Mobile Intelligence

9.6 SUMMARY

This chapter has presented air index techniques for energy conservative query processing in wireless data broadcast environments. We briefly reviewed basics of wireless data broadcast and data organization under air indexes. Indexes for nonspatial data, for example, tree-based index, hashing-based index, signature-based index, hybrid index, and exponential index, were described. In the air index for spatial data, HCI and DSI based on Hilbert Curve, a kind of space-filling curves, were described in detail. The indexes have various problems, long broadcast cycle by their big size and listening to redundant data items by filtering queried data items after accessing candidates determined on Hilbert Curve. In this chapter, we presented CEDI. CEDI has much reduced size by keeping pointers of groups of data items by n × n grid, instead of the pointer of each data item. CEDI has distributed structure and supports multiple access paths by the replication of the pointers of data groups. CEDI eliminates listening to redundant data items during the processing of window query by filtering out the queried data items using original coordinates their before accessing them. CEDI is very efficient in the aspect of energy conservation and access time. Moveover, CEDI has the robustness for link-error in error-prone wireless transmission environments.