An architecture for seamless mobility in Spontaneous Wireless Mesh Networks

F. Rousseau, Y. Grunenberger, V. Untz, E. Schiller, P. Starzetz, F. Theoleyre, M. Heusse, O. Alphand, and A. Duda, In Proceedings of the 2nd ACM/IEEE international workshop on mobility in the evolving internet architecture, MobiArch’07Available-Online.

Abstract: In this paper, we consider spontaneous wireless mesh networks that can provide wide coverage connectivity to mobile nodes. Our mobility scheme builds upon the separation  between a persistent node identifier and its current address. When joining the mesh, a mobile node associates with a mesh router that updates a location service managed in the mesh as a distributed hash table. Mobility implies changing addresses while a node moves in the mesh. To keep the rate of location updates and correspondent node notifications low, the address of the new mesh router with which the mobile node is associated needs to be topologically close to the previous one. Thus, such a mobility scheme requires an addressing space with specific properties. We achieve this by  defining an algorithm for constructing a pseudo-geographical addressing space: a few nodes know their exact locations and others estimate their relative positions to form a topologically consistent addressing space. Such an addressing space also enables scalable and low overhead routing in the wireless mesh – we propose a trajectory based long distance ballistic geographical routing.

Categories and Subject Descriptors: C.2.1 [Computer-Communication Networks]: Network Architecture and DesignWireless communication

Remarks: This paper studies wide scale wireless mesh networks. It builds upon the separation between the nodal identifiers and addresses.

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Figure 1: Station-to-station communication in the mesh.

Every node has a human readable name (e.g., hostname.domainname), persistant identifier EID (e.g., 130.190.227.184), and physical locator in the mesh (e.g., geo-location of the node). To send a packet to the distant location, the sender has to resolve the corresponding EID of the destination by using the naming service, which is one of the core services in the mesh. Then the sender resolves the relation between the EID and the physical locator by querying the location service. By using the derived locator, the consecutive forwarding nodes compute the next hop, and send the packet further on. Such a mechanism guarantees that every node may be reachable through its permanent EID in spite of mobility, when the nodes frequently change their positions.

We also argue that the mesh network should be based on wireless routers, which do not frequently move and operate uninterruptedly for a long period of time. Such wireless routers shall provide a wireless backhaul for transporting information from any source to any destination in the mesh. Wireless stations should only associate with the desired (the closest) mesh router to get access to the backhaul, which in turn provides station-to-station communication.

The naming service and the location service may be implemented as Distributed Hash Tables (DHTs) by using permanent addresses of routers. Such addresses may be both synthetic or physical (e.g., based on GPS). We argue that physical addresses have certain advantages over synthetic addressing especially in the case of merging two networks.

Keywords: Wireless Mesh Networks, Distributed Hash Tables, Separation between address and locator, seamless mobility, mobility management, handoff.

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