Communication Systems Principles Using MATLAB

6Data Transmission and Integrity

6.1 Chapter Objectives

On completion of this chapter, the reader should be able to:

1. Distinguish between error detection and error correction.
2. Calculate the bit error probabilities for a simple channel coding scheme.
3. Understand the working of algorithms for block error detection and block error correction.
4. Explain the operation of convolutional coding, including path‐search algorithms.
5. Explain private (secret) key encryption, key‐exchange methods, and public‐key encryption.

6.2 Introduction

Digital communications clearly depends on getting the correct bit sequence from the sender to the receiver. In a real communication system, there is no guarantee that the stream of bits emanating from the encoder will be received correctly at the decoder. Some bits may be subject to random errors due to noise and other factors such as clock synchronization. An important distinction is between error detection and error correction. Detecting errors is easier than correcting them. Not only do we usually require the correct bit sequence; the data must also be delivered in the correct order. Although this may sound strange, it is possible in packet‐switched systems for the correct blocks of data to be delivered, but out of order.

In addition to checking data integrity due to random events, it is often important to ensure that there is no compromise to data integrity due to deliberate manipulation or theft of confidential data. The Internet represents anessentially ...