Abstract:
Communications network node ( 5 ) configured to receive a called address string of a call destination and to output the called address string. The node comprises a processor ( 10 ) and a memory ( 12 ). The memory arranged to store at least one address string, and the processor configured to compare the called address string with the at least one stored address string. If the received called address string corresponds to one of the at least one stored address string the processor configured to cause the called address string to be output as a single signalling message.

Description:
TECHNICAL FIELD 
     The present invention relates generally to communications networks. 
     BACKGROUND 
     During establishment of a call connection from a caller communications device to a call recipient communications device signalling messages to communicate a called address string are sent from the media access gateway to a call agent or server. This signalling, however, can result in delays to establishing the call connection. We have realised that it would be advantageous to improve call connection establishment. 
     SUMMARY 
     According to one aspect of the invention there is provided a communications network node configured to receive a called address string of a call destination and to output the called address string. The node comprises a processor and a memory, the memory arranged to store at least one address string, and the processor configured to compare the called address string with the at least one stored address string. If the received called address string corresponds to one of the at least one stored address strings the processor configured to cause the called address string to be output as a single signalling message. 
     In one embodiment of the invention the communications node comprises an access gateway, and advantageously the gateway is configured to send a called address string to a call agent as a single signalling message, so reducing the time required for successful call connection. 
     Preferably the communications network node is configured to output the called address string in multiple signalling messages if the called address string does not correspond to one of the at least one of the stored address strings. Each signalling message comprises a subset of digits of the called address string. 
     The signalling messages are preferably signalling messages in accordance with DigitMap H.248 signalling or Session Initiation Protocol, SIP. 
     The memory is preferably arranged to store at least one previously called address string received by the node during a call establishment process. 
     The processor is preferably configured to store the called address string in the memory as a previously dialled address string if the processor determines that the called address string does not correspond to any of the stored address strings and the processor determines that a connection to a recipient communications device has been achieved using the address string. 
     The processor is preferably configured to determine that a called address string should be stored in the memory on receipt of a signal indicative that a connection has been achieved to the recipient communications device. 
     The memory is preferably arranged to store caller-specific address strings. 
     The processor is preferably arranged to associate in the memory a caller address string with address strings called by that caller. 
     The memory is preferably arranged to store a predetermined maximum number of validated address strings for each caller. 
     The memory may be arranged to store at least one address string available for use by the processor in respect of called address strings received from any of a plurality of caller address strings. 
     The communications node is preferably arranged to at least in part enable call establishment between a caller communications device and a call recipient communications device. 
     The communications node may conveniently comprise a gateway equipment. 
     According to another aspect of the invention there is provided a method for use in establishing a call connection between communications devices. The method comprises receiving a called address string of a call destination, comparing the received called address string with at least one stored called address string, and if the received called address string corresponds to one of the least one stored address string then outputting the called address string as a single signalling message. 
     The received called address string comprises a plurality of digits and the method preferably comprises receiving the digits one at a time. 
     Another aspect of the invention relates to machine-readable instructions for a processor of a communications network node, the instructions configured, when loaded onto the processor, to cause the processor to compare a received called address string to at least one stored previously called address string. If the received called address string corresponds to the at least one stored called address string the processor causes the node to output the called address string as a single signalling message. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  shows a communications network, 
         FIG. 2  shows a communications network node, 
         FIG. 3  shows a message signalling diagram, 
         FIG. 4  shows a message signalling diagram, and 
         FIG. 5  shows a flow diagram. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1  there is shown a telecommunications network  1  comprising a caller communications device  2  and recipient or called communications devices or terminals  3 ,  13  and  30 , network infrastructures  4   a ,  4   b ,  4   c  and  4   d , a media access gateway (AGW) node  5 , a call agent (CA) node  6  and a router  15 . During a call setup procedure in which a connection is established between two of the communications devices, suitable signalling between AGW  5  and CA  6  is performed so that the CA  6  can establish a through-connection to the communications device  3  via the router  15 . In broad terms, the functionality of the AGW  5  includes receiving a called address string, or number, comprising a plurality of digits, from the caller communications device  2  and forwarding this address string to the CA  6 . The CA  6  then analyses the received address string, causes ringing to be commenced at one of the recipient communications devices  3 ,  13  or  30  and then establishes a through-connection between the communications devices when the recipient answers. 
     The caller communications device  2  comprises a telephone of the type which uses Dual Tone Multi Frequency (DTMF) dialling or pulsed dialling (by way of a dial component). The router  15  communicates with the communications devices  3 ,  13  and  30  by way of the network infrastructures  4   b ,  4   c  and  4   d . The communications device  2  is connected to the AGW  5  via a subscriber line  9 , and the AGW  5  is connected to the (Internet Protocol-enabled) network infrastructure  4   a . The communications device  3  is a Voice over Internet Protocol (VoIP) enabled device which connects with the network infrastructure  4   b  by way of Session Initiation Protocol (SIP) over communications link  17 . The communications device  13  is connected to a media access gateway (AGW)  18  by subscriber line  19 . The AGW  18  communicates with the network infrastructure  4   c  on link  21  by way of Real-time Transport (RTP) and by way of DigitMap H.248 signalling. The communications device  30  communicates with an Access Network (AN)  24  via a subscriber line  25 , and the AN  24  communicates with a Media Gateway  26  over link  27  via Time Division Multiplexing (TDM). 
     As shown in  FIG. 2 , the AGW  5  comprises a processor  10  and a memory  12 . The operation of the processor  10  is determined by suitable machine-readable instructions, which may be stored in the memory  12 . As will be described below, the processor  10  causes validated called address strings received from the user communications device  2  to be stored in the memory  12 . In particular, the processor  10  is operative to cause called address strings to be stored in association with the address string of the caller communications device  2 . 
     Initially, the memory  10  contains no entries of validated dialled address strings, and a learning process then commences to learn validated address strings called by the communications device  2 . This procedure is shown in  FIGS. 3 and 5 . When the communications device  2  commences making a call to one of the recipient communications devices  3 ,  13  or  30 , the address string of the recipient communications device and the address string of the communications device  2  are sent across the network infrastructure  4   a  to the AGW  5 . When the communications device  2  goes ‘off-hook’, this is detected by the AGW  5 , and the AGW  5  notifies the CA  6  accordingly. The CA  6  then causes a dialling tone to be added to the communications device  2 . The AGW  5  then receives the digits of the called address string and those of the address string of the caller communications device  2 , one digit at a time. The processor  10  then retrieves a table from the memory  12  relating to validated called strings originating from the communications device  2 . At this initial stage, no validated numbers are stored in the table and so the processor  10  determines that the called string is to be sent to the CA  6  using DigitMap H.248 signalling. This involves sending multiple signalling messages, each message comprising a subset of the string of n digits, the subset comprising a predetermined number of digits k, as shown in  FIG. 3 . Once the CA  6  has received all of the digits, the CA  6  then analyses and processes the address string so that the connection can be made to the recipient communications device. The CA  6  is then able to confirm, or otherwise, that the address string is a valid address string by detecting when ringing commences of the recipient communications device, and an acceptance signalling message containing confirmation that the address string is valid (i.e. it is complete and is not a faulty number) is then sent to the AGW  5 . Therefore, CA  6  outputs the acceptance signalling message if it achieves a connection to the recipient communications device  3 . On receipt of such acceptance/validation signalling message, the processor  10  is then operative to cause the called address string to be stored in the memory  12  as a validated address string, associated with the address string of the caller communications device  2 . 
     Turning now to  FIG. 4 , there is shown the sequence of signalling, which takes place subsequent to the signalling in  FIG. 3 , in which the caller communications device  2  wishes to make a call to the communications device called previously. On receipt of the called address string, the processor  10  compares the called address string to the validated address strings stored in the memory  12  associated with the address string of the user communications device  2 . The processor  10  determines that the called address string matches an address string stored in the memory  12 . The processor  10  then causes the called address string stored in the memory  12  to be sent to the CA  6  as a single signalling message, namely all digits 1 to n of the address string are sent to the CA  6 . 
     Advantageously, in the case of multiple users, the memory  12  stores a table of validated address strings for each user (or rather for each originating address string). By arranging that each user has his own table (or put another way that the memory stores caller-specific tables) the processing required by the processor  10  in determining whether a match exists is considerably reduced as compared to if the processor needed to review all of the validated address strings stored in the memory  12 . The AGW  5  could be arranged such that each user is allocated a predetermined maximum number of validated address strings which can be stored in the memory  12 . When the processor  10  encounters an address string which is not present in the memory  12 , but which has been accepted by the CA  6 , and the predetermined number of stored address strings for that caller has been reached, the processor  10  will cause one of the stored validated address strings (which could for example be the least used or oldest address string) to be replaced by the ‘new’ dialed address string. 
       FIG. 5  shows a flow diagram  100  of the various steps performed by the processor  10 . At step  101  the processor receives a called address string. The processor  10  then retrieves the respective table of validated address strings for that caller and compares the called address string to those stored address strings, as shown at steps  102  and  103 . At step  104  the processor  10  determines if the called address string is a validated (previously) called address string. If it is, then the address string is sent to the CA  6  as a single signalling message, as shown at step  105 . Otherwise, the processor  10  sends the address string as multiple signalling messages (at step  106 ). If the processor then receives confirmation (at step  107 ) from the CA  6  that a through connection has been achieved with the address string then the processor stores the address string as a validated address string, as shown at step  108 . 
     It will be appreciated that although in the above described embodiment the memory  10  is initially empty, and is populated subsequently by the learning process described above, in another embodiment the memory  10  may be pre-loaded with one or more address strings, which are immediately available to the processor  10  for use in comparing against a called address string, prior to any further address strings being added as a result of the learning process. 
     It will also be appreciated that certain address strings are likely to be needed by multiple callers, such as the address strings for emergency services, transportation services and social/community services. Such numbers may advantageously be stored in the memory  12  as a table of shared address strings, which table may be created by the network administrator or service provider. The processor  10  can then compare a dialled address string to both the address strings in the caller-specific table as well as in the shared table. 
     The AGW  5  is advantageously able to send received digits of a called address string and send the digits as fast as possible to the CA  6  using fewer signalling messages. This is particularly advantageous in the case mentioned above in which the called address string is sent to the AGW  5  by the communications device  2  one digit at a time. Another important advantage of the above embodiment is that no changes are required to the existing H.248 DigitMap signalling procedure. Therefore use of the DigitMap signalling can be continued and act as the default in the instance that a called address string is not stored in the memory  12 . 
     It will be appreciated that although particular mention above has been made H.248 signalling in relation to an access gateway, other embodiments of the invention may include a gateway equipment which converts Time Division Multiplexed (TDM) signals and H.248 or SIP signals.