Advances in Multiuser Detection

7

INTERFERENCE AVOIDANCE FOR CDMA SYSTEMS

Dimitrie C. Popescu Sennur Ulukus Christopher Rose Roy Yates

7.1 INTRODUCTION

Though the success of cellular telephony heralds the wireless age, wireless networking by the masses is a relatively new and exciting phenomenon with potentially even larger impact on our society. Accelerating sales of wireless LANs (802.11) for home and small office use, and even small business as a customer lure, indicate that wireless connectivity is increasingly seen as an important, if not vital, part of modern life. In addition, there is demand for other wireless networking technology geared toward different applications such as wiring replacement (Bluetooth, HomeRF), paging networks, and wide area email access (Blackberry). Furthermore, as wireless networks become more ubiquitous and less expensive, sensor/actuator networks, now primarily the commercial domain of burglar/fire alarms and climate control, could become much more prevalent.

However, the increasing demand for various wireless services is tempered by simple economics. Usable spectrum is scarce and therefore expensive. Thus, applications which cannot be deployed almost full-blown with a predictably stable revenue base (i.e., cellular systems) cannot usually afford spectrum licenses and must therefore share use of various unlicensed bands—for example, the Unlicensed National Information Infrastructure (UNII [9]) at 5 GHz and other unlicensed bands at 900 MHz and 2.4 GHz.

Unfortunately, shared spectrum ...