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Cell sectorization has been shown as a promising technique to improve the overall capacity in direct sequence code division multiple access (DS-CDMA) systems. It has been further demonstrated that the use of adaptive antenna arrays with dynamic cell sectoring is particularly suitable for non-uniformly distributed users. In this paper, we first re-formulate cell sectoring into an optimization problem and solve it with dynamic programming algorithm. We next show that this has two major practical drawbacks: the complexity and oscillation of users between neighboring sectors. We then present an efficient Cluster-based Sectoring (CS) algorithm for adaptive cell sectorization to overcome these two inefficiencies: Firstly, the computation complexity of CS algorithm is much lower than that of the optimal sectoring algorithm. In particular under high-density case, the complexity is bounded and does not depend on the number of users in a cell; Secondly, the CS algorithm maintains the excellent property of avoiding sector boundaries frequently crossing those users closely located within short angular distances. In addition, we also investigate the support for multi-rate applications with the proposed CS algorithm. Through extensive experimental study, we find that the performance of proposed CS scheme obtains comparable performance with greatly reduced complexity when comparing to the optimal solution.