Research On Uplink Access Technologies In GEO Satellite Communication System For LTE

With the rapid development of satellite mobile communication system, the developmenttendency of satellite mobile communication is bringing in3rdGeneration Partnership Project(3GPP) Long Term Evolution (LTE) and building a LTE mobile satellite communication system.Uplink access is one of core technologies of satellite communication system for LTE. Thecorrelative key technologies of uplink access affect the performance of the system directly. Thepaper regarded LTE uplink access key technologies as the breakthrough point, launched a morein-depth study of the random access technology, uplink synchronization technology and powercontrol technology. The main contents of the paper are as follows:1. A rapid random access method is proposed in orde to solve satellite communicationcharacteristics of large time delay. The algorithm introduced the idea of joint design, whichproposed special frame structure and streamline random send processes to adapt to the mobilesatellite communication system via referenced LTE random access technology and combinedrandomd access control information and random access preamble. Theory analysis andsimulation results show that probability of the frame received correctly and performance ofaverage access time is effectively improved, by reasonably seting guard time, cyclic prefix andcontrol information.2. Researched on the problem of long average access time in Geosynchronous Earth Orbit(GEO) satellite mobile communication system for LTE, an uplink time-slot synchronizationscheme based on cross-slot is proposed. Through combined with uplink timing synchronizationand the allocation of resources, this method determines the satellite uplink receiving frametiming reference by the transmission delay of the beam center users, and the user uplink time slotis cross-assigned according to users’ positions in the beam via allocated time slot in advance toremote users and lag time slot to near end uers. Theory analysis and simulation results show thatmethod is superior to the traditional performance lag of uplink synchronization method, whichreduces the waiting time of users with the premise of guarantee the Bit Error Ratio (BER)performance.3. A power control algorithm based on assignation is proposed combined with open loopand closed loop for the problem of power control inefficiency in satellite communication system.The algorithm first uses the open loop power control and user calculated the actual sendingpower for the first time to improve the effect of coarse control of power, which considered theinstant information of satellite channel, the satellite load conditions, uers’ location and quality ofservice. Secondly as to the signal to noise ratio in satellite communication, using assigned closed-loop power control to compensate error caused by open loop power control, whichobtained the optimal power control performance. Theoretical analysis and performancesimulation results show that the algorithm performance is superior to the conventional fixed steppower control algorithm, increasing the average access time performance and the correct useraccess probability and performance at the same time.