Adaptive cell sectoring using fixed overlapping sectors in CDMA networks

The problem of base station antenna assignment (BSAA) with minimum mobile transmit power (MTP) is studied for CDMA networks that employ fixed overlapping sector antenna architecture (FOSAA). It is noted that the non-FOSAA has limitations in switching users between in-cell sectors and also out-of-cell sectors in moderately loaded networks. It is then shown that by employing overlapping sectors in FOSAA, we can exploit the flexibility of assigning a user to one of possibly many potential antenna to effectively support the non-uniform angular traffic. It is also proven that the problem of selecting a set of antenna from a pool of overlapping antenna and assigning the users to them in FOSAA with minimum MTP is a special case of a general problem that was solved by Hanly (1995) and Yates (1995). The process of dynamic cell sectoring is differentiated two-fold as cell-breathing (CB) and cell-slicing (CS) and the latter can be viewed as azimuthal counterpart of the former radial scheme. The hybrid scheme, CB+CS, is shown to yield the optimal solution in minimum total MTP in a CDMA/FOSAA system. The performance results for the total MTP and the received signal quality are reported. As the congestion level increases, the difference in SIR performance between CB and CS schemes becomes more apparent with the latter outperforming the former. The performance results also show that on average, the CB scheme requires about 30% more power than in CB+CS, when 60% of the mobiles are concentrated in a hot-spot sector in a conventional 3-sector cell