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CS249 Digital Communications and Signal Processing


Notice: Please go to Chris' website for 2010 seminars.

Note: Please make sure you attend the final two seminars as the questions discussed in the seminar will be very similar to the final exam questions.

Seminar 1 (week 2): Matlab Introduction, DTMF matlab script

Seminar 2 (week 3): Fourier Transform exercise, solution,

last year's exercise with solution

Seminar 3 (week 4): Notes,


Matlab code

Seminar 4 (week 5): Notes

Datafile: Midsummer, Message

Solutions: Part I , Part II

2007 Seminar with solution.

Seminar 5 (week 6): DTFT and DFT exercise, solution

seminar 6 (week 7): DFT and Matlab Notes, Signal data

seminar 7 (week 8): Filter Design Notes, Solution

seminar 8 (week 9): Wiener filter exercise, solution

seminar 9 (week 10): No seminar...


2009 assignment

Reference answer

For Question 2, download one the signals below. Each signal corresponds to a different 300x300 black-and-white bitmap image. Prior to modulation, the data was augmented by one extra column and row to include parity bits (odd parity for rows, even parity for columns). ASK and Manchester coding were used for modulation. The carrier frequency is 1000 Hz. The data is trasmitted row after row. At the end each row, an 'end-of-row' signal is trasmitted (5 periods of a sinusoid wave at half the frequency of the carrier). The sample rate of the wave file is 5000 Hz. Encoder program (Matlab code)

  • Signal 1
  • Signal 2
  • Signal 3
  • Signal 4
  • Signal 5
  • Signal 6
  • Signal 7
  • Signal 8

For Question 8, download one the two datafiles below and try to remove noise as much as you can. In both cases the original signal is an excerpt from Handel's "Halleluja" chorus. The sampling frequency is 8192 Hz.

  • Download datafile 1 -- (play)
  • Download datafile 2 (challenge) -- (play)
  • Email your solutions to