Introduction

In Chapter 1 the working definition for cognitive radio used throughout this book was presented. That definition ended with the statement ‘A cognitive radio is made from software and hardware components that can facilitate the wide variety of different configurations it needs to communicate.’ In this chapter we look at the hardware involved. There is no one right way to build a cognitive radio so the chapter merely aims to give a sense of what kind of hardware can be used and some of the related performance issues.

A complete cognitive radio system

In a cognitive radio receiver, the antenna captures the incoming signal. The signal is fed to the RF circuitry and is filtered and amplified and possibly downconverted to a lower frequency. The signal is converted to digital format and further manipulation occurs in the digital domain. On the transmit side the opposite occurs. The signal is prepared and processed and at some stage is converted from digital to analogue format for transmission, upconverted to the correct frequencies and launched on to the airwaves via the antenna.

Throughout this book we have been using the terms ‘cognitive radio’ and ‘cognitive node’ interchangeably. The reason for this is that a cognitive radio will almost all of the time function as a node in a network. Therefore it is useful to think of the complete cognitive radio system in terms of a communication stack.