Exploiting the Joint Sparsity for LDPC-Enhanced Delay-Doppler Multicarrier Modulation: A Parallel Belief Propagation-Based Approach

To support communications with extremely high mobility, both the delay-Doppler multicarrier (DDMC) modulation and low-density parity-check (LDPC) code can be adopted to enhance the reliability under doubly-selective channels. However, the detector and decoder for LDPC-DDMC systems are treated separately in prior investigations, which cannot fully exploit the joint sparsity brought by the delay-Doppler channel and parity-check matrix. To promote the performance and reduce the complexity further, the detector and decoder of LDPC-DDMC systems are connected in a factor graph as two modules in this letter. The parallel belief propagation (BP)-based approach is then proposed to establish the joint receiver design for LDPC-DDMC systems with low complexity. Simulation results verify that the proposed scheme enjoys better bit-error-rate (BER) performance compared with the separate design.