In-band Full-duplex Wireless Communication Research Articles

Self-Interference Cancellation Techniques for In-Band Full-Duplex Wireless Communication Systems: A Review

In-Band Full-Duplex (IBFD) systems have the capability of simultaneously transmitting and receiving signals through the channel and require the same resources as half-duplex systems. Unfortunately, IBFD systems have self-interference (SI) issues that prevent the system from gaining double throughput with respect to half-duplex systems. Therefore, the IBFD system will be more reliable if SI is mitigated more. This contribution will look at SI cancellation in wireless radio and underwater acoustic systems. The reviewed documents cover all types of SI cancellations, including passive, analog, and digital cancellations. In a practical full-duplex system, the SI cancellation for all domains must cancel the SI below the receiver noise floor.

Evaluating Analog Self-Interference Cancellation for In-Band Full-Duplex Wireless Communication

In-band full-duplex (IBFD) technology allows simultaneous transmission and reception in the same frequency band to boost spectral efficiency. However, selfinterference, introduced by transmitter-to-receiver leakage, poses the biggest obstacle to the realization of IBFD. Altogether IBFD radio performance and effective network throughput are directly correlated with the amount of energy suppressed by self-interference cancellation (SIC). In this work a model of an IBFD transceiver, featuring an adaptive, analog-domain, tapped-branch self-interference canceller, was developed to evaluate the inimical effects attributable to the various noise and nonlinear distortions of the simulated transceiver components. Results of the simulation show that noise incursions and nonlinearity in the transmission channel produced a negligible effect on the overall cancellation performance. However, the effectiveness of the cancellation hardware is highly dependent on the level of intrinsic nonlinearity within the canceller’s own components. Consideration of these non-ideal characteristics should be an essential part of analog SIC design to prevent any intrinsic limitations on the cancellation performance.

Design and Performance Analysis of an In-Band Full-Duplex MAC Protocol for Ad Hoc Networks

This paper proposes a MAC protocol for ad hoc networks using In-band Full-duplex (IBFD) wireless communications, which are named as AdHoc-FDMAC. To utilize IBFD communications in ad hoc networks, this protocol modifies a number of control frames in the IEEE 802.11 Distributed Coordination Function (DCF) MAC standard. Here, the detailed time sequences for all types of IBFD communications are shown for the data transmission and routing. In this paper, the probability and throughput equations for IBFD communications in different situations have been derived. The performance of the proposed AdHoc-FDMAC has been analysed in terms of probability, throughput, and routing time. The Maximum throughput of AdHoc-FDMAC has been found to be 48.34 Mbps, and it is compared with a recently published ad hoc MAC as well as with the conventional HD MAC. The AdHoc-FDMAC outperforms the recently published ad hoc MAC and conventional HD MAC by 16.80% and 66.50% throughput gain, respectively. AdHoc-FDMAC incorporates the existing Ad hoc On-demand Distance Vector (AODV) routing protocol, but this AODV routing is utilized here using IBFD communications. This paper also compares the routing time of the IBFD-based AODV with the conventional AODV. The result shows that the IBFD-based AODV requires 33.33% less routing time than that of the conventional AODV for 3-hop distance between the transmitter and receiver. This paper suggests that the AdHoc-FDMAC protocol provides much more throughput in ad hoc networks by utilizing IBFD communications.

Optical Multi-Tap RF Canceller for In-Band Full-Duplex Wireless Communication Systems

In-band full-duplex (IBFD) technology has become important for future wireless communications, due to its ability of increasing the radio-frequency (RF) spectrum efficiency. However, the benefits can only be realized if the self-interference (SI) is sufficiently suppressed. RF cancellation is important for IBFD systems due to its ability of SI mitigation. But it becomes more difficult for RF cancellation while the frequency and bandwidth increase. In real scenarios, the response of the multi-path SI channel is not frequency-flat, which also limits the cancellation performance. To solve these problems, we present a photonic-enabled multi-tap RF canceller in this paper. The proposed RF canceller has the ability of cancelling multi-path SI. The tap coefficients are precisely adjusted by optical spectrum processing. A prototype system with 8 taps is demonstrated in this paper. The measured results show 25 dB average cancellation depth over 1 GHz cancellation bandwidth under over-the-air conditions. To verify the signal of interest (SOI) recovery capability of the novel RF canceller, an IBFD wireless communication experiment based on 16-quadrature amplitude modulation (16-QAM) was demonstrated, the SOI was successfully recovered.

A Lazy Learning-Based Self-Interference Cancellation Approach for In-Band Full-Duplex Wireless Communication Systems

We propose a new lazy learning-based cancellation approach to improve spectral efficiency for current wireless communication systems, suppress self-interference (SI) sent from base stations, and enable in-band full-duplex (IBFD) transmissions in cellular networks. Our proposed approach consists of two phases based on traditional IBFD systems: an offline phase for database generation and an online phase for data transmission. In the offline phase, the output before a 0/1 decision is premeasured without the desired signal input and recorded in a database with self-defined feature vectors (FVs). In the online phase, a suitable result is sought from the generated database with the help of a learning method and FV for the same system architecture with the desired signal input. The result is then assigned an SI cancellation value. Regular and eager learning-based cancellation approaches are employed to evaluate the proposed method and simulate the transmission output. Computer simulation results indicated that the proposed cancellation methods could achieve about 134 dB SI suppression and achieve nearly the same transmission levels as methods with no SI effect, enabling the IBFD operations in wireless communication systems better than the regular and eager learning-based techniques.

Antenna/Propagation Domain Self-Interference Cancellation (SIC) for In-Band Full-Duplex Wireless Communication Systems

In-band full duplex (IBFD) is regarded as one of the most significant technologies for addressing the issue of spectrum scarcity in 5G and beyond systems. In the realization of practical IBFD systems, self-interference, i.e., the interference that the transmitter causes to the collocated receiver, poses a major challenge to antenna designers; it is a prerequisite for applying other self-interference cancellation (SIC) techniques in the analog and digital domains. In this paper, a comprehensive survey on SIC techniques in the antenna/propagation (AP) domain is provided and the pros and cons of each technique are studied. Opportunities and challenges of employing IBFD antennas in future wireless communications networks are discussed.

Blind Source Separation For Full-Duplex Systems: Potential and Challenges

Full-duplex communications systems that transmit and receive simultaneously suffer self-interference due to the mixing of the transmitted signal and the weaker received signal at the same node. The problem becomes compounded in Multi-Input Multi-Output (MIMO) systems, where considerable overhead is dedicated to training. In this article, we discuss using blind source separation techniques, namely Independent Component Analysis (ICA) to reduce training overhead in MIMO in-band full-duplex wireless communication systems. Practical limitations are discussed and experimental results that compare ICA to traditional Least Square approaches are presented, showing the superiority of ICA, especially in low SNR regimes.

Iterative Nonlinear Self-Interference Cancellation for In-Band Full-Duplex Wireless Communications Under Mixer Imbalance and Amplifier Nonlinearity

This paper presents an iterative estimation and cancellation technique for nonlinear in-band full-duplex transceivers with IQ imbalances and amplifier nonlinearities. The estimation process of the proposed scheme consists of three stages, namely, the channel response estimation, IQ imbalance estimation, and power amplifier and low-noise amplifier (LNA) nonlinearities estimation. For the estimation of the parameters and improvement of the accuracy, distortions are compensated by cancellation or inversion with the latest estimated parameters. On the one hand, the channel response is estimated on the time domain; on the other hand, the IQ imbalance and nonlinearities are estimated on the frequency domain for a more straightforward estimation and superior accuracy. In the cancellation process of the proposed scheme, the received signal is compensated with the estimated parameters of the LNA and receiver IQ imbalance before cancellation because the desired signal is received with a high-power self-interference and is distorted by the radio-frequency receiver impairments. Simulation results show that the proposed technique can achieve higher cancellation performance compared with the Hammerstein canceller when the LNA is saturated by the self-interference. Additionally, the performance of the proposed canceller converges much faster than that of the Hammerstein canceller.

Queueing and channel access delay analysis in in-band full-duplex wireless networks

In-band full-duplex wireless communication, which supports a node to transmit and receive simultaneously in the same frequency band, is receiving growing interest. The latency of packets in an in-b...

USRP 장치를 이용한 동일대역 전이중 무선통신 연구

The implementation of an in-band full-duplex wireless communication system is demonstrated in this study. In the analog/RF domain, the self-interference(SI) signal is reduced using a separate antenna for the transmitter and receiver paths, and most of the SI signal is canceled in the digital domain. A software defined radio(SDR) is used to implement the in-band full-duplex wireless communication system. The USRP X310 device uses transmitting and receiving antennas. By adjusting the gain of the transmitting and receiving ends of the SDR device, the magnitude of the SI signal entering the receiving antenna, and the size of the received signal from the outside, are both set to −64 dB. To verify the in-band full-duplex wireless communication performance, the source data is image and orthogonal frequency-division multiplexing is used for modulation. A WiFi standard frame with a carrier frequency of 2.67 GHz and bandwidth of 20 MHz is used. In the received signal, the SI signal is canceled by digital signal processing and the SI signal is attenuated by up to 34 dB. OFDM demodulation was impossible when the SI signal was not removed. However, the bit error rate is reduced to 2.63×10−5 when the SI signal is attenuated by 34 dB, and no error is detected in the 100 Mbit data output as a result of passing through the Viterbi decoder.

Geometry-Based Statistical Channel Models of Reflected-Path Self-Interference in Full-Duplex Wireless

Self-interference (SI) channel characteristics are crucial for SI cancellation (SIC) techniques of in-band full-duplex (IBFD) wireless communications. This paper develops two geometry-based statistical channel models-geometry-based concentric ellipses model (GBCEM) and geometry-based concentric circles model (GBCCM)-for full-duplex systems in micro- and macrocell environments, respectively, to analyze the characteristics of reflected-path SI (RSI) compared with the desired signal (DS). The probability density functions of incident angle and path length are derived to identify the fading characteristics of RSI and DS. The simulations based on GBCEM and GBCCM intuitively present the signal characteristics by the signal envelope in the time domain, the statistics of signal envelope, the autocorrelation properties, and the power spectral density. We find that the fading characteristics of RSI and DS can be modeled as Rayleigh when reflectors sit far away from the receiver. We also find that RSI is still likely to be Rayleigh fading, even if DS is not when reflectors scatter in a specific region restricted by the range of incident angle. Our works on the characteristics of RSI and DS are generally helpful to explore a more efficient SIC mechanism for IBFD systems, and the developed models are useful for both simulation and analysis purposes.

Ultra-Dense 5G Small Cell Deployment for Fiber and Wireless Backhaul-Aware Infrastructures

In this paper, we study the cell planning problem for a two-tier cellular network containing two types of base stations (BSs), i.e., with fiber backhaul, referred to as wired BSs (W-BSs), and BSs with wireless backhaul, referred to as unwired-BSs (U-BSs). In-band full-duplex wireless communications is used to connect U-BSs and W-BSs. We propose an algorithm to determine the minimum number of W-BSs and U-BSs to satisfy given cell and capacity coverage constraints. Furthermore, we apply our proposed non-dominated sorting genetic algorithm II (NSGA-II) to solve both cell planning and joint cell and backhaul planning problem to minimize the cost of planning, while maximizing the coverage simultaneously. Additionally, the considered cell planning program is developed into an optimization by including the problem of minimizing the cost of fiber backhaul deployment. In order to analyze the performance of the proposed algorithm, we study three different deployment scenarios based on different spatial distributions of users and coverage areas. The results show the superiority of our proposed NSGA-II algorithm for both cell planning and joint cell and backhaul planning to other well-known optimization algorithms. The results also reveal that there is a tradeoff between cell deployment costs and SINR/rate coverage, and W-BSs are placed in congested areas to consume less resources for wireless backhauls. Similarly, a tradeoff between cell and fiber deployment costs and SINR/rate coverage is observed in planning. We show that for realistic scenarios desirable solutions can be selected from the Pareto front of the introduced multi-objective problem based on given cellular operator policies.

Self-Interference Cancellation Enabling High-Throughput Short-Reach Wireless Full-Duplex Communication

In-band full-duplex (FD) wireless communication allows the simultaneous transmission and reception of data at the same frequency band, effectively doubling the spectral efficiency and data rate while reducing the latency. Previously published designs mostly target the self-interference (SI) cancellation in conventional wireless systems. In this paper, we focus on real-time SI cancellation for short-reach wireless FD systems. The superior signal quality of a point-to-point short-reach wireless system, allows the utilization of wideband communications to achieve a high throughput. Besides, in such wireless systems, the impacts of phase noise and nonlinear distortions are largely reduced, easing the SI cancellation. Moreover, the degradation of signal reception quality due to FD operation is experimentally evaluated in different environments. Experimental results of a prototype implementation show that a combination of antenna isolation and digital cancellation can already achieve an overall SI cancellation performance of 72.5 dB over a bandwidth of 123 MHz. This prototype can support a high-data-rate FD communication link of close to 1 Gbps up to 300 cm with an error vector magnitude lower than −26 dB in a typical indoor environment.

Asym-FDMAC: In-band full-duplex medium access control protocol for asymmetric traffic in wireless LAN

Recent advancements in antenna design and signal processing have made it feasible to transmit and receive simultaneously by using the same carrier frequency, which is defined as in-band full-duplex (IBFD) wireless communications. Along with physical layer advancements, efficient medium access control (MAC) design is required to derive optimal benefit from this latest technology. In this paper, an IBFD MAC protocol named Asym-FDMAC, is proposed for infrastructure based WLAN to support asymmetric lengths of traffic for uplink and downlink. This MAC protocol enables multiple users to transmit data to the access point (AP) during the transmission of a single downlink frame from the AP. In Asym-FDMAC, the AP always initiates the transmission. Therefore, there is no contention period and thus, there is no collision among the user terminals and the AP for channel access. A mathematical analysis of Asym-FDMAC is presented together with an evaluation of its performance, which involved a comparison with traditional IBFD and half-duplex (HD) communications. On average, the highest throughput gain achieved by Asym-FDMAC was approximately 54% and 94% compared with traditional IBFD and HD communications respectively, although the lowest average throughput gain was observed as about 50% and 89%, respectively.

Basis Function Selection of Frequency-Domain Hammerstein Self-Interference Canceller for In-Band Full-Duplex Wireless Communications

This paper presents a basis function selection technique of a frequency-domain Hammerstein digital self-interference canceller for in-band full-duplex communications. The power spectral density (PSD) of the nonlinear self-interference signal is theoretically analyzed in detail, and a nonlinear self-interference PSD estimation method is developed. The proposed selection technique decides on the basis functions necessary for cancellation and relaxes the computational cost of the frequency-domain Hammerstein canceller based on the estimated PSD of the self-interference of each basis function. Furthermore, the convergence performance of the canceller is improved by the proposed selection technique. Simulation results are then presented, showing that the proposed technique can achieve similar cancellation performance compared with the original frequency-domain Hammerstein canceller and a time-domain nonlinear canceller. In addition, it is shown that the proposed technique improves the computational cost and the convergence performance of the original frequency-domain Hammerstein canceller.

Semi-Blind SI Cancellation for In-Band Full-Duplex Wireless Communications

Blind known self-interference cancellation (BKSC) is particularly attractive in self-interference (SI) reduction for full-duplex (FD) systems, because it requires no interference channel state information (CSI) and the overhead of capturing the full CSI on SI can be saved. In this letter, a semi-blind SI cancellation method is proposed for FD systems under phase noise. By applying the idea of BKSC in the frequency domain, this method is designed to extract partial CSI of the SI for removing the interference that results from differential operations in BKSC schemes. The closed-form expression for the power of the residual SI is also derived in the presence of phase noise. As a low-complexity method that requires no specific pilot design or complex estimation algorithms, the proposed scheme can effectively suppress the SI signal in the presence of phase noise, which outperforms conventional least-square-based SI cancellation schemes.

In-band full duplex wireless communications and networking for IoT devices: Progress, challenges and opportunities

The new era of IoT devices call for wireless communications with high spectral efficiency because of the congested spectral space in reality. Current wireless communication systems work at half duplex mode in an either time-division or frequency-division approach to transmit and receive wireless signals. Half duplex results in poor spectral efficiency because only unidirectional communications are allowed. Recent research has aimed at enabling In-band full duplex wireless communication that allows a wireless node for simultaneous transmission and reception of signals. The benefits of in-band full duplex includes the doubled spectra efficiency which is in great need in the rapidly growing IoT devices and the potentials to solve the hidden terminals, unfairness and the exposed problems presented in the current single channel half duplex wireless communications. This paper investigates the research background and progress of in-band full duplex wireless. It also presents the research problems as well as opportunities. In addition, this paper summarizes the performance of literature solutions with experiment results in achieving in-band full duplex wireless communications. It also compares the Throughput and Packet Reception Ratio performance of full duplex to that of half duplex from a Software Defined Radio platform.

Over-the-air in-band full-duplex system with hybrid RF optical and baseband digital self-interference cancellation

In this paper, we propose a hybrid analog optical self-interference cancellation (OSIC) and baseband digital SIC (DSIC) system for over-the-air in-band full-duplex (IBFD) wireless communication. Analog OSIC system is based on optical delay line, electro-absorption modulation lasers (EMLs) and balanced photodetector (BPD), which has the properties of high adjusting precision and broad processing bandwidth. With the help of baseband DSIC, the cancellation depth limitation of OSIC can be mitigated so as to achieve deeper total SIC depth. Experimental results show about 20-dB depth by OSIC and 10-dB more depth by DSIC over 1GHz broad baseband, so that the signal of interest (SOI) overlapped by wideband self-interference (SI) signal is better recovered compared to the IBFD system with OSIC or DSIC only. The hybrid of OSIC and DSIC takes advantages of the merits of optical devices and digital processors to achieve deep cancellation depth over broad bandwidth.

ReflectFX: In-Band Full-Duplex Wireless Communication by Means of Reflected Power

In this paper, we introduce a new full-duplex wireless communication system, named ReflectFX, that relies on backscatter modulation. This paper offers a new concept for two-way wireless communication: rather than avoiding self-interference as in half-duplex, or combatting self-interference as in conventional full-duplex, nodes will re-use the received interfering radio-carrier waves to transfer information. The electromagnetic waves are modulated and reflected by the same antenna that receives them. We consider two nodes, a base-station and an end-user, that wish to exchange data over a wireless Rayleigh fading channel with additive white Gaussian noise. With ReflectFX, the end-user receives a self-interference free signal. We improve the transmission range of ReflectFX by adding negative resistance to the end-user load. We derive an expression for the overall achievable throughput and ergodic capacity of ReflectFX. Simulation results show that ReflectFX outperforms both conventional full-duplex and half-duplex.

Experimental study of wideband in-band full-duplex communication based on optical self-interference cancellation.

In this paper, we experimentally demonstrate and study a wideband in-band full-duplex (IBFD) wireless communication system based on optical self-interference cancellation (SIC). The optical SIC performances based on antennas for broadband IBFD are firstly evaluated within high frequency bands (> 10GHz). In this system, two electro-absorption-modulated lasers (EMLs) and a balanced photo-detector (BPD) are employed to remove the wideband self-interference within received wireless signal. By theoretical derivation and experimental verification, the impact factors of SIC are analyzed, especially for non-flatness wireless channel case. Experimental results show more than 30-dB cancellation depth in 100-MHz bandwidth with employment of horn antennas. Besides, IBFD transmission performance based on OFDM signals for different bandwidth with 11.15-GHz center frequency is also demonstrated, and ~52.2- dB•Hz2/3 spurious-free dynamic range (SFDR) is obtained.