While conventional half-duplex wireless systems rely on transmitting and receiving in non-overlapping time slots or frequency channels, full duplex (FD) communications and the underlying self-interference cancellation (SIC) techniques may improve the attainable spectral efficiency while reducing latency. This is made possible by recent advances in antenna design and signal processing techniques specifically in multiple input multiple output systems, which make SIC of 80-110 dB possible. In fact, SIC has been demonstrated in applications requiring even more than 110 dB of interference cancellation. We expect that in the future, SIC technologies will enable not only FD communications, but also a variety of spectrum-sharing applications by creating radio technologies that are tolerant of adjacent and co-channel interference.
Recent developments in standardization and commercial deployments point at a progression towards small cells and higher frequencies, including millimeter-wave frequencies in the 3rd Generation Partnership Project’s frequency range 2, FR2. In these frequency bands, self-backhauled small cells through the so-called integrated access and backhaul (IAB) solutions enable fast densification of wireless networks. IAB deployments benefit largely from advanced SIC techniques. Other applications that will be enabled or made more efficient by advanced SIC algorithms include those that require isolating signals on the same, overlapping, or immediately adjacent frequencies.
While SIC and FD for bidirectional communications have been researched since the 1990’s, they have only recently been demonstrated as cost-efficient technology components in the next generation of cellular networks. Most existing research results suggest that to achieve more than 100 dB of interference cancellation, a combination of antenna isolation, active analog cancellation, and digital cancellation is needed. On the one hand, analog-to-digital converters do not have sufficient dynamic range to achieve 100 dB or higher cancellation. On the other hand, the cancellation capability of analog cancellers is affected by reflections from objects that may be far away from the receiver and the need for incorporating long delays in analog circuits. Therefore, ongoing research activities target to develop cost efficient hybrid solutions that utilize both analog and digital cancellation techniques and can be integrated in contemporary multi-antenna architectures. Also, when FD transmissions are used in multi-cell networks, the cross-link interference caused by multiple transmitters operating in the same frequency bands in neighboring cells must be mitigated.
In this Best Readings, we introduce several archival papers and special issues on the topic of SIC and FD wireless communications that are available on IEEE Xplore. The Best Readings include five book titles, six tutorials, and seven special issues that are all dedicated to the theory and practice of wireless FD technologies. While these items provide a holistic picture of the state of the art, the subsequent sections of the Best Reading focus on specific topics related to SIC and FD techniques. These sections include Foundations, Self-Interference cancellation, Experiments and testbeds, 5G cellular networks, Medium access control, Resource allocation, Resource allocation for MIMO, Relaying, Wireless power transfer, and useful readings and resources available on the Internet.
Issued: February 2021
Gabor Fodor, KTH Royal Institute of Technology and Ericsson Research, Sweden
Taneli Riihonen, Tampere University, Finland
José Mairton Barros da Silva Júnior, KTH Royal Institute of Technology, Sweden
Chan-Byoung Chae, Yonsei University, Korea
Risto Wichman, Aalto University Finland
Ashutosh Sabharwal, Rice University, Texas, USA
Raghu M. Rao, GenXComm, Austin, Texas, USA
Matthew C. Valenti
Editor-in-Chief, ComSoc Best Readings
West Virginia University
Morgantown, WV, USA
Associate Editor-in-Chief, ComSoc Best Readings
London, ON, Canada
Y. Liao, T. Wang, L. Song, and Z. Han, Listen and Talk: Full-duplex Cognitive Radio Networks, Springer, 2016.
This book focuses on the use of full-duplex radio in cognitive radio networks, presenting a novel spectrum sharing protocol that allows the secondary users to simultaneously sense and access the vacant spectrum. This protocol, called “Listen-and-talk”, is evaluated by both mathematical analysis and computer simulations in comparison with other existing protocols, including the listen-before-talk protocol. In addition to Listen-and-talk based signal processing and resource allocation, the book discusses techniques such as spectrum sensing and dynamic spectrum access. The book is important for researchers, developers, and professionals involved in cognitive radio networks and future applications for the technology.
L. Song, R. Wichman, Y. Li, and Z. Han, Full-Duplex Communications and Networks, Cambridge University Press, 2017.
This book explains the fundamental theories on which full-duplex communications are built, and lays out the techniques needed for network design, analysis and optimization. The techniques covered in detail include self-interference cancellation and signal processing algorithms, physical layer algorithms, methods for efficient resource allocation, and game theory. It is an indispensable reference for both researchers and practitioners designing the next generation of wireless networks.
T. Le-Ngoc and A. Masmoudi, Full-Duplex Wireless Communications Systems: Self-Interference Cancellation, Springer, 2017.
This book introduces the development of self-interference cancellation techniques for full-duplex wireless communication systems. The authors employ estimation theory and signal processing to develop self-interference cancellation algorithms. This book aims to provide researchers and engineers in an understanding of the challenges of deploying full-duplex and practical solutions to implement a full-duplex system.
H. Alves, T. Riihonen, and H. A. Suraweera, Full-Duplex Communications for Future Wireless Networks, Springer, 2020.
This book gives an overview of the multidisciplinary state-of-the-art of self-interference cancellation techniques and full-duplex wireless communications and their applications. The book surveys the most recent advances in self-interference cancellation from antenna design to digital domain. Moreover, the reader will discover analytical and empirical models to deal with residual self-interference and to assess its effects in various scenarios and applications. Therefore, this is a highly informative and carefully presented book by the leading scientists in the area.
D. Cruickshank, Implementing Full Duplexing for 5G, Artech, IBSN 9781630816964, 2020.
This book examines the current state of the art in developing full duplex (FD) systems in 5G LTE cellular communications. The book also considers what can be achieved with ferrite-based circulators in terms of size reduction and performance enhancement, especially at millimetric frequencies. The relative merits of ferrite and non-ferrite circulators are compared in terms of their fundamental materials and device technologies, such as isolation, insertion loss, bandwidth and non-linearity. FD in the entire 5G cell is also examined and its resulting range of equipment and device communication. This includes front-hauling, more sophisticated back and front-hauling, backhaul beam switching, and cell extenders and relays, all of which could involve FD. The chapter on MIMO-based nodes will be especially useful for network equipment designers.
- Overviews and Tutorials
A. Sabharwal, P. Schniter, D. Guo, D. W. Bliss, S. Rangarajan, and R. Wichman, “In-band Full-duplex Wireless: Challenges and Opportunities,” IEEE Journal on Selected Areas in Communications, vol. 32, no. 9, pp. 1637-1652, September 2014.
This tutorial article surveys a wide range of self-interference cancellation/mitigation and in-band full-duplex (IBFD) techniques and reviews the main concepts of IBFD wireless. This work reviews the history of IBFD wireless, including its longstanding use in radar systems, to current wireless technology. Also discussed are numerous other research challenges and opportunities in the design and analysis of IBFD wireless systems.
D. Kim, H. Lee, and D. Hong, “A Survey of In-Band Full-Duplex Transmission: From the Perspective of PHY and MAC Layers,” IEEE Communications Surveys & Tutorials, vol. 17, no. 4, pp. 2017-2046, Fourth Quarter 2015.
This survey covers a wide array of technologies that have been proposed in the literature for in-band full-duplex (IBFD) transmissions. The performance of the IBFD systems is compared to conventional half-duplex transmission along with theoretical aspects such as the achievable sum rate, network capacity, system reliability, and so on. This work also discusses research challenges and opportunities associated with the design and analysis of IBFD systems in a variety of network topologies. In addition, it also explores the development of medium access control protocols for an IBFD system in both infrastructure-based and ad hoc networks. This survey reviews the advantages of IBFD transmission when applied for different purposes, including spectrum sensing, network secrecy, and wireless power transfer.
G. Liu, F. R. Yu, H. Ji, V. C. M. Leung, and X. Li, “In-Band Full-Duplex Relaying: A Survey, Research Issues and Challenges,” IEEE Communications Surveys & Tutorials, vol. 17, no. 2, pp. 500-524, Second Quarter 2015.
This work provides a survey on some of the works for in-band full-duplex relaying (FDR), and discusses the related research issues and challenges. The work identifies five important aspects of in-band FDR: basics, enabling technologies, information-theoretical performance analysis, key design issues and challenges. In addition, this work identifies the challenges and research opportunities of in-band FDR networks and explores broader perspectives, such as full-duplex wireless beyond FDR, heterogeneous networks, cognitive radio networks, green communications and wireless network virtualization.
Z. Zhang, K. Long, A. V. Vasilakos, and L. Hanzo, “Full-Duplex Wireless Communications: Challenges, Solutions, and Future Research Directions,” Proceedings of the IEEE, vol. 104, no. 7, pp. 1369-1409, July 2016.
This survey presents a comprehensive list of the potential full-duplex techniques and highlight their pros and cons, including a classification of the self-interference cancellation techniques with the advantages and disadvantages of each technique compared. This article also discusses the full-duplex medium access control protocol design to address critical issues, such as the problem of hidden terminals, the resultant end-to-end delay and the high packet loss ratio due to network congestion. Furthermore, the survey discusses a range of critical issues related to the implementation, performance enhancement and optimization of full-duplex systems, including important topics such as hybrid full-duplex/half-duplex scheme, optimal relay selection and optimal power allocation, etc. Finally, this survey points at a variety of new directions and open problems associated with the full-duplex technology.
S. K. Sharma, T. E. Bogale, L. B. Le, S. Chatzinotas, X. Wang, and B. Ottersten, “Dynamic Spectrum Sharing in 5G Wireless Networks With Full-Duplex Technology: Recent Advances and Research Challenges,” IEEE Communications Surveys & Tutorials, vol. 20, no. 1, pp. 674-707, First Quarter 2018.
This survey provides a comprehensive survey of recent advances in the full-duplex enabled dynamic spectrum sharing in wireless systems, where full-duplex can provide several benefits and possibilities such as concurrent sensing and transmission, concurrent transmission and reception, improved sensing efficiency and secondary throughput, and the mitigation of the hidden terminal problem. This work highlights several potential techniques for enabling full-duplex operation in dynamic spectrum sharing wireless systems, and proposes a novel communication framework to enable concurrent sensing and transmission. Finally, the survey discusses some open research issues and future directions with the objective of stimulating future research efforts in this emerging domain.
K. E. Kolodziej, B. T. Perry, and J. S. Herd, “In-band Full-duplex Technology: Techniques and Systems Survey,” IEEE Transactions on Microwave Theory and Techniques, vol. 67, no. 7, pp. 3025-3041, Jul. 2019.
This tutorial survey offers the most comprehensive collection to date of self-interference cancellation techniques and discusses how all of them could be implement within the different domains of a typical transceiver. In addition, the results of a novel IBFD system study are presented for more than 50 demonstrated communication systems with more than 80 different measurement scenarios. This work analyzes their total isolation performance with respect to center frequency, instantaneous bandwidth, and transmit power. This survey combines these metrics into a new figure of merit, which can be used to propel future research and accelerate the inclusion of IBFD technology within an upcoming wireless standard.
- Special Issues
“Special Issue on In-Band Full-Duplex Wireless Communications and Networks”, IEEE Journal on Selected Areas in Communications, issue 9, September 2014.
“Special Issue on Full Duplex Communications”, IEEE Communications Magazine, vol. 3, issue 5, May 2015.
“Special Issue on Recent Advances in Full-Duplex Radios and Networks”, IEEE Access, vol. 6, June 2018.
“Special Issue on 5G Wireless Systems with Massive MIMO”, IEEE Systems Journal, vol. 11, no. 1, March 2017.
“Special Issue on Full-Duplex (Two-Way) Communication”, IEEE Microwave Magazine, vol. 20, issue 2, February 2019.
“Special Issue on Full Duplex Communications Theory, Standardization and Practice”, upcoming, IEEE Wireless Communications, February 2021.
“Full-Duplex Transceivers for Future Networks: Theory and Techniques”, upcoming, IEEE Open Journal of the Communications Society, Second Quarter 2021.
- Topic: Foundations
S. Chen, M. A. Beach, and J.P. McGeehan, “Division-free Duplex for Wireless Applications,” Electronics Letters, vol. 34, issue 2, January 1998.
Division-free duplex is proposed for future wireless systems, thus providing simultaneous duplex radio transmission on a division-free basis. The required duplex isolation can be achieved by electronic interference cancellation operating at both RF and baseband, with results from an experimental RF system yielding some 72 dB duplex isolation at 1.8 GHz for 200 kHz channelization.
J. I. Choi, M. Jain, K. Srinivasan, P. Levis, and S. Katti, “Achieving Single Channel, Full Duplex Wireless Communication,” ACM MobiCom’10 September 20-24, Chicago, Illinois, USA.
This paper pioneering paper discusses the design of a single channel full-duplex wireless transceiver and reports on experiments on real nodes that demonstrate that the full-duplex prototype achieves median performance that is within 8% of an ideal full-duplexing system
- Topic: Self-Interference Cancellation
A. Sahai, G. Patel, C. Dick, and A. Sabharwal, “On the Impact of Phase Noise on Active Cancelation in Wireless Full-Duplex,” IEEE Transactions on Vehicular Technology, vol. 62, no. 9, pp. 4494-4510, November 2013.
This paper investigates the root cause of performance bottlenecks in full-duplex systems. This work first classifies all known full-duplex architectures based on how they compute their canceling signal and where the canceling signal is injected to cancel self-interference. Based on the classification, they analytically explain several published experimental results. The key bottleneck in current systems turns out to be the phase noise in the local oscillators in the transmit-and-receive chain of the full-duplex node. As a key by-product of our analysis, this work proposes signal models for wideband and MIMO full-duplex systems, capturing all the salient design parameters, thus allowing future analytical development of advanced coding and signal design for full-duplex systems.
D. Korpi, T. Riihonen, V. Syrjälä, L. Anttila, M. Valkama, and R. Wichman, “Full-Duplex Transceiver System Calculations: Analysis of ADC and Linearity Challenges,” IEEE Transactions on Wireless Communications, vol. 13, no. 7, pp. 3821-3836, July 2014.
In this paper, the effect of nonlinear distortion occurring in the transmitter power amplifier and the receiver chain is analyzed, beside the dynamic range requirements of analog-to-digital converters. This is done with detailed system calculations, which combine the properties of the individual electronics components to jointly model the complete transceiver chain, including self-interference cancellation. They also quantify the decrease in the dynamic range for the signal of interest caused by self-interference at the analog-to-digital interface. Using these system calculations, this work provides comprehensive numerical results for typical transceiver parameters. The analytical results are also confirmed with full waveform simulations. We observe that the nonlinear distortion produced by the transmitter power amplifier is a significant issue in a full-duplex transceiver and, when using cheaper and less linear components, also the receiver chain nonlinearities become considerable. It is also shown that, with digitally intensive self-interference cancellation, the quantization noise of the analog-to-digital converters is also significant problem.
- Topic: Experiments and Testbeds
M. Duarte, C. Dick, and A. Sabharwal, “Experiment-Driven Characterization of Full-Duplex Wireless Systems,” IEEE Transactions on Wireless Communications, vol. 11, no. 12, pp. 4296-4307, December 2012.
This paper presents an experiment-based characterization of passive suppression and active self-interference cancellation mechanisms in full-duplex wireless communication systems. First, it shows that the average amount of cancellation increases for active cancellation techniques as the received self-interference power increases. This work’s 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, it shows 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, this paper characterizes the probability distribution of the self-interference channel before and after cancellation.
D. Bharadia, E. McMilin, and S. Katti, “Full Duplex Radios,” Proceedings of ACM Special Interest Group on Data Communication (SIGCOMM), 2013, pp. 375–386.
This paper presents the design and implementation of the first in-band full duplex WiFi radios that can simultaneously transmit and receive on the same channel using standard WiFi 802.11ac and achieves close to the theoretical doubling of throughput in all practical deployment scenarios. It proposes novel analog and digital cancellation techniques that cancels the self-interference to the receiver noise floor. The key technical contributions in this paper are the novel self-interference cancellation circuits and algorithms that provide the required 110dB of self-interference cancellation for standard WiFi signals and thus eliminate all self-interference to the noise floor.
D. Bharadia and S. Katti, “Full Duplex MIMO Radios,” Symposium on Networked Systems Design and Implementation (NSDI), 2014, pp. 359–372.
This paper presents the design and implementation of the first in-band full duplex WiFi-PHY based MIMO. The design solves two fundamental challenges associated with MIMO full duplex: complexity and performance. The design achieves full duplex with a cancellation design whose complexity scales almost linearly with the number of antennas. Furthermore, it also designs novel digital estimation and cancellation algorithms that eliminate almost all interference and achieves the same performance as a single antenna full duplex system. This paper shows experimentally that the design works robustly in noisy indoor environments and provides close to the expected theoretical doubling of throughput in practice.
M. Chung, M. S. Sim, J. Kim, D. K. Kim, and C. Chae, “Prototyping Real-time Full Duplex Radios,” IEEE Communications Magazine, vol. 53, no. 9, pp. 56-63, September 2015.
This paper presents a real-time full duplex radio system for 5G wireless networks. To overcome the self-interference challenge, this article prototypes the design on a software-defined radio platform. This design combines a dual-polarization antenna-based analog part with a digital self-interference canceler that operates in real time. Prototype test results confirm that the proposed full duplex system achieves about 1.9 times higher throughput than a half-duplex system. This article concludes with a discussion of implementation challenges that remain for researchers seeking the most viable solution for full duplex communications.
E. Everett, C. Shepard, L. Zhong, and A. Sabharwal, “SoftNull: Many-Antenna Full-Duplex Wireless via Digital Beamforming,” IEEE Transactions on Wireless Communications, vol. 15, no. 12, pp. 8077-8092, December 2016.
This paper presents and studies a digital-controlled method, called SoftNull, to enable full-duplex in many-antenna systems. Unlike most designs that rely on analog cancelers to suppress self-interference, SoftNull relies on digital transmit beamforming to reduce self-interference. SoftNull does not attempt to perfectly null self-interference, but instead seeks to reduce self-interference sufficiently to prevent swamping the receiver's dynamic range. Residual self-interference is then cancelled digitally by the receiver. This work evaluates the performance of SoftNull using measurements from a 72-element antenna array in both indoor and outdoor environments. SoftNull can significantly outperform half-duplex for small cells operating in the many-antenna regime, where the number of antennas is many more than the number of users served simultaneously.
D. Korpi, M. Heino, C. Icheln, K. Haneda, and M. Valkama, “Compact Inband Full-Duplex Relays With Beyond 100 dB Self-Interference Suppression: Enabling Techniques and Field Measurements,” IEEE Transactions on Antennas and Propagation, vol. 65, no. 2, pp. 960-965, February 2017.
In this paper, the self-interference channel and the novel enabling techniques for a compact in-band full-duplex relay are described and characterized in different operating environments. The full-duplex operation is based on a novel antenna design to provide passive isolation, which is complemented with novel active RF and digital cancellation stages that further suppress the residual SI to the receiver noise floor. Measurement results of a complete prototype implementation show that the proposed design can achieve an overall self-interference cancellation performance of over 100 dB even with an ambitious instantaneous bandwidth of 80 MHz. Similar results are obtained both in an anechoic chamber as well as in realistic multipath indoor environments.
- Topic: 5G Cellular Networks
S. Hong, J. Brand, J. I. Choi, M. Jain, J. Mehlman, S. Katti, and P. Levis, “Applications of Self-interference Cancellation in 5G and Beyond,” IEEE Communications Magazine, vol. 52, issue 2, February 2014.
Self-interference cancellation invalidates a long-held fundamental assumption in wireless network design that radios can only operate in half duplex mode on the same channel. Beyond enabling in-band full duplex, which effectively doubles spectral efficiency, self-interference cancellation tremendously simplifies spectrum management. Not only does it render entire ecosystems it enables future networks to leverage fragmented spectrum. Self-interference cancellation offers the potential to complement and sustain the evolution of 5G technologies toward denser heterogeneous networks and can be utilized in wireless communication systems in multiple ways, including increased link capacity, spectrum virtualization, any-division duplexing, novel relay solutions, and enhanced interference coordination.
X. Xia, K. Xu, Y. Wang, and Y. Xu “A 5G-Enabling Technology: Benefits, Feasibility, and Limitations of In-Band Full-Duplex mMIMO,” IEEE Vehicular Technology Magazine, vol. 13, issue 3, September 2018.
This article presents a smart composition of mMIMO and in-band full-duplex (IBFD), called IBFD mMIMO, as a potential enabling technology for 5G and beyond. IBFD mMIMO can support multiple uplink and downlink users with the same time–frequency resources, and thus substantially enhances spectral efficiency. This article also shows that by exploiting the new degree of freedom provided by IBFD transmission, IBFD mMIMO can alleviate the complexity in the design of base stations due to the large increase in the number of antennas.
- Topic: Medium Access Control
K. M. Thilina, H. Tabassum, E. Hossain, and D. I. Kim, “Medium Access Control Design for Full Duplex Wireless Systems: Challenges and Approaches,” IEEE Communications Magazine, vol. 53, no. 5, pp. 112-120, May 2015.
This article first discusses the fundamental concepts, potential benefits, and primary network topologies of full-duplex transmissions. Then, this work highlights immediate challenges, both in the physical (PHY) and medium access control (MAC) layers, that need to be addressed in designing full-duplex wireless systems. A qualitative comparison among the existing full-duplex MAC (FD-MAC) protocols is then provided. Finally, the primary requirements and research issues for the design of FD-MAC protocols are discussed, and implications of FD technology in cellular wireless networks are highlighted.
S.-Y. Chen, T.-F. Huang, K. C. J. Lin, Y.-W. P. Hong, and A. Sabharwal, “Probabilistic Medium Access Control for Full-Duplex Networks With Half-Duplex Clients,” IEEE Transactions on Wireless Communications, vol. 16, issue 4, April 2017.
The feasibility of practical in-band full-duplex radios has recently been demonstrated experimentally. One way to leverage full-duplex in a network setting is to enable three-node full-duplex, where a full-duplex access point transmits data to one node yet simultaneously receives data from another node. Such three-node full-duplex communication, however, introduces inter-client interference, directly impacting the full-duplex gain. It hence may not always be beneficial to enable three-node full-duplex transmissions. This paper presents a distributed full-duplex medium access control protocol that allows an access point to adaptively switch between full-duplex and half-duplex modes.
K. M. Thilina, H. Tabassum, E. Hossain, and D. I. Kim, “Medium Access Control Design for Full Duplex Wireless Systems: Challenges and Approaches,” IEEE Communications Magazine, Vol. 53, No. 5, May 2015.
Recent advances in self-interference cancellation techniques enable in-band full-duplex (FD) transmission in which a wireless node can simultaneously transmit and receive in the same frequency band. However, to fully exploit the benefits of FD technology in a wireless network, in addition to the physical (PHY) layer issues, medium access control (MAC) layer issues such as inter-node collisions, fairness between half-duplex (HD) and FD users, opportunistic selection of different modes of FD transmission, and synchronization issues need to be resolved. To this end, this article first discusses the fundamental concepts, potential benefits, and primary network topologies of FD transmission. The article then highlights immediate challenges (both in the PHY and MAC layers) that need to be addressed in designing FD wireless systems.
W. Choi, H. Lim, and A. Sabharwal, “Power-Controlled Medium Access Control Protocol for Full-Duplex WiFi Networks,” IEEE Trans. Wireless Comms, Vol. 14, No. 7, July 2015.
Recent advances in signal processing have demonstrated in-band full-duplex capability at WiFi ranges. In addition to simultaneous two-way exchange between two nodes, full-duplex access points can potentially support simultaneous uplink and downlink flows. However, the atomic three-node topology, which allows simultaneous uplink and downlink, leads to inter-client interference. This paper proposes a random-access medium access control protocol using distributed power control to manage inter-client interference in wireless networks with full-duplex-capable access points that serve half-duplex clients.
S. Liu, L. Fu, and W. Xie, “Hidden-Node Problem in Full-Duplex Enabled CSMA Networks,” IEEE Transactions on Mobile Computing, Vol. 19, No. 2, February 2020.
The in-band full-duplexing is a promising technique to boost wireless network throughput by allowing a node to transmit and receive simultaneously. This paper provides a comprehensive investigation on the hidden-node problem that arises in the full-duplex (FD) enabled carrier-sensing multiple-access (CSMA) networks. In particular, the paper provides the fundamental conditions that guarantee successful receptions for all the FD transmission cases and propose an ellipse interference model and an ellipse carrier-sensing model to capture the interference relations and the carrier-sensing mechanism in FD CSMA networks, respectively. It also establishes the hidden-node-free design in FD CSMA networks.
M. Hirzallah, W. Aﬁﬁ, and M. Krunz, “Provisioning QoS in Wi-Fi Systems With Asymmetric Full-Duplex Communications,” IEEE Transactions on Cognitive Communications and Networking, Vol. 4, No. 4, December 2018.
The traffic volume carried by wireless local area networks (WLANs) continues to increase at a rapid pace. Full-duplex communication is a key solution for satisfying the growing traffic demand, enhancing spectrum efficiency, and reducing latency for WLAN users. In this paper, we consider the application of asymmetric full-duplex (AFD) communications in WLANs, exemplified by a Wi-Fi system. Our system model relies on a full-duplex-enabled Wi-Fi access point to simultaneously transmit uplink and downlink to a pair of half-duplex Wi-Fi stations. Providing QoS guarantees in WLANs with AFD communication capabilities is challenging due to inter-node as well as residual self-interference. The heterogeneity of the QoS requirements between paired uplink and downlink stations further complicates the problem. To tackle these challenges, we introduce a framework called AFD-QoS, which incorporates AFD communications in WLANs and supports QoS.
- Topic: Resource Allocation
C. Nam, C. Joo, and S. Bahk, “Joint Subcarrier Assignment and Power Allocation in Full-Duplex OFDMA Networks,” IEEE Transactions on Wireless Communications, vol. 14, no. 6, pp. 3108-3119, June 2015.
This paper considers a single-cell full-duplex OFDMA network with one full-duplex base station and multiple full-duplex mobile nodes. The goal is to maximize the sum-rate performance by jointly optimizing subcarrier assignment and power allocation considering the characteristics of full-duplex transmissions. This work develops an iterative solution that achieves local Pareto optimality in typical scenarios. Through extensive simulations, we demonstrate that our solution empirically achieves near-optimal performance and outperforms other resource allocation schemes designed for half-duplex networks.
Z. Tong and M. Haenggi, “Throughput Analysis for Full-Duplex Wireless Networks With Imperfect Self-Interference Cancellation,” IEEE Transactions on Communications, vol. 63, no. 11, pp. 4490-4500, November 2015.
This paper investigates the throughput of full-duplex communications with using stochastic geometry. It focus on a wireless network of nodes with both half- and full-duplex capabilities and derive and optimize the throughput in such a network. The analytical result shows that if the network is adopting an ALOHA protocol, the maximal throughput is achieved by scheduling all concurrently transmitting nodes to work in either full-duplex mode or half-duplex mode depending on one simple condition. This paper rigorously quantifies the impact of imperfect self-interference cancellation on the throughput gain, transmission range, and other metrics, and it establishes the minimum amount of self-interference suppression needed for full-duplex to be beneficial.
A. AlAmmouri, H. ElSawy, O. Amin, and M. Alouini, “In-Band α-Duplex Scheme for Cellular Networks: A Stochastic Geometry Approach,” IEEE Transactions on Wireless Communications, vol. 15, no. 10, pp. 6797-6812, October 2016.
This paper presents a tractable framework, based on stochastic geometry, to study full-duplex communications in cellular networks by assessing the effects on the network performance and quantifying the associated gains. This paper proves the vulnerability of the uplink to the downlink interference and shows that full-duplex rate gains harvested in the downlink come at the expense of a significant degradation in the uplink rate. It proposes a novel fine-grained duplexing scheme, denoted as the α-duplex scheme, which allows a partial overlap between the uplink and the downlink frequency bands. In particular, the paper shows that the α-duplex scheme provides a simultaneous improvement for the downlink and uplink rate. Finally, it shows that the amount of the overlap can be optimized based on the network design objective.
J. M. B. da Silva, G. Fodor, and C. Fischione, “Spectral Efficient and Fair User Pairing for Full-Duplex Communication in Cellular Networks,” IEEE Transactions on Wireless Communications, vol. 15, no. 11, pp. 7578-7593, November 2016.
This paper investigates the problem of grouping users to pairs and assigning frequency channels to each pair in a spectral efficient and fair manner. Specifically, the joint problem of user uplink/downlink frequency channel pairing and power allocation is formulated as a mixed integer nonlinear problem that is solved by a novel joint fairness assignment maximization algorithm. Realistic system-level simulations indicate that the spectral efficiency of the users having the lowest spectral efficiency is increased by the proposed algorithm, while a high ratio of connected users in different loads and self-interference levels is maintained.
J. Marašević, J. Zhou, H. Krishnaswamy, Y. Zhong, and G. Zussman, “Resource Allocation and Rate Gains in Practical Full-Duplex Systems,” IEEE/ACM Transactions on Networking, vol. 25, no. 1, pp. 292-305, February 2017.
This paper characterizes the full-duplex rate gains in both single-channel and multi-channel use cases. For the single-channel case, it quantifies the rate gain as a function of the remaining self-interference and signal-to-noise ratio values. This work provides a sufficient condition under which the sum of uplink and downlink rates on a full-duplex channel is biconcave in the transmission power levels. For the multi-channel case, it introduce a new realistic model of a compact full-duplex receiver and demonstrate its accuracy via measurements. This work studies the problem of jointly allocating power levels to different channels and selecting the frequency of maximum SI suppression, where the objective is to maximize the sum of the rates over uplink and downlink orthogonal frequency division multiplexing channels. Finally, it demonstrates via numerical evaluations the capacity gains in different use cases and obtain insights into the impact of the remaining SI and wireless channel states on the performance.
S. Goyal, P. Liu, and S. S. Panwar, “User Selection and Power Allocation in Full-Duplex Multicell Networks,” IEEE Transactions on Vehicular Technology, vol. 66, no. 3, pp. 2408-2422, March 2017.
This paper proposes a distributed resource allocation, including joint user selection and power allocation for a full-duplex multi-cell system, assuming full-duplex base stations and half-duplex users. Due to the complexity of finding the globally optimum solution, a suboptimal solution for user selection and a novel geometric-programming-based solution for power allocation are proposed. It provides a hybrid scheduling policy that allows full-duplex operations whenever it is advantageous. With practical self-interference cancelation, it shows that the proposed hybrid full-duplex system achieves high throughput improvement for indoor and outdoor multi-cell scenarios when compared with the half-duplex system.
- Topic: Resource Allocation for MIMO
D. Nguyen, L. Tran, P. Pirinen, and M. Latva-aho, “Precoding for Full Duplex Multiuser MIMO Systems: Spectral and Energy Efficiency Maximization,” IEEE Transactions on Signal Processing, vol. 61, no. 16, pp. 4038-4050, August 15, 2013.
This paper explores the potential gains in terms of the spectral efficiency and energy efficiency that the full-duplex multi-user MIMO model may provide. Toward this end, it proposes low-complexity designs for maximizing the spectral efficiency and energy efficiency, and evaluate their performance numerically. Numerical results demonstrate that compared to a half-duplex system, the full-duplex system with the proposed designs achieves a better spectral efficiency and a slightly smaller energy efficiency when the self-interference is small.
A. C. Cirik, Y. Rong, and Y. Hua, “Achievable Rates of Full-Duplex MIMO Radios in Fast Fading Channels With Imperfect Channel Estimation,” IEEE Transactions on Signal Processing, vol. 62, no. 15, pp. 3874-3886, August 2014.
This paper studies the theoretical performance of two full-duplex MIMO systems: a full-duplex bi-directional communication system and a full-duplex relay system. This work assumes that the instantaneous channel state information is not available at the transmitters and aims to maximize the system ergodic mutual information. Numerical results indicate that the full-duplex mode is optimal when the nominal self-interference is low, and the half-duplex mode is optimal when the nominal self-interference is high. In addition to an exact closed-form ergodic mutual information expression, this work introduces a much simpler asymptotic closed-form ergodic mutual information expression, which in turn simplifies the computation of the power allocation.
D. Nguyen, L. Tran, P. Pirinen, and M. Latva-aho, “On the Spectral Efficiency of Full-duplex Small Cell Wireless Systems,” IEEE Transactions on Wireless Communications, vol. 13, no. 9, pp. 4896-4910, September 2014.
This paper investigates the spectral efficiency of full-duplex small cell wireless systems, in which a full-duplex capable base station sends/receives data to/from multiple half-duplex users on the same system resources. The objective is a joint beamformer design to maximize the spectral efficiency subject to certain power constraints. To obtain suboptimal solutions, it proposes two provably convergent algorithms. Extensive numerical experiments under small cell setups illustrate that the full-duplex system with the proposed algorithms can achieve a large gain over the half-duplex system.
A. C. Cirik, “Fairness Considerations for Full Duplex Multi-User MIMO Systems,” IEEE Wireless Communications Letters, vol. 4, no. 4, pp. 361-364, August 2015.
This paper addresses the proportional fairness issue of a cellular system with a full-duplex base station “erving multiple users simultaneously, where all the nodes are equipped with multiple antennas. The sum of the logarithm of the achievable rate of UL and DL users is maximized subject to power constraints at the BS and UL users. The numerical results indicate that the proposed algorithm provides a good balance between maximizing the sum-rate and maintaining fairness among users.
D. W. K. Ng, Y. Wu, and R. Schober, “Power Efficient Resource Allocation for Full-Duplex Radio Distributed Antenna Networks,” IEEE Transactions on Wireless Communications, vol. 15, no. 4, pp. 2896-2911, April 2016.
This paper studies resource allocation for distributed antenna multiuser networks with full-duplex radio base stations with multiple users. The considered resource allocation algorithm design is formulated as an optimization problem taking into account the antenna circuit power consumption of the BSs and the quality of service requirements of both uplink and downlink users. The objective is to minimize the total network power consumption by jointly optimizing the downlink beamformer, the uplink transmit power, and the antenna selection. The results illustrate the tradeoff between power efficiency and the number of active transmit antennas when considering the circuit power consumption. In particular, activating an exceedingly large number of antennas may not be an efficient approach for reducing the total system power consumption. In addition, the results reveal that full-duplex systems facilitate significant power savings compared to traditional half-duplex systems, despite the non-negligible self-interference.
C. Psomas, M. Mohammadi, I. Krikidis, and H. A. Suraweera, “Impact of Directionality on Interference Mitigation in Full-Duplex Cellular Networks,” IEEE Transactions on Wireless Communications, vol. 16, no. 1, pp. 487-502, January 2017.
This paper considers two fundamental full-duplex architectures, two-node and three-node, in the context of cellular networks where the terminals employ directional antennas. Using a stochastic geometry model, it investigates how directional antennas can control and mitigate the co-channel interference in large-scale multi-cell networks. Furthermore, it provides a model that characterizes the way directional antennas manage the self-interference in order to suppress it. The results show that both architectures can benefit significantly by the employment of directional antennas. Finally, the paper derives the optimal values for the density fraction of each architecture that maximize the success probability and the network throughput.
- Topic: Relaying
T. Riihonen, S. Werner, and R. Wichman, “Hybrid Full-Duplex/Half-Duplex Relaying with Transmit Power Adaptation,” IEEE Transactions on Wireless Communications, vol. 10, no. 9, pp. 3074-3085, September 2011.
Focusing on two-antenna infrastructure relays employed for coverage extension, this paper develops hybrid techniques that switch opportunistically between full-duplex and half-duplex relaying modes. It proposes the combination of opportunistic mode selection and transmit power adaptation for maximizing instantaneous and average spectral efficiency after noting that the trade-off favors alternately the modes during operation. The analysis covers both common relaying protocols (amplify-and-forward and decode-and-forward) as well as reflects the difference of downlink and uplink systems. The results show that opportunistic mode selection offers significant performance gain over system design that is confined to either mode without rationalization.
T. Riihonen, S. Werner, and R. Wichman, “Mitigation of Loopback Self-Interference in Full-Duplex MIMO Relays,” IEEE Transactions on Signal Processing, vol. 59, no. 12, pp. 5983-5993, December 2011.
This paper analyzes a broad range of MIMO mitigation schemes: natural isolation, time-domain cancellation, and spatial suppression. Cancellation subtracts replicated interference signal from the relay input while suppression reserves spatial dimensions for receive and transmit filtering. Spatial suppression can be achieved by antenna subset selection, null-space projection, i.e., receiving and transmitting in orthogonal subspaces, or joint transmit and receive beam selection to support more spatial streams by choosing the minimum eigenmodes for overlapping subspaces. In addition, filtering can be employed to maintain the desired signal quality, which is inherent for cancellation, and the combination of time- and spatial-domain processing may be better than either alone. The performance of mitigation schemes is evaluated and compared by simulations, and the results confirm that self-interference can be mitigated effectively also in the presence of imperfect side information.
B. P. Day, A. R. Margetts, D. W. Bliss, and P. Schniter, “Full-Duplex MIMO Relaying: Achievable Rates Under Limited Dynamic Range,” IEEE Journal on Selected Areas in Communications, vol. 30, no. 8, pp. 1541-1553, September 2012.
This paper considers the problem of full-duplex MIMO relaying between multi-antenna source and destination nodes. The principal difficulty in implementing such a system is that, due to the limited attenuation between the relay's transmit and receive antenna arrays, the relay's outgoing signal may overwhelm its limited-dynamic-range input circuitry, making it difficult, if not impossible, to recover the desired incoming signal. While explicitly modeling transmitter/receiver dynamic-range limitations and channel estimation error, this work derives tight upper and lower bounds on the end-to-end achievable rate of decode-and-forward-based full-duplex MIMO relay systems, and propose a transmission scheme based on maximization of the lower bound. To gain insights into system design tradeoffs, it derives an analytic approximation to the achievable rate and numerically demonstrate its accuracy. Then, this paper studies the behavior of the achievable rate as a function of signal-to-noise ratio, interference-to-noise ratio, transmitter/receiver dynamic range, number of antennas, and training length, using optimized half-duplex signaling as a baseline.
I. Krikidis, H. A. Suraweera, P. J. Smith, and C. Yuen, “Full-Duplex Relay Selection for Amplify-and-Forward Cooperative Networks,” IEEE Transactions on Wireless Communications, vol. 11, no. 12, pp. 4381-4393, December 2012.
This paper focuses on the relay selection problem in amplify-and-forward cooperative communication with full-duplex operation. Different relay selection schemes assuming the availability of different instantaneous information are studied. This work considers optimal relay selection that maximizes the instantaneous full-duplex channel capacity and requires global channel state information as well as several sub-optimal relay selection policies that utilize partial channel. To facilitate comparison, this paper derives exact outage probability expressions and asymptotic approximations of these policies that show a zero diversity order. In addition, an optimal relay selection procedure that incorporates a hybrid relaying strategy, which dynamically switches between full-duplex and half-duplex relaying according to the instantaneous channel state information, is also investigated.
H. A. Suraweera, I. Krikidis, G. Zheng, C. Yuen, and P. J. Smith, “Low-Complexity End-to-End Performance Optimization in MIMO Full-Duplex Relay Systems,” IEEE Transactions on Wireless Communications, vol. 13, no. 2, pp. 913-927, February 2014.
This paper deals with the deployment of full-duplex relaying in amplify-and-forward cooperative networks with multiple-antenna terminals. In contrast to previous studies, which focus on the spatial mitigation of the self-interference at the relay node, this work investigates a joint precoding/decoding design that maximizes the end-to-end performance. To reduce system complexity, the antenna selection problem for full-duplex amplify-and-forward cooperative systems is discussed. To facilitate comparison, this work provides exact outage probability expressions and asymptotic approximations of the proposed schemes. In order to overcome zero-diversity effects associated with the antenna selection operation, a simple power allocation scheme at the relay node is also investigated and its optimal value is analytically derived. Numerical and simulation results show that the joint precoding significantly improves end-to-end performance, while antenna selection schemes are efficient solutions for scenarios with strict computational constraints.
H. Q. Ngo, H. A. Suraweera, M. Matthaiou, and E. G. Larsson, “Multipair Full-Duplex Relaying With Massive Arrays and Linear Processing,” IEEE Journal on Selected Areas in Communications, vol. 32, no. 9, pp. 1721-1737, September 2014.
This paper considers a multi-pair decode-and-forward relay channel with the help of a full-duplex relay station equipped with massive MIMO, while all sources and destinations have a single antenna. To reduce the self-interference, it proposes two techniques: using a massive receive antenna array or using a massive transmit antenna array together with very low transmit power at the relay station. This work derives exact and approximate achievable rate expressions for several processing techniques. These closed-form expressions enable the determination of the regions where the full-duplex mode outperforms the half-duplex mode, as well as to design an optimal power allocation scheme. Numerical results show that by doubling the number of antennas at the relay station, the transmit power of each source and of the relay station can be reduced by 1.5 dB if the pilot power is equal to the signal power, and by 3 dB if the pilot power is kept fixed, while maintaining a given quality of service.
- Topic: Wireless Power Transfer
H. Ju and R. Zhang, “Optimal Resource Allocation in Full-duplex Wireless-powered Communication Network,” IEEE Transactions on Communications, vol. 62, no. 10, pp. 3528-3540, October 2014.
This paper studies optimal resource allocation in the wireless-powered communication network, where one hybrid access point operating in full duplex broadcasts wireless energy to a set of distributed users in the downlink and receives independent information from the users via time-division multiple access in the uplink. It designs an efficient protocol to support simultaneous wireless energy transfer in the downlink and wireless information transmission in the uplink. This work jointly optimizes the time allocations to the hybrid access point for downlink and different users for uplink and the transmit power allocations over time at the hybrid access point to maximize the users' weighted sum rate of uplink information transmission with harvested energy. Simulation results show that full-duplex outperforms half-duplex when effective self-interference cancellation can be implemented and more stringent peak power constraint is applied at the hybrid access point.
C. Zhong, H. A. Suraweera, G. Zheng, I. Krikidis, and Z. Zhang, “Wireless Information and Power Transfer With Full Duplex Relaying,” IEEE Transactions on Communications, vol. 62, no. 10, pp. 3447-3461, October 2014.
This paper considers a dual-hop full-duplex relaying system, where the energy constrained relay node is powered by radio frequency signals from the source using the time-switching architecture, and both the amplify-and-forward and decode-and-forward relaying protocols are studied. Specifically, this work provides an analytical characterization of the achievable throughput of three different communication modes, namely, instantaneous transmission, delay-constrained transmission, and delay tolerant transmission. In addition, the optimal time split is studied for different transmission modes. The results reveal that, when the time split is optimized, the full-duplex relaying could substantially boost the system throughput compared to the conventional half-duplex relaying architecture for all the transmission modes. In addition, this paper shows that the instantaneous transmission mode attains the highest throughput. Unlike the instantaneous time split optimization, which requires instantaneous channel state information, the optimal time split in the delay-constrained transmission mode depends only on the statistics of the channel, hence, is suitable for practical implementations.
Y. Zeng and R. Zhang, “Full-Duplex Wireless-Powered Relay With Self-Energy Recycling,” IEEE Wireless Communications Letters, vol. 4, no. 2, pp. 201-204, April 2015.
This paper studies a wireless-powered amplify-and-forward relaying system, where an energy-constrained relay node assists the information transmission from the source to the destination using the energy harvested from the source. It proposes a novel two-phase protocol for efficient energy transfer and information relaying, in which the relay operates in full-duplex mode with simultaneous energy harvesting and information transmission. Under the multiple-input single-output channel setup, the optimal power allocation and beamforming design at the relay are derived. Numerical results show a significant throughput gain achieved by the proposed design over the existing time switching based relay protocol.
X. Kang, C. K. Ho, and S. Sun, “Full-Duplex Wireless-Powered Communication Network With Energy Causality,” IEEE Transactions on Wireless Communications, vol. 14, no. 10, pp. 5539-5551, October 2015.
This paper considers a wireless communication network with a full-duplex hybrid energy and information access point and a set of wireless users with energy harvesting capabilities. Each user can continuously harvest wireless power from the hybrid access point until it transmits, i.e., the energy causality constraint is modeled by assuming that energy harvested in the future cannot be used for the current transmission. Under this setup, this work investigates the sum-throughput maximization and the total-time minimization problems. For the sum-throughput maximization, it obtains the optimal solution as a closed-form expression. For the total-time minimization, it proposes a two-step algorithm to obtain an optimal solution. Finally, simulation studies on the effect of user scheduling show that different scheduling strategies should be adopted for the sum-throughput maximization and the total-time minimization.
M. Mohammadi, B. K. Chalise, H. A. Suraweera, C. Zhong, G. Zheng, and I. Krikidis, “Throughput Analysis and Optimization of Wireless-Powered Multiple Antenna Full-Duplex Relay Systems,” IEEE Transactions on Communications, vol. 64, no. 4, pp. 1769-1785, April 2016.
This paper considers a full-duplex decode-and-forward system in which the time-switching protocol is employed by the multi-antenna relay to receive energy from the source and transmit information to the destination. The instantaneous throughput is maximized by optimizing receive and transmit beamformers at the relay and the time-split parameter, in which both optimum and suboptimum schemes are proposed. The results reveal that beamforming increases both the energy harvesting and self-interference suppression capabilities at the full-duplex relay. Moreover, simulation results show that the choice of the linear processing scheme as well as the time-split plays a critical role in determining the full-duplex gains.
V. Nguyen, T. Q. Duong, H. D. Tuan, O. Shin, and H. V. Poor, “Spectral and Energy Efficiencies in Full-Duplex Wireless Information and Power Transfer,” IEEE Transactions on Communications, vol. 65, no. 5, pp. 2220-2233, May 2017.
This paper considers a full-duplex multiple-antenna base station and multiple single-antenna downlink and uplink users, where the latter need to harvest energy for transmitting information to the base station. The communication has two phases, in which the aim is to maximize the sum rate and energy efficiency under the uplink users’ achievable information throughput constraints by jointly optimizing beamforming and time allocation. The proposed algorithms obtain a local optima solution to this problem and iteratively improve the objectives with guaranteed convergence. Simulation results show that they achieve rapid convergence and outperform conventional solutions.
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