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

这项研究的主要目标是产生实用的代码，提供无与伦比的鲁棒性，接近复合信道信息理论对线性高斯信道预测的性能。由此产生的信道码将在许多场景中得到应用，包括有线和无线广播、无线局域网、非对称数字用户线路、军事抗干扰通信和跳频通信。复合信道信息理论的结果表明，存在一个单一的码，它支持在每个信道上的通信，这些信道具有高于码的信息速率的互信息。因此，一旦发射机功率谱固定，编码就不需要专门用于单天线系统中的特定频率选择信道或多天线系统中的特定时空路径增益矩阵。虽然这个理论结果已经有三十多年的历史了，但实际的代码设计迄今为止关注的是一个较弱的鲁棒性概念，即根据统计信道模型（如瑞利衰落）计算平均性能。本研究中采用的代码设计方法的强大之处在于，代码设计独立于有关信道的统计假设。代码只是在它可能的每个通道上工作。这项研究的第二个目标是开发支持不同用户乘法的代码。在这里，信息理论（这次是针对降级广播信道的信息理论）再次列出了性能的限制。我们的研究将通过将turbo码应用于退化广播信道的叠加编码概念来接近这些性能限制。

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.