AU726064B2 - System and method for providing services to subscriber stations connected to an access network - Google Patents

Description

SYSTEM AND METHOD FOR PROVIDING SERVICES TO SUBSCRIBER STATIONS CONNECTED TO AN ACCESS NETWORK FIELD OF THE INVENTION The invention relates to an access node for use in an access network, an access network for providing data communication between at least one subscriber station and at least one service network and a telecommunication system including a number of subscriber stations, a service network and an access network. Furthermore, the invention relates to a method for providing services from a service network to one or more subscriber stations connected to an access network.

BACKGROUND OF THE INVENTION Access networks now play an important role in providing efficient data communication between a number of subscriber stations. Such an access 15 network is generally configured as is shown in figure 11. A number of subscriber stations SS-1, SS-2, SS-3, SS-4 are connected respectively to an access node AN1, AN2, AN3, AN4 via a respective data communication or traffic path TRP1, TRP2, TRP3, TRP4. As is shown with the dotted line in figure 11, it is also S: possible to connect two subscriber stations SS-1, SS-5 to one and the same access node AN1. The access nodes AN1 to AN4 are interconnected via traffic S paths, in the simplest case only with one adjacent access node, as is indicated with the traffic path TRP12, thus forming the access network AN for the subscriber stations. As is indicated with dotted lines, of course each access node S can be interconnected with several other access nodes. For example, in normal i: 25 telephony, the traffic paths TRP1, TRP2, TRP3, TRP4 will each use a 64Kbit/s channel of digital data, resulting from a digital decoding of the respective analog speech signal. For setting up a connection between a subscriber station e.g.

SS-1, and the respective access node, e.g. AN1, the concerned access node AN1 must be able to interpret the signalling protocol used by the respective subscriber station SS-1. Once the connection has been set up, the data communication can take place. In figure 11, such a signalling protocol or signalling format is schematically indicated by SS-F. Further, whilst figure 11 shows all subscriber stations SS-1, SS-2, SS-3, SS-4 to use the same signalling format SS-F, in principle, depending on the capabilities of the respective access nodes AN1, AN2, AN3, AN4, each subscriber station depending on its capability may have a different signalling format. Within the access network AN, the data communication between two respective access nodes can use the same signalling format as is used by the subscriber stations, however, generally, data communication between the access nodes can also be different, i.e. the signalling format for the data communication can be freely selected according to need.

The structure of such an access network as shown in figure 11 is very general and can be applied both to a private networks or public networks, as is e.g. in DE 42 30 561 Al. Such access networks are particularly advantageous, since the subscriber stations themselves must only know that they can hook up to an access node, whereas they do not have to take care of how the data communication with respect to a number of subscriber stations is physically :o 15 maintained within the access network. Hence, the access network can be treated as an abstract entity, as is shown with the abstract boundary AB in figure 11.

US 5 386 417 discloses a method and an apparatus for establishing connections in a communications access network. A number of terminals S: constituting subscriber stations are connected to a remote terminal acting as an access node. The remote terminal is connected to the central office via a traffic path. The remote terminal constituting the access node comprises a time slot interchange means and a control means. In particular, the time slot interchange .is provided for performing a cross-connection of time slots on the traffic path i9 between the subscriber station and the remote terminal and between the remote 25 terminal and the central office. A signalling message indicating that an incoming call has been received and other call-processing-related messages are transmitted within a so-called call processing signalling channel or CPSC, that is carried within a particular time slot on the traffic path between the subscriber station and the remote terminal. This time slot also carries the time slot assignment signalling channel TASC which is responsible for the time slot assignment. Time slots to carry a received call a negotiated first over the TASC ,iZNbetween the central office and the remote terminal and then between the remote 3 terminal and the subscriber station wherein a connection on a call-by-call basis is established. The negotiated time slots are thereupon interconnected and the call is then processed by the fixed time slot cross-connection. Therefore, here a communication path is set up via the signalling channel CPSC and when the communication path has been established the pay load data is transmitted on the allocated time slots between the subscriber station and the central office through the remote terminal. The document only relates to the call processing and not the providing of services from a service network.

The European Telecommunication Standards Institute (ETSI) has now compiled general guidelines of how such access networks should be handled, e.g. regarding the use of protocols, the transmission systems and fault management. This is e.g. described in reference DTRITM-2222 "The Management of Access Network" published by ETSI TM2 Access Network SEG, Copenhagen, 12-16 September 1994.

15 Whilst in the past access networks were solely used to enable the subscriber stations to exchange data and/or talk to each other, more advanced telecommunication techniques allow to provide additional services to the subscriber stations. According to the definitions in the aforesaid ETSI-reference such service provisioning functions include all procedures which are 20 necessary to establish a service to the subscriber. Such additional services may e.g. teletext, video communication, etc., which can e.g. be provided through an additional ISDN-link.

Starting with an access network according to figure 11, figure 12a shows how these services are provided to the access network and thus to the subscriber 25 stations by a service network SN. The service network SN may be a single local exchange or a number of interconnected local exchanges. Hereinafter, the term "service network" will be used, should however be understood as including all such possibilities. A similar architecture is shown in the afore-mentioned DE 42 30 561 Al, wherein a private network can provide data communication between subscribers and also provide some services, e.g. a call protocol system, to subscribers which are connected within a public network.

However, as is shown in figure 12a, rather than using the signalling format SS-F of the subscriber stations, the services network SN can use its own signalling protocol or signalling format SN-F on its interconnection traffic path TRP-SN. Therefore, initially the service network SN does not know to which access node AN1, AN2 it can be connected, i.e. whether it is the access node AN1 or the access node AN2, which will have a termination point (shown with the black dot in figure 12a) supporting its signalling format. In addition, as is shown in figure 12a, the used traffic path TRP-SN will have to be a line of larger bandwidth than the ones used by the subscriber stations for transmitting the services.

Therefore, when in figure 12b the subscriber station SS-1 requests services, the access node AN1 must first be identified and checked, whether it is adapted for setting-up a signalling format used by the service network SN. If so, the line is terminated at the access node AN1 by setting up the signalling format on the traffic path TRP-SN. With this fixed connection of the traffic path TRP-SN, 15 services can be provided to the subscriber station SS-1, wherein the term "providing of services" of course includes the transmitting of data to the subscriber t ao station SS-1 as well as the receiving of response data from the subscriber station SS-1. In this respect, it is also to be understood that "subscriber station" is used here as a generic term, that not only includes a telephone, but also other devices 20 like a computer, a screen, an answer phone etc.

Considering figure 12b, where the subscriber SS-1 has requested the services from the service network SN, the situation shown there corresponds to the physical spanning of an individual line between the service network SN and 0" 90 the subscriber station SS-1, namely through the access node AN1 capable of 25 terminating or setting-up the line. Considering the fixed set-up of the line as in figure 12b, of course this leads to a major disadvantage, when the subscriber station SS-2 also requests services from the service network SN. Assuming in figure 12c, that AN2 cannot support the signalling format and it is only access node AN1, which can be used for a connection of the service network SN, then the provision of services to the subscriber station SS-2 can only be established through the access node AN1. This is shown with dotted lines in figure 12c.

However, as long as the subscriber station SS-1 also requesting services occupies the traffic path TRP-SN-TRP1, this traffic path is not available to other subscribers. Then, the link through AN1 is established for the other subscriber SS-2. Since no direct connection can be established to AN2, this concept is called "virtual connection concept". Such a virtual connection concept is also used in DE 42 30 561 Al in order to provide additional services to a number of subscriber stations.

As is schematically shown in figure 12d, of course the situation worsens, if there is a further subscriber SS-4 also simultaneously requesting services from the service network SN. In this case, two virtual connections VC,, VC 2 must be established. Despite such virtual connection concept being generally known also in the field of ATM-switching systems (see e.g. WO 94/09576) they result in the major disadvantage, that not only the abstraction level of the access network as established in figure 11 is destroyed, but more importantly, the network resources 15 are not optimally used.

As explained before, the service network SN itself may be constituted by a number of different entities such as a local exchange or several interconnected local exchanges, as long as it is capable of providing the required services to the subscriber stations. Nowadays, very sophisticated new service networks are considered to be interfaced to an access network, e.g. via a service network interface such as The European Telecommunications Standards Institute (ETSI) has also compiled general guidelines and recommendations of how such a should be configured within the framework of an access network. Generally and 25 in particular for two versions of the V5-interface (namely the V5.1-interface and the V5.2-interface) ETSI has standardised the signalling protocols and switching procedures for a configuring of the V5-interface with respect to an access network. The following documents may be referred to for further information regarding the V5-interface: reference ETSI: Final Draft prETS 300 376-1: 1994; Signalling Protocols and Switching (SPS); Q3 interface at the Access Network (AN) for configuration management of V5 interfaces and associated user Sports; reference ETSI: DE/SPS-3003.1; Signalling Protocols and Switching; V 6 interfaces at the digital Local Exchange V5.1 interface for the support of Access Network reference ETSI: DE/SPS-3003.2; Signalling Protocols and Switching; V interfaces at the digital Local Exchange V5.2 interface for the support of Access Network and reference

DIAX

Telecommunications: 9402803D011; Operation's Guide; DIAmuX.

Figure 13, which is analogous to figure 12, describes the procedure when setting up a V5-interface between a local exchange LE, SN and an access network AN. Whilst again figure 13a shows the abstract treatment of the access network, figure 13b and figure 13c demonstrate the problem, i.e. that it is necessary to determine, where to terminate the V5-interface on the AN side, i.e.

to identify the access node where the V5-protocol can be interpreted. As is shown in figure 13b, subscribers SS-1, SS-2, SS-3, SS-4 are connected to their respective access node within the access network AN, whilst access nodes AN1, AN2 are indirectly connected to the local exchange LE through access node AN3, 15 which serves as an entry point to the access network. (Such a configuration may be found e.g. in reference Again, the problem, that arises is how to support the services on the network management layer, i.e. how to set up the protocols on the access network (see figure 13a or figure 12a).

S 20 So far, not making any difference between the specific features of the V5.1-interface and the V5.2-interface, generally and as is shown in figure 11, the access network topology can be rather complex and it is not always obvious how S and where the V5-interfaces are to be set up in order to provide services to the subscriber stations. Even if one refers to the latest literature in e.g. reference 25 the standards regarding the problem in figure 13a are rather vague about the definition of the object class "access network", so that presently, there are no clear guidelines available per se as to how the V5-interfaces are to be set up on access networks.

The paper by A. Gillespie, globecom '92 "Interfacing Access Networks to Exchanges: The ETSI V5 Approach" describes the principles of connecting interfaces to access networks, as described for example in references [3] A above. In particular, this paper describes, how a ISDN-service can be terminated in an access node and that the access network does not need to be concerned with the content of the ISDN-signalling for the interconnection. However, the paper also emphasises, that it has not proved possible to map PSTN-signalling and an ISDN-signalling. The reason for this is that the respective messages are performed in different layers. The paper only describes the interchange of signalling between the local exchange and the access network, however, also gives no clear guidelines as to how the access should be performed within the access network.

As is demonstrated in figure 13c, 13d depending on the location of the subscriber requesting the V5-supported service, the access node AN1 within the access network AN is identified to which the subscriber is connected. If can be established on this access node, this node AN1 is used directly to provide the subscriber service. In case of the V5-supported service, this connection will be a single 2Mbit/s line.

15 If the V5-interfaces have, however, not already been established on the access node AN2, the virtual 2Mbit/s connection from the local exchange to the access node AN1 must be set up and configured for the special S signalling protocol. For example, in figure 13e, the subscriber SS-2 has also S* requested a V5-supported service, however, no V5-interface has been set up on its respective access node AN2 in advance. Then, access nodes AN1, AN2 have both been designed to terminate 2Mbit/s connections from local exchanges, but in the case of access node AN1, the 2Mbit/s connection from the local exchange is not terminated in AN1 itself, but rather cross-connected to enable the 2Mbit/s connection to be terminated in access node AN2 (2Mbit/s connections are used 25 between AN1, AN2 (see also reference Therefore, using the access node AN1 as a transport access node and AN2 as the final target access node, it is possible to string a virtual 2Mbit/s connection between the local exchange LE and the access node AN2, such that the V5-interface can be terminated at the access node AN2, thus allowing the subscriber station SS-2 to be provided with services supported by the basic rate ISDN-BA). Of course, if there are more subscribers present as is shown in figure 12d, the situation becomes even worse also for the 8 connections, since individual virtual connections will have to be set up to each target access node. Thus, generally and in particular for the the following disadvantages can be summarised: 1. the abstraction level of the access network AN must be broken, since it is not possible to avoid looking into the access network when setting up the service network interface the 2. the utilisation of the access network resource is not optimal, since the service network interfaces V5-interfaces) will have to be terminated at all access nodes, which connect subscriber stations requiring services, thus requiring virtual connections.

For example, in figure 13e, when two subscriber stations SS-1 and SS-2 both have requested the V5-supported services, e.g. the basic rate ISDN, then invariably two separate 2Mbits connections between the local exchange and the access node AN1 will have to be set up in order to support two different :i 15 V5-interfaces, one terminated at access node AN1 and the other terminated at access node AN2. However, for capacity and resource utilisation reasons, it :i would of course be better to have only one 2Mbits connection set up between the local exchange LE and one of the access nodes within the access network AN in order to simultaneously provide services to both subscribers SS-1 and SS-2.

SUMMARY OF THE INVENTION S* Therefore, it is an object of the present invention to provide an access node, an access network, a telecommunication system and a method for providing services to subscriber stations of an access network, that allow to make optimum use of the capacity and resources of the access network, without 25 destroying the abstraction level of the access network.

With the above object in mind the present invention provides in one aspect an access node for use in an access network to which access network are connected, via a subscriber traffic path and a service network traffic path, respectively, at least one subscriber station and at least one service network, said service network providing services for said at least one subscriber station and said services being transmitted respectively via service communication data on at least two bearer channels and via service signalling data on at least two communication channels, including: a front end translator adapted to interpret a signalling protocol used by said at least one service network and a signalling protocol used on a traffic path between said access node and at least one subscriber station and/or a signalling protocol on a traffic path between said access node and at least one other access node of said access network to establish communication between said service network and said subscriber station and/or said other access node and said front end translator being further adapted to receive/transmit said service communication data on said bearer channels and said service signalling data on said communication channels and being further adapted to transmit/receive said service communication data to/from a transmission/reception means: said transmission/reception means being adapted to transmit/receive said service communication data on said bearer channels and service signalling data on said communication channels of said services to/from said front end translator and being further adapted to broadcast 15 the service signalling data on said communication channels to at least two other access nodes of said access network or to at least one connected subscriber station and at least one other access node or at least two connected subscriber stations via the respective traffic path.

8 Since in the above method, the telecommunication system and the access network, the access nodes are provided with the front end translator and the transmission/reception means, service network interfaces can be terminated on the boundary of complex access network interfaces. This facilitates a flexible and uniform set-up of service network interfaces on access networks, no matter how S: 25 complex their internal topology is. Therefore, the access network can be treated a real black box entity, without any need for looking inside the access network structure, when setting up the service network. It is only necessary to know the very termination point on the termination boundary, that will support the service network interface and only a single line has to be connected to this termination point, whereas still all subscribers connected to the access network can request services from the service network, also simultaneously, if desired. Since no virtual concept is used, access networks configured with such access nodes can be treated as real black boxes to be interconnected to other access networks having the same functionality. Another advantage is, that the same structure may be applied to the service network itself, such that access and service network topology can be mutually interconnected by just interconnecting the black boxes at their termination boundary.

According to a further aspect of the invention, with respect to the access node, preferably said front end translator is adapted for interpreting said signalling protocol of said service network and said signalling protocol of said subscriber stations.

According to another aspect of the invention, with respect to the access node, preferably said front end translator is adapted for terminating a subscriber traffic path having a bandwidth of 2Mbit/s or 64Kbit/s and/or a service network traffic path of 2Mbit/s, if a V5-network interface is used.

According to another aspect) of the invention, with respect to the access 15 node, preferably said transmission/reception means is adapted for receiving simultaneously services from said service network traffic path as a respective :OO- number of separate circuits each having a specific bandwidth.

According to another aspect of the invention, with respect to the access node, preferably said transmission/reception means receives said services on S 20 said circuits and dynamically allocates said services on respective circuits on said i traffic paths connected to said other access nodes and/or subscribers stations.

According to another aspect of the invention, with respect to the access node, preferably said circuits transmitted/received to/from said subscriber stations each occupy 64Kbit/s.

25 According to another aspect of the invention, with respect to the access node, preferably said services provided by said service network for said subscriber stations each occupy one or more of said 64Kbit/s circuits.

According to another aspect of the invention, with respect to the access node, preferably communication data of said services is carried on 64Kbit/s channels on B-channels and signalling data of said services is carried on 16Kbit/s D-channels, if said service is basic rate ISDN.

11 According to another aspect of the invention, with respect to the access node, preferably said transmission/reception means is adapted for switching and routing a respective subset of bearer channels and all of said communication channels to interconnected other access nodes or subscriber stations via said traffic paths.

According to a further aspect of the invention, with respect to the access network, preferably said transmission/reception means also examines said signalling data on said communication channels.

Embodiments of the invention will hereinafter be described with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram that shows the treatment of the access network as a black box having termination points TP on the termination boundary TB according to the invention; p* 15 Figure 2a is a diagram that shows an access node, an access network and a telecommunication system according to a first embodiment of the invention; Figure 2b is a diagram that shows a front end translator FET and a transmission/reception means TR-SR according to the first embodiment of the invention; 20 Figure 3a is a diagram showing an access node, an access network and a telecommunication system according to a second embodiment of the invention; S; Figure 3b is a diagram showing a front end translator FET and a transmission/reception means TR-SR according to a second embodiment of the o invention; Figure 3c is a diagram showing how the subscriber stations SS-1, SS-2 and the service network SN can be connected to an arbitrary termination point according to the second embodiment of the invention; Figure 3d is a diagram showing a termination point port connection list according to the second embodiment of the invention; Figure 4 is a diagram showing the method of providing services to the subscriber stations SS-1, SS-2, SS-4 using a switching and routing of channels in the respective access nodes AN 1, AN2, AN3; Figure 5 is a diagram showing a third embodiment of an access node, an access network and a telecommunication system when setting up a VS-interface on the termination boundary TB; Figure 6a is a diagram showing the broadcast of signalling information for a V5.1-interface set-up, when all subscriber stations SS-1, SS-2, SS-3, SS-4, have respectively requested basic rate ISDN-BA from the local exchange LE, SN; Figure 6b, 6c in combination constitute a flow chart that describes the switching and routing of bearer channels and communication channels according to an embodiment of the method for providing services to subscriber stations, when applied to the V5.1-interface set-up shown in Figure 61; 6a; Figure 7 is a diagram showing the routing of signalling information when all subscriber stations SS request basic rate ISDN-BA from the V5.1-interface; Figure 8 is a diagram showing the switching of bearer channels BC and S 15 communication channels CC at access nodes for a V5.2-interface; Figure 9 is a diagram showing an extended network topology using black box network AN-i, AN-2, SN-1 each being configured as is shown in Figure 1 according to a fourth embodiment of the invention; Figure 10 is a diagram showing the regrouping of networks to form a 20 generalised "black box" network having a new termination boundary TB' fee* according to a fourth embodiment of the invention; 0• Figure 11 is a diagram showing a conventional access network; Figure 12a is a diagram that illustrates the problem with connecting a service network SN to an access network according to Figure 11; 25 Figure 12b is a diagram that shows a fixed set-up connection of the service network to the access node AN1; Figure 12c is a diagram showing the virtual connection concept when both subscribers SS-1, SS-2 have requested services from the service network SN; Figure 12d is a diagram showing the problems of virtual connection when three subscriber stations have simultaneously requested services from the service network; Figure 13a is a diagram that shows the problem when conventionally setting up a V5-interface on an access. network; Figure 13b is a diagram that shows the interconnection of the local exchange to the access network; Figure 13c is a diagram showing the V5-interface termination at access node AN 1; Figure 13d, 13e are diagrams, that respectively show the interconnection and cross-linking of the V5-interface when one or two subscribers SS-1, SS-2 have simultaneously requested a V5-supported service.

DESCRIPTION OF THE EMBODIMENTS Hereinafter, the same reference symbols as in the above-described Figures 11 to 13 are used for denoting the same or similar parts.

The general concept of the invention is illustrated in Figure 1. As seen in Figure 1, by contrast e.g. to Figure 12b, the service network SN is now terminated 9.

15 on the boundary TB of the access network, no matter how complex the access network may be. The termination boundary includes a number of termination points TP1, TP2, TP3, on which the respective traffic paths TRP1, TRP2, TRP3 i:@j are terminated. If such a concept is used, then the access network can be treated as a real black box. Of course, there must be a "visibility" of termination points on the termination boundary TB, i.e. in a simplest case, where all subscribers have the same signalling format SS-F and the service network SN uses a different signalling format SN-F, the termination points must carry a label or flag that indicates that the service network and the subscriber stations, respectively, can be terminated at the such identified termination point. However, 25 the advantage with this approach is obviously, that no further knowledge about the internal structure of the access network capabilities is necessary.

FIRST EMBODIMENT Figures 2a, 2b generally show the internal functionalities, that will allow this access network to be treated as a real black box. As shown in Figure 2a, an access node AN3 has been identified as supporting the signalling format SN-F of the service network SN. The subscriber stations SS-1, SS-2, SS-4 are respectively terminated on the termination points TP1, TP2, TP4 with their 14 respective traffic paths TRP1, TRP2, TRP4. The termination points are respectively connected with the access nodes ANI, AN2, AN3, wherein it is possible to connect more than one termination point to one access node as is indicated with the dotted lines. For simplicity, the internal connection of the access network nodes is shown as interconnected only with the adjacent access node via a respective traffic path TRP31, TRP21. However, of course, if more access nodes are provided in the access network, the interconnection can be arbitrary, as shown in Figure 11. It should, however, be noted that despite the fact that all subscriber stations SS-1, SS-2, SS-4 can simultaneously request services from the service network SN, there is only one single individual line set up between the switching network SN and the access node AN3 via the termination point TP3.

Figure 2b shows the internal structure of the access nodes according to the first embodiment of the invention. The access node AN3 contains a front end go 15 translator that is capable of interpreting the interface signalling protocol SN-F from the switching network SN (or if necessary, also from an interconnected subscriber station in a termination point TP4). The front end translator FET interprets the signalling format SN-F and provides for the internal signalling format IN-F needed S: to establish communication with the other internal access nodes AN1, AN2. This internal signalling format IN-F can be adjusted according to need. The access S. node AN3 also includes a transmission/reception means TR-SR, that receives goes and transmits the services from the other interconnected access node AN1 (or other connected access nodes or termination points as is shown with the dotted lines). Having configured the access nodes as shown in Figures 2a, 2b, such that 25 they are respectively adapted to interpret the required signalling protocol SS-F, SN-F and include a respective transmission/reception means, services for all interconnected subscriber stations SS-1, SS-2, SS-4 can be simultaneously provided on the single traffic path TRP3, while the access nodes AN3, AN1, AN2 respectively perform a routing and switching of the services. That is, access node AN3 (having set up the service network signalling format on its front end translator FET) receives all services from the service network SN, takes out the required service for the subscriber station SS-4 and switches the rest of the services via traffic path TRP31 to the adjacent access node AN1 (all performed by the transmission/reception means TR-SR).

In turn, the access node AN1 receives the remaining services and route services required by subscriber station SS-1 to subscriber station SS-1, whereas it switches the remaining services to the access node AN2, which in turn routes the services for the subscriber station SS-2 to said subscriber station SS-2.

Relying upon such internal switching and routing functionalities, the access network can be treated as a black box and maintains its abstraction level, as long as the termination point carries a label or indication as to what signalling format can be interpreted at the respective connected access node.

SECOND EMBODIMENT Figures 3a, 3b show essentially a structure similar to the one shown in Figures 2a, 2b, however, the access nodes AN1, AN2, AN3 each have the capability of interpreting all signalling formats SS-F, SN-F. As shown in Figure 15 3b, the front end translator according to the second embodiment is now oo

*S

0 configured so as to interpret both signalling formats SN-F, SS-F and to convert it into an internal signalling format IN-F. The switching and routing capabilities of °.to the transmission/reception means are equivalent to those in Figures 2a, 2b. In an access network having access nodes as is shown in Figure 3a, however, there is no need for the termination points to carry a specific indication as to what :00 signalling format can be interpreted.

o0 0. This means, as is shown in Figure 3c, there is a complete black box treatment of the access network, meaning that the subscriber stations SS-1, SS-2 and the service network SN, can be connected arbitrarily to any termination point 0°o 25 TP1, TP2, TP3 on the termination boundary TB (schematically shown with the dotted line in Figure 3c). Of course, in general each subscriber station SS-1, SS-2 can even use a different signalling format SS-F or can even be adapted to use one of a plurality of signalling formats SS-F. Likewise, the service network may be configured to use one or several ones of signalling formats. In accordance therewith, the front end translator is adapted to respectively include the signalling formats that are used by the service network and the subscriber stations.

16 As is shown in Figure 3d, the termination point, i.e. the physical port of the (abstract) termination boundary TB can carry a termination point port connection list TPCL indicating which kind of protocols are available at this termination point.

However, in any case, with the switching and routing functions of the individual access nodes AN1, AN2, AN3, it is not required to possess any knowledge about the internal structure of the access network.

Figure 4 shows a method of switching and routing the individual services, something that is carried out by the transmission/reception means in each access node. In figure 4, it is assumed (as in Figure 3a) that the access nodes only support the respective signalling format required by the connected subscriber station SS-1, SS-2 and the service network SN, respectively.

As already indicated in Figure 3a, there is one connection between the service network SN and the access node AN3, that will support a specific bandwidth of x Mbit/s. This bandwidth is capable of supporting a number of circuits (circuits in this connection is to be regarded as an individual interconnection between the service network and the subscriber having requested a service, e.g. the entire route from SN to SS-2 via AN3-AN1-AN2 in Figure 4), e.g. consisting of channels of specific bandwidths n 4 n 2 nc as is indicated in Figure 4. Naturally, the termination point TP3 will be able to support this 20 bandwidth. The services respectively to be provided to the subscriber stations will each be transmitted on one or more channels SS-1 CH, SS-4 CH, SS-2 CH.

Also necessary are of course one or more channels C-CH for the communication data, i.e. the exchange of signalling information.

:lO: In Figure 4, the subscriber station SS-1 has as an example requested a 25 service that requires three channels, the subscriber station SS-2 has requested a service requiring two channels and the subscriber station SS-4 has requested a service requiring only one channel. In this case, the termination points TP4, TP1, TP2 will respectively be adapted to support at least the required bandwidth as is indicated in Figure 4. Since in Figure 4 two communication channels C-CH are used, two communication channels will be switched and routed up to the access node AN2 through the access node AN1. Therefore, the indicated traffic paths 17 TRP31, TRP12 respectively have the minimum bandwidth indicated in Figure 4.

Of course, they can provide a larger bandwidth.

Whilst generally, bearer channels SS-1 CH, SS-4 CH, SS-2 CH and C CH of deferring bandwidth can be used in a time division multiplexing method, these channels are usually of an equal bandwidth. It is not necessary to provide a specific fixed time relationship between the input channels on the input traffic path to the access node AN3 and the respective internal traffic path TRP31 or the traffic path to the termination point TP4, as long as the access node AN3 performs the necessary switching and routing of the correct channels, that originate from the service network. This means, the access node AN3 dynamically selects and allocates the channels from its input to its output traffic path. Likewise, the access nodes AN1, AN2 will perform the dynamic allocation of channels, until all service channels are respectively routed to the subscriber station having requested services from the service network.

The advantage of using a transmission/reception means for switching and routing of the individual channels will thus ensure, that the abstraction level of the access network is not destroyed; namely, there is neither a need to identify the specific access node, which is connected to the very subscriber station, that requires services, nor is there any necessity to string up virtual connections.

20 Therefore, one single connection line between the service network and the respective access node (capable of interpreting the service network interface protocol) is sufficient and nevertheless, all subscriber stations can be provided with services, provided the total bandwidth of required channels does not exceed 2 the bandwidth of the traffic path between the switching network and the o* 6 respective access node.

THIRD EMBODIMENT Whilst the above-proposed solution is very general and is not related to the usage of any specific interface or protocol format, in the following it will be described, how the problems with setting up a VS-interface (see Figures 12, 13 discussed above) can be solved by using a concept as shown with Figures 1 to 4.

Again, in Figure 5, the VS-interface is terminated on the boundary of the access network AN, while the access nodes AN1 to AN4 have the special 18 functionalities as described with reference to Figures 1 to 4. The V5-interface is terminated on the termination point TP6 using a 2Mbit/s bandwidth. Of course, again all 2Mbit/s access node termination points interfacing towards the service network are visible on the termination boundary TB of the access network AN.

Visibility again means (as was discussed with reference to Figures 1, that it is known, which access node or which front end translator is capable of interpreting the V5-interface protocol. Looking at Figure 5, this means, that all SN interfacing 2Mbit/s termination points of access node AN1 (the entry access node into the access network) will be known outside the access network. Likewise, this comment applies to all other termination points TP1, TP2, TP3, TP4, TP5 (which may be regarded as the exit nodes for the access network with respect to the provision of services to the subscriber stations) and also such termination points that interface to other access networks (see Figure All descriptions made for the termination points TP1 -TP6 interfacing to subscribers SS-1 to SS-5 and to the local exchange LE in Figure 5 therefore only apply in a similar range manner to such termination points, that interface to another access network AN-2 or a service network SN-1 in Figure 9 As already discussed in Figure 4, the traffic paths between the individual subscriber stations SS-1, SS-2, SS-3, SS-4, SS-5 support the minimum 20 bandwidth required for the respective service (n x 64Kbit/s). When leased lines from other companies are used, these traffic paths can of course also support 2Mbit/s, since leased lines are only charged for the time period, during which they are occupied by data. For illustration purpose, again the access nodes AN1 to AN4 are only as an example interconnected to one adjacent access node, whilst the general interconnection configuration may be taken from Figure 11.

Using the service network interfacing 2Mbit/s termination points TP on the termination boundary TB, the service network may now be interfaced in a conventional way. In Figure 5, this means that the VS-interface is in fact terminated again at the access node AN1, however, this is transparent outside the access node.

In the following, the switching and routing of channels will be described for the V5.1 and V5.2-interfaces, however, the switching and routing is similar in as much both enable the access networks to be treated as black boxes when the are set up.

V5.1-SOLUTION In Figure 6a, the V5.1-interface is terminated at a respective termination point TP6 on the boundary, which is in turn connected to the entry access node AN1. As an example, all subscriber stations are assumed to have requested basic rate ISDN-services at their premises. Each such service to be provided to the respective subscriber station will in this case require two bearer channels BC (carrying the payload data as the channels SS-1 CH, SS-4 CH, SS-2 CH in Figure 4) of e.g. 64Kbit/s on B-channels) and two communication channels CC (carrying the signalling information as the channels C-CH in Figure 4) e.g.

each occupying 16Kbit/s D-channel). The communication channels and the bearer channels are respectively denoted with CC, BC in Figure 6a.

If 5 subscriber stations simultaneously request the basic rate ISDN, then there will be needed 10 bearer channels and 2 communication channels wherein the communication channels are used for the exchange of signalling information and the bearer channels will carry the communication data for the service. In total, the required bandwidth in this case would be 10 x 64Kbit/s 2 x 64Kbit/s 768Kbit/s, which can easily be supported on the termination point of 2Mbit/s 20 where the V5.1-interface is terminated (in a V5-interface the communication channel bandwidth is 64Kbit/s).

In fact, the V5-interface uses n x 31 bearer channels of 64Kbit/s amounting e.g. to a bandwidth of 1984 Kbit/s (for a V5.1-interface which can fully be supported on the said termination point. Whilst the number of bearer channels 25 10 for 5 subscriber stations) is fixed and dependent on the chosen V5.1-interface configuration, 1, 2 or 3 64Kbit/s communication channels for signalling can be used. In figure 6a, two communication channels CC are used.

With reference to Figure 6b, 6c, which together show a flow chart relating to the switching and broadcasting of channels in Figure 6a, the method of providing services to each subscriber station in a V5.1-interface configuration will be described. First, the service network (here one local exchange LE) is Sconnected to the termination point TP6 via the network interface in step S2 after starting the procedure in step S1. In the connection step S2, the front end translator FET of the access node AN1 will set up a signalling format or protocol used by the V5.1-interface. In step S3, all subscriber stations request the service. Therefore, in step S4, the 10 64Kbit/s bearer channels CC and (in the illustrated case) two communication channels CC are allocated and subsequently transmitted to the access node AN1 in step In step S6, it is determined, whether or not the subscriber station SS-1 has requested a service and if so, the access node AN1 will use this information to support, i.e. to switch and route the ISDN-service to subscriber SS-1; namely, access node AN1 takes out two bearer channels BC in step S7, i.e. it allocates the incoming channels to channels on the traffic path between AN1 and subscriber station SS-1. Now, in step S8, the subscriber station SS-1 can use the ISDN-service, wherein there will be a transmission/reception of data on the two bearer channels.

When in step S9 it is detected in node AN1, that also the subscriber station has requested an ISDN-service, then in steps S10, S11, S12 again two bearer channels for the subscriber stations SS-5 are taken out and the two communication channels are again used for signalling. AN4 in step 11 transmits the two bearer channels BC to subscriber station SS-5 after having received also 20 the two communication channels. The remaining channels (in this case 6 bearer channels and 2 communication channels) are then transmitted to the access node AN2 in step S13.

Access node AN2 will in turn check whether subscriber station SS-2 has made an ISDN-request in step S14 and if so, again two bearer channels BC are 25 taken out and the transmission/reception takes place in steps S15, S16. The remaining channels (now 4 bearer channels and 2 communication channels) are transmitted to access node AN3 in step S17, which in step S18, S21 performs an examination as to whether the subscriber stations SS-3, SS-4 have requested the ISDN-service. If this is so, again the taking-out of channels and the transmission/ reception takes place in steps S19, S20 (for subscriber station SS-3) and in steps S22, S23 (for subscriber station SS-4), before the procedure comes to an end in step S24.

Thus, whilst all services are provided on the V5.1-interface, there is a selection and transmission of bearer channels in the internal structure of the access network until the last subscriber station having requested service has been provided with the requested service. By doing so, it is ensured that the bearer channels arrive at their proper destination.

The signalling information on the communication channels is required by the access nodes to support the subscriber services. In figure 6a, access node AN1 is obviously aware of two communication channels on the V5.1-interface.

These two communication channels contain the complete signalling information that is required by all subscriber services on the V5.1-interface. The access node AN1 has therefore the choice of either examining the signalling information and "route" it to the concerned access nodes AN2, AN4 (see Figure 7) or to "broadcast" it to access nodes AN2, AN4 as was done in Figure 6a. In doing so, access node AN2 will in turn broadcast the signalling information to access node AN3. This way all access nodes within the access network will receive the very same signalling information, although parts or all of this information may not apply to them. However, it is ensured that all access nodes will receive their required signalling information via the two communication channels CC used for this e signalling information.

0 be 20 As indicated in Figure 6a, the broadcast of signalling information is indeed feasible for most practical applications, however, it can have the undesired effect of signalling information taking up too many time slot channels on the signalling paths between the individual access nodes. As seen in Figure 6a, the two communication channels CC are always broadcast to the adjacent access node, 25 despite this access node might not need the complete signalling information. This increases the bandwidth requirements.

i Figure 7 uses the principle of having the access nodes examine the received signalling information on the communication channels CC and then only to route it to the concerned access nodes. That is, the access node AN1 will examine, which signalling information is needed by access node AN4 and perform the routing of this channel only, whilst the remaining communication .channel is routed to the other access node AN2. Therefore, in this case, the steps S6, S7; S9, S10; S14, S15; S18, S19; S21, S22 in Figures 6b, 6c are appropriately altered, so as to include the examination of the communication channel and only route to the respective access node such signalling information, that is required there.

V5.2-SOLUTION Setting up a V5.2-interface on the access network is not intrinsically different from the V5.1-case. However, rather than using a fixed allocation of time slots on the bandwidth, the V5.2-interface uses a dynamic time slot allocation (see references to and thus, in this case, the access nodes are expected to support more advanced transmission/reception capabilities in order to ensure that all bearer and signalling data arrive at their proper destinations in the access network, i.e. at the respective access nodes. Dynamic allocation of time slots in this connection means that the access nodes cannot rely upon the individual channels always having the same slot position in the bandwidth.

As in the V5.1-case, the V5.2-interface will be terminated at a termination point TP6, i.e. at access node AN1 (see Figure Now, since the V5.2-interface uses a dynamic time slot allocation, access node AN1 will have to examine its received signalling information on the communication channels CC in order to co0o route the bearer and signalling data appropriately to the other access nodes AN2, S 20 AN4.

(andIn this case and is schematically shown in Figure 8, the access node AN1 and also the access nodes AN2, AN3) will have to examine the signalling information for the communication channels CC in order to determine, which ones 0*09 to route to access node AN4 and AN2 (in the case of access node AN1). Thus, the access nodes incorporate a switch, that can examine the received signalling information on the communication channels, select free channels on the aggregate and tributary side for data transmission and then connect these channels dynamically. This way, bearer and signalling data will be routed to their proper destination in the access network, much like in the V5.1-case as illustrated in Figures 6, 7. Whilst of course the examining of signalling information in this way is more complicated than the mere routing or broadcasting of signalling information (as in Figures 6, the advantage of such a dynamic time slot channel allocation is also that there will be no fixed relationship described on each of the signalling paths between the individual access nodes AN1 AN2, AN2 AN3, AN1 AN4.

Whilst in Figures 6, 7, 8, the routing and switching of channels has been described for an illustrative example with reference to the V5-interface, it should be noted that this concept is generally applicable to any service network interface, as long as it provides its services on a time slot channel basis, obtainable e.g.

through a TDM-method or other channel multiplexing method.

FOURTH EMBODIMENT For each of the V5.1-interfaces and V5.2-interfaces, a solution has been presented above for treating the access network as a complete black box as was described with reference to Figure 1. As long as the internal access nodes have the special switching, routing or broadcast capability in combination with the interpreting of the signalling format, this allows a flexible set-up of on complex access network topologies.

Thus, the abstract level of the access network is not broken, since the interfaces can be set up without looking into the access network. This will facilitate a higher abstraction level for network management. The utilisation of the access network resources is optimal, i.e. bearer and signalling information will 20 only take up channels on a minimum set of 2Mbit/s transmission resources.

S: The treatment of access networks including access nodes as described above, will allow telecommunication systems to be flexibly set up, as is shown in Figure 9. As long as the abstraction level of the respective networks are not tll: 2 broken, the access networks or service networks can be interconnected freely and flexibly, without looking into the internal structure of the access network itself.

9 9 All that is required is, that the termination point on the boundary will support the signalling format used by the respective interconnected other network.

This principle can even be extended further as is shown in Figure Here, a number of general access networks AN-i', AN-2', AN-3'(each having an internal structure of access nodes as described above) are again interconnected, leading to a new generalised "black box" network with a new termination boundary TB'. Thus, the access networks AN-i', AN-2', AN-3' behave, as if they were access nodes within one single access network the one denoted with AN-1 Such a flexible set-up is possible, since the respective basic units of access nodes support the functionality as described above, i.e.

such that the access networks can be treated as real black boxes with no breaking of the abstraction level.

Reference numerals in the claims only serve illustration purposes and do not limit the scope of these claims.

"Comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

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Claims (10)

1. An access node for use in an access network to which access network are connected, via a subscriber traffic path and a service network traffic path, respectively, at least one subscriber station and at least one service network, said service network providing services for said at least one subscriber station and said services being transmitted respectively via service communication data on at least two bearer channels and via service signalling data on at least two communication channels, including: a) a front end translator adapted to interpret a signalling protocol used by said at least one service network and a signalling protocol used on a traffic path between said access node and at least one subscriber station and/or a signalling protocol on a traffic path between said access node and at least one other access node of said access network to establish communication between said service network and said subscriber station and/or said other access node and said front end translator being further adapted to receive/transmit said service communication data on said bearer channels and said service signalling data on said communication channels and being further adapted to transmit/receive said service communication data to/from a transmission/reception means; b) said transmission/reception means being adapted to transmit/receive said service communication data on said bearer channels and service signalling data on said communication channels of said services to/from said front end translator and being further adapted to broadcast the service signalling data on said communication channels to at least two other access nodes of said access network or to at least on connected subscriber station and a least one other access node or at least two connected subscriber stations via the respective traffic path.

2. An access node according to claim 1, wherein said front end translator is adapted for interpreting' said signalling protocol of said service network and said signalling protocol of said subscriber stations.

3. An access node according to claim 1, wherein said front end translator is adapted for terminating a subscriber traffic path having a bandwidth of 2Mbit/s or 64Kbit/s and/or a service network traffic path of 2Mbit/s, it a V5-network interface is used.

4. An access node according to claim 1, wherein said transmission/reception means is adapted for receiving simultaneously services from said service network traffic path as a respective number of separate circuits each having a specific bandwidth. An access node according to claim 4, wherein said transmission/reception means receives said services on said circuits and dynamically allocates said services on respective circuits on said traffic paths connected to said other access nodes and/or subscribers stations. coco

6. An access node according to claim 4, wherein S•-said transmission/reception means receives said services on said circuits and dynamically allocates said services on respective circuits on said traffic paths connected to said other access nodes and/or subscribers stations and; S and;said circuits transmitted/received to/from said subscriber stations each ,oct• occupy 64Kbit/s.

7. Access node according to claim 6, wherein i said services provided by said network for said subscriber stations each occupy one or more of said 64Kbit/s circuits.

8. Access node according to claim 1, wherein 27 communication data of said services is carried on 64Kbit/s channels on B- channels and signalling data of said services is carried on 16Kbit/s D- channels, if said service is basic rate ISDN.

9. Access node according to claim 1, wherein said transmission/reception means is adapted for switching and routing a respective subset of bearer channels and all of said communication channels to interconnected other access nodes or subscriber stations via said traffic paths. Access node according to claim 1, wherein said transmission/reception means also examines said signalling data on said communication channels.

11. An access node as claimed in claim 1 substantially as herein before described with reference to the accompanying drawings. DATED this 18th day of August 2000 TELEFONAKTIEBOLAGET L M ERICSSON WATERMARK PATENT TRADEMARK ATTORNEYS UNIT 1, THE VILLAGE RIVERSIDE CORPORATE PARK

39-117 DELHI ROAD NORTH RYDE NSW 2113 t o*