Unlocking Potentials of MIMO Full-duplex Radios for Heterogeneous Networks (UPFRONT)

Lead Research Organisation: Loughborough University
Department Name: Wolfson Sch of Mech, Elec & Manufac Eng


This project will develop multi-antenna full-duplex technology to achieve highly efficient spectrum usage in HetNets (heterogeneous networks). Full-duplex radios are much more than just doubling the capacity as perceived in current literature. More explicitly speaking, we believe that it is making communication technologies impossible become possible. The implications of full-duplex communications are transformative. Full duplex, which permits simultaneous transmission and reception, motivates a fundamental rethinking of the ways wireless networks are designed and optimised.

However, the fact that the power of the transmitting signal is so much larger (over 100 dB) than that of the receiving signal has fuelled the belief that it is impossible to separate them on a single channel. Recently, this picture has begun to change, following the pioneering work by Choi et al. from Stanford University who demonstrated a working full-duplex radio on a single channel.

We envisage that full-duplexing can transform the operations of wireless networks and is expected to have massive benefits in HetNets. HetNets are widely regarded as one key wireless technology for the provision of future wireless communications (including 5G) by complex interoperation between macrocells and small cells. The enormous interest for HetNets is due to their capability of providing high regional capacities and flexible coverage, and more importantly their low infrastructure costs. In HetNets, a mosaic of wireless coverage is obtained by a variety of wireless coverage zones from macrocell to small cell such as, pico- and femtocell. Of increasing interest to mobile operators are the customers' installed femtocells that can greatly improve indoor coverage but share the same frequency band as the macrocells. There is a huge scope of research in resource allocation and physical-layer design and optimisation in HetNets.

This project will exploit the full potential of MIMO full-duplexing in HetNets by designing a holistic solution that interconnects antenna design, physical-layer signal processing, and network resource allocation to address the inherent challenges of full-duplexing and realise its massive end-to-end benefits. To achieve this goal, UPFRONT first proposes new antenna design specially for wideband MIMO full-duplexing, which is substantially more challenging than the existing narrowband single-antenna case. Next we leverage the powerful MIMO signal processing to handle the overlooked in-tercell interference and new interference introduced by the full-duplex operation, which are critical to deliver the end-to-end benefits of full-duplex HetNets but were not well studied before. Furthermore, UPFRONT will explore the unexplored full-duplexing opportunities to address the networking-wide resource allocation challenges associated with the adoption of full-duplexing small cells under the greater macrocell structure sharing the same mobile spectrum. The outcomes of UPFRONT will elucidate the importance of a holistic approach to full-duplexing design and have impact in fundamental and practical research of future wireless networks.


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Description We have made several findings regarding self-interference cancellation and performance of full-duplex cellular networks. These findings includes 1). For SIC, we have investigated the design, isolation, and radiation pattern performance of coaxially fed orthogonally polarized broadband dual rectangular spiral antenna configurations for in-band full duplex communications. We found that at the operating frequency 3.2 GHz within a 60 MHz bandwidth, a very high SIC isolation of 45 dB can be achieved. 2) We provide a theoretical framework for the study of massive multiple-input multiple-output (MIMO)-enabled full-duplex (FD) cellular networks in which the residual self-interference (SI) channels follow the Rician distribution for both uplink (UL) and downlink (DL). The results indicate that the UL rate bottleneck in the FD baseline single-input single-output system can be overcome via exploiting massive MIMO. 3) We recently investigate the optimization of uplink (UL) channel state information (CSI) training in the FD based multiuser MIMO systems. Our results show that the performance of the proposed UL training outperforms the fixed length training and the traditional half-duplex training and it closely matches the performance with an exhaustive search.
Exploitation Route 1) The first finding provides a detailed guideline for the choice of the SIC scheme depending on the bandwidth used. 2) The findings from our performance analysis may be viewed as a reality-check, since we show that, under state-of-the-art system parameters, the spectral efficiency gain of FD massive MIMO over its half-duplex counterpart is largely limited by the cross-mode interference between the DL and the UL. The anticipated twofold increase in SE is shown to be only achievable when the number of antennas tends to be infinitely large. 3) We also investigated the benefit of FD in cloud radio access networks (C-RAN). Our results indicate that significant spectral efficiency gains can be achieved compared to the half duplex operation, particularly in the presence of sufficient-capacity fronthaul links and advanced interference cancellation capabilities.
Sectors Digital/Communication/Information Technologies (including Software)

Description AI-enabled Massive MIMO
Amount £950,863 (GBP)
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 08/2020 
End 08/2022
Description The Leverhulme Trust Research Grant
Amount £199,163 (GBP)
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2018 
End 03/2021
Description Chaired a Workshop in IEEE SPAWC 2016 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Together with the lead PI, Prof. Wong, we organised a special session in IEEE International Workshop on Signal Processing Advances in Wireless Communications in Edinburgh, 2016. We solicited 5 high-quality submissions from top researchers in the area of full-duplex radios. The special session provided a useful venue to exchange ideas, and attracted a large number of audience who attended the conference.
Year(s) Of Engagement Activity 2016