In this section, the performance of proposed schemes will be compared with existing protocols including the conventional IEEE 802.11a DCF protocol, the eMAC algorithm [29], and the eDCF protocol [32]. The proposed proto-cols include the ART, MRT+FNT, and FNT schemes where the MRT+FNT approach denotes the combination of the MRT and FNT algorithms as de-scribed in Chapter 4. In order to provide consistent network scenario and simulation settings with the proposed schemes, each node in the eMAC proto-col is selected to have the same coverage R for the transmission, sensing, and interference ranges. Therefore, the ICP frame of Type II and the out-of-band busy tone in the eMAC scheme can be ignored in the following simulations.
Moreover, the overhead of eMAC-table and the data sent (DS) control frame in the eMAC protocol is assumed to be extremely small such that the best case of the eMAC scheme is evaluated in the simulations.
Fig. 6.6 shows the performance comparison between the proposed pro-tocols and the existing schemes. In the left plot, the average throughput is compared under different number of nodes N with payload size L = 3000 bytes; while the throughput performance is compared under different payload sizes with N = 60 in the right plot. Note that the proposed ART protocol is evaluated under three cases as M = 2, 4, and with dynamic adjustment algorithm for Mi which is denoted as ART-DA scheme. As the total num-ber of nodes in the network grows, it is intuitively to observe from the left plot that the throughput performance of all the schemes becomes worse since there can exist more packet collisions and additional interference from hidden nodes. The proposed ART-DA protocol can provide the highest throughput performance compared to the other schemes owing to its dynamic adjustment of selected receivers Mi. The throughput performance of eDCF protocol is similar to that of the MRT+FNT scheme since the eDCF protocol provides
a second chance to deliver the data packet to another receiver if there is no CTS feedback from the original destination. Furthermore, as the payload size becomes larger shown in the right plot, the throughput performance is increased in all the schemes since the source node is able to delivery addi-tional information bytes after winning the channel contention. The proposed ART-DA protocol still outperform the other methods with the highest sys-tem throughput owing to its better channel utilization instead of constructing unnecessary connection attempts between the network nodes. Consequently, the simulation results show that the proposed ART protocols, especially the ART-DA scheme, can consistently outperform the other algorithms and ef-fectively alleviate the receiver blocking problem.
Fig. 6.7 illustrates the comparison of control overhead versus number of nodes under L = 3000 bytes. Note that the control overhead is defined as the number of RTS/M-RTS packets over the number of CTS packets which implies the average required RTS/M-RTS packets for a protocol to acquire a CTS feedback from the selected receivers. In other words, as the control overhead is increased, the protocol will operates in a less efficient manner with worse channel utilization since it wastes excessive time in establishing the connection to obtain a CTS packet. As in Fig. 6.7, if the number of nodes is increased, additional control overhead for all the scheme can be observed which is attributed to the excessive packet collisions and retransmissions within the network. The conventional IEEE 802.11a DCF protocol results in the highest control overhead among all the schemes owing to its poor ability to handle the receiver blocking problem in the ad-hoc networks. Even though the throughput performance of the eDCF protocol is similar to that of the MRT+FNT scheme, excessive RTS packets are required by the eDCF protocol which is attributed to the second chance for delivering the data packet to another receiver that is not confirmed by the second receiver’s
CTS packet. It can be observed that the proposed ART-DA scheme can achieve reasonable lowered control overhead compared to other protocols.
With less number of network node, the behaviors of the ART-DA protocol will be similar to the cases with smaller M values, e.g. M = 2; while the ART-DA scheme will behave similar to the situation with larger M under increased value of N. Therefore, as can be seen from Fig. 6.7, the total number of M-RTS packets of the ART-DA protocol will intersect the curves from smaller to larger M values as the number of nodes is augmented.
Fig. 6.8 shows the performance comparison from different boundary lim-its B to the system throughput. As the boundary limit is less than 30 meters, the multi-hop ad-hoc network will be degenerated to be a single hop ad-hoc network. The hidden terminal problem becomes minimal where the trans-mission failure is primarily caused by the RTS/M-RTS packet collision at a given time slot. Note that the collision probability will merely be related to the total number of nodes N as was derived in [43]. As shown in Fig. 6.8, when the boundary limit is less than 30 meters, the throughput performance will be the same for all the schemes except for the proposed ART-DA algo-rithm owing to the reason that the ART-DA scheme is primarily designed to alleviate the receiver blocking problem in multi-hop ad-hoc networks. The ART-DA protocol will result in unnecessarily excessive number of selected receivers Mi with the occurrence of failed transmission of M-RTS packets such as to deteriorate the throughput performance. Therefore, compared to the other algorithms, it can be observed that the conventional IEEE 802.11a DCF protocol can provide feasible throughput performance in the single hop ad-hoc networks. As the boundary limit B is increased, the effect of hid-den nodes becomes significant to influence the on-going transmissions in the multi-hop networks. The effectiveness of the proposed ART-DA scheme is revealed such as to provide the highest throughput performance compared
to the other algorithms. Noted that the throughput performance for all the schemes is increased alone with the boundary limit since the neighbor size per node is decreased which can provide higher chance for different transmission pairs to conduct data delivery in the network.
Furthermore, it is worthwhile to evaluate the performance of proposed protocols with mobility of network nodes. The random way-point mobility (RWM) model is adopted to simulate the movement of all the nodes in the multi-hop ad-hoc network. In the RWM model, a mobile node begins by staying at a position for a random period of time called the pause time, which is determined based on a uniform distribution between [1, tp] in the unit of µs where tp denotes the maximum pause time. After the pause time has expired, the node starts to move towards the next position which is located in the simulation area and the moving velocity is uniformly selected from [1, Vm], where Vm indicates the maximum velocity of mobile node. Fig. 6.9 illustrates the throughput performance versus different maximum velocities in the left plot; while the throughput performance versus pause time is shown in the right plot. The proposed ART-DA protocol is compared to both the eMAC and the IEEE 802.11a DCF protocols. Note that the total number of node is selected as N = 60, the information payload size is L = 3000 bytes, and the boundary limit B = 180 meters as shown in Table 2.
It can be observed from Fig. 6.9(a) that the throughput decreases sharply after the network nodes are moving since it becomes difficult for each source node to acquire its corresponding receiver for data transmission. Afterwards, the throughput will be maintained at the same level as the maximum velocity of mobile node has been enlarged. The major reason is that most of the network connections can still be maintained in one transmission time since the velocity of each node is not large enough such that the nodes in each transmission pair will not escape from each other in such short time period.
It is intuitive to observe in each scheme that smaller pause time, i.e. tp = 5 milliseconds, will result in reduced system throughput compared to that with tp = 2 seconds. On the other hand, similar performance can be seen from Fig. 6.9(b) under reasonable pause time for all three schemes. The major difference is that the system throughput will be enlarged as the pause time is increased from 1 to 100 seconds, which implies that the mobile nodes will behave more stationary in the network topology. It can be observed from both plots that the proposed ART-DA protocol can outperform the other two existing schemes under various circumstances. The benefits of adopting the proposed ART protocols can therefore be observed.
20 40 60 80 100 120 140 160 180 200
0 500 1000 1500 2000 2500 3000 3500 4000
0
Figure 6.1: Performance validation for ART protocol with M = 2: average throughput versus number of nodes (top plot) and payload size (bottom plot).
20 40 60 80 100 120 140 160 180 200
0 500 1000 1500 2000 2500 3000 3500 4000
0
Figure 6.2: Performance validation for ART protocol with M = 4: average throughput versus number of nodes (top plot) and payload size (bottom plot).
20 40 60 80 100 120 140 160 180 200
0 500 1000 1500 2000 2500 3000 3500 4000
0
Figure 6.3: Performance validation for IEEE 802.11a DCF protocol: average throughput versus number of nodes (top plot) and payload size (bottom plot).
2 3 4 5 6 7 8 9 10 11
Figure 6.4: Sensitivity analysis: average system throughput versus decreasing threshold T hd.
Average Number of Selected Receivers
L = 500 L = 1000 L = 2000 L = 4000
Figure 6.5: Average number of selected receivers Mi versus number of total nodes N.
20 40 60 80 100 120 140 160 180 200
0 500 1000 1500 2000 2500 3000 3500 4000
0.5
Figure 6.6: Performance comparison: average throughput versus number of nodes (top plot) and payload size (bottom plot).
20 40 60 80 100 120 140 160 180 200
Figure 6.7: Performance comparison: control overhead versus number of nodes.
Figure 6.8: Performance comparison: average throughput versus boundary limit B.
0 5 10 15 20 25 30
0.01 0.1 1 10 100 1,000 10,000 100,000
1.5
Figure 6.9: Performance comparison: average throughput versus maximum velocity (m/s) (top plot) and maximum pause time (ms) (bottom plot).
Chapter 7 Conclusion
In this thesis, both the multiple receiver transmission (MRT) and the fast NAV truncation (FNT) mechanisms are proposed in order to alleviate the receiver blocking problem in the multi-hop ad-hoc networks. The adap-tive receiver transmission (ART) scheme is proposed to further improve the throughput performance with dynamic adjustment on the number of selected receivers. Analytical model is derived for the proposed ART scheme and is validated via simulations. It is shown in the simulation results that the pro-posed ART scheme can effectively alleviate the receiver blocking problem, which consequently enhances the network throughput for wireless multi-hop ad-hoc networks.
Bibliography
[1] C.S. Murthy and B.S. Mano, Ad Hoc Wireless Networks: Architectures and Protocols.
Prentice Hall, 2004.
[2] F.A. Tobagi and L. Kleinrock, “Packet switching in radio channels:Part II-the hidden terminal problem in carrier sense multiple-access modes and the busy-tone solution,”
IEEE Trans. Commun., vol. COM-23, no. 12, pp. 1417–1433, 1975.
[3] P. Karn, “MACA - A new channel access method for packet radio,” in Proc.
ARRL/CRRL Amateur Radio 9th Computer Networking Conf., Sep. 1990, pp. 134–
140.
[4] V. Bharghavan, A. Demers, S. Shenker, and L. Zhang, “MACAW: A media access protocol for wireless LAN’s,” in Proc. ACM SIGCOMM’94, Oct. 1994, pp. 212–225.
[5] C.L. Fullmer and J.J. Garcia-Luna-Aceves, “Floor Acquisition Multiple Access (FAMA) for Packet-Radio Networks,” in Proc. ACM SIGCOMM’95, Oct. 1995, pp.
262–273.
[6] ——, “Solutions to hidden terminal problems in wireless networks,” in Proc. ACM SIGCOMM’97, Oct. 1997, pp. 39–49.
[7] IEEE 802.11 WG, IEEE Std 802.11a-1999 (R2003): Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHz Band, IEEE Standards Association Std., 2003.
[8] IEEE 802.11 WG, IEEE Std 802.11b-1999 (R2003): Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Higher-Speed Phys-ical Layer Extension in the 2.4 GHz Band, IEEE Standards Association Std., 2003.
[9] IEEE 802.11 WG, IEEE Std 802.11g-2003: Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Amendment 4: Further Higher Data Rate Extension in the 2.4 GHz Band, IEEE Standards Association Std., 2003.
[10] IEEE 802.11 WG, IEEE P802.11n/D3.00: Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Amendment 4: Enhance-ments for Higher Throughput, IEEE Standards Association Std., Sept. 2007.
[11] S. Xu and T. Saadawi, “Does the IEEE 802.11 MAC protocol work well in multihop wireless ad hoc networks?” IEEE Commun. Mag., vol. 39, no. 6, pp. 130–137, Jun.
2001.
[12] K. Xu, M. Gerla, and S. Bae, “How Effective is the IEEE 802.11 RTS/CTS Handshake in AdHoc Networks?” in Proc. IEEE GIOBECOM, Nov. 2002, pp. 17–21.
[13] A. Swaminathan, D.L. Noneaker, and H.B. Russell, “The Receiver Blocking Prob-lem in a DS Mobile Ad Hoc Network with Directional Antennas,” in Proc. IEEE MILCOM, Oct. 2004, pp. 920–926.
[14] H. Zhai, J. Wang, Y. Fang, and D. Wu, “A dual-channel MAC protocol for mobile ad hoc networks,” in Proc. IEEE GLOBECOM Workshops, Nov. 2004, pp. 27–32.
[15] H. Zhai, J. Wang, and Y. Fang, “DUCHA: A New Dual-Channel MAC Protocol for Multihop Ad Hoc Networks,” IEEE Trans. Wireless Commun., vol. 5, no. 11, pp.
3224–3233, Nov. 2006.
[16] B. Zhou, A. Marshall, and T.H. Lee, “The Non-Responsive Receiver Problem in Mobile Ad-Hoc Networks,” IEEE Commun. Lett., vol. 9, no. 11, pp. 973–975, Nov.
2005.
[17] S.R Ye, Y.C. Wang, and Y.C. Tseng, “A jamming-based MAC protocol for wireless multihop ad hoc networks,” in Proc. IEEE VTC-Fall, Oct. 2003, pp. 1396–1400.
[18] Y. Gu, L. Shen, and X. Qiu, “A dual-channel MAC protocol for multi-hop ad hoc networks,” in Proc. IEEE ICCCAS, May 2005, pp. 308–313.
[19] K. Ghaboosi, M. Latva-aho, and Y. Xiao, “Receiver blocking problem in mobile ad hoc networks: Challenges & solutions,” in Proc. IEEE WD’08, Nov. 2008, pp. 1–5.
[20] K. Ghaboosi, M. Latva-aho, Y. Xiao, and Q. Zhang, “Unreachability problem in mo-bile ad hoc networks: A medium access control perspective,” in Proc. IEEE PIMRC, Sept. 2009, pp. 2576–2580.
[21] D. Tse and P. Viswanath, Fundamentals of Wireless Communication. Cambridge University Press, 2005.
[22] J. Deng and Z.J. Haas, “Dual busy tone multiple access (DBTMA): a new medium access control scheme for packet radio networks,” in Proc. IEEE ICUPC’98, Oct.
1998, pp. 973–977.
[23] Z.J. Haas and J. Deng, “Dual busy tone multiple access (DBTMA)- performance evaluation,” in Proc. IEEE VTC’49, Jul. 1999, pp. 314–319.
[24] ——, “Dual busy tone multiple access (DBTMA)- a multiple access control scheme for ad hoc networks,” IEEE Trans. Commun., vol. 50, no. 6, pp. 975–985, Jun. 2002.
[25] B. Ji, “Asynchronous busy-tone multiple access with acknowledgement (ABTMA/ACK) for ad hoc wireless networks,” in Proc. IEEE GLOBECOM, Dec. 2005, pp. 3643–3647.
[26] W. Yuan, G. Zhu, G. Liu, D. Wu, and M. Chen, “A New MAC Protocol of Ad Hoc Networks,” in Proc. IEEE VTC-Fall, Sept. 2007, pp. 1618–1622.
[27] P. Wang and W. Zhuang, “An Improved Busy-Tone Solution for Collision Avoidance in Wireless Ad Hoc Networks,” in Proc. IEEE ICC, Jun. 2006, pp. 3802–3807.
[28] H. Zhai and Y. Fang, “A Solution to Hidden Terminal Problem Over a Single Channel in Wireless AD HOC Networks,” in Proc. IEEE MILCOM, Oct. 2006, pp. 1–7.
[29] K. Ghaboosi, M. Latva-aho, Y. Xiao, and Q. Zhang, “eMAC - A Medium Access Control Protocol for the Next Generation Ad Hoc Networks,” IEEE Trans. Veh.
Technol., vol. 58, no. 8, pp. 4476–4490, Oct. 2009.
[30] K. Ghaboosi and B.H. Khalaj, “AMACA - a new multiple access collision avoidance scheme for wireless LANS,” in Proc. IEEE PIMRC, Sept. 2004, pp. 1932–1936.
[31] D. Lihong and J. Yan’an, “A Novel MAC Protocol for Hidden Receiver Problem in Ad Hoc Networks,” in Proc. IEEE ICAL, Aug. 2007, pp. 2345–2348.
[32] A. Chayabejara, S.M.S. Zabir, and N. Shiratori, “An enhancement of the IEEE 802.11 MAC for multihop ad hoc networks,” in Proc. IEEE VTC-Fall, Oct. 2003, pp. 3020–
3024.
[33] L.B. Jiang and S.C. Liew, “Improving Throughput and Fairness by Reducing Exposed and Hidden Nodes in 802.11 Networks,” IEEE Trans. Mobile Comput., vol. 7, no. 1, pp. 34–49, Jan. 2008.
[34] ——, “Hidden-Node Removal and Its Application in Cellular WiFi Networks,” IEEE Trans. Veh. Technol., vol. 56, no. 5, pp. 2641–2654, Sept. 2007.
[35] Y. Zhou and S.M. Nettles, “Balancing the hidden and exposed node problems with power control in CSMA/CA-based wireless networks,” in Proc. IEEE WCNC, Mar.
2005, pp. 683–688.
[36] K. Liu and X. Xing, “A Multichannel Reservation Multiple Access Protocol for Mobile Ad Hoc Networks,” in Proc. IEEE ICC, May 2008, pp. 3176–3180.
[37] T. Luo, M. Motani, and V. Srinivasan, “CAM-MAC: A Cooperative Asynchronous Multi-Channel MAC Protocol for Ad Hoc Networks,” in Proc. IEEE BroadNets, Oct.
2006, pp. 1–10.
[38] J. Chen and Y.D. Chen, “AMNP: ad hoc multichannel negotiation protocol for mul-tihop mobile wireless networks,” in Proc. IEEE ICC, Jun. 2004, pp. 3607–3612.
[39] J. Chen, S.T. Sheu, and C.A. Yang, “A new multichannel access protocol for IEEE 802.11 ad hoc wireless LANs,” in Proc. IEEE PIMRC, Sept. 2003, pp. 2291–2296.
[40] S.C. Lo and C.W. Tseng, “A Novel Multi-Channel MAC Protocol for Wireless Ad Hoc Networks,” in Proc. IEEE VTC-Spring, Apr. 2007, pp. 46–50.
[41] K. Liu, T. Wong, J. Li, L. Bu, and J. Han, “A reservation-based multiple access protocol with collision avoidance for wireless multihop ad hoc networks,” in Proc.
IEEE ICC, May 2003, pp. 1119–1123.
[42] E. Shim, S. Baek, J. Kim, and D. Kim, “Multi-Channel Multi-Interface MAC Protocol in Wireless Ad Hoc Networks,” in Proc. IEEE ICC, May 2008, pp. 2448–2453.
[43] G. Bianchi, “Performance Analysis of the IEEE 802.11 Distributed Coordination Function,” IEEE J. Sel. Areas Commun., vol. 18, no. 3, pp. 535–547, Mar. 2000.
[44] F. Alizadeh-Shabdiz and S. Subramaniam, “Analytical models for single-hop and multi-hop ad hoc networks,” in Proc. IEEE BroadNets, Oct. 2004, pp. 449–458.
[45] ——, “MAC layer performance analysis of multi-hop ad hoc networks,” in Proc. IEEE GLOBECOM, Nov. 2004, pp. 2781–2785.
[46] P. Li and Y. Fang, “Saturation throughput of IEEE 802.11 DCF in multi-hop ad hoc networks,” in Proc. IEEE MILCOM, Nov. 2008, pp. 1–7.
[47] T.C. Hou, L.F. Tsao, and H.C. Liu, “Analyzing the throughput of IEEE 802.11 DCF scheme with hidden nodes,” in Proc. IEEE VTC-Fall, Oct. 2003, pp. 2870–2874.
[48] A.A. Abdullah, F. Gebali, and L. Cai, “Modeling the Throughput and Delay in Wireless Multihop Ad Hoc Networks,” in Proc. IEEE GLOBECOM, Nov. 2009, pp.
1–6.
[49] Y. Wang and J.J. Garcia-Luna-Aceves, “Collision avoidance in multi-hop ad hoc networks,” in Proc. IEEE MASCOT, 2002, pp. 145–154.
[50] B.J. Kwak, N.O. Song, and L.E. Miller, “Performance Analysis of Exponential Back-off,” IEEE/ACM Trans. Netw., vol. 13, no. 2, pp. 343–355, Apr. 2005.