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In this letter, we propose a GRid-based Indexing scheme on Multiple channels (GRIM) for processing spatial window queries in non-flat wireless spatial data broadcasting. When the clients access both popular and regular items simultaneously, GRIM provides the clients with improved access time by broadcasting popular items separately from regular ones in units of grid cells over multiple channels. Simulations show that the proposed GRIM outperforms the existing indexing scheme in terms of the access time.
This letter proposes a Cell-based Hybrid Index (CHI) for energy conserving k Nearest Neighbor search on air. The proposed CHI provides global knowledge on data distribution for fast decision of the search space and local knowledge for efficient pruning of data items. Simulations show that CHI outperforms the existing indexing schemes in terms of tuning time and energy efficiency. With respect to access time, it outperforms them except the distributed indexing scheme optimized for access time.
This letter proposes an Index based on Irregular Partition of data identifiers (IIP), to enable clients to quickly access multiple data items on a wireless broadcast channel. IIP improves the access time by reducing the index waiting time when clients access multiple data items, through the use of irregular partitioning of the identifier space of data items. Our performance evaluation shows that with respect to access time, the proposed IIP outperforms the existing index schemes supporting multiple data access.
This letter proposes a Non-uniform Cell-based Index (NCI) to enable clients to quickly process window queries in the wireless spatial data broadcast environment. To improve the access time, NCI reduces the probe wait time by equalized spacing between indexes, using non-uniformly partitioned cells of data space. Through the performance evaluation, we show the proposed NCI outperforms the existing index schemes for window queries to spatial data in respect of access time.
SeokJin IM MoonBae SONG Sang-Won KANG Jongwan KIM Chong-Sun HWANG SangKeun LEE
This letter proposes a group-based distributed air index (called GDI) using two-leveled groups by partitioning the identifiers of data items to reduce the size of the index. GDI provides both global and local views of data items and multiple pointers to data items in a single access to an index. Simulation results show that GDI outperforms the existing index in terms of multiple data access, energy conservation and data waiting time.
To support the processing of spatial window queries efficiently in a non-flat wireless data broadcasting system, we propose a Two-Tier Spatial Index (TTSI) that uses a two tier data space to distinguish hot and regular data items. Unlike an existing index which repeats regular data items located near hot items at the same time as the hot data items during the broadcast cycle, TTSI makes it possible to repeat only hot data items during a cycle. Simulations show that the proposed TTSI outperforms the existing scheme with respect to access time and energy consumption.