Influence of microstrip patch antenna heights on wideband channel parameters in a static indoor channel

The paper presents the wideband parameters of an indoor channel such as the path loss characteristics and root mean square r.m.s. delay spread in a typical laboratory setting. Different antenna height configurations were used in the experiment. Measurements were made by using a vector network analyser at 1·95 GHz using directive patch antennae. The path loss characteristic changes with the different types of antenna height configuration. For line-of-sight LOS n the value ranges from 2 to 2·9, whereas for an obstructed path OBS it ranges from 3·3 to 3·6. Similarly, the median r.m.s. delay spread ranges from 6·2 ns to 10·4 ns in LOS. However, the r.m.s. spread delays obtained are constant and are based on the type of antenna height configuration for OBS. For the same antenna height configuration, it centres on 25 ns, whereas the optimized configuration is at 19 ns. The correlation of r.m.s. delay spread with transmit–receive T–R distance is high in LOS, but not when different antenna height configurations are considered. However, in OBS it is explicitly clear that r.m.s. delay spread is independent of distance. Generally, the r.m.s. delay spread increases when the path loss characteristics are more severe. The results presented here advocate the choice of directional antennae for a typical indoor wireless LAN environment, as compared with that of an omni-directional antenna. Moreover, careful selection of antenna height at the base station to avoid the Fresnel zone is essential for optimal n performance. This selection yeilds an n exponent value following very closely free space propagation, and it has the lowest r.m.s. delay spread with median value of 6–2 ns.