SYSTEM ASPECTS OF SCANNING BEAMS FOR WIDELY DISTRIBUTED USERS

Abstract

Satellite communications in the allocated EHF bands, (i.e., several frequency segments from ~20 GHz to 50 GHz) has the potential for providing interference resistant communications to users employing small, mobile terminals. To realize this potential, advanced spacecraft technologies are required, such as uplink coverage through high gain directive beams, onboard signal processing, and downlink beam hopping. Simultaneous worldwide uplink coverage could be obtained via many narrow uplink antenna beams which collectively cover the earth field-of-view. When worldwide communications traffic is low volume, a reduction in space segment impact can be achieved by using a few narrow uplink antenna beams to provide the required service. To minimize delays, these beams must be able to rapidly point anywhere within the field-ofview to cover individual users who require a channel for brief communications. The agile antenna beams can be shared through demand assignment techniques. A multimode common transmission format can provide both data and control channels. The data channels are available at several rates to allow either full duty cycle data transmission or burst data transmission. With burst transmissions, a single beam can support multiple calls in a time division multiplexed fashion. The control channels are utilized in coordinating the use of satellite resources to efficiently meet the communications needs of the users. This paper discusses the use of EHF satellite communicatons to provide service to widely scattered users. The use of control channels to request and coordinate service is described. Example control protocols are presented, and system performance is indicated.