Supporting Multi-dimensional Query In Mobile P2P Networks

In the past few years, P2P technology has been widely applied into the area of file sharing: a large number of people use P2P softwares for sharing music files, video files, etc. in Internet. The popularity of P2P file sharing systems is due to the advantages of P2P technology, including: scalability, low maintenance cost, and resource aggregation. With the advance in mobile wireless communication technology and the development of various mobile devices, P2P file sharing systems have been evolved in two aspects: their networking environment is changed from wired P2P network into mobile P2P network and their task is changed from providing simple lookup into supporting complex queries. The resulting advanced systems are referred to as mobile P2P multi-dimensional search systems. Compared to wired P2P network, mobile P2P network provides a more constrained communication environment, which is characterized by much more limited bandwidth, higher rate of transmission errors, less stable connections and dynamic network topology. Working in such an environment, search systems should be topology-aware and adaptive. That is, they should take advantage of the physical topology of the network to achieve shorter physical length of query routing path and adjust themselves to the topology changes of the underlying mobile P2P network. Designed for wired P2P networks, existing P2P search systems are neither topology-aware nor adaptive, so they would not work efficiently in mobile P2P networks.To efficiently support multi-dimensional search in mobile P2P networks, we propose a novel scheme called Multi-dimensional Index in Mobile Environment (MIME). First, considering the constrained communication environment provided by mobile P2P networks, MIME adopts a new communication cost model. This cost model measures the cost of executing a query in terms of the physical distance of its network layer path, instead of the number of its overlay hops. Second, MIME captures the physical topology of the network in a two-dimensional plane and keeps records of the physical locations of the nodes in order to construct a topology-aware P2P overlay. Third, MIME incorporates two adaptive features: an update algorithm that makes dynamic updates to the overlay when the physical network layout changes, and a cache mechanism that reduces the load of data migration during the updates to the overlay. Experiment results show that MIME achieves significant performance improvements in point/range queries compared to the conventional system.