Hierarchical Architecture for Managed Wireless Networks Balázs Kovács
Rolland Vida
Gergely Biczók
Budapest University of Technology and Economics 2, Magyar Tudósok krt., Budapest, Hungary - 1117
Budapest University of Technology and Economics 2, Magyar Tudósok krt., Budapest, Hungary -1117
Ericsson Research Hungary, Traffic Lab 4-20, Irinyi József u., Budapest, Hungary - 1117
[email protected]
[email protected]
[email protected]
ABSTRACT The expected growth in the number of communicating wireless devices claims for a more effective utilization of widespread wireless technologies, like WiFi. In this paper we propose an addressing and routing network architecture that uses multi-hop access to extend the range of managed wireless networks. It provides a scalable and controllable solution to facilitate network configuration and mobility handling in a possibly heterogeneous environment.
1. INTRODUCTION Communication and routing in wireless networks became a popular field of research in recent years. Several ad-hoc routing algorithms have been proposed, one of the most known being AODV (Ad Hoc Ondemand Distance Vector)[1]. Nowadays, providing wireless Internet access at various locations became a necessity. We think that connecting to the wireless infrastructure of a facility will be a frequent event in future networks. Moreover there is a need to provide multi-hop Internet access through other mobile devices to achieve better connectivity.
Our solution involves multiple cooperating access points into a wireless domain under one administration authority to support and enhance the communication of mobile nodes. They provide a distributed lookup mechanism for nodes. The access points are the root nodes of the hierarchies. Each access point spans a hierarchical address tree, to which mobile nodes may join. After all the nodes performed the join procedures, the whole wireless domain will be covered with multiple, distinct, hierarchical address trees. The routing algorithm that builds on the SCARF (Scalable Addressing and Routing Architecture for Future Networks) hierarchical architecture [2], is SCARF-RP.
2.1 Addressing Our concept engages a locator - identifier split, to allow addressing mobile stations either by their node identity or their location. Thus, each node has a Global Node Identifier (GNI), and one or more Local Node Address(es) (LNA).
To support these features, we propose a hierarchical network architecture, together with a routing algorithm capable of multi-path forwarding. It builds on the fix part of the network by pushing some administration load onto the acces points ; thus, it is not an ad hoc routing protocol. The system is able to support both intra- and inter-domain mobility. Its hierarchical architecture facilitates the integration of security mechanisms, and allows aggregated handling of relatively static network groups. It is interoperable with existing networking technologies, like IP; moreover, it can handle network technology heterogeneity.
The attachment to the address trees corresponds to an address distribution procedure. The trees are continuously maintained and updated in function of the mobility of the nodes and the characteristics of the radio connections. A newcomer node learns about the available address trees from the received HELLO messages. At a moment defined by its timers, the node tries to connect to as many address trees as available. In case of positive address negotiation the newcomer is attached to the corresponding address trees and advertises its new addresses to other mobile nodes. Thus, nodes acquire chained addresses that reflect their actual position in a tree. Since multiple access points and thus multiple address trees are used, a node has multiple location aware address.
2. NETWORK ARCHITECTURE
2.2 Node Lookup
The architecture exploits the fact that in managed wireless networks there are access points through which the wired part of the network can be accessed.
Among other tasks, the access points relieve the mobile stations and take over some administration load from them. They operate a distributed Local Address
Directory (LAD) service that stores the valid GNI and LNA pairs for each node. In case a mobile node wants
cooperating access points (SCARF-n, where n is the number of access points). The protocols were tested in ns-2, on a 700x500m area for 400 seconds, with 50
Figure 1 Packet loss to communicate with another mobile node, it sends a node lookup message to the LAD, which serves back he LNA(s) of the desired node. The LAD service has to be updated and kept consistent. In our architecture this task is an integral part of mo bility handling.
Figure 2 Number of control packets nodes having a 250m radio range and a data rate of 11Mb/s. We assumed constant bit rate traffic and random-waypoint mobility pattern, with 40 seconds pause time and a node speed of 7-10 m/s.
The SCARF routing protocol exploits the constructed network architecture. It has no routing tables; instead, packet forwarding is done based on node addresses . Each mobile node is aware of the LNA(s) of its immediate neighbors. After obtaining the LNA(s) of the node it desires to send packets to, the source decides whom to pass the packet. Considering its own address, its neighbors’ addresses, and the destination address(es), it can select the best next -hop neighbor.
Results show that SCARF has comparable performance to AODV in packet loss and in signaling (Figure 1 and Figure 2). However, the functionalities of SCARF and AODV are not identical. Even if both can be used as multi-hop extensions of managed wireless networks, SCARF provides a controllable and flexible solution; it is capable to handle multi-path routing, multi-homing and uses an architecture that facilitates the integration of security primitives. For AODV to achieve that, it should be thoroughly extended, which means more control information and lower performance [3].
2.4 Mobility
4. CONCLUSION
2.3 Routing
The architecture supports intra-domain mobility. Mobility handling can be simplified into two basic sub processes: disconnecting a node and connecting it. During these procedures the LAD has to be properly updated. On disconnection this is the responsibility of the parent node, on connection the newcomer has to notify and register itself to the LAD. Due to its hierarchical nature, the architecture feasibly supports inter-domain mobility. Outside a wireless domain only the domain identifiers of a mobile node must be known in the backbone. Further address resolution can be performed by the administration of a wireless domain.
3. SIMULATION We compared our protocol with AODV and its flavors, AODV-LL (Link Layer) and AODV-OH (Optimized Hellos). SCARF was simulated with 1, 3 and 5
In this paper we introduced a network architecture called SCARF and compared it to AODV. The presented architecture supports the multi-hop extension of managed wireless networks; it creates a hierarchical, multi-route structure in wireless domains. The architecture has integrated support for network heterogeneity, intra- and inter-domain mobility.
5. REFERENCES [1] S.R. Das, et al. Performance Comparison of Two
On-demand Routing Protocols for Ad hoc Networks. IEEE Personal Communications Magazine special issue on Ad hoc Networking, Feb. 2001, p. 16-28. [2] G. Biczók, N. Égi, P. Fodor, B. Kovács, R. Vida:
Scalable Addressing and Routing in Large-Scale Wireless Networks, Production Systems and
Information Engineering, vol. 2. (2004), pp. 143158. [3] E.M. Belding-Royer, Y. Sun, and Ch.E. Perkins.
Global Connectivity for IPv4 Mobile Ad hoc Networks. IETF Internet Draft, draft-royer-manetglobalv4-00.txt, Nov. 2001 (Work in Progress)
