Algorithms for Communications Systems and their Applications, 2nd Edition

Chapter 4Transmission channels

This chapter introduces the radio channel with its statistical description and associated numerous parameters, including the use of multiple antennas at the transmitter and/or receiver. Briefly, we also mention the telephone channel, which however is gradually replaced by optical fibres.

4.1 Radio channel

The term radio is used to indicate the transmission of an electromagnetic field that propagates in free space. Some examples of radio transmission systems are as follows:

• point‐to‐point terrestrial links [1];
• mobile terrestrial communication systems [2–6];
• earth–satellite links (with satellites employed as signal repeaters) [7];
• deep‐space communication systems (with space probes at a large distance from earth).

A radio channel model is illustrated in Figure 4.1, where we assume that the transmit antenna input impedance and the receive antenna output impedance are matched for maximum transfer of power.

Figure 4.1 Radio channel model.

4.1.1 Propagation and used frequencies in radio transmission

Propagation over the various layers of the atmosphere is denoted respectively as ionospheric and tropospheric propagation, while propagation occurring very close to the earth's surface is denoted as ground propagation. The importance of each of propagation methods depends on the length of the path and the carrier frequency [8].

Basic propagation ...