Performance enhancement of DS-CDMA system using overlapping sectors with interference avoidance

A cellular system with overlapping sectors is proposed to enhance system performance through interference avoidance. Due to the overlapping effect, each user is allowed to select one sector out of many for operation. It is shown that the mutual interference among users in different regions within a cell can be minimized by choosing a good sector combination. The potential benefits of the proposed technique are investigated in two scenarios: orthogonal and nonorthogonal code division multiple access systems. In the former case, it is shown that when compared with the traditional nonoverlapping sectors system, one is able to reduce the number of spreading codes required to support all users by using appropriate code allocation in the proposed system. A theoretical framework based on combinatorial enumeration is developed to assess the performance of the proposed system. For the latter case, the enhancement takes the form of multiple access interference reduction. Simulation results show that its improvement is significant and can be further enhanced by increasing the number of overlapping sectors.