Syudy on Frame Synchronization Methods for Digital Satellite Communications System

在数字卫星通信系统中，帧同步是提供数字传输服务的基本功能。它包括被称为“唯一字(UW)”的帧同步模式的检测，以及通过连续检测UW来建立同步。接收端的UW检测是基于接收信号向量与UW向量在多维空间中的欧几里得距离来实现的，该距离的维度与UW的长度一致。从实用的角度讨论了量化软判决数据在UW检测中的应用，建立了获取各种UW检测特性的理论和实验方法。通过与传统硬判决数据和非量化软判决数据的比较，定量地评估了所获得的唯一漏字、误检测等性能。定量评估结果表明，量化软判决数据的应用具有有效实现符合设计目标的UW检测的潜力。对于帧同步，建立了一种从UW检测的帧同步特性计算各种帧同步特性的理论方法。定量评估表明，与硬判决和非量化软判决数据相比，在低信噪比条件下，使用软判决数据的UW检测在重帧时间和同步丢失检测和重帧时间准则上具有更好的性能。

Frame synchronization is an essential function for providing digital transmission services in digital satellite communications systems. It consists of a detection of frame synchronization pattern called "Unique Word (UW)", and an establishment of synchronization by detecting UWs consecutively. The UW detection in the receiving side is realized based on Euclidian distance between received signal vector and UW vector in multi-dimentional space, the dimension of which coincides with the length of UW. An application of quantized soft-decision data to UW detection is discussed from the practical point of view, and a theoretical and experimental approaches are established for obtaining a variety of UW detection characteristics. The obtained performance such as unique word missed, false detections and so on is quantitatively evaluated, compared with that of conventional hard-decision data and non-quantized soft-decision data. It is concluded from the quantitative evaluation that the application of quantized soft-decision data has potential to realize effectively the UW detection complying with design objective. With respect to the frame synchronization, a theoretical approach is established for calculating a variety of frame synchronization characteristics from those of UW detection. It becomes obvious from the quantitative evaluation that the UW detection using soft-decision data provides better performance on the criteria of reframe time and sync loss detection & reframe time in the low C/N condition, compared to the use of hard-decision and non-quantized soft-decision data.