTH-ISY-EX--10/4327--SE}},
year = {2010},
address = {Sweden},
}
The GSM network technology has been developed and improved during several years which have led to an increased complexity. The complexity results in more network parameters and together with different scenarios and situations they form a complex set of configurations. The definition of the network parameters is generally a manual process using static values during test execution. This practice can be costly, difficult and laborious and as the network complexity continues to increase, this problem will continue to grow.This thesis presents an implementation of an automated performance optimization algorithm that utilizes genetic algorithms for optimizing the network parameters. The implementation has been used for proving that the concept of automated optimization is working and most of the work has been carried out in order to use it in practice. The implementation has been applied to the Link Quality Control algorithm and the Improved ACK/NACK feature, which is an apart of GSM EDGE Evolution.
@mastersthesis{diva2:299931,
author = {Gustavsson, Jonas},
title = {{Automated Performance Optimization of GSM/EDGE Network Parameters}},
school = {Linköping University},
type = {{LiTH-ISY-EX--09/4310--SE}},
year = {2009},
address = {Sweden},
}
In wireless transmissions the communication is often degraded by random fades, noise and other performance reducing phenomena. One way of improving the stability and reducing the error rates is to use relaying techniques where several nodes cooperate in a transmission between two of them. This thesis analyzes some of the available Decode-and-Forward relaying schemes for wireless transmission. The investigated schemes are conventional repetition coding, partial repetition coding and non-collaborative direct transmission. I have developed a three-node communication system using an audio channel to test the performance of repetition coding and direct transmission. This audio communication system can also be used to demonstrate some basic phenomena in wireless transmissions and how different scenarios change the performance of the communication. A theoretical performance analysis and computer simulations of the schemes performance over a Rayleigh fading channel are done as a basis for comparison. As a result we see that in the audio communication system repetition coding actually degrades the performance, compared to direct transmission, when using a relatively slow data rate in comparison to the speed of the fading in the audio channel.
@mastersthesis{diva2:228951,
author = {Wärme, Thomas},
title = {{Performance of Cooperative Relay Protocols over an Audio Channel}},
school = {Linköping University},
type = {{LiTH-ISY-EX- -09/4267 - - SE}},
year = {2009},
address = {Sweden},
}
This thesis examines the possibility of installing a wireless communication system based on multiple antennas, on an Unmanned Aerial Vehicle (UAV). The communication system is based on MIMO technology. This technology uses the fact that we can make use of several antennas at the transmitter and the receiver to create independent signal path which in turn can increase the roboustness of the communication link. Advantages and disadvantages of this new system arediscussed. However, this report concludes that the benefits of MIMO outweights the disadvantages.
Furthermore a simulation environment for the MIMO system is designed and implemented, based on a specific scenario. Moreover, the results from the simulation also points to a benefit of the MIMO technology.
@mastersthesis{diva2:201911,
author = {Zamanzadeh, Amin},
title = {{MIMO system for Skeldar UAV System}},
school = {Linköping University},
type = {{LiTH-ISY-EX--09/4213--SE}},
year = {2009},
address = {Sweden},
}
In todays GSM network more and more interfaces are run over IP instead of classic synchronized networks. This rises new issues to be solved, for example handling of jitter that use of IP networks introduces. The jitter can be handled by a jitter buffer which ensures that the packets are forwarded in evenly spaced intervals.
In GSM, data is requested a certain time in advance before delivery to a cellphone. This "time in advance" needs to be adjusted according to the delay of the channel. For an IP network this delay varies (jitter), which means that it would be beneficial to have an algorithm which continuously adjusts how long in advance the packets should be requested. The adjustment is made according to current channel delay and jitter size.
In this thesis work a model of a general IP network has been developed and isthen used for development of two algorithms for jitter buffer handling. Once the algorithms have been developed they are evaluated and compared to each other and previous solutions to the problem. One of the algorithms is new and the other is an already existing algorithm that has been extended.
The simplified conclusion is that the behaviors of both algorithms are very similar. They mainly have small packet loss but sometimes the packets are requested earlier than needed and therefore are kept in the buffer a bit longer than necessary. When comparing the two developed algorithms with previous solutions it is visible that they improve the buffer handling a great deal.
@mastersthesis{diva2:207810,
author = {Ferm, Gabriella and Jarledal, Jonas},
title = {{Abis over IP Modelling and Characteristics}},
school = {Linköping University},
type = {{LITH-ISY-EX--09/4238--SE}},
year = {2009},
address = {Sweden},
}
GSM has been developed during more than a decade and has grown to a very complex system. Due to the wide range of functionality, the high capacity and the complexity of the BSC the testing of stability and performance is time consuming. A simulator is needed for these tests as live networks are not available at this stage in the development process. The performance and stability need to be verified for each new release of functionality.
This thesis describes a conceptual model of a GSM network. The conceptual model can be used to configure a simulated radio network and to communicate what is simulated on a conceptual level rather than a detailed level.
The model presented consists of several sub models. The subscriber model describes the actions and movement of subscribers; the cell model describes the radio conditions experienced by a subscriber moving within one cell; and the cell network model describes the geographical and structural properties of the network.
Together the models are used to compose scenarios with the aim to describe varying radio conditions, varying subscriber behavior and varying cell structures. The aim is that different features of the Ericsson base station controller shall be used in the different scenarios. The scenarios represent different parts of a radio network connected to the same base station controller.
@mastersthesis{diva2:557849,
author = {Grundberg, Staffan},
title = {{Radio Netwok Test Configuration for Maximum Test Coverage:
Model based load generation in system verification of a GSM Base Station Controller}},
school = {Linköping University},
type = {{LIU-ISY-A--07/4037--SE}},
year = {2008},
address = {Sweden},
}
This report treats detection in IR-pictures taken from airplanes over the ground. The detection is divided in two parts. First there is a detection with filterkernels with the task to point on targets and objects that look like targets. The second part is a discriminator that demands more calculations and has the task to sort out the false alarms from the discriminator. Both the detector and the discriminator contain thresholds thats been trained from trainingsets of data. The results from the detector was better then expected hence it wasn’t possible to test the diskriminator properly.
@mastersthesis{diva2:127064,
author = {Aronsson, Peter},
title = {{Objektdetektering i SAR- och IR-bilder}},
school = {Linköping University},
type = {{LITH-ISY-EX--08/4070--SE}},
year = {2008},
address = {Sweden},
}
The main goal in this thesis is to select and test Forward Error Correction (FEC) schemes suitable for network video transmission over RTP/UDP. There is a general concern in communication networks which is to achieve a tradeoff between reliable transmission and the delay that it takes. Our purpose is to look for techniques that improve the reliability while the realtime delay constraints are fulfilled. In order to achieve it, the FEC techniques focus on recovering the packet losses that come up along any transmission. The FEC schemes that we have selected are Parity Check algorithm, ReedSolomon (RS) codes and a Convolutional code. Simulations are performed to test the different schemes.
The results obtained show that the RS codes are the more powerful schemes in terms of recovery capabilities. However they can not be deployed for every configuration since they go beyond the delay threshold. On the other hand, despite of the Parity Check codes being the less efficient in terms of error recovery, they show a reasonable low delay. Therefore, depending on the packet loss probability that we are working with, we may chose one or other of the different schemes. To summarize, this thesis includes a theoretical background, a thorough analysis of the FEC schemes chosen, simulation results, conclusions and proposed future work.
@mastersthesis{diva2:17539,
author = {Valverde Martínez, David and Parada Otte, Francisco Javier},
title = {{Forward Error Correction for Packet Switched Networks}},
school = {Linköping University},
type = {{LiTH-ISY-EX--08/4036-SE}},
year = {2008},
address = {Sweden},
}
Other links
- Master thesis projects performed at the previous chair in Data Transmission during 1992-2001 can be found here.
Page responsible:
Danyo Danev
Last updated: 2019 07 29 15:48