Subject Spotlight: Communication Systems

Welcome to a series covering the variety of electrical engineering subjects available at Melbourne Uni. This series hopes to give those who have not done the subjects a more overall outlook of what the subject entails, tips and more interesting information that is only known by those who have done the subject.

Disclaimer: These articles are written from past experiences and may not reflect what the subject is currently like or will be like in the future. The opinions expressed are purely the authors’ and not representative of the Melbourne Uni Electrical Engineers Club or the University of Melbourne. In no way is anything here presented as fact. Do not come complaining to us if after reading something you think the subject is easy and then you fail or if something crucial has changed in the subject.

Year this subject was taken: 2016

Communication Systems explores what happens to a signal when transmitted across different telecommunication technologies. Examples include AM and FM radio, television and lastly digital systems. This subject focuses, time wise, mostly on analog systems with the last fifth of the subject on digital systems. It is a good idea to do this subject alongside Signal Processing as the two subjects are closely intertwined, even though Signal Processing is wholly focused on digital communications.

It should be quite obvious that Communication Systems is the prerequisite to Advanced Communication Systems, from the handbook Advanced Communication Systems is focused on the digital aspect of communications.

Topics:

  • Signals, Spectra, LTI Systems (Revision of Signals and Systems)
  • Distortion, equalisation, bandpass signals and systems
  • Modulation and demodulation general
  • Types of linear modulation (DSBSC, AM, SSB, VSB)
  • Types of non-linear (angle) modulation (FM, PM)
  • Phase Lock Loops (Feedback)
  • Revision of Probability and Random Processes
  • Noise in linear modulation
  • Noise in FM modulation
  • Threshold Effect
  • Digital Communication, Quantisation, Waveform Coding, Pulse-code modulation

For the types of modulations, their formulas, transmission power and time domain/frequency domain views are explored, and for the noises their figure of merits are explored.

Lectures:

The lecturer for Communication Systems is Prof William (Bill) Shieh, lecture slides are less detailed as there is an emphasis on in lecture examples and discussion.

Prior Knowledge:

Signals and Systems and Probability and Random Models are revised briefly in this subject but proper practice is advised.

Signals and Systems is an overall requirement for this subject, as all the basics of different signals, fourier transforms, systems properties are taught in that subject.

Probability and Random Models is required as noise in communications are represented as Gaussian random processes. Hypothesis testing is used in Binary Pulse-Code modulation to calculate the probability of bit flip errors and to chose their threshold.

Workload:

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That's right, we use that big thing in the workshop that we all see but never use.

In the workshops the TIMS modules are used to simulate telecommunications. There are in total 4 workshops over multiple weeks, sometimes with a break week in between. Reports are to be written and handed in the next workshop.

Workshops groups are allocated and each group is 2 people. Workshop reports are shared.

There is a tutorial that runs like a lecture every week where the tutor/lecturer goes through some tutorial questions. The questions are made available the week before.

The mid-semester test is one hour and is made up of several questions similar to what would be on the final exam. Three A4 double sided pages of notes are allowed into the mid-semester test as well as the final exam.

Tips:

Even though lectures and tutorials are recorded, don't assume the recording works, and sometimes what is written on the projector is not recorded.

It is a good idea to read from other sources such as the textbook alongside lecture slides before the lecture.

When in doubt about how to wire something in the workshops read the TIMS manuals.

For the '100kHz Channel Filters' TIMS module, the channel select switch for bandpass filter is 3 not 2 as said in the TIMS manual. (Might have since changed)

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FFT Spectra of a modulated signal.

Aside from the digital portion of the subject, all the analog topics require knowledge of the previous section so you have to keep up with all the lectures.

The oscilloscopes may be so old that they can't detect a flash drive that is more than 2 GB, but its not recommended to use the inbuilt save to flash drive function anyway because you lose the scale on the bottom of the readout, as well as anything displayed by the measure sidebar.

Take a picture of the oscilloscope readout with your phone and use an app like CamScanner to clean up the image quickly.

 


BY Dennis Nguyen

Melbourne University Electrical Engineering Club

2017

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