A study of multimedia CDMA system for personal satellite communication

Abstract

A variable data rate CDMA system with constant envelope modulation is studied by hardware simulation for personal multimedia random access satellite communications in the Ka-band and millimeter-wave region. This system utilizes a constant occupied bandwidth and has variable data rates and processing gains to mitigate communication link impairments such as fading, rain attenuation and interference as well as to handle a variable data rate on demand. A proof of concept hardware system for a 6 MHz bandwidth transponder is developed for hardware simulation, which uses MSK-, GMSK-, and OQPSK-type constant envelope direct sequence spread spectrum modulation and handles data rates of 4 to 64 kbps. The receiver is designed with a coherent matched filter technique to achieve fast code acquisition, AFC and coherent detection in a single matched filter circuit. This receiver structure facilitates a variable data rate on demand during a call without the aid of system control earth stations. The proposed system is described, along with the CDMA performance of the prototype equipment with the non-geostationary ETS-VI satellite at the Ka-band (30/20 GHz). Both the IF loop back hardware simulation and satellite link test performances of the prototype equipment prove it has the potential for personal multimedia satellite applications.