Single-RF and Twin-RF Spatial Modulation for an Arbitrary Number of Transmit Antennas

Spatial modulation (SM) constitutes an appealing low-complexity single radio frequency (RF) aided multiple-input multiple-output technique. Conventional SM schemes tend to rely on transmit antenna (TA) configurations, where the number of TAs is a power of two. In order to circumvent this limitation, a novel single RF-aided SM conceived for an arbitrary number of TAs (SM-ATA) is proposed, which is then further developed to a twin-RF enhanced SM-ATA (ESM-ATA) schedule for exploiting the diversity advantage of space-time block coding. Furthermore, low-complexity near-optimal detectors are designed for both the SM-ATA and ESM-ATA schemes. Our simulation results show that the proposed SM-ATA schemes offer almost the same performance as conventional SM systems, despite using a reduced number of TAs at the same transmission rate. The proposed twin-RF ESM-ATA schemes provide a beneficial performance gain over the existing twin-RF multiplexing based and space-time coding based SM schemes. Finally, an upper bound is derived for the average bit error probability, which is confirmed by our simulation results.