Effects of handoff margins and shadowing on the residence time in cellular systems with link adaptation

In mobile cellular systems with link adaptation (LA), different quality zones, in terms of the signal-to-interference ratio (SIR), can be distinguished within each cell. In this paper, the effects of the inter-cell and intra-cell handoff hysteresis margins and log-normal shadowing on the residence time in the different quality zones in mobile cellular systems with LA are evaluated. Contrary to the inter-cell handoff margin that refers to a difference of received signal strengths, the intra-cell handoff margin refers to a difference of signal-to-interference ratios, which is used to determine whenever intra-cell handoff is required. Comprehensive simulation results for a generalised mobility model and for several of the most commonly used assumptions in the literature are shown. Results show that as the (intercell or intra-cell) handoff hysteresis margin increases, the probability density function of the residence time in the cell or in the different quality zones is better fitted by a lognormal distribution than by a negative exponential one. Also, it is observed that as the mobility randomness increases, the pdf of the residence time in the quality zones for handed-off calls tends to a negative exponential distribution. Finally, it is observed that as the standard deviation of the lognormal shadowing increases, the mean residence time in the cells and in the different quality zones decreases.