The document discusses energy efficient techniques for data collection in wireless sensor networks using TDMA protocols. It first reviews related work on constructing efficient data gathering trees and exploiting spatial-temporal correlations. It then examines the fundamental limitations of interference and half-duplex radios with TDMA. The paper proposes a fast convergecast algorithm for tree-based WSNs using TDMA to minimize schedule length and addresses techniques to overcome interference limitations. In conclusion, the algorithm is found to be energy efficient for data collection in WSNs using TDMA protocols.