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 (MIMO) 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 (STBC). 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 transmit antennas 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 (ABEP), which is confirmed by our simulation results