An Introduction to 5G

5Digital Signal Processing

This chapter addresses the principles of digital signal processing on the 5G air interface. There are three main topics. The first covers the underlying techniques for transmission and reception that 5G has inherited from 2G and 3G systems, for example modulation, demodulation and channel estimation. The second covers orthogonal frequency division multiple access (OFDMA), a technique inherited from LTE through which the base station can communicate with several different mobiles at the same time. The third covers the management of errors in the received data stream by means of forward error correction and re‐transmission. We will also discuss a number of issues which appear at high radio frequencies and are especially relevant to 5G.

This chapter contains more mathematics than most of the others in this book, but it has been kept lightweight with the aim of making the material accessible to those without a mathematical background. The Bibliography has several references for further reading, for both the material in this chapter and the underlying maths.

5.1 Modulation and Demodulation

5.1.1 Carrier Signal

In a wireless communication system, the radio wave from Chapter 4 is known as a carrier signal. Mathematically, we can express the carrier signal as follows:

(5.1)

Here, a is the amplitude of the radio wave, φ is its initial phase angle and