The design of a high-speed decoder using traditional partly parallel architecture for Non-Quasi-Cyclic(NQC) Low-Density Parity-Check(LDPC) codes is a challenging problem due to its high memory-block cost and low hardware utilization efficiency. In this paper, we present efficient hardware implementation schemes for NQCLDPC codes. First, we propose an implementation-oriented construction scheme for NQC-LDPC codes to avoid memory-access conflict in the partly parallel decoder. Then, we propose a Modified Overlapped Message-Passing(MOMP) algorithm for the hardware implementation of NQC-LDPC codes. This algorithm doubles the hardware utilization efficiency and supports a higher degree of parallelism than that used in the Overlapped Message Passing(OMP) technique proposed in previous works. We also present single-core and multi-core decoder architectures in the proposed MOMP algorithm to reduce memory cost and improve circuit efficiency. Moreover, we introduce a technique called the cycle bus to further reduce the number of block RAMs in multi-core decoders. Using numerical examples, we show that, for a rate-2/3, length-15360 NQC-LDPC code with 8.43-d B coding gain for Binary PhaseShift Keying(BPSK) in an Additive White Gaussian Noise(AWGN) channel, the decoder with the proposed scheme achieves a 23.8%–52.6% reduction in logic utilization per Mbps and a 29.0%–90.0% reduction in message-memory bits per Mbps.
This paper investigates the social-aware cooperation(SAC) among mobile terminals(MTs), motivated by the fact that modern smart devices have much improved context awareness. Aware of the social ties, the cooperative network contains two layers of property: social and physical. In order to observe how the social awareness benefit the cooperation performance, we first formulate the social ties between MTs into parameters that can describe the cooperative behaviors by taking the mobility feature into account, defined as the conviction-approval-suspicion(CAS) model. Limited by the processing capability, partner selection is of great practical significance. To this end, the social-aware partner selection strategy is analyzed, and a significant superiority is observed compared to social-unaware selection. By analyzing the cooperative throughput, an explicit relationship between the degrees-of-freedom gain and the social-physical property is finally derived. Simulation results validate the theoretical analysis.
In this study,a class of Generalized Low-Density Parity-Check(GLDPC) codes is designed for data transmission over a Partial-Band Jamming(PBJ) environment. The GLDPC codes are constructed by replacing parity-check code constraints with those of nonsystematic Bose-Chaudhuri-Hocquenghem(BCH),referred to as Low-Density Parity-Check(LDPC)-BCH codes. The rate of an LDPC-BCH code is adjusted by selecting the transmission length of the nonsystematic BCH code,and a low-complexity decoding algorithm based on messagepassing is presented that employs A Posteriori Probability(APP) fast BCH transform for decoding the BCH check nodes at each decoding iteration. Simulation results show that the LDPC-BCH codes with a code rate of 1/8.5have a bit error rate performance of 1 10 6at signal-noise-ratios of 6.97 dB,4.63 dB,and 2.48 dB when the fractions of the band jammed are 30%,50%,and 70%,respectively.
The scheduling efficiency of the tracking and data relay satellite system(TDRSS)is strictly limited by the scheduling degrees of freedom(DoF),including time DoF defined by jobs' flexible time windows and spatial DoF brought by multiple servable tracking and data relay satellites(TDRSs).In this paper,ageneralized multiple time windows(GMTW)model is proposed to fully exploit the time and spatial DoF.Then,the improvements of service capability and job-completion probability based on the GMTW are theoretically proved.Further,an asymmetric path-relinking(APR)based heuristic job scheduling framework is presented to maximize the usage of DoF provided by the GMTW.Simulation results show that by using our proposal 11%improvement of average jobcompletion probability can be obtained.Meanwhile,the computing time of the time-to-target can be shorten to 1/9 of the GRASP.
