Citation
Abstract
International Mobile Telecommunications (IMT)-2000 and its European member, Universal Mobile Telecommunications System (UMTS), are planning to deploy mobile radio services in the S-band (around 2 GHz) in the next few years. NASA’s Deep Space Network (DSN) has been operating powerful S-band transmitters at three worldwide sites. The DSN’s uplink frequency (2110-2120 MHz) is part of the spectrum to be used by the UMTS terrestrial system for the forward links (2110- 2170 MHz). It is necessary to determine if the DSN transmitters would interfere with nearby IMT-2000/UMTS receivers through transhorizontal propagation. Under normal conditions, interference causes three types of losses that will reduce the power level as received by a victim receiver: free-space loss, difiraction loss over the spherical Earth, and difiraction loss over mountain peaks. In this article, simplified topographic mountain-peak profiles along the radial direction are used to calculate the losses for all three DSN sites. In addition, there are unusual propagation modes under which the interference can have favorable propagation channels to reach areas beyond the line of sight. They are, respectively, the ducting mode (one-dimensional loss) and rain scattering (rain as a reflector). These two modes are strongly timepercent dependent. The propagation loss for these special modes also is calculated. All losses are combined to estimate the minimum "coordination distance" beyond which the interference will be attenuated below the threshold level of the IMT2000/UMTS receiver. We find that for 85 percent of the time this distance is about 70 km from the DSN site. The radial distance can be reduced to as small as 30 km in the direction of a large mountain shadow. For 15 percent of the time, ducting and rain scattering can greatly increase the distance to several hundreds of kilometers.
Keywords
Details
- Volume
- 42-142
- Published
- August 15, 2000
- Pages
- 1–21
- File Size
- 623.8 KB