LIFO-backpressure achieves near-optimal utility-delay tradeoff

  • Authors:

  • Longbo Huang;Scott Moeller;Michael J. Neely;Bhaskar Krishnamachari

  • Affiliations:

  • Institute for Theoretical Computer Science and the Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing, China;Department of Electrical Engineering, University of Southern California, Los Angeles, CA;Department of Electrical Engineering, University of Southern California, Los Angeles, CA;Department of Electrical Engineering, University of Southern California, Los Angeles, CA

  • Venue:
  • IEEE/ACM Transactions on Networking (TON)
  • Year:
  • 2013

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Abstract

There has been considerable work developing a stochastic network utility maximization framework using Backpressure algorithms, also known as MaxWeight. A key open problem has been the development of utility-optimal algorithms that are also delay-efficient. In this paper, we show that the Backpressure algorithm, when combined with the last-in-first-out (LIFO) queueing discipline (called LIFO-Backpressure), is able to achieve a utility that is within O(1/V) of the optimal value, for any scalar V ≥ 1, while maintaining an average delay of O([log(V)]2) for all but a tiny fraction of the network traffic. This result holds for a general class of problems with Markovian dynamics. Remarkably, the performance of LIFO-Backpressure can be achieved by simply changing the queueing discipline; it requires no other modifications of the original Backpressure algorithm. We validate the results through empirical measurements from a sensor network testbed, which show a good match between theory and practice. Because some packets may stay in the queues for a very long time under LIFO-Backpressure, we further develop the LIFOp-Backpressure algorithm, which generalizes LIFO-Backpressure by allowing interleaving between first-in-first-out (FIFO) and LIFO. We show that LIFOp-Backpressure also achieves the same O(1/V) close-to-optimal utility performance and guarantees an average delay of O([log(V)]2) for the packets that are served during the LIFO period.