Research And Implementation On Index Technology In Mobile Datacasting

The mobile database field has a widespread market application foreground as a core component of the presently mobile computing environment in development and application. To use the communication asymmetry between server and clients, the server broadcasts some hot datas periodically which is so called datacasting technology. To solve the problem of large scale of mobile clients and network communication asymmetry is the primary purpose of datacasting. The mobile database has a set of broadcast disks, the broadcast servers which located in stable hosts broadcast hot datas to local computers termly and the cost is independent of the amount of mobile clients.Data broadcasting structure determines what kind of data structure will be transmitted to mobile customer which consists of index structure and organization type of data in broadcasting singal path. We can put index into broadcast to reduce tuning time while the additional index increase the length of broadcast message and then increase the accessing time. So the index mechanismresearches to reduce tuning time at the same time assure accessing time in a proper boundary which can save on electricity and reduce latency time.This thesis compares indexical broadcast with indexless broadcast technology, after that, provide a new optimization indexical broadcast structure based on many kinds of index structures. Through theoretical analysis by means of access time and tuning time, the new indexical structure can adapt to the change of dada access probabilities more and more, the average accessing performance of mobile users is optimized. Introduces some contents that connected with the capability of multichannel data accessing, such as broadcast priority definition,attemper strategy in multichannel circumstance and so on. Sum up data accessing conflict data distribution and disk matching in multichannel data broadcast concisely. Illustrate proper data distribution to decrease data average accessing time to a low level in datacasting disks and then to save mobile computer's electricity and bandwidth. Finally, we provide a highly efficient data and index organization structure of mobile database broadcasting to environmental multichannel and design the simulation experiment. The results of simulation reveal that the new structure is superior to grade data broadcasting in aspect of decrease of average expectation, which can apply to complicated multichannel data broadcasting environment compatibly.