Digital Distributed Antenna System (DDAS)

Lead Research Organisation: University of Cambridge
Department Name: Engineering


This project will seek to commercialise research which has led to the development of a new paradigm in the distribution of wireless services. In short the targeted products will, for the first time, enable the distribution of multiple RF services over conventional internet infrastructure for the first time. It will allow full remote management and monitoring of such services, and enable a substantial increase in backhaul capacity. The concept behind this current proposal won the Cambridge University £5k Entrepreneur's Challenge in its field in 2011.

To date in-building DAS systems have primarily been analogue and this results in limitations in the number of wireless channels, and hence the capacity, that can be transmitted over an individual optical fibre. If digital systems have been used, they have typically been configured for known, pre-determined, RF modulation formats and protocols, and require very high bandwidth digital links to transmit the signals. Up to now, this has been acceptable because conventional DAS systems have been used to ensure good coverage for mobile services with capacity requirements being relatively modest. However both analogue radio over fibre and conventional digital DAS have considerable limitations for likely future user needs where for the first time, capacity will become a very important issue, as it will affect the growth of high bandwidth services such as mobile video. This is because both conventional techniques essentially use large bandwidths which necessitate the use of individual back-haul fibres being required to address individual antennas.

As such these systems become limited in their ability to scale to the numbers of antennas required to deliver on future bandwidth demands, and require the conversion from IP internet traffic to mobile communication standards to occur at a base station within the building from which the signals are carried on the DAS. For future systems therefore, where capacity will become as (and ndeed more) important than coverage, a new technology is required. Recently we have devised a system concept able to solve this problem (even though it is able to use low bandwidth links such as twisted-pair cables), and in turn proposed how it would enable a new form of commercial model for the delivery of high bandwidth services in the future. The technology not only makes possible exploitation by hardware sales, but also offers the creation of new service models which a new companies could adopt, in effect creating the mobile service equivalent to 'cloud computing'.

Thus this digital DAS (DDAS) project aims to develop a novel DAS which could take advantage of existing Ethernet infrastructure in such places to make them economically feasible to install. In addition, it offers a more flexible way of increasing capacity since the radio source is centralised. It intends to take the current laboratory demonstration of the low bit rate digital DAS system to commercialisation. The technical aspect of the work will focus on a prototype system to demonstrate to potential customers, investors or collaborators. The commercial development plan will develop relationships with customers and potential licensees while building a business plan with the aim of generating a spinout company at the end of the grant period.

Planned Impact

We have considered the impact of our research within each of the four main areas identified by EPSRC, namely economy, knowledge, people and society.

Economy: As a project aimed at the commercialisation of research, this project will the judged at every stage on its economic impact, as its success depends upon it. We intend to engage particularly closely with a number of companies including Zinwave, who are keen to advanced their technologies to address the major challenge of high capacity wireless delivery in the coming years. They have skills that are fully complementary to those of the group and will allow much more efficient and cost-effective commercialisation. Their direct access to key customers is a major advantage to us.

Given that there has been a lot of interest in the technology, we anticipate that, should the technical and commercial development activities in DDAS go to plan, that there will be the opportunity for the creation of a commercialisation vehicle perhaps within some joint venture. This work will be supported in this goal by Cambridge Enterprise.

We are particularly excited that whilst the work began has a systems project (involving primarily hardware research with software support), it could well lead to a new service-industry concept where individuals can be provided flexibly with a new wireless service on an on-demand basis, without requiring expert installation, in a much more economic and energy-efficient manner than previously regarded possible. The economic benefits to the service industry are ones that we wish to explore fully in the proposed project.

Knowledge: Although much of our research has direct exploitative benefit, we believe that the knowledge that we generate also benefits those researching within the academic community both within our disciplines and elsewhere, and also non-academics. Also, we hope to educate and reach out to the public with the new technology through public seminars, presentations, demonstrations and exhibitions. We believe this is necessary as it is anticipated that this new technology will be part of everyone's life in the near future.

People: The Photonic Systems group has an excellent record of training students and staff, with its alumni going on to permanent positions in academia, industry, government and commerce. The student (Tongyun Li) and RA (M Crisp) who will be involved with this project will gain invaluable experience in taking a technology concept from university research into a commercial venture. The inclusion of activities such as projects by students from Engineering (including the CDT in Photonic Systems Development) and the Judge Business School will allow a wider pool of students, across the engineering, economics and business departments, to benefit from the project providing experience in finding potential applications and routes to market for a real technology under active commercialisation.

Society: The ability to provide high bandwidth services will continue the immense benefit that mobile technology has had for the wider society in people's day to day lives. Increasingly real-time monitoring will be crucial in healthcare and in a host of environmental applications such as pollution, security, transport and energy monitoring, and some would argue that the solution to climate change will rely heavily on advances in this technology. It is of great importance that high bandwidth solutions to the distribution of wireless services are found so that individuals can have the enhanced lifestyles to which they aspire.
Description Designed a Novel Data Compression Algorithm. This signal processing technique has shown the capability of compressing digitised RF wireless signal to a much lower level and decompressing at the other end of the link. It includes a sampling compression consisted of training and a running sequence for learning the best sample position of a digitised RF signal and select only right samples to transmit, and a resolution compression based on controlling and maintaining the signal dynamic range to reduce the quantisation requirement. These methods significantly reduce the signal bandwidth to be transmitted. The algorithm is also feasible for multiple wireless standards, allowing high compression ratio while maintaining its signal quality and integrity after full signal recovery. It has also been designed to be able to implement on real time processing platforms which is easy to implant into industry systems.

Built a Real-time Platform of Digital RF Distribution System based on FPGAs. Through experiments, it has shown the feasibility of distributing and processing digitised RF signal in real time on commercially available FPGAs for indoor scenario. The FPGA signal processing components on the platform includes ADC/DAC interface processing, digital downconversion and upconversion, data compression and decompression, and high-speed transceiver interface processing. Dynamic range over 50dB for 3GPP WCDMA in-building distribution has been demonstrated using the platform. This system also allows multiple services to be supported on a single existing infrastructure, such as Ethernet. Therefore, cost effectiveness and energy efficiency can be increased through digital signal processing techniques and ease of installation difficulty.

Demonstrated a solution for transmitting digitised RF signals over multiple cabling schemes. By using the data compression techniques, the required bit rate can be reduced to a level suitable for transmission on twisted pair which could be used to extend the coverage of wireless services. Our demonstration has shown that, with data compression, a dynamic range of 20dB for a 3GPP WCDMA signal carried on a 30m CAT5e link is achieved. The performance is improved by using CAT6 cable with larger bandwidth. Both 0.5m and 10m CAT6 and coaxial cable give a dynamic range of 55dB. Without data compression, the data rate would necessitate the use of optical fibre at practical transmission distances. A dynamic range of 70dB is shown for the non-compression scheme using high bandwidth short coaxial cable.
Exploitation Route Building Owner/Developers, Companies, Airports, Supermarkets, Stadiums, Mobile Operators. Through new industrial/academic joint project and Spinout company
Sectors Digital/Communication/Information Technologies (including Software),Leisure Activities, including Sports, Recreation and Tourism,Manufacturing, including Industrial Biotechology,Retail,Transport

Description The findings have been used to form a spinout company for providing highly efficient in-building wireless solutions in large buildings such as airports, shopping mall, stadium and residential areas. And also the finding has led to a new University and Industrial joint research project for exploring a new type indoor wireless distribution system for integration of multiple wireless carrier onto existing indoor networks.
First Year Of Impact 2013
Sector Digital/Communication/Information Technologies (including Software),Leisure Activities, including Sports, Recreation and Tourism,Retail,Transport
Impact Types Societal,Economic

Description Converged Optical and Wireless Access Networks (COALESCE)
Amount £1,373,034 (GBP)
Funding ID EP/P003990/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 01/2017 
End 12/2021
Description SWIFT - CAPE Partners
Amount £132,508 (GBP)
Organisation Beijing Institue of Aerospace Control Devices 
Sector Private
Country China
Start 03/2014 
End 12/2016
Description BIACD 
Organisation Beijing Institue of Aerospace Control Devices
Country China 
Sector Private 
PI Contribution The BIACD is a collorator for the smart inbuilding wireless system using flexible transmission technology (SWIFT) project
Collaborator Contribution The BIACD is a collorator for the smart inbuilding wireless system using flexible transmission technology (SWIFT) project
Impact This collaboration is ongoing. The results the SWIFT project will be announced next year.
Start Year 2014
Title Transmission of an rf signal over a wired communications link 
Description We describe a method of sending RF signals over a wired communications link, the method comprising: inputting an RF signal bearing data symbols at a symbol rate; digitising a version of said RF signal to provide digitised samples of said data symbols, a said sample comprising data defining a digitised I and Q value for said version of said RF signal; and sending said digitised I and Q values for said samples over a wired communications link. The digitising comprises: oversampling said version of said RF signal to provide an oversampled digital symbol data stream, and decimating said oversampled digitised symbol data stream to provide a decimated stream of said samples for sending over said wired communications link, where said decimated stream of said samples has an integral number of samples for each said data symbol. The method further comprises selecting a timing of said decimated stream of samples with respect to said version of said RF signal which substantially minimises a variance of the stream of samples 
IP Reference WO2013156770 
Protection Patent granted
Year Protection Granted 2013
Licensed Yes
Impact A spin out is formed based on the research findings and the patent. Furtuer research project is being conducted with the patent as a prior art
Company Name eComm Ltd. 
Description A university spin-out, eComm Ltd., has been created to exploit the technology. The eComm technology is based on a novel DDAS that enables in-building RF distribution over existing infrastructures, such as Ethernet in a cost-effective manner. 
Year Established 2012 
Impact The company is a portal for the DDAS tehcnology to be commercialised. Its exploitation on commercialisation has attracts various international collaborators and potential customers, particular in Chinese market which has 20 to 30 Billion GBP inbuilding wireless market in next 5 years. Through commercial project and collaboration, eComm Ltd has created strong product development and marketing teams aiming to deliver successful products to the inbuilding wireless market.