Turbo Coded Modulation for Partially Coherent Channels

翻译后摘要：本研究认为，部分相干信道的带宽效率的编码调制的设计。实际上，当相干接收机在低或中等信噪比（SNR）下操作时，会出现这种信道，从而导致有噪声的相位估计。这例如发生在无线信道上，其中多径衰落导致接收SNR的波动。这项研究利用了最近的一项突破，称为涡轮编码，其中在发射机的两个或更多个编码器的输出在接收机迭代解码，导致在1 dB的信道容量的SNR可靠的通信。本研究将相位追踪误差整合到涡轮编码调变设计的各个方面，进而降低实际相干通讯系统所需的信噪比。本研究的目标是在部分相干信道（PC）上，包括PC加性白色高斯噪声（AWGN）信道，以及具有和不具有信道状态信息（CSI）、具有和不具有相关衰落以及具有闭环和开环相位估计的PC衰落信道。调查研究的PC信道的信息容量，并确定能力实现输入概率密度函数（PDF）和容量最佳的星座等概率和非等概率信令平均和峰值功率约束下。距离度量的成对符号错误概率的基础上，将推导出PC衰落信道，迭代解码器的性能预测工具的基础上联合界和收敛区域分析将开发。然后，研究人员将研究集划分，比特到符号的映射，以及线性和非线性递归卷积编码器用作级联网格编码调制方案中的组成码的代码搜索程序。最后，成形码设计技术的功率受限的PC信道上的Turbo编码调制将开发，这些信道的容量实现PDF的基础上，这是已知的非高斯。这些代码将塑造编码器输出符号序列的高维空间，使得诱导的二维PDF将紧密地近似于容量最优的输入PDF。

Abstract:This research considers the design of bandwidth efficient coded modulation for partially coherent channels. Such channels occur in practice when coherent receivers are operated at low or moderate signal-to-noise ratios (SNRs), resulting in noisy phase estimates. This happens for example on wireless channels, where multipath fading causes fluctuations in received SNR. This research leverages a recent breakthrough known as turbo coding, wherein the outputs of two or more encoders at the transmitter are iteratively decoded at the receiver, resulting in reliable communication at SNRs within 1 dB of channel capacity. This research integrates phase-tracking error into all aspects of turbo coded modulation design, thereby reducing the required SNR for practical coherent communication systems. The new design techniques stemming from this research will therefore interest not only communication and coding theorists, but also engineers designing practical communication systems.The goal of this research is to develop theoretically based, practical design methods for parallel and serially concatenated turbo coded modulation over partially coherent (PC) channels, including PC additive white Gaussian noise (AWGN) channels, and PC fading channels with and without channel state information (CSI), with and without correlated fading, and with closed-loop and open-loop phase estimation. The investigators study the information capacity of PC channels, and determine capacity-achieving input probability density functions (PDFs) and capacity-optimal constellations for equiprobable and non-equiprobable signaling under average and peak power constraints. Distance metrics based on pairwise symbol error probabilities will be derived for PC fading channels, and iterative decoder performance prediction tools based on union bounds and convergence-region analysis will be developed. The investigators will then study set-partitioning, bits-to-symbol mapping, and code-search procedures for both linear and non-linear recursive convolutional encoders used as constituent codes in concatenated trellis-coded modulation schemes. Finally, shaping code design techniques for turbo coded modulation on power-constrained PC channels will be developed, based on the capacity-achieving PDFs of these channels, which are known to be non-Gaussian. These codes will shape the high-dimensional space of encoder output symbol sequences so that the induced two-dimensional PDF will closely approximate the capacity-optimal input PDF.