ODMA-based MIMO Massive Unsourced Random Access with Soft-Output Polar Codes
Information Theory
Summary
The authors study a way to improve how devices communicate in a busy wireless system using multiple antennas, called MIMO massive unsourced random access. They propose a new coding and detection method under the on-off division multiple access (ODMA) framework that splits transmissions into segments to reduce errors without adding overhead. Their approach combines pattern detection and data decoding by using extra information from a special polar code decoder to make communication more accurate. The proposed method also lowers computational effort while boosting performance, as shown by their simulation results.
Authors
Tianya Li, Xiaoran Zhang, Nan Hu, Yongpeng Wu, Wenjun Zhang, Xiang-Gen Xia, Chengshan Xiao
Abstract
This paper investigates the design of the on-off division multiple access (ODMA) transmission scheme for multiple-input multiple-output (MIMO) massive unsourced random access (URA) systems with soft-output (SO) polar codes. First, a three-segment pilot-uncoupled coding scheme is introduced under the ODMA framework, which reduces the coding rate of the data segment without increasing the transmission overhead, improving the overall system performance. Building upon this architecture, a hierarchical pattern detection framework is developed. Specifically, a coarse-grained candidate set of transmission patterns is first identified through correlation operations. Based on this, a message-passing (MP)-based pattern detection algorithm is developed to iteratively estimate the posterior probabilities of transmission patterns, followed by the \textit{maximum a posteriori} (MAP) estimation to obtain the precise pattern detection result. Furthermore, a joint pattern detection and data decoding algorithm based on the bit-wise SO information of polar decoder is investigated, where the posterior probability information provided by the polar decoder is exploited to refine the pattern detection and contribute to an improved accuracy. In addition, by leveraging bit-wise SO information of the successive cancellation list polar decoder, an MP-based iterative decoding algorithm is developed to significantly enhance the decoding performance. The proposed scheme simultaneously exploits the transmission gain of uncoupled-ODMA framework, the coding gain of polar codes in the short-blocklength regime, and the iterative decoding gain enabled by SO information, while the computational complexity is significantly reduced through the hierarchical detection framework. Simulation results demonstrate that the proposed scheme achieves strong robustness ...