Wireless Networks

Future wireless networks will enable people on the move to communicate with anyone, anywhere, at any time, using a range of multimedia services. The exponential growth of cellular telephone and paging systems coupled with the proliferation of laptop and palmtop computers indicate a bright future for such networks, both as stand-alone systems and as part of the larger networking infrastructure. In this chapter we provide an overview of wireless networks. We begin in Section 1.1 with a brief introduction to these networks, including their history, their future, and their technical challenges. The greatest technical challenge to wireless network design is the underlying wireless channel. In Section 1.2 we describe the main characteristics of the wireless channel and how these characteristics impact the link layer and network design. Link layer design techniques that overcome wireless channel impairments to deliver high data rates with low distortion are described in Section 1.3. The wireless channel is a limited resource that must be shared among many users. In Section 1.4 we describe channel access protocols for sharing this resource in an eecient and fair manner. Section 1.5 outlines design issues for wireless networks, including network architecture, user location and routing protocols, network reliability and QOS, internetworking between wireless and wired networks, and security issues. Current wireless network technology is described in Section 1.6 including cellular and cordless telephones, wireless LANs and wide-area data services, paging systems, and global satellite systems. Section 1.7 gives an overview of emerging systems and standards for future wireless networks. We conclude the chapter in Section 1.8 with a summary and discussion of the design trends and challenges for future wireless networks. 1.1 Introduction Wireless communications is, by any measure, the fastest growing segment of the communications industry. As such, it has captured the attention of the media and the imagination of the public. Cellular phones, cordless phones, and paging services have experienced exponential growth over the last decade, and this growth continues unabated worldwide. Wireless communications has become a critical business tool and part of everyday life in most developed countries. In addition, wireless communication systems are rapidly replacing antiquated wireline systems in many developing countries. Will future wireless networks live up to their promise of multimedia communications anywhere and any time? In this introductory section we will brieey review the history of wireless networks, from the smoke signals of the Pre-industrial age to the cellular, satellite, and wireless …