Code Design for Fast Selective Retrieval of Fusion Stored Sensor-Network/Time-Series Data
Sharadh Ramaswamy, Jayanth Nayak, Kenneth H. Rose · 2007
We consider the problem of storing data from multiple correlated sources in a database, so as to enable efficient future retrieval of data from select subsets of the sources, where only statistical information about queries may be available in advance. This setting poses new challenges in terms of the precise tradeoffs between storage rate, retrieval rate and distortion. We derive a gradient descent algorithm to optimize the joint encoding (storage) procedure, the decoder, and the retrieval procedure via mapping from queries to subsets of the stored data to retrieve and decode, so that the average retrieval rate-distortion cost is minimized, given a pre-specified overall storage capacity (or rate). Experiments conducted on real and synthetic data-sets demonstrate that our selective retrieval procedure is able to achieve significantly better trade-offs than joint compression, with retrieval speed-ups reaching 5X and distortion gains of up to 3.5 dB possible.