Amplify-forward and decode-forward cooperation relying on systematic Luby transform coded Hybrid Automatic-Repeat-reQuest

Abstract

Systematic Luby transform (SLT) codes constitute rateless codes, which are capable of adaptively adjusting their code rate depending on the channel quality without any explicit channel state information (CSI) at the transmitters. SLTs are also suitable for space time collaboration-aided relay networks. In this study, an iterative decoding-aided SLT scheme is combined with 16 quadrature amplitude modulation (QAM) transmission in a wireless relay-aided network. The bit error ratio (BER) results and extrinsic information transfer (EXIT) charts are provided to evaluate the performance of the proposed scheme. The simulation results show that the proposed scheme using amplify-and-forward (AF) relaying achieves a 2.5 dB gain at a BER of 10 25 , while the attainable improvement is nearly 6 dB for decode-and-forward (DF) relaying, compared to the noniterative detection scheme operating without the relay's assistance. Moreover, the AF relaying-aided SLT coded 16-QAM scheme is more beneficial, when the relay station is close to the source. By contrast, the DF relaying performs best near the mid-point between the source and the destination. Additionally, a modified Hybrid Automatic-Repeat-reQuest (HARQ) protocol using incremental redundancy is applied along with the SLT-coded 16-QAM scheme in order to enhance the achievable throughput and energy efficiency of cooperative networks. This arrangement reduces the total transmit power by about 5%, compared to the classic HARQ scheme.

Hybrid Automatic-Repeat-reQuest Systems for Cooperative Wireless Communications

“…20. schemes remained significantly below those of the first group. The third group contained Scheme 8 and Scheme 9, whose EXIT functions remained further below those of Schemes {4, 5,6,7} in Fig. 2.14. They achieved the BER of 10 −4 around the E b /N 0 value of 5.5 dB.…”

“…To reflect the rate of change in the channel, the so-called (maximum) Doppler frequency f D is specified based on the velocity v of the MS and the carrier frequency f c as 6) where λ denotes the wavelength, while c represents the speed of light.…”

“…The thesis is based on 8 publications and 4 submitted papers, which [1][2][3][4][5][6][7][8][42][43][44][45] cover the following novel aspects.…”

“…• In Section 3.4 we conceive a novel system based on the concatenation of SLT codes and 16-QAM [2,4,6], where the decoder and the demodulator iteratively exchange extrinsic information, as detailed in Section 3. 4.1.…”

“…Briefly, the encoding matrices have to satisfy the orthogonal property, which may be mathematically represented as 6) where c is a constant, while I n T represents an (n T × n T ) identity matrix.…”