@article{warrier_janakiraman_ha_rhee_2009, title={DiffQ: Practical Differential Backlog Congestion Control for Wireless Networks}, ISBN={["978-1-4244-3512-8"]}, ISSN={["0743-166X"]}, DOI={10.1109/infcom.2009.5061929}, abstractNote={Congestion control in wireless multi-hop networks is challenging and complicated because of two reasons. First, interference is ubiquitous and causes loss in the shared medium. Second, wireless multihop networks are characterized by the use of diverse and dynamically changing routing paths. Traditional end point based congestion control protocols are ineffective in such a setting resulting in unfairness and starvation. This paper adapts the optimal theoretical work of Tassiulas and Ephremedes on cross-layer optimization of wireless networks involving congestion control, routing and scheduling, for practical solutions to congestion control in multi-hop wireless networks. This work is the first that implements in real off-shelf radios, a differential backlog based MAC scheduling and router-assisted backpressure congestion control for multi-hop wireless networks. Our adaptation, called DiffQ, is implemented between transport and IP and supports legacy TCP and UDP applications. In a network of 46 IEEE 802.11 wireless nodes, we demonstrate that DiffQ far outperforms many previously proposed "practical" solutions for congestion control.}, journal={IEEE INFOCOM 2009 - IEEE CONFERENCE ON COMPUTER COMMUNICATIONS, VOLS 1-5}, author={Warrier, Ajit and Janakiraman, Sankararaman and Ha, Sangtae and Rhee, Injong}, year={2009}, pages={262–270} }
 @article{rhee_warrier_aia_min_sichitiu_2008, title={Z-MAC: A hybrid MAC for wireless sensor networks}, volume={16}, ISSN={["1558-2566"]}, DOI={10.1109/TNET.2007.900704}, abstractNote={This paper presents the design, implementation and performance evaluation of a hybrid MAC protocol, called Z-MAC, for wireless sensor networks that combines the strengths of TDMA and CSMA while offsetting their weaknesses. Like CSMA, Z-MAC achieves high channel utilization and low latency under low contention and like TDMA, achieves high channel utilization under high contention and reduces collision among two-hop neighbors at a low cost. A distinctive feature of Z-MAC is that its performance is robust to synchronization errors, slot assignment failures, and time-varying channel conditions; in the worst case, its performance always falls back to that of CSMA. Z-MAC is implemented in TinyOS.}, number={3}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Rhee, Injong and Warrier, Ajit and Aia, Mahesh and Min, Jeongki and Sichitiu, Mihail L.}, year={2008}, month={Jun}, pages={511–524} }
 @article{warrier_park_min_rhee_2007, title={How much energy saving does topology control offer for wireless sensor networks? - A practical study}, volume={30}, ISSN={["1873-703X"]}, DOI={10.1016/j.comcom.2007.05.019}, abstractNote={Topology control is an important feature for energy saving, and many topology control protocols have been proposed. Yet, little work has been done on quantitatively measuring practical performance gains that topology control achieves in a real sensor network. This is because many existing protocols either are too complex or make too impractical assumptions for a practical implementation and analysis. A rule of thumb or a practical upper bound on the energy saving gains achievable by topology control would assist engineers in estimating the overall energy budget of a real sensor system. This paper proposes a new topology control protocol simple enough to permit a straightforward stochastic analysis and also a real implementation in Mica2. This protocol is currently deployed in our testbed network of 42 Mica2 nodes. Our contribution is not on the novelty of this protocol but on a practical performance bound we can study using this protocol. The stochastic analysis reveals that topology control can achieve a power gain proportional to network density divided by a factor of eight to ten. Our experiment result from the real testbed tests confirms this finding. We also find a tradeoff in terms of throughput loss due to reduced density by topology control which amounts to about 50% throughput loss. These performance figures represent rough rules of thumb on energy efficiency achievable even by a very simple, unoptimized protocol.}, number={14-15}, journal={COMPUTER COMMUNICATIONS}, author={Warrier, Ajit and Park, Sangjoon and Min, Jeongki and Rhee, Injong}, year={2007}, month={Oct}, pages={2867–2879} }