New Air Interface Techniques for Future Massive Machine Communications

Lead Research Organisation: University of Surrey
Department Name: Institute of Communications Systems


Future wireless systems are expected to constitute an ultra dense wireless network, which supports billions of smart wireless devices (or machines) to provide a wide varieties of services for smart homes, smart cities, smart transportation systems, smart healthcare, and smart environments, etc., in addition to supporting conventional human-initiated mobile communications. Therefore, the communication technologies employed in future wireless communication systems are expected to be capable of coping with highly diverse service requirements and communication environments, both of which also have time-varying nature. However, the legacy wireless systems, such as LTE/LTE-A, have been primarily designed for human-initiated mobile communications, which rely on strict synchronisation guaranteed by a substantial signalling overhead. Explicitly, due to this overhead legacy systems are inefficient for device-centric mMTC. Furthermore, they are unable to support the massive connectivity required by the future mMTC networks, where devices heavily contend for the limited resources available for communications. This project is proposed at the time, when myriads of smart wireless devices of different types are being deployed and connected via the Internet, which is expected to be the next revolution in the mobile ecosystem. To fulfil these objectives, a new design paradigm is required for supporting the massive number of wireless devices having diverse service requirements and unique traffic characteristics.
In this project, we propose to meet the challenges of future mMTC by investigating and designing novel non-orthogonal multiple access, flexible duplexing, and adaptive coherent-noncoherent transmission schemes, as well as new waveforms that are tailored for the future mMTC systems. We aim for alleviating the strict synchronism demanded by the legacy wireless systems, and for significantly improving their capabilities, network performance as well as the lifetime of autonomous mMTC nodes. The novelties of this project are summarized as follows.
1. New non-orthogonal sparse code multiple access (SCMA) schemes will be developed for mMTC systems, where the number of devices exceeds the number of available resource-slots, resulting in an over-loaded or a generalized rank-deficient condition.
2. Novel multicarrier waveforms will be designed for future mMTC in order to maximize spectrum efficiency by minimizing the overhead for achieving synchronisation as well as for reducing the out-of-band radiation.
3. By jointly exploiting the resources available in the time, frequency and spatial domains, we will design noncoherent, partially-coherent and adaptive coherent-noncoherent transmission schemes, in order to strike the best possible trade-off among overhead reduction, energy and spectral efficiency, latency and implementation complexity in practical mMTC scenarios.
4. We will investigate the full potential of the multicarrier-division duplex (MDD) scheme and, especially, its applications to future mMTC by synergistically combining it with novel multicarrier waveforms, non-orthogonal SCMA techniques and other high-efficiency transmission schemes developed within the project.
5. Furthermore, the key techniques developed in the project will be prototyped and integrated into the 5G Innovation Centre (5GIC) test bed facilities at the University of Surrey. This will allow us to demonstrate the viability of our new design approaches, as well as to accelerate knowledge transfer and commercialisation.
The proposed research will be conducted jointly by the 5GIC at the University of Surrey and Southampton Wireless (SW) at the University of Southampton, led by Xiao, Tafazolli, Yang & Hanzo. The research and commercial exploitation of the project will be further consolidated by our partnership with experienced academic and industrial partners.

Planned Impact

This project is proposed at the time when a massive number of smart devices/machines of different types are being deployed and connected via the Internet. The Internet-of-everything is predicted to be the next revolution in the mobile ecosystem. The legacy wireless systems were primarily designed for human-initiated mobile communications, but they are inefficient for device-centric machine-type communications. Furthermore, the existing wireless systems cannot support the massive connectivity required by future mMTC networks. Therefore, we need fundamental re-thinking of how the future device-centric mMTC systems are designed and operated. This may require a paradigm shift and significant departure from the current design philosophy. To the best of our knowledge, EPSRC has not yet funded any project in this important area. In this project, we propose to meet these challenges by novel non-orthogonal multiple access, flexible duplexing, adaptive coherent-noncoherent schemes, as well as new waveforms that are tailored for future mMTC systems. These techniques aim for the best exploitation of the available resources, minimum energy consumption, lowest implementation complexity, and most flexible as well as reliable operation. Their successful implementation will unlock the potential of connecting billions of devices and developing novel products as well as new types of services. Hence, beyond the academic beneficiaries, the technical solutions developed by the project will generate profound economic and social impact. The research results will be beneficial to the industry specialising in the development of smart wireless devices for various purposes, such as those for home monitoring, smart cities, V2X communications, environmental monitoring, healthcare, safety and security, etc. The general public will also benefit from the improved services in terms of enhanced efficiency, ubiquitous and massive connectivity, seamless service coverage and system sustainability, energy saving, etc. The mobile operators can promote their business and glean a higher revenue by exploiting the new technologies. Consequently, the research outputs are likely to enhance the UK's economic competitiveness and academic standing, as well as the quality of life of its residents. They also provide opportunities for industry, such as our industrial partners, to develop innovative products and services.
As described in the Academic Beneficiaries section, the research outputs from this collaborative project will have a substantial impact on communication theory, signal processing, optimization theory, information theory, and wireless networking theory, through different dissemination routes. Considering the novel aspects in theory, applications and practical implementation, this project will inspire industrially relevant research, as well as encourage academic-industrial collaboration. Furthermore, it will boost the profiles of the 5GIC and SW, enhance their research income through follow-on research projects and industrial consultancy. Those impacts will augment the UK's research reputation in the above fields by citation of the research publications generated by the project. Additionally, by invoking the research outputs in the two institutions' educational programs at both undergraduate and graduate levels, we will further establish the UK as a world leader in knowledge transfer.
The opportunities arising from this project for research training will establish an inter-institutional team with excellence in mMTC, and educate a new generation of leadership in this future-proof field. The outcomes from the project have the potential to attract more researchers world-wide to the relevant field, which will accelerate the research and deployment of mMTC systems in practice.


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Cao A (2020) A Tight Upper Bound for Enhanced DCT-OFDM With Index Modulation in IEEE Transactions on Vehicular Technology

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Han S (2019) Energy-Efficient Short Packet Communications for Uplink NOMA-Based Massive MTC Networks in IEEE Transactions on Vehicular Technology

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Lai K (2019) Codeword Position Index Based Sparse Code Multiple Access System in IEEE Wireless Communications Letters

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Lai K (2019) Secure Transmission With Interleaver for Uplink Sparse Code Multiple Access System in IEEE Wireless Communications Letters

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Liu Y (2020) Spatial Modulated Multicarrier Sparse Code-Division Multiple Access in IEEE Transactions on Wireless Communications

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Liu Z (2019) Low-PAPR Preamble Design for FBMC Systems in IEEE Transactions on Vehicular Technology

Description 1) From our theoretical study, we realized that the diversity gain plays a major part in the performance of SCMA systems. This motivates us to remove the sparsity constraint and design dense codebook, which can provide significant performance improvements.
2) We designed an equal protection mechanism in SCMA systems by utilizing the fact that not all the transmitted bits are equally important. This requires joint design of SCMA codebook and LDPC code, and this joint design approach brings significant gain in performance.
3) The codebooks in SCMA serve as private keys which are shared by legitimated users and unknown to evasdroppers, thus SCMA thus inherent security mechanism to be utilized for secure communications without any added signal processing complexity and signalling overhead.
4) The sparse graph and LDPC and SCMA can be combined into a joint sparse graph to enable joint multiuser detection and channel decoding, leading to reduced complexity and processing latency.
5) The index of SCMA codeword position can be utilized to transmit additional information.
6) SCMA receiver complexity can be reduced by 1) replacing massage passing algorithm (MPA) with expectation propagation algorithm (EPA); 2) deep learning techniques.
7) Diversity of SCMA system can be further enhanced by frequency hoping.
8) The performance of SCMA codebook can be enhanced by choosing mother constellation which is capacity-approaching, such as golden angle modulation (GAM).
Exploitation Route The findings can help us design algorithms to support more users/devices for 5G/6G massive-IoT applications.
Sectors Digital/Communication/Information Technologies (including Software)

Description SCMA and Grant-Free Multiple Access Technical
Amount £241,000 (GBP)
Organisation Huawei Technologies 
Sector Private
Country China
Start 05/2019 
End 05/2020
Description Design of Non-Orthogonal Multiple Access (NOMA) Systems for Future Vehicular Communications. 
Organisation Indraprastha Institute of Information Technology Delhi
Country India 
Sector Academic/University 
PI Contribution This is a joint research project sponsored by Scheme for Promotion of Academic and Research Collaboration (SPARC), aiming to develop the next generation technologies to support future vehicular communications.
Collaborator Contribution The funding is provided by SPARC Inida. Our partner IIIT has allocated students to work on the project with us.
Impact This is an interdisciplinar research project covering wireless communications and vehicular automation.
Start Year 2019
Description This invention proposes an unequal error protection (UEP) SCMA codebooks based on cloud partitioning and optimization of the protection levels of the codebooks based on the channel code. It represents a new paradigm for the design of non-orthogonal multiple access (NOMA) systems to support future massive IoT applications. 
IP Reference PCT/CN2018/094693 
Protection Patent granted
Year Protection Granted 2018
Licensed No
Impact The practical significance of this invention lies in the fact that the new design not only improves the system spectrum efficiency, but also reduces the peak-to-average power ratio (PAPR) which is of vital importance for the viability and practical deployment of OFDM based NOMA systems.
Description Dr Zilong Liu's Interview by Futurum Careers 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact This medium report published by Futurum Careers is disseminated to secondary school students across the country. It tells students what the future massive machine type communication is about as well as its exciting applications . It aspires students to dive into the wireless communications field upon graduation from high schools.
Year(s) Of Engagement Activity 2019