METHOD AND DATA STRUCTURE FOR THE CONTROL OF SWITCHING CENTERS IN A TELECOMMUNICATIONS NETWORK

Abstract: The invention relates to a method and data structure for controlling switching centers (1, 14, 17, 19, 21, 23, 25, 27). According to the invention switching centers (1, 14, 17, 19, 21, 23, 25, 27) are controlled to update the control information stored in the semipermanent databases of said switching centers (1, 14, 17, 19, 21, 23, 25, 27) with information retrieved from service database (5) and the update operation of said semipermanent databases of said switching centers (1, 14, 17, 19, 21, 23, 25, 27) is chained so that selected switching centers (1, 14, 17, 19, 21, 23, 25, 27) of desired telecommunications networks are arranged to perform sequentially the updating of their control information with information retrieved from said service database (5).

Description: Method and data structure for the control of switching centers in a telecommunications network The invention relates to a method according to the preamble of claim 1 for the control of switching centers in a telecommunications network. The invention also concerns a data structure suited for the control of switching centers in a telecommunications network. According to conventional techniques, the flow of control information such as charging data is typically handled individually for each switching center basis by perform- ing the transfer of charging data separately to the. charging database of each switching center. As the number of switching centers in, e.g., Finland runs into thousands, the updating of charging data is an operation requiring plenty of work. According to the IN (Intelligent Network) standard being adopted in the art, a telecommunications network has a common SCP (Service Control Point) database of services that facilitates centralized maintenance of control information such as charging data in this service database. However, such a service database is incapable of transferring control information to the switching centers, whereby a request for control information, typically charging data, must be placed on the database every time a call is being processed. Obviously, these request messages may put an excessive load on the service database, and hence, on telecommunications network, too. It is an object of the present invention to overcome the drawbacks of the above-described techniques and to achieve an entirely novel method of controlling telephone switching centers. The invention is based on primarily storing the network control information such as charging data in semi¬ permanent databases of switching centers, while the desired changes are first made in a centralized manner in the service database and then the switching centers are controlled to update their own databases in a chained manner with the desired control information retrieved from the centralized SCP service database. More specifically, the method according to the invention is characterized by what is stated in the characterizing part of claim 1. Furthermore, the data structure according to the inven- tion is characterized by what is stated in the character¬ izing part of claim 11. The invention offers significant benefits. The invention avoids the time-consuming manual step of transferring control information changes. The novel control scheme is accurate and covering, and free from human error in the transfer of database information changes. Compared with, e.g., the request-based charging data update scheme of the IN system, the load on the service database remains very low thus improving the switching speed of calls. Even in the event of such extensive damage to the hardware of the service database or to the transmission path of the requested information that makes the service database inaccessible, the total telecommunications system still remains operative. In the following, the invention will be examined in more detail by means of exemplifying embodiments with reference to the attached drawings, in which: Figure 1 is a block diagram of a telephone network suited to accommodate the application of the invention; Figure 2 is a schematic diagram of a semipermanent switching center database adapted for the control scheme according to the invention; and Figure 3 is a schematic diagram of a data structure according to the invention. With reference to Fig. 1, switching centers 1 and 27 are subscriber-level local switching centers and all the other switching centers 14, 17, 19, 21, 23 and 25 are transit switching centers, typically trunk/toll switching centers. The term switching center later in the context of this publication refers to both subscriber-level local switching centers and transit switching centers which typically are trunk/toll switching centers. The sub¬ scriber-level local switching centers 1 and 27 are interfaced to terminal equipment 3 which may comprise PABX connections, conventional subscriber lines, telefax equipment, etc. The service database 5 of an IN system is typically con- nected to the telecommunications network via a single switching center 21, whereby it can serve the entire network. A greater number of service databases 5 is also possible. The operating principle of the service database 5 is not to transfer information in a self-contained manner, but rather, to respond to request messages chiefly sent by switching centers to the database. According to the invention, the switching centers are controlled in a centralized manner so that an authorized person 2 makes a desired change 7 in the service database, next typically the same authorized person controls 9 a first switching center 1 to call a desired secured number, e.g., a hexadecimal number, whereby the connection to said number controls the switching center 1 to request 11 the service database 5 to send a response message with information 13 comprising at least 1) information on the address of the desired data element of the semipermanent database of the switching center 1; 2) the new content of the data element to be updated, and if necessary, the old content thereof; and 3) information on the telephone number of the update chain's next switching center 14 to which the switching center 1 connects the call, sends the number received from the database and said number then activates the next switching center 14 to send a message 15 to request 16 the service database 5 to send a response message containing all the data representing the information 13. The message 15 contains the number which was entirely or partially contained in the response message (message 13) . The invariable portion of the number is typically placed at the end of the number sequence, while according to the invention its place can be anywhere in the number sequence. The number to which the call is placed is advantageously sent in hexadecimal format for security reasons to prevent access to the number from conventional telephone set either accidentally or by tampering attempts . The other reason for the use of hexadecimal numbers is to conserve the numbers of the normal dial number space. An alternative or parallel security operation against system tampering is to define, e.g., a closed user group, whereby the controls 7 and 9 are permissible from a certain connection only. Also alternatively or in parallel with the above-described security operations, verification of the calling party's number can be used, whereby the controls 7 and 9 are permissible from a certain number or numbers only. The call is chained by providing the message 13 always with information on the number to be called next. Accord¬ ingly, this number contains information on the next switching center in the chain and the action to be taken. The number can be changed systematically after the inter¬ pretation of each of the messages 13, whereby the value of the number related to ;he next request can be used as a counter in the service database 5 or in the switching centers permitting termination of the chained information transfer sequence when the value of the number reaches a preset value. Information which can be updated by virtue of the addressing scheme described in this publication include such data as call charging, billing method or charging of call forwarding which information is contained in the semipermanent databases of the switching centers. Simultaneously, the method is suited for changing time information such as synchronizing the time and date information of switching centers, αefining timing functions (wait times for response, dialing progress, etc.) . Furthermore, the method also facilitates the control of routing and authorizing information under fault and catastrophe situations, typically required to establish a so-called authority network in conjunction with an extensive catastrophe, war, etc. With reference to Fig. 2, the semipermanent database 33 of a switching center is divided with regard to its data content into groups 35, 37, 39, etc., whereby charging data can be stored in group 37, for instance. The contents of the other groups may comprise, e.g., routing, authorizing and timing data. Each group is comprised of data elements, of which the diagram illustrates within the group 37 the first data element 41, the Nth data element 43 and the last data element 45. Each data element has an unique address in the database 33. The data element 43 may contain, e.g., information on the charge rate per minute for the area " code 931. With reference to Fig. 3, the structure of the message 13, which according to Fig. 1 forms the response message, must contain indexed addresses for the contents of the semipermanent databases of switching centers complemented with the new contents, and for possible checking, the old contents at the indexed addresses. Hence, the data structure 47 of the response message 13 illustrated in Fig. 3 can be used to, e.g., the database 33 of Fig. 2. The data structure 47 contains at least fields for message type, sender 49, receiver 51, address 53 of data element 43 to be updated and new content 55 of data element 43. Moreover, the data structure 47 may contain information on the old content of the data element 43. Obviously, checking elements are included in the data structure 47 to secure the integrity of transferred data. Accordingly, the data structure 47 can be used in accordance with the invention for updating, e.g,, the content of data element 47 of Fig. 2, wherein the charge rate per minute for area code 931 is changed in all desired switching centers. The exemplify the invention, the fields of the data structure 47 illustrated in Fig. 3 are filled in brackets with information corresponding to the response message 13 of Fig. 1, whereby said information is used to update the data element 43 of the semipermanent database 33, wherein the sender is the service database 5, the receiver is the switching center 1, the data element address is N in the group 37 and the information to be updated is the charging rate for the area code 931. Appendix 1 is listing of an actual definition for the data structure according to the invention. In the context of this publication, the term call denotes an operation in which the switching center receives a number, based on the number selects an outgoing line to which a connection is established and sends to the line at least a portion of the received number. Appendix 1: Exemplifying definition of the data structure according to the invention ~ Buist ::= SEQUENCE { cHGvsMPM [0] CHOICE { numbOfPulses [1] INTEGER (1..255)}} -- "burst' makes it possible to send a burst of pulset within each of the periods of the periodic — charging. -- PulseCharging ::= SEQUENCE { interval [0] INTEGER (100..3600000), - in milliseconds numbOfPulsesInlnterval [1] INTEGER (0..255), chargeAt [2] ENUMERATED { synchronous (1), karlsson (2)} OPTIONA I } — 'chargeAt' is used for choosing cither synchronou' or karlsson charging. If the SSP cannot use this — information, it still shall be able to receive this parameter, but ienore it. — Within the 'level' sequence the 'chargeLevel' parameter is used when a level different — from the ones existing in SSF shall be used. — The OldLevel' parameter is used for indicating tl^ level that should be replaced, if -- 'levelToUse' is sent as the second or further times within the same call. — Either one or both of the OldLevel' and 'chargeLevel' parameters may be present with — the 'levelToUse' parameter when 'level' is used as the chargeBase choice. — ChargeLevel ::= SEQUENCE { firstPcriod [0] PeriodCharacteristicsSet, nextPeriods [1] NextPeriods OPTIONAL, changeGroup [2] INTEGER (! ..255), chargeRatelndex [3] INTEGER (1..4) } — changeGroup, chargeRatelndex: these parameters are needed to link the information within — 'ChargeLevel' to the internal structure of the SSPs' charging mechanisms. All the SSPs do not use —.both of these parameters, but they have to be able to receive them and ignore the unnecessary ones — without any effect on the functionality. - NextPeriods ::= SEQUENCE SIZE (1..3) OF PeriodCharacteristicsSet — PeriodCharacteristicsSet ::= SET SIZE (1) OF Period Characteristics — PeriodCharacteristics ::= SEQUENCE { periodDuration [0] INTEGER (-1..3600), - in seconds, -1 means infinite duration burst [1] Burst OPTIONAL, chargingType [2] CHOICE { pulseCharging [2] PulseCharging} } — 'periodDuration' indicates how long this charging period shall be used. — "burst' indicates the possible charge burst for the period. — When pulse charging should be used the 'pulseCharging 1 parameter indicates the charge — rate for sending pulses.

Claims: Claims : 1. A method of controlling switching centers (1, 14, 17, 19, 21, 23, 25, 27) in a telecommunications network comprising - switching centers (1, 14, 17, 19, 21, 23, 25, 27) connected to each other Dy a telecommunica¬ tions network, said switching centers being provided with semipermanent databases containing alterable network control information related to, i.a., call charging and routing, said information staying constant unless separately altered by an external control, - terminals (3) such as PABX connections, con¬ ventional subscriber lines, telefax equipment etc., connected by a telecommunications network to said switching centers (1, 14, 17, 19, 21, 23, 25, 27) , and - at least one service database (5) common to said network and containing at least a portion of the network control information, c h a r a c t e r i z e d in that - said switching centers (1, 14, 17, 19, 21, 23, 25, 27) are controlled to update the control information stored in the semipermanent data¬ bases of said switching centers (1, 14, 17, 19, 21, 23, 25, 27) with information retrieved from said service database (5) , and - the update operation of said semipermanent databases of said switching centers (1, 14, 17, 19, 21, 23, 25, 27) is chained so that selected switching centers (1, 14, 17, 19, 21, 23, 25, 27) of desired telecommunications networks are arranged to perform sequentially the updating of their control information with information retrieved from said service database (5) , whereby normally no update request message for control information need be sent to the service database (5) separately for each processed call. 2. A method as defined in claim 1, c h a r a c t e r ¬ i z e d in that said switching centers (1, 14, 17, 19, 21, 23, 25, 27) are controlled to update the control information stored in their semipermanent databases by controlling the switching centers to request update information from the service database (5) . 3. A method as defined in claim 1 or 2, c h a r a c ¬ t e r i z e d in that the chaining operation is implemented through externally controlling a switching center (1) to call a number which initiates such a connection to the service database (5) that causes the service database (5) to respond with a message or messages which updates/update the desired information and controls/control the switching center (1) to call a desired next switching center (14, 17, 19, 21, 23, 25, 27) , thus controlling the next switching center to perform the equivalent operation. 4. A method as defined in claim 3, c h a r a c t e r - i z e d in that the switching centers (1, 14, 17, 19, 21, 23, 25, 27) are controlled to call a number which is varied after each call so that the value of said number acts as a counter, and the chained update sequence is terminated when the value of the number reaches a preset value. 5. A method as defined in claim 1, c h a r a c t e r ¬ i z e d in that the message structure is formatted so as to contain information on indexed addresses of data elements of the semipermanent databases of the switching centers (1, 14, 17, 19, 21, 23, 25, 27) , complemented with the new contents of the data element, and for possible checking, the old contents at the indexed addresses. 6. A method as defined in any foregoing claim, c h a r a c t e r i z e d in that the update operation is performed to change charging data. 7. A method as defined in any foregoing claim, c h a r a c t e r i z e d in that the update operation is performed to change routing data. 8. A method as defined in any foregoing claim, c h a r a c t e r i z e d in that the update operation is performed to change timing data. 9. A method as defined in any foregoing claim, c h a r a c t e r i z e d in that the update operation is performed to change time and date data. 10. A method as defined in any foregoing claim, c h a r a c t e r i z e d in that the update operation is performed to change authorizing data. 11. A data structure (47) suited to be sent from a service database (5) as a response message (13) to a request message (16) received from an element (1, 14, 17, 19, 21, 23, 25, 27) of a telecommunications network, said data structure (47) comprising - a field containing information on the message type, - a field containing information on the sender (49) , and - a field containing information on the receiver (51) , c h a r a c t e r i z e d by - a field (53) for the address (37, N) of the data element (43) to be altered, and - a field (55) for the new content of the data element (43) to be altered. 12. A data structure (47) as defined in claim 11, c h a r a c t e r i z e d in that said data structure also contains information on the old content of the data element (43) to be altered.

Inventors: FILS HENRY, FILS, HENRY
Applicants: HELSINGFORS TELEFON AB, HELSINGIN PUHELIN OY, HELSINGIN PUHELIN OY - HELSINGFORS TELEFON AB
Application year: 1995
Main classification: H04Q3
IPC codes: H04M15, H04Q3