Dr. M. Moh, CS 258 Homework 6 Spring 2008

(Revised 4/5/08)

Note: Refer to Prof Raj Jain’s slides on (a) Physical Layer (2006) for Problems 1 – 3 and (b) Local Area Networks (2008) for Problems 4.

1. A telephone line is known to have a loss of 20 dB. The input signal power is measured at 1 Watt, and the output signal noise level is measured at 1 mW. Using this information, calculate the output signal to noise ratio in dB.

2. What is the maximum data rate that can be supported on a 10 MHz noise-less channel if the channel uses eight-level digital signals?

3. What signal to noise ratio (in dB) is required to achieve 10 Mbps through a 5 MHz channel?

4. Two 802.11 stations get frames to transmit at time t=0. The 3^rd station has just finished transmitting a long packet at t=0. The transmission parameters are: Slot time=1, SIFS=1, DIFS=3, CWmin=5, CWmax=7. Assume that the pseudo-random number generated are 1, 3. The frame size is 3 slots. Draw a transmission diagram. How many slots before the two packets will get acknowledged assuming no new arrivals?

5. Read Textbook Chapter 5 (TCP Modeling) and try the review problems.

6. Read Textbook Chapter 6 (TCP Performance over Wireless Networks) and try the review problems.

7. Study slides on “MANET routing”.