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Evaluation of the Masked Node Problem in Ad Hoc Wireless LANs
September/October 2005 (vol. 4 no. 5)
pp. 430-442
IEEE 802.11 wireless networks employ the so-called RTS/CTS mechanism in order to avoid DATA packet collisions. The main design assumption is that all the nodes in the vicinity of a sender and a receiver will hear the RTS or CTS packets, and defer their transmission appropriately. This assumption happens to not hold, in general, even under perfect operating conditions. Often, neighboring nodes are "masked” by other ongoing transmissions nearby and, hence, are unable to receive the RTS or CTS packets correctly. We refer to such nodes as masked nodes. In this paper, we describe the masked node problem and show scenarios leading to DATA packet collisions. We evaluate the impact of masked nodes through mathematical analysis and real experiments on a small IEEE 802.11 ad hoc network. The analytical and experimental data closely match and reveal that the presence of a masked node in a network can result in an order of magnitude increase in DATA packet loss compared to a network without masked nodes. These results are further validated by extensive simulations on a large-scale network, which show that masked nodes also significantly affect delay and throughput performance. Therefore, masked nodes severely limit the effectiveness of the RTS/CTS mechanism in preventing performance degradation in wireless LANs.

[1] Z.J. Haas, J. Deng, B. Liang, P. Papadimitratos, and S. Sajama, “Wireless Ad Hoc Networks,” Encyclopedia of Telecomm., J.G. Proakis, ed., Wiley, 2002.
[2] “ANSI/IEEE Std 802.11-1999 Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.” 1999.
[3] R. Rom and M. Sidi, Multiple Access Protocols: Performance and Analysis. Springer Verlag, 1990.
[4] L. Kleinrock and F.A. Tobagi, “Packet Switching in Radio Channels: Part 1— Carrier Sense Multiple-Access Modes and Their Throughput-Delay Characteristics,” IEEE Trans. Comm., vol. 23, no. 12, pp. 1400-1416, 1975.
[5] F. Tobagi and L. Kleinrock, “Packet Switching in Radio Channels: Part 2— The Hidden Node Problem in Carrier Sense Multiple Access Modes and the Busy Tone Solution,” IEEE Trans. Comm., vol. 23, no. 12, pp. 1417-1433, 1975.
[6] P. Karn, “MACA— A New Channel Access Method for Packet Radio,” Proc. ARRL/CRRL Amature Radio Ninth Computer Networking Conf., pp. 134-140, Sept. 1990.
[7] V. Bharghavan, A. Demers, S. Shenker, and L. Zhang, “MACAW: A Media Access Protocol for Wireless LANs,” Proc. ACM SIGCOMM Conf., pp. 212-225, 1994.
[8] S. Ray, J.B. Carruthers, and D. Starobinski, “RTS/CTS-Induced Congestion in Ad-Hoc Wireless LANs,” Proc. IEEE Wireless Comm. and Networking Conf. (WCNC), pp. 1516-1521, Mar. 2003.
[9] K. Xu, M. Gerla, and S. Bae, “How Effective is the IEEE 802.11 RTS/CTS Handshake in Ad Hoc Networks?,” Proc. IEEE Globecom Conf., 2002.
[10] E. Jung and N.H. Vaidya, “A Power Control MAC Protocol for Ad Hoc Networks,” Proc. ACM Int'l Conf. Mobile Computing and Networking (MobiCom), Sept. 2002.
[11] C.L. Fullmer and J.J. Garcia-Luna-Aceves, “Floor Acquisition Multiple Access (FAMA) for Packet-Radio Networks,” Proc. SIGCOMM Conf., 1995.
[12] S.-L. Wu, Y.-C. Tseng, and J.-P. Sheu, “Intelligent Medium Access for Mobile Ad Hoc Networks with Busy Tones and Power Control,” IEEE J. Selected Areas in Comm., vol. 18, no. 9, pp. 1647-1657, Sept. 2000.
[13] Z.J. Haas, “On the Performance of a Medium Access Control Scheme for the Reconfigurable Wireless Networks,” Proc. MILCOM Conf., 1997.
[14] D. Gross and C.M. Harris, Queuing Theory, third ed. John Wiley & Sons, 1998.
[15] J. Murdock, Perturbations: Theory and Methods. Wiley, 1991.
[16] Aironet Wireless Comm., PC4500/PC4800 Developer's Reference Manual, document number: 710-004247, Revision: B1, 1997.
[17] “SimEleven: An IEEE 802.11 MATLAB-Based Simulator,”, 2004.
[18] J.P. Monks, V. Bharghavan, and W.W. Hwu, “A Power Controlled Multiple Access Protocol for Wireless Packet Networks,” Proc. IEEE Infocom Conf., pp. 134-140, Mar. 2001.
[19] S. Verdu, Multiuser Detection. The Press Syndicate of the Univ. of Cambridge, 1998.

Index Terms:
Index Terms- Wireless communication, experimental design, performance evaluation, queuing theory, simulation.
Saikat Ray, Jeffrey B. Carruthers, David Starobinski, "Evaluation of the Masked Node Problem in Ad Hoc Wireless LANs," IEEE Transactions on Mobile Computing, vol. 4, no. 5, pp. 430-442, Sept.-Oct. 2005, doi:10.1109/TMC.2005.66
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