WLAN/WDS Performance using Directive Antennas in Highly Mobile Scenarios: Experimental Results

This paper presents experimental results from a series of IEEE 802.11g studies to investigate the performance of vehicular to roadside wireless communications. In particular, two high-gain omni-directional antennas were used at the roadside access point, while high-gain omni-directional and directional antennas were compared for use on the vehicle. By employing high-gain antennas at both ends of the wireless link, the range of the WLAN network was dramatically improved. Moreover, the use of directional antennas in highly mobile applications allows communication at higher vehicle speeds (by reducing the Doppler spread) and longer ranges (by reducing delay spread and increasing the received power level). Results show that mobile performance is significantly improved, especially when directional antennas are utilised at the receiving end of the link. As a result, the amount of data that can be exchanged between a moving vehicle and a roadside access point is considerably increased. The use of WDS (wireless distribution system) is also investigated in this paper. The reported measurements form part of a larger campaign to compare WiFi, WiMAX and HSPA technologies for vehicular communications.