Search

A random access framework based on random interleaving multiplexing (RIM) is proposed to further improve throughput for internet of things in satellite networks, which resort to the state-of-art physical layer techniques that can resolve multiple packet collisions issue. The interleavers are randomly selected by active devices from a set of available interleavers, which are used to differentiate signals of different devices sharing a subframe that consists of multiple time slots. The message passing detector (MPD) is utilized to decode collided packets. By means of transmission diversity and interference cancellation, the proposed scheme can be linked with the irregular repetition slotted ALOHA (IRSA), the RIM-IRSA protocol is proposed. The analysis of packet loss ratio (PLR) of the RIM-IRSA is given by using the density evolution method, and the optimal degree distributions are given. Simulation results show that the RIM-IRSA outperforms traditional IRSA protocol.

Due to limited radio resources, non-orthogonal multiple\ud access (NOMA) is a promising technology to enable massive\ud connectivity in future 5G and beyond wireless networks. However,\ud it suffers from the multiple access interference (MAI), which\ud usually requires a high detection complexity to mitigate. In this\ud paper, we consider NOMA with sparse multiple-access sequences,\ud so as to leverage the message passing algorithm (MPA) for lowcomplexity and high-reliability multiuser detection. The optimal\ud sparsity of spreading sequences is analyzed by minimizing the\ud average bit error rate (BER) in the asymptotic large-system limit.\ud Based on the analysis, the optimal sparse sequences that optimize\ud the performance of MPA detector are designed in a systematically\ud hierarchical way. The sparse structure is constructed given the\ud target girth. Then, the values of nonzero entries are determined\ud to maximize the minimum distance. The detection performance\ud of the designed sparse sequences is presented for both additive\ud white Gaussian noise (AWGN) and Rayleigh fading channels.\ud Simulation results show the superiority of the proposed design\ud in comparison with existing schemes.\ud

Spatial modulation (SM) sparse codemultiple access (SCMA) systems provide high spectral efficiency (SE) at the expense of using a high number of transmit antennas. To overcome this drawback, this paper proposes a novel SM-SCMA system operating in uplink transmission, referred to as rotational generalized SM-SCMA (RGSM-SCMA). For the proposed system, the following are introduced, first, transmitter design and its formulation, second, maximum likelihood and maximum a posteriori probability decoders, and finally, practical low-complexitymessage passing algorithm and its complexity analysis. Simulation results and complexity analysis showthat the proposed RGSM-SCMA system delivers the same SE with significant savings in the number of transmit antennas, at the expense of close bit error rate and a negligible increase in the decoding complexity, when compared with SM-SCMA., Natural Sciences and Engineering Research Council of Canada (NSERC); Turkish Academy of Sciences (TÜBA), GEBIP Programme