Spatial-Modulated Physical-Layer Network Coding Based on Block Markov Superposition Transmission for Maritime Relay Communications

As an alternative to satellite communications,multi-hop relay networks can be deployed for maritime long-distance communications.Distinct from terrestrial environment,marine radio signals are affected by many factors,e.g.,weather conditions,evaporation ducting,and ship rocking caused by waves.To ensure the data transmission reliability,the block Markov superposition transmission(BMST)codes,which are easily configurable and have predictable performance,are applied in this study.Meanwhile,the physical-layer network coding(PNC)scheme with spatial modulation(SM)is adopted to improve the spectrum utilization.For the BMST-SMPNC system,we propose an iterative algorithm,which utilizes the channel observations and the a priori information from BMST decoder,to compute the soft information corresponding to the XORed bits constructed by the relay node.The results indicate that the proposed scheme outperforms the convolutional coded SM-PNC over fast-fading Rician channels.Especially,the performance can be easily improved in high spatial correlation maritime channel by increasing the memory m.

Block Markov superposition transmission of LDPC codes

In this paper,based on the block Markov superposition transmission(BMST)technique,we present a new class of coupled low-density parity-check(LDPC)codes for the transport block(TB)-based transmission to improve the error-correcting performance.For encoding,the previous LDPC codewords corresponding to a TB(at prior time slot)are interleaved and superimposed onto the current LDPC codewords,resulting in the transmitted codewords.For decoding,the sliding window decoding algorithm with sum-product or min-sum implementations can be employed,inheriting a relatively low-latency decoding.A distinguished advantage of the proposed coded transmission over spatially coupled LDPC(SC-LDPC)codes is that the encoder/decoder of the proposed codes can be designed by reusing the encoder/decoder architecture of component block LDPC codes.To analyze the waterfall performance of BMST-LDPC code ensembles,we present the protograph-based EXIT chart analysis,which can efficiently predict the error-correcting performance in waterfall region.To analyze the error-floor performance of BMST-LDPC codes,we employ the genie-aided(GA)lower bound,which can efficiently predict the error-correcting performance in error-floor region.For ease of implementation,the BMST-LDPC codes are constructed by taking the(2,4)-raptor-like LDPC codes or the 5G LDPC codes as the basic components.The numerical results reveal that the proposed codes can have capacity-approaching performance,exhibiting a gap of 0.007 dB away from the corresponding Shannon limit.They also reveal that,by using the proposed BMST construction,the error-correcting performance of the original 5G block LDPC codes can be significantly improved,achieving coding gains up to one dB over the AWGN channels and two dB over the fast fading channels.

Improving Performance of LDPC-Coded Links via Partial Superposition Retransmission

In this paper,we propose a transmission scheme for uplink and downlink transmissions,where the fifth generation(5G)low-density parity-check(LDPC)codes are implemented for error correction.In the proposed scheme,the acknowledgment(ACK)or negative acknowledgment(NACK)feedback information is transmitted along with the payload data by cyclically shifting coded sequence,while the re-transmitted codewords are superimposed(XORed)partially on the current codewords.The distinguished feature of the proposed transmission scheme is that it requires neither extra transmission bandwidth nor extra transmission power.We also propose to truncate the error patterns for the purpose of reducing the implementation complexity and reducing the error propagation.Numerical results show that the proposed scheme significantly outperforms conventional LDPC-coded transmission.For the 5G LDPC code with length 1920 at the signal-to-noise ratio(SNR)of 1.3 dB,the word error rate(WER)of the data transmitted by the proposed scheme is about 10^(−4),while that of the conventional LDPC-coded transmission is about 10^(−2).