FI108767B - Call connection in a telecommunications system - Google Patents

Description

108767 i i

CALL SET UP IN TELECOMMUNICATION SYSTEMS SAMTALSUPPKOPPLING I ETT TELECOMMUNIKATIONSSYSTEM

Field of the Invention

The invention relates to call setup in a telecommunication system and more particularly to the formation of voice calls through the selected number muuttamispisteen, which performs the conversion of the called party number.

Background of the Invention

In a telecommunication system for establishing a call connection; involves negotiation and exchange of information between the network of two or! between multiple nodes. In particular, the establishment of a voice call made over an inter-network border usually involves a negotiation between the calling center and the called exchange to determine the type of speech coding used for the call. Voice coding for audio signals is used primarily. ti to reduce the bit rate of the connection on the connection.

: 1: In the context of Japanese telecommunications networks, the following is the coding of speech: · The basic type is known as μ-law coding. Support for μ- 'legal coding exists on all networks. In modern digital mobile communication networks (known as PDC networks), the network may support one or both of the other two types of coding, namely PSI-CELP and VSELP. '... · VSELP known as a "full rate" (in English. "Full rate") koodek- kinase (coder / decoder), and uses a data rate of 11.2 kbit / s, while the PSI-CELP is a "half rate" ( half-: ·. rate) codec using a data rate of 5.6 kbit / s.

The mobile communication network typically supports both PSI-CELP, VSELP, and μ law, or only VSELP and μ law. Unlike traditional networks, in cellular networks 108767 [512], coding and decoding can be performed at the mobile level rather than at the central level.

In the event that a call is initiated from a mobile station that supports PSI-CELPs, to a mobile station which also supports PSI-CELPs, audio signals can be transmitted in both directions without the need for intermediate transcoding, i.e. from one encoding type to another. . However, if the call is initiated from the same PSI-CELP-enabled mobile station to a mobile station (or network) that supports VSELP but not PSI-CELP, then the voice data must be converted to code or the original mobile station must change to VSELP encoding if possible. Of the two alternatives, the latter is preferred because the code conversion causes signal distortion and requires additional processing capacity at the called switching center [(commonly referred to as the Mobile Switching Center (MSC)).

Obviously, negotiation of the 'encoding type' used for voice calling is necessary due to the possible incompatibility of the • encoding types available to the called network with the called network. Such a consultation is also necessary in order to take into account network operators' preference in coding. For example, it may be that a mobile network operator that supports both PSI-CELP and VSELP prioritizes the provision of high quality speech to subscribers. The choice of encoding '· *' for this operator is therefore full speed VSELP encoding. * · The second, 'like the mobile network operator may MIE-' ·· rather than in maximizing the call handling capacity, and he therefore prefers to use a half-rate PSI-CELP coda-meeting.

3 108767 i In a mobile communication network, each MSC knows the coding capabilities and preference settings of its own network. In addition, every MSC maintains! This is a database that has coding capabilities and preference settings for other networks (sometimes called "foreign" networks). When the mobile station initiates a call, the MSC of the caller j identifies the called center based on the prefix of the dialed number. The inviting MSC then determines the popular coding type based on the capabilities and preferences of its own network and the capabilities and preferences of the called exchange. Based on the preferred encoding type, the calling MSC then assigns the appropriate speech channel for the calling mobile station via the wireless interface.

The call set-up is initiated by sending the so-called Initial Address Message (IAM) to the so-called MSC. The IAM contains a plurality of fields containing various data related to the call. One of these fields is called a User Service Information Field (USI) and it contains an 'encoding selection' determined by the calling MSC. After the IAM has received '·' in the called MSC, this MSC examines the transmitted: '' encoding selection and compares it with its current encoding advantage and layout. Note that current MSC preference settings may differ from those reported to and stored by the calling MSC due to, e.g., changes in traffic volume within the called MSC.

The called MSC can either accept the sent selection, or report the alternative selection by returning the calling MSC: a Mobile Application Message (MAP)

Part message). Note that if the target MSC ends up in an alternative selection, there are limitations to the selection. Specifically, 4,108,767 if the choice shown in the IAM is PSI-CELP, the called MSC can select VSELP or μ-law alternatives, while if the IAM-designated choice is VSELP, the called MSC can only select the μ-law option, i.e. the called The MSC can only move down the list: PSI-CELP - »VSELP -> μ law. Upon receipt of the MAP message, the calling MSC may either implement the encoding type indicated therein or adopt the default μ-law encoding.

In some cases, the called MSC may not send the MAP message caller MSC. Unless the MAP message is received in the caller's MSC before receiving the so-called reply | ussage message (ANM, the Answer Message sent by the called MSC as a response to the call), then, upon receipt of the calling MSC ANM, implements the default encoding, i.e. the μ law.

Many modern telecommunication networks include so-called Intelligent Network Services (IN). Examples of such services are 800 number services and the like, wherein the selected number identifies a Service Switching Point (SSP) to which call setup is initially directed. SSP ;;; performs a number change with the Service Control Point (SCP) to determine the actual destination of the call. Once the actual destination has been determined, the SSP transmits the IAM | provided by the caller exchange '. !! to the center of the called. 1 The use of SSPs in telecommunication networks poses a problem concerning; · 'negotiating the encoding type. As already mentioned, the caller; '·. The MSC must have determined the encoding type selection before transmitting an IAM message in order to determine the appropriate channel for the calling mobile station. However, the called MSC is unable to determine the identity of the target network based on the dialed number. Therefore, the selection must be based solely on the capabilities and preferences of the inviting MSC.

In addition, although the SSP, while receiving the IAM, can determine the identity of the called MSC and thus its coding capabilities and preference settings, it does not know the full set of current preference MSCs (which may differ from time to time in preference to one). layouts previously reported to SSPs and other network nodes). Therefore, the SSP cannot perform any meaningful check on the selection addressed in the IAM. The result is that in many cases μ-law coding is chosen, although higher quality coding is available on both the caller and the called networks. Take, for example, the case where the caller's MSC is VSELP encoding, but it can also use PSI-CELP. Thus, the IAM sent to the SSP indicates that VSELP is the preferred encoding type. The IAM is then transmitted from the SSP to the called MSC. In the event that the called MSC is unable to use VSELP, it does not have the ability to · · · · · · · · · · · · · · · · · · · · · · Reverse PSI-CELP (because it can ;; only use the return MAP message to navigate to the encoding type sequence down), which is why you must use the default encoding type, μ-la, · · 1, · ·, to speak; 2 2 ·

The problem noted in the previous paragraph is not limited to calls routed through SSP. Rather, it occurs' · 1 'whenever a call is routed through a network node where'. · 1 changes the selected number, for example | '· Gateway Mobile Switching Centers for Mobile Networks'' (Gateway Mobile Switching Centers, GMSC).

6 108767

Summary of the Invention

The object of the invention is to overcome or at least alleviate the above disadvantage. A further object is to enable coding type negotiation between two nodes in a telecommunications network, even when the call is initially directed to a number changing node.

According to a first aspect of the invention, there is provided a method of negotiating a coding type between a call center and a called exchange in a communication system, wherein the call set-up procedure I is controlled through a dialing number changing node! comprising the steps of: (1) transmitting a call set-up message from the calling exchange to the number changing node, the call set-up message including the called number and the call center exchange at least a primary coding type selection identifier and a secondary coding type selection identifier; \ '(2) receiving said call set-up message at the number changing node and determining the identity of the called exchange based on the selected number; (3) determining the preference settings for the encoding type of the called exchange in the number changing node; (4) determining, in the number changing node, the selection of the coding type of the call based on the priority setting of the coding type specified for the called exchange and the selection of the coding type of the calling center indicated in the call setup message; * '·· (5) indicates if the call encoding selection determined in step (4) corresponds to the primary encoding type selection indicated in the call setup message, selecting the primary encoding type 108767 pin as the desired encoding type in the call setup message and otherwise indicating a secondary encoding type; selecting a pin as the desired encoding type in the call setup message; and (6) transmitting a call setup message from the number change node to the called exchange.

Embodiments of the invention allow the intermediate dialing node to have interleaved call center coding type preference settings and called exchange coding type preference settings such that the dialing node can make a selection in substantially the same way as a dialed node redundancy.

Preferably, the selected number changing node is called a Service Switching Point (SSP). Even more preferably, in step (2), the identity of the called exchange is determined by using the • · • · between the SSP and the Service Control Point (SCP). signaling contact.

t t «I · l · !!! Preferably, the calling center is a mobile switching center for a digital cellular network. Even more advantageously, the called center is also the mobile switching center of the digital mobile network. One or more of the MSCs or both may belong to PDC networks. However, I * / ··, however, is suitable for fixed-line networks and other digital cellular networks.

* If the MSCs are part of PDC networks, the * * mentioned preference settings may be either PSI-CELP or ··· VSELP Additionally, networks and MSCs may have the ability of 8 108767 I to use the default encoding type, namely, μ-law encoding.

Preferably, the call set-up message sent from the caller exchange to the selected number change node appropriately indicates the primary selection of the encryption type by setting the parameter to a User Service Information prime (USI '). The secondary selection of the encoding type may be similarly demonstrated by setting the parameter User Service Information (USI).

In case (5) states the encoding option | different from the primary selection indicated in the call set-up message, the USI parameter is transmitted unmodified to the called exchange. On the other hand, if the encoding selection matches the primary encoding type selection indicated in the call setup message, the USI parameter of the call setup message is replaced by the USI 'parameter.

I ·

Preferably, said call set-up message is a Initial Address Message (IAM).

> * «!!! According to another aspect of the invention, there is provided a device which, during a voice call setup phase between a caller exchange of a communication system and a called exchange, negotiates a type of code to control the call set-up procedure, ··, through a dialing node. caller; t <call center change number node, call setup message including call number and call center »*: 'at least the primary coding type selection identifier and the secondary encoding type selection identifier if the calling center has such a secondary selection; 9,108,767 means for receiving said call set-up message in a dial-up node and determining the identity of the called exchange on the basis of the dialed number; means for determining preference layouts of the coding type of the called exchange in the selected number changing node; means for determining a call coding type selection based on the called center coding type preference settings defined in the dialing node and the call center coding type selection / preference settings indicated in the call setup message; means for indicating in the call set-up message the selection of the primary coding type as the desired coding type if the call coding selection determined in the dialing node corresponds to the selection of the coding type indicated in the call set-up message or otherwise to indicate the desired coding type in the call setup message; and means for transmitting a call set-up message to the called exchange of the dialing node.

t <»I ·. According to a third aspect of the invention there is provided a method of determining the selection of a coding type in a dialing node of a selected number during a voice call setup between a communication system caller exchange and a called exchange, the method comprising the steps:,. (1) receive the call set-up message at the dialing number of the selected number »*, the call set-up message being transmitted from the calling exchange and including the called number and i · i I * h, at least the primary coding type selection identifier and the secondary coding type selection identifier such a secondary standard '··· * price; 108767 ίο (2) specifies the selected number in the change node in the call | knows the identity of the exchange based on the selected number and! the preferred center encoding type preference settings; (3) determining a call encoding type selection based on the SSP preferred coding type preference layouts and the call setup message address / address call center coding type preference layouts / preference layouts; (4) indicates if the call coding selection determined in step (3) corresponds to the primary coding type selection indicated in the call setup message, the primary coding type selection to the desired coding type in the call setup message, and otherwise indicates a secondary coding type! selecting the pin as the desired encoding type in the call setup message mass; and (5) transmitting a call set-up message from the selected number change node to the called exchange.

:,, Brief Description of Drawings * | »·> * * * ♦ ·» *.! For a better understanding of the invention and to illustrate how it may be implemented, reference will now be made to the accompanying drawings in which: * t ♦ t Figure 1 illustrates schematically a communication system in which a call set-up procedure can be routed through a service switching point; and FIG. 2 is a flowchart illustrating a call setup procedure in the system of FIG.

Detailed Description of Specific Embodiments «i» »1 ·

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1 · '* · Figure 1 illustrates a communication system comprising first and second cellular networks 1, 2. For purposes of the following disclosure, these networks 1, 2 are assumed to be Japanese standard PDC networks. Each of the networks 1, 2 comprises one or more exchanges, called "Mobile Switching Centers" (MSCs) 3, 4, which connect the calls to and from the mobile stations 5, 6. connected through the MSCr 3, 4 base station controller (BSC) 7, 8 and the base transceiver station (BTS) 9, 10 of their network.

The BTS 9, 10 is arranged in the "cell" where the mobile station 5, 6 is located, while the BSC 7,8 is associated with a small group of cells (and thus also the BTSs) including the one in which the mobile station 5 is located. , 6 located in.

The mobile station 5 requests a telephone connection by transmitting a SETUP message to the associated MSC 3 via BTS '9 and BSC 7. This message contains the called party number. Assuming that the called party number is provided corresponding to the subscriber traditional B-number and the called party is in a foreign network subscriber: large, that is, the network 2, the MSC 3 construct a call setup message (specifically IAM) for transmission to the MSC 4, the amount of which B- · ... · 'number prefix.

* · · ♦ «* v · As already explained, constructing an IAM involves determining the desired encoding type (i.e., PSI-CELP, VSELP, or μ-law) • · · Caller MSC 3 capabilities and selection, and called MSC 4 · · * Based on abilities. The latter are maintained in the ability database 11 associated with MSC 3. Suppose, for example, <that the caller MSC 3 is able to use both PSI-. '·. CELP and VSELP, but keeps PSI-CELP in the first place, and since the called MSC 4 is also able to use both PSI-CELP and VSELP, then the caller MSC 3 shows that they prefer 12 108767 PSI-CELP to IAM in the User Service Information parameter (USI). The IAM is then transmitted to the called MSC 4 via the interconnecting network 12. Note that after selecting the encoding type: after configuring and before IAM is transmitted, MSC 3! the amount required for a half rate channel the calling mobile station 5 to.

In the event that the called exchange 4 has an encoding selection that is the same as defined in the USI parameter, i.e. in this example, PSI-CELP, it sends the MAP message back to the caller MSC 3. The MAP message has two fields, the codec state. Codec status) and codec throughrate information. The first field is set to indicate the passage of the codec (codec through english.) (I.e., transmission from mobile to mobile without using code-conversion), while the latter field is set to indicate the half rate encoding (i.e., the PSI-CELP Ia). It will be clear to one skilled in the art how to set the MAP message fields for other preference layouts and capabilities.

The call set-up procedure described so far is in accordance with the conventional PDC set-up procedure. However, the formation procedure now described represents a change to that traditional procedure. Consider the case where the number dialed from the mobile station 5 is an 800 number or the like, i.e. it is associated with a specific service, such as a toll-free service or dialing. In such a case, the dialed number does not directly represent the subscriber of the network, but rather is a number that requires modification to determine such a subscriber number.

»· 108767 ϊ 13

Upon receipt of the 800-digit SETUP message, the caller MSC 3 builds an IAM message at the called exchange. However, when defining the encoding type preference settings, MSC 3 cannot identify the called center because this cannot be determined directly from the 800 number. Consequently, the caller MSC 3 places its own speech coding type selection (and assigns a channel for the calling mobile station 5) to the user service information parameter (USI ') with an apostrophe. The choice is either PSI-CELP or VSELP. The MSC calling the USI parameter also inserts a selection of an alternative speech coding type. If MSC 3 has only one choice, then this is placed in the USI parameter.

Of the selected 800 number, the caller MSC 3 recognizes that the original IAM destination is a service switching point (SSP) 13. The IAM is therefore transmitted to the SSP 13, where a change of the selected 800 number is performed to determine the B subscriber number to which the call must be routed. The SSP 13 is able to identify the called exchange 4 of the call using the modified B number prefix.

: · *: The SSP 13 has a capability database 11 corresponding to that of the caller MSC 3 (and of the called MSC 4). Upon receiving the »i ·: IAM caller from MSC 3, SSP 13 interrogates database 11 to determine the capabilities of the called MSC 4. In the event that the called MSC 4 is unable to support the selection of encoding types · ... · of the caller MSC 3 (as defined in the IAM USI 'parameter), the SSP leaves the ... * USI parameter unchanged. The USI' parameter can be dropped (although this is not essential as the called MSC 4 will ignore it anyway). The SSP 13 then forwards the IAM to the called exchange 4.

14 108767

In the event that the SSP query on the capability database 11 determines that the called MSC 4 is capable of supporting the calling MSC 3 encoding type selection (as defined in the IAM USI' parameter), the encoding type selection indication in the USI parameter is replaced by the SSP 13 USI' parameter selection. Again, the selection of the encoding type defined in the USI 'parameter can be dropped before forwarding the IAM to the called MSC 4.

The above process can be illustrated by an example. First, let's consider the case where the caller MSC 3 is able to use both PSI-CELP and VSELP and prioritize the use of PSI-CELP. In the IAM sent from MSC 3 to SSP 13, the USI 'parameter is set to indicate PSI-CELP, while the USI parameter is set to indicate VSELP. If the SSP 13 determines that the called exchange can only use VSELPs, the USI1 parameter may be dropped and the IAM transmitted to the called exchange 4 via the connecting network 12 '.

Now let us consider a similar case, except that SSP 13 determines that the called center 4 is capable of using both: PSI-CELP and VSELP. In this case, the USI parameter: is replaced by the USI 'parameter before the IAM is passed to the called ·'. * Known exchange 4.

After receiving the IAM, in the called MSC 4, the formation -'... · procedure continues in the conventional manner. This means that the called MSC 4 determines whether the selection defined in the USI parameter is the same as its own current price. If so, this is indicated in the returned MAP. * ··. message. If the signaling selection is not the same as that of the 15 108767 called MSCs 4, an alternative encoding type may be indicated in the MAP.

FIG. 2 is a flowchart illustrating the above-described procedure in which a call from one mobile station to another is routed through a service switching point.

One skilled in the art will recognize that various modifications may be made to the embodiment described above without departing from the scope of the invention. For example, although the above embodiment; The invention relates to a number change in a Gateway MSC (GMSC) of a cellular telephone network. When a call is made to a mobile subscriber, the call is routed to the subscriber's home network. The GMSC queries the Home Location Register (HLR) to determine the subscriber's location. Assuming that the subscriber is currently registered on a foreign network, GMSC will replace the telephone number with the visitor number obtained from the HLR. Again, it must be understood that the MSC of the caller may not know the foreign network: V · identity; deficiency which can be avoided by means of the invention.

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Claims (11)

A method for negotiating a coding type during a voice call setup between a communication system caller exchange and a called exchange, wherein the call set-up procedure is routed through a selected number change node, characterized by the steps of: (1) sending a call set up message at least the primary coding type selection token and the secondary coding type selection token of the exchange, if the calling party has such a secondary selection; (2) receiving said call set-up message at the number changing node and determining the identity of the called exchange based on the selected number; (3) determining the preference settings for the encoding type of the called exchange in the number changing node; (4) determine the selection of the coding type of the call based on the coding type specified by the switching node for the called switch center and the preference settings of the caller center indicated in the call setup message; (5) indicates if the call specified in step (4); the encoding V · selection corresponds to the V · primary encryption type selection indicated in the call setup message, the primary encryption type pin to the desired encoding type is the call encoding word • · · · · • · and otherwise indicates the secondary encoding type selection to the desired encoding type · *; mass, and '· ***: (6) sends a call set-up message from the number change node to the called exchange 17 108767 2. A method according to claim 1, characterized in that the calling center is a mobile switching center of a digital cellular network. 3. A method according to claim 1, characterized in that the called center is a Mobile Switching Center of a digital cellular network. Method according to claim 2 or 3, characterized in that one or both of the MSCs belong to PDC networks. A method according to claim 4, characterized in that said encoding type selections are either PSI-CELP or VSELP. t j i Method according to any one of the preceding claims, characterized in that the method comprises assigning a primary selection of the encoding type i. in the call set-up message sent from the caller's exchange to the number changing node, by setting the | ; according to the user service information parameter (USI '). • · · I I I A method according to claim 2, characterized in that said number changing node is a Service Switching Point (SSP). A method according to claim 6 or 7, characterized in that the method comprises detecting the secondary selection of the encoding type by setting a user-service information parameter (USI parameter). 18 108767 A method according to claim 8, characterized in that if in step (5) the call encoding selection is found to differ from the primary encoding type selection indicated in the call setup message, the USI parameter is transmitted to the called exchange unchanged, selection of the encoding type, the USI parameter is replaced by the USI 'parameter in the call setup message. 10. A device for encoding type negotiation with a voice call | during said communication between the caller exchange of the communication system and the called exchange, wherein the call set-up procedure is controlled through a dialing number change node, characterized in that the device comprises: means for sending a call set-up message from a calling exchange to a selected number changing node; ; : at least the primary encryption type selection ID and the caller secondary encryption type selection ID. ; 'if the calling center has such a secondary choice; V means for receiving said call set-up message in a dialing number changing node and determining therein the identity of the called center on the basis of the dialed number; I t t ·· * 'means for setting the preferred switching encoding type of the switching center: determination of the calls in the selected number changing node; '•' 'U means for dialing the selected number node to determine the size of the call type for the called exchange; * ^ · Based on the specified encoding type preference layouts and the caller center selection (s) indicated in the call setup message; means for indicating if the call coding selection determined in the dialing node of the selected number corresponds to the primary coding type selection indicated in the call setup message, the primary coding type selection to the desired coding type and means for transmitting a call set-up message from the selected number changing node to the called exchange. A method for determining encoding type selection in a dialing node of a dialed number during a voice call call setup between the calling system of the communication system and the called exchange, characterized in that the method comprises the steps of: (1) receiving a call setup message in a dialing message; :; the number transmitted from the exchange and including the dialed number and::: selecting at least the primary encoding type of the calling exchange; Identification IDs and secondary encoding type selection symbols if the caller exchange has such a secondary choice. \ * · (2) determine the identity of the called exchange in the selected number changing node based on the selected number, and the encoding type preference settings of the called exchange; (3) specify in SSP the call encoding type selection Kut - *: **; basic coding type preference settings assigned to the exchange and selection (s) of the coding type of the caller center indicated in the call setup message; ·. J tea; 108767 (4) indicates if the call coding selection determined in step (3) corresponds to the primary coding type selection indicated in the call setup message, the primary coding type selection to the desired coding type in the call setup message and otherwise indicating a secondary coding type selection to the desired coding message; and (5) transmitting a call set-up message from the selected number change node to the called exchange. i 2i 1 08767