Channel Alternation and Rotation in Narrow Beam Trisector Cellular Systems

Two 60 Narrow-Beam Trisector Cell (NBTC) frequency reuse plans, 1x(3+1) and 2x(3+1), that employ Channel Alternation and Rotation (CAR) scheme are presented. In CAR, each cell type is allocated one extra channel set that allows network designer to rotate and alternate channels according to nearest front lobe interference avoidant strategy to enhance co-channel interference ratio (C/I) and allow deployment of tighter and non-integer reuse factors thus increase system capacity. For a typical cellular system that requires C/I of 14 dB, 2x(3+1) reuse plan increases system capacity by 12.50% over current frequency reuse plans. For system that requires 9 dB or less, 1x(3+1) reuse plan still provides at least one sector separation interval between co-channel sectors and mobiles that, if employed, can increase system capacity up to 125%. CAR is simple and can be deployed in current trisector cellular systems without any modification to the base station (BS) equipment thus imposing no additional cost.