ITR Collaborative Research: Achieving the Rate-Diversity Tradeoff in Space-Time Codes

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ABSTRACT0325180Xiang-gen XiaUniversity of DelawareThe term fading is used to describe the unpredictable and often rapid fluctuation in received signal strength encountered in a wireless communication environment. Dropped calls in cellular communication are often attributable to fading. A very effective and recent technique used to combat fading is to use multiple antennas at both input (transmitter end) and output (receiver end). The term space-time communication channel is used to describe the fading, wireless communication channel in the presence of multiple input and output antennas. Multiple input and output can be used to either increase the reliability of a wireless communication channel or else increase the rate at which information can be transmitted by a factor potentially equal to the number of transmit antennas. When used to both increase reliability and rate of information transfer, there is a tradeoff between the increase in information rate and the corresponding reliability of the communication link. This tradeoff is referred to as the rate-diversity tradeoff. A principal goal in the present project is the design of signal sets that will allow the user to pick an operating point along the rate diversity tradeoff curve. Other goals include helping define and achieve the limits of the space-time communication channel.More specific objectives include the design of signal sets that achieve the rate-diversity tradeoff and that are easy to decode, the study of alternative relevant notions of channel capacity such as delay-limited channel capacity, the study of other relevant channel models including those incorporating channel memory and correlated path gains, the study of the space-time channel in the presence of feedback as well as in the presence of sources having a multi-resolution capability.