ELEC 471, Spring 1999
Prof. Rich Kozick

Homework 3

Date Assigned: Thursday, January 28, 1999
Date Due: Thursday, February 4, 1999

  1. Exam 1 will be on Thursday, February 4. The topics will include everything that we have done in class through January 28. This includes topics in the text in Sections 1.1-1.6, as well as the digital communication application.

  2. Reading: Continue studying Chapter 1, Sections 1.8 and 1.9. Also read Chapter 2 for class on February 11.

  3. Implement a MATLAB simulation of the digital communication system that we discussed in class. Use the "decision rule" discussed in class to decide whether a -1 or +1 was transmitted based on the observation of the noisy value. Compute the probability of a bit error (also called bit error rate or BER) in your program. Compare the BER in your simulation with the BER that we computed analytically.

    Please submit a printout of your MATLAB program, the BER obtained in your simulation (how many "trials" should you perform to get accurate results?), and a comparison with the analytical BER. Also include a clear and complete explanation of how your receiver makes decisions and how the BER is computed analytically.

    Modify your simulation program so that each bit is transmitted three times, with independent noise added on each transmission. Make your "overall" decision for each bit as the majority of the three individual decisions. What is the BER for this system, based on your simulation? Please derive the analytical BER for this system, and compare with your simulation result. For some hints on the analysis of this system, refer to Section 1.9, and Example 1.36 in particular. Or, you can just look at the sample space of repeating the experiment three independent times.

  4. I will be available on Friday 12-1 and 2-3, and on Monday 12-1 and 2-3 if you have any questions. I will be out of town from Tuesday, February 2 through Sunday , February 7.
Thank you and have fun!