A new construction for low density parity check convolutional codes

Low density parity check (LDPC) block codes have been shown to achieve near capacity performance for binary transmission over noisy channels. Block codes, however, require splitting the data to be transmitted into frames, which can be a disadvantage in some applications. Convolutional codes, on the other hand, have no such requirement, and are well suited for continuous transmission. Felstrom and Zigangirov (1999) proposed the construction of periodic time-varying convolutional codes with LDPC matrices. A set of time-invariant LDPC convolutional codes was described by Sridharan et al. (2002). The codes of Felstrom and Zigangirov were obtained by random construction techniques whereas those of Sridharan et al. were essentially algebraic constructions. The new LDPC convolutional codes described here are obtained by introducing a degree of randomness into the latter construction.