2 GHz propagation and diversity evaluation for in-building communications up to 4 MHz using high altitude platforms (HAP)

This paper investigates in-building radio coverage at 2 GHz from a high altitude platform (HAP). The HAP is located at a height of 20 km above the Earth. The propagation analysis is based on a novel two-dimensional ray-model. The model makes use of an array of virtual transmitters placed around the building. To improve radio reception, two branch switched and equal gain diversity combining are applied at the terminal. Propagation coverage grids are generated over a pair of multi-floor building structures. Results include the calculation of in-building penetration loss and the derivation of link margins for 90% and 99% indoor area coverage. Using this data, the required HAP transmit power is calculated as a function of diversity technique, area coverage and operating bandwidth. Assuming a 1 km radius spot beam, a 3G compatible operating bandwidth of 4 MHz and 90% in-building area coverage, the results indicate that space diversity at the terminal reduces the HAP transmit power from 2.15 Watts to 0.84 Watts.