Homework Assignment 8

What is the frequency of the following wave?
Suppose television transmitters use a 6MHz channel and that we can use them to transmit 8-level digital signals.
1. What is the maximum number of bits/sec that can be sent if the channel is noiseless?
2. Suppose the signal to noise ratio is 20dB, what is the maximum bit rate?
As you know from homework assignment 1, in a 1080p high-definition (HD) television system, each image is 1920x1080 pixels and an entire image is transmitted each cycle. Suppose each pixel in the image is represented by 24 bits (8 bits each for the red, green, and blue components) and that the images are not compressed in any way. How much bandwidth (in bits per second) is required to transmit 30 images per second?
Media access control (MAC) addresses are commonly expressed as 12 hexadecimal digits (i.e., 6 groups of 2 hexadecimal digits).
1. How many bits are there per MAC address?
2. How many MAC addresses are there (in total)?
How does the industry ensure that MAC addressess are unique?
Explain how a data error can lead an Ethernet system to (mistakenly) conclude that a giant or short frame error has occurred.
Consider the 802.11b protocol.
1. How many channels are there?
2. Why is there more than one channel?
3. How wide is each 802.11b channel?
4. Given what you know about data/signals, what are the important implications of the width of each channel?
What are the important differences between 802.11n and 802.11b? (Hint: You may need to do some independent research to find the answer to this question. Use a reputable source.)
Why shouldn't WiFi use CSMA/CD (even though Ethernet does)?
Suppose the probability of a collision for two wireless devices is 0.5.
1. What is the probability that there are three collisions in a row?
2. What important assumption did you make when calculating this probabilty?
3. When might this assumption be violated in practice?
How many devices can be in a Bluetooth piconet? Why?