GB2270814A - Provision of analogue telephone exchange supplementary services - Google Patents

Abstract

An automatic telecommunications system includes one or more analogue exchanges, such as a TXE 4 exchange with a switching network 1, and at least one digital exchange 3, such as a System X exchange, there being PCM transmission links therebetween. In order to provide supplementary services to analogue exchange subscribers, a processing means (20) having supplementary services call handling processes is located at the digital exchange(s) and may be shared between a number of analogue exchanges. Signalling messages relating to the supplementary services employ a protocol different to that employed for call supervision and call establishment and are transmitted between the processing means (20) and the analogue exchange(s) in spare signalling channels of the PCM transmission links. The processing means may be based on a DMS compute module. <IMAGE>

Description

ANALOGUE TELEPHONE EXCHANGE SUPPLEMENTARY SERVICES This invention relates to automatic telecommunications systems and to the provision of supplementary services for telephone subscribers, in particular for those subscribers still served by analogue exchanges (switches).

Analogue exchanges still feature to a great extent in the British network (British Telecom) and in many other countries.

Supplementary services are however currently only available where there are digital exchanges. Supplementary services include, for example, call diversion, advise duration and charge, call restriction (barring), repeat last number dialled, abbreviated dialling service, call waiting, third party services, reminder calls. An example of such an analogue exchange is that manufactured by Northern Telecom Europe Limited and basically designated TXE 4. The original TXE 4 exchange was for a totally analogue network and did not provide any supplementary services at all but an enhanced version is able to provide call logging and itemised billing.

It is an object of the present invention to further enhance such an analogue exchange so that it can also provide the supplementary services available with digital exchanges.

According to one aspect of the present invention there is provided an automatic telecommunications system including one or more analogue telephone exchanges and at least one digital telephone exchange, wherein the analogue exchanges are connected with the digital exchange by PCM transmission links having common channel signalling capabilities, wherein to provide subscribers to the analogue exchanges with supplementary services a processing means having supplementary services call handling processes is located at a said digital telephone exchange, connected to at least one said analogue telephone exchange, by said PCM transmission links and connected to said digital exchange, and wherein signalling messages relating to the supplementary services are carried between said processing means and the analogue exchange in spare signalling channels of said PCM transmission links.

According to another aspect of the present invention there is provided a digital telephone exchange adapted to provide several analogue telephone exchanges with supplementary services normally unavailable thereto, the digital exchange having a processing means with supplementary services call handling processes located thereat and wherein in use the digital exchange is connected to the analogue exchanges by PCM transmission links having common channel signalling capabilities and signalling messages relating to the supplementary services are carried between said processing means and the analogue exchanges in spare signalling channels of said PCM transmission links.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 illustrates schematically an architecture with a conventional TXE 4 analogue exchange connected to a DMSU (Digital Main Switching Unit); Fig. 2 a modified architecture according to an embodiment of the present invention which enables the TXE 4 analogue exchange to provide supplementary services, Fig. 3 illustrates message flow between the TXE 4 exchange and the DMS-AP (Adjunct Processor), Fig. 4 illustrates OAdcM (Operations Administration and Maintenance) for the DMS-AP via a local MAP (Maintenance and Administration Position) terminal or through a TXE 4 MMI (Man Machine Interface) terminal (via the ACP (Adjunct Communications Protocol) link).

The basic architecture illustrated in Fig. 1 comprises an analogue Switch 1 (TXE 4 for example) with a main control unit 1' which is a call establishment control unit connected to a plurality of subscribers via line terminations 2 and to a remote DMSU 3, for example a System X switch, or alternatively a remote DCCE (Digital Cell Centre Exchange) network node. In order to provide call logging and itemised billing the TXE 4 switch was enhanced. Interworking between analogue and digital exchanges involves signalling between them and in the case of the enhanced TXE 4 analogue exchange this results in the arrangement illustrated schematically in Fig. 1. The analogue exchanges may already be connected to 30 channel PCM PMUX equipment and thus involve channel associated signalling (call supervision).For the interworking between analogue and digital exchanges this must be replaced by common channel signalling i.e. common channel signalling messages have to be inserted into and extracted from the slot 16 (TS16) of the multiplex in place of existing channel associated signalling. This is achieved in the manner described in GB2144601A (G Harland 15) by use of an interface unit, comprised in Fig. 1 by Channel Extractor Inserter (CXI)13. Other elements in Fig. 1 include an interface 4 whereby an SCH 5 (Set-up Call Handler), a CMH 6 (Call Monitor Handler), an SMF 7 (System Manager Facility), a CDF 8 (Charge Determination Facility) and a CCF 9 (Common Channel Facility), which are interconnected by an Ethernet LAN 10, are connected to the Switch 1.The analogue junctions 11 are connected by 2-wire analogue links to a PMUX 12 (Primary Rate (2Mbit/s) Multiplexer), which is connected to the DMSU 3 via a CXI 13 (Channel Extractor Inserter). The link between the PMUX and the CXI is at 2Mbit/s using CAS (Channel Associated Signalling) whereas that between the CXI and the DMSU is at 2 Mbit/s using CCS No 7 (CCITT Common Channel Signalling System No 7-CC #7). The CAS signalling information (call supervision) on TS16 is extracted by CXIs 13 for use by the CCF. The CCF communicates with a main control unit MCU 1 of the Switch 1 via SCH 5 which passes call establishment information.The CCF assembles these call supervision and call establishment messages and sends them back to the CXI as CC*7 labelled messages which are then transmitted on TS16 to switch 3. Conversely common channel signalling messages from the DMSU are extracted by CXI 13 and separated into call establishment and call supervision signals by CCF 9 and directed to MCU 1' or back to CXI 13 for transmission to PMUX 12 as appropriate.

In order to provide the aforesaid supplementary services according to the embodiment of the invention a number of elements additional to those illustrated in Fig. 1 are required, whilst some elements of Fig. 1 need to be modified. A "simple" approach to providing these supplementary services would involve providing the appropriate memory and processing at each analogue exchange itself, for example by adding an additional element, between the LAN 10 and the Switch 1, providing all the necessary Supplementary Services Functioning. However such an approach is expensive and would still require modification of certain of the existing elements.

According to the embodiment the memory and processing are provided at the DMSU or DCCE network node i.e. remotely of the analogue exchange but shared between a number of such exchanges, for example up to ten. It is proposed to use the Supplementary Services call handling processes already existing within our DMS product (Digital Multiplex System) in particular the DMS core i.e. the DMS Compute Module (CM). This DMS CM element and associated equipment is thus packaged to comprise an Adjunct Processor (AP) and is referred to as the DMS-AP. In Fig. 2 the DMS-AP is referred to by numeral 20. Elements of Fig. 2 which are unchanged from Fig. 1 have the same reference numerals, those which require modification have the same reference numeral but it is dashed i.e. SCH 5'. The communications link between switch 1 and the DMS-AP involves a minimum of two 64 kb/s channels.It should be noted that the call establishment information referred to above is for conventional call set-up, it does not relate to supplementary services. The main control unit MCU (not shown) and markers (not shown) are parts of Switch 1 which also require modification. The other new elements are the Star Peripheral Interface Processor 21 (SPIP), Intelligent Links (Bridge and Through) 22, Announcement Circuits 23 and Alerters 24. Additionally a Three Party Conference Bridge (TCB) (not shown) is provided. The TCB interfaces to a cyclic store CS of the analogue Switch 1 and is controlled by the SPIP 21 under instruction from the SCH 5'.

The SPIP 21 provides control for the supplementary peripherals, Intelligent links 22, Announcement circuits 23 and Alerters 24.

The Intelligent Links (IL) 22 replace a proportion of standard bridge and through links in the Switch 1. In addition to providing the same features as the existing electro-mechanical circuits in Switch 1, the ILs provide: - detection of timed break for Register Recall, register recall is an essential part of the operation of some supplementary services - detection and decode of MF4 signalling - control of speech paths to connect announcements to calling or called parties - control of ringing current - release under instruction from Switch 1 (enhanced TXE 4) - release one side of switched path under instruction from Switch 1 (enhanced TXE 4).

The intelligent links provide the system with improved control over the links and hence the ability to set up and release the more complicated serial trunking sequences which are required for many of the supplementary services.

A customer recall class of service (COS) is provided to indicate whether the customer wishes to be able to use the recall service. This enhanced COS is MMI updatable. Customers who have the recall class of service or who have one of the supplementary services which need register recall will be allocated an intelligent link for every originating or terminating call and will thus be able to use register recall for any allowed purpose. The intelligent links thus provide four ringing cadences which will be used for some of the supplementary services. The intelligent links will always give a burst of immediate ringing (i.e. continuous ringing) then a pause before sending the desired ringing cadence.

The announcement circuits (ACTs) 23 replace existing tone relay sets and provide network announcements to replace NU (Number Unobtainable), BT (Busy Tone) and EET (Equipment Engaged Tone) for all customers, as well as announcements which correspond to Connection Not Admitted (CNA) conditions received on CC&num;7 messages. For some services the ACTs also provide dial tone or ringing tone. In addition the ACTs provide guidance announcements for Supplementary Service customers on service activation, de-activation and interrogation and intermittent dial tone, call waiting tone and special call waiting tone.The ACTs provide: - detection and decode of MF4 signalling - control of . speech path to connect announcements to customers - release under control from Switch 1 (enhanced TXE 4) The Alerters 24 (ALTR) are new units used as calling devices for services such as Reminder and ADdcC (advise duration and charge). Each ALTR circuit is connected to the cyclic store and under control can provide a calling condition. The calling condition is detected and via use of the TXE Allotter an MCU (Main Control Unit) of the Switch 1 is allocated to the call. The MCU will assign a Register 25 to establish the path connections necessary to complete the call set-up process.

The DMS-AP 20 comprises the CM 26, a message bus or switch 27 (DMS-Bus), which is a high-speed transaction bus that acts as a hub for interprocessor communications and supports multiple application processors and allows them to communicate with each other as well as those in the DMS-Core (CM), a link interface unit (LIU) shelf 28 and link interface units 29.

Communication between Switch 1 and DMS-AP 20 is via spare TSl6s in the 2Mbit PCM links connecting Switch 1 to the DMSU 3. The messaging between Switch 1 and the DMS-AP 20 utilises a signalling protocol based on CCITT No 7 signalling system (CC&num;7) and called Adjunct Communications Protocol (ACP). The message flows between the SCH and the DMS-AP are based on CC&num;7 signalling using the Message Transfer Part (MTP) with the ACP User Part. The layer 2 tasks will provide error detection and recovery on the signalling links. The layer 3 termination task will be responsible for managing the ACP signalling link set, bringing links in and out of service and load sharing the ACP signalling traffic across the available links. Dependent on network topology the ACP signalling link may utilise spare capacity in either the main or standby routes to the DMSU.To inject and receive this signalling information on the PCM systems, the LIUs 29 at the DMS-AP 20 are modified in comparison with Standard LIUs by the addition of paddle boards.

At the DMS-AP20 ACP signalling on TS16 is extracted from the incoming PCM stream by a LIU29 with the remaining 30 speech channels being handled transparently. The modified PCM stream is routed to the DMSU. On the transmit path the ACP is injected into the "free" TS16, again without any modification to the speech channels. The modified LIUs support PCM 30 maintenance measures such as TS0 interruption.At the TXE 4 the information extracted by CXIs 13 is CAS or CCS depending on the transmission direction, with CAS information multiplexed by CMUX (CAS/CC*7 Multiplexer) 14 prior to application to CCF 9'. In order to support the ACP the TXE 4 enhanced system requires a change to the CCF 9 functional processor. An additional data communications board is added to the first CCF 9 replica on each side of the LAN.Whilst not specifically mentioned before it will be appreciated that for system security various elements of TXE 4 enhanced are at least duplicated, hence the reference to CCF 9 replica. Each CCF 9' of the replica handles a proportion of the signalling between the SCH 5' and the DMS-AP 20.

The use of spare TS16 channels in the CC&num;7 routes to the DMSU or other switching centres eliminates the requirement for additional transmission equipment between these sites in order to connect the DMS-AP 20 and Switch 1.

The software of the SMF 7' is updated in comparison with that of SMF 7 in order to handle additional MMI commands to support the Supplementary Services and the maintenance of the additional necessary software and hardware resources.

Administration updates to customer specific data are forwarded to the DMS-AP 20 as discussed below with regard to Operations Administration and Maintenance. It will also be necessary to introduce an additional process at the SMF in order to ensure consistency of customer configuration data held by the enhanced TXE 4 and the DMS-AP 20.

The CDF8 software will be updated to cater for Supplementary Service calls which need charge advice and new call record types.

Certain supplementary services require by-pass numbers. For individual customers who need a by-pass number, the number is stored in both the cyclic store (CS) Y-slot corresponding to the customer's line slot and in the DMS-AP 20 allocated to the customer. It will be the administration's responsibility to see that the by-pass number entered into the cyclic store is the same as that entered via the MMI. The DMS-AP 20 is not able to correlate these two DNs (Directory Number).

For PBXs, it is possible to allocate by-pass numbers to individual PBX lines. A combined by-pass/night service number is stored in the cyclic store Y-slot and the same number must be stored in the enhancement memory, in the same manner as for individual customers. Note that the presence of the combined by-pass number/night service number in the cyclic stores causes the normal PBX hunting mechanism to be avoided. When a call is made to a by-pass number, a triple-burst ringing cadence will be sent instead of the standard ringing cadence.

Where a customer needs the same feature for one or more supplementary services, then one common feature is used. For example, where appropriate a customer will be provided with one by-pass number which is then used for all relevant supplementary services. The customer is not able to have a separate keyword per supplementary service.

Customers who have been provided with one or more subcontrolled services will be able to activate, interrogate or de-activate these services by going off-hook and dialling a star-hash sequence of digits using MF4 signalling. For example, for activations dial *SC&num;, where SC is the appropriate service code for the supplementary service, for interrogations dial *&num;SC&num; and for de-activations dial #SC#. For some services, additional parameters are required after the service code, such parameters use the * as a separator.

The provision of the new customer services described below is governed by new classes of service (COS). These star classes of service are under administration control via the Switch 1 (TXE 4 enhancement) MMI 15. Their individual installed/not-installed state is held in the DMS-AP 20. Only a global star/non-star class of service is held in the cyclic store of Switch 1. In addition, each star class of service has an activated/not-activated state, which is governed either by the customer (using MF4 - Dual Tone Multi Frequency Signalling System No 4) and * and &num;) and/or by the administration (via the MMI) as appropriate for the individual service.

The system configuration shown in Fig. 2 uses a distributed system software architecture with certain Supplementary Service logic in the Switch 1 and other Supplementary Service logic in the DMS-AP 20.

For the simpler Supplementary Service calls i.e. those not requiring transfer of connections following a stable call state, the DMS-AP 20 responds by providing the data necessary for Switch 1 to complete the Supplementary Service procedure. For these calls the DMS-AP does not track call status.

For complex supplementary Service calls i.e. Three Party Calls, Call Waiting and Call Diversion - No reply, and services invoked by register recall, the DMS-AP 20 assumes call control following event data received from Switch 1. The DMS-AP 20 has the service logic for these calls and has sufficient knowledge of the Switch 1 to initiate switch network connections.

The Switch 1 resumes control of the call when it has reached a stable state with a connection between two subscribers, or for completion of the call release sequence. If there is a failure of the DMS-AP 20 or the signalling link, subscribers will be limited to Plain Old Telephone Service (POTS). Supplementary Service calls in progress at the time of a failure will be maintained in stable call states or cleared if in an unstable call state, or if the call enters a change of state.

The messaging necessary between the switch 1 and the DMS-AP 20 for all supplementary services will now be described with reference to Fig. 3. All the services are considered within the same diagram in an attempt to show the total number of messages which may be involved in a call between supplementary service subscribers or a supplementary service management operation.

The following text details the steps involved in the call set-ups, each numbered paragraph mapping to the numbers within the TXE 4 (switch 1) and DMS-AP 20 processors.

1. Subscriber goes off-hook and is directed by state of line logic to an MCU. The MCU determines if the calling party has the fixed destination service active, in which case no dial tone is returned. Otherwise, the MCU simply checks if the subscriber is a supplementary service subscriber.

2. A check of the calling party Class of Service (COS) is initiated by the MCU to the DMS-AP 20 to determine the type of dial tone to be returned to the subscriber (broken dial tone is returned should the subscriber have Incoming Calls Barred (ICB) or call diversion active). In addition, the DMS-AP 20 returns the Outgoing Calls Barred (OCB) status for the calling party and a flag indicating if the warm line option is active.

3. If the COS check indicated that OCB all calls is currently active for the calling subscriber, the termination is parked. Similarly, broken dial tone is returned if the COS check determined this requirement.

4. The dialled digits are then received from the subscriber and analysed by the MCU. The MCU determines if the called subscriber is a supplementary service subscriber. The digits are then passed to the DMS-AP 20 via the CCF 91 if either or both the calling or called subscriber is a supplementary service subscriber.

If a "star" (*) or "hash" (&num;) character is identified at the beginning of the sequence, the MCU collects the digits and passes them to the DMS-AP 20 for further processing. Further requests for digits may be initiated by the DMS-AP 20 for further processing.

Further requests for digits may be initiated by the DMS-AP 20 to complete the supplementary service operation.

Should the called digits form part of a request for a three party call, the equipment number of the held party (EEN - enhancement equipment number) is passed to the DMS-AP to identify the parties involved in the potential 3 way call (3wc).

5. The DMS-AP 20 determines the called party COS.

Should the call be involved in a diversion (div), the diversion loop flag is set for the directing party.

6. An announcement is sent to the calling subscriber if the call setup fails due to supplementary service restrictions.

7. On completion of call set up, the dialled digits are stored in the DMS-AP 20 for the Repeat Call Facility (RCF) if the service is active for the calling subscriber.

8. On call answer a request is passed to the DMS-AP 20 to reset the diversion loop flags for any diverting parties involved in a calL If the subscriber fails to answer, the call set up continues from step 4, with a COS check for the party to whom the call is being diverted. A further check is required to ensure the "calling" party (i.e. the party who is diverting the call on no answer) has no service restrictions which would prevent the origination of the diverted calL 9. Any subscriber diversion loop flags are reset, allowing further calls to be diverted through the terminations.

10. During an established call, if register recall is detected, the sequence of events progresses from step 1 as indicated in Fig. 3 (except for dialled digits received via the intelligent links).

11. On call cleardown, a further check is initiated to the DMS-AP to determine if ADZcC is active for the calling party.

12. The DMS-AP 20 checks the COS for the calling subscriber and returns the AD & information if the service is currently active or requested for the last call.

Operations Administration and Maintenance (OA & ) will now be described with reference to Fig. 4 for the TXE 4/DMS-AP 20 arrangement described above. The implementation provides OAtcM for the DMSAP 20 via a local Maintenance and Administration Position (MAP) terminal or through a TXE 4 MMI terminal (via the ACP link).

In order to minimise the impact of introducing the DMS-AP 20 and supplementary services to an existing network including TXE 4 and network management (NM) support systems environment, there must be minimal change to the current processes for managing TXE 4. Likewise, there should be a non-disruptive introduction of the DMS OAdcM technology required to manage the DM > AP.

Currently, TXE 4 exchanges are managed at the local exchange site. The only significant exception to this are the propagation of alarms to the Network Operations Unit (NOU) for display and the output of billing records, statistics and other data to the District Data Collector (DDC). The TXE 4s could however be managed from the remote operations centre i.e. the NOU. In view of this and the fact that the DMS-AP 20 is shared by a number of TXE 4s, as many DMS-AP OAdcM functions as possible are preferably performed from a remote and more centralised MAP location. Fig. 4 provides an overall view of the OAdcM system and how it fits the existing environment.

From the local/remote MAP, network staff are able to perform or view the following OAdcM functions in the DMS-AP 20.

Resource configuration including resource provisioning changes and resource provisioning data queries, fault management including detection and classification of trouble indications; indication and storage of trouble detections; service recovery both manual and automatic; fault sectionalisation both on-demand line, trunk, ACP interface testing and on-demand and automatic diagnostics; fault resolution and return to service both for remote resolution and where a workforce is required, testing management including performance of or administration of ACP interface testing, resource maintenance including performance of or administration of routine diagnostics; performance of on-demand diagnostics; output of results of diagnostics, performance management including administration of measurement systems; output of performance measurements; output of overload/congestion indications; administration of overload/congestion controls, accounting management including administration of a DMS-AP billing system, security management including assignment/modification of access security; assignment/modification of access privileges, and recovery management including system backup, system recovery and reload, and system robback.

From a users perspective, the TXE 4 management procedures are unchanged.

The OAdcM functions that require coordination between TXE 4 and the DMS-AP 20 to maintain the current user's perspective are in the areas of Services Configuration and Accounting Management. The TXE 4 is the single entry point for all service orders. Service changes as they are made will be propagated to the DMS-AP 20 via the ACP link. Similarly for accounting management, the DMS-AP 20 passes the necessary billing data via the ACP link to the TXE 4 in order to ensure that all customer calls and service invocations are correctly recorded and billed.

A number of MMI operations are provided to support the supplementary services. All operations can be executed via standard MMI menus or a hierarchy of menus. Five types of MMI operation are provided: - input of resource information e.g. installation state or in-service state of star peripherals.

- per customer cease/provide, to change the status of the star class of service to a single customer. This includes not only the star class of service itself but also associated parameters and/or activation state where relevant.

- predefinition of up to 16 "star service groups" where a star service group is any collection of star classes of services. Where reasonable the MMI allows the administration to specify a star service group instead of an individual star class of service.

- per tariff group cease/provide, to change the status of the star class of service for all customers belonging to the specified tariff group. The MMI subsequently provides a list of all customers with the specified tariff group so that their individual class of service data may be changed via the MMI, and - display of supplementary service statistical counts.

As will be appreciated from the above the invention proposes the provision of supplementary services for customers to analogue exchanges by making use of supplementary service call handling processes already existing within the DMS system for digital exchanges. It is proposed to provide a DMS-AP, which is a unit having these call handling processes, adjacent to a DMSU or equivalent and to share its functioning between a number of analogue exchanges. The necessary signalling messages for the supplementary services are carried in spare TSl6s of the existing 2Mbit PCM links between the analogue and digital exchanges, or rather to the DMS-AP located at the digital exchange, in an Adjunct Communications Protocol (ACP) and thus no additional transmission equipment is necessary.

Claims (4)

CLAIMS:

1. An automatic telecommunications system including one or more analogue telephone exchanges and at least one digital telephone exchange, wherein the analogue exchanges are connected with the digital exchange by PCM transmission links having common channel signalling capabilities, wherein to provide subscribers to the analogue exchanges with supplementary services a processing means having supplementary services call handling processes is located at a said digital telephone exchange, connected to at least one said analogue telephone exchange, by said PCM transmission links and connected to said digital exchange, and wherein signalling messages relating to the supplementary services are carried between said processing means and the analogue exchange in spare signalling channels of said PCM transmission links.

2. A system as claimed in claim 1, wherein the signalling messages relating to supplementary services employ a protocol based on the CCITT No 7 signalling system and different to that employed for call supervision and call establishment between the analogue and digital exchanges.

3. An automatic telecommunications system substantially as herein described with reference to and as illustrated in Fig. 2, with or without reference to Figs. 3 and 4, of the accompanying drawings.

4. A digital telephone exchange adapted to provide several analogue telephone exchanges with supplementary services normally unavailable thereto, the digital exchange having a processing means with supplementary services call handling processes located thereat and wherein in use the digital exchange is connected to the analogue exchanges by PCM transmission links having common channel signalling capabilities and signalling messages relating to the supplementary services are carried between said processing means and the analogue eh exchanges in spare signalling channels of said PCM transmission links.