Link-Adaptive Mapper Designs for Space-Shift-Keying-Modulated MIMO Systems

Abstract

This work focuses on the design and analysis of link-adaptive bits-to-antenna-indexes mapping for closed-loop space-shift keying (SSK)-modulated multiple-input multiple-output (MIMO) systems. With the aim of achieving a lower bit error rate (BER), optimal mappers are designed under different transmission conditions. Assuming that perfect channel state information (CSI) is available at the transceivers, an original binary switch algorithm (OBSA) is proposed. For the case in which there is no CSI at the transmitter and the feedback channel is bandwidth limited, a restricted binary switch algorithm (RBSA)-based mapping design is proposed. Both of the proposed algorithms can bring considerable performance gains but are of high computational complexity if there are a large number of transmit antennas. To overcome this, algorithms with reduced computational complexity are proposed and investigated, which are named partial OBSA and partial RBSA. The performance improvement brought by all of the proposed mapping schemes in terms of BER performance enhancement and signal-to-noise ratio (SNR) gain in a high-SNR regime is theoretically given. Simulations are done to validate the theoretical analysis, and results show that the proposed schemes can improve BER performance considerably in a wide range of SNR regimes. In addition, all of the proposed mapping schemes can cowork with those existing transmit processing techniques and bring additional performance gain without incurring any extra cost on physical components (e.g., additional phase shifters or power amplifiers). All these make the proposed mapping schemes promising choices for the link-adaptive design of closed-loop SSK MIMO systems.