OTFS Signaling for SCMA With Coordinated Multi-Point Vehicle Communications

TL;DR

This paper proposes an OTFS-based SCMA system with CoMP for uplink vehicle communications, exploiting delay and Doppler diversity to improve performance in dynamic environments.

Contribution

It introduces a novel OTFS-based SCMA with CoMP system, along with ML detection and efficient algorithms, enhancing multi-user detection in high-mobility scenarios.

Findings

OBSCMA with CoMP outperforms existing solutions.

The proposed detectors are robust under channel uncertainty.

The system effectively exploits Doppler and spatial diversity.

Abstract

This paper investigates an uplink coordinated multi-point (CoMP) coverage scenario, in which multiple mobile users are grouped for sparse code multiple access (SCMA), and served by the remote radio head (RRH) in front of them and the RRH behind them simultaneously. We apply orthogonal time frequency space (OTFS) modulation for each user to exploit the degrees of freedom arising from both the delay and Doppler domains. As the signals received by the RRHs in front of and behind the users experience respectively positive and negative Doppler frequency shifts, our proposed OTFS-based SCMA (OBSCMA) with CoMP system can effectively harvest extra Doppler and spatial diversity for better performance. Based on maximum likelihood (ML) detector, we analyze the single-user average bit error rate (ABER) bound as the benchmark of the ABER performance for our proposed OBSCMA with CoMP system. We also develop a customized Gaussian approximation with expectation propagation (GAEP) algorithm for multi-user detection and propose efficient algorithm structures for centralized and decentralized detectors. Our proposed OBSCMA with CoMP system leads to stronger performance than the existing solutions. The proposed centralized and decentralized detectors exhibit effective reception and robustness under channel state information uncertainty.