The Research Of Multi-user Detection In MIMO Systems

Nowadays，the3G communication systems have passed through the standardization epochand forthcoming commercialization period. At the same time the4G mobile communicationtechnology is widely investigated. In order to improve bandwidth efficiency and cancel theinterference，the multiple access technique is recommended in wireless communicationespecially the Code Division Multiple Access technology. In Direct-Sequence Code DivisionMultiple Access(DS-CDMA) system，the channel bandwidth is shared by multiple users whoare distinct by different spread code. However, multiple access interference and multi-pathdistortion degrades the performance of DS-CDMA system. Therefore, many advanced digitalsignal process techniques are proposed to solve the Problem，which could be classified asMulti-user Detection and Space-Time processing.The Multi-user Detection technology provides a way to restrain the noise and interferenceat the receiver end. It helps demodulate the information form the CDMA signals reliably.Meanwhile, the MIM0Space-Time process takes advantages of the diversity gain which isprovided by the setting of several transmitting antennae and receiving antennae as well as theencoding gain. It can multiply the utilization rate of the frequency spectrum and increase thechannel capacity without additional signal power.The mathematics model and basic principleof Constant Modulus Algorithm (CMA) are shown firstly, then several CMAs proposedrecently and its principle and convergence behavior are reviewed systematically.By using the non-orthogonal signature between users, Multi-user detection technologycould eliminate the multi-user interference. It takes full advantage of the signal information ofall users, which causes the multi-address interference, to detects the signal of individual users,thus reducing. I and the effect of distance while decreasing the precision requirements by thepower control system. In this way, the resources of a link spectrum could he effectivelyutilized, and thereby the capacity of the system significantly enhanced. This thesis combinesthe Broaden-Fletcher-Goldfarb-Shannon (BFGS) algorithm with constant modulus algorithm, and proposes a BFGS Linearly Constrained Constant Modulus Algorithm (BFGS-LCCMA).This thesis proposes a subspace-based linearly constrained LSCM algorithm(SUB-LC-LSCMA). This thesis also introduced a MIMO (BLAST)-MC-CDMA downlinksystem and applied the two new proposed algorithms to the system.