Delay efficient data gathering in sensor networks

Data gathering is a very important functionality in sensor networks. Most of current data gathering researches have been emphasized on issues such as energy efficiency and network lifetime maximization; and the technique of data aggregation is usually used to reduce the number of radio transmissions. However, there are many emerging sensor network applications with different requirements and constraints. Rather, they are time critical, i.e., delivering sensed information of each individual sensor node back to a central base station quickly becomes most important. In this paper, we consider collision-free delay efficient data gathering problem in sensor networks, assuming that no data aggregation happens in intermediate nodes. We formally formulate this problem and propose optimal and near-optimal algorithms for different topologies. Particularly, in general topology, we present two approximation algorithms with performance ratio of 2 and 1+1/(k+1), respectively.