| Advance radio system designs have been proposed that are intended to overcome or even take advantage of the impairments of the radio channel caused by multipath effects in urban environments to achieve even higher performance. The design of such systems and their evaluation requires knowledge of higher order channel statistics. For example, the design of smart antenna systems requires knowledge of the delay spread and angle spread in the environment where the system is to function. The delay and angle spreads have been measured at individual locations in a few cities. However, it is not clear if the measured results are widely applicable to other building environments. To overcome this limitation, we have used a 3D ray tracing code, called the VPL method, to simulate channel statistics. Our goal is to relate the variation of statistical properties of the radio channel to the statistics of the building environment, and to the geometry of the radio link. Simulations have been run to find the influence of the statistical parameters describing the building distribution on delay and angular spreads. Results for elevated base station antennas show that both delay and angular spread increase as the base station antenna is lowered below roof level. Simulations for three cities having different distributions of building height show that the environment and base station antenna height have a significant effect on the distribution of angle spread, but have less effect on the delay spread. However, only the delay spread shows a consistent increase with the distance to the mobiles. We also have discussed the characteristic changes in the radio channel resulting from displacement of mobiles along a street. These changes in the channel include finger life distance, autocorrelation and crosscorrelation of shadow loss. The effect of prediction error was also studied and found to have little effect on the statistical properties of the channel. And we carried out the CW and wideband channel measurements for Fixed Wireless Loop application at the carrier frequency of 2.475GHz in suburban area. |
