A multicell model of handover initiation in mobile cellular networks

A model is provided for the analysis of handover initiation algorithms in cellular systems, which are based on the averages of signal strength measurements and hysteresis. An extension of Vijayan's and Holtzman's (1993) model is achieved, which accounts for: (1) the effects of the angular direction when a mobile terminal moves from a current to a target base station; (2) the presence of more than two base stations; and (3) the effects of cross correlation of shadow fadings affecting the links between the mobile terminal and the various base stations. The level crossing theory of Gaussian processes is used to derive the algorithm performance. The results obtained from the model are in good agreement with those obtained from simulations. It is seen that the model tends to underestimate the algorithm performance, thus yielding a lower performance bound and guaranteeing an intrinsic design margin. It is also seen that, for a typical trajectory of the mobile terminal from the current base station, the number of handovers might be noticeably increased due to the presence of disturbant stations. Moreover, when cross correlation among shadow fadings is also accounted for, significant variations are observed in both the number of handovers and handover delay. As a final result, tradeoff curves are derived and presented for the most general case.