GB2368239A

GB2368239A - Multi-hop packet data routing system

Info

Publication number: GB2368239A
Application number: GB0025673A
Authority: GB
Inventors: Keith Edward Mayes; Rajadurai Vijithan; Arulalingam Arulkkumaran; Alan Law
Original assignee: Vodafone Ltd
Current assignee: Vodafone Ltd
Priority date: 2000-10-19
Filing date: 2000-10-19
Publication date: 2002-04-24
Anticipated expiration: 2020-10-19
Also published as: GB0025673D0; GB2368239B

Abstract

Packet data is routed from a source node to a destination node through a plurality of intermediate nodes, hopping from node to node. The nodes may be any suitable transceiver such as cellular telephone handsets. Hopping the data between nodes minimises the transmission power required and reduces the possibility of interference compared with transmitting data between source and destination addresses in a single transmission. In order to monitor signal quality or aid in recovery processes, all calls must be routed through a central point or mobile switching centre. In a multi point transmission network, data may not be able to be routed through the MSC. A Special node is introduced into the network which can distort the flow of traffic in the network so that data transmissions pass through the special node. The special node may achieve this by producing artificial information relating to the cost or power loss involved in data hops between nodes to ensure that the lowest cost route is through itself.

Description

TELECOMMUNICATIONS SYSTEM The invention relates to telecommunications systems. A telecommunications system embodying the invention, and to be described in more detail below, by way of example only, is for transmitting data in a radio network, such as a cellular telecommunications network.

According to the invention, there is provided a method of transmitting data in a wireless network arrangement between two spaced ones of a plurality of radio transceiving nodes in the network arrangement, one of the spaced nodes acting as a source node for the data transmission and the other one of the spaced nodes acting as a destination node for the transmitted data, the transmission path for the data between the source and destination nodes comprising a plurality of hops involving one or more intermediate ones of the nodes, in which the or one of the intermediate nodes is a predetermined one of the node.

According to the invention, there is further provided a wireless telecommunication network arrangement, comprising a plurality of radio transceiving nodes and routing means for routing data between two spaced one of the nodes one of which is a source node for the data and the other of which is a destination node for the data, the routing means routing the data between the source and destination nodes along a data transmission path by means of a plurality of hops involving one or more intermediate ones of the nodes, the routing means including control means operative whereby the or one of the intermediate nodes is a predetermined one of the nodes.

Telecommunications systems embodying the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure I is a schematic drawing of a network used in one of the systems; Figure 2 is a block diagram showing interconnected networks in one of the systems; and Figure 3 is a flow chart for explaining the operation of one of the networks.

The telecommunication networks to be described are in the form of wireless networks.

Such a network may be a cellular network. In the networks to be described, packet data is transmitted from a source node in the network to a destination node. The nodes may be radio transceivers of any suitable type. The nodes may, for example, be represented by cellular telephone handsets. The source and destination nodes may be any of the distributed nodes may be any of the distributed nodes in the network of a base station or other point in the network. Data is transmitted by hopping-that is, data is communicated between the source node and the destination node in a series of hops, in which the data is received by an intermediate node and then possibly transmitted to another intermediate node, this process continuing until the data reaches the destination node. Such a hopping technique minimises the transmission power required and thus reduces the possibility of radio interference, as compared with an attempt to transmit the data between the source and destination nodes in a single transmission.

In such a data transmission arrangement, it may be necessary or advantageous for the transmitted data to be intercepted. This may be carried out for a number of purposes: for example, to monitor the quality of transmission and/or to assist in recovery in the event of a failure of transmission; to route traffic along a particular path, or away from a particular path, in order to reduce interference; and to enable monitoring for security purposes such as by a security centre in a private network or by a law enforcement agency in a public network. In a cellular telephone network such as a GSM network, voice calls all pass through a central point (a mobile service switching centre or MSC). Therefore, if all voice calls to or from a particular mobile station are to be monitored, this can easily be carried out by or through the MSC. The MSC can be temporarily set up to capture all voice calls being sent from or to a particular mobile station so that they can then be monitored at a control point. However, in a multi-hop data transmission network, as described above, all communication takes place between a pair of nodes, defining the starting and ending points of each hop, and the data does not necessarily pass through a central point. In addition, where some form of central point is utilized, it may not have the functionality to perform the required task of interception or route distortion..

In order to deal with this problem, the multi-hop data network being described employs a special node or"supemode" (SN) which is introduced into the network and which operates to ensure that data transmission paths between any particular pair of source and destination nodes in the network always include a hop which involves the SN. In other words, the SN distorts the hopping process so that it is always involved in data transmission between any pair of source and destination nodes. Therefore, the SN can be used as a means of intercepting data transmission to or from a particular node in the network so that it can be monitored.

The SN can distort the flow of data within the network, in order to ensure that it itself is always included in all data transmission, in various different ways. These will depend on the method of operation of the particular networks, as will now be described in the following examples.

Figure 1 shows a network in which there are a number of nodes, A, B... E, together with the super node (SN) and a node (CN) to which all other nodes communicate. Also shown in Figure 1 are transmission links 10,12, 14... 32 between the nodes and between them and the node CN. Against each transmission path, the"cost"of the link in terms of db is shown. The cost values for the transmission paths passing through the super node SN are cost values which are produced by the SN. They may be broadcast to the nodes A, B... E. by the SN or sent in some other way. For example, the nodes themselves may request the information from the SN or via other nodes. In this way, each node in the network is aware of the cost value, in db, of each link from itself to the other nodes. Therefore, when determining the path on which to send data to reach a particular destination, it uses this information to select the path with the least cost-and this, of course, determines the intermediate nodes to be involved in the hopping process. It will be noted that the super node SN broadcasts an artificially low cost value ouf-lob for the link 10.

If, for example, node A wishes to transmit data to CN, various possibilities are open to it. If it transmits the data to CN via the super node SN, the data will be transmitted via a first hop along link 12 to the SN, at a"cost"of Idb, and then in a second hop via link 10 to the CN, at a cost of-lOdb. The net overall cost will therefore be-9db.

Instead, node A could transmit the data to CN in four hops: first, from node A to node B along link 22 at a cost of I db, then from node B to node D using link 24 at a cost of 1 db, then from node D to node E along link 26 at a cost of I db, and finally from node E to CN along path 28 at a cost of ldb. The total cost of transmission in this way is therefore 4db.

Another possibility would be to transmit the data from node A to node C along link 30 at a cost of Idb, then from node C to node D along link 32 at a cost of Idb, then from node D to node E along link 26 at a cost of I db and finally from node E to CN along link

28 at a cost of 1 db, again at a total cost of 4db.

Therefore, by broadcasting the artifically low value ouf-lob for the link 10, the super node SN forces all data transmissions from node A to CN to pass through the SN.

Similarly, of course, it can act to force data transmissions from each of the other nodes B, C, D and E to pass through SN on their way to CN.

Therefore, if transmissions from a particular node (the"target node") are to be intercepted or monitored, this can now easily be carried out, because all transmissions pass through the SN.

In the case of a full mesh network, where any node can communicate with any other node (that is, all communications are not necessarily directed to the CN as shown in Figure 1), the supemode SN would need to broadcast cost information which would ensure that for each node the shortest route to any other node would be through the super node SN.

Data transmission between nodes can be controlled by arranging the nodes into different groups, the nodes of the different groups being differently marked or"tagged", the system being arranged so that each hop in a data transmission process between a source node and a destination node takes place between a node in one group and a node in the next group.

In one such arrangement, the groups are geographically arranged regions, all the nodes in the same region having the same tag. For example, the tags can be given the names of different colours. Such an arrangement is described, for example, in co-pending U. K. patent application No. 0022335.4. Such a system can be exploited by the SN to ensure that all data transmissions to or from a particular target node pass through the SN. For example, if it is known that the target node carries a"red"tag, the SN can broadcast information requiring that all nodes with a red colour tag must transmit data, or receive data, via the SN. In this way, therefore, all data transmissions to or from the target node can be intercepted at the SN.

Figure 2 shows an arrangement in which there is a main network 40 containing a number of nodes, F, G... K, two ad-hoc networks 42,44 containing further nodes L, M... T, and another network 46. Ad-hoc networks such as networks 42,44 may be formed by groups of isolated nodes. Network 46 is, for example, a network owned by a different network operator.. In this case, the SN is used to provide interconnection for data communication between the ad-hoc networks 42,44 on the one hand and the main network 40 on the other.

In this way, the SN provides an optimal path for communication between the network 40 and the networks 42,44. For example, in the absence of the SN, a node in network 42 might attempt to communicate with a node in the main network 40 via one or more nodes in network 46, thus possibly over-loading that network. Even in the absence of the intervening network 40, a node in the network 42 might attempt to communicate directly with a node in the network 40 by means of a direct hop which might have to be at high power with the risk of creating radio interference.

In each such case, therefore, the presence of the super node SN provides a preferred path for communication between a node in the network 42 and a node in the network 40. Figure 2 also shows the presence of a radio obstacle 48 between the network 44 and the network 40. The presence of this obstacle would mean that direct transmission between a node in network 44 and a node in network 40 would be difficult and would have to involve high power with the risk of creating radio interference. Again, therefore, these problems are avoided by the presence of the super node SN which provides a preferred transmission path between networks 44 and 40.

In addition, the super node SN provides a means for intercepting data communication between a target node in one of the ad-hoc networks 42,44 and a node in network 40.

Since all such communications must pass through the SN, it can intercept them.

In a case where it is required to monitor or intercept data transmissions between a target node in one of the ad-hoc networks 42,44 and another node within the same network, the SN can achieve this by broadcasting"cost"information to the network to ensure that communications to and from the target node always pass through the SN-that is, they will emerge from the ad-hoc network, pass through the SN and then return to the ad-hoc network. Alternatively, of course, another SN can be placed within the ad-hoc network to intercept the communications.

Figure 3 shows steps which may take place at an SN to carry out interception of data transmission. At step I, the super node determines whether a message has been received. If it has, at step II the message is examined. At step III, a determination is made whether the message is appropriate for interception or not. This step will normally involve a determination whether the message has been transmitted from or is being transmitted to the target node.

If the message is determined as being appropriate for interception, at step IV the message is duplicated. The duplicated message is forwarded to a monitoring centre (step V). Here, it may be stored (step VI) for later processing or passed to a law enforcement agency (step VII).

The original message is then processed (step VIII) to determine whether the next hop for the message, or the final destination, is available. If it is, the message is forwarded accordingly (step IX). If not, the message is passed back to the origin.

If at step III it is determined that the message is not appropriate for interception, it is passed directly to step VIII.

Claims

CLAIMS 1. A method of transmitting data in a wireless network arrangement between two spaced ones of a plurality of radio transceiving nodes in the network arrangement, one of the spaced nodes acting as a source node for the data transmission and the other one of the spaced nodes acting as a destination node for the transmitted data, the transmission path for the data between the source and destination nodes comprising a plurality of hops involving one or more intermediate ones of the nodes, in which the or one of the intermediate nodes is a predetermined one of the node.
2. A method according to claim 1, in which one of the source and destination nodes is a selected one ("target node") of the nodes, and in which the data transmission paths between source and destination nodes neither of which is the target node do not necessarily involve the predetermined node.
3. A method according to claim 2, in which the target node is one of a group of the nodes, and in which the predetermined node acts to constrain data transmission paths originating or terminating at any of the nodes in that group to be by means of hops involving the predetermined node.
4. A method according to claim 1, in which the source and destination nodes respectively comprise any ones of the plurality of nodes except the predetermined node.
5. A method according to any preceding claim, in which the predetermined node acts to constrain the data transmission path to include itself as the or the said one of the intermediate nodes.
6. A method according to any one of claims 1 to 4, in which the predetermined node acts on the source node to constrain the data transmission path to include the predetermined node.
7. A method according to claim 2, in which for the data transmission path for which the target node is the source or destination node the or each of the nodes ("initiating node") acting to initiate one of the hops in that transmission path responds to control information to determine the node where that hop ends, and in which the predetermined node acts on the control information for the or at least one of the initiating nodes to ensure that the node where that hop ends is the predetermined node.
8. A method according to claim 7, in which the control information is information relating to the power losses or apparent power losses in the data transmission paths, and in which the predetermined node adjusts the control information so that the apparent power losses for data transmission paths by means of hops involving the predetermined node are less than data transmission paths by means of hops not involving the predetermined node.
9. A method according to claim 4, in which for each data transmission path each of the nodes ("initiating node") acting to initiate one of the hops in that transmission path responds to control information to determine the node where that hop ends, and in which the predetermined node acts on the control information for at least one of the initiating nodes to ensure that the node where that hop ends is the predetermined node.
10. A method according to claim 9, in which the control information is information relating to the power losses or apparent power losses in the data transmission paths, and in which the predetermined node adjusts the control information so that the apparent power losses for data transmission paths by means of hops involving the predetermined node are less than data transmission paths by means of hops not involving the predetermined node.
It. A method according to any preceding claim, in which the predetermined node responds to the identity of the source or destination node by intercepting that data when that node has a particular predetermined identity.
12. A method according to claim 11, in which the predetermined node intercepts the data by copying it and re-transmitting it.
13. A method according to claim 11 or 12, including the step of storing the intercepted data.
14. A method according to any preceding claim, in which the network arrangement includes two different networks each including some of the nodes, the source node and the destination node respectively being in the different networks and in which the predetermined node provides an interconnection between the networks.
15. A wireless telecommunication network arrangement, comprising a plurality of radio transceiving nodes and routing means for routing data between two spaced one of the nodes one of which is a source node for the data and the other of which is a destination node for the data, the routing means routing the data between the source and destination nodes along a data transmission path by means of a plurality of hops involving one or more intermediate ones of the nodes, the routing means including control means operative whereby the or one of the intermediate nodes is a predetermined one of the nodes.
16. A network arrangement according to claim 15, in which one of the source and destination nodes is a selected one ("target node") of the nodes, and in which the data transmission paths source and destination between nodes neither of which is the target node does not necessarily involve the predetermined node.
17. A network arrangement according to claim 16, in which the target node is one of a group of the nodes, and in which the control means comprises means constraining data transmission paths originating or terminating at any of the nodes in that group to be by means of hops involving the predetermined node.
18. A network arrangement according to claim 15, in which the source and destination respectively comprise any ones of the plurality of nodes except the predetermined node.
19. A network arrangement according to any one of claims 15 to 18, in which the

control means comprises means associated with the predetermined node to constrain the I data transmission path to include the predetermined node as the or the said one of the intermediate nodes.
20. A network arrangement according to any one of claims 15 to 18, in which the control means comprises means associated with the predetermined node to cause the source node to constrain the data transmission path to include the predetermined node.
21. A network arrangement according to claim 16, in which the data transmission path for which the target node is the source or destination node the or each of the nodes ("initiating node") acting to initiate one of the hops in that transmission path responds to control information to determine the node where that hop ends, and in which the control means comprises means which acts on the control information for the or at least one of the initiating nodes to ensure that the node where that hop ends is the predetermined node.
22. A network arrangement according to claim 21, in which the control information is information relating to the power losses or apparent power losses in the data transmission paths, and in which the control means adjusts the control information so that the apparent power losses for data transmission paths by means of hops involving the predetermined node are less than data transmission paths by means of hops not involving the predetermined node.
23. A network arrangement according to claim 18, in which for each data transmission path each of the nodes ("initiating node") acting to initiate one of the hops in that transmission path responds to control information to determine the node where that hop ends, and in which the control means comprises means which acts on the control information of at least one of the initiating nodes to ensure that the node where that hop ends is the predetermined node.
24. A network arrangement according to claim 23, in which the control information is information relating to the power losses or apparent power losses in the data transmission paths, and in which the predetermined node adjusts the control information so that the apparent power losses for data transmission paths by means of hops involving the predetermined node are less than data transmission paths by means of hops not involving the predetermined node.
25. A network arrangement according to any one of claims 15 to 24, in which the predetermined node comprises means which responds to the identity of the source or destination node by intercepting that data when that node has a particular predetermined identity.
26. A network arrangement according to claim 25, in which the predetermined node intercepts the data by copying it and re-transmitting it.
27. A network arrangement according to claim 25 or 26, including means for storing the intercepted data.
28. A network arrangement according to any one of claims 15 to 27, in which the network arrangement includes two different networks each including some of the nodes, the source node and the destination node respectively being in the different networks and in which the predetermined node provides an interconnection between the networks.
29. A method of transmitting data in a wireless network arrangement, substantially as described with reference to the accompanying drawings.
30. A wireless telecommunication network arrangement, substantially as described with reference to the accompanying drawings.