Hybrid Codeword Position Index Modulation for Sparse Code Multiple Access System

TL;DR

This paper introduces HCPI-SCMA, a novel scheme that enhances transmission efficiency and error performance in sparse code multiple access systems by utilizing additional codeword position information and a modified detection algorithm.

Contribution

The paper proposes HCPI-SCMA, a new variation of CPI-SCMA that uses multiple index selectors and a modified MPA for improved efficiency and error rates.

Findings

Achieves higher transmission efficiency at high SNRs.

Provides better error rate performance compared to CPI-SCMA.

Outperforms conventional SCMA in high SNR regions.

Abstract

In this paper, a novel variation of codeword position index based sparse code multiple access (CPI-SCMA) system, which is termed as hybrid codeword position index modulated sparse code multiple access (HCPI-SCMA), is proposed to further improve the transmission efficiency (TE). In this scheme, unlike the conventional CPI-SCMA that uses only one kind of bits-toindices (BTI) mapper, the codeword positions which are padded with zeros in CPI-SCMA are also utilized to transmit additional information. Since multiple index selectors are used in a HCPISCMA codeword, the original message passing algorithm (MPA) no longer works in HCPI-SCMA; hence, a modified MPA is proposed to detect the received signals. It is shown in the simulations and analysis that the proposed scheme can achieve both higher TE and better error rate performance in the region of high signal-to-noise ratio (SNR) compare to the conventional SCMA (C-SCMA). Moreover, compared with CPI-SCMA, HCPISCMA can achieve higher TE with approximately the same error rate performance compared to CPI-SCMA at high SNRs.