• The Data Schedule Holdoff Algorithm in Four-way Handshake Pro-cedure
Recalled in Section 5.4, in order to insure the extended confirm messages will arrive before the data schedule starting, we look up the next control message transmitting time of all corresponding nodes, and delay the data schedule starting time if it needed. This procedure reduce the collisions successfully as shown in Table 6.3. However, the performance may be reduced by unneces-sary protections due to the long back-off of data schedules. If a collision never affects the network coding scheme, it can be ignored without any protection.
But it is hard to distinguish a packet whether it needs protection or not.
• The Election Algorithm when Schedules Overlap in Four-Way Hand-shake Procedure
As mentioned in Section 5.3, the extended confirm handling procedure needs to decide which node can transmit data when a extended confirm schedule is overlapped with existing data schedules. In this thesis, we use a simple method to make the decisions as explained in Section 5.3. However, this method may cause unfair conditions. That is, some nodes always win the election and some nodes are forced to yield the transmission opportunities. The new algorithm must be designed to deal with the fairness issue.
Chapter 8 Conclusion
In this thesis, we propose an easy-to-implemented and easy-to-deployed inter-session network coding scheme that is based on the opportunistic approach. Our proposed scheme need not employ an additional protocol to find coding opportunities or coding structures instead of other researches. Oppositely, our proposed scheme exploits only routing and MAC-layer information to find coding opportunities and coding structures. Using this advantage, it is easier to be realized in a real-life network.
In addition, in this thesis, we point out a new “extended hidden terminal prob-lem,” which can frequently occur in a wireless network using network coding. The
“extended hidden terminal problem” can result in the failure of network-coded packet decoding, thus significantly decreasing the performance of a network-coded wireless network. We explain why the “extended hidden terminal problem” cannot be solved by the currently-existing wireless network standards, such as the IEEE 802.11(b) and the IEEE 802.16(d) specifications. Moreover, we also propose a band-width reservation mechanism that is extended from the IEEE 802.16(d) mesh-mode three-way handshake procedure to prevent the “extended hidden terminal problem”
from occurring.
Although our mechanism proposed in this paper is specific to the IEEE 802.16 mesh network, it can be used as an example protocol design to eliminate the “ex-tended hidden terminal problem” for other network-coded wireless networks.
Finally, the simulation results show that the throughput performance of a net-work using our proposed scheme is better than that of a netnet-work using the traditional routing. In addition, the performance of our proposed four-way handshake design is worthy of being further study.
Bibliography
[1] “802.16d 2004. Draft IEEE standard for local and metropolitan area networks -Part 16: Air interface for fixed broadband wireless access systems”. May. 2004.
[2] R. Ahlswede, N. Cai, S. R. Li, and R. W. Yeung. “Network Information Flow”.
IEEE Transactions on Information Theory, pages 1204–1216, July. 2000.
[3] P. A. Chou and Y. Wu. “Network Coding for the Internet and Wireless Net-works”. June. 2007.
[4] P. A. Chou, Y. Wu, and K. Jain. “Practical Network Coding”. 51st Allerton Conf. Communication, Control and Computing, Oct. 2003.
[5] H. Chu. “Simulating WiMAX Mesh Networks over the NCTUns Network Simulator”. June. 2006.
[6] A. Eryilmaz and D. Lun. “Control for inter-session network coding”. In Proceedings of the Workshop on Network Coding, Theory and Applications, 2007.
[7] K.-H. Fang. “A Novel MAC-layer Scheduling Scheme for Improving Qos Sup-port in IEEE 802.16(d) Mesh Networks”. June. 2007.
[8] A. A. Hamra, C. Barakat, and T. Turletti. “Network Coding for Wireless Mesh Networks: A Case Study”. In Proceedings of IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM’06), 2006.
[9] T. Ho, Y. Chang, and K. J. Han. “On constructive network coding for multiple unicasts”. invited paper, 44th Allerton Conference on Communication, Control and Computing, 2006.
[10] T.-W. Hsu. “Using Steerable Direction Antennas to Improve the Performances of IEEE 802.16(d) Mesh Networks”. June. 2007.
[11] S. Katti, S. Gollakota, and D. Katabi. “Embracing Wireless Interference:
Analog Network Coding”. In Proceedings of the ACM SIGCOMM, 2007.
[12] S. Katti, H. Rahul, W. Hu, D. Katabi, and M. Medard. “XORs in the air:
practical wireless network coding”. In Proceedings of Sigcomm 2006, pages 243–254, September. 2006.
[13] A. Khreishah, C.-C. Wang, and N. Shroff. “An Optimization Based Rate Con-trol for Communication Networks with Inter-session Network Coding”. IEEE Infocom, Phoenix, Arizona, USA, April. 15-17. 2008.
[14] S. Omiwade, R. Zheng, and C. Hua. “Butterflies in the mesh: lightweight localized wireless network coding”. In Proceedings of 4th Workshop on Network Coding, Theory, and Applications (Netcod), 2008.
[15] S. Sengupta, S. Rayanchu, and S. Banerjee. “An Analysis of Wireless Network Coding for Unicast Sessions: The Case for Coding-Aware Routing”. In Proceed-ings of the 26th IEEE International Conference on Computer Communications (INFOCOM 2007), pages 1028–1036, May. 2007.
[16] C.-C. Wang and N. Shroff. “On Wireless Network Scheduling with Interses-sion Network Coding”. In Proceedings of the 42nd Conference on Information Sciences and Systems, Princeton, USA, Mar. 19-21. 2008.
[17] S. Wang, C. Chou, C. Huang, C. Hwang, Z. Yang, C. Chiou, and C. Lin. “The Design and Implementation of the NCTUns 1.0 Network Simulator”. Computer Networks, 42(2):175–197, June. 2003.
[18] S. Wang, C. Chou, and C. Lin. “The Design and Implementation of the NC-TUns Network Simulation Engine”. In Elsevier Simulation Modelling Practice and Theory, 2007.
[19] S. Wang, C. Lin, K. Fang, and T. Hsu. “Facilitating the Network Entry and Link Establishment Processes of IEEE 802.16 Mesh Networks”. In Wireless Communication and Networking Conference 2007 (WCNC 2007), Mar. 2007.