WANG etaL:OPPORTUNISTIC ENERGY-EFFICIENT CONTACT PROBING IN DELAY-TOLERANT APPLICATIONS 1605 [5]A.Chaintreau,P.Hui,J.Crowcroft,C.Diot.R.Gass,and J.Scott. [28]G.Zaruba and I.Chlamtac,"Accelerating Bluetooth inquiry for per- "Impact of human mobility on the design of opportunistic forwarding sonal area networks,"in Proc.IEEE GLOBECOM,2003,pp.702-706. algorithms,"in Proc.IEEE INFOCOM,2006,pp.1-13. [29]N.Bisnik.A.Abouzeid,and V.Isler,"Stochastic event capture using [6]M.Motani,V.Srinivasan,and P.Nuggenhalli,"Peoplenet:Engi- mobile sensors subject to a quality metric,"in Proc.ACM MobiCom. neering a wireless virtual social network,"in Proc.ACM MobiCom. 2006,pp.98-109. 2005,Pp.243-257 [30]P.Barford and M.Crovella,"Generating representative web workloads [7]A.J.Campbell,S.B.Eisenman,N.D.Lane,E.Miluzzo,and R.A. for network and server performance evaluation,"in Proc.ACM Sigmet- Peterson,"People-centric urban sensing,"in Proc.WICON,2006,vol. rics/Performance,1998.pp.151-160. 220.Article No.18. [31]J.Polastre,J.Hill,and D.Culler,"Versatile low power media access [8]H.Y.O.Wolfson,B.Xu,and H.Cao,"Search-and-discover in mobile for wireless sensor networks,"in Proc.ACM SenSys,2004,pp.95-107 p2p network databases."in Proc.IEEE ICDCS.2006.pp.65-73. [9]M.Kuhn and R.Wattenhofer,"Community aware mobile networking," in Proc.Ist Workshop on Mobile Services and Personalized Emviron., Wei Wang (S'06-M'09)received the Ph.D.degree 2006pp.1-14. in electrical and computer engineering from the Na- [10]V.Srinivasan.M.Motani.and W.T.Ooi."Analysis and implications tional University of Singapore in 2008 of student contact patterns derived from campus schedules,"in Proc. He is currently with Microsoft Research Asia,Bei- ACM MobiCom,2006,pp.86-97. jing,China.His research interests are in the area of [11]A.Natarajan,M.Motani,and V.Srinivasan,"Understanding urban in- wireless networking. teractions from Bbluetooth phone contact traces,"in Proc.PAM,2007, pp.115-124. [12]J.Su,A.Chin,A.Popivanova,and E.d.L.A.Goel,"User mobility for opportunistic ad-hoc networking,"in Proc.IEEE WMCSA,2004,pp. 41-50. [13]N.Eagle and A.Pentland,"Social serendipity:Mobilizing social soft- ware,"IEEE Pervasive Comput.,vol.4,no.2,pp.28-34,2005. [14]A.Chaintreau,P.Hui,J.Crowcroft,C.Diot,R.Gass,and J.Scott. "Pocket switched networks:Real world mobility and its consequences Mehul Motani (S'92-M'00)received the B.E.de- for opportunistic forwarding."Univ.Cambridge,Cambridge,U.K.. gree from Cooper Union,New York,the M.S.de- 2005,Tech.Rep.No.617. gree from Syracuse University,Syracuse,NY,and the [15]S.M.Ross.Stochastic Processes.New York:Wiley,1983 Ph.D.degree from Cornell University.Ithaca,NY,all [16]S.Boyd and L.Vandenberghe,Convex Optimization.Cambridge. in electrical and computer engineering. U.K.:Cambridge Univ.Press,2005. He is currently an Assistant Professor in the Elec- [17]G.He and J.Hou,"An in-depth,analytical study of sampling tech- trical and Computer Engineering Department at the niques for self-similar internet traffic,"in Proc.IEEE ICDCS,2005. National University of Singapore.Previously,he was Pp.404413 a Research Scientist at the Institute for Infocomm Re- [18]W.Leland,M.Taqqu,W.Willinger,and D.Wilson,"On the self-sim- search in Singapore for three years and a Systems En- ilar nature of ethernet traffic,"IEEE/ACM Trans.Netw.,vol.2,no.1, gineer at Lockheed Martin in Syracuse,NY,for over pp.1-15,Feb.1994. four years.Recently,he has been working on research problems that sit at the [19]J.Beran,Statistics for Long-Memory Processes.London.U.K.: boundary of information theory,communications,and networking,including Chapman Hall,1994. the design and analysis of wireless ad hoc and sensor network systems. [20]M.McNett and G.M.Voelker,"Access and mobility of wireless PDA Dr.Motani was awarded the Intel Foundation Fellowship for work related to users,"Mobile Comput.Commun.Rev.,vol.9,no.2,pp.40-55,2005. his Ph.D.in 2000.He has served on the organizing and technical program com- [21]A.Papoulis and S.U.Pillai,Probability.Random Variables and Sto. mittees of ISIT,MobiCom,INFOCOM,SECON,and various other conferences. chastic Processes,4th ed.New York:McGraw Hill,2002. He participates actively in the IEEE and Association for Computing Machinery [22]R.Shah,S.Roy,S.Jain,and W.Brunette,"Data mules:Modeling and has served as the Secretary of the IEEE Information Theory Society Board a three-tier architecture for sparse sensor networks,"in Proc.IEEE of Govemors. SNPA,2003.pp.30-41. [23]P.Hui,A.Chaintreau,J.Scott,R.Gass,J.Crowcroft,and C.Diot, "Pocket switched networks and human mobility in conference environ ments,"in Proc.ACM SIGCOMM Workshop on Delay-Tolerant Netw.. Vikram Srinivasan (M'03)received the Bachelor 2005,Pp.244-251. of Science degree in physics from the University of [24]T.Gross and C.Tuduce,"A mobility model based on WLAN traces Chennai,Chennai,India,in 1994;the M.E.degree in and its validation,"in Proc.IEEE INFOCOM,2005.pp.664-674. electrical communications engineering from the In- [25]W.-J.Hsu,T.Spyropoulos,K.Psounis,and A.Helmy,"Modeling dian Institute of Science,Bangalore,India,in 1998: time-variant user mobility in wireless mobile networks,"in Proc./EEE and the Ph.D.degree in electrical and computer NF0C0M2007,Pp.758-766. engineering from the University of California at San [26]L.-J.Chen.Y.-C.Chen.T.Sen.P.Sreedevi.K.-T.Chen.C.-H.Yu. Diego in 2003. and H.-H.Chu,"Finding self-similarities in opportunistic people net- He was an Assistant Professor in the Electrical works."in Proc.IEEE INFOCOM,2007,pp.2286-2290. and Computer Engineering Department,National [27]C.Drula,"Fast and energy efficient neighbour discovery for oppor- University of Singapore,from 2003 to 2007.He is tunistic networking with Bluetooth."Master's thesis.Univ.of Toronto. currently with Bell Labs Research,Bangalore,India.His research interests are Toronto,ON,Canada,2005. broadly in the area of wireless networks.WANG et al.: OPPORTUNISTIC ENERGY-EFFICIENT CONTACT PROBING IN DELAY-TOLERANT APPLICATIONS 1605 [5] A. Chaintreau, P. Hui, J. Crowcroft, C. Diot, R. Gass, and J. Scott, “Impact of human mobility on the design of opportunistic forwarding algorithms,” in Proc. IEEE INFOCOM, 2006, pp. 1–13. [6] M. Motani, V. Srinivasan, and P. Nuggenhalli, “Peoplenet: Engi￾neering a wireless virtual social network,” in Proc. ACM MobiCom, 2005, pp. 243–257. [7] A. J. Campbell, S. B. Eisenman, N. D. Lane, E. Miluzzo, and R. A. Peterson, “People-centric urban sensing,” in Proc. WICON, 2006, vol. 220, Article No. 18. [8] H. Y. O. Wolfson, B. Xu, and H. Cao, “Search-and-discover in mobile p2p network databases,” in Proc. IEEE ICDCS, 2006, pp. 65–73. [9] M. Kuhn and R. Wattenhofer, “Community aware mobile networking,” in Proc. 1st Workshop on Mobile Services and Personalized Environ., 2006, pp. 1–14. [10] V. Srinivasan, M. Motani, and W. T. Ooi, “Analysis and implications of student contact patterns derived from campus schedules,” in Proc. ACM MobiCom, 2006, pp. 86–97. [11] A. Natarajan, M. Motani, and V. Srinivasan, “Understanding urban in￾teractions from Bbluetooth phone contact traces,” in Proc. PAM, 2007, pp. 115–124. [12] J. Su, A. Chin, A. Popivanova, and E. d. L. A. Goel, “User mobility for opportunistic ad-hoc networking,” in Proc. IEEE WMCSA, 2004, pp. 41–50. [13] N. Eagle and A. Pentland, “Social serendipity: Mobilizing social soft￾ware,” IEEE Pervasive Comput., vol. 4, no. 2, pp. 28–34, 2005. [14] A. Chaintreau, P. Hui, J. Crowcroft, C. Diot, R. Gass, and J. Scott, “Pocket switched networks: Real world mobility and its consequences for opportunistic forwarding,” Univ. Cambridge, Cambridge, U.K., 2005, Tech. Rep. No. 617. [15] S. M. Ross, Stochastic Processes. New York: Wiley, 1983. [16] S. Boyd and L. Vandenberghe, Convex Optimization. Cambridge, U.K.: Cambridge Univ. Press, 2005. [17] G. He and J. Hou, “An in-depth, analytical study of sampling tech￾niques for self-similar internet traffic,” in Proc. IEEE ICDCS, 2005, pp. 404–413. [18] W. Leland, M. Taqqu, W. Willinger, and D. Wilson, “On the self-sim￾ilar nature of ethernet traffic,” IEEE/ACM Trans. Netw., vol. 2, no. 1, pp. 1–15, Feb. 1994. [19] J. Beran, Statistics for Long-Memory Processes. London, U.K.: Chapman & Hall, 1994. [20] M. McNett and G. M. Voelker, “Access and mobility of wireless PDA users,” Mobile Comput. Commun. Rev., vol. 9, no. 2, pp. 40–55, 2005. [21] A. Papoulis and S. U. Pillai, Probability, Random Variables and Sto￾chastic Processes, 4th ed. New York: McGraw Hill, 2002. [22] R. Shah, S. Roy, S. Jain, and W. Brunette, “Data mules: Modeling a three-tier architecture for sparse sensor networks,” in Proc. IEEE SNPA, 2003, pp. 30–41. [23] P. Hui, A. Chaintreau, J. Scott, R. Gass, J. Crowcroft, and C. Diot, “Pocket switched networks and human mobility in conference environ￾ments,” in Proc. ACM SIGCOMM Workshop on Delay-Tolerant Netw., 2005, pp. 244–251. [24] T. Gross and C. Tuduce, “A mobility model based on WLAN traces and its validation,” in Proc. IEEE INFOCOM, 2005, pp. 664–674. [25] W.-J. Hsu, T. Spyropoulos, K. Psounis, and A. Helmy, “Modeling time-variant user mobility in wireless mobile networks,” in Proc. IEEE INFOCOM, 2007, pp. 758–766. [26] L.-J. Chen, Y.-C. Chen, T. Sen, P. Sreedevi, K.-T. Chen, C.-H. Yu, and H.-H. Chu, “Finding self-similarities in opportunistic people net￾works,” in Proc. IEEE INFOCOM, 2007, pp. 2286–2290. [27] C. Drula, “Fast and energy efficient neighbour discovery for oppor￾tunistic networking with Bluetooth,” Master’s thesis, Univ. of Toronto, Toronto, ON, Canada, 2005. [28] G. Zaruba and I. Chlamtac, “Accelerating Bluetooth inquiry for per￾sonal area networks,” in Proc. IEEE GLOBECOM, 2003, pp. 702–706. [29] N. Bisnik, A. Abouzeid, and V. Isler, “Stochastic event capture using mobile sensors subject to a quality metric,” in Proc. ACM MobiCom, 2006, pp. 98–109. [30] P. Barford and M. Crovella, “Generating representative web workloads for network and server performance evaluation,” in Proc. ACM Sigmet￾rics/Performance, 1998, pp. 151–160. [31] J. Polastre, J. Hill, and D. Culler, “Versatile low power media access for wireless sensor networks,” in Proc. ACM SenSys, 2004, pp. 95–107. Wei Wang (S’06–M’09) received the Ph.D. degree in electrical and computer engineering from the Na￾tional University of Singapore in 2008. He is currently with Microsoft Research Asia, Bei￾jing, China. His research interests are in the area of wireless networking. Mehul Motani (S’92–M’00) received the B.E. de￾gree from Cooper Union, New York, the M.S. de￾gree from Syracuse University, Syracuse, NY, and the Ph.D. degree from Cornell University, Ithaca, NY, all in electrical and computer engineering. He is currently an Assistant Professor in the Elec￾trical and Computer Engineering Department at the National University of Singapore. Previously, he was a Research Scientist at the Institute for Infocomm Re￾search in Singapore for three years and a Systems En￾gineer at Lockheed Martin in Syracuse, NY, for over four years. Recently, he has been working on research problems that sit at the boundary of information theory, communications, and networking, including the design and analysis of wireless ad hoc and sensor network systems. Dr. Motani was awarded the Intel Foundation Fellowship for work related to his Ph.D. in 2000. He has served on the organizing and technical program com￾mittees of ISIT, MobiCom, INFOCOM, SECON, and various other conferences. He participates actively in the IEEE and Association for Computing Machinery and has served as the Secretary of the IEEE Information Theory Society Board of Governors. Vikram Srinivasan (M’03) received the Bachelor of Science degree in physics from the University of Chennai, Chennai, India, in 1994; the M.E. degree in electrical communications engineering from the In￾dian Institute of Science, Bangalore, India, in 1998; and the Ph.D. degree in electrical and computer engineering from the University of California at San Diego in 2003. He was an Assistant Professor in the Electrical and Computer Engineering Department, National University of Singapore, from 2003 to 2007. He is currently with Bell Labs Research, Bangalore, India. His research interests are broadly in the area of wireless networks