Space Shift Keying (SSK) Modulation: On the Transmit-Diversity / Multiplexing Trade-Off

Space Shift Keying (SSK) is a low-complexity modulation scheme for multiple-antenna wireless systems. In this paper, we analyze the transmit-diversity/multiplexing trade-off of SSK modulation with the main objective of developing practical solutions to achieve transmit-diversity. More specifically, the contributions of this paper are as follows: i) we propose a practical scheme that achieves transmit-diversity equal to two for any number of antennas at the transmitter. The solution is based on the so-called Time-Orthogonal-Signal-Design (TOSD) principle introduced in [1], and adopts time-orthogonal shaping filters at the transmitter; ii) we show that the TOSD principle with orthogonal shaping filters can be applied to the so-called Generalized SSK (GSSK) modulation scheme in [2], and that a transmit-diversity equal to two can still be obtained while increasing the data rate with respect to SSK modulation; and iii) we propose a general encoding scheme that allows us to get transmit-diversity greater than two. The solution combines TOSD and GSSK principles in a unique fashion, and is flexible enough to accommodate various transmit-diversity gains by trading-off the number of transmit-antenna, the number of simultaneously-active transmit-antenna, and the achievable data rate. Furthermore, proposed methods and findings are substantiated via analysis and numerical simulations.