Broadband multimedia services
Broadband multimedia services supported by 40GHz fixed and mobile access networks are often hindered in their performance by both manmade and natural obstacles such as signal interference and bad weather conditions. Project OBANET, Optically Beamformed Antennas for adaptive broadband fixed and mobile wireless access NETworks, was undertaken with the objective to improve the performance of access networks and to evaluate specific coverage area management. A new modulation technique has been developed which remotely feeds a base station, BS, with information signals in their original base-bandIn this way the same information can be transmitted through a wireline and a wireless access network. It allows long fibre spans due to its dispersion-tolerant nature and simplifies hardware requirements due to its frequency doubling capacities. Different band frequencies can be operated simultaneously (wireless and wired) when the need arises for example during service work or whenever a backup is needed. An algorithm has also been developed to estimate the direction of arrival of signals coming from user terminals and the position of a mobile user. Traditional tracking algorithms use digital signal processing techniques. However these are not suitable for Broadband Wireless Access (BWA)networks due to the high frequency of operation. This algorithm is based on power measurement of pilot tones similar to the mono-pulse technique used in radar systems. A system for assessing the performance of the wireless network has also been developed. It measures the carrier to interference ratio in a Time Division Duplex, TDD/Time Division Multiple Access, TDMA wireless network with beam switching antennas. This can be used for the optimisation of performance and cost of systems.
