MIMO Wireless Networks: A Promising Rate Splitting Transceiver Architecture

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Engineering

Abstract

Wireless communications have enabled a plethora of novel applications in recent years thanks to the continuous research efforts to increase the spectral efficiency (SE) and energy efficiency (EE) of wireless networks. Multi-antenna (MIMO) processing plays a central part towards harnessing those gains. MIMO has grown much beyond the original point-to-point channel and can nowadays refer to a diverse range of centralized and distributed deployments (e.g. multi-cell MIMO, cooperative/coordinated MIMO, distributed MIMO, massive MIMO, network MIMO).
The fundamental bottleneck towards enormous spectral and energy efficiency benefits in multiuser MIMO networks lies in a huge demand for accurate channel state information at the transmitter (CSIT). This has become increasingly difficult to satisfy due to the increasing number of antennas and access points in next generation wireless networks relying on very dense heterogeneous networks and transmitters equipped with a very large number of antennas. CSIT inaccuracy results in a multi-user interference that significantly degrades the network performance.
Looking backward, the problem has been to strive to apply techniques designed for perfect CSIT to scenarios with imperfect CSIT. The motivation behind this project is the following: wouldn't it be wiser to design wireless networks from scratch accounting for imperfect CSIT?
In this project, we leverage recent progress in information theory and initial results by the PIs to address the above fundamental CSIT problem (and its resulting multi-user interference) by introducing a rate-splitting (RS) network architecture. Contrary to current approaches where transmission is operated in a broadcast manner with one private message per user, the approach considered consists in splitting one receiver's message into a common and a private part and superposing this common message on top of all users' private messages. The common message is decoded by all users but intended to only one of the users. Such approach has recently been found to be optimal from an information theoretic perspective in a multiuser deployment with imperfect CSIT and significant enhancements over conventional approaches in terms of spectral efficiency and power utilization have been demonstrated by the PIs.
This visionary project conducted at Imperial College London and University of Edinburgh by leading experts in wireless communication theory aims at leveraging those recent findings to design and demonstrate the suitability of an RS-based MIMO wireless network architecture in a multitude of scenarios.
To put together this novel wireless network solution in a credible fashion, this project focuses on designing 1) RS for a single transmission point, 2) RS for a large number of co-localized antennas (also called Massive MIMO) in microwave and millimeter-wave bands, 3) RS for a large number of distributed antennas representative of dense heterogeneous networks, 4) RS for multi-antenna relay channel and finally 5) evaluating the system level performance of RS-based networks.
The project will be performed in partnership with leaders in equipment manufacturing and standardization (Toshiba and InterDigital) and in defence and emergency services (Qinetiq). The project demands a strong track record in wireless communication, MIMO signal processing, optimization, information theory and it is to be conducted in a unique research group with a right mix of theoretical and practical skills. With the above and given the novelty and originality of the topic, the research outcomes will be of considerable value to transform the future of wireless and give the industry a fresh and timely insight into the development of robust MIMO wireless networks, advancing UK's research profile of both wireless communication in the world. Its success would radically change the design of the physical layer of wireless communication systems and have a tremendous impact on standardization.

Publications

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Basnayaka D (2019) Doppler Effect Assisted Wireless Communication for Interference Mitigation in IEEE Transactions on Communications

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Biswas S (2019) An Analysis on Caching Placement for Millimeter-Micro-Wave Hybrid Networks in IEEE Transactions on Communications

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Biswas S (2018) Coexistence of MIMO Radar and FD MIMO Cellular Systems With QoS Considerations in IEEE Transactions on Wireless Communications

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Papazafeiropoulos A (2018) Rate-Splitting Robustness in Multi-Pair Massive MIMO Relay Systems in IEEE Transactions on Wireless Communications

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Papazafeiropoulos A (2017) Rate-Splitting to Mitigate Residual Transceiver Hardware Impairments in Massive MIMO Systems in IEEE Transactions on Vehicular Technology

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Papazafeiropoulos A (2018) Modeling and Performance of Uplink Cache-Enabled Massive MIMO Heterogeneous Networks in IEEE Transactions on Wireless Communications

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Singh K (2018) Transceiver Design and Power Allocation for Full-Duplex MIMO Communication Systems With Spectrum Sharing Radar in IEEE Transactions on Cognitive Communications and Networking

 
Description In this work, we focus on a realistic massive multiple-input single-output broadcast channel hampered by the inevitable hardware impairments. We consider a general experimentally validated model of hardware impairments, accounting for the presence of multiplicative distortion due to phase noise, additive distortion noise and thermal noise amplification. Under both scenarios with perfect and imperfect channel state information at the transmitter (CSIT), we analyze the potential robustness of RS to each separate hardware imperfection. We analytically assess the sum-rate degradation due to hardware imperfections. Interestingly, in the case of imperfect CSIT, we demonstrate that RS is a robust strategy for multiuser MIMO in the presence of phase and amplified thermal noise, since its sum-rate does not saturate at high signal-to-noise ratio (SNR), contrary to conventional techniques. On the other hand, the additive impairments always lead to a sum-rate saturation at high SNR, even after the application of RS. However, RS still enhances the performance. Furthermore, as the number of users increases, the gains provided by RS decrease not only in ideal conditions, but in practical conditions with residual transceiver hardware impairments as well. Notably, although a deterministic equivalent analysis is employed, the analytical and simulation results coincide even for finite system dimensions. As a consequence, the applicability of these results also holds for current "small scale" multiantenna systems.
Exploitation Route Our finding may influence the future wireless standard and products.
We are currently working with local industry Calnex and international telecom industry Huawei and exploiting our research knowledge. Also including the research finding in our teaching syllabus (Advanced wireless communications and Array Signal Processing and MIMO).
Sectors Digital/Communication/Information Technologies (including Software),Education

URL http://www.profratnarajah.org/
 
Description We are currently working with local industry Calnex and international telecom industry Huawei and exploiting our research knowledge. Also including the research finding in our teaching syllabus (Advanced wireless communications and Array Signal Processing). Obtained industry funding from Huawei - £230K.
First Year Of Impact 2019
Sector Digital/Communication/Information Technologies (including Software),Education
 
Description Organising a one day workshop at the IEEE 81st Vehicular Technology Conference: VTC2015-Spring, Glasgow, Scotland, 11-14 May 2015 
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 Organising a one day workshop at the IEEE 81st Vehicular Technology Conference: VTC2015-Spring, Glasgow, Scotland, 11-14 May 2015.
The workshop title is "International Workshop on Emerging MIMO Technologies in 5G Wireless Cellular Networks"
Year(s) Of Engagement Activity 2015