On Movement-based Location Update. A Lookahead Strategy

Abstract

This paper presents a lookahead strategy for a movement-based location update procedure that reduces the signaling traffic of the classical movement-based scheme. Our proposal is based on the observation that many trips of the mobile users are daily trajectories according to certain routines, for instance from home to the working place and vice-versa. Also we assume that the network can predict the mobile's position at the cell level. Based on those aspects, our scheme works as follows. If the mobile terminal visits an expected cell, a target cell, before a certain movement threshold M is reached, its movement counter is reset to zero. If the movement counter of the mobile terminal reaches the threshold M before visiting the target cell the mobile terminal will trigger a location update message. With this strategy, since mobile terminals have less contacts with the network, the uncertainty on their location increases and as a consequence of that, in order to keep the terminal paging cost below reasonable bounds, a selective polling strategy based on the expected trajectory of the mobile terminal should be applied. To that purpose a selective line-paging-Iike procedure is considered. Two step and three step paging procedures have been implemented. The net effect is a significant saving in the total signalling load (location update + paging) supported in the air interface. The assertion of this expected result has been carried out using a suitable Markovian analytical framework.