Hyacinth: An IEEE 802.11-based Multi-channel Wireless Mesh Network

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Summary
      Even though multiple non-overlapped channels exist in the 2.4GHz and 5GHz spectrum, most IEEE 802.11-based multi-hop ad hoc networks today use only a single channel. As a result, these networks rarely can fully exploit the aggregate bandwidth available in the radio spectrum provisioned by the standards. This architectural limitation prevents multi-hop ad hoc networks from being used as an ISP's wireless last-mile access network or as a wireless enterprise backbone network.

      In this project, we propose a novel multi-channel wireless mesh network (WMN) architecture (called Hyacinth) that can be readily built using IEEE 802.11 a/b/g or IEEE 802.16a technology. Hyacinth equips each mesh network node with multiple 802.11 radios. The central design issues of this multi-radio-based mesh architecture are (1) interface channel assignment and (2) packet routing. For two nodes to communicate with each other, their interfaces need to be assigned to a common channel. However, as more interfaces within an interference range are assigned to the same radio channel, the effective bandwidth available to each interface decreases. Therefore, a channel assignment algorithm needs to balance between maintaining network connectivity and increasing aggregate bandwidth. The routing strategy, on the other hand, determines the load on each 802.11 interface, and in turn affects the bandwidth requirement and thus the channel assignment decision for each interface.

      We have shown that intelligent channel assignment is critical to the performance of multi-channel mesh architecture, and have devised centralized as well as distributed algorithms to assign channels and to route packets. A comprehensive performance study (using both ns-2 simulations as well as a system prototype) shows that even with just 2 radios on each node, it is possible to improve the network throughput by a factor of 6 to 7 when compared with the conventional single-channel ad hoc network architecture. The intuition behind this non-linear improvement is that even use of 2 radios on each node enables the overall network to utilize several channels simultaneously (as shown in Figure below). This breaks each collision domains into multiple collisions domains operating on different frequencies. The Hyacinth prototype currently has 10 nodes that are built using small form-factor PCs (RouterBoard RB-230) each equipped with three 802.11a NICs.

Hyacinth Multi-channel Mesh Network Architecture 

Figure: System architecture of Multi-channel Wireless Mesh Network. End users' mobile devices connect to the network through access point-like traffic aggregation nodes, which form a multi-channel wireless mesh network among themselves to relay the data traffic to/from end user devices. The links between nodes denote direct communication over the channel indicated by the number on the link. In this network, each node is equipped with 2 wireless NICs. Therefore the number of channels any node uses simultaneously cannot be more than 2; the network as a whole uses 5 distinct channels.

 
Publications

 
Presentations

 

Software Downloads
Related Projects at ECSL
Past Works

    Channel Assignment/Routing in Other Networking Fields

  • I. Katzela and M. Naghshineh; ``Channel assignment schemes for cellular mobile telecommunication systems: a comprehensive survey''; IEEE Personal Comm Mag (June 1996)
  • M. Kodialam, T.V. Lakshman; ``Minimum Interference Routing with Applications to MPLS Traffic Engineering''; Infocom 2000.
  • S. Suri, M. Waldvogel, Priyank Ramesh Warkhede; ``Profile-Based Routing: A New Framework for MPLS Traffic Engineering''; Quality of future Internet Services 2001.
  • ``DIMACS Workshop on Multi-channel Optical Networks: Theory and Practice''; Rutgers University, 1998.
  • R. Klasing; ``Methods and Problems of Wavelength-Routing in All-Optical Networks''; Proc. of the MFCS Workshop on Communication, August 1998.

Last modified: 12/10/05