Coded Diversity Combining and Channel Estimation for Wireless Data Communications

近年来，针对蜂窝通信系统提出了一种新的检测后宏分集方案。在这种被称为多重检测大分集（multiple - detected Macrodiversity， MDM）的新方案中，会检测多个基站的信号，并将其用作决策算法的输入，该算法提供传输内容的最佳决策。MDM方案在误码率（BER）方面有相当大的改进，特别是当移动设备靠近小区边界时。由于小区之间的边界正是移动信号质量受损最严重的区域，因此MDM方案具有均衡整个系统覆盖区域内的误码率的作用。MDM方案的Decision Algorithm除了需要对接收端进行单独的检测外，还需要对接收信号的质量进行估计，以便在检测后的组合过程中对这些信号进行适当的“加权”。为了获得估计，通常要进行某种信道测量；例如，信号功率（S分集）或信号干扰比（S/ i分集）。在这种情况下，测量过程使发送/接收硬件的设计和系统的操作复杂化。此外，测量结果受到高方差的影响，需要随时间平均。为了避免基于测量的信号质量估计的缺点，我们建议研究使用信道编码来评估宏分集接收无线信道的传输特性。所提出的信道估计方案使用解码过程中产生的侧信息。总之，我们打算研究MDM结合编码信道估计在单个站点配备多个相距很远的接收器和多个蜂窝站点的情况下的使用情况。在后一种情况下，我们将研究使用后检测和预检测组合（与接收信号的量化），比较在存在信道损伤特征的情况下方案的性能与移动通信环境。

Recently, a new post-detection macrodiversity scheme was proposed for cellular communication systems. In this new scheme, termed Multiply-Detected Macrodiversity (MDM), the signals at multiple base stations are detected and used as input to a Decision Algorithm, which provides an optimal decision of what was transmitted. The MDM scheme shows considerable improvement in the Bit-Error Rate (BER), especially when the mobile is close to the boundary between cells. As the boundary between cells is exactly the region in which the quality of the mobile's signal is mostly impaired, the MDM scheme has the effect of equalizing the BER throughout the system coverage area. The Decision Algorithm of the MDM scheme requires as an input, in addition to the separate detections of the receivers, also an estimation of the quality of the received signals, so that appropriate"weightings" of these signals can be applied in the post-detection combining process. To obtain estimates, usually some sort of channel measurement is performed; e.g., the signal power (S-diversity) or the Signal-to-Interference-Ratio (S/I-diversity). In such cases, the measurement process complicates the design of the transmitter/receiver hardware and the operation of the system. Furthermore, the measurements are subject to high variance and need to be averaged over time. To avoid the disadvantage of the measurement-based quality of signal estimation, we propose here to investigate the use of channel coding to evaluate the transmission characteristics of a wireless channel for macrodiversity reception. The proposed channel estimation schemes use side information generated during the decoding process.In summary, we intend to study the use of the MDM combining with coded channel estimation in the case of a single site equipped with multiple,widely-separated receivers and in the case of multiple cell sites. In the latter case, we will investigate the use of both post-detection and predetection combining (with quantization of the recei ved signal), comparing the performance in the schemes in the presence of channel impairments characteristic to the mobile communication environment.