Improved BCH-Polar Concatenated Scheme for Unsourced Random Access in Internet of Things

In this article, an improved Bose-Chaudhuri-Hocquenghem (BCH)-Polar concatenated unsourced random-access coding scheme is considered for the Internet of Things system. At each active user side, a concatenated random-access code is used, where the outer code is denoted as a BCH-based T-fold code, which is constructed by using the parity-check matrix of a BCH code to distinguish no more than T user packets, and a polar code is used as the inner code. At the receiver side, a novel T-fold aided successive-cancelation list (TA-SCL) decoding approach is proposed that exploits the information transferred between the inner- and outer-decoding of the BCH-Polar concatenated random-access code. The TA-SCL decoding approach resorts to indicators of the T-fold decoding to aid in the survival path selection of the successive cancelation list (SCL) decoding for the polar code. Within the Berlekamp-Massey algorithm (BMA) decoding procedure of the T-fold code, its input, whether it is in an error-free case or contains more than T users or not, can be determined by its output indicators. Therefore, these indicators of the outer BMA can play a genius role in the last-survival path selection for the inner SCL decoding. Simulation results show that, compared with the traditional method, the proposed TA-SCL decoding approach can improve the $E_{b}/N_{0}$ performance for the BCH-Polar concatenated scheme in the uncoordinated Gaussian multiple-access channel by about 1 dB with the computational complexity cost times increased by much more less than the size of SCL list.