Comparison of distributed LDPC coding schemes for decode-and-forward relay channels

Abstract

Abstract-In order to approach the theoretical limit of the decode-and-forward strategy for the half-duplex relay channel, distributed LDPC coding schemes have been proposed. In these schemes, the code applied at the source should be decodable at the relay to yield correct parity bits. With the help of the parity bits the destination should also be able to estimate the transmitted information correctly. For successful decoding the distributed coding scheme has to be designed jointly, requiring a high design complexity. As an alternative a distributed LDPC scheme based on puncturing is investigated, which requires only the design of one mother code. In this paper we compare three different approaches for designing distributed LDPC codes with respect to their performance and their design complexity.

Jointly optimized rate-compatible UEP-LDPC codes for half-duplex co-operative relay networks

“…The code design proposed here is different from the designs proposed in [3] and [6] because it provides UEP properties to the code, i.e., more important bits are made more protected by allocating them higher variable node degrees. The coding scheme in [6] has simple code design as it requires the design of only one single-user LDPC. In contrast to the coding scheme in [6], our proposed coding scheme requires the joint design of two codes.…”

“…Section 4 describes the selection of a good check node degree distribution and discusses the simulation results of our proposed code design. The results are also compared to the simulation results for QC-LDPC codes [9] as well as the codes proposed in [3] and [6]. Section 5 concludes this paper.…”

“…In [6], the authors have compared two different LDPC coding schemes from [7] and [8] with their proposed puncturing-based rate-compatible LDPC codes. The code design proposed here is different from the designs proposed in [3] and [6] because it provides UEP properties to the code, i.e., more important bits are made more protected by allocating them higher variable node degrees. The coding scheme in [6] has simple code design as it requires the design of only one single-user LDPC.…”

“…The coding scheme in [6] has simple code design as it requires the design of only one single-user LDPC. In contrast to the coding scheme in [6], our proposed coding scheme requires the joint design of two codes. However, our proposed code shows better performance than the code proposed in [6] because the code in [6] has performance loss due to puncturing in the co-operative relay network.…”

“…D concatenates w 1 withw e to get the extended codewordw 2 = [w 1we ] of length N 2 belonging to the extended code C 2 .w 2 is then decoded at D to recover the original information. From (2) and (3), it follows that the signals received at D in BC and MAC modes can be expressed respectively as y D1 = h SD P S1 w 1 + n D1 (6) y D2 = h RD P R w e + n D2 .…”