Wireless local area radio networks wideband characterisation and measurements at 62.4GHz
The presence of multipath propagation in indoor environments limits the performance of wideband radio communication systems and also the maximum data rate that can be feasible. This thesis addresses the dynamics of propagation mechanisms needed to design and exploit future broadband wireless local area networks in the 60GHz millimetre-wave band. The frequency band between 62-63GHz with data rates up to 155Mb/s, has been provisionally assigned for Mobile Broadband Systems. The main emphasis of this study was to provide an original contribution to the development, design and planning of future broadband communication systems using new high-resolution wideband channel measurement data. Based on this data, spatial and temporal statistics of several line-of-sight radio paths in a University campus are presented and analysed. In order to enable measurement of the wideband propagation characteristics a high-resolution (Ins) wideband Frequency-swept channel sounder was designed and implemented at 62.4GHz. The channel sounder has been built around a Vector Network Analyser to measure the complex transfer function of the channel. The instantaneous coherence bandwidth is found to be highly variable with the location of the receiver with respect to the base station. With delay spread values ranging from 20 to 70ns the coherence bandwidth remains most of the times below 10MHz. Based on the maximum delay spread of 68ns obtained in a 41m long narrow corridor, a BER of 10" 3 and normalised delay spread of 0.1, the minimum data transmission rate is estimated at 1.47 Mb/s. For a 12.80m room environment with maximum delay spread of 20ns the minimum data transmission rate is 5Mb/s. To achieve higher data transmission rates channel protection countermeasures appears to be necessary. However limiting the extent of a picocell size and utilising the potential capability of frequency re-use at 62.4GHz can result in radio network implementation without the complexity of countermeasures. Results relating to coherence bandwidth variability in multipath conditions confirm that higher user mobility envisaged for MBS would present a real challenge to the achievement of data transmission rates of the order of 155Mb/s. The research work reported in the thesis has been able to identify and extract from extensive high resolution wideband propagation the necessary design characteristics for the development of realistic radio planning models. Using measured results obtained in a number of radio paths geometries, the objectives of the project have been largely achieved and further work is recommended.
wideband radio communication systems, dynamics of propagation mechanisms, Broadband Wireless LANs
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