A DHT-based approach for Path Selection and Message Forwarding in IEEE 802.11s Industrial Wireless Mesh Networks * Marcos Pinheiro † , SilvioSampaio and Francisco Vasques IDMEC, FEUP University of Porto {madruga, silviocs, vasques}@fe.up.pt Pedro Souto ISR, FEUP University of Porto pfs@fe.up.pt Abstract Wireless Mesh Networks (WMNs) are a promising com- munication technology that may offer greater flexibility and reliability, when compared to traditional wireless net- works. WMNs open up new applications domains, but still need to find efficient mechanisms to deal with scal- ability and timeliness requirements. This paper proposes a scheme for Path Selection and Message Forwarding in IEEE 802.11s networks, that is suitable to be used in in- dustrial environments. We present the DHT-based Clus- ter Routing Protocol (DCRP), a routing protocol based on DHTs, clustering of nodes and use of proxies. DCRP allows to improve the overall network performance by re- ducing the time required for path selection and the number of communication hops in large sized networks. 1. Introduction Wireless Mesh Networks (WMNs) are a new promis- ing communication technology specially adequate for wireless mobile networks. This type of wireless net- work is characterized by dynamic self-organization, self- configuration and self-healing. These properties enable, among other, fast deployment, low installation cost, and reliablecommunication. WMNsreducethetimeandwork required for creating or updating an existing wireless net- work, as the mesh nodes can dynamically cooperate to update/re-arrange the network. In a WMN the installa- tion costs may be significantly reduced when compared to traditional WLAN, as they require less cabling connec- tions. Unlike traditional WLANs, where there is the need for both a data cable and a power line for each Access Point (AP). A WMNs AP requires only to be connected to a power line. This feature may be very attractive for setting-up industrial plants, where is quite easy to extend power lines, but it is usually difficult to re-cable the plant * This work was partially funded by IDMEC and by FCT/CAPES funding agencies (project SideTrail), and by FCT under project PTDC/EIA/74313/2006. † Marcos Pinheiro is currently on leave from DIMAp-UFRN, Brazil. His contact address at UFRN is: madruga@dimap.ufrn.br. installation in order to get a direct cable connection from the AP to the nearest data communication switch. As a consequence, WMNs are believed to play an important role in future Wireless Industrial Networks [18], reducing installation and reconfiguration costs and increasing the reliability of the wireless communicationnetwork. This work is focused in a particular type of Mesh Net- works: theIEEE802.11sWirelessMeshNetworks,which are the developing IEEE standard for IEEE 802.11 Wire- less Local Area Networks (WLANs) based mesh network- ing. TheuseofIEEE802.11sMeshNetworksinindustrial environmentwill raise two major benefits: higher reliabil- ityofthewirelessnetworkandsupportofahighernumber of APs. The first property arises from the self-healing and self-organizedcharacteristicsofWMNsthatmaintainsthe communicationslinksevenwhenfacingmultiplecommu- nication faults. The second property comes up as conse- quence of the network topology. Typical deployed IEEE 802.11 WLANs consist of a series of wired APs that rely on a wired infrastructure to extend its connectivity. As a result, the dimension of the network is largely restricted bythewiredinfrastructure. Conversely,inaIEEE802.11s Mesh Network, APs can be interconnected in a multi-hop fashion. Thus, the IEEE 802.11s approach allows the setup of large sized networks (with a larger number of nodes). However, as the network size increases, the mesh network may face severe scalability problems. In essence, the available throughput will decay as the network gets bigger. One of the major reasons for this behavior is the increase in the number of hops in the multi-hop network. The longer hop distance in a path will lower down the available throughputover the relay links. The main target of this paper is to propose a novel scheme for path selection and message forwarding in IEEE 802.11s networks, that is especially suitable to in- dustrialenvironments.Ontheonehanditreducesthetime for path selection in order to cope with tighter real-time requirements, and on the other hand improvesthe reliabil- ity and fault-tolerance of the message transmission. The preliminaryresultsofthisworkindicatethatsoftreal-time requirements can be addressed by the joint use of DHTs and clusters in the routing protocol to reduce the num- 978-1-4244-2728-4/09/$25.00 ©2009 IEEE