Partially Informed Transmitter-Based Space Shift Keying

Abstract

In this paper, we propose a space shift keying (SSK) modulation scheme where a transmitter (Tx) has partial information of the channel states through feedback from the receiver. More specifically, the Tx does not receive perfect information of the channel coefficients, but only has information about channel gains ordering. This information is exploited by Tx to adapt the spatial constellation and transmit power weights. Thus, gray encoding based adapted spatial constellation decreases the number of bits in error between two consecutive constellation points and also reduces the average bit error rate (ABER). For mathematical analysis, we focus on a 2 × 1 multiple-input single-output (MISO) system over Rayleigh fading channels. An accurate expression of the ABER for the considered MISO system is derived. The proposed scheme outperforms the conventional SSK scheme for a given transmission rate, as demonstrated by both analysis and simulation. It is shown analytically that the ABER performance of the proposed SSK scheme can be improved by applying asymmetric power allocation (PA) to make links more distinguishable. Moreover, the proposed SSK scheme achieves a higher diversity order, as compared to the conventional SSK scheme; due to asymmetric PA. For a 4 × 1 MISO system, we present simulation based results of ABER performance for the proposed SSK scheme. Further, all analytical results are verified via simulation.