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TSKS04 Digital Communication Continuation Course

Laboratory Exercises

Lab Memo

Lab-groups

You sign up for the labs in groups of three students (some group might be four students if necessary). We will discuss the laboratory exercises in detail at Tutorial 2 and also decide on the members of each group.

Introduction to Simulink

Simulink is a part of Matlab. If you have not used Simulink before, you will learn it during the laboratory exercises. You can also go through the introduction part of the Lab Memo to the course TSKS02 Telecommunication. You will not need any advanced Simulink skills. You will get a pre-made communication system and your task is only to modify it so that it satisfies certain demands.

Task

The lab task is the following: You get a partly unknown channel, and your task is to construct a communication system that communicates over that channel.

Information about the channel
  • It is saturated. Apart from that, it is linear.
  • It is time-invariant.
  • It is bandlimited, but not ideally.
  • It adds white Gaussian noise.
  • It takes a time-discrete input, and the sampling frequency has to be 100 kHz. If not, you will be flooded with error messages.
Demands on the System

Your communication system must fulfill the following demands:

  • The system must be non-trivial, in the sense that it is not simply a modulator-channel-demodulator system.
  • The bit-error rate must not exceed 0.5% when communicating independent equally probable bits.
  • You should strive to maximize the data rate. 250 bit/s should not be impossible.
Examination

Demands to pass the laboratory exercises:

  • Your system fulfills the demands above.
  • Your lab report (one per group) is handed in no later than 2016-03-08 together with a Simulink model of your system that demonstrates that the bit error rate demand is fulfilled.
  • Your lab report is written in English and includes a description of your system. All relevant measurements should be accounted for, as well as the reasoning that resulted in your design.

Your report should be sent by email to   as a PDF.

Hints
  • The noise is substantial and will cause trouble when measuring the properties of the channel. You will not be able to see the signal in the noise with your bare eyes. A good idea is to correlate in a suitable manner over long time.
  • A Bernoulli source can be used to generate independent bits.
  • There are no formal demands on the signal power. Note, however, that the saturation of the channel results in a power constraint.
  • Look around in Simulink. Most of what you need might be already available in the Simulink Communication Blockset.
  • First construct a working system. Then use whatever time you have left to improve it.
Files

The following Simulink models are needed or useful. Open them in Matlab version 7.13 or higher.

  • TSKS04.mdl. Open this first. The files below refer to it.
  • ProjektLib.mdl. Then open this. The file below refers to it.
  • A trivial, but working system using your channel. In the interactive Matlab window, you need to define the variables Rb=100 and Spb=1000. Rb is data-rate, i.e. the sample-rate of the Bernoulli source that generates the input. Spb is samples per bit, which tells us the number of samples that represents a signal interval. Note that Spb has to be an integer, while Rb can be fractional. The product of those has to be 100000. If you include error correction in your system, that must be adjusted based on the rate of the code.

The channel that you are supposed to use is the one that is used in the trivial example above. In case you encounter any difficulty, feel free to contact  .


Sidansvarig: Emil Björnson
Senast uppdaterad: 2019 07 30   10:16