Successive Decode-and-Forward Relaying With Privacy-Aware Interference Suppression

Abstract

Successive relaying holds the promise of achieving spatial diversity gain for single-antenna users while recovering the multiplexing loss due to the half-duplex relaying in B5G/6G. However, how to mitigate inter-relay interference (IRI) with privacy protection in low complexity remains open. In this paper, we present a successive decode-and-forward (DF) relaying protocol based on an analog network interference cancellation (NICE) method, which may suppress IRI, using linear processing without decoding the signals from the source. More specifically, a relay actively keeps receiving signals from the source, which are then used as prior knowledge to enable an amplify-and-cancel (AC) IRI mitigation strategy. The AC based IRI suppression is capable of improving high information privacy, because a relay does not need to know codebooks used by other relays and will not decode any signals intended for other relays. We obtain the closed-form expression of the minimum residual interference power, based on which the average throughput and the optimal diversity-multiplexing tradeoff (DMT) are presented. The DMT analysis along with simulations shows that the proposed method outperforms conventional two-timeslot half-duplex relaying in terms of the spectral efficiency. It also achieves lower complexity than CAO-SIR based on decode-and-cancel (DC) in [1] and lower IRI than the successive amplify-and-forward (AF) relaying in [2] .