Chapter Overview

Since the mid-1970s, the proliferation of applications that send digital data over communication channels has resulted in the need for efficient methods of transmission, conversion, and reception of digital data. As with analog data, the amount of digital information that can be transmitted is proportional to the bandwidth of the communication channel and the time of transmission. This chapter further develops some of the basic concepts and equipment used in the transmission of digital data, including some mathematical principles that apply to transmission efficiency, and discusses the development of digital modulation, standards, error detection and correction methods, and spread spectrum techniques.

Chapter Outline

11-1 Digital Codes
11-2 Principles of Digital Transmission
11-3 Transmission Efficiency
11-4 Modem Concepts and Methods
11-5 Wideband Modulation
11-6 Broadband Modem Techniques
11-7 Error Detection and Correction
11-8 Protocols

Chapter Objectives

• Explain the difference between asynchronous and synchronous data transmission.
• State the relationship between communication channel bandwidth and data rate in bits per second.
• Name the four basic types of encoding used in the serial transmission of data.
• Describe the generation of FSK, PSK, QAM, and OFDM.
• Name three types of data modems and explain how they operate.
• Explain the need for and types of communication protocols.
• Compare and contrast redundancy, parity, block-check sequences, cyclical redundancy checks, and forward error correction.
• Explain the operation and benefits of spread spectrum systems.