CDMA communication system for mars areostationary relay satellite

Stationary orbits around Mars, which are known as areostationary orbits, have similar characteristics as Earths geostationary orbits. An areostationary Relay Satellite is expected to be used for future communication network for the exploration of Mars. An areostationary Relay Satellite at 17,000 km above Mars surface is always in the same place in the sky on Mars, receiving data from the rovers/landers and low Mars orbiters and transmitting it to an Earth station. The areostationary satellite enables almost all time communication, except for certain durations when Mars is in between the areostationary Relay Satellite and the Earth. In this paper we define a code division multiple access (CDMA) communication system between various assets such as rovers/landers on Mars surface, low Mars orbiters such as MRO, CubeSats in vicinity of Mars, and an areostationary relay satellite at 17,000 km above Mars surface. We assume data rates between 50 Kbps and 1 Mbps operating at 8.40 GHz frequency. We define the transmit power, antenna size, and data rates for the assets communicating with the areostationary relay satellite. Since the areostationary relay satellite simultaneously receives data from many users we have chosen the code division multiple access (CDMA) as a multiple access scheme, which does not require time/frequency coordination among users. Further-more we compute the link budgets for various communication links, we define the modulation format, the PN spreading and chip rates. We provide a new theoretical analysis for multiuser interference, and simulate the performance of coded CDMA communication system. For coded system we use standard CCSDS LDPC codes proposed by NASA for space applications. Using CDMA, the communication structure of all assets on Mars operates at one single RF frequency. However the initial states of spreading PN codes assigned to users are different such that if all users communicate simultaneously with the areostationary relay satellite over a given band will have low cross correlation that reduces the multiuser interference.