Ahmed Helmy
Associate Professor
Computer & Information Science & Engineering (CISE) Department
College of Engineering, University of Florida
Founder and Director: Mobile Networking Laboratory (NOMADS group)
(Courtesy appointements: ECE Dept, UF and EE - Systems Dept, USC)
email: helmy at ufl.edu

Following are selected publications: On Mobile and Sensor Networks - Other Selected Publications - Recent Selected Work
For a more complete list of publications select Publications by year.

Selected Publications (On Mobile and Sensor Networks)

1. W. Hsu, T. Spyropoulos, K. Psounis, A. Helmy, TVC: "Modeling Spatial and Temporal Dependencies of User Mobility in Wireless Mobile Networks", IEEE/ACM Transactions on Networking, pp. 1564-1577, Vol. 17, No. 5, October 2009.
   (Conference version appeared in IEEE INFOCOM, pp.758-766, May 2007 [Acceptance rate: ~17%]).
2. W. Hsu, D. Dutta, A. Helmy, "CSI: A Paradigm for Behavior-oriented Profile-cast Services in Mobile Networks", IEEE/ACM Transactions on Networking, accepted with revision.
   (Earlier short version in ACM Mobile Computer and Communications Review (MC2R), Vol. 12, Issue 1, pp. 52-54, January 2008. [Top 5 in ACM Mobicom SRC]. Conference version appeared in IEEE WCNC (Wireless Communications and Networking Conference), pp. 3033-3038, March 2008).
3. S. Tanachaiwiwat, A. Helmy, "Encounter-based Worms: Analysis and Defense", Ad Hoc Networks Journal - Elsevier. Volume 7, Issue 7, Pages 1414-1430, September 2009.
   (Conference version appeared in ACM MobiCom Workshop on Challenged Networks (CHANTS), pp. 67-74, September 2007).
4. Y. Kim, A. Helmy, "CATCH: A Protocol Framework for Cross-layer Attacker Traceback in Mobile Multi-Hop Networks", Ad Hoc Networks Journal - Elsevier, pp. 193-213, Vol. 8, Issue 2, March 2010.
   (Conference version in Proceedings of the ACM SASN (fourth ACM workshop on Security of ad hoc and sensor networks), pp. 123-134, October 2006.)
5. M. Zuniga, K. Seada, B. Krishnamachari, A. Helmy, "Efficient Geographic Routing over Lossy Links in Wireless Sensor Networks", ACM Transactions on Sensor Networks (TOSN), pp. 12:1-33, Article 12 (33 pages), Vol. 4, No. 3, May 2008. (Conference version appeared in ACM SenSys (Conference on Embedded Networked Sensor Systems), pp. 108-121, November 2004. [Acceptance: 14%] [Nominated for best paper award at USC EE Dept, 2005]). (Related work on geographic routing with power control appeared in IEEE SECON, Sep 2005 [Acceptance: 27%]).
6. K. Seada, A. Helmy, R. Govindan, "Modeling and Analyzing the Correctness of Geographic Face Routing under Realistic Conditions", Ad Hoc Networks Journal - Elsevier, Special issue on Recent Advances in Wireless Sensor Networks, pp. 855-871, Vol. 5, Issue 6, August 2007. (Conference version appeared in IEEE/ACM IPSN (Int'l Symposium on Information Processing in Sensor Networks), pp. 71-80, April 2004. [Acceptance rate: 33% of 150] [Nominated for best paper award at USC EE Dept, 2004]).
7. K. Nahm, A. Helmy, C.-C. Kuo, "Cross-layer Interaction of TCP and Ad Hoc Routing Protocols in Multihop 802.11 Networks", IEEE Transactions on Mobile Computing (TMC), pp. 458 - 469, Vol. 7, Issue 4, April 2008. (Conference version appeared in ACM MobiHoc (Int'l Symposium on Mobile Ad Hoc Networking and Computing), pp. 277-287, May 2005. [Acceptance rate: 14% of 281 submissions]).
8. K. Seada, A. Helmy, R2D2: "Geographic Rendezvous-based Architectures for Emergency Data Dissemination", Journal on Wireless Communications and Mobile Computing, Wiley. Accepted, in press (Dec 08) (Early version). (Conference version appeared in IEEE/ACM IPDPS Int'l Workshop on Algorithms for Wireless, Mobile, Ad Hoc and Sensor Networks (WMAN), pp.218-225, Apr 2004).
9. F. Bai, A. Helmy, MAID: "Impact of Mobility on Mobility-Assisted Last Encounter Based Routing Protocols", IEEE SECON (Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks), pp. 461-470, June 2007. [Acceptance: 20%]. (Journal version in submission).
10. K. Seada, A. Helmy, "Efficient and Robust Geocasting Protocols for Sensor Networks", Computer Communications Journal-Elsevier, Special Issue on Dependable Wireless Sensor Networks, Vol. 29, Issue 2, pp. 151-161, January 2006 (Conference version appeared IEEE WCNC, pp. 2551 - 2556, March 2004).
11. IMPACT study:
    • - W. Hsu, A. Helmy, "On Nodal Encounter Patterns in Wireless LAN Traces", IEEE Int'l Workshop on Wireless Network Measurement (WiNMee), April 2006 [Nominated for best paper award at USC EE Dept, 2006]. (Journal version in submission)
    • - W. Hsu, A. Helmy, "On Modeling User Associations in Wireless LAN Traces on University Campuses", IEEE Int'l Workshop on Wireless Network Measurement (WiNMee), April 2006.
12. A. Helmy, S. Garg, P. Pamu, N. Nahata, "CARD: A Contact-based Architecture for Resource Discovery in Ad Hoc Networks", ACM Mobile Networks and Applications (MONET) Journal, Vol. 10, Issue 1, pp. 99-113, February 2005. [Acceptance rate: 22% of 60 submissions] (Conference version appeared in IEEE/ACM IPDPS Int'l Workshop on Wireless, Mobile and Ad Hoc Networks (WMAN), pp. 219-227, Apr 2003. [Acceptance: 29%] [Paper selected for forwarding to the ACM MONET Journal for review and publication]).
13. N. Sadagopan, B. Krishnamachari, A. Helmy, ACQUIRE: "Active Query Forwarding in Sensor Networks", Ad Hoc Networks Journal - Elsevier, Vol. 3, Issue 1, pp. 91-113, January 2005. [Acceptance rate: 12%] (Conference version" appeared in IEEE ICC Int'l Workshop on Sensor Network Protocols and Applications (SNPA), pp. 149-155, May 2003. [Acceptance: 37%]).
14. A. Helmy, TRANSFER: "Contact-extended Zone-based Routing for Transactions in Ad Hoc Networks", IEEE Transactions on Vehicular Technology, Vol. 54, No. 1, pp. 307-319, January 2005. (Conference version appeared in IEEE GLOBECOM (Global Telecom. Conf), pp. 398-404, December 2003. [Acceptance: 27%]).
15. F. Bai, N. Sadagopan, B. Krishnamachari, A. Helmy, PATHS: "Modeling Path Duration Distributions in MANETs and their Impact on Routing Performance", IEEE Journal on Selected Areas in Communications (JSAC), Vol. 22, No. 7, pp. 1357-1373, September 2004. [Acceptance rate: 18% of 82] [Nominated for best paper award at USC EE Dept, 2005]. (Conference version appeared in ACM MobiHoc, pp. 245-256, June 2003. [Acceptance rate: 15% of 189 submissions]).
16. D. Son, A. Helmy, B. Krishnamachari, "The Effect of Mobility-induced Location Errors on Geographic Routing in Mobile Ad Hoc and Sensor Networks: Analysis and Improvement using Mobility Prediction", IEEE Transactions on Mobile Computing (TMC), Special issue on Mission-Oriented Sensor Networks, Vol. 3, No. 3, pp. 233-245, July 2004 [Acceptance rate: 25%] (Conference version appeared in IEEE WCNC, pp. 189-194 March 2004).
17. F. Bai, N. Sadagopan, A. Helmy, "The IMPORTANT Framework for Analyzing the Impact of Mobility on Performance of Routing for Ad Hoc Networks", Ad Hoc Networks Journal - Elsevier, Vol. 1, Issue 4, pp. 383 - 403, November 2003. [Acceptance rate: 12%][Nominated for best paper award at USC EE Dept, 2004]. On the top 25 most requested articles (Ad Hoc Networks Journal) for Jan-Dec'03 & Jan-Mar'04. (Conference version appeared in IEEE INFOCOM, pp. 825-835, April 2003. [Acceptance rate: 20% of 1078 submissions])
18. A. Helmy, "Mobility-Assisted Resolution of Queries in Large-Scale Mobile Sensor Networks (MARQ)", Computer Networks Journal - Elsevier, Special issue on Wireless Sensor Networks, Vol. 43, Issue 4, pp. 437-458, November 2003. [Acceptance rate: 24% of 25 submissions].
19. A. Helmy, "Small Worlds in Wireless Networks", IEEE Communications Letters, pp. 490-492, Vol. 7, No. 10, October 2003.
20. A. Helmy, M. Jaseemuddin, Ganesha Bhaskara, M&M: "Multicast-based Mobility: A Novel Architecture for Efficient Micro-Mobility", IEEE Journal on Selected Areas in Communications (JSAC), Vol. 22, No. 4, pp. 677-690, May 2004. [Acceptance rate: 25% of 60 submissions] (Earlier work on M&M appeared in ACM SIGCOMM Int'l Workshop on Networked Group Communication (NGC), pp. 49-58, November 2000. [Acceptance: 24%]).

Other Selected Publications

1. S. Ebrahimi, A. Helmy, S. Gupta, "TCP vs. TCP: a Systematic Study of Adverse Impact of Short-lived TCP Flows on Long-lived TCP Flows", IEEE INFOCOM, pp. 926-937, March 2005. [Acceptance rate: 17% of 1419 submissions] [Nominated for best paper award at USC EE, 2005].
2. A. Das, D. Dutta, A. Helmy, A. Goel, J. Heidemann, "Low State Fairness: Lower Bounds and Practical Enforcement", IEEE INFOCOM, pp. 2436-2446, March 2005 [Acceptance rate: 17%]. (The framework design appeared in IEEE Communications Letters, Vol. 8, No. 9, pp. 588-590, Sept 2004.) (Earlier work on Fair Stateless Aggregate Marking with A. Das and D. Dutta appeared in IEEE/IFIP MMNS (Management of Multimedia Networks and Services, pp. 211-223, October 2002. (Best Paper Award)).
3. A. Helmy, S. Gupta, "FOTG: Fault Oriented Stress Testing of Multicast Routing", IEEE Communications Letters, Vol. 9, No. 4, pp. 375-377, April 2005. (Conference version appeared in IFIP FORTE/PSTV, Paris, pp. 93-109, November 1998. [Acceptance rate: 30% of 85], and another conference version" comparing forward and backward search appeared IEEE ICCCN (IC3N), pp. 590-597, October 2000.)
4. K. Seada, A. Helmy, S. Gupta, "A Framework for Systematic Evaluation of Multicast Congestion Control Protocols", IEEE Journal on Selected Areas in Communications (JSAC), Volume 22, Issue 10, pp. 2048- 2061, December 2004. [Nominated for best paper award at USC EE, 2005].
5. A. Helmy, S. Gupta, D. Estrin, "The STRESS Method for Boundary-point Performance Analysis of End-to-end Multicast Timer-Suppression Mechanisms", IEEE/ACM Transactions on Networking, Volume 12, Issue 1, pp. 44-58, February 2004. [Acceptance rate '03: 18% of 439] (Conference version appeared in IFIP FORTE/PSTV (Formal Description Techniques & Protocol Specification, Testing, and Verification, pp. 187-202, October 2000. [Acceptance: 34% of 63]).
6. L. Breslau, D. Estrin, K. Fall, S. Floyd, J. Heidemann, A. Helmy, P. Huang, S. McCanne, K. Varadhan, Y. Xu, H. Yu, NS-2: "Advances in Network Simulation", IEEE Computer, vol.33, No.5, pp. 59-67, May 2000. [Top 65 most cited papers in computer science in 2000 (Citeseer Jul '03)]
7. PIM-SM protocol:
   • - D. Estrin, M. Handley, A. Helmy, P. Huang, D. Thaler, "A Dynamic Bootstrap Mechanism for Rendezvous-based Multicast Routing", IEEE INFOCOM, Vol. 3, pp. 1090-1098, March 1999. [Acceptance rate: 30% of 600 submissions].
   • - D. Estrin, D. Farinacci, A. Helmy, D. Thaler, S. Deering, V. Jacobson, M. Handley, C. Liu, P. Sharma, L. Wei, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification", RFCs 2362 of the Internet Engineering Task Force (IETF), Inter-Domain Multicast Routing (IDMR), June 1998. [RFC2362. Earlier version as RFC2117 in 1997]
   • - D. Estrin, D. Farinacci, A. Helmy, D. Thaler, S. Deering, V. Jacobson, M. Handley, C. Liu, P. Sharma, L. Wei, "Protocol Independent Multicast (PIM): Motivation and Architecture", Proposed RFC of the IETF, Inter-Domain Multicast Routing (IDMR), October 1996.

Selected Recent Publications (Work in progress)

1. W. Hsu, D. Dutta, A. Helmy, "Mining Behavioral Groups in Large Wireless LANs", ACM MobiCom, pp. 338-341 (short paper), Sept. 2007. [In the top 11% of 233 submissions.] (Journal version in submission). [Extended version as technical report].
2. U. Kumar, N. Yadav, A. Helmy, "Gender-based Feature Analysis in Campus-wide WLANs", ACM MC2R, Vol. 12, Issue 1, pp. 40-42, January 2008. [Top 10% & Winner of 3rd place prize in ACM Mobicom SRC]. (Workshop version presented at IEEE/ACM IPSN Int'l Workshop on Mobile Device and Urban Sensing (MODUS), April 2008). (newer version in submission)
3. S. Wang, A. Helmy, "BEWARE: Background Traffic-Aware Rate Adaptation for IEEE 802.11", Extended (plenary session) paper at The 9th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM), June 2008 [Acceptance rate of Extended papers at the plenary session: 7% of 181 submissions] (Journal version to be submitted).