Digital Communications with Emphasis on Data Modems

15COMMUNICATION RANGE EQUATION AND LINK ANALYSIS

15.1 INTRODUCTION

This chapter deals with numerous issues related to the design of the data modulator, transmitter, antennas, receiver, and demodulator subsystems as they relate establishing the system performance over a communication link. A communication link, as defined here, involves issues related to the transmission of data from one point to another and, in addition to the various systems, includes the transmission channel. The focus is on the received signal and noise powers and the resulting signal‐to‐noise ratio required to meet the overall system performance specification. The channel is generally viewed as the transmission medium between a transmitter and receiver location and the emphasis in this chapter is on wireless channels involving transmissions through the atmosphere and ionosphere. The link might include, for example, a satellite relay with unique uplink and downlink channels. The satellite relay may be thought of as a “bent pipe” with frequency translation and power amplification or a full processing satellite in which the data is demodulated and then remodulated for transmission on an independent downlink. The emphasis in this chapter is on the application of the communication range equation in analyzing the system performance over wireless channels. Chapter 18 introduces the subject of fading channels. Chapters 19 and 20 focus is on the impact of atmospheric and ionospheric propagation on the communication ...