Research on LDPC Decoder Design Methodology for Error-Correcting Performance and Energy-Efficiency

I-Abstract Low-Density Parity-Check (LDPC) codes, as linear block error-correcting codes (ECC), which were invented by Gallager in 1963 and rediscovered by MacKay in 1999, nowadays become a hot topic in a variety of application fields. Due to inherently paralleled decoding algorithm and near Shannon limit error-correcting performance, LDPC codes have been widely adopted in modern communication standards, such as Wi-Fi (IEEE 802.11n), WiMAX (IEEE 802.16e), WPAN (IEEE 802.15.3c) and the second-generation of digital video broadcasting (DVB-x2) family of standards. Moreover, storage systems and optical transmission systems also adopt them for improving the lifetime and reliability of devices or communication distances. LDPC codes can be decoded in time linear to their code-lengths by using iterative belief propagation (BP) or Two-Phase Message-Passing (TPMP) algorithm which was firstly invented by Gallager involving variable-node and check-node message-updating phases. The independence of calculations among variable-nodes or check-nodes in each phase enables arbitrary parallelism for parallel implementation of decoders. Fully-parallel decoders, in which all the variable-node and check-node processing units are implemented, can achieve the highest parallelism but usually suffer from extremely complicated placement and interconnection. A practical solution is the so-called partial-parallel implementation, in which both or either of variable-node and check-node phases are divided into groups and processed separately to trade-off hardware complexity. Structured LDPC codes such as IRA-(irregular repeat-accumulate) LDPC codes and QC-(quasi-cyclic) LDPC codes are invented for partial-parallel implementation and have been adopted in a variety of wireless/wired communication standards. On the other hand, for most of application cases, supporting multi-mode (multiple code-lengths and multiple code-rates) decoding in one single decoder is appreciated since the communication channel status may change at all times. However, previous decoders designed with TPMP algorithm largely depend on the codes' properties, Abstract-II-which makes the multi-mode decoding almost impossible. Due to the introduction of Layered decoding algorithm by Mansour in 2003, the development of LDPC decoders obtains a tremendous progress. It cannot only achieve up to twice convergence speed compared to traditional TPMP algorithm, but also provide practical solution for the multi-mode partial-parallel decoder architectures. The Layered algorithm applies the same check-node functions as TPMP algorithm but different variable-node message-passing schedule, which can increase the flexibility of decoder for multi-mode decoding. Actually, almost all the multi-mode decoders for modern wireless communication systems are designated based on the Layered algorithm. As multi-mode LDPC decoders, many works are developed from the multi-mode prototype designed by Mansour (JSSC 2006). Y. Sun …