A Survey on LDPC Codes and Decoders for OFDM-based UWB Systems

Abstract

Current UWB systems apply convolutional codes as their channel coding scheme. For next generation systems LDPC codes are in discussion due to their outstanding communications performance. LDPC codes are already utilized in the new WiMax and WiFi standards. Thus it is reasonable to investigate these codes as candidate LDPC codes for UWB. In this paper the authors present an implementation complexity and performance comparison of LDPC decoders. We will show that it is of great advantage to design new LDPC codes which are tailored to the special latency and throughput constraints of upcoming UWB systems. This new class of LDPC codes is named ultra-sparse LDPC codes. Synthesis results of WiMax, WiFi, and U-S LDPC decoders are presented based on an enhanced 65 nm CMOS process. We show that the implementation complexity of the new U-S LDPC decoders is 55% smaller, utilizing only 0.2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> instead of over 0.4 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , while the communications performance of all observed LDPC codes are almost identical under all the considered UWB simulation conditions.