GB2367208A

GB2367208A - Multi-hop wireless network

Info

Publication number: GB2367208A
Application number: GB0022335A
Authority: GB
Inventors: Keith Edward Mayes; Rajadurai Vijithan; Arulalingam Arulkkumaran; Alan Law
Original assignee: Vodafone Group PLC; Vodafone Ltd
Current assignee: Vodafone Group PLC; Vodafone Ltd
Priority date: 2000-09-12
Filing date: 2000-09-12
Publication date: 2002-03-27
Anticipated expiration: 2020-09-12
Also published as: DE60133397D1; GB0025910D0; WO2002023829A1; GB0022335D0; GB2366951A; DE60133397T2; GB2367208B; GB2366951B; AU2001286068A1

Abstract

A multi-hop wireless network for transmitting data packets between a concentration point (CP) and one of a plurality of radio transceiving nodes (e.g. R1....R6, Y1.....Y4) is described. Each node is allocated to a particular region which is spatially positioned relative to the concentration point (CP) such as a base station. The allocation of each node to a particular region may be carried out according to the distance of the node from the concentration point (CP), by distance measurements carried out by the node itself or by the concentration point (CP), or may be allocated according to the node's position (e.g. using GPS signals). Each node is correspondingly tagged according to its allocated region. Data transmission, for data to be transmitted from a particular node to the concentration point (CP) or in the reverse direction, is carried out according to predetermined rules, and in accordance with these rules each node receiving data for onward transmission may be constrained to transmit the data only to a node in the adjacent region.

Description

2367208 TELECOMMUNICATION NETWORKS AND METHODS The invention relates to

telecommunication networks and methods. A telecommunication network embodying the invention, and to be described in more detail below by way of example only, provides a network for transmitting data (e.g. packet data) from a source to a destination.

According to the invention, there is provided a method for routing data in a wireless network between two spaced radio transceiving nodes in the network, one of the nodes being a concentration point and the other node being a selectable one of a plurality of the nodes spatially positioned with reference to the concentration point, by means of a plurality of hops involving at least one intermediate one of the nodes, in which each node is allocated to a particular one of a plurality of regions which are differently spatially positioned relative to the concentration point, and in which at least one of the hops is constrained to start in one of the regions and end in another of the regions.

According to the invention, there is also provided a wireless telecommunication network, comprising a plurality of radio transceiving nodes, and routing means for routing data between two of the nodes one of which is a concentration point in the network and the other of which is a selectable one of a plurality of the nodes spatially positioned with references to the concentration point, the routing means routing the data between the two nodes by the means of a plurality of hops involving at least one intermediate one of the nodes, means for allocating each of the nodes to a particular one of a plurality of regions which are differently spatially positioned relative to the concentration point, and 2 constraining means for constraining at least one of the hops to start in one of the regions and end in another of the regions.

Telecommunication networks and methods according to the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawing which shows one of the networks.

The telecommunication network to be described is in the form of a wireless network, which may be a cellular network, in which packet data is transmitted from a source node in the network to a destination node. The network comprises one node in the form of a concentration or inner point which may be a base station, and a plurality of other nodes spaced away from and around the concentration point. The nodes may be radio transceivers of any suitable type. The nodes spaced around the concentration point may, for example, be represented by cellular telephone handsets. The source node may be any of the distributed nodes in the network and the destination node is then the base station or concentration point. Instead, however, the concentration point may be the source node, transmitting data to a destination node comprising one of the hand sets. 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 transmitted to another 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 source and destination nodes in a single transmission.

In such a multi-hop network, however, it is necessary to provide a mechanism by which each node selects the next node in the transmission path so as to maximise efficiency of data transmission - thus ensuring that each hop carries the data forward to the destination node in the most efficient direction. For example, if a node simply transmits the data to the intermediate node nearest to it, a very large number of nodes in the network may be involved in the data transmission path to the destination node, considerable increasing the traffic density in the network and reducing its capacity and without necessarily transmitting the data quickly and efficiently.

In accordance with the invention, each node is allocated to a respective region, the regions being spatially arranged with respect to each other. Each region may contain a plurality of the nodes. Each region is given an individual identity (for example, the regions can be colour-coded so that there is a "red" region, a "yellow" region and a "green" region). Each node is given a "tag" which identifies the region to which it belongs. Thus, in the example being considered, each node will be given a red, yellow or green tag. The regions are spatially arranged with respect to the concentration point or base station so that a first region includes the concentration point and the other regions are successively spaced at greater distances from the first region. For example, the regions may be arranged so that each one embraces or surrounds the next region nearer to the concentration point. As a specific example of this arrangement, the regions can be concentric. The regions are normally contiguous.

When the regions have been set up in this way, so that each node has been tagged according to the region in which it is situated, it is then possible to set up rules to control 4 the transmission of data within the network. More specifically, for example, a node in a particular region may be arranged to have data communication only with a node in the next adjacent region - thus excluding communication with another node in the same region or with a node in a region spaced beyond the adjacent region. In this way, data transmission in the network can be expedited.

Figure I shows a network arranged into three regions; a green region 1, a yellow region 2 and a red region 3. Region I contains the concentration point (CP) or base station. Regions 2 and 3 are arranged successively and concentrically around region 1. Such a concentric arrangement is shown by way of example only. The regions could have any suitable shape. In this example, the radius or effective size of the regions increases as their distance from the CP increases.

The CP is always involved in data transmission. Messages may or may not be intended for the CP or may or may not be originated by the CP but in general they always pass through the CP.

I The Figure shows a node G I in the green region 1, nodes Y I, Y2, Y3, Y4 in the yellow region 2, and nodes Rl, R2, R3,R4,R5 and R6 in the red region 3. There may, of course, be many more nodes.

As will be described in more detail below, when data is to be transmitted from a node in the red region 3 to the CP in region 1, the source node in the red region 3 will transmit the data in a first hop to a node in the yellow region 2 which will then in turn transmit the data in a second hop to the CP in region 1. Similarly, when data is to be transmitted from the CP to a node in the red region 3, the CP will transmit the data in the first hop to a node in the yellow region 2 which will then transmit the data in the second hop to the destination node in the region 3.

In order for the system to operate, it is necessary initially for each node to be assigned to, or to assign itself to, a particular one of the regions. This assignment process can be carried out in several different ways (a) The node can determine its own spatial position relative to the CP or base station and can then assign itself to a particular region.

(b) The CP can determine the relative positions of the individual nodes and then assign them to particular regions.

Each node can determine its own position relative to the CP in a number of different ways. For example, it can transmit a signal to the CP and determine its distance from the CP from a reply signal returned by the CP (assuming a particular radio path loss model). Instead, it can determine its distance from the CP by utilising broadcast transmissions from the CP (again assuming a particular radio path loss model). Another possibility is for each node to use an external method to determine its position e.g. using GPS signals.

The sizes, shapes, and relative spatial positions of the regions need not be constant. For example, they can be changed or modified dynamically, and the tags on the individual nodes altered accordingly, in accordance with changing interference patterns.

Although the regions are located spatially with respect to each other, they need not be geographically fixed; for example, they could be regions within a moving environment such as on a train or ship.

Each node may be capable of transmitting information to, and receiving information from, all the nodes in the same region and at least one other node in the neighbouning region.

If a node finds that it cannot transmit data to a node in the next region, it will then transmit to a node in the same region. It can select this node according to a number of different possible rules. It may simply transmit to the closest node. If that node can then successfully dispose of the data (by transmitting to the next region or, possibly, by transmitting to another node in the same region if transmission to the next region is not possible), then the originating node will have completed its task. However, if the node receiving the data from the originating node cannot successfully transmit the data to an onward node, it will inform the originating node which will then attempt transmission via another node. Such an arrangement is more satisfactory than arrangements in which the originating node sends out data indiscriminately.

There may be one or rr-ore dedicated nodes in each region for receiving data from another region and for onward-transmitting it. Alternatively, a node in one region could select a particular node in the next region to receive transmissions, such as in accordance with information previously transmitted to it. Another possibility would be for a node in one region to broadcast-transmit to all the nodes in the next region, the first one in the second region to transmit the data to the next region disabling transmission from the others.

Preferably, the sizes of the regions decrease in the direction towards the CP. This ensures that the lengths of the hops decrease for data transmitted towards the CP and increase for data transmitted away from the CP. This is advantageous because it optimises the capacity in the network.

In a more specific example, a frequency division duplex (FDD) system can be used for routing packets between source and destination nodes in the network. An FDD system requires the use of two different RF camiers, at one frequency for transmitting data and at a second frequency for receiving data. By alternating the transmitting frequencies for the successively arranged regions, and similarly alternating the receiving frequencies for the successively arranged regions, it can be ensured that each node can only transmit data to a node in the next region. For example, the respective transmitting and receiving carrier frequencies can be arranged in the following way:- TABLE

I REGION FREQUENCY RED YELLOW GREEN Tx freq. fl. f2 fl.

Rx freq. f2 fl. f2 If data is to be transmitted ftom a source node in the red region 3 to the CP in the green region 1, it will be initially transmitted at frequency fl. It therefore cannot be received by any of the other nodes in the red region 3 but will be received by a particular node in the yellow region 2 - because the nodes in this region have fl as their receiving 8 frequency. The node in the yellow region 2 which receives the data then re-transmits it with the transmitting frequency f2 so that it will be received by the CP in the green region 1 which has receiving frequency C.

Other transmission and receiving systems (e.g. TDD) can be used instead of FDD, of course. The particular transmission/receiving system does not control the routing of data.

The nodes in different regions may be arranged to provide different services - for example, all the nodes in the red region 3 could have a higher data rate.

9

Claims

A method for routing data in a wireless network between two spaced radio transceiving nodes in the network, one of the nodes being a concentration point and the other node being a selectable one of a plurality of the nodes spatially positioned with reference to the concentration point, by means of a plurality of hops involving at least one intermediate one of the nodes, in which each node is allocated to a particular one of a plurality of regions which are differently spatially positioned relative to the concentration point, and in which at least one of the hops is constrained to start in one of the regions and end in another of the regions.
2. A method according to claim 1, in which the or each constrained hop is a hop from one region to the adjacent spatially positioned region.
3. A method according to claim 2, in which the regions are successively spaced further away from the concentration point.
4. A method according to claim 3, in which there are at least two regions spaced outwardly of the region containing the concentration point, the first one of these embracing the region containing the concentration point and the second one embracing the first region.
5. A method according to claim 4, in which the regions are arranged concentrically.
6. A method according to any preceding claim, in which each node itself deten-nines its region.
7. A method according to claim 6, in which each node determines its region by exchanging signals with the concentration point and/or others of the nodes.
8. A method according to claim 6, in which each node determines its region by reference to signals from outside the network, such as GPS signals.
9. A method according to any one of claims I to 5, in which the concentration point determines the position of the respective nodes and itself allocates them to particular ones of the regions itself.
10. A method according to any preceding claim, in which the sizes of the region are allocated and changed dynamically.
11. A method according to any preceding claim, in which data is transmitted and received using a frequency division duplex system in which the transmitting and receiving carrier frequencies for a node in one of the regions are the same as the receiving and transmitting carrier frequencies, respectively, for a node in the adjacent region.
12. A method according to any preceding claim, in which the length of a constrained hop closer to the concentration point is less that the length of a constrained hop further from the concentration point.
13. A wireless telecommunication network, comprising a plurality of radio transceiving nodes, and routing means for routing data between two of the nodes one of which is a concentration point in the network and the other of which is a selectable one of a plurality of the nodes spatially positioned with references to the concentration point, the routing means routing the data between the two nodes by the means of a plurality of hops involving at least one intermediate one of the nodes, means for allocating each of the nodes to a particular one of a plurality of regions which are differently spatially positioned relative to the concentration point, and constraining means for constraining at least one of the hops to start in one of the regions and end in another of the regions.
14. A network according to claim 13, in which the constraining means constrains the or each constrained hop to be a hop from one region to the adjacent region.
15. A network according to claim 14, in which the regions are successively spaced further away from the concentration point.
16. A network according to claim 15, in which there are at least two regions spaced 12 outwardly of the region containing the concentration point, the first one of these embracing the region containing the concentration point and the second one embracing the first region.
17. A network according to claim 16, in which the regions are arranged concentrically.
18. A network according to any one of claims 13 to 17, in which each node comprises means for determining its region.
19. A network according to claim 18, in which each node determines its region by exchanging signals with the concentration point and/or others of the nodes.
20. A network according to claim 18, in which each node determines its region by reference to signals from outside the network, such as GPS signals.
21. A network according to any one of claims 13 to 17 in which the concentration point includes means for determining the position of the respective nodes and allocating them to particular ones of the regions itself.
22. A network according to any one of claims 13 to 2 1, in which data is transmitted and received using a frequency division duplex system in which the transmitting and receiving carrier frequencies for a node in one of the regions are the same as 13 the receiving and transmitting carrier frequencies, respectively, for a node in the adjacent region.
23. A network according to any other one of claims 13 to 22, in which the length of a constrained hop closer to the concentration point is less than the length of a constrained hop ftirther from the concentration point.
24. A method of routing data in a multi-hop wireless telecommunication network, substantially as described with reference to the accompanying drawing.
25. A multi-hop wireless telecommunication network, substantially as described with reference to the accompanying drawing.