Efficient Approximation Algorithm for Data Retrieval with Conflicts in Wireless Networks

Given a set of data items broadcasting at multiple parallel channels, where each channel has the same broadcast pattern over a time period, and a set of client's requested data items, the data retrieval problem requires to find a sequence of channel access to retrieve the requested data items among the channels such that the total access latency is minimized, where both channel access (to retrieve a data item) and channel switch are assumed to take a single time slot. As an important problem of information retrieval in wireless networks, this problem arises in many applications such as e-commerce and ubiquitous data sharing, and is known two conflicts: requested data items are broadcast at same time slots or adjacent time slots in different channels. Although existing studies focus on this problem with one conflict, there is little work on this problem with two conflicts. So this paper proposes efficient algorithms from two views: single antenna and multiple antennae. Our algorithm adopts a novel approach that wireless data broadcast system is converted to DAG, and applies set cover to solve this problem. Through Experiments, this result presents currently the most efficient algorithm for this problem with two conflicts.