Spatial modulation, a multiple-input multipleoutput (MIMO) technology which uses the antenna index to transmit part of the incoming data, is an attractive way to reduce the energy cost and transceiver complexity in future wireless networks. In particular, the recently proposed technique of distributed spatial modulation (DSM) for relay networks can lead to better spectral efficiency, as it allows the relays to transmit their own data while simultaneously relaying the data of the source. A new distributed spatial modulation protocol is introduced in this paper which achieves virtual full duplex (VFD) communication. In this protocol, the source and relays transmit their own data in every time slot; thus, the spectral efficiency is significantly improved compared to conventional DSM. Simulation results indicate that at high signal-to-noise ratio (SNR), the proposed protocol has similar bit error rate (BER) performance versus SNR-per-bit compared to the standard full duplex relaying protocol of successive relaying; however, in contrast to successive relaying, the relays are simultaneously transmitting their own data, which is received at the destination with an error rate similar to that of the source's data.

Spatial modulation, a multiple-input multipleoutput (MIMO) technology which uses the antenna index as an additional means of conveying information, is an emerging technology for modern wireless communications. In this paper, a new distributed version of spatial modulation is proposed which achieves virtual full-duplex communication (VFD-DSM), allowing the source to transmit new data while the relay set forwards the source's data in every time slot. Two maximum a posteriori (MAP) detection methods at the destination are proposed for this VFD-DSM protocol: one, called local MAP, is based on processing the signals received over each pair of consecutive time slots, while the other, called global MAP, is based on symbol-errorrate optimal detection over an entire frame of data. Simulation results for the proposed VFD-DSM protocol indicate that for source data detection at high signal-to-noise ratio (SNR), VFD-DSM with local MAP detection can provide a similar error rate performance to that of successive relaying, while providing a significant throughput advantage since the relays can forward the source transmissions while also transmitting their own data. Furthermore, the use of global MAP detection is shown to yield a further 1.8 dB improvement in source data error rate while still maintaining this throughput advantage.

Distributed spatial modulation (DSM) is a cooperative diversity protocol for a wireless network, whereby communication from a source to a destination is aided by multiple intermediate relays. The main advantage of the DSM protocol is that it provides distributed diversity to the source's transmission, while simultaneously allowing the relays to efficiently transmit their own data to the destination. In this paper, network coding is combined with DSM in order to increase the data rate of the source-to-destination link while maintaining the same diversity order of 2 for this data. Two methods of detection are proposed for implementation at the destination node: an error-aware maximum likelihood (ML) demodulator which is robust to demodulation errors at the relays, and a low-complexity suboptimal demodulator which assumes correct demodulation at the relays. The system bit error rate (BER) performance is measured under two different relay geometries. Simulation results show that for the same overall system throughput, the proposed network coded DSM protocol can increase the source-to-destination data rate by approximately 33.3% compared to the conventional DSM system, while still guaranteeing a similar BER as for DSM for both of the considered channel geometries.

In this paper, a novel cooperative diversity protocol based on the association of non-orthogonal multiple access (NOMA) and distributed spatial modulation (DSM) is introduced. In the proposed protocol, two source symbols are multiplexed in the power domain, while one source symbol obtains a diversity gain due to its being relayed according to the DSM principle; this doubles the data rate for the source-to-destination link as compared with conventional DSM. We propose two demodulators for use at the destination: an error-aware demodulator which is robust to demodulation errors at the relays, and a suboptimal demodulator which assumes error-free demodulation at the relays. Simulation results demonstrate that while the proposed protocol achieves a source data throughput equal to that of a full-duplex system, its BER performance also significantly outperforms the full-duplex relaying benchmarks of successive relaying and virtual full-duplex DSM.

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