Research On Doa Estimation Algorithms Of WCDMA System

The direction finding technology of WCDMA system is an important application of DOA estimation and has important researchvalue in the fields of wireless location and beamforming. In terms of the study of WCDMA system’s direction finding technology, a sheer volume of schemes and algorithms have been proposed. For example,Bartlett,Capon,MUSIC and so forth. However, the former two algorithms have lower precision and worse applicability while the latter is limited by the signal coherence as well as the source number can not exceed the number of array elements although it has higher precision.Taking the two problems of signal coherence and limited source number in the DOA estimation as the central point of this dissertation,a direction finding algorithm which can be applied to WCDMA multi-user system is proposed based on the existing model of uniform linear array. Thereby the main content of research work are as follows:First, analyzed the traditional DOA estimation algorithms such as Bartlett,Capon algorithm and MUSIC algorithm and the performance in signal coherence environment of these algorithms are also analyzed by computer simulation respectively.Second, aiming at addressing the coherence problem of MUSIC algorithm,the original of coherence solution using spatial smoothing algorithm is analyzed in detail and the advantage on number of array element of the two-dimensional spatial smoothing algorithm compared with the prior and after the spatial smoothing algorithm are also analyzed by simulation.By constructing sub-array to solve the coherence, spatial smoothing algorithm lost the array aperture and the maximum number of sources it can accept has certain quantitative relationship with the element number of antenna array.Whereas, compared with one-way smoothing, two-way spatial smoothing method can solve the coherence problem under the condition of same signal sources.Third, on the basis of former parts,a scheme to complete direction estimation on PRACH channel of WCDMA system is presented.Different from the traditional algorithms which completed the direction estimation in traffic channel, it utilizes the messages transferring in PRACH channel to estimate the direction which no longer need the whole voice communication link. Therefore, direction finding and location can be done under the condition of users’ unawareness.Last,a search algorithm based on uniform linear antenna array is proposed in view of the scheme on PRACH channel.Combined with the synchronization process of random access channel,this algorithm,it can search the position of the maximum correlation peak during the process of moving correction which is aiming to get the maximum peak and time-delay after signal received by using location angle weights. Then the direction of target user can be estimated.The search algorithm proposed in this dissertation has successfully tackled the problems of limited array elements and direction finding of signals in coherence environment.Under single way condition,the performance of search algorithm is a little bit worse than MUSIC but it can achieve a less DOA estimation bias when facing the two problems aforementioned.