Low-Complexity and High-Performance Equalization for Wireless MIMO Communication Systems in Frequency Selective Fading Channels

无线通信在过去十年中得到了极大的发展。事实上，最新的预测是增长将会继续。未来的无线通信系统有望支持高速、高质量的多媒体业务。为了提高无线通信的质量和容量，多输入多输出（MIMO）系统已经被提出利用来自发射器和接收器的多个天线的信号。即使作为一项相对较新的技术，MIMO已经以空时编码的形式被第三代（3G）无线标准所采用，并且被认为是第四代（4G）和其他未来系统的重要组成部分。然而，在频率选择性衰落信道中，由于信号的多径延迟，MIMO系统的性能严重下降。因此，这一难题需要有效的解决方案。在有限的频率带宽内提供对数据速率要求不断增加的高质量业务是一项重大挑战。这一建议为研究提供了一些思路，有可能克服上述缺点。此外，这提供了低复杂性，这是从功耗的角度来看是一个重要的问题，以及高性能，这是客户所希望的。单载波频域均衡（FDE）已被证明是解决频率选择性衰落信道的有效方法。在本研究中，将研究一种新的自适应迭代FDE架构，用于MIMO系统，以对抗时变频率选择性衰落信道。迭代（Turbo）解码将与FDE结合以提高系统性能，其中码位上的软信息在均衡器和解码器之间迭代交换。线性和非线性迭代MIMO FDE结构都将得到发展。本文将研究两种自适应算法来跟踪信道变化。一种基于自适应信道估计，另一种不需要显式信道估计。特别提出了一种自适应半盲迭代MIMO FDE结构，这是一种非常新颖有效的方法，有助于节省宝贵的带宽和提高性能。随着无线通信市场的快速发展，高速、高质量、低成本的系统成为无线服务提供商的迫切需求。人们承认，技术创新将在实现这一目标方面发挥关键作用。所提出的自适应turbo启发迭代MIMO FDE系统具有高速、高性能、低成本和低复杂度的优点。它还允许在性能、复杂性和带宽效率方面进行广泛的权衡。基于密集的分析和数值结果，提出的研究将是未来（如4G）无线通信的一个有前途的解决方案。

Wireless communications have expanded enormously over the last decade. Indeed the latest prediction is that the growth will continue. Future wireless communication systems are expected to support high-speed and high-quality multimedia services. To increase the quality and capacity of wireless communications, Multiple-Input Multiple-Output (MIMO) systems have been proposed already to exploit signals from multiple antennas at both the transmitter and receiver. Even as a relatively new technique, MIMO has already been employed by the 3rd generation (3G) wireless standards in the form of space-time coding, and it is regarded as an essential component of the 4th generation (4G) and other future systems. However, the performance of MIMO systems deteriorates severely in frequency-selective fading channels, caused by the multi-path delay of the signal. Therefore, effective solutions are required for this difficult problem. To provide a high quality service with increasing demands on data rates within a restricted frequency bandwidth is a major challege. This proposal offers a number of ideas for investigations, which have the potential to overcome the shortcoming mentioned above. Moreover this offers low-complexity, which is an important issue from the point of view of power consumption, as well as high-performance, which is desired by the customers. Single carrier frequency domain equalization (FDE) has been shown to be an effective solution for frequency selective fading channels. In this research, a novel adaptive iterative FDE architecture will be investigated for MIMO systems, to combat time-varying frequency selective fading channels. Iterative (Turbo) decoding will be incorporated with FDE to improve the system performance, where the soft information on the code bits is exchanged between the equalizer and decoder iteratively. Both the linear and nonlinear iterative MIMO FDE structures will be developed. Two types of adaptive algorithms will be investigated to track the channel variations. One is based on adaptive channel estimation, and the other requires no explicit channel estimation. In particular, an adaptive semi-blind iterative MIMO FDE structure will be proposed, which is an extremely novel and effective method to help save the valuable bandwidth and improve the performance. With the rapid growth of the wireless communications market, the high speed, high quality and low cost systems are desired by the wireless service providers. It is acknowledged that technological innovation will play a key role in underpinning this goal. The proposed adaptive Turbo-inspired iterative MIMO FDE system has the advantages of high speed, high performance, low cost and low complexity. It also allows a wide range of tradeoffs on performance, complexity and bandwidth efficiency. Based on intensive analytical and numerical results, the proposed research will be a promising solution for the future (such as 4G) wireless communications.