Use of Adaptive Sectorisation for Capacity Enhancement in CDMA Cellular Systems with Non-Uniform Traffic

This paper discusses the application of adaptive sectorisation in the capacity enhancement of a CDMA cellular system dealing with non-uniform traffic. It considers the particular case where the traffic distribution consists of isolated areas of congested traffic called Hot Spots (HS). It is envisaged that the traffic density inside a HS is many more times that outside the HS. A more even traffic distribution among sectors is attempted by re-adjustment of sector boundaries using finite antenna beam switching. System capacity is estimated on the basis of tolerable interference in a sector taking into account of both intrasector and intersector interference in a multicell environment. Interference is evaluated under the assumption of perfect power control in the uplink. Normal propagation environment is assumed in the cell that allows path losses and shadowing losses in the mobile radio signal. Variation in the antenna gain is also accommodated by taking appropriate radiation pattern into account. It is shown that successive sector adjustment with increasing HS traffic intensity can deter call blocking in the HS sector. It is also shown that a significant improvement in system capacity could be obtained with adaptive sectorisation particularly when the HS user density is several orders of magnitude higher than that outside the HS.