Uniquely Decodable Multi-Amplitude Sequence for Grant-Free Multiple-Access Adder Channels

Abstract

Grant-free multiple-access (GFMA) is a valuable research topic, since it can support multiuser transmission with low latency. This paper constructs novel uniquely-decodable multi-amplitude sequence (UDAS) sets for GFMA systems, which can provide high spectrum efficiency (SE) without additional redundancy. We give the definition of a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> -size UDAS set, and construct two kinds of UDAS sets based on cyclic and quasi-cyclic modes. Then, we propose an UDAS-based multi-dimensional bit interleaving coded modulation (MD-BICM) transceiver, with corresponding detection algorithms, i.e., a statistic of UDAS feature based active user detection algorithm (SoF-AUD) and a multiuser detection iteration decoding algorithm. In addition, the theoretical active user error rate (AUER) and Shannon limits of the proposed system are deduced. Simulation results show that our proposed system can simultaneously support four users with an AUER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> , under the condition that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E_b</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is 0 dB and the length of transmit block is larger than a specified value, e.g., 784, verifying the validity of the proposed UDAS sets.