Research On The Satellite Communication System Based On CDMA-CWTDM Conversion

This thesis researches on a new satellite communication system based on onboard CDMA-CWTDM conversion. Compared with CDMA-TDM conversion based on a hub station, the new system without an expensive and huge hub station can also make the user terminals more compact and cheaper, moreover, it makes the channel efficiency increase for twice and makes the transmission delay between every two user terminals decrease to half, whose performance is very attractive.The thesis mainly engage in the design of USAT mobile satellite communication system based on onboard CDMA-CWTDM conversion with some key technology including de-spread onboard, low complexity multi-user detection algorithms, CWTDM multiplex/time-hopping, CWTDM demultiplex/dehopping, samples interleave, high-precise sample synchronization and the technology of anti-multipath fading. The author's main contributions are as follows:1. This thesis designed a CDMA-CWTDM satellite system, and analyzed detailedly the theory and some key technique of the transmitter, block of processing onboard and receiver.2. In this thesis, the author analyzed and demonstrated in details the system gain and the necessity of de-spreading on the satellite, furthermore has completed some simulations.3. The key techniques of de-spread are researched and with specific emphasis on the anti-jamming ability of optimal receiver of direct-sequence system and some optional synchronization techniques including FFT fast acquisition algorithms, partial integral de-spread algorithms without fine synchronization, a high-precise symbol synchronization technique based on multi-phase filter bank.4. An adaptive multi-user detection algorithms applied to satellite communication system is proposed after comparison of some classical multi-user detection techniques.