On optimizing the location update costs in the presence of database failures

This paper studies the database failure recovery procedure for cellular phone networks as part of the Electronic Industries Association/Telecommunications Industry Association Interim Standard 41 (EIA/TIA IS-41). Before the location information of the database is recovered, phone calls may be lost. The restoration process can be sped up by having the mobile phones to periodically confirm their existence by radio contact with the cellular network. We show that, under some cost assumptions, periodic update interval should be chosen to be approximately equal to the call interarrival time, with more frequent updates for more unreliable system. We also show that the cost of an optimized system is relatively small and stable, if the system is even moderately reliable. Finally, if the system is at least moderately reliable, the effects of call origination rate and the rate at which Location Areas are crossed, are rather small, assuming that the periodic update interval was chosen as stated above. Thus, in such cases, optimization of the size of the Location Area can be made independent of the optimization of the periodic update process.