Wireless systems for mobile telephony and data transmission are currently undergoing very rapid development due to recent international agreements opening new regions in the radio spectrum to such services. These new systems, so-called third-generation wireless systems, will incorporate considerable signal-processiilg intelligence in order to provide advanced services such as multimedia. In order to make optimal use of available bandwidth for these services and to provide maximal flexibility, many such systems will operate as multiple-access systems, in which channel bandwidth is shared my many users on a random-access basis using protocols such as code division multipleaccess (CDMIA) signaling. Moreover, in order to support the high data rates inherent in such services, ratios of bit rates to bandwidths will be pushed to their limits. In general, wireless channels can be be very hostile media through which to communicate. Physical impairments such as multiple-access interference, co-channel interference, multipath transmission, amplitude fading, and dispersion due to limited bandwidth, all contribute to make it difficult to transmit data reliably and quickly through wireless channels. Moreover, the dynamism resulting from user mobility and the above-noted random-access nature of mobile channels, amplify the effects of these impairments, and make them much more difficult to ameliorate. Solutions to these difficulties lie in the use of advanced adaptive systems to perform advanced signal processing functions, and this proposal addresses such solutions.
Specifically, we plan to consider three general research problems within the area of adaptive equalization of multiple-access wireless channels: optimal methods for joint adaptive equalization and multiuser detection; adaptive linear and nonlinear methods for joint adaptive equalization and multiuser detection; and iterative methods for joint adaptive equalization and multiuser detection on coded channels. By addressing these research issues we can answer key questions about the equalization of wireless multiple-access channels. In particular, the consideration of optimal methods will establish baseline results by which other methods can be benchmarked. Furthermore, by considering low complexity adaptive linear and nonlinear methods, we can develop an understanding of mechanisms by which adaptivity can brought to bear on the problem at hand, and moreoever we. can examine the dynamics of adaptation in a tractable setting. And, finally, by consideration of iterative, and other adaptive nonlinear methods, we can seek adaptive techniques that can approach the ideals - of high performance and low complexity - established via the analytical results of the two other areas.
In order to accomplish these goals, it is necessary to take a novel approach to these problems, and in particular to synthesize technologies from disparate areas. Consequently, this studv will be conducted as a joint project among three institutions - ALGOREX, Inc., Cornell University, and Princeton University - bringing together considerable separate expertise in the fields of equalization, interference suppression, and adaptive system design to facilitate the necessary synthesis of ideas. ***
