The Effects of Varying Soft Handoff Thresholds in Cellular CDMA System


IEICE TRANSACTIONS on Communications   Vol.E87-B   No.4   pp.807-815
Publication Date: 2004/04/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Fundamental Theories
soft handoff,  code division multiple access (CDMA),  forward-link capacity,  load balance equation,  cell-breathing,  

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In order to benefit from the advantages of soft handoff (SHO), it is important that the SHO parameters (the SHO thresholds; T_ADD and T_DROP are well assigned. T_ADD is the threshold used for triggering a pilot with high strength to be added to the Active Set (AS) list. The AS means the pilots associated with the forward traffic channels assigned to mobile station. In contrast, T_DROP is the threshold used for triggering a pilot with low strength to be dropped from the AS list. This paper analyzes the effects of varying SHO thresholds in a cellular code division multiple access (CDMA) system on the blocking probability based on traffic load and geometrical distances in hexagonal layout of base stations (BSs). In addition, the previously proposed traffic load equation is applied to the proposed SHO model for balancing the numbers of new and handoff calls on the forward link capacity in case of uniform traffic load. The results show that the blocking probability is more sensitive to T_DROP than to T_ADD variations.