Reduced-Dimension Decision Feedback Equalizers for High-Speed Wireless Digital Communications

用于高速无线数字通信的降维判决反馈均衡器

• 批准号: 0118842
• 负责人: Michael Zoltowski
• 金额: $ 29.82万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0118842&HistoricalAwards=false
• 关键词: Reduced; Dimension; Decision; Feedback; Equalizers

ABSTRACTThe primary problem addressed is the deleterious effect of dynamicmultipath propagation on high-speed wireless digital communications supporting real-time video and multimedia applications. Digital TV (DTV) is a target application along with Fourth Generation Cellular Communication Systems. Reflections off buildings and other structures cause ghosts and other artifacts in the reconstructed video stream. These multipath effects can wreak havoc on all functions of the receiver causingloss of synchronization and loss of carrier/timing recovery as wellas inter-symbol interference. Discrete ghosts are often associated with multipath conditions of large, flat surfaces, such as tall steel buildings. However, multipath conditions can occur in areas with hills and dense foliagewhere a signal can travel through many paths to the receiver. When the signalis bounced back from a moving object, complex ghosts can arise with a time-varying nature that is very challenging for the equalizer to overcome.To accommodate delay spreads of up to 40 microseconds, current generation Digital TV receiver chips employ a Decision Feedback Equalizer (DFE) with more than 100 Feed-Forward taps and more than 400 Feed-Back taps. This constitutes a large number of taps to adapt implying slow convergence and high computational complexity. Future high-speed wireless multimedia applications will place even more stressful demands on equalizer performance. The investigator will develop fundamental advances in the area ofreduced-dimension Decision Feedback Equalizers (DFE's).These include methods for dimensionality reduction based on apowerful reduced-rank adaptive filtering algorithm referred to as the Multi-Stage Nested Wiener Filter (MSNWF). The MSNWF providesconvergence speeds better than the Recursive Least Squares (RLS) algorithm,but at a much reduced computational complexity due to the fact that that the MSNWF constrains the overall weight vector to lie in a data-adaptive, low-dimensional subspace.The MSNWF has been successfully employed to effect a reduced-rank, linear equalizer for applications in Third Generation Cellular Communicationsbased on both CDMA Technology and the European GSM EDGE System. Theinvestigator will also develop other means for dimensionalityreduction including the use of the channel shortening concept employed in OFDM systems to reduce the length of the cyclic prefix, and symbol waveform compression achieved through simple linear filtering at the receiver.In addition, the investigator will study the use of reduced-dimension DFE'sfor equalization when block space-time coding is employed under frequency selective multipath conditions.

摘要要解决的主要问题是动态多径传播对支持实时视频和多媒体应用的高速无线数字通信的有害影响。 数字电视 (DTV) 是与第四代蜂窝通信系统一起的目标应用。 建筑物和其他结构的反射会导致重建视频流中出现重影和其他伪影。 这些多径效应会对接收机的所有功能造成严重破坏，导致同步丢失、载波/定时恢复丢失以及符号间干扰。离散重影通常与大型平坦表面（例如高层钢结构建筑）的多路径条件相关。然而，在有山丘和茂密树叶的地区可能会出现多径情况，信号可以通过许多路径到达接收器。当信号从移动物体反射回来时，会出现复杂的重影，其具有随时间变化的性质，这对于均衡器来说是非常具有挑战性的。为了适应高达 40 微秒的延迟扩展，当前一代数字电视接收器芯片采用了具有 100 多个前馈抽头和 400 多个反馈抽头的决策反馈均衡器 (DFE)。 这构成了大量的适应抽头，意味着收敛速度慢且计算复杂度高。 未来的高速无线多媒体应用将对均衡器性能提出更高的要求。研究人员将在降维决策反馈均衡器 (DFE) 领域取得根本进展。其中包括基于强大的降维自适应滤波算法（称为多级嵌套维纳滤波器 (MSNWF)）的降维方法。 MSNWF 提供比递归最小二乘 (RLS) 算法更好的收敛速度，但由于 MSNWF 将整体权重向量限制在数据自适应的低维子空间中，因此计算复杂度大大降低。MSNWF 已成功用于实现基于第三代蜂窝通信的降阶线性均衡器。 CDMA 技术和欧洲 GSM EDGE 系统。 研究人员还将开发其他降维方法，包括使用 OFDM 系统中采用的信道缩短概念来减少循环前缀的长度，以及通过接收器处的简单线性滤波实现符号波形压缩。此外，研究人员还将研究在频率选择性多径条件下采用块空时编码时使用降维 DFE 进行均衡。