The main purpose of this book is to help senior undergraduate students, graduate students, or young engineers design wireless communications systems by themselves. The basic architecture of wireless communications has not changed much in recent decades. Especially, most of the broadband wireless communications (WiMAX, LTE, WLAN, UWB, etc.) adopt similar techniques (OFDM/OFDMA, turbo codes/LDPC, MIMO, AMC, etc.). Therefore, this book is intended to provide the basic knowledge and methodology for wireless communications systems design. This book is based on my experience in various areas (standards, research and development) of wireless communications as a researcher, developer, and consultant.

Many different interests are entangled in the wireless communications systems design. The designed wireless communication system should satisfy various interested parties such as vendors, mobile operators, regulators, and mobile users. For example, in a wireless communication system, an officer of a regulatory agency will look for efficient spectrum usage and for violation of the regulation for the frequency band. A mobile operator will look out for business opportunities, service quality, and the cost of the infrastructure. A mobile phone vendor or a network equipment vendor looks for the cost-effective design of the wireless communication system. An end user is interested in whether or not it can use a network with enough data rates and seamless connection. In order to build wireless communication systems, we consider many requirements such as spectrum, system capacity, service area, radio resource allocation, cost, and QoS. Though it is not easy to find an optimal solution, we should find a good trade-off. Wireless communication system designers require a wide range of data because one decision in one design step is closely related to another decision in the next design step. This process is very complicated and it is very difficult to find an optimal solution. Thus, they often make a decision subjectively and empirically. This book provides the reader with a big picture of wireless communications systems design in terms of a mobile device designer. It covers from fundamentals of wireless communication theory to wireless communications block implementation and system integration.

A brief design flow of wireless communications systems is as follows: Firstly, international regulator such as the International Telecommunication Union (ITU) defines the spectrum allocation for different services. The regional regulatory bodies such as European Conference of Postal and Telecommunications Administrations (CEPT) in Europe and Federal Communications Commission (FCC) in the United States play quite an important role in decision making of ITU meetings. They are responsible for spectrum licensing and protection. After spectrum allocation for a certain service, ITU may label certain frequency allocations for a certain technology and determine the requirements for the technology. For the requirements, some standardization bodies such as the 3rd Generation Partnership Project (3GPP) and the Institute of Electrical and Electronics Engineers (IEEE) make their contributions to ITU to guarantee that their technology will meet the requirements. The actual technology is specified in the internal standardization such as 3GPP and IEEE and some standards are established at regional level. Secondly, a wireless channel is defined. Its mathematical model is developed to define the test scenario for the evaluation of the proposed technical solutions or algorithms. For example, short-range wireless channel models are different from cellular channel models. In cellular systems, we widely use empirical channel models such as ITU channel models. Thirdly, each block of the wireless communication system is selected to satisfy the requirement of the wireless communication system. This step is discussed and defined in wireless communication standards such as 3GPP and IEEE. The next steps are wireless communication system implementation. They are carried out by vendors. Fourthly, receiver algorithms under the given standard are selected and their performances are confirmed by a floating point design. Basically, standard bodies define interfaces, signaling protocol, and data structures and also give transmitter and receiver requirements. However, many freedoms of actual design and implementation are left. Fifthly, a fixed point design is performed. In this step, the architecture of a target wireless communication system is defined and the complexity can be roughly calculated. Lastly, conventional chip design processes as the remaining steps (RTL design and back-end design) are performed. This book focuses on each wireless communication algorithm design and deals with architecture design and implementation.

This book considers a broadband wireless communication system based on OFDM/OFDMA system because it is widely used in the modern wireless communication systems. The organization of the book is as follows: In Part I, the overall wireless communication theories are introduced. The basic structure of wireless communications systems is composed of a transmitter, a wireless channel, and a receiver. Their mathematical model is defined and their important theories are introduced. In addition, several physical layer techniques for mitigating wireless channel impairments are discussed. Chapter 5 “Wireless Channel Impairment Mitigation Techniques” provides a reader with fundamentals of Parts II and III. In Part II, key wireless communication blocks (FEC, MIMO, OFDM, channel estimation, equalization, and synchronization) are designed. In wireless communications systems, each block is deployed symmetrically. For example, if turbo encoder and QPSK modulator are used in a transmitter, turbo decoder and QPSK demodulator should be used in a receiver. Therefore, each block should be designed and verified pairwise. In Part III, wireless communications systems design is introduced from radio planning to system integration. Chapter 11 “Radio Planning” introduces a reader to wireless network design. In Chapter 12 “Wireless Communications System Design and Considerations,” we discuss the design methodology and implementation techniques. In Chapter 13, we roughly design a 4G mobile device.

I am pleased to acknowledge the support of VTT Technical Research Centre of Finland and John Wiley & Sons and the valuable discussion of my colleagues and experts in Lancaster University, University of Leeds, Nokia, Samsung, NEC, NICT, Cadence, and so on. I am grateful for the support of my family and friends.