Full-duplex Wireless Communication Research Articles

An Investigation Into Baseband Techniques for Single-Channel Full-Duplex Wireless Communication Systems

Full-duplex wireless communication is becoming an important research area because of its potential for increasing spectral efficiency. The challenge of such systems lies in cancelling the self-interference. In this paper, we focus on the design of digital cancellation schemes and use them to supplement RF/analog cancellation techniques. The performance of digital cancellation is limited by the non-ideal characteristics of different subsystems in the transceiver, such as analog/digital converter (ADC), power amplifier (PA), and phase noise. It is first shown that given the pre-cancellation achieved by existing RF/analog techniques, the effects of ADC, phase noise, and sampling jitter are not the bottleneck in the system. Instead, the performance of conventional digital cancellation approaches are mainly limited by nonlinearity of the PA and transmit I/Q imbalance. In addition, the output SINR of the desired signal is limited because the estimation precision of the self-interference channel is affected by the desired signal. To overcome these issues, we propose a two-stage iterative self-interference cancellation scheme based on the output signal of the power amplifier. Analytical and simulation results reveal that the proposed cancellation scheme substantially outperforms existing digital cancellation schemes for full-duplex wireless communication systems.

Guest Editorial: In-Band Full-Duplex Wireless Communications and Networks

The articles in this special issue focus on the technology and applications supported by in-band full duplex wireless services.

Complex signal transmission for multi‐user multiple‐input multiple‐output relay

A full-duplex wireless communications system is considered where K user wants to exchange common messages and private messages via a relay with multiple antennas simultaneously. The proposed scheme combines signal space alignment with zero forcing during multiple access channel phase and broadcast channel phase to cancel self-interference. The authors can achieve high degree of freedom by using successive network coding and aligning multiple interfering signals. The result is extended to a more generalised Y channel circumstance where they can transfer each message with different interference-free streams.

A New In-band Full-duplex SIC Scheme Using a Phase Rotator

How well the self-interference cancellation (SIC) technique performs is a primary issue in realizing an in-band full-duplex (FD) wireless communication system. One factor affecting its performance is channel estimation error on the self-interference channel. We propose a new analog SIC scheme which is robust to channel estimation error. It uses phase rotators in the radio frequency (RF) chain. We also derive closed-form equations for the residual self-interference of the proposed and the conventional schemes. The analytical and numerical results show that the residual self-interference under the proposed SIC scheme is less than that using the conventional scheme, even though channel estimation error is present.

Performance Analysis of RF Self-Interference Cancellation in Full-Duplex Wireless Communications

An expression of radio frequency (RF) interference cancellation ratio (ICR) is derived for full duplex wireless communications, considering the amplitude and phase errors in Rician fading channel. The results show that the amplitude and phase estimation errors of line-of-sight (LOS) components are the significant factors that limited the performance when Rician factor K > 1. ICR 55 dB can be achieved when the standard deviation of LOS component relative amplitude error is less than 0.1% and the standard deviation of LOS component phase error is less than 0.1°.

全双工通信关键技术研究

Traditional half-duplex (HD) wireless systems transmit and receive signals adopting orthogonal time-slots, resulting in a great waste of frequency resources. And full-duplex (FD) wireless communication techniques have drawn extensive attention from academia and industry for the attractive abilities of doubling the channel capacity and promoting the utilization of spectrum resources. We frame the paper by rst comparing the per-formance of HD and FD modes and addressing the advantages and disadvantages of the existing FD techniques. As the core problem of FD systems, self-interference (SI) cancellation will be realized by two main techniques: passive self-interference suppression and active self-interference cancellation. In this paper, we also present the advantages and disadvantages of respective techniques. Besides, the design of FD media access control (FD-MAC) layer is carried out based on the complex time-varying wireless spectrum environment and the dynamic wireless network structure. Furthermore, the design and implement of FD algorithms are presented in this paper, including relay network coding, relay selection and dynamic resource allocation. Finally, we summarize the future research directions and conclude the whole paper.

Application of Full-Duplex Wireless Technique into Secure MIMO Communication: Achievable Secrecy Rate based Optimization

This letter considers the secure MIMO transmission in a wireless environment, in which one transmitter (Alice), one receiver (Bob) and one eavesdropper (Eve) are involved. Apart from the artificial noise (AN) generated by Alice, Bob can also exploit his remaining antenna resources to emit AN to further impair Eve's channel. Such kind of AN can be cancelled by Bob himself by applying the Full-Duplex wireless communication technique. A computable secrecy rate is obtained for this model over a Rayleigh-fading eavesdropping channel. In order to maximize the secrecy rate, a joint optimization scheme is proposed to assign the TX/RX antennas for Bob and to design the beamforming and power allocation for Alice's information and AN signal. Simulation is carried out to illustrate the process of the proposed optimization scheme.

Image and Video Error Rate Analysis in Full Duplex Communication Using Phase Offset

ne of the most efficient way to utilize the bandwidth in wireless communication systems is Full- duplex communication. It is proposed for full duplex wireless communication over a single channel. The signals are transmitted and received at a same time and same frequency. It creates the large self-interference over the transmitted and received signals and lead to large loss of data. We used different values of phase offset to reduce the self-interference between the transmitted and received signals. The full duplex communication system is designed for input as image and by using wavelet transform. The performance of full-duplex communication system using various modulations like 16-QAM, QPSK and 64-QAM along with Haar, Daubechies2 and Daubechies 4 wavelets over different values of phase offset are evaluated by bit error rate.

Passive Self-Interference Suppression for Full-Duplex Infrastructure Nodes

Recent research results have demonstrated the feasibility of full-duplex wireless communication for short-range links. Although the focus of the previous works has been active cancellation of the self-interference signal, a majority of the overall self-interference suppression is often due to passive suppression, i.e., isolation of the transmit and receive antennas. We present a measurement-based study of the capabilities and limitations of three key mechanisms for passive self-interference suppression: directional isolation, absorptive shielding, and cross-polarization. The study demonstrates that more than 70 dB of passive suppression can be achieved in certain environments, but also establishes two results on the limitations of passive suppression: (1) environmental reflections limit the amount of passive suppression that can be achieved, and (2) passive suppression, in general, increases the frequency selectivity of the residual self-interference signal. These results suggest two design implications: (1) deployments of full-duplex infrastructure nodes should minimize near-antenna reflectors, and (2) active cancellation in concatenation with passive suppression should employ higher-order filters or per-subcarrier cancellation.

Performance Analysis of Bit Error Rate in Full-Duplex Wireless Communications with Analog Cancellation Error

Recent work has shown the full duplex transmission scheme to allow nodes to send and receive in the same frequency at the same time. In this paper, we investigate the impact of analog cancellation error on the bit error rate (BER) performance of full duplex wireless communication system. Considering the transmission delay error, amplitude error and phase error of analog cancellation, we derive the analytic BER expression of binary phase shift keying (BPSK) in additive white Gaussian noise (AWGN) channel. The analysis results show that BER generally decreases with timing and amplitude error decreases for fixed signal to interference rate (SIR). Compared with the ideal analog cancellation system, the performance loss 0.3dB when the phase error is 0.0001 degree, carrier frequency is 800MHz and SIR is 100dB.

Call for Papers - IEEE Journal on Selected Areas in Communications: Full-DuplexWireless Communications and Network

Call for Papers - IEEE Journal on Selected Areas in Communications: Full-DuplexWireless Communications and Network

Rate Gain Region and Design Tradeoffs for Full-Duplex Wireless Communications

In this paper, we analytically study the regime in which practical full-duplex systems can achieve larger rates than an equivalent half-duplex systems. The key challenge in practical full-duplex systems is uncancelled self-interference signal, which is caused by a combination of hardware and implementation imperfections. Thus, we first present a signal model which captures the effect of significant impairments such as oscillator phase noise, low-noise amplifier noise figure, mixer noise, and analog-to-digital converter quantization noise. Using the detailed signal model, we study the rate gain region, which is defined as the region of received signal-of-interest strength where full-duplex systems outperform half-duplex systems in terms of achievable rate. The rate gain region is derived as a piece-wise linear approximation in log-domain, and numerical results show that the approximation closely matches the exact region. Our analysis shows that when phase noise dominates mixer and quantization noise, full-duplex systems can use either active analog cancellation or base-band digital cancellation to achieve near-identical rate gain regions. Finally, as a design example, we numerically investigate the full-duplex system performance and rate gain region in typical indoor environments for practical wireless applications.

High-Speed Full-Duplex Optical Wireless Communication System with Single Channel Imaging Receiver for Personal Area Networks

In this paper, we propose a high-speed full-duplex optical wireless communication system using a single channel imaging receiver for personal area network applications. This receiver is composed of an imaging lens, a small sensitive-area photodiode, and a 2-aixs actuator and it can reject most of the background light. Compared with the previously proposed system with single wide field-of-view (FOV) non-imaging receiver, the coverage area at 12.5Gb/s is extended by > 20%. Furthermore, since the rough location information of the user is available in our proposed system, instead of searching for the focused light spot over a large area on the focal plane of the lens, only a small possible area needs to be scanned. In addition, by pre-setting a proper comparison threshold when searching for the focused light spot, the time needed for searching can be further reduced. Proof-of-concept experiments have been carried out and the results show that with this partial searching algorithm and pre-set threshold, better performance is achieved.

A Shared Aperture Dual-Frequency Circularly Polarized Microstrip Array Antenna

A novel 2 2 array of microstrip antennas was developed that generates orthogonal circularly polarized waves at two frequencies simultaneously. This true shared aperture can be used as a building block in full-duplex wireless communication applications such as focal-plane arrays for satellite internet (VSAT) and wireless connectors. An alternative implementation of the sequential rotation technique was applied to create dual-frequency operation using only a single aperture. The concept was verified with experimental results from a prototype consisting of a 2 2 array of aperture coupled microstrip antennas (ACMAs) with corresponding feed network operating at 4 and 6 GHz. Measurements show that the axial ratio (AR) is below 1.2 dB for both the low-band as well as the high-band mode of operation. The isolation between both modes is larger than 26 dB, eliminating the need of high-performance duplexers.

Experiment-Driven Characterization of Full-Duplex Wireless Systems

We present an experiment-based characterization of passive suppression and active self-interference cancellation mechanisms in full-duplex wireless communication systems. In particular, we consider passive suppression due to antenna separation at the same node, and active cancellation in analog and/or digital domain. First, we show that the average amount of cancellation increases for active cancellation techniques as the received self-interference power increases. Our characterization of the average cancellation as a function of the self-interference power allows us to show that for a constant signal-to-interference ratio at the receiver antenna (before any active cancellation is applied), the rate of a full-duplex link increases as the self-interference power increases. Second, we show that applying digital cancellation after analog cancellation can sometimes increase the self-interference, and thus digital cancellation is more effective when applied selectively based on measured suppression values. Third, we complete our study of the impact of self-interference cancellation mechanisms by characterizing the probability distribution of the self-interference channel before and after cancellation.