Full Duplex Radios

Abstract

Full duplex communication has been well explored in the past decade, with several physical layer designs proposed for effectively doubling the throughput of mobile devices. However, these systems are far from being well-deployed in the Wi-Fi and cellular applications, where most of the research has been done. In this paper, we investigate some of the fundamental pragmatic challenges in deploying full duplex that explain the reluctance from industry players in deploying this feature in commercial end-user devices and base stations at a large scale. Upon doing so, we identify that the problems lie not quite at the radio layer-but at layers below and above it. At the hardware layer, we find that the power and complexity of IC-implementations of full duplex far exceeds that of other existing technologies that achieve similar throughput gain, such as multiuser MIMO. We further identified how higher-layer cellular and Wi-Fi traffic patterns and MAC protocols are fundamentally ill-suited to the full duplex paradigm. We report empirical analysis from the power consumption of an IC-implementation of a full duplex cancellation circuit, demonstrating that full duplex cancellation circuitry would consume at least 57% more power than a MIMO system achieving identical throughput gains. We also show how current traffic patterns reduce the benefits of full duplex to 1.25× instead of the expected 2×. CCS CONCEPTS • Networks → Network performance analysis; Network components; • Theory of computation → Circuit complexity; • Hardware → Integrated circuits; Circuits power issues.

Impacts of Nonlinear Energy Harvesting and Residual Self-Interference on the Performance of Full-Duplex Decode-and-Forward Relay System

“…Specifically, several solutions in antenna domain such as cross-polarization, antenna directionality, and isolation are used first. Thanks to the usage of separate antennas, these solutions in the antenna domain can effectively reduce the SI power up to 30 dB [8], [9]. Then, the SI suppression in analog and digital domains is carried out by using suitable circuits and algorithms.…”

“…Then, the SI suppression in analog and digital domains is carried out by using suitable circuits and algorithms. These techniques can mitigate SI up to 50 dB in the analog domain and 60 dB in the digital domain [8], [33], [34]. Overall, after applying all SIC methods, FD devices can cancel the SI up to 110 dB [8], [33], [34], making FD communication systems become feasibly in realistic scenarios.…”

“…These techniques can mitigate SI up to 50 dB in the analog domain and 60 dB in the digital domain [8], [33], [34]. Overall, after applying all SIC methods, FD devices can cancel the SI up to 110 dB [8], [33], [34], making FD communication systems become feasibly in realistic scenarios. On the other hand, the residual self-interference (RSI) after all SIC techniques (denoted by I R ) become Gaussian variable with zero mean and variance of γ RSI [35]- [37], where γ RSI is…”

“…where γ R and γ D are respectively given by ( 7) and (8). Let γ th = 2 R 1−α − 1 be the SINR threshold.…”

“…However, a major issue of FD transmission is the self-interference (SI) from the transmitting antenna to the receiving antenna of FD device. Fortunately, recent studies and experiments have reported that the SI can be reduced up to 110 dB by using several self-interference cancellation (SIC) solutions such B. C. Nguyen et al: Impacts of Nonlinear Energy Harvesting and Residual Self-Interference antenna designs, analog and digital signal processing [8], [9]. When effective SIC solutions are deployed so that FD devices can successfully decode the desired signal from the received signals.…”