Joint Power Control Algorithm. Cdma System

CDMA (Code Division Multiple Access ) is one of the promising technology for futUfemobile conununication system because of its several featUrs with which other multipleaccess technology can not compare: higher efficiency of frequency allocation, robustani-multipath effect, macro diversity mitigating intefference, soft capacity low POwet, softhandoff simple frequency design, easy access, and so on. In CDMA conuntalcation system,the users are identified by their different spread speCtrUIn codes Which are unique to each user,namely they are identified by the cross correlation of sPread sPectruIn codes. If the correlationof fferent spread spectrUIn codes is not zero, ther would be multi-access interference.Additionally, CDMA conunwhcation system is a intefference-limited system, tha is to saythat the interference directly influences the caPabi1ity of dris system and the QoS of the userin the system. In order to rid the nearfar problem and muti-access intehae, POwercontrol plays an impohan role.The power control algorithm used in Present CDMA conunwhcation standar (fOrexamle, IS-95A and CDMA2000) is to allocate ophmal power vector for the user in thesystem sboply by the distance betWen the base station and the user under a Predefined norm(fOr examPle, the transmitted POwer of user or the Signalto-Interfrence Ratio(SIR receivedby the base station suffice to some a nddriZation norm ),. Traditional POwer contrOlalgorithIn is to use a convergent iteration fimtion to set uP a mathematical model. When suchmethod is used to control the POwer of user, we shOuld find the optimum solution vector ofthe convergent iteration funhon by iteration transform. The defect of thes powe contrOl andallocation method is without consideraon of the induence of all of the other users on thedesired user and the influence of time-varying channel, so it can not maximize the caPacity,and deduces the frequency waste. In a word, it is important to improve the presen powercontrOl technology to peffect the Pefformance.In this paPer, the model of the traditional POwer control aigoritIun used in CDMA systemis expanded. With the perf0rmance of the multiuser deteCtion introduced into the powercontrOl, the improvement of the caPability is discussed. Moreover, the concePt is used into thePOwer control algorithm based on game theory with consideration of the tboe-varyingchaIml, three strategies of power control are proposed: (l) the joint power contrOl algorithmbased on the multiuser detection; (2) the joint power control algoritlun based on the gametheory; (3) the joint power control algoritlun based on channel estimation.In chapter 4, a joint power control algorithIn is proposed, in which the perfOrmance ofmuhuser detection and the itefation mechanism of the coefficients of receiver filter inmulhuser detection are considered, and a new joint power control algorithIn based on MMSEmultiuser detection is proposed finally. In chaPter 6, a joint power control algorithIn based ongame theory using the concept of the joint power control is put forward. The simulationresultS show that the joini power cothel algorithIn can improve the Signal-to-Interferenceboo of the system and increase the caPacity of system. In order to really describe thetime-varying featUre of the channl, in chaPter 7, Kaiman filter is used to timely eStimate thechannl parameters and the PerfOrmance of POwer control is imProved with consideration ofthe chaIml parameters estimatd in POwer contrOl algorithIn.The simulation experiments show tha it is because the pefformance of multiuser detectionis Wuced into power contrOl that the request on powe contrOl is reduced, the perfrmanceof POwe contrOl is imProved and the system caPacity and QoS of users are etwed.