Chapter 5

Homework Assignment 5 Chapter 5 & 6

CSC 571 HW-5

1. What is digital-to-analog conversion?

A process in which signals having a few (usually two) defined levels or states (digital) are converted into signals having a theoretically infinite number of states (analog). A common example is the processing, by a modem, of computer data into audio-frequency (AF) tones that can be transmitted over a twisted pair telephone line.

2. Explain aspects of digital-to-analog conversion in terms of data elements vs. signal element, data rate vs. signal rate, bandwidth, and carrier signal.

data elements vs. signal element : data element as the smallest piece of information to be exchanged, the bit. We also defined a signal element as the smallest unit of a signal that is constant.

data rate vs. signal rate: We can define the data rate (bit rate) and the signal rate (baud rate) as we did for digital transmission. The relationship between them is S=Nx! Baud R where N is the data rate (bps) and r is the number of data elements carried in one signal element. The value of r in analog transmission is r =log2 L, where L is the type of signal element, not the level. The same nomenclature is used to simplify the comparisons.

bandwidth: The required bandwidth for analog transmission of digital data is proportional to the signal rate except for FSK, in which the difference between the carrier signals needs to be added.

carrier signal: In analog transmission, the sending device produces a high-frequency signal that acts as a base for the information signal. This base signal is called the carrier signal or carrier frequency. The receiving device is tuned to the frequency of the carrier signal that it expects from the sender. Digital information then changes the carrier signal by modifying one or more of its characteristics (amplitude, frequency, or phase). This kind of modification is called modulation (shift keying).

3. Explain amplitude shift keying, frequency shift keying, and...