Oblique projection: An interference mitigation for MIMO multihop full‐duplex relay

Abstract

Full-duplex (FD) assisted multiple-input-multiple-output relaying increases the spectral efficiency through efficient spectrum utilization. The major concerns for the FD assisted relay system are the cancellation of inter-relay interference (IRI) and relay self-interference (RSI). Previous works were idealized only on the basis of either RSI or IRI; hence, all other realistic models to overcome the RSI or IRI were unappreciated. This paper aims to reduce the interference-to-signal ratio. We propose the joint relay's receive beamforming based on oblique projection to mitigate the RSI and IRI in multihop environments. Applying first orthogonal projectors to the relay's received signal, the relay's received signals are divided into interference subspace and signal subspace. Then, the desired signal is recovered from signal subspace by using oblique projection that cancels out the RSI and IRI. The geometric interpretation of oblique projection is analyzed to understand its properties. The major merit of this method is that it can be adopted even when the RSI and IRI channels are unknown. In comparison to the existing interference cancellation methods, the signal-to-interference ratio of our proposed method does not deteriorate even when the transmit power is high. Additionally, we demonstrate that the oblique projection output is equivalent to an orthogonal projection using geometrical interpretation, simulation, and theoretical derivation.Trans Emerging Tel Tech. 2020;31:e3799.wileyonlinelibrary.com/journal/ett

Short-Packet URLLCs for Multihop MIMO Full-Duplex Relay Networks: Analytical and Deep-Learning-Based Real-Time Evaluation

“…The proof is concluded. APPENDIX B PROOF OF (12), (13), AND (14) By substituting (3) into (11), the average BLER at hop k for TAS/MRC is calculated as into (B.1), we obtain (12). The derivations of ( 13) and ( 14) can be demonstrated by using the same methods as those in (12).…”

“…The results revealed that distributing the interference rejection capability between both terminals performed better than letting either the transmitter or receiver remove the SLI and crosstalk interference. In [12], Madani et al proposed a joint-relay receive beamforming technique on oblique projections to mitigate residual SLI and inter-relay interference in multihop MIMO FDR environments. The results claimed that (i) the proposed methodology could be adopted, even when the residual SLI and inter-relay interference channels were unavailable; and (ii) the signal-to-interference-plus-noise ratio (SINR) would not deteriorate, even in the high transmit-power regime.…”

Interference Management in 5G and Beyond Network: Requirements, Challenges and Future Directions

“…Researchers worked on the mitigation of both interferences related to relay, i.e., IRI and RSI. Subsequently, in [136], authors investigated RSI and IRI for FDR. They are using oblique projection and orthogonal projector techniques to nullify relays interferences.…”

Short-Packet URLLCs for Multihop MIMO Full-Duplex Relay Networks: Analytical and Deep-Learning-Based Real-Time Evaluation

“…The results revealed that distributing the interference rejection capability between both terminals performed better than letting either the transmitter or receiver remove the SLI and crosstalk interference. In [11], Madani et al proposed a joint-relay receive beamforming technique on oblique projections to mitigate residual SLI and inter-relay interference in multihop MIMO FDR environments. The results claimed that (i) the proposed methodology could be adopted, even when the residual SLI and inter-relay interference channels were unavailable; and (ii) the signal-tointerference-plus-noise ratio (SINR) would not deteriorate, even in the high transmit-power regime.…”