Simplified Robust Adaptive Detection and Beamforming for Wireless Communications

2Wireless System Models

2.1 Introduction

In this chapter, mathematical models of DS/CDMA and orthogonal frequency division multiplexing (OFDM) systems are presented. These form the foundation of the robust adaptive detection algorithms that will be presented in this book. DS/CDMA and OFDM are used in 3GPP 3G and 4G systems respectively. The 5G systems under development by 3GPP will use evolved versions of OFDM. The algorithms presented in this book suit any of these systems and may also be extended to other systems.

The focuses of 3G and 4G were on mobile broadband thanks to smartphone adoption. The internet of things (IoT), with billions of devices expected to be connected to the internet, has directed the 3GPP and industry towards narrowband technologies. 3GPP has modified the LTE system to meet IoT requirements by introducing NB‐IoT. Other proprietary technologies in unlicensed bands, known as low‐power wide area (LPWA) networks, have used narrowband or ultra‐narrowband approaches such as SigFox. Other LPWA networks have adopted a wideband CDMA approach based on chirp spread spectrum (CSS). One example is LoRa.

The focus of this book is not on particular commercial technologies, and readers will require some effort in order to match the detection and beamforming algorithms developed in this book to specific practical systems. The focus of the book is on the development and comparative analysis of robust adaptive detection and beamforming algorithms based on simplified system models. ...