Full-duplex amplify-and-forward relays with optimized transmission power under imperfect transceiver electronics

Abstract

In-band full-duplex (FD) relays are useful for extending coverage areas and increasing overall throughput in wireless networks. The main technical difficulty hindering their implementation and use is their inherent self-interference (SI), generated due to simultaneous in-band reception and forwarding. Efficient SI mitigation is a practical necessity, and the imperfections in transceiver electronics, from which power amplifier (PA) non-linearity is one of the most serious phenomena, have to be taken into account in order to not limit the performance of such techniques. The magnitude of the distortion introduced by the PA depends on the relay input back-off (IBO) whose optimization for alleviating the effect of PA non-linearity is the main research objective in this paper. In particular, although plain signal-to-noise ratio (SNR) at the destination obviously increases when the IBO decreases, increased transmit power also strengthens the non-linear distortion leading to decreasing overall signal-to-interference-plus-noise ratio (SINR). We develop expressions for bounding the optimal IBO setting that maximizes the SINR at the destination, considering all relevant hardware impairments and SI cancellation with I/Q imbalance compensation. We provide closed-form solutions for the soft-limiter PA model and numerical results for more general PA models. Finally, the derived IBO bounds are compared with the numerical maximization of the SINR and the minimization of the bit-error rate (BER) to demonstrate that the theoretical bound settings provide good approximations to the optimal one.

Amplify-and-forward relay identification using joint Tx/Rx I/Q imbalance-based device fingerprinting

“…1. We consider the asymmetric IQI model [15,22] in which the signal is affected by the Rx/Tx gain imbalance α rx /α tx and the Rx/Tx phase-shift imbalance θ rx /θ tx . Since the frequency-dependent IQI plays a minor role compared to the dominant effect caused by the frequency-independent IQI [23], the former is not considered in this model.…”

“…By using (32) instead of (30), we are able to quickly calculate the instantaneous detection probability for every fingerprint comparison, which may enable the timely adjustment of T in (23) for ensuring the desired detection performance. In summary, using the GLRT presented in (22) and 23, two fingerprints can be differentiated with the detection probability derived in (30) given a given false alarm rate. In practical implementation, the detection probability can be quickly computed using (32) instead of (30).…”

Performance Analysis of Full-Duplex Amplify-and-Forward Relay System with Hardware Impairments and Imperfect Self-Interference Cancellation

“…However, more e orts still need to be done to achieve better RSI suppression. Wireless relaying is an emerging technology which can be used to improve coverage, reliability, and spectrum efciency has recently become a hot research topic [1,[3][4][5][6][7][8][9][10][11][15][16][17]. It is also expected to be widely employed for the IoT networks to support machine-to-machine (M2M) communications, in which wireless relaying is an important application.…”

“…e paper derived the self-interference matrix at the relay and proposed beam-forming schemes to maximize the signal-tointerference-plus-noise power ratio (SINR), thus improving the system performance. e works [11,15] analyzed the impact of hardware impairment at the relay node on the system performance.…”

“…e above overview showed that the outage performance of the FD relay systems suffered an outage floor in the high SNR regime and optimal power allocation could be used to improve the system performance and avoid such outage floor. However, most previous studies have been done for the ideal hardware systems except those in [11,15,18]. ese works considered an additional impact of imperfect hardware but only at the relay node.…”