臺灣博碩士論文加值系統

Wireless Mesh Networks (WMNs) have emerged as the next generation of backbones networks in Wireless Local Area Network (WLAN). IEEE has therefore been on the front edge to develop a standard for WMN, which they did by adding a new amendment in the current 802.11 standard: the 802.11s amendment. 802.11s allows traditional wireless access points to act as router at the layer 2 level, by carrying and routing data from devices to gateways, normally out of range of these devices. 802.11s comes with its own routing protocol (HWMP) as well as some new features such as EDCA for channel access to the medium and MCCA, an optional feature that allows nodes to reserve and coordinate their access to the medium in order to avoid collision among them.
However, since MCCA is optional, not all nodes within the mesh network have it enabled. This can results in nodes being unaware of any reservations made by other nodes, thus trying to access the channel at the same time. This disparity can create collision and reduce the mesh network performance.
We propose a new solution to this issue, by creating different planes of communications that will use different non-overlapping channels to transmit data. In every plane, all nodes should have the same features enabled. Therefore nodes without MCCA enabled will not interfere with nodes with MCCA. In that way we can avoid these collisions and hope to increase the network performance by a factor of 3. Since a new solution brings some new trade-offs, tests have also been made to quantify these trade-offs and see their impacts on the performance.

無線網狀網絡(Wireless Mesh Networks, WMN)已經成為無線局域網路(WLAN)的下一代骨幹網路。電子電機學會(IEEE)也因此成為無線網狀網路標準制定的先驅，而他們制定的標準，是透過在目前的802.11標準中添加一個新的修正：802.11s。 802.11s中允許傳統的無線接入點(AP)在網路第二層作為路由器，將數據由設備端路由至閘道器端(通常超出設備本身的通訊範圍)。 802.11s有自行規範的路由協議（HWMP），以及一些新的功能，如EDCA(通道接入)以及MCCA(一個選擇性功能，允許節點保留並協調其通訊，以避免節點間的碰撞。
然而，由於MCCA是選擇性的，不是所有網狀網絡中的節點都啟用此功能。這可能使得某些節點完全不知道任何其他節點保留的通道，從而試圖在同一時間訪問通道。這種資訊落差會造成碰撞，並減低網狀網絡的性能。
針對此議題，我們提出了一種新的解決方法，通過建立不同的通訊平面(plane)，並使之使用非重疊的不同通道來傳輸數據。在每一個通訊平面中，所有節點應該啟用相同的功能。因此沒有MCCA功能的節點不會干擾有MCCA的節點。這樣一來，我們就能避免這些碰撞，並希望能提高網絡的性能為三倍。由於新的解決方案帶來了一些新的權衡，我們也做了一些測試，來量化這些權衡和對性能的影響。

Table Of Contents (p.III)
Table of Figures (p.IV)
List of Acronyms (p.V)
I. Introduction (p.1)
1.1 Background (p.1)
1.2 Problem statement (p.1)
1.3 Purpose (p.2)
1.4 Thesis outline (p.2)
II. WMNs and 802.11s (p.3)
2.1 WMNs (p.3)
2.1.1 Introduction (p.3)
2.1.2 Architecture (p.3)
2.1.3 Key Design Factors and challenges in WMNs (p.7)
2.1.4 Ad-Hoc and MANETs (p.8)
2.2 802.11s (p.8)
2.2.1 Introduction and Architecture (p.8)
2.2.2 Design Factors (p.10)
III. Problem Statement (p.19)
IV. Related Work (p.21)
4.1 eMCCA (p.21)
4.2 MARE (p.22)
4.3 SMA (p.23)
V. Proposed Solution (p.24)
5.1 The 3-Plane Mesh Network (p.24)
5.1.1 The concept (p.24)
5.1.2 The difference with other solutions (p.25)
5.2 Frame Forwarding (p.26)
5.3 Possible implementation (p.28)
5.4 Expected Results and Limitations (p.29)
5.4.1 NS3 (p.29)
5.4.2 Expected Results (p.30)
5.4.3 Limitations (p.31)
VI. Conclusion (p.35)
References (p.36)

[1] I. F. Akyildiz, X. Wang, “A Survey on Wireless Mesh Networks”, IEEE Communications Magazine, vol. 43, no. 9, pp. S23 -S30, 2005
[2] R. Bruno, M. Conti, E. Gregori, “Mesh networks: commodity multihop ad hoc networks”, IEEE Communications Magazine, vol. 43, no.3, 2005
[3] E. Borcoci, “Wireless Mesh Networks Technologies: Architectures, Protocols, Resource Management and Applications”, INFOWARE Conference, Cannes, France, August 2009
[4] IEEE standard for Information Technology, “Telecommunication and information exchange between systems – Local and Metropolitan area network – specific requirements – Part 11 : Wireless Medium Access Control (MAC) and Physical Layer (PHY) specifications : Amendment 10 – Mesh Networking”, IEEE approved draft, 2012 [5] J. Camp, E. Knightly, “The IEEE 802.11s extended service set mesh networking standard”, IEEE Communications Magazine, vol. 46, no. 8, pp 120-126, 2008
[6] IEEE Standards Committee, “Wireless LAN Medium Access Control (MAC) and Physical layer (PHY) specifications: Amendment 8: Medium Access Control (MAC) Quality of Service Enhancements”, IEEE Computer Society, 2005. [7] Krasilov, et al., “Interference, even with MCCA channel access method in IEEE 802.11s mesh networks”, IEEE Eighth International Conference on Mobile Adhoc and Sensor Systems, Valencia, Spain, October 2011
[8] IEEE Standard for 802.11 [9] G. R. Hiertz et al., “IEEE 802.11s: the WLAN mesh standard”, IEEE Wireless Communications, Vol. 17, no. 1, pp 104-111, 2010 [10] M. S. Islam et al., “EFT: a high throughput routing metric for IEEE 802.11 s wireless mesh networks”, Annals of Telecommunications, Vol. 65, no. 5, pp 247-262, 2010 [11] R. Draves, J. Padhye, B. Zill, “Routing in multi-radio, multi-hop wireless mesh networks”, Proceedings of the Tenth annual international conference on Mobile computing and networking, pp. 114-128, Philadelphia, United States of America, September 2004
[12] C.E. Perkins, E.M. Belding-Royer, S.R. Das, “Adhoc On-Demand Distance Vector (AODV) Routing”, IETF Experimental RFC 3561, July 2003.
[13] M. Bahr, “Proposed Routing for IEEE 802.11s WLAN Mesh Networks”, Second Annual International Wireless Internet Conference, Boston, United States of America, August 2006 [14] M. Bahr, “Update on the hybrid wireless mesh protocol of IEEE 802.11s”, IEEE International Conference on Mobile Adhoc and Sensor Systems, pp. 1-6, Pisa, Italy, October 2007
[15] Y. Chen, S. Emeott, “Scheduled mesh access mechanism for an IEEE 802.11 mesh network,” Proceedings of IEEE Wireless Communications and Networking Conference, Las Vegas, United States of America, April 2008
[16] J. R. Gallardo, D. Makrakis, H. T. Mouftah, “MARE: An efficient reservation-based mac protocol for IEEE 802.11s mesh networks”, Proceedings of Second International Conference on Advances in Mesh Networks, pp. 97–102, Athens, Greece, June 2009 [17] M. S. Islam, et al., “eMCCA: An enhanced mesh coordinated channel access mechanism for IEEE 802.11 s wireless mesh networks”, Journal of Communications and Networks, Vol. 13, no. 6, pp 639-654, 2011
[18] K. Xu, M. Gerla, S. Bae, “How effective is the IEEE 802.11 RTS/CTS handshake in ad hoc networks”, Global Telecommunications Conference, Vol. 1, pp. 72-76, Taipei, Taïwan, November 2002
[19] A. Reaz, et al., “Enhancing multi-hop wireless mesh networks with a ring overlay”, Fifth Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks, San Francisco, United States of America, June 2008.
[20] M. Vipin, S. Srikanth, “Analysis of open source drivers for IEEE 802.11 WLANs”, International Conference on Wireless Communication and Sensor Computing, pp 1-5, Chennai, India, January 2010
[21]http://www.nsnam.org [22] P. Fuxjager, D. Valerio, F. Ricciato, “The myth of non-overlapping channels: interference measurements in IEEE 802.11”, Fourth Annual Conference on Wireless on Demand Network Systems and Services, pp 1-8, Obergurgl, Austria, January 2007 [23] W. S. Conner, et al., “IEEE 802.11s Tutorial: Overview of the Amendment for Wireless Local Area Mesh Networking”, IEEE Plenary, Dallas, United States of America, November 2006.
[24] IEEE P802.11s, “Draft amendment to standard-IEEE 802.11s: Mesh Networking”, July 2009