Self-interference in Multi-tap Channels for Full-Duplex Wireless Systems

Residual self-interference (SI) is primarily a key challenge when designing In-Band Full-duplex (IBFDX) wireless systems. Channel estimation errors are one of the major causes of residual SI. Consequently, a deeper understanding of the impact of the channel effects on the residual SI becomes indispensable. In this paper, we investigate the influence of multiple taps on the residual SI power of IBFDX systems. We first formulate the effect of having independent taps on the residual SI power mathematically. The derivations take into account the amount of interference cancellation on each tap by considering phase and amplitude estimation coefficients. We conclude that the increase in the number of taps always leads to an additive effect of the residual power. Such findings are shown mathematically and also reported in different results obtained by simulation. Finally, we compare the distribution of the residual SI power with different known distributions, concluding that Weibull and Gamma distributions are the closest ones in terms of accuracy. In-Band Full-Duplex communication Residual self-interference Independent fading taps channel.authorsversionpublishe

Distribution of the Residual Self-Interference Power in In-Band Full-Duplex Wireless Systems

This paper derives the distribution of the residual self-interference (SI) power in an analog post-mixer canceler adopted in a wireless in-band full-duplex communication system. We focus on the amount of uncanceled SI power due to SI channel estimation errors. Closed form expressions are provided for the distribution of the residual SI power when Rician and Rayleigh fading SI channels are considered. Moreover, the distribution of the residual SI power is derived for low and high channel gain dynamics, by considering the cases when the SI channel gain is time-invariant and time-variant. While for time-invariant channels the residual SI power is exponentially distributed, for time-variant channels the exponential distribution is not a valid assumption. Instead, the distribution of the residual SI power can be approximated by a product distribution. Several Monte Carlo simulation results show the influence of the channel dynamics on the distribution of the residual SI power. Finally, the accuracy of the theoretical approach is assessed through the comparison of numerical and simulated results, which confirm its effectiveness.publishe

In-Band Full-duplex Residual Self-interference Approximation in Multi-tap Delay Fading Channels

InfoCent-IoT (POCI-01-0145- FEDER-030433.Residual self-interference (SI) is primarily a key challenge when designing In-Band Full-duplex (IBFDX) wireless systems. Channel estimation errors are one of the major causes of the residual SI. The SI channel is composed by multiple fading taps which makes the characterization of the residual SI more challenging as multiple copies of the transmitted signal, with variable delays and gains, are eventually aggregated at the receiver. In this paper, we derive an approximation for the distribution of the residual SI power in multi-tap delay fading channels. In particular, we show that under specific conditions the multi-tap fading channel can be represented by a summation of non-identical independent gamma distributions. In a further step, we approximate the summation of the gamma distributions using the Welch-Satterthwaite equation, obtaining a closed form expression for the distribution of the residual SI power. The accuracy of the theoretical approach is evaluated through simulation results. The similarity comparison between simulated data and the proposed model indicates a high accuracy of the adopted approximation when considering low fading uncertainty associated to the taps and low estimation errors. On the other hand, the accuracy of the approximation slightly decreases for higher uncertainty fading scenarios and for higher estimation errors. However, as a final remark, we highlight that the results computed with the model are close to the simulated ones and for most of the applications the model's error can be negligible.publishe