1. Hierarchical LR scheme See my paper with Gopal Dommety on general mobile location management

2. Variants of overlay approach: move operation Level S location database Level L-1 location database Level L location database (also home location database) Level L location database Level L location database Level L location database Level S location database Home Switch Visiting Switch Register Register (needed if first appearance at this Level S LD) Register (hierarchy limits level to which this is needed) S = 1... L Register New visiting Switch Register Home location database tracks Sth level location database of mobile Cancel

3. Variants of overlay approach: find operation Level S location database Level L-1 location database Level L location database (also home location database) Level L location database Level L location database Level L location database Level S location database Home Switch Visiting Switch Originating Switch Other Switch Other Switch Find

4. Attributes If S = L, then it means there are only VLRs and HLRs – cellular scheme If S = 1, then a full tree structure – don’t need concept of home location databases Tree structure limits registration propagation as well as find propagation Need to cancel at old sub-tree during move