On multi-cell interference and capacity of the CDMA forward link with tracking beam antennae

The use of narrow tracking beam antennas at base stations provides a way to increase the capacity of CDMA cellular systems. The realistic capacity evaluation of such a system is still a challenge since multi-cell interference is hard to model, especially considering real-time power control and soft handoff. This paper proposes and compares both an analytical and a simulation approach in calculating multi-cell interference in the CDMA forward link with a transmission tracking beam antenna. The analytical method assumes a constant required E_b/N₀ for all users in the system to maintain a given quality of service, while the simulation approach takes the CDMA soft (and softer) handoff gain into account. The results show that the latter yields a more realistic interference power profile. To evaluate the capacity gain of the tracking beam system, the interference power profile is incorporated into an IS-2000 symbol-level user motion simulation. The simulations show that narrow tracking beam antennas can provide about 2.7 times capacity gain over a conventional tri-sector system