WO2000051295A1

WO2000051295A1 - Method and system for setting up a call

Info

Publication number: WO2000051295A1
Application number: PCT/FI2000/000154
Authority: WO
Inventors: Reijo Romppanen; Martti YRJÄNÄ
Original assignee: Nokia Networks Oy
Priority date: 1999-02-25
Filing date: 2000-02-25
Publication date: 2000-08-31
Also published as: FI108199B; FI990410A0; AU3167800A; FI990410A

Abstract

The invention concerns a method and system for queueing up for resources in a telecommunication system comprising a local exchange (LE), an access node (AN), a concentrating V5 interface (V5) connecting the access node to the local exchange. In addition, subscribers are connected to the access node via a concentrating interface (RSSI), so its resources may become a problem when calls are to be set up. In an embodiment, the access node is given a command from the local exchange to wait for the release of resources in the concentrating interface in the event of congestion in the latter. This makes it possible to avoid call setup failures if resources are released in the concentrating interface within a relatively short predetermined queueing-up time. This improves the service that subscribers receive from the operator.

Description

METHOD AND SYSTEM FOR SETTING UP A CALL

FIELD OF THE INVENTION

The present invention relates to telecommuni- cation systems. In particular, the invention concerns a new type of method and system for queueing up for resources in an access node in an overload situation in a concentrating interface in an access network.

BACKGROUND OF THE INVENTION

Open interfaces (V5.1 and V5.2) between an access network and a telephone exchange are defined in the ETSI (European Telecommunications and Standards Institute) standards of the ETS 300 324 and ETS 300 347 series. V5 interfaces enable subscribers belonging to a physically separate access network to be connected to a telephone exchange using a standard interface. A dynamic concentrator interface V5.2 defined by the ETS 300 347-1 and 347-2 standards consists of one or more (1 - 16) PCM (Pulse Code Modulation) lines. One PCM line comprises 32 channels or time slots, each of which has a transfer rate of 64 kbit/s, so the to^¬ tal capacity of the PCM line is 2048 kbit/s. The V5.2 interface supports analogue telephones as used in the public telephone network, digital, such as ISDN (Integrated Services Digital Network) basic rate and primary rate interfaces as well as other analogue or digital terminal equipment based on semi-fixed connections . 'WLL system' (WL , Wireless Local Loop) means a system in which the subscriber is connected to a telephone network via a wireless communication system. A subscriber interface is created using a special telecommunication terminal. In principle, the telecom- munication terminal functions like a mobile station known in itself, but its operating range can be lim- ited to a given mobility area. The wireless communication system can be implemented using mobile communication technology, e.g. GSM technology (GSM, Global System for Mobile communications) . The wireless communi- cation system is generally connected to the access node of an access network. Via the access node, the wireless communication system is further connected to a telephone exchange.

The access node may comprise both scanned re- sources and dynamically allocated resources. Subscribers can be connected to the access node via a remote subscriber stage (RSS) , in which case subscribers to be connected to the access node are concentrated on the modular line between the remote subscriber stage and the access node. Moreover, as stated above, subscribers can be connected to the access node via a wireless communication system, in which case subscribers can be concentrated in the interface between the access node and the radio network. 'Concentrating' here means in practice that not all subscribers can simultaneously communicate with the access node, but the capacity is only sufficient for a proportion of them.

If all the resources in the concentrating modular line or radio system are busy, then the problem is how to ensure successful setup of special priority calls. When a call is being set up from a local exchange to an access node or vice versa, the local exchange selects the V5.2 interface link to be used and a suitable time slot in that link. The BCC protocol defined by the V5 standard gives link and time slot information to the access node so that the call can be set up. In the case of an outgoing call, i.e. when a call from the access node to the local exchange is to be set up, the call may fail because of a lack of resources due to overload in the interface between the access node and the subscribers connected to it . In practice, the A-party does not get a dial tone because the subscriber cannot even be connected to the access node. In this case, the BCC protocol at the access node gives a negative response to the link and time slot allocation message sent by the local exchange. A corresponding problem is encountered in the case of a call terminating at the access node. This problem appears especially during crises when subscribers try to set up calls simultaneously and the V5 signalling channels are overloaded, with the result that many call attempts fail .

OBJECT OF THE INVENTION

The object of the invention is to eliminate the problems described above. A specific object of the invention is to disclose a new feature to be implemented in the V5.2 interface so that a queueing property can be provided for a certain type of priority calls to ensure their successful setup. A further object of the invention is to disclose a method that allows the operator or other main- tainer of a telephone network to allocate call resources for desired calls or subscribers.

An additional object of the invention is to disclose a system designed to implement the above- mentioned method.

The invention is characterized by what is presented in the claims.

SUBJECT OF THE INVENTION

The present application describes a new and innovative solution for queueing up for resources in a telecommunication system comprising a local exchange, an access node, a concentrating interface, such as a remote subscriber stage or radio network interface for connecting subscribers to the access node and a con- centrating V5 interface for connecting the access node to the local exchange. In the invention, subscribers are connected via a concentrating interface to the access node and further to the local exchange. According to the invention, information indicating the priority category of each call is sent from the local exchange to the access node and, based on it, the call is queued to wait for call resources in the concentrating interface, i.e. in the interface be- tween the access node and the remote subscriber stage or radio network interface, in the event of congestion in it .

The local exchange may send the access node notice of a predetermined queueing-up time for which the access node is to wait for call resources. The queueing-up time can be monitored by starting a special time-out in the access node and, after the timeout period has expired, the local exchange is informed that the call has failed. Likewise, if call resources are released before the time-out expires, then the local exchange is given a normal acknowledgement of the call setup request.

The priority category of each subscriber port can be stored in the access node separately, which means that certain subscribers can be given a special priority. The local exchange can interrupt the queueing-up for resources before the time-out has expired.

The system of the invention for queuing up for resources in a telecommunication system comprises means for giving call-specific call priority information from the local exchange to the access node and means for queueing up for call resources in the event of congestion in a concentrating interface. Moreover, the system may comprise a timer for determining and measuring the time spent queueing up for resources. In addition, the access node preferably comprises means for storing the priority category of each subscriber port separately.

As compared with prior art, the present invention provides the advantage that the service re- ceived by subscribers connected to an access node via a concentrating interface is improved. In practice, this means that, in crises and other situations where it is absolutely necessary to be able to set up a call, the probability of successful setup of a prior- ity call can be improved.

Moreover, the invention is applicable to both terminating and outgoing calls and is therefore quite useful .

The invention is also particularly useful when both the local exchange and the access node are products manufactured by the applicant; for instance, the local exchange is a DX200 telephone exchange and the access node is a Daxnode5000.

LIST OF ILLUSTRATIONS

In the following, the invention will be described by the aid of preferred embodiments with reference to the attached drawing, in which

Fig. 1 presents a telecommunication system according to the invention,

Fig. 2 presents a signalling diagram in a preferred embodiment of the present invention,

Fig. 3 presents a flow diagram of a procedure according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 presents an example of a system in which the invention can be implemented. The system comprises a first local exchange LEI and a second lo- cal exchange LE2. The local exchange may be e.g. a

DX200 telephone exchange manufactured by the appli- cant. In addition, the system comprises an access node AN, which is connected to the local exchanges LEI and LE2 via a V5.2 interface V5.2. The access node is preferably a Daxnode5000 manufactured by the appli- cant. The figure shows here interfaces V51 and V52. The functionality of these interfaces and this V5.2 interface are described in detail in the above- mentioned standard series ETS 300 347, which is included here by this reference. The system presented in Fig. 1 further comprises a remote subscriber stage RSS, which is connected via a concentrating interface RSSI to the access node. The concentrating interface may consist of e.g. a single PCM line. Connected to the remote subscriber stage are subscribers, in this example a PSTN subscriber SI and an ISDN subscriber S2. Although not presented here, it is obvious that the telephone network may consist of a considerably larger system than that presented in Fig. 1. The network may comprise several exchanges, access nodes and other network components.

Fig. 1 also presents some details of a part of the functional structure of the V5 interface. The BCC protocol 1 allocates and deallocates the resources, such as the time slots, to be used for the call in the V5.2 interface. In practice, the BCC protocol thus manages the use of resources in the concentrating V5 interface. In this invention, the BCC protocol is further used in that it is complemented with an additional feature which is used to transmit infor- mation regarding the call priority category from the local exchange to the access node AN in conjunction with allocation. This feature is implemented using means 1 as provided by the invention. Correspondingly, the BCC protocol in the access node comprises means 2 for queueing up for call resources in the concentrating interface RSSI . The access node additionally comprises a timer 3 for measuring the time assigned by the local exchange LE for queueing up for call resources .

Fig. 2 presents a signalling scheme according to the invention in a case where a PSTN subscriber SI (Fig. 1) initiates call setup. When the PSTN subscriber SI picks up the receiver, the PSTN protocol in the V5.2 interface sends an ESTABLISH message, arrow 21, from the access node to the local exchange. If the calling party were an ISDN subscriber, the procedure would be similar except that the activation message would be transmitted in the Control protocol . The local exchange performs a priority category analysis on the subscriber and, based on the analysis, advises the BCC protocol in the local exchange LE about the length of possible queueing-up time. In the priority category analysis, the local exchange establishes the subscriber priority category e.g. from subscriber information. Based on the priority category, the local exchange estimates the queueing-up time to be assigned for the subscriber in the situation in question. The BCC protocol at the local exchange end of the interface may also have to wait for a call resource in the V5.2 interface. Having obtained the resources, the local exchange sends an allocation message, arrow 22, containing the queueing-up time (time) to the access node. In the access node AN, the BCC protocol object receives the allocation message and the queueing-up time is stored in the access node specifically for the subscriber port concerned. The access node waits for a call resource in the concentrating interface RSSI for the length of time (time) defined in the allocation message if no resource is immediately available. Having obtained a call resource, the BCC protocol sends an acknowledgement of the allocation message, arrow 23, from which the local exchange LE learns that a call resource has been made available to the subscriber for the call. Next, the PSTN protocol at the local exchange LE sends an acknowledgement, arrow 24, of the call setup message first sent by the access node. Let it be further noted that, in the case of an ISDN subscriber S2 (Fig. 1), although not described here, the procedure is mainly the same, only the PSTN protocol is replaced by the Control protocol.

Fig. 3 presents a flow diagram representing a preferred embodiment of the invention. When the subscriber picks up the receiver, a notice is sent to the local exchange LE, block 31. Based on the notice, allocation of resources in the V5.2 interface is started, block 32. If a call resource is obtained in the V5.2 interface, then a priority category analysis is performed, block 33. This will indicate whether the access node is to be given an instruction to queue up for a resource in the concentrating interface RSSI. In block 34, a check is carried out to establish whether a priority has been defined for the subscriber.

If the subscriber is not entitled to priority calls, the procedure will go on to block 36, in which case the allocation message sent from the local exchange LE to the access node AN contains no information relating to queueing-up time, and the only function to be performed in block 36 is to check whether there are any free call resources available in the concentrating interface. If there are not, then the call is disconnected, block 38. If there are, then normal call setup is continued, block 37.

If it was established in block 34 that the subscriber is entitled to priority calls, then an allocation message giving a queueing-up time is sent from the local exchange LE to the access node AN, block 35. After this, a time-out is started in the access node, block 39. The procedure then goes on to block 40, where a check is performed to see whether there are any resources available in the concentrating interface. If there are, then the procedure goes on to block 41 and normal call setup is continued. If no resources are available, then the procedure goes on to block 42, where the state of the time-out is checked. If the time-out has been tripped, then the procedure will go on to block 43 and the call is disconnected. If the time-out has not been tripped, then the procedure will return to block 40 and go on waiting for resources being released. After the time-out period has finally expired, the call is disconnected. The invention is not restricted to the example embodiment described above, but many variations are possible within the scope of the inventive idea defined in the claims .

Claims

1. Method for queueing up for resources in a telecommunication system comprising a local exchange (LE) , an access node (AN) and a concentrating V5 in- terface connecting the access node to the local exchange, in which method the subscriber is connected to the access node via a concentrating interface (RSSI) , characterized in that the method comprises the steps of: sending from the local exchange to the access node information indicating the priority category of the call, and queueing up for call resources in the concentrating interface (RSSI) in the event of congestion in said interface.

2. Method as defined in claim 1, characterized in that the local exchange advises the access node about the queueing-up time to be spent queueing up for call resources.

3. Method as defined in claim 1 or 2 , characterized in that a time-out is started to monitor the queueing-up time.

4. Method as defined in any one of claims 1 - 3, characterized in that the access node (AN) informs the local exchange (LE) about release of resources, whereupon normal call setup is continued.

5. Method as defined in any one of the preceding claims 1 - 4, characterized in that, if the queueing-up time expires, then the queueing is inter- rupted and the call is disconnected.

6. Method as defined in any one of the preceding claims 1 - 5, characterized in that the access node (AN) stores the priority category separately for each subscriber port .

7. System for queueing up for resources in a telecommunication system comprising a local exchange (LE) , an access node (AN) and a concentrating V5 in- terface connecting the access node to the local exchange, the subscriber being connected to the access node via a concentrating interface (RSSI), characterized in that the system comprises: means (1) for sending from the local exchange to the access node information indicating the priority category of the call; and means (2) for queueing up for call resources in the concentrating interface (RSSI) in the event of congestion in said interface.

8. System as defined in claim 7, characterized in that the system comprises means (3) for advising the access node (AN) about the queueing-up time to be spent waiting for the release of call resources in the concentrating interface.

9. System as defined in claim 7 or 8 , characterized in that the system comprises a timer (4) for monitoring the lapse of the queueing-up time.

10. System as defined in any one of the pre- ceding claims 7 - 9, characterized in that the access node (AN) comprises a storage device (5) for storing the priority category for each subscriber port .