In-band full-duplex transmission allows a relay station to theoreticallydouble its spectral efficiency by simultaneously receiving and transmitting inthe same frequency band, when compared to the traditional half-duplex orout-of-band full-duplex counterpart. Consequently, the inducedself-interference suffered by the relay may reach considerable power levels,which decreases the signal-to-interference-plus-noise ratio (SINR) in adecode-and-forward (DF) relay, leading to a degradation of the relayperformance. This paper presents a technique to cope with the problem ofself-interference in broadband multiple-input multiple-output (MIMO) relays.The proposed method uses a time-domain cancellation in a DF relay, where areplica of the interfering signal is created with the help of a recursive leastsquares (RLS) algorithm that estimates the interference frequency-selectivechannel. Its convergence mean time is shown to be negligible by simulationresults, when compared to the length of a typical orthogonal-frequency divisionmultiplexing (OFDM) sequences. Moreover, the bit-error-rate (BER) and the SINRin a OFDM transmission are evaluated, confirming that the proposed methodextends significantly the range of self-interference power to which the relayis resilient to, when compared with other mitigation schemes.
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