Performance Studies of Narrow-Beam Trisector Cellular Systems

Early cellular architectures consisted of base stations with omnidirectional antennas. Although directional antennas are widely used in current cellular /PCS (Personal Communication System) the system architecture is often still based upon an omnicell structure, and potential advantages of sectorization are not fully exploited. This paper analyzes and compares two different approaches to sectorization: the traditional wide-beam trisector cell (WBTC) and the newer (but not well characterized) narrow-beam trisector cell (NBTC). Unlike the WBTC architecture using three 100 8 ±120 8 antennas in a base station, the NBTC architecture (also called a clover-leaf o ) uses three 60 8 ±70 8 antennas at each base. We have obtained new results on the quantitative perform ance of both architectures, 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 in ̄ uences of reuse factor and shadow fading. We show that NBTC system performance exceeds that of WBTC systems, both in signal-to-interfer ence ratio (SIR) statistics and signal coverage. The improvement in coverage translates to 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. The improvement in SIR performance corresponds to a gain of 2±3 dB in the 90th SIR percentile. This gain can be translated to signi® cantly improved grade-of-service in cellular environments, with no attendant cost.