PERFORMANCE EVALUATION OF MULTI -USER CDMA USING IMPORTANCE SAMPLING

Abstract

Wireless communication is expected to be the dominant mode of access technology in the next century. Besides voice, a new range of services such as multimedia, high-speed data, etc. are being offered for delivery over wireless networks. Mobility will be seamless, realizing the concept of persons' being in contact anywhere, at any time. To make future mobile systems globally acceptable, standardization efforts are underway in the International Telecommunications Union. Over the past several years, CDMA (Code Division Multiple Access) has been shown to be a viable alternative to both frequency division multiple access (FDMA) and time division multiple access (TDMA), and the use of spread spectrum techniques (upon which CDMA is based) in wireless communications has become a very active area of research and development [23] [24]. While there does not appear to be a single multiple accessing technique that is superior to others in all situations, there are characteristics of spread spectrum waveforms that give CDMA certain distinct advantages. The two basic problems which the cellular mobile radio system designer is faced with are multipath fading of the radio link [1] and interference from other users in the cellular reuse environment [35]. Spread spectrum signals are effective in mitigating multipath because their wide bandwidth introduces frequency diversity. They are also useful in mitigating interference, again because of their wide bandwidth. The result of these effects is a higher capacity potential compared to that of nonspread access methods,