Effect of physical traffic & t-junction layout on radio signal characteristics & network performance at 5.9 ghz

IEEE 802.11p, which operates at 5.9 GHz, has been the widely adopted communications standard for vehicular communications and this has prompted studies at different physical locations on the network performance, pathloss, Doppler and delay spreads in the 5.9 GHz radio channel. This thesis presents novel measurements of network performance, signal strength and Doppler spread under NLOS conditions at three T-junctions with different street widths and building layouts. The study found that there was less received power and poorer network performance in intersections with single/dual lanes and fewer buildings on either side of the roads – the maximum range for reliable operation (>90%) of the network is reduced to approximately 10 m from the intersection centre. Higher signal strength in the presence of buildings is consistent with multipath propagation contributing positively towards the signal strength as shown by a site specific ray tracing model developed as part of this project. Signal strength measurements were compared with predictions from the model virtualsource11p and a median error less than 5 dB was found for measurements in urban environments and closer to the intersection centre. The median error was greater than 10 dB and increased with the distance from the intersection centre in junctions with wider roads and fewer buildings either side of the road. The relationship between a vehicle’s size and the Doppler spread it causes is another unique observation of this study and has been investigated by developing a simple model. Doppler spreads become larger as the reflecting vehicle moves closer to the transmitter and receiver and when the size of this vehicle is larger. A directional antenna was used to determine the azimuth of arrival of the strongest multipath components with the observations demonstrating the importance of including transient features in maps when ray tracing.