MODAL: An enabling technology for wireless access

Future mobile radio systems must use ever higher radio frequencies as spectral congestion effectively removes lower frequencies from availability. Future broadband mobile services (e.g. MBS) will use mm-wave frequencies and utilise a microcellular architecture. The limitations of fibre/radio for these applications are outlined and a novel solution, based on optical heterodyning, is proposed. A RACE funded research programme is investigating this approach and the authors describe the demonstrator that will be built. Applications for MODAL (microwave optical duplex antenna link) type systems are discussed and some of the most significant results achieved to date are summarised. The authors outline a novel solution to the problem of providing a connection between a base station and a remote antenna for a mobile access system operating at mm-wave frequencies. Optical technology has been adopted to remove the need for mm-wave signal sources whilst optical fibre is used to interconnect the base station and the antenna thereby ensuring both low installation and maintenance costs.