Coded Diversity Combining and Channel Estimation for Wireless Data Communications

最近，一种新的用于蜂窝通信系统的检测后宏分集方案被提出。在这种称为多重检测宏分集(MDM)的新方案中，多个基站的信号被检测并被用作判决算法的输入，该判决算法提供关于所传输的内容的最佳判决。MDM方案在误码率(BER)方面有相当大的改善，特别是当移动台接近小区间边界时。由于小区间的边界恰恰是移动台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的误码率的效果。MDM方案的判决算法除了需要接收器的单独检测之外，还需要对接收信号的质量进行估计作为输入，以便可以在检测后合并过程中应用这些信号的适当“加权”。为了获得估计，通常执行某种类型的信道测量；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，测量过程使发射器/接收器硬件的设计和系统的操作复杂化。此外，测量结果的方差很大，需要随时间推移求平均值。为了避免基于测量的信号估计质量的缺点，我们建议使用信道编码来评估用于宏分集接收的无线信道的传输特性。所提出的信道估计方案利用译码过程中产生的边信息。综上所述，我们打算研究在单个站点配备多个分散的接收器的情况下以及在多个小区站点的情况下MDM结合编码的信道估计的使用。在后一种情况下，我们将研究检测后和检测前组合的使用(与接收信号的量化)，比较在存在移动通信环境所特有的信道损害的情况下的方案的性能。

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.