GB2378625A

GB2378625A - A communications network using a Banyan tree structure

Info

Publication number: GB2378625A
Application number: GB0215195A
Authority: GB
Inventors: Robert Hancock; Mark Alan West
Original assignee: Roke Manor Research Ltd
Current assignee: Roke Manor Research Ltd
Priority date: 2001-07-03
Filing date: 2002-07-01
Publication date: 2003-02-12
Also published as: GB0215195D0; GB0116224D0

Abstract

A communications network is formed of a number of inter-linked network nodes (such as access routers, base stations and internet gateways) interconnected in a Banyan tree structure so as to provide alternative paths to give increased robustness and redundancy in the event of node failure. The network is particularly suitable for use with a mobile node such as a mobile phone or computer.

Description

A communications network This invention relates to a communications network. It is particularly applicable to a network supporting mobile communications.

A typical telecommunications network is shown in figure 1. The network comprises the Internet, an access network and a mobile node MN. A mobile node is a device such as a computer or mobile telephone that can connect to the access network at more than one location.

The mobile node connects to the access network via access routers AR-1 to AR-3 (these may be base stations in a cellular communications network). It is possible for the mobile node to connect to the Internet via the access network nodes and one of the Internet Gateways.

The nodes in the access network are interconnected in a hierarchical parent child tree like arrangement as shown in figure 2. The lowest nodes in the structure, labelled a to h, correspond to the access routers in figure 1. The uppermost nodes in the tree A and B correspond to the gateway nodes to other networks such as the Internet as depicted in Figure 1. As the mobile node moves physical location a connection will be established to one (or more in some future systems) of the nodes a to h. Further movement may result in a handover process with the mobile node connecting to another one of the nodes a to h.

When the mobile node connects to one of the lower nodes a to h, the new position in the network of the mobile node is passed from the lower node to its parent node and so on up the network. A problem occurs however when the mobile node moves from a connection with node d to node e since in doing so there is no common upper node connected to these nodes.

A further problem with such a network is that if a parent node fails all the nodes below that are effectively disconnected from the network.

The invention arose in an attempt to alleviate or to at least mitigate these problems.

According to the invention there is provided a communications network comprising a plurality of network nodes interconnected in a Banyan tree structure.

By interconnecting the network nodes in a Banyan tree structure there are a number of alternative paths to cater for redundancy in the event of node failure and to update the network as to the movements of mobile nodes. This technique therefore adds resilience and scalability to existing hierarchical mobility solutions without having to change the mobility portocol.

A specific embodiment of the invention will now be described, by way of example only, with reference to the drawing in which:

Figure 1 shows in schematic form a communications network used in the explanation of both the prior art and also the network node structure; Figure 2 shows a prior art communication network node structure; Figure 3 shows a communication network node structure in accordance with the invention; and Figure 4 is an explanatory diagram concerning the operation and advantages of the communication network node structure in accordance with the invention.

With reference to figure 1, the communication network at this level of detail is the same as earlier described. The way in which the nodes in the network are interlinked to provide a node structure is shown in figure 3. The structure is a Banyan tree. The nodes 31 to 34 uppermost in the structure are gateways to other networks, for example the Internet as shown in figure 1. The upper nodes are each linked to two of a set of intermediate nodes 35 to 38. These in turn are each linked to two of a set of lower nodes 39 to 42. Thus rather like the prior art arrangement each node is linked to two nodes below. However, each node is linked to two nodes higher in the hierarchy. Thus node 31 is linked to nodes 35 and 36. Node 32 is linked to nodes 36 and 38. Node 33 is linked to nodes 35 and 37.

The intermediate nodes 35 to 38 are linked in the following way. Each is linked to two nodes above and two below in the hierarchy. Thus, node 35 is linked to upper nodes 31 and 33, and to the two lower nodes 39 and 40. Node 36 is linked to the upper nodes 32 and 31 and to the lower nodes 41 and 42. Node 37 is linked to the upper nodes 33 and 34 and the lower nodes 39 and 40.

As will be understood the lower nodes are each connected to two of the intermediate nodes but explicitly the nodes are connected as follows. Node 39 is connected to nodes 35 and 37. Node 40 is connected to nodes 35 and 37. Node 41 is connected to node 36 and 38. Node 42 is connected to nodes36 and 38.

In essence as is emphasised by the double lines in figure 4 a and b, there are two hierarchical networks of the earlier type combined with two more nodes 32 and 33 and additional connections.

The combination of the two networks and the inclusion of additional nodes and connections enables a greater redundancy to cater for node and link failure. For example, consider a connection made by a mobile node to an access node 40 requiring a connection all the way through to gateway node 33 to say the Internet beyond. There are a choice of two immediately apparent paths. The first path is via node 37 and the second via node 35. The are a number of less direct routes such as for example, 40 to 37 to 39 to 35 to 33. In the event of a failure of the node 37 or the link thereto the connection can be established via node 35.

Similarly, a connection may be made from node 42 to node 31. The connection may be established via nodes 38,32, 36 to 31. An alternative routing may be from 42 to 36 to 31. Thus if node 38 fails the second of these routing may be utilised.

Other connection possibilities may be readily determined from the drawing.

Claims

Claims 1. A communications network comprising a plurality of network nodes interconnected in a Banyan tree structure.
2. A communications network substantially as hereinbefore described with reference to and as illustrated by figures 1,3 or 4 of the drawing.