Performance Studies of Narrow-Beam Trisector Cellular Systems

Early cellular architectures consisted of basestations with omnidirectional antennas. Althoughdirectional antennas are widely used in currentcellular/PCS (Personal Communication System) the systemarchitecture is often still based upon an omnicellstructure, and potential advantages of sectorization arenot fully exploited. This paper analyzes and comparestwo different approaches to sectorization: thetraditional wide-beam trisector cell (WBTC) and the newer(but not well characterized) narrow-beam trisector cell(NBTC). Unlike the WBTC architecture using three100-120° antennas in a base station, the NBTCarchitecture (also called “clover-leaf”) usesthree 60-70° antennas at each base. We have obtainednew results on the quantitative performance of botharchitectures, taking into account the impact of (1)actual (rather than ideal) antenna patterns, (2)channel utilization factor, (3) site diversity, (4)nonideal cell site locations, and (5) the influences ofreuse factor and shadow fading. We show that NBTC system performance exceeds that of WBTC systems, bothin signal-to-interference ratio (SIR) statistics andsignal coverage. The improvement in coverage translatesto a reduced power requirement of about 2 dB for the same cell size, or equivalently, to a 25%larger cell coverage area for the same power. Theimprovement in SIR performance corresponds to a gain of2-3 dB in the 90th SIR percentile. This gain can be translated to significantly improvedgrade-of-service in cellular environments, with noattendant cost.