A Direct-Code To Increase The Spectral Efficiency Of Generalized Space Shift Keying Modulation

In conventional space shift keying (SSK) and generalized SSK (GSSK), the symbols are transmitted only by the active antennas indices, while the inactive antennas remain unexploited; this limits the spectral efficiency. In order to combat this limitation, we propose a direct-code for SSK (DC-SSK) modulation technique. In DC-SSK, the transmitter is allowed to use 0, 1,..., N-t antennas for each symbol, and groups of Nt bits are used to derive the transmitting antennas directly according to the bit value, active for '1' and inactive for '0'. DC-SSK improves the spectral efficiency by exploiting the indices of both the active and inactive antennas to convey the information. The analysis shows that the data rate of DC-SSK increases linearly with the number of transmitting antennas, while the data rate of conventional SSK increases as a base-2 logarithm. To keep the transmit side simple, we propose an on-off keying modulation, instead of generalized QAM. We analyze the performance of the proposed solution and validate the results by simulation. The results show that the DC-SSK is a promising solution for the next generation of wireless communications, as a response to the massive demand for increased data rates.