Predictive handoff scheme with channel borrowing based on the positioning of mobile stations

Abstract

Previously, we presented a predictive channel reservation (PCR) scheme for handoff motivated by the rapidly evolving technology of mobile positioning. In this paper, we investigate a new scheme, called PCR_CB, which is an extension of the PCR scheme by allowing channel borrowing from the neighboring cells. In PCR_CB, channel borrowing is invoked when the cell receiving reservation request cannot find any free channel. This is to take advantage of the situation that neighboring cells may have some idle channels at that moment. However, to avoid the negative impact of further depleting the channels of busy cells, the ratio of available channels to total number of channels (coldness index) is checked first on the potential lender cells. This implies the PCR_CB scheme predicts incoming traffic to each cell based on the extrapolated motion path of every single mobile station, and then re-allocate channels according to the traffic trends. Performance evaluation of the PCR_CB scheme is done by simulation. The result shows that PCR_CB outperforms the original PCR and GC schemes by a large margin on handoff blocking while new call blocking is virtually the same as PCR. Non-homogenous traffics, in which some hot cells may exist persistently, are also included in this study. Similar trend is observed as that of homogeneous traffic, although during high degree of non-homogeneity the reduction on the performance gain of PCR_CB can be clearly observed. PCR_CB is also shown to outperform the Channel Carrying scheme on the basis of performance optimization.