Research on Up and Down Channels of Satellite Communication Based on Spread Spectrum Principle

Abstract

Satellite communication mode is based on spread spectrum technology, and CDMA mode is adopted as a whole. In satellite communication system, all base stations, base station controllers, mobile switching centers, etc. adopt a common CDMA reference time, namely CDMA system time. The uplink channel is differentiated by PN sequence with orthogonal Walsh code, and is transmitted by the same radio-frequency carrier. The downlink code division physical channel is composed of PN long codes with a length of 242-1, and different phase offsets of the long codes are used to distinguish users. Long codes PNA and PNT are code division channels provided by access channel and downlink traffic channel respectively. The uplink and downlink work in X-band, which meets the speed requirements of 8Kb/s for uplink and 32Kb/s for downlink, and realizes the functions of resisting human interference, narrowband interference, multipath interference, rain attenuation and ranging.