WO2000051313A2 - Etablissement d'appels dans un systeme de telecommunications - Google Patents

Etablissement d'appels dans un systeme de telecommunications Download PDF

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Publication number
WO2000051313A2
WO2000051313A2 PCT/FI2000/000079 FI0000079W WO0051313A2 WO 2000051313 A2 WO2000051313 A2 WO 2000051313A2 FI 0000079 W FI0000079 W FI 0000079W WO 0051313 A2 WO0051313 A2 WO 0051313A2
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WO
WIPO (PCT)
Prior art keywords
coding type
preference
message
call set
call
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/FI2000/000079
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English (en)
Other versions
WO2000051313A3 (fr
Inventor
Keijo Laiho
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Priority to AU25502/00A priority Critical patent/AU2550200A/en
Priority to JP2000601808A priority patent/JP2002538675A/ja
Publication of WO2000051313A2 publication Critical patent/WO2000051313A2/fr
Publication of WO2000051313A3 publication Critical patent/WO2000051313A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/18—Service support devices; Network management devices
    • H04W88/181—Transcoding devices; Rate adaptation devices

Definitions

  • the present invention relates to call set-up in a telecommunications system and more particularly to the setting-up of voice calls via a called number translation point which performs a called party number translation.
  • call set-up generally involves a negotiation between the originating and terminating exchanges to determine the type of speech coding which is to be used for the call. Speech coding of voice signals is primarily used to reduce the transmission bit rate over the connection.
  • VSELP is referred to as a "full-rate” codec (coder/decoder) and involves a data rate of 11.2kbits/sec
  • PSI-CELP is a "half-rate” codec involving a data rate of 5.6kbits/sec .
  • a mobile network will support both PSI-CELP, VSELP, and ⁇ -law, or only VSELP and ⁇ - law.
  • coding and decoding may be carried out at the level of the mobile station rather than at the level of the exchange .
  • the voice signals may be transmitted in both directions without any need for intermediate transcoding, i.e. translation from one coding type to another.
  • the voice data must be transcoded, or the originating mobile station must change to VSELP coding if possible.
  • the latter is preferred as transcoding introduces distortion into signals and occupies additional processing capacity at the terminating exchange (normally referred to as a Mobile Switching Centre (MSC) ) .
  • each MSC knows the coding capabilities and preferences of its own network.
  • each MSC maintains a database containing the coding capabilities and preferences of other networks (sometimes referred to as "foreign" networks) .
  • the originating MSC identifies the terminating exchange on the basis of the called number prefix.
  • the originating MSC determines a preferred coding type on the basis of its own network's capabilities and preferences, and of the capabilities and preferences of the terminating exchange.
  • the originating MSC then allocates an appropriate speech channel, over the air interface, to the calling mobile station.
  • IAM Initial Address Message
  • the IAM contains a number of fields which contain various data relating to the call .
  • One of these fields is referred to as "User Service Information" (USD field and contains the coding preference as determined by the originating MSC.
  • USD field contains the coding preference as determined by the originating MSC.
  • that MSC Upon receipt of the IAM at the terminating MSC, that MSC examines the transmitted coding preference and compares it to its own current coding preferences. It is noted that the current preferences of an MSC may differ from those notified to and stored by the originating MSC, e.g. due to changes in traffic levels at the terminating MSC.
  • the terminating MSC may either accept the transmitted preference, or indicate an alternative preference, by returning to the originating MSC a Mobile Application Part (MAP) message. It is noted that if the terminating MSC decides on an alternative preference, the choice is restricted. Specifically, if the preference indicated in the IAM is for PSI-CELP, then the terminating MSC may select VSELP or ⁇ -law as alternatives, whilst if the preference indicated in the IAM is for VSELP, the terminating MSC may select only ⁇ -law as an alternative, i.e. the terminating MSC may only move down the list: PSI-CELP ⁇ VSELP ⁇ ⁇ -law.
  • the originating MSC may either adopt the coding type indicated therein, or may adopt the default ⁇ -law coding .
  • the terminating MSC may return no MAP message to the originating MSC. If no MAP message is received at the originating MSC ahead of a so-called Answer Message (ANM, which is transmitted from the terminating MSC to indicate call answer) , then the originating MSC assumes the default coding, i.e. ⁇ -law, upon receipt of the ANM.
  • NNM Answer Message
  • I Intelligent Network
  • SSP Service Switching Point
  • SCP Service Control Point
  • SSPs in telecommunications networks presents a problem vis-a -vis coding type negotiation.
  • the originating MSC transmits the IAM message, it must have determined a coding type preference in order to allocate an appropriate channel to the calling mobile station.
  • the originating MSC cannot determine from the dialled number the identity of the terminating network. Therefore the preference must be determined solely on the capabilities and preferences of the originating MSC.
  • the SSP can determine the identity of the terminating MSC and hence its coding type capabilities and preferences, it is not aware of the complete set of current preferences of the originating MSC (which may differ from time to time in comparison with those preferences previously notified to the SSP and other network nodes) . The SSP is therefore unable to perform any meaningful adjustment to the preference indicated in the IAM.
  • the result is that in many cases ⁇ -law coding will be selected even when a higher quality coding is available at both the originating and terminating networks. For example, consider the case where the preference of the originating MSC is for VSELP coding, but it is also capable of using PSI-CELP.
  • VSELP will be identified as the preferred coding type.
  • the IAM is then relayed to the terminating MSC from the SSP.
  • the terminating MSC is not capable of using VSELP, it does not have the possibility of reverting to PSI-CELP (as it can only use the return MAP message to move down the coding type order noted above) and therefore the call must use the default ⁇ -law coding type.
  • GMSCs Gateway Mobile Switching Centres
  • a method of negotiating a coding type during the setting up of a voice call between an originating exchange and a terminating exchange of a telecommunications system, where the call set-up procedure is directed via a called number translation node comprising the steps of:
  • the call coding preference determined at step (4) corresponds with the primary coding type preference identified in the call set-up message, identifying in the call set-up message, the primary coding type preference as the preferred coding type, otherwise identifying in the call set-up message, the secondary coding type preference as the preferred coding type ; and (6) transmitting the call set-up message from the number translation node to the terminating exchange.
  • Embodiments of the present invention enable an intermediate called number translation node to be provided with the coding type preferences of the originating exchange and the coding type preferences of the terminating exchange such that the number translation node may select a preference in substantially the same manner as may be done in the absence of a called number translation node.
  • the called number translation node is a Service Switching Point (SSP) of an Intelligent Network. More preferably, at step (2) , the identity of the terminating exchange is determined using a signalling connection between the SSP and a Service Control Point (SCP) .
  • SSP Service Switching Point
  • SCP Service Control Point
  • the originating exchange is a Mobile Switching Centre of a mobile digital network. More preferably, the terminating exchange is also a Mobile Switching Centre of a digital mobile network.
  • the MSCs may belong to PDC networks . The invention however is applicable to fixed line networks and to other mobile digital networks .
  • the MSCs belong to PDC networks
  • said preferences may be for either PSI-CELP or VSELP.
  • the networks and MSCs may have the capability to use a default coding type, namely ⁇ -law coding.
  • the primary coding type preference is indicated in the call set-up message, sent from the originating exchange to the called number translation node, by appropriately setting a User Service Information prime (USI ' ) parameter.
  • USI User Service Information prime
  • the secondary coding type preference may be similarly indicated by setting the User Service Information (USI) parameter.
  • the USI parameter is transmitted unchanged to the terminating exchange.
  • the USI parameter is replaced in the call set-up message with the USI' parameter.
  • said call set-up message is an Initial Address Message (IAM) .
  • IAM Initial Address Message
  • apparatus for negotiating a coding type during the setting up of a voice call between an originating exchange and a terminating exchange of a telecommunications system, where the call set-up procedure is directed via a called number translation node
  • the apparatus comprising: means for transmitting from the originating exchange to the called number translation node a call set-up message, the call set-up message including the called number and an identification of at least a primary coding type preference of the originating exchange and of a secondary coding type preference if the originating exchange has such a secondary preference; means for receiving said call set-up message at the called number translation node and determining thereat the identity of the terminating exchange based upon the called number; means for determining the coding type preferences of the terminating exchange at the called number translation node; means for determining a call coding type preference at the called number translation node on the basis of the coding type preferences determined for the terminating exchange and of the coding type preference (s) of the originating exchange identified in
  • a third aspect of the present invention there is provided a method of determining a coding type preference at a called number translation node during the setting up of a voice call between an originating exchange and a terminating exchange of a telecommunications system, the method comprising the steps of :
  • Figure 1 illustrates schematically a telecommunications system wherein a call set-up procedure may be routed through a Service Switching Point ; and
  • Figure 2 is a flow diagram illustrating a call setup procedure in the system of Figure 1.
  • FIG. 1 a telecommunications system comprising first and second mobile telephone networks 1,2.
  • these networks 1,2 are assumed to be PDC networks according to the Japanese standard.
  • Each of the networks 1,2 comprises one or more exchanges, termed "Mobile Switching Centres" (MSCs) 3,4, which connect calls to and from mobile stations 5,6.
  • MSCs Mobile Switching Centres
  • a given mobile station 5,6 is connected to the MSC 3,4 of its network via a Base Station Controller (BSC) 7,8 and a Base Transceiver Station (BTS) 9,10.
  • BSC Base Station Controller
  • BTS Base Transceiver Station
  • the BTS 9,10 is arranged in the "cell" in which the mobile station 5,6 is located, whilst the BSC 7,8 is associated with a small group of cells (and hence BTSs) including that in which the mobile station 5,6 is located.
  • a mobile station 5 requests a telephone connection by transmitting a SETUP message to the associated MSC 3 via the BTS 9 and BSC 7.
  • This message includes the number of the called party. Assuming that the called party number is a conventional B-number, i.e. corresponding to a specific subscriber, and that the called party is a subscriber of some foreign network, i.e. network 2, then the MSC 3 prepares a call set-up message (specifically an IAM) for transmission to the MSC 4 defined by the prefix of the B-number.
  • a call set-up message specifically an IAM
  • preparation of the IAM involves determining a preferred coding type (i.e. PSI-CELP, VSELP or ⁇ -law) based upon the capabilities and preference of the originating MSC 3, and the capabilities of the terminating MSC 4.
  • the later are maintained in a capabilities database 11 associated with the MSC 3.
  • the originating MSC 3 is capable of using both PSI-CELP and VSELP but prefers PSI-SELP, and that the terminating MSC 4 is also capable of using both PSI-CELP and VSELP
  • the originating MSC 3 indicates its preference for PSI-SELP in the User Service Information parameter (USI) of the IAM.
  • USI User Service Information parameter
  • the IAM is then sent to the terminating MSC 4, via an interconnecting network 12. It is noted that after determining the coding type preference, and prior to transmitting the IAM, the originating MSC 3 allocates the necessary half rate channel to the calling mobile station 5.
  • the terminating exchange 4 In the event that the terminating exchange 4 has a coding preference which coincides with that defined in the USI parameter, i.e. in this example PSI-CELP, it returns a MAP message to the originating MSC 3.
  • the MAP message has two fields, Codec status and Codec throughrate information.
  • the former field is set to indicate Codec through (i.e. mobile to mobile transmission without transcoding)
  • the latter field is set to indicate half rate coding (i.e. PSI- CELP) .
  • PSI- CELP half rate coding
  • the described call set-up procedure is according to the conventional PDC set-up procedure.
  • the set-up procedure which will now be described represents a modification to that conventional procedure.
  • the number dialled at the mobile station 5 is an 800 number or the like, e.g. associated with some special service such as free phone, or shortened number dialling.
  • the dialled number does not directly represent a network subscriber, but rather is a number which requires translation to determine such a subscriber number.
  • the originating MSC 3 Upon receipt of a SETUP message containing an 800 number, the originating MSC 3 prepares the IAM message for relaying to the terminating exchange.
  • the MSC 4 is unable to identify the terminating exchange as this cannot be determined directly from the 800 number.
  • the originating MSC 3 therefore inserts into the User Service Information prime parameter (USI ' ) its own speech coding type preference (and allocates a channel to the calling mobile station 5) .
  • the preference will be either PSI-CELP or VSELP.
  • the originating MSC also inserts an alternative speech coding type preference. If the MSC 3 has only one preference, then this is inserted in the USI parameter.
  • the originating MSC 3 recognises that the initial destination for the IAM is a Service Switching Point (SSP) 13.
  • SSP Service Switching Point
  • the IAM is therefore transmitted to the SSP 13 where a number translation is performed on the dialled 800 number to determine the subscriber B-number to which the call is to be directed.
  • the SSP 13 is able to identify the terminating exchange 4 for the call.
  • the SSP 13 has a capabilities database 11 corresponding to that of the originating MSC 3 (and of the terminating MSC 4) .
  • the SSP 13 Upon receipt of the IAM from the originating MSC 3, the SSP 13 interrogates the database 11 to identify the capabilities of the terminating MSC 4.
  • the USI parameter is left unchanged by the SSP.
  • the USI' parameter may be dropped (although this is not essential as it will in any case be ignored by the terminating MSC 4) .
  • the IAM is then relayed by the SSP 13 to the terminating exchange 4.
  • the definition of the coding type preference in the USI parameter is replaced, at the SSP 13, by the preference identified in the USI' parameter.
  • the coding type preference defined in the USI ' parameter may be dropped before the IAM is relayed to the terminating MSC 4.
  • the originating MSC 3 is capable of using both PSI-CELP and VSELP, and prefers to use PSI-CELP.
  • the USI' parameter is set to indicate PSI-CELP, whilst the USI parameter is set to indicate VSELP. If the SSP 13 determines that the terminating exchange is only capable of using VSELP, then the USI' parameter may be dropped, and the IAM is forwarded to the terminating exchange 4 via the interconnecting network 12.
  • the SSP 13 determines that the terminating exchange 4 is capable of using both PSI-CELP and VSELP.
  • the USI parameter is replaced with the USI ' parameter before forwarding the IAM to the terminating exchange 4.
  • the set-up procedure proceeds in the conventional manner. That is to say that the terminating MSC 4 determines whether the preference identified in the USI parameter coincides with its own current preference. If so, this is indicated in the returned MAP message. If the signalled preference does not coincide with that of the terminating MSC 4, then an alternative coding type may be identified in the MAP.
  • Figure 2 is a flow diagram illustrating the procedure described above, where a mobile to mobile call is routed through a Service Switching Point .
  • the invention may be applied to number translation occurring at a Gateway MSC (GMSC) of a mobile network.
  • GMSC Gateway MSC
  • HLR Home Location Register
  • the GMSC replaces the directory number with a roaming number received from the HLR.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Telephonic Communication Services (AREA)

Abstract

L'invention concerne un procédé pour négocier un type de codage pendant l'établissement d'un appel vocal entre deux centres de commutation mobile MSC (3, 4), selon lequel la procédure d'établissement d'appel est dirigée via un point de commutation de services SSP (13). Un message d'adresse initiale (IAM) est transmis depuis le MSC d'origine (3) au SSP (13) et comprend le numéro appelé et une identification des préférences de codage des types primaire et secondaire du MSC d'origine (3). Le SSP (13) détermine l'identité du MSC de terminaison (4) sur la base du numéro composé puis détermine les préférences du type de codage du MSC de terminaison (4). Le SSP (13) détermine ensuite une préférence du type de codage sur la base des préférences du type de codage du MSC de terminaison (4) et la (les) préférence(s) du type de codage du central d'origine (3). Si la préférence de codage de l'appel ainsi déterminée diffère de la préférence du type de codage primaire identifiée dans l'IAM, le type de codage primaire est remplacé par le type de codage primaire, et l'IAM est transmis au MSC de terminaison (4).
PCT/FI2000/000079 1999-02-24 2000-02-04 Etablissement d'appels dans un systeme de telecommunications Ceased WO2000051313A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU25502/00A AU2550200A (en) 1999-02-24 2000-02-04 Call set-up in a telecommunications system
JP2000601808A JP2002538675A (ja) 1999-02-24 2000-02-04 通信システムにおける呼の設定

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI990398A FI108767B (fi) 1999-02-24 1999-02-24 Puhelunmuodostus tietoliikennejärjestelmässä
FI990398 1999-02-24

Publications (2)

Publication Number Publication Date
WO2000051313A2 true WO2000051313A2 (fr) 2000-08-31
WO2000051313A3 WO2000051313A3 (fr) 2000-12-07

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PCT/FI2000/000079 Ceased WO2000051313A2 (fr) 1999-02-24 2000-02-04 Etablissement d'appels dans un systeme de telecommunications

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JP (1) JP2002538675A (fr)
AU (1) AU2550200A (fr)
FI (1) FI108767B (fr)
WO (1) WO2000051313A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004091151A1 (fr) * 2003-04-07 2004-10-21 Telefonaktiebolaget Lm Ericsson (Publ) Procede et systeme de commande du debit dans un reseau

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7308248B2 (en) * 2003-10-24 2007-12-11 Lucent Technologies Inc. Connection of one or more toll-free calls with one or more mobile phones associated with one or more toll-free numbers

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4924480A (en) * 1988-03-11 1990-05-08 American Telephone And Telegraph Company Codecs with suppression of multiple encoding/decodings across a connection
US5608779A (en) * 1994-11-08 1997-03-04 Motorola, Inc. Method for communications between mobile units using single and multiple switching center configurations
US5867784A (en) * 1995-07-05 1999-02-02 Telefonaktiebolaget Lm Ericsson Call forwarding in a mobile communication system
FI106905B (fi) * 1998-05-12 2001-04-30 Ericsson Telefon Ab L M Menetelmä ja laite tietoliikennejärjestelmässä

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004091151A1 (fr) * 2003-04-07 2004-10-21 Telefonaktiebolaget Lm Ericsson (Publ) Procede et systeme de commande du debit dans un reseau
EP2099179A1 (fr) 2003-04-07 2009-09-09 Telefonaktiebolaget L M Ericsson (publ) Methode et systeme de negotiation de debit dans un réseau

Also Published As

Publication number Publication date
FI990398A7 (fi) 2000-08-25
JP2002538675A (ja) 2002-11-12
AU2550200A (en) 2000-09-14
FI990398A0 (fi) 1999-02-24
FI108767B (fi) 2002-03-15
WO2000051313A3 (fr) 2000-12-07

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