Converged Optical and Wireless Access Networks (COALESCE)

Lead Research Organisation: University College London
Department Name: Electronic and Electrical Engineering


For most users today, connecting to the Internet ("access") is done wirelessly, either by WiFi or mobile data networks. Yet the unseen high-speed backbone of the Internet depends almost exclusively on fibre optic networks. To provide the higher data rate wireless access demanded by users to support increasingly sophisticated services and applications, wireless cell sizes must be reduced, presenting numerous challenges.

One such challenge is how to distribute the signals to each radio access point. This problem will be exacerbated in future wireless networks operating at higher carrier frequencies in the millimetre-wave or sub-terahertz bands, due to greatly reduced propagation distances at these frequencies. One solution is to use radio-over-fibre techniques, using optical fibre to connect the central office or base station to the access points. Thus, the optical fibre will be pushed closer to the user, with radio providing only the final, short hop. As an alternative to radio, an optical signal could be used to make that last wireless link (optical wireless access), producing a scenario where the interconnection between the optical network and the wireless access is even more seamless.

Another challenge brought about by the increased number of access points is that of energy consumption. Indeed, the biggest - and growing - contribution to energy consumption in the communications network is in the area of wireless access. Connecting the optical and wireless networks together in as seamless a manner as possible would offer advantages by reducing the energy lost in converting optical signals into wireless transmissions.

This project aims to bring together key groups already carrying out work on various aspects of wireless access and optical networking. It will create a physical network to interconnect existing test-beds at the different universities, using an established research optical network - the National Dark Fibre Infrastructure Service. This will foster collaboration between the groups with their complementary expertise and encourage cross-fertilisation of ideas, with the aim of finding optimal solutions for different wireless access scenarios. Beyond the physical network of test-beds, it is planned that this consortium will form the core of a Network of Excellence of researchers working in this area, which will encourage and promote collaboration with and between other university and industrial groups, both in the UK and internationally.

Planned Impact

The research enabled by this project is expected to have impact in the following areas:

Knowledge will be created as a direct result of the research, and this will be disseminated through publication in high-quality, high-impact scientific journals and at major international conferences in the subject area, as well as through annual workshops organised as part of the project. These routes will allow us to engage with other academic researchers in the field, both from the UK and internationally, and with industry, for instance mobile network operators, with an interest in the topic. It is through this route that we expect to attract other researchers to collaborate with and become users of the network of interconnected test-beds formed by the project. Major findings and developments will be publicised through media channels directed at a wider audience, such as specialist magazines, and a website for the consortium will be set up and regularly updated.

People will be trained and developed as a result of the project, particularly PhD students and post-doctoral researchers, helping to create a skilled workforce in this important area for the future. In addition, a major aim of the project is to encourage formal and informal collaborations and networks to be formed in the area of wireless and optical access networks, bringing together researchers from both academia and industry, and resulting in the development of future projects and products.

Society will benefit through the provision of an improved communication infrastructure for private customers and businesses, with potential impacts on e-commerce, entertainment, healthcare and government services. It is anticipated that the outcomes of the project will help inform standards activities. The UK will also benefit from the development of skilled workers through training enabled by the consortium and associated projects.

Economically, the market for wireless access technologies is expected to be in excess of $1 billion pa within the next 15 years. In order to exploit the economic potential of the research enabled by the consortium, opportunities for patenting, intellectual property licencing, and the formation of spin-out companies will be actively pursued. Members of the project consortium have a proven track record in this area, being the inventors on over 40 patents and having founded several successful start-up companies.


10 25 50
Description National Dark Fibre Facility
Amount £4,900,552 (GBP)
Funding ID EP/S028854/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 03/2019 
End 05/2024
Description Collaboration with NPL on metrology for THz communication 
Organisation National Physical Laboratory
Country United Kingdom 
Sector Academic/University 
PI Contribution Co-funded a PhD student, who was collocated on both side. A particular interest in measurement and impact of phase noise on wireless THz links. This has led to important contribution to the field and developments in coherent digital THz wireless link fully transparent to optical networks.
Collaborator Contribution NPL funded half of the PhD fees and stipend, gave access to their laboratory for measurements of spectrum and lend an interferometer to UCL. Further, NPL co-supervised the PhD student and gave advise on measurements, metrology and traceability.
Impact Luis Gonzalez-Guerrero, Haymen Shams, Irshaad Fatadin, Member, IEEE, Martyn J. Fice, Member, IEEE, Mira Naftaly, Alwyn J. Seeds, Fellow, IEEE, and Cyril C. Renaud, "Single sideband signals for phase noise mitigation in wireless THz-over-fibre systems," Journal of Lightwave Technology, Vol. 35, 2018 Luis Gonzalez-Guerrero, Haymen Shams, Irshaad Fatadin, Martyn Fice, Mira Naftaly, Alwyn Seeds, Cyril Renaud, "Spectrally Efficient SSB signals for W-band Links Enabled by Kramers-Kronig Receiver," Optical Fiber Communication Conference, San Diego, 2018 L. Gonzalez-Guerrero, H. Shams, M. J. Fice, A. J. Seeds, I. Fatadin, M. Naftaly, F. Van Dijk, C. C. Renaud, "Experimental Investigation of Phase Noise Tolerance of SSB THz Signals," IEEE Topical meeting on Microwave Photonics, MWP 2017, Beijing, China, 2017 L. Gonzales-Guerrero, H. Sjams, M. J. Fice, A. J. Seeds, M. Naftaly, C. C. Renaud, "Experimental investigation for laser linewidth tolerance on photonic THz wireless systems using PE algorithms," Optical Terahertz Science and Technology, OTST 2017, London 2017 L. Gonzalez-Guerrero, H. Shams, M. J. Fice, A. J. Seeds, F. van Dijk, C. C. Renaud, "Linewidth Tolerance for THz Communication Systems Using Phase Estimation Algorithm," IEEE Topical meeting on Microwave Photonics, MWP 2016, Long Beach, US, 2016.
Start Year 2015
Description Harnessing Quantum-Computing & Signal Processing in Wireless Communications 
Organisation Indian Institute of Technology Madras
Country India 
Sector Academic/University 
PI Contribution We published several joint 4* papers, which contribute to the REF;
Collaborator Contribution Deriving closed-form equations for characterizing device-to-device communications and IoT
Impact mathematics, information theory, signal processing, computer science, telecommunications engineering
Start Year 2017