Robust Codes for Space-Time Communication, Iterative Decoding, and Multi-Rate Broadcast

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The primary goal of this research is to produce practical codes that provideunequaled robustness, approaching the performance predicted by compoundchannel information theory for linear Gaussian channels. The resultingchannel codes will find application in many scenarios including wired andwireless broadcast, wireless local area networks, asymmetric digitalsubscriber lines, military anti-jam communications, and frequency hoppedcommunications.Results from compound channel information theory state that a single codeexists that supports communication over every channel that has a mutualinformation above the information rate of the code. Thus, once thetransmitter power spectrum is fixed, a code need not be specialized to aparticular frequency selective channel in a single antenna system or aparticular space-time path-gain matrix in a multiple antenna system. Whilethis theoretical result is more that thirty years old, practical code designhas focused to date on a weaker notion of robustness, that of averageperformance according to a statistical channel model, such as Rayleighfading. The power of the code design approach taken in thisresearch is that the code design is independent of statistical assumptionsabout the channel. The code simply works on every channel that it possiblycould.A second goal of this research is to develop codes that support multiplerates to different users. Here again, information theory (this timeinformation theory for degraded broadcast channels) lays out the limits ofperformance. Our research will closely approach these performance limits byapplying turbo codes to the concept of superposition coding for the degradedbroadcast channel.