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Unformatted text preview: UCSB Spring 2011 ECE 146B: Communications II Lab 3: Introduction to Channel Equalization Assigned: April 22 Due: May 13 (at the beginning of the lab session) Reading: Chapter 4 (linear modulation) and Chapter 6 (Section 6.1 on Gaussian random variables and Q function). We also state and use probability of error expressions from Chapter 6, but reading about how these are derived is not required at this point. Lab Objectives: To understand the need for equalization in communication systems, and to implement linear MMSE equalizers adaptively. Laboratory Assignment 0) Use your own code from Lab 1 or Lab 2 as a starting point. If you had difficulty in completing these labs, ask the instructor or TA for a template. As before, the transmit, channel, and receive filters are implemented at rate 4 /T . For simplicity, we consider BPSK signaling throughout this lab, and consider only real-valued signals. Generate nsymbols = ntraining + npayload (numbers to be specified later) ± 1 BPSK symbols as in Lab 2, and pass them through the transmit, channel, and receive filters to get noiseless received samples at rate 4 /T . 1) Let us start with a trivial channel filter as before. Set nsymbols = 200. The number of rate 4 /T samples at the output of the receive filter is therefore 800, plus tails at either end because the length of the effective pulse modulating each symbol extends over multiple symbol intervals. Take, say, 400 samples from somewhere in the middle of these samples, avoiding the tails. Divide these into segments of length equal to 2 symbol intervals, or 8 samples (you can do this by reshaping the column vector of 400 samples into an 8 × 50 matrix). Plot these overlapped intervals against time, expressed in units of the symbol interval (i.e., the x axis goes from 0 to 2, since you are plotting segments of the received waveform spanning two symbol intervals). You should get something like Figure ?? , which is called an eye diagram because of its shape. The figure shows many different trajectories corresponding to thebecause of its shape....
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This note was uploaded on 09/10/2011 for the course ECE 146B taught by Professor Upamanyumadhow during the Spring '11 term at UC Merced.
- Spring '11