Improvements On The Index For The Broadcast Scheduling

Mobile database is a database system which is embedded in a mobile device. It keeps touch with centric database server with wireless method. It downloads data from the server in down channel, and uploads the local modifications to the server in up channel.In an asymmetric communication network, broadcast is an effective transmitting mode. The server can support a large scale of clients, save channel bandwidth and server processing resources, and make the clients get the required data via broadcast.In the broadcast, access probabilities of data items is skewed, therefore the index tree may be built through access probability. A mobile client listens to the index to determine when its interested data items will be broadcasted. Then it can go to sleep until just before the designated data items are broadcasted. The mobile client then listens to the wireless channel again to retrieve its interested data items.There are such two methods for adding index to broadcast scheduling. One is that clients cache data and index, the other is that the Huffman tree is improved so that don't require equal size for both index and data, don't restrict index channel's number and mark data modification. These methods'performance analysis shows that it significantly decreases the average access and tuning times for the broadcast data over existing methods.