Cost implications of mobility management

Mobility management is concerned with how the network supports subscribers in making and receiving services as they roam. In cellular networks, mobility is implemented by the use of home location register (HLR) and visitor location register (VLR) databases. In cellular networks, future cell sizes may be smaller than the floor of a building and therefore cell boundaries will be crossed more often, increasing the number of location updates. It is expected that this and other things will have a significant effect on the scale of the mobility management problem and therefore the cost of mobility. Research to date has largely considered the cost of mobility in terms of the number of signalling messages generated. However, while this is an important factor, it does not give an accurate measure of the total cost of mobility. It is argued that the cost of mobility can be broken down into communication costs and database costs. In estimating the communication costs, the number of hops which the signalling messages traverse must be taken into consideration, together with the number of signalling messages. Clearly the location of the HLR and VLRs in relation to the source of the messages has implications for the communication costs. A new approach to mobility management is presented. The emphasis is on reducing the length of the route taken by the signalling messages and it is argued that this reduces the overall load on the signalling network. The scheme is suitable for 2nd and 3rd generation networks