Optimizing antenna parameters for sectorized W-CDMA networks

We investigate the W-CDMA system capacity for different number of sectors per cell, different antenna opening angle and different antenna front to back ratio. First an analytical theory for she downlink and uplink system capacity is derived. The capacity is given as a function of the operating SIR, available power, thermal noise, pilot power orthogonality factor and the gain between the mobiles and the sector antennas. The gain affects the capacity by an integral (or in case of no power control, a max-function), which is identified as the often used loading factor. Hence a theoretical expression for the loading factor is derived. Next system simulations, including handover, power control and other CDMA characteristics, are performed. The optimal opening angle for a 3-sector cell is found to be 80° or 65° depending on how the antennas are directed. The optimal opening angle for a 6-sector cell is 40°. The optimal opening angle is insensitive to the orthogonality factor, the handover margin and the distance attenuation factor. Finally, the simulation results and the results derived by the theoretical model show good agreement