GB2353665A

GB2353665A - Telecommunications system

Info

Publication number: GB2353665A
Application number: GB9919637A
Authority: GB
Inventors: Andrew George Lauder; Peter Wood
Original assignee: Nokia Telecommunications Oy
Current assignee: Nokia Oyj
Priority date: 1999-08-20
Filing date: 1999-08-20
Publication date: 2001-02-28
Anticipated expiration: 2019-08-20
Also published as: GB2353665B; WO2001015395A1; GB9919637D0; AU6582800A

Abstract

A telecommunications system has a main telecommunications network for carrying data to be transmitted over the system by users thereof, and a remote management network for carrying signals relating to the operation of the system, the system incorporates service telephone communications means for enabling additional telephone communications to occur over said subsidiary network. The service telephone communications means is operable to cause data constituting said additional communications to be transmitted over the management network as a stream of internet protocol data packets for transmission over the management network.

Description

2353665 TITLE: TELECOMMUNICATIONS SYSTEM

Field of the Invention

This invention relates to a telecommunications system, for example a digital telecommunications system, and to the provision of a service communications facility (for example a service telephone, also known as an Engineers' Order Wire or an Engineering Order Wire) for such a system. The invention also relates to a method of providing audio telecommunications between two sites on a subsidiary network of a telecomminica tions system.

Background to the Invention

Telecommunications operators often require one or more service telephones to be provided at each node of their telecommunications system. A service telephone enables a technician at a given node to communicate either with service telephones at other nodes or with the management centre of the system. The service telephone facility is particularly important in areas where there is little or no mobile phone coverage, for example underground or in remote areas, in which the service telephone might therefore provide the sole means by which a technician can communicate with other technicians or the management centre.

The service telephone apparatus is usually compatible with any sort of telecommunications equipment which might constitute a node of the telecommunications system, and provides an,out of band', connection to other service telephones or the management centre so that the service telephone facility does not use any saleable pay load capacity of the system, ie capacity of the system to carry the telecommunications signals, the pay load, to or from subscribers to the service provided by the system.

2 In known digital PDH or SDH telecommunications systems, one or more bytes in the traffic overhead are allocated for the service telephone signals. For example, the El and E2 bytes in the SDH section overhead are used for this purpose. These bytes provide a time domain multiplexed (TDM) channel, normally at 64kbits/s, between the sites. Dedicated service telephone hardware in the transmission equipment allows these channels to be connected together to form a dedicated engineering orderwire ser-vice telephone network through the transmission network, and allows a service telephone at a given site to be connected to this network.

However, this sort of service telephone system requires the traffic overhead to be such as to be capable of providing the dedicated overhead bytes, and in some cases, for example on optical networks or ATM networks, no such bytes are available. Furthermore, specialised, and hence relatively expensive, equipment is needed in order to provide an interface between the service telephones and the telecommunications network. Furthermore, the network needs to be specially configured by its management system to handle the bytes in the traffic overhead that are dedicated to carrying service telephone communications.

Summary of the Invention

According to a first aspect of the invention, there is provided a telecommunications system having a main telecommunications network for carrying data to be transmitted over the system by users thereof, and a subsidiary network for carrying signals relating to the operation of the system, wherein the system incorporates service communications means for enabling additional communications to occur over said subsidiary network, wherein said service communications means is operable to cause data constituting said additional communications to be transmitted over the subsidiary network as a stream of packet switched protocol data packets for transmission over the 3 subsidiary network.

Preferably, the data packets use internet protocol data packets.

The invention thus enables,out of ban& service communications to occur without the need for the provision of any dedicated engineering orderwire channels. Furthermore, the equipment for dealing with internet protocol data packets is in widespread use, and is therefore relatively cheap. Accordingly, the setting up of a telecommunications system to include the service communications means will be less expensive than sett-ing up a dedicated engineering orderwire network on the system.

Since all sites in the telecommunications network will have a connection to the management network, the invention is able to provide a service telephone facility at all sites, with the management network constituting said subsidiary network.

Preferably, the service communications means is so arranged as to provide a service telephone communications facility over said subsidiary network.

Preferably, the subsidiary network comprises a remote management network of the system, the service communications means being operable to transmit streams of internet protocol data packets on management channels provided by the remote management network.

The service communications means may to advantage comprise two or more signal transceivers, each situated in the vicinity of, and connected to, a respective node of the telecommunications system.

Preferably, each transceiver comprises telephone apparatus for connecting an audio input into said stream of internet protocol 4 data packets for transmission and for converting a stream of internet protocol data packets received by the telephone apparatus into an audio output.

Sites in the system may be connected together with point to point VoIP links, and to that end, each transceiver is preferably connected to a respective voice hybrid means which is, in turn, connected to at least one other corresponding voice hybrid means at an adjacent node. the voice hybrid means being operable to combine streams of internet protocol data packets from said other voice hybrid means with the stream generated by its respective transceiver so that all the voice hybrid means cooperate to create a single service communications network.

Alternatively, the transceivers may be connected directly to the management network which will convey the internet protocol data packets from one transceiver to a selected other transceiver using existing routing facilities in the management network.

Part of the network of the telecommunications system may have a service telecommunications facility provided by dedicated Engineers' Order Wire bytes in the traffic overhead of the system, in which case the system preferably includes interface means for enabling service telecommunications from that part of the network to be transmitted as said IP packets over another part of the network and vice versa.

The invention also lies in a method of providing audio telecommunications between two sites on a telecommunications system having a main network for carrying data to be transmitted over the system by users thereof, and a subsidiary network for carrying management signals and data relating to the operation of the system, the method comprising the steps of converting a voice input at one of said sites into a stream of internet protocol data packets, relaying said stream to the other site along the subsidiary network and converting the stream into an audio output at said second site.

The invention also lies in a node of a telecommunications system, in accordance with the first aspect of the invention, the node having service telecommunications means for converting a service telecommunications input into a string of switched protocol data packets for transmission over the subsidiary network of the system and receiving such packets from the subsidiary network and converting them into a service telecommunications output.

Brief Description of the Drawinqs

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a simplified telecommunications system in accordance with the invention; Figure 2 is a block diagram of one embodiment of service telephone equipment provided at a node of the system; Figure 3 is another block diagram, corresponding to Figure 2, showing service telephone apparatus adapted to be connected to an engineering orderwire link; and Figures 4 and 5 are block diagrams, corresponding to Figure 2, each showing a respective further embodiment of service telephone apparatus at a node of the system.

Detailed DescriDtion The telecommunications system is an SDH system having six nodes referenced station 1 - station 6. The nodes are interconnected by means of, for example, optical or electrical cables, and these links are indicated by the solid lines, for 6 example the line 10. The signals received along the links comprise a payload, ie the data which a customer wishes to transmit over the system, and an overhead which carries information required for the operation of the network. On some of the links between adjacent nodes, the overhead carries instructions and data relating to the management of the system, and those links provide a remote management network which, in Figure 1, is indicated by broken lines, for example line 12, between adjacent nodes.

The management network is also able to carry voice telecommunications signals between service telephones at the nodes. In Figure 1, service telephones 14 and 16 are respectively provided at nodes/stations 1 and 3.

Each service telephone forms part of a respective service communications means for its node. Since the service communications means are identical with each other, only that at the node 3 will be described.

Each site (ie node) in the network has a service telephone function that has its own internet protocol (IP) address constituted by an internet address and a port number at that address. This function enables the node to receive voice internet protocol (VoIP) packets and convert them into voice data for passing the voice data to a voice hybrid function.

With reference to Figure 2, the node 3 thus has a voice hybrid device having three input/output ports, each connected to a respective one of three VoIP devices 20, 22 and 24. Each of the VoIP devices is, in turn, connected to the corresponding device in the adjacent node over the preexisting management network connection, normally in the I'D" overhead bytes. Thus, the device 20 is connected to a VoIP device in the node 4, the device 24 to a VoIP device in the node 2 and the device 22 to a corresponding device in the node 6.

7 A further port on the voice hybrid device 18 is connected to the telephone 16 via an interface 26 for converting PCM codes to analyse audio signals and vice versa.

The voice hybrid device 18 combines the PCM encoded voice data received on its ports from the VoIP devices (i.e. the voice data. from service telephones at other nodes) with data from the local service telephone interface 26, and the voice hybrid devices of the network therefore create a single service telephone network that is shared between all sites.

The voice hybrid devices may operate in the digital or analogue domains. Preferably, however, the devices operate in the digital domain since such operation does not introduce any additional noise into the channels that are relayed by the voice hybrid device through to other nodes.

The VoIP device takes a PCM data stream and divides it into data packets which are then transmitted using the Internet protocol. Optionally the VoIP devices may use voice compression techniques to reduce the amount of data that is transmitted. Optionally the VoIP function may perf orm ', silence suppression,' (not transmitting packets when the input PCM codes correspond to a low level, that is taken to be silence), to further reduce the amount of data that is transmitted. Received packets are re- assembled by the VoIP devices into a PCM data stream, with any necessary decompression.

The service communications means of the apparatus shown in Figures 1 and 2 provide a service telephone network which, functionally, is the same as that provided on a conventional engineering orderwire network. Thus, the management network is used to provide a common service communications channel which is such that an engineer using one telephone can confer with one or more other people at other service telephones on the network.

8 If required, standard tone dialling techniques can be used to enable an engineer to call an individual site in the same way as happens over a conventional engineering orderwire network.

The functional similarities of the communications means and conventional engineering orderwire networks allow the communications means of the network shown in Figure 1 to be connected to an engineering orderwire link with an existing service telephone network. Figure 3 shows a node which provides this facility. All but one of the elements shown in Figure 3 correspond to elements of the node shown in Figure 2. Each of these elements is therefore identified by the reference numeral of the corresponding component, as shown in Figure 2, raised by 50.

In this node, the voice hybrid device 68 is connected to a VoIP device 70, a service telephone interface 76 and to an engineering orderwire termination 80 which is, in turn, connected to an engineering orderwire link of an existing, conventional service telephone network. The engineering orderwire termination 80 extracts the service telephone data transmitted on the conventional network from the engineering orderwire bytes in the traffic overhead and supplies them to the voice hybrid device 68 which mixes the data with other data as described above. The termination 80 also inserts the summed data into the orderwire bytes to enable the data to be transmitted over the conventional network. Thus, a service telephone call made over the engineering orderwire network can be received by a service telephone, for example the telephone 66 (or 14) of a network in accordance with the present invention.

Figure 4 shows a telecommunications node having an alternative type of service communications means. In this case, the node has its own respective internet protocol address for service telephone communications.

i 9 The node, generally referenced 100, has a VoIP device 102 which is connected to a service telephone 104 similar to the telephones 14, 16 or 66. The device 102 is also connected to an internet protocol routing device 106 which monitors the information being relayed along the management network through the device 106, and extracts the internet protocol data packets carrying service telephone communications addressed to the service telephone 104. The node shown in Figure 5, generally referenced 150, has service communications means which comprise a routing device 156 similar to the device 106. This device is connected to a dedicated internet protocol telephony handset 154 (or a computer running VoIP software) which performs the same functions as the service telephone 104 and VoIP device 102 of the node 100.

As with the apparatus shown in Figures 1 and 2, the routing devices of either of these nodes are connected to the corresponding device(s) in the adjacent nodes, since the management network links are point to point links. However, each node (shown in Figures 4 and 5) implements an IP routing function that enables it to forward IP packets that are not for that node on towards the correct destination node. It should be noted that "adjacency" is, in this context, a logical concept. It is possible to configure point to point links that pass through a number of intermediate nodes without being terminated at those nodes. This is a standard part of management networks.

IP packets are routed through the network based on their destination address. A VoIP function will include the address of its partner VoIP function in each of the packets that it generates. It is the responsibility of the management network to deliver each packet to the nominated destination address.

Thus, a system which uses service communications means as shown in Figures 4 or 5 provides a virtual private network for service telephone traffic, with selected sites being individually dialled by making an internet protocol connection to the appropriate site.

This approach therefore enables multiple simultaneous calls to be made, and can also support conference calls through standard multi-casting techniques.

Since all the sites in a telecommunications network have a remote management connection, the invention is able to provide a service telephone at all sites regardless of whether or not the equipment at that site can provide engineering orderwire overhead bytes. Furthermore, there is no need for separate configuration of the service telephone network as the invention makes this part of the remote management data network.

It will be appreciated from the examples described above that the voiceover internet protocol functionality can be implemented in the telecommunications equipment or in external equipment connected to the remote management network (for example over a local Ethernet connection).

In the examples described above, it is necessary for the remote management network to be able to route internet protocol data in order to enable the service telephone function to be provided. However, the network can be configured to enable service telephone communications to be made with sites at other types of network (for example over a Q3/CLNS management network). This can be achieved by using internet protocol tunnelling functions which wrap the VoIP packets inside the data transport packets of the other network.

Although the service telephone facility has been described in relation to the provision of voice communications, a service communications network in accordance with the invention can be used to provide other forms of communication. For example, the service communication means could be configured to provide a video phone service.

Claims

1 A telecommunications system having a main telecommunications network for carrying data to be transmitted over the system by users thereof, and a subsidiary network for carrying signals relating to the operation of the system, wherein the system incorporates service communications means for enabling additional communications to occur over said subsidiary network, wherein said service communications means is operable to cause data constituting said additional communications to be transmitted over the subsidiary network as a stream of switched protocol data packets.

2. A-system according to claim 1 in which the service communications means is operable to cause data constituting said additional communications to be transmitted over the subsidiary network as a stream of internet protocol data packets.

3. A system according to claim 1 or claim 2, in which the service communications means is so arranged as to provide a service telephone communications facility over said subsidiary network.

4. A system according to any of the preceding claims, in which the subsidiary network comprises a remote management network of the system, the service communications means being operable to transmit streams of internet protocol data packets on management channels provided by the remote management network.

5. A system according to any of the preceding claims, in which the service communications means comprises two or more signal transceivers, each situated in the vicinity of, and connected to, a respective node of the telecommunications system.

12

6. A system according to claim 5, in which each transceiver comprises telephone apparatus for connecting an audio input into said stream of internet protocol data packets for transmission and for converting a stream of internet protocol data packets received by the telephone apparatus into an audio output.

7. A system according to claim 5 or claim 6, in which each transceiver is connected to a respective voice hybrid means which is, in turn, connected to at least one other voice hybrid means at an adjacent node, the voice hybrid means being operable to combine data received from said other voice hybrid means with the data supplied by its respective transceiver means so-that all the voice hybrid means cooperate to create a single service communications network.

8. A node for a telecommunications system according to any of the preceding claims, the node having service telecommunications means for converting a service telecommunications input into a string of switched protocol data packets for transmission over the subsidiary network of the system and receiving such packets from the subsidiary network and converting them into a service telecommunications output.

9. A method of providing audio telecommunications between two sites on a telecommunications system having a main network for carrying data to be transmitted over the system by users thereof, and a subsidiary network for carrying management signals and data relating to the operation of the system, the method comprising the steps of converting a voice input at one of said sites into a stream of internet protocol data packets, relaying said stream to the other site along the subsidiary network and converting the stream into an audio output at said second site.

10. A system substantially as described herein with reference 13 to, and as illustrated in, Figures 1 and 2 of the accompanying drawings.

11. A system substantially as described herein with reference to, and as illustrated in, Figure 3 of the accompanying drawings.

12. A system substantially as described herein with reference to, and as illustrated in Figure 4 and/or 5 of the accompanying drawings.

13. A method substantially as described herein with reference to the accompanying drawings.

14. A node substantially as described herein with reference to, and as illustrated in, any of Figures 2 to 5 of the accompanying drawings.