This paper considers the downlink performance of mobile communication channel based on a novel wireless infrastructure that is called stratospheric platforms (SPF). The SPF has been recently proposed as an alternative method for delivering mobile communication services such as IMT-2000 in parallel with cellular tower-based terrestrial system or satellite. Channel performance evaluation is now becoming a matter of urgency in the designing of communication link between the platform and mobile user. We first evaluate propagation characteristic in urban area in order to obtain propagation parameters in terms of path loss model and Rice factor. Due to their unique positioning, elevation and azimuth angle are considered as main parameter in SPF environment compared with terrestrial tower-based system. The propagation parameters are then used in order to evaluate downlink performance for IMT-2000 services served by the SPF. Different applications refer to different information bit rate that is carried by IMT-2000 system are considered in the analysis. In all scenarios, downlink performance decreases as the service bit rate increases and it becomes worse when elevation angle lower than 40°.