Research On QC-LDPC-Based MIMO Satellite Communication Systems

MIMO, this is multiple-input-and-multiple-output technology, is a major breakthrough in wirelesscommunication field. It facilites antennas on transmitter and receiver side, then uses advanced signalprocessing strategies in space to separate signals. It can enlarge system capacity and improveefficiency for spectrum without using wider spectrum. MIMO systems have advantages like highspectrum efficiency, wide range, low power and high reliability.Recently, MIMO system has come to its research and producing period. IEEE802.16e has set it asthe architecture of wireless communications. Researches about it have been fruitful on channelestimation, multiusage in space and so on. But current researches are often limited in MIMO itself,and have insufficient connection with LDPC and spreading. So our research on MIMO and the usageof LDPC and spreading on it is quite potential in study and application.The research work in this thesis mainly covers aspects as follows:1. Sum up the channel mode when antenna arrays are linear, and simplize it to a discrete-timememoryless mode under some conditions. Summarize the general principle of maximumlikelihood detection in MIMO systems.2. Analyze JML and three linear detection methods under assumption of known channel, on thebasis of which feedback methods are researched. Effection of channel property, such as angles ofreceived signals, transmitting amplitude, number of receiving antennas, is studied. Underassumption of unknown channel, adaptive methods are introduced into space field. The authorderived the MMSE best detection in adaptivity, analyzed gradient algorithm, and studied spatialLMS and RLS algorithm for detection and their instantaneous and steady-state characteristics.3. The author explored the suppression effect of addition of spreading codes on interference andnoise, analyzed principle and course of production of Gold codes, and added it into MIMOsystems. Then performance of MIMO plus spreading system is compared under non-adaptive andadaptive situations.4. Encoding and decoding methods of LDPC and QC-LDPC are studied, and simulations on thesecodes are made. So the effect of code length, code rate and decoding iteration numbers onperformance of LDPC codes could be researched. The author designed spreading MIMO systembased on LDPC code, and compared detection performance under known and unknown channel.