DLINK - D-band Wireless Link with Fibre Data Rate

The extraordinary increase of wireless data traffic by smartphones and laptops, virtual reality, billions of IoTs or Industry 4.0 infrastructure need 5G, small cell densification and reduction of digital divide. High throughput connectivity everywhere is a fundamental requirement to support the growing data demand and the evolution of future wireless communication market. Affordable wireless networks with fibre data rate are needed.
Wireless links with multi-gigabit (Gb/s) distribution at millimetre waves have been demonstrated up to 400 GHz. However, the strong atmosphere attenuation at the increase of frequency and limitations of the present semiconductor-based millimetre wave technology limit their potentiality. E-band wireless links with 2 GHz bandwidth and theoretical few Gb/s are already in the market, but large antenna footprint and low transmission power are probably preventing wider adoption.
The portion of the spectrum above 100 GHz includes numerous wide bands which are presently unused, and could support tens of Gb/s, if adequate millimetre wave technology were available. In particular, the D-band (141 - 174.8) has about 28 GHz split in three sub-bands.

The DLINK project aims to bring the UK at the forefront of millimetre wave wireless technology through the realisation of the first high capacity link at D-band with unprecedented performance, to provide 45Gb/s, over 1 km range, and with 99.99% availability in ITU rain zone K (typical of UK and Europe). The DLINK system includes a high power vacuum traveling wave tube (TWT) of new generation driven by a novel resonant tunnelling diode (RTD) transmitter with an integrated vector modulator. The system will be demonstrated in Frequency Division Duplex (FDD), with two bands of 10 GHz each to provide about 45 Gb/s data rate. The high performance of DLINK is enabled by traveling wave tubes as amplifiers, with about 10W output power, which is more than one order of magnitude than solid state amplifiers at the same frequency. The TWT working mechanism is based on the transfer of energy from a high energy electron beam, flowing in a waveguide with high level of vacuum, to the electric field generated by the input signal. No D-band TWTs are available in the market. Substantial challenges must be solved for an affordable microfabrication of mm-wave waveguides, due to small dimensions and three dimensional shapes. The transmitter will be an RTD oscillator with very low phase noise to support QAM modulation generated by an on-chip PIN diode vector modulator. The DLINK system includes two transmitters, one for each FDD channel, integrating a RTD oscillator/transmitter, a TWT and an antenna. For the first time, the property of a transmission link with 20 GHz bandwidth above 100 GHz will be investigated by field tests at BT.
The DLINK project has a strong industry focus. It is a collaboration between Lancaster and Glasgow Universities with the strategic support of the wireless communication industry full chain, from devices to end users: IQE (semiconductor wafers), Filtronic (mm-wave links), Teledyne e2v (mm-wave TWT), Nokia (system manufacturer), Intel (chip manufacturer), BT (UK main network operator and end user).
The high impact of the project will enable new architectures of wireless high capacity networks by mesh of high data rate links at mm-waves. The DLINK project has the ambition to fully contribute to "Connected Nation", one of the four Prosperous Outcomes and to benefit other numerous ambitions of the Prosperous Nation outcomes. DLINK involves researchers and PhD students of two leading research groups and a number of industry partners that will work together for the success of the project, with a long term strategy for future industry exploitation. A particular attention is devoted to growth of talent, improving the gender balance in the millimetre wave technology sector highlighting role models in the Lancaster and Glasgow teams.

Internet access is recognised as commodity at the level of water or electricity.
The wide use of smartphones, laptops, the urgency of full UK broadband coverage, new data hungry applications such as IoT or car-to-car are posing relevant technology challenges. Fibre is widely deployed, but too expensive for a full coverage. Wireless networks are gaining interest among operators, however, a suitable solution for the high capacity needed has not yet been found. The use of the millimetre wave spectrum to replace fibre connections is the only viable route, but advancements in mm-wave technology are needed. This DLINK project offer of 45 Gb/s wireless long distance D-band link opens the route to deployment of unprecedented capacity wireless networks, with substantial and broad impact in the UK as outlined in the following.

Impact on economy
The development of state of the art technology at mm-waves, production of novel mm-wave devices, fabrication and testing of new wireless high capacity transmission systems will boost the UK industry capability in the fierce race for new wireless networks. The high number of key industrial partners in the project demonstrates the high impact expected at industry level. World Economic Forum estimates the global economic impact of 5G in new goods and services at $12 trillion by 2035.
The UK mm-wave industry has the opportunity to gain leadership and create new high qualified jobs in a variety of sectors such as micromechanics, materials, mm-wave and solid state technology, network architectures and protocols. In particular, Filtronic, SME in mm-wave wireless links, will open new markets as supplier of major players, such as Nokia or Huawei. Teledyne-e2v could expand TWT production for the wide 5G market. BT, the main UK operator, will benefit of the full UK supply chain to build affordable tailored wireless networks and offer high end services. High data rate connectivity is the enabler of the Industry 4.0 vision. The report commissioned by the UK government to Jeurgen Maier, Made Smarter, clearly states that digital manufacturing is a UK strategic priority that needs high data rate infrastructure. Finally, 5G is strategic for BT and all the UK mobile operators. One or two new university spin-off companies are expected as follow up of the project.

Impact on people
DLINK is a great career opportunity for the group of early career researchers and PhD students that directly and indirectly will be involved in the project. The close interaction with industry and the networking plan will permit to grow a new generation of leaders in mm-wave technology for a robust and long term progress in RF Engineering. In terms of improving the gender balance in the RF engineering sector, the hope is that role models already present in the research teams will help attract a diversity of brilliant minds to overcome the actual skills shortage in the sector.

Impact on society
The availability of ubiquitous Internet coverage with high speed is the pillar of the modern society. Society and people are more and more interconnected with services, e-healthcare, e-commerce, social networks, e-entertainment. It has been also estimated that any increase of data rate per users has a direct effect on the increase the GDP. A step change in connectivity to support the unstoppable increasing data traffic must be provided with new wireless infrastructures. The DLINK mm-wave high capacity link technology will to respond to this quest.

Impact on knowledge
The DLINK project aims to shift to the UK the leadership in mm-wave wireless technology, so far mostly held overseas. It will benefit of the experience developed by the team by three major European Commission Horizon 2020 projects. The following outcomes are expected: production of a high number of scientific outputs, advanced fabrication processes, new technical skills, new learning routes for undergraduate and postgraduate students, and technology transfer.