Reducing signalling overhead in cell-hopping mobile wireless networks using location caches

In this paper, we propose and analyze a timer-based location caching scheme to reduce the signalling cost of on-demand location management in the context of a light-weight cellular wireless network architecture, called a cell-hopping network. The timer value is the most important control parameter of the proposed caching scheme. We derive a closed-form expression as a function of the message-to-mobility ratio (MMR), for the optimum timer value that minimizes signalling cost. Using numerical examples, we show that the signalling cost can be reduced by as much as 80% for reasonable MMR values, if the caching timer is set to the optimum value. Conversely, incorrectly selected timer values can nullify the use of the location cache.