Low Density Parity Check Codes and Turbo Codes for Wireless Communication

随着二十一世纪的到来，新的无线服务正在被部署，还有更多的服务正在被设想。为了提供这些服务，未来的无线系统应该能够处理比现在系统高得多的数据速率。可用于这些业务的有限频谱意味着未来系统的频谱效率必须显著提高。除了频谱效率外，下一代无线系统还必须节能。较低的发射功率意味着对其他用户的干扰较小，频谱可以更好地重用，从而提高整个网络的效率。无线信道对传输的信号有几种损害，使通信链路的质量恶化。在存在这种不可靠链路的情况下提高功率和频谱效率是一项具有挑战性的任务，使用有效的编码和信号处理技术可以大大促进这一任务。本研究探讨了强大的编码技术，如涡轮码和低密度奇偶校验码的设计，以提高无线系统的功率和频谱效率。本研究详细研究了在无线环境中使用的具有低解码复杂度的涡轮式码和低密度奇偶校验码（LDPC）的设计和性能分析。详细介绍的具体领域是用于多径信道和turbo均衡的编码方案的设计，用于频谱高效调制的LDPC码的设计，以及用于非平稳环境的使用LDPC码的增量冗余方案的设计。这项工作与现有工作的不同之处在于，它研究了几种新颖的编码技术，并专注于与所使用的迭代解码算法匹配的编码设计，而不是基于假设最大似然解码的编码设计。

As the twenty-first century unfolds, new wireless services are being deployed and several more are envisioned. In order to provide these services, future wireless systems should be capable of handling much higher data rates than today's systems. The limited spectrum available for these services implies that the spectral efficiency of future systems will have to be significantly higher. In addition to being spectrally efficient, next-generation wireless systems will have to be power efficient. Lower transmit powers means lesser interference to other users, better reuse of the spectrum and, hence, higher efficiency for the overall network. Wireless channels offer several impairments to the transmitted signals, deteriorating the quality of the communication link. Increasing the power and spectral efficiency in the presence of such an unreliablelink is a challenging task which can be greatly facilitated by the use of efficient coding and signal processing techniques. This research investigates the design of powerful coding techniques such as turbo codes and low density parity check codes for increasing the power and spectral efficiency of wireless systems.This research involves a detailed study of the design and performance analysis of turbo-like codes with low decoding complexity, and low density parity check codes (LDPC) for use in a wireless environment. Specific areas covered in detail are the design of coding schemes for use with multipath channels and turbo equalization, the design of LDPC codes for spectrally efficient modulation, and the design of incremental redundancy schemes using LDPC codes for use in a non-stationary environment. This work differs from the existing work in that it studies several novel coding techniques and concentrates on the design of codes matched to the iterative decoding algorithm being used, rather than the design of codes based on hypotheticalmaximum-likelihood decoding.