Study On The Channel Capacity And The Space Time Coding Under Mimo Satellite Channel

Due to the crowded orbits and shortage of frequency resources, using MIMO technology to improve spectrum efficiency,increase the capacity of satellite communication systemand take full advantages of wide coverage and strong comprehensive business ability has become a necessary trend of broadband satellite communication.The main research of this paper is on capacity of MIMO satellite communication channelandspacetime coding technology as well as its performance analysis under land mobile satellite(LMS) channel. By using Markov chain and combining with transmission characteristic and statistical characteristic of mobilesatellitecommunication channelwe build up the four statesmobile satellite channel model firstly, whichcan reflect the actual signal propagation process in that the signal may encounter multipath, shelter, etc.On the basis of that, the main emphasis is placed on the channel capacity in MIMO satellite communication system and the effects of the factors, such as antenna numbers, terminal environments and elevation angles. We provide many simulation results to illustrate the effects of these factors through comparisons of the transmit rate, ergodic capacity and outage capacity with different factor values. In this paper, we also study the encoding and decoding methods of space-time coding in detail, and we analyze the main influenced factors and compare the BER performance of spacetime block code(STBC) scheme and spacetime trellis code(STTC) scheme. Simulation results show that performance of STBC and STTC under Rayleigh channel is obviously improved with the increase of transmitting and receiving antennas numbers, and the number of STTC encoder states has little impact on the performance of STTC.At last, based on the study above, we combine the MIMO LMS channel with spacetime coding schemes to emphatically study the BERperformance of STTC and STBC under MIMO satellite channel. Throughsimulation results obtained by selecting different parameters, including terminal environments and elevation angles, we analyze influenceof these factors on the system performance.Under the LMS channel, performance of these two kinds of spacetime coding in open area is optimal,and worst in urban area. But no matter under what circumstances, performance of STTC is slightly superior to the performance of STBC. Under the same environmental conditions, BER of STBC and STTC reduces with the increase of the satellite altitude angle, and the BER curves of STTC fall faster.