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Dynamically Reconfigurable Optical-Wireless Backhaul/Fronthaul with Cognitive Control Plane for Small Cells and Cloud-RANs

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Fibres weave their threads in 5G wireless

The new 5G wireless revolution will require heterogeneous, flexible solutions to boost network capacity. An EU-funded project has demonstrated novel end-to-end, integrated mobile transport solutions that should help meet the demands of the future 5G use cases.



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Mobile traffic is expected to grow by a factor of 1 000 by 2020 compared to 2010. 5G networks serving this mobile data tsunami will require fronthaul and backhaul solutions aligned with the needs of the new radio access and mobile core networks to cope with this increased traffic load. This new mobile technology will significantly affect both the wireless and the wired sides of the network infrastructure. In view of this challenge, the EU-funded project 5G-XHaul proposed a converged network solution integrating novel optical and wireless technologies to offer end-to-end transport services. “Flexible wireless solutions along with very high-capacity optical interconnects are highly needed for dynamic backhaul and fronthaul architectures. But until now, there had been no consensus on how to efficiently combine both technologies,” notes project coordinator, Prof. Eckhard Grass. Deriving the best of both worlds 5G-XHaul efficiently combines optical and wireless technologies, addressing critical interoperability challenges. The architecture proposed complies both with current and the upcoming 5G mobile networks, addressing end users and operational services. The 5G-XHaul physical architecture consists of a hybrid optical network platform combining both active and passive elements. For the backhaul, researchers implemented wavelength-division multiplexing (WDM) technology additionally supporting elastic and fine granular bandwidth allocation referred to as time-shared optical network (TSON). This elastic optical network is a perfect example of a dynamic-frame-based solution that supports the varying degrees of bandwidth and latency requirements introduced by various radio access network deployments. For the fronthaul, the team implemented WDM over an optical network containing no active components (passive optical network – PON). This WDM-PON solution based on autonomous wavelength tuning transparently carries mobile backhaul and fronthaul traffic through different wavelengths. A wide spectrum of radio access technologies was also deployed to extend the fibre network. Researchers focused on massive multiple-input multiple-output (MIMO) systems, millimetre-wave spectrum as well as sub-6 GHz spectrum technologies. Millimetre-wave technologies use much higher carrier frequencies compared with 4G and Wi-Fi, and in the context of 5G-XHaul, were complementary for backhauling small cells to the macro-cell site. Virtualisation key to the move towards 5G The 5G network will require virtualisation both at the network core and the edge. Network function virtualisation and software-defined networking (SDN) are major steps in this direction. The flexible SDN control plane proposed by 5G-XHaul enables infrastructure that can be partitioned to network slices, each of which can be independently controlled by a different operator. This SDN-controlled network enables flexible and software-defined reconfiguration of all network functions, while also forecasting traffic demand in space and time. For more effective network control and management, researchers proposed a mechanism for reducing signalling. “The 5G-XHaul SDN architecture allows automatic provision of multi-domain connectivity services in 5G transport networks in a matter of seconds,” notes 5G-XHaul’s technical coordinator Dr Daniel Camps. A city-wide field trial carried out in Bristol, integrating the novel 5G-XHaul optical and wireless technologies and controlled by the SDN control plane, showcased the overall project architecture. The functionality and end-to-end performance of this field demonstration verified the suitability of 5G-XHaul’s solution for 5G. Project results are particularly relevant for future networks that need to be dynamic and manage themselves automatically to welcome billions of connected devices. “Our new network solution can flexibly connect small cells to the core network. Exploiting user mobility, it allows the dynamic allocation of network resources to predicted and actual hotspots. This dynamic allocation serves the needs of the users,” concludes Prof. Grass.


5G-XHaul, 5G, wireless, backhaul, optical network, fronthaul, wavelength-division multiplexing (WDM), passive optical network (PON), software-defined networking (SDN), millimetre-wave, network function virtualisation

Project information

Grant agreement ID: 671551


Closed project

  • Start date

    1 July 2015

  • End date

    30 June 2018

Funded under:


  • Overall budget:

    € 7 233 887,50

  • EU contribution

    € 7 233 887,50

Coordinated by: