An Adaptive Self-Interference Cancelation/Utilization and ICA-Assisted Semi-Blind Full-Duplex Relay System for LLHR IoT

Abstract

In this article, we propose a semi-blind full-duplex (FD) amplify-and-forward (AF) relay system with adaptive self-interference (SI) processing assisted by independent component analysis (ICA) for low-latency and high-reliability (LLHR) Internet of Things (IoT). The SI at FD relay is not necessarily canceled as much as possible like the conventional approaches, but is canceled or utilized based on a signal-to-residual-SI ratio (SRSIR) threshold at relay. According to the selected SI processing mode at relay, an ICA-based adaptive semi-blind scheme is proposed for signal separation and detection at destination. The proposed FD relay system not only features reduced signal processing cost of SI cancelation but also achieves a much higher degree of freedom in signal detection. The resulting bit error rate (BER) performance is robust against a wide range of SRSIR, much better than that of conventional FD systems, and close to the ideal case with perfect channel state information (CSI) and perfect SI cancelation. The proposed system also requires negligible spectral overhead as only a nonredundant precoding is needed for ambiguity elimination in ICA. In addition, the proposed system enables full resource utilization with consecutive data transmission at all time and same frequency, leading to much higher throughput and energy efficiency than the time-splitting and power-splitting-based self-energy recycling approaches that utilize only partial resources. Furthermore, an intensive analysis is provided, where the SRSIR thresholds for the adaptive SI H. Duan and Y. Jiang are with the

Toward URLLC: A Full Duplex Relay System with Self-Interference Utilization or Cancellation

“…In order to achieve the goal of URLLC, digital SI cancellation can be processed at base station rather than at relay [10][11][12]. The main reasons can be listed as follows:…”

“…In other words, the SI consists of summing up all previous OFDM symbols, if the residual SI is not cancelled at relay. However, the power of the residual SI consecutively fades exponentially with the number of transmitted OFDM symbols in the past, as the residual SI channel gain is relatively low [10][11][12], with the line-of-sight component being mitigated by analog cancellation. Therefore, the current OFDM symbol is only interfered with a small number of previously successive OFDM symbols [10][11][12] that take a significant part in the SI power.…”

“…However, the power of the residual SI consecutively fades exponentially with the number of transmitted OFDM symbols in the past, as the residual SI channel gain is relatively low [10][11][12], with the line-of-sight component being mitigated by analog cancellation. Therefore, the current OFDM symbol is only interfered with a small number of previously successive OFDM symbols [10][11][12] that take a significant part in the SI power. The residual SI power of the other left OFDM symbols is too low, and can be treated as noise [10][11][12].…”

“…Therefore, the current OFDM symbol is only interfered with a small number of previously successive OFDM symbols [10][11][12] that take a significant part in the SI power. The residual SI power of the other left OFDM symbols is too low, and can be treated as noise [10][11][12].…”

“…The equalized SI is a replica of previous OFDM symbols, and is utilized to combine with the equalized signal in previous OFDM symbols to maximize the desired signal power for enhancement of degree of freedom in signal processing as well as reliability improvement. It has been shown that up to 10 dB signal power enhancement can be yielded [10]. The procedure of SI utilization is described as follows:…”