The Research Of CDMA Uplink Power Control Algorithms For LEO Satellites

The current Terrestrial Universal Mobile Telecommunication System(T-UMTS)is able to meet the need of communication service of the most residential area in our country because the wireless communication technology develops so fast.However,due to the vast territory in China where has huge marine areas and badlands areas,the T-UMTS is not able to provide communication service to these extreme or remote areas,and the Satellite Universal Mobile Telecommunication System(S-UMTS)becomes the primary communication choice for these areas.The low earth orbit(LEO)S-UMTS based code division multiple access(CDMA)is very suitable to provide communication service for these extreme or remote areas,because LEO satellites have many advantages such as low cost,small size and short developing period,and the CDMA standard also has some benefits such as simple frequency planning and good security.While there are the multiple access interference(MAI)and near-far effect in this communication system,it is necessary to thoroughly study the power control technology and this dissertation focuses on the power control optimal problem under the varying,long round-trip delay and time-varying channel.There are three power control scenarios(i.e.low power scenario,general scenario and high performance scenario)in LEO S-UMTS.This dissertation researched power control strategies for these three application scenarios.These power control strategy algorithms can well meet the power control demands of these different power control scenarios and give the basic theory knowledge for the research of the power control optimal problem.The power control of user terminals in LEO S-UMTS is badly influenced by the long round-trip delay and time-varying statistics of the satellite channel.In order to mitigate the effect of round-trip delay,this dissertation studied the time delay compensation(TDC)algorithms based Smith predictors to compensate the round-trip delay of the power update signal.In addition,this dissertation also studied the least mean square(LMS)adaptive filter to reduce the effect of the time-varying channel and proposed an improved power control algorithm which is combined with Smith predictors and LMS adaptive filters.It is clear that the improved power control algorithm proposed by this dissertation is more effective to mitigate the effect of the varying,long round-trip delay and time-varying channel than other algorithms.In addition to the research of power control strategies and time delay compensation algorithms,this dissertation also designed the power control system related to the uplink of S_UMTS,which includes the design of the architecture of the power control system,the design of the transmitter and receiver related to uplink,and the research of SINR estimation algorithms and gain step adjustment algorithms.Furthermore,this dissertation set up this power control system on the Simulink platform and gave a set of optimal parameters for the power control system.