GWoFAN

 

Gbit/s Wireless-over-Fibre Access Networks

(GWoFAN)

Frederic LUCARZ and Alwyn SEEDS 

Start date        01.10.2004

Duration           36 months
Status              ongoing

Sponsored by

 

Downloads:  CII Brochure [.pdf]  -  CII Poster [.pdf]

 

Department of Engineering Centre for Photonics Systems (UK)

 

Future broadband mobile communication and distribution systems envisage the use of millimetre- wave frequency as the transmission medium, due to wide available bandwidth. The frequencies in the 40 GHz region have already been allocated for Multipoint Video Distribution Services (MVDS) and 60 GHz band for Mobile Broadband Systems (MBS).

Wireless-over-Fibre technology provides a cost-effective solution for delivering high data rate, as well as for extending the range of the existing wireless access networks. This technology has been successfully deployed to provide a low cost solution for extending the coverage of the cellular radio system in public places such as shopping malls.

Gigabit/s wireless access solutions are now being actively researched both in academia and industry to overcome the last-mile bottleneck in access networks and thereby meet the growing demand for future broadband services.

At millimetre-wave frequencies (>30 GHz), propagation consideration requires the base stations for such systems to be closely spaced and favour frequency re-use through a micro or pico-cellular architecture. The greatly increased number of base stations required to serve a given geographical area requires the base stations to be simple, with a low cost interface to the fixed network.

If the signals to be transmitted are sent from a central station to the base stations over optical fibre as intermediate frequency (IF) modulated signals, then the base station functionality can be reduced to photo-detection, frequency conversion and amplification. The required mm-wave local oscillator (LO) signal is generated at a central station and distributed on a separate wavelength, giving exact frequency synchronisation amongst all base stations.

We propose to distribute signals at IF using electrical up/down conversion at the base stations. In addition to overcoming the chromatic dispersion limitations, this approach enables directly modulated lasers and modest bandwidth photo-detectors to be used, with the potential for substantial cost savings. LO distribution dispersion penalties can be made negligible by using a heterodyne generation technique.

 

The main objectives of this project include a feasibility study on future wireless-over-fibre systems that operate in the millimetre-wave range. To enable distribution of the broadband signals to a number of base stations, we have considered the star-tree architectures based on coarse wavelength division multiplexing (CWDM).

We aim to design an optimized optical distribution network for mm-wave over fibre systems that is capable of delivering 1 Gb/s wireless data to fixed or mobile customer units.

 

The work provides an approach to Gbit/s access in deployments where mobility is a requirement or the cost of fibre to the home (FTTH) is not justified.

The use of uncooled directly modulated lasers with CWDM and optical distribution of the millimetre-wave local oscillator signal allows substantial reduction in the overall system complexity and cost, as will be necessary for the widespread adoption of millimetre-wave wireless access systems.

Wireless-over-Fibre is a suitable technology and provides a cost-effective solution for delivering high data rate, as well as for extending the range of the existing wireless access networks. The technology has already been successfully deployed to provide a low cost solution for the cellular radio system in public places such as shopping malls.

 

Previously we have demonstrated full-duplex QPSK wireless data transmission over 12.8 km single-mode fibre between a central station and a remote base station incorporating a 2.2 km fibre ring architecture using a bi-directional Semi-conductor Optical Amplifier (SOA) with remote 40 GHz local oscillator delivery [1].

For indoor applications, the star topology is preferred, whereas a star-tree or star-bus topology is preferable for extended coverage for outdoor applications as compared with a ring topology.

A wireless-over-fibre system capable of delivering 1 Gbits/s to mobile stations is being set up in our lab. The system will implement Differential Phase Shift Keying (DPSK) modulation scheme, and will include a wireless link operating around 40 GHz.

 

[1] T. Ismail, C. P. Liu, J. E. Mitchell, A. J. Seeds, X. Qian, A. Wonfor, R. V. Penty and I. H. White, “Full-duplex wireless-over-fibre transmission incorporating a CWDM ring architecture with remote millimetre-wave LO delivery using a bi-directional SOA,” Optical Fibre Communications 2005 (OFC 2005), Anaheim Convention Centre, Anaheim, California, USA.

[2] http://www.ee.ucl.ac.uk/research/UFP_WOF.pdf

[3] Analogue Optical Fibre Communications, B. Wilson, Z. Ghasemblooy, I. Darwazeh, 1995

[4] Broadband Wireless Access, Benny Bing, Kluwer Academic Publishers, 2000

[5] Radio over Fiber Technologies for Mobile Communications Networks, Hamed Al-Raweshidy, Shozo Komaki, 2002