Multiple-Input Multiple-Output OFDM with Index Modulation: Low-Complexity Detector Design

Abstract

Multiple-input multiple-output orthogonal frequency division multiplexing with index modulation (MIMO-OFDMIM), which provides a flexible trade-off between spectral efficiency and error performance, is recently proposed as a promising transmission technique for energy-efficient 5G wireless communications systems. However, due to the dependence of subcarrier symbols within each sub block and the strong inter-channel interference, it is challenging to detect the transmitted data effectively while imposing low computational burden to the receiver. In this paper, we propose two types of low-complexity detectors based on the sequential Monte Carlo (SMC) theory for the detection of MIMO-OFDM-IM signals. The first detector draws samples independently at the sub block level while the second detector draws samples at the subcarrier level with further reduced complexity. To meet the constraint of the subcarrier combinations within each sub block, the second detector is further coupled with a carefully designed legality examination method. Attributed to the effectiveness of legality examination and deterministic SMC sampling, both proposed detectors achieve near-optimal error performance for the MIMO-OFDM-IM system.

Existing System

Spatial Multiplexing, Spatial Modulation.

Proposed System

In this paper, in order to achieve near-optimal error performance while maintaining low computational complexity, two types of detection algorithms based on the sequential Monte Carlo (SMC) theory are proposed for MIMO-OFDM-IM. By regarding each OFDM-IM subblock as a super modulated symbol drawn from a large finite set, the first type of detector draws samples independently at the subblock level. Although it is capable of achieving near-optimal performance with substantially reduced complexity, its decoding complexity can be still unsatisfactory when the size of the OFDM-IM subblock grows much larger. To further reduce the complexity, the second type of detector is proposed to draw samples subcarrier wise from the modified constellation with a much smaller size. To meet the constraint on the legal active subcarrier combinations within each OFDM-IM subblock, the second type of detector is coupled with a carefully designed examination method to avoid illegal samples. The effectiveness of the deterministic SMC sampling and legality examination, it only suffers from a marginal error performance loss. Finally, computer simulation and numerical results in terms of BER and number of complex multiplications (NCM) corroborate the superiority of both proposed detection methods.

Architecture

Block diagram of MIMO-OFDM-IM transmitter

Block diagram of MIMO-OFDM-IM receiver