Abstract:
A third UE calls the second UE, however, the second UE is on a call with a first UE, then the call controlling device provides a voice message from said third user equipment as a background voice message to the second user equipment while keeping the call between the first user equipment and the second user equipment. The “background” in the background voice message is relative to the original call, and does not have any other special meanings. Since the original call between the first UE and the second UE is not affected, for the second UE, or a second user that uses the second UE, the voice message from the third UE is a background voice message.

Description:
FIELD OF THE INVENTION 
     The invention relates to a method and device for providing user equipment with voice messages. 
     BACKGROUND OF THE INVENTION 
     When the calling party calls a called party, if the called party is on a call (also called as busy), then the call from the calling party will be rejected or the call from the calling party will be forwarded by the call controlling device, for example, the telephony application server (TAS) or switch, in the network to the voice message server (VMS) of the called party, so that the calling party can send a voice message to the voicemail box of the called party. The VMS receives and stores the voice message, then the VMS sends a voicemail message waiting indicator to the user equipment (UE) of the called party to prompt the called party to check the voice message. When the call of the called party ends, the called party communicates with the VMS to check the voice message according to the voicemail message waiting indicator from the VMS. 
     SUMMARY OF THE INVENTION 
     When a user is on a voice call, a long voice call in particular, for example, a telephone conference, he/she may not be able to check voicemail in his/her voicemail box, and may miss important ones which need immediate action. Aimed at the above mentioned problem, it would be advantageous to propose a technical solution of providing a second user equipment (UE) which is on a call with a first UE with a voice message from a third UE: the third UE calls the second UE, however, the second UE is on a call with a first UE, then the call controlling device provides a voice message from said third UE as a background voice message for the second UE while keeps the call between the first UE and the second UE. The word “background” in the background voice message is just relative to the original call, and does not have any other special meanings. Since the original call between the first UE and the second UE is not affected, for the second UE, or a second user that uses the second UE, the voice message from the third UE is a background voice message. 
     According to an embodiment of the present invention, there is provided a method, in a call controlling device in telecommunication networks, for providing a second UE which is on a call with a first UE with a voice message from a third UE, comprising: receiving a first request message from said third UE, said first request message configured to request to establish a call between said third UE and said second UE; detecting whether said second UE is on a call with said first UE; and if said second UE is on a call with said first UE, providing a voice message from said third UE as a background voice message for said second UE while keeping said call between said first UE and said second UE. 
     According to another embodiment of the present invention, there is provided a method, in a voice message server (VMS) in telecommunication networks, for providing a second UE which is on a call with a first UE with a voice message from a third UE, comprising: receiving a third request message from a call controlling device, said third request message configured to request to establish a call between said VMS and said third UE; and sending a sixth request message to said second UE, said sixth request message configured to request to establish a call between said VMS and said second UE. 
     According to another embodiment of the present invention, there is provided a first providing device in a call controlling device in telecommunication networks, for providing a second UE which is on a call with a first UE with a voice message from a third UE, comprising: a first receiving means configured to receive a first request message from said third UE, said first request message configured to request to establish a call between said third UE and said second UE; a detecting means configured to detect whether said second UE is on a call with said first UE; and a background voice providing means configured to provide a voice message from said third UE as a background voice message fir said second UE while keeping said call between said first UE and said second UE, if said second UE is on said call with said first UE. 
     According to another embodiment of the present invention, there is provided a second providing device in a VMS in telecommunication networks, for providing a second UE which is on a call with a first UE with a voice message from a third UE, comprising: a second receiving means configured to receive a third request message from a call controlling device, said third request message configured to request to establish a call between said VMS and said third UE; and a second sending means configured to send a sixth request message to said second UE, said sixth request message configured to request to establish a call between said VMS and said second UE. By using the methods and devices provided by the present invention, the second user (corresponding to the second UE) who is on a call with the first user (corresponding to the first UE) can hear the voice message from the third user (corresponding to the third UE) promptly. If the voice message indicates an event with high priority or of great importance, the second user can promptly handle the event indicated by the voice message. Besides, since only the second user can hear the voice message from the third user, while the first user whom the second user is on a call with can not hear the voice message from the third user, the privacy of the second user can be protected. Further, in the technical solution of the present invention, the original call between the first user and the second user is kept, and the first user cannot hear the voice message from the third user; therefore the user experience of the first user is very good. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features, aspects and advantages of the present invention will become obvious by reading the following description of non-limiting embodiments with reference to the appended drawings. 
         FIG. 1  shows a network topological diagram of an IP Multimedia Subsystem (IMS)-based system architecture according to an embodiment of the present invention; 
         FIG. 2(   a ) shows a flow chart, in a call controlling device in telecommunication networks, of providing a second UE which is on a call with a first UE with a voice message from a third UE, according to an embodiment of the present invention; 
         FIG. 2  ( b ) shows a schematic flowchart of the substep S 203  shown in  FIG. 2(   a ); 
         FIG. 3  shows a systematic signal flowchart, in a TAS  22  shown in  FIG. 1 , of providing a second US which is on a call with a first UE with a voice message from a third UE according to an embodiment of the present invention; 
         FIG. 4  shows a systematic signal flowchart of a method, in a serving-call session control function (S-CSCF) entity  32  shown in  FIG. 1 , of providing a second UE which is on a call with a first UE with a background voice message from a third UE according to another embodiment of the present invention; 
         FIG. 5  shows a systematic signal flowchart of a method, in a VMS  42  shown in  FIG. 1 , of providing a second UE which is on a call with a first UE with a voice message from a third UE according to an embodiment of the present invention; 
         FIG. 6  shows a topological diagram of a circuit-switched based telecommunication network according to an embodiment of the present invention; 
         FIG. 7  shows a No. 7 signal flowchart, in a VMS  92  shown in  FIG. 6 , of providing a second UE which is on a call with a first UE with a background voice message from a third UE according to another embodiment of the present invention; 
         FIG. 8  shows a topological diagram of a circuit-switched based wireless telecommunication network; 
         FIG. 9  shows a block diagram of a first providing device  900  in a call controlling device in telecommunication networks, for providing a second UE which is on a call with a first UE with a voice message from a third UE, according to an embodiment of the present invention; 
         FIG. 10  shows a block diagram of a second providing device  1000  in a VMS in telecommunication networks, for providing a second UE which is on a call with a first UE with a voice message from a third UE, according to an embodiment of the present invention; wherein, same or similar reference numerals refer to the same or similar steps or means. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The illustrative description of the embodiments of the present invention will be given in details combined with FIGS. 
       FIG. 1  shows a network topological diagram of an IP Multimedia Subsystem (IMS)-based system architecture, which shows a second UE  12 , a proxy-call session control function (P-CSCF) entity  52 , an interrogating-call session control function (I-CSCF) entity  62 , a serving-call session control function (S-CSCF) entity  32 , a voice message server (VMS)  42 , a telephony application server (TAS)  22 , and a home subscriber server (HSS)  72  in home networks; a third UE  13 , a P-CSCF entity  53 , an I-CSCF entity  63 , a S-CSCF entity  33 , a VMS  43 , a TAS  23  and a HSS  73  in home networks: a first UE  11 , a P-CSCF entity  51 , an I-CSCF entity  61 , a S-CSCF entity  31 , a VMS  41 , a TAS  21  and a HSS  71  in home networks. 
       FIG. 2(   a ) shows a flow chart, in a call controlling device in telecommunication networks, of providing a second UE which is on a call with a first UE with a voice message from a third UE, according to an embodiment of the present invention. 
     Taking it as an example that the second UE  12  and first UE  11  are on a call, and the third UE  13  calls the second UE  12  as shown in  FIG. 1 , the process of the call controlling device providing the second UE  12  with the voice message from the third UE  13  is described in detail. In this application scenario, the call controlling device can be the TAS  22  or the S-CSCF entity  32  in the home network of the second UE  12 . 
     First, in step S 201 , the call controlling device receives a first request message from the third UE  13  requesting to establish a call with the second UE  12 . The request message can be an INVITE message or an IAM (Initial Address Message), which will be taken as an example as follows. 
     Then, in step S 202 , the call controlling device detects whether the second UE  12  is on a call with the first UE  11 . Since the second UE  12  is on a call with the first UE  11 , the call controlling device detects that the second UE  12  is busy. Here, it should be noted that the first UE  11  refers to any UE in general, instead of a specific UE. 
     Then, in step S 203 , if the second UE  12  is on a call with the first UE  11 , the call controlling device provides the voice message from said third UE  13  as a background voice message for the second UE  12  while keeps the call between the first UE  11  and the second UE  12 . 
     In one embodiment, the step S 203  can be implemented by the two substeps shown in  FIG. 2(   b ). First, in step S 2031 , the call controlling device sends a second request message to the VMS  42 , and the second request message is used to request to establish a call between the third UE  13  and the VMS  42 ; and sends a third request message to the third UE  13 , and the third request message is used to request to establish a call between the VMS  42  and the third UE  13 . The call between the VMS  42  and the third UE  13  is used by the third UE  13  to send the voice message destined to the second UE  12  to the VMS  42 . 
     Then, in step S 2032 , the call controlling device sends a fourth request message to the VMS  42 , the fourth request message is configured to request to establish a call between the second UE  12  and the VMS  42 ; and sends a fifth request message to the second UE  12 , said fifth request message is configured to request to establish a call between the VMS  42  and the second UE  12 . The call between the VMS  42  and the second UE  12  is used by the VMS  42  to send the voice message from the third UE  13  to the second UE  12 . 
     It should be noted that, for the call controlling device, the step S 2031  is optional. For example, in case that the call controlling device is the S-CSCF entity  32  in  FIG. 1 , the step S 2031  can be implemented by other devices, for example, the TAS  22 , therefore, the S-CSCF entity  32  does not need to implement step S 2031 . 
     Then, after step S 2032 , the call controlling device receives a response message from the third UE  13  responding to the third request message and a response message from the VMS  42  responding to the second request message. Of course, if the call controlling device does not need to implement step S 2031 , it will not receive the two response messages. The two response messages indicate that the voice channel between the third UE  13  and the VMS  42  can be established, then, the voice channel between the third UE  13  and the VMS  42  is established, and the third UE  13  sends the voice message to the VMS  42 . 
     After step S 2032 , the call controlling device receives a response message from the second UE  12  and a response message from the VMS  42  respectively. The two response messages indicate that the voice channel between the second UE  12  and the VMS  42  can be established, then, the voice channel between the second UE  12  and the VMS  42  is established, and the VMS  42  sends the voice message from the third UE  13  to the second UE  12 . 
     It should be noted that the step S 2032  and the step S 2031  can be implemented simultaneously. Alternatively, the step S 2032  can be implemented after the call controlling device receives the response message from the third UE  13  that responds to the third request message and the response message from the VMS  42  that responds to the second request message. 
     Optionally, before step S 203 , the call controlling device can further determine whether the second UE  12  subscribes to a service for receiving the voice message from the third UE  13  when the second UE  12  is on the call with the first UE  11 . If the second UE  12  subscribes to said service, step  203  and its subsequent steps are executed. For example, the second UE  12  can set that it can receive the voice message from other UEs unconditionally during a call. Optionally, the second UE  12  can preset some service strategies, for example, the second UE  12  can set in advance that it can receive the voice message from some specific UEs in the call during some specific periods; or the second UE  12  set whether to listen to the voice message or to leave a message according to the its own location and the calling party (i.e., the one that leave a message)&#39;s location; or, the second UE  12  can set the priority of other users, when it is on a call with a UE with a higher priority, it will not receive the voice message from the UE with a lower priority; when it is on a call with a UE with a lower priority, it will receive the voice message from the UE with a higher priority. 
     Optionally, if the call controlling device needs to execute step S 2031 , then before step S 2031 , it can further determine whether the second UE  12  subscribes to the voice message service, if the second UE  12  subscribes to the voice message service, the step S 2031 , step S 2032  and the subsequent steps are executed. 
       FIG. 3  shows a systematic signal flowchart, in a TAS  22  shown in  FIG. 1 , of implementing the function of the call controlling device shown in  FIG. 2(   a ) based on SIP protocol. The systematic signal flowchart of  FIG. 3  will be described in detail with reference to  FIG. 1 . 
     First, in step S 301 , the second UE  12  and the first UE  11  are in voice session. The voice session is established based on Real time Transport Protocol (RTP). 
     In step S 302 , the third UE  13  calls the second UE  12 , the third UE  13  sends a first request message to request to establish a call with the second UE  12 . that is, a first INVITE message, to the second UE  12 . The first INVITE message includes the session description of the third UE  13  based on Session Description Protocol (SDP), which includes the session IP address of the third UE  13 . the supported media format and type, the session ID, the session version, net type, and address type, and other parameters. 
     The first INVITE message is sent by the third UE  13 , routed by the P-CSCF entity  53  and S-CSCF entity  33  in the home network of the third UE  13  and the backbone network, reaches I-CSCF entity  62  in the home network of the second UE  12 , and is forwarded by the I-CSCF entity  62  to the S-CSCF entity  32 . and the S-CSCF entity  32  sends the first INVITE message to the TAS  22 . After the TAS  22  sends the first INVITE message to the S-CSCF entity  32 , the S-CSCF entity  32  forwards it to the second UE  12  via the P-CSCF entity  52 . 
     Since the second UE  12  is on the call with the first UE  11 , therefore, after receiving the first INVITE message, the second UE  12  returns a busy message in step S 303 , and the busy message reaches the S-CSCF entity  32  via the P-CSCF entity  52 , and the S-CSCF entity  32  sends the busy message to the TAS  22 . 
     In step S 304 , the TAS  22  determines whether the second UE  12  subscribes to the voice message service. Usually the information that the second UE  12  subscribes to the voice message is stored in the HSS  72 . The TAS  22  looks up the HSS  72  to determine whether the second UE  12  subscribes to the voice message. Optionally, the TAS  22  can pre-store the information about whether the second UE  12  subscribes to the voice message service. 
     If the second UE  12  subscribes to the voice message service, then, in step S 305 , the TAS  22  sends a second INVITE message to the VMS  42 . The second INVITE message includes the session description of the third UE  13  based on SDP protocol, which includes the session IP address of the third UE  13 , the supported media format and type, the session ID, the session version, network type, and address type, and other parameters. 
     Then, in step S 306 , the TAS  22  receives the 200 OK message from the VMS  42  which responds to the second INVITE message in step S 305 . The 200 OK message includes the session description of the VMS  42  based on SDP protocol, which includes the session IP address of the VMS  42 , the supported media format and type, the session ID, the session version, network type, and address type, and other parameters. 
     Then, in step S 307 , the TAS  22  sends a third (Re) INVITE message to the third UE  13  via S-CSCF entity  32  to request to establish a call between the third UE  13  and the VMS  42 . The (Re) INVITE message sets the called party as the VMS  42 , and it includes the session description of the VMS  42  based on SDP protocol, which includes the session IP address of the VMS  42 , the supported media format and type, the session ID, the session version, net type, and address type, and other parameters. 
     Then, in step S 308 , the TAS  22  receives the 200 OK message which responds to the third (Re) INVITE message from the third UE  13  forwarded by the S-CSCF entity  32 . 
     In step S 309 , after the VMS  42  and the third UE  13  respectively receive session description of each other based on SDP, the voice channel between the two is established, and the third UE  13  can send the voice message that is to be left fir the second UE  12  to the VMS  42 , which will be described in detail in the following step S 318 . 
     Then, in step S 310 , the third UE  13  sends an ACK message, and the ACK message reaches the VMS  42  via S-CSCF entity  32 , TAS  22  and S-CSCF entity  32 . 
     Then, in step S 311 , the TAS  22  determines whether the second UE  12  subscribes to the service for receiving the voice message from the third UE  13  when the second UE  12  is on a call with the first UE  11 . Optionally, as discussed above, the TAS  22  can determine whether the second UE  12  receives the voice message from the third UE  13  when the second UE  12  is on the call with the first UE  11 , based on a service strategy preset by the second UE  12 . 
     If the second UE  12  subscribes to the service, the subsequent steps are executed. 
     In step S 312 , the TAS  22  sends a fourth INVITE message to the VMS  42  to request to establish a call between the second UE  12  and the VMS  42 . The fourth INVITE message includes the session description of the second UE  12  based on SDP protocol, which includes the session IP address of the second UE  12 , the supported media format and type, the session ID, the session version, network type, and address type, and other parameters. 
     Then, in step S 313 , the VMS  42  sends a 200 OK message which responds to the fourth INVITE message. The 200 OK message reaches the TAS  22  via the S-CSCF entity  32 . 
     In step S 314 , the TAS  22  sends a fifth (Re)INVITE message to the second UE  12  to request to establish a call between the second UE  12  and the VMS  42 . The fifth (Re)INVITE message includes the session description of the VMS  42  based on SDP protocol, which includes the session IP address of the VMS  42 , the supported media format and type, the session ID, the session version, network type, and address type, and other parameters. 
     Then, in step S 315 , the second UE  12  sends a 200 OK message which responds to the fifth INVITE message. 
     In step S 316 , after the VMS  42  and the second UE  12  respectively receive session description of each other based on SDP, the voice channel between the two is established, and the VMS  42  can send the voice message from the third UE  13  to the second UE  12 . 
     Then, in step S 317  the second UE  12  sends an ACK message, and the ACK message reaches the VMS  42  via S-CSCF entity  32 . 
     In step S 318 , the third UE  13  sends the voice message to the VMS  42 . In step S 319 , the VMS  42  sends the voice message from the third UE  13  to the second UE  12 . Usually, the establishment of the voice channel between the UE  13  and the VMS  42  is earlier than the establishment of the voice channel between the UE  12  and the VMS  42 . Therefore, the VMS  42  may need to register the voice message from the third UE  13 . 
     Optionally, the volume for the second UE  12  to play the voice message can be set by the VMS  42 . The second UE  12  can set in advance the volume for the second UE  12  to play the voice message from different UEs. Usually, in order to bring interference as small as possible to the call between the second UE  12  and the first UE  11 , the VMS  42  can set the voice message to be played at a lower volume in the second UE  12 . Of course, the voice message from a specific UE can be set to be played at a higher volume according to the preset of the second UE  12 . 
     In step S 320 , the third UE  13  sends a BYE message to terminate the call with the VMS  42 , that is, finish sending the voice message. In step S 321 , the VMS  42  sends a BYE message to terminate the call with the second UE  12 , that is, finish sending the voice message. 
     It should be noted that, the flowchart shown in  FIG. 3  is only illustrative. In different embodiments, the executing order for each step may differ from that shown in the flowchart of  FIG. 3 . For example, the order of step S 305  and step S 307  does not matter, that is the step S 307  and the step S 305  can be executed simultaneously, or the step S 307  can be executed prior to the step S 305 . Similarly, the order of step S 312  and step S 314  does not matter. 
     Besides, the step S 304  and step S 311  are optional. In some embodiment, it is not necessary to determine whether the second UE  12  subscribes to the voice message service or whether the second UE  12  subscribes to the service to listen to the voice message during a call. The 200 OK messages and ACK messages shown in  FIG. 3  are all optional. 
     It should also be noted that, for the establishment of a call in  FIG. 3 , only one INVITE message is illustrated for determining the establishment of the voice channel. If the session parameters between the two communicating parties are not consistent, more rounds of the INVITE messages for consultation are needed, the details of which can refer to the IETF RFC  3261  and RFC  4566  and are not repeated here. 
     The TAS  22  is taken as an example above to describe in detail the process for it to provide the voice message from the third UE  13  to the second UE  12  which is on a call with a first UE  11 . The S-CSCF entity  32  will be taken as an example in the follows to describe in detail the process for it to provide the voice message from the third UE  13  to the second UE  12  which is on a call with a first UE  11 . 
       FIG. 4  shows a signal flowchart, in an S-CSCF entity  32 , of providing a second UE  12  which is on a call with a first UE  11  with a voice message from a third UE  13 . 
     The steps S 401  to S 410  prior to the step S 411  correspond to the steps S 301  to S 310  in  FIG. 3  in a one-to-one manner, and are not repeated here. 
     In step S 411 , the S-CSCF entity  32  determines whether the second UE  12  subscribes to the service to listen to the voice message from the third UE  13  when the second UE  12  is on a call with the first UE  11 . 
     If the second UE  12  subscribes to the service, the subsequent steps are executed. 
     In step S 412 , the S-CSCF entity  32  sends a fourth INVITE message to the VMS  42  to request to establish a call between the second UE  12  and the VMS  42 . The fourth INVITE message includes the session description of the second UE  12  based on SDP protocol, which includes the session IP address of the second UE  12 , the supported media format and type, the session ID, the session version, net type, and address type, and other parameters. 
     Then, in step S 413 , the VMS  42  sends a 200 OK message which responds to the fourth INVITE message forwarded by the TAS  22  to the S-CSCF entity  32 . 
     Then, in step S 414 , the S-CSCF entity  32  sends a fifth (Re) INVITE message to the second UE  12  to request to establish a call between the second UE  12  and the VMS  42 . The fifth (Re)INVITE message includes the session description of the VMS  42  based on SDP protocol, which includes the session IP address of the VMS  42 , the supported media format and type, the session ID, the session version, network type, and address type, and other parameters. 
     Then, in step S 415 , the second UE  12  sends a 200 OK message which responds to the fifth INVITE message to the S-CSCF entity  32 . 
     In step S 416 , after the VMS  42  and the second UE  12  respectively receive session description of each other based on SDP, the voice channel between the two is established, and the VMS  42  can send the voice message from the third UE  13  to the second UE  12 . 
     Then, in step S 417 , the second UE  12  sends an ACK message, and the ACK message reaches the VMS  42  via the S-CSCF entity  32 . 
     In step S 418 , the third UE  13  sends a voice message to the VMS  42 . In step S 419 , the VMS  42  sends the voice message from the third UE  13  to the second UE  12 . 
     In step S 420 , the third UE  13  sends a BYE message to terminate the call with the VMS  42 , that is, finish sending the voice message. In step S 421 , the VMS  42  sends a BYE message to terminate the call with the second UE  12 , that is, finish sending the voice message. 
     In an embodiment, the function realized by the signal flowchart shown in step S 311  to step S 315  or step S 411  to step S 415  also can be accomplished by the VMS  42 .  FIG. 5  shows a signal flowchart, in the VMS  42 , of providing a second UE  12  which is on a call with a first UE  11  with a voice message from a third UE  13 . 
     The steps S 501  to S 510  correspond to the steps S 301  to S 310  in  FIG. 3  in a one-to-one manner, and are not repeated here. 
     In step S 511 , the VMS  42  determines whether the second UE  12  subscribes to the service to listen to the voice message from the third UE  13  when the second UE  12  is on a call with other UEs. 
     If the second UE  12  subscribes to the service, the subsequent steps are executed. 
     In step S 512 , the VMS  42  sends a sixth (Re) INVITE message to the second UE  12  to request to establish a call between the second UE  12  and the VMS  42 . The sixth (Re)INVITE message includes the session description of the VMS  42  based on SDP protocol, which includes the session IP address of the VMS  42 , the supported media format and type, the session ID, the session version, network type, and address type, and other parameters. 
     Then, in step S 513 , the second UE  12  sends a 200 OK message which responds to the sixth (Re) INVITE message to the VMS  42 . The 200 OK message includes the session description of the second UE  12  based on SDP protocol, which includes the session IP address of the second UE  12 , the supported media format and type, the session ID, the session version, network type, and address type, and other parameters. 
     In step S 514 , after the VMS  42  and the second UE  12  respectively receive session description of each other based on SDP, the voice channel between the two is established, and the VMS  42  can send the voice message from the third UE  13  to the second UE  12 . 
     Then, in step S 515 , the second UE  12  sends an ACK message, and the ACK message reaches the VMS  42  via the S-CSCF entity  32 . 
     In step S 516 , the third UE  13  sends the voice message to the VMS  42 . In step S 517 , the VMS  42  sends the voice message from the third UE  13  to the second UE  12 . 
     In step S 518 , the third UE  13  sends a BYE message to terminate the call with the VMS  42 , that is, finish sending the voice message. In step S 519 , the VMS  42  sends a BYE message to terminate the call with the second UE  12 , that is, finish sending the voice message. 
     The network topology of the IMS architecture shown in  FIG. 1  is taken as an example to elucidate the process for the call controlling device or the VMS  42  of providing a voice message from the third UE  13  to the second UE  12  while keeping the call between the first UE  11  and the second UE  12 . It should be noted that the flow charts shown in  FIG. 3  to  FIG. 5  are illustrative, for different network topologies, the specific implementing steps are different, and those skilled in the art can introduce the technical solution of the present invention to other network topologies based on the shown flowcharts. Besides, the TAS  22 , the S-CSCF entity  32  and the VMS  42  are divided in terms of their functionality, in practical implementation, one or more above functional entities can be integrated into one hardware device for implementation, meanwhile, some of the interactive steps among the functional entities can be omitted car he implemented with internal control protocol. 
     The circuit-switched based fixed telecommunication network shown in  FIG. 6  is taken as an example, to elucidate the process for the VMS of providing a second UE  12  which is on a call with a first UE  11  with a voice message from a third UE  13 . 
       FIG. 6  shows a topological diagram of a circuit-switched based telecommunication network. In  FIG. 6 , the second UE  12  and the switch  82  and the VMS  92  in its home network, the third UE  13  and the switch  83  in its home network, and the first UE  11  and the switch  81  in its home network are shown. Those skilled in the art can understand, the topology in  FIG. 6  is only illustrative, the home network of each UE can also include other devices, such as access devices, the home network of the third UE  13  may also include a VMS, since they are not directly related to the object of the present invention, they are not listed one by one. 
       FIG. 7  shows a No. 7 signal flowchart, in a VMS  92 , of providing a second UE  12  which is on a call with a first UE  11  with a voice message from a third UE  13 . The signal flowchart shown in  FIG. 7  will be described in detail with reference to  FIG. 6 . 
     First, in step S 701 , the voice session between the second UE  12  and the first UE  11  is being carried out. The voice session is established on the ISDN User Part (ISUP) standard. 
     Then, in step S 702 , the third UE  13  calls the second UE  12 . The third UE  13  sends an IAM message to the second UE  12  requesting to establish a call with the second UE  12 , and the IAM message includes the number of the second UE  12 . 
     The IAM message is sent out by the third UE  13 , routed through the circuit-switched network via the switch  83  in the home network of the third UE  13 , and reaches the switch  82  in the home network of the second UE  12 . 
     Since the second UE  12  is on a call with the first UE  11 , therefore, after receiving the IAM message, in step S 703 , the switch  82  detects that the second UE  12  is on a call, then, it determines whether the second UE  12  subscribes to a voice message service. 
     If the second UE  12  subscribes to the voice message service, then, in step S 704 , the switch  82  sends a REDREQ (Redirection Request) message to the switch  83 , to inform the switch  83  that the second UE  12  is busy, and the IAM message is redirected to the VMS  92 . 
     In step S 705 , the switch  83  sends a redreq message (the response message to the REDREQ message) to the switch  82 . 
     In step S 706 , the switch  83  sends a REL (Release) message to the switch  82 . 
     In step S 707 , the switch  83  sends an IAM message to the VMS  92 , and the IAM message is used to request to establish a call between the third UE  13  and the VMS  92 . 
     In step S 708 , the VMS  92  sends an ACM (Address Complete Message) to the third UE  13  via the switch  83 . 
     In step S 709 , the VMS  92  sends an ANM (Answer Message) to the third UE  13  via the switch  83 . 
     Subsequently, in step S 710 , the voice channel between the VMS  92  and the third UE  13  is established, and the third UE  13  can send the voice message to be left for the second UE  12  to the VMS  92 . 
     Then, in step S 711 , the VMS  92  determines whether the second UE  12  subscribes to the service for receiving the voice message from the third UE  13  when the second UE  12  is on a call with the first UE  11 . 
     If the second UE  12  subscribes to the service, the subsequent steps are executed. 
     Then, in step S 712 , the VMS  92  sends an IAM message to the second UE  12  requesting to establish a call with the second UE  12 . 
     Then, in step S 713 , the second UE  12  sends an ACM message to the VMS  92 . 
     In step S 714 , the second UE  12  sends a (Pseudo) ANM message to the VMS  92 . 
     In step S 715 , the voice channel between the VMS  92  and the second UE  12  is established, and the VMS  92  can send the voice message from the third UE  13  to the second UE  12 . 
     Then, in step S 716 , the third UE  13  sends the voice message to the VMS  92 . In step S 717 , the VMS  92  sends the voice message from the third UE  13  to the second UE  12 . 
     In step S 718 , the third UE  13  sends a REL message to terminate the call with the VMS  92 , that is, finish sending the voice message. In step S 719 , the VMS  92  sends a REL message to terminate the call with the second UE  12 , that is, finish sending the voice message. 
     The process, in the VMS  92  in a circuit-switched based telecommunication network, of providing the second UE  12  which is on a call with the first UE  11  with a voice message from the third UE  13  is described in detail with the signal flowchart shown in  FIG. 7 . It should be noted that, the signal flowchart shown in  FIG. 7  is only illustrative, there are many modifications based on this. For example, the step S 711  is optional, the VMS  92  can execute step S 712  after receiving the IAM message in step S 707  without determining. The execution order of step S 708  and step S 711  (or step S 712 ) doesn&#39;t matter. Besides, if the second UE  12  and the third UE  13  do not support No. 7 signaling, then the transporting of other signals can be implemented between the second UE  12  and the switch  82 , as well as the third UE  13  and the switch  83 . 
     For the circuit-switched based wireless telecommunication network shown in  FIG. 8 , the mobile switch center (MSC) corresponding to the UE can be implemented to realize the function of the VMS  92  in  FIG. 7 , referring to the flowchart shown in  FIG. 7 . 
     The process when the second UE  12  is located in its home network and is on a call with the first UE  11 , the call controlling device or the VMS provides it with the voice message from the third UE  13  is described in detail. For the case when the second UE  12  is roaming, the process for the call controlling device in the roaming area to provide the voice message from the third UE  13  is similar to that above, and is not repeated here. 
       FIG. 9  shows a block diagram of a first providing device  900  in a call controlling device in telecommunication networks, for providing a second UE which is on a call with a first UE with a voice message from a third UE, according to an embodiment of the present invention. In  FIG. 9 , the first providing device  900  includes a first receiving means  901 , a detecting means  902 , a first determining means  903  and a background voice providing means  904 . 
     Without loss of generality, the network topology shown in  FIG. 1  and the case that the second UE  12  and the first UE  11  are on a call, and the third UE  13  calls the second UE  12  is taken as an example to describe in detail the process of the first providing device  900  in the call controlling device for providing the second UE  12  with a voice message from the third UE  13 . In the application scenario, the call controlling device can be the TAS  22  or the S-CSCF entity  32  in the home network of the second UE  12  in  FIG. 1 . 
     First, the first receiving means  901  receives a first request message from the third UE  13 . The first request message is used to request to establish a call between the third UE  13  and the second UE  12 . 
     Then, the detecting means  902  detects whether the second UE  12  is on a call with the first UE  11 . Since the second UE  12  is on a call with the first UE  11 , the detecting means  902  detects that the second UE  12  is busy. 
     Then, if the second UE  12  is on a call with the first UE  11 , the background voice providing means  904  provides the voice message from the third UE  13  as a background voice message for the second UE  12  while keeps the call between the first UE  11  and the second UE  12 . 
     In one embodiment, the background voice providing means  904  sends a second request message to the VMS  42 , and the second request message is used to request to establish a call between the third UE  13  and the VMS  42 ; and sends a third request message to the third UE  13 , and the third request message is used to request to establish a call between the VMS  42  and the third UE  13 . This operation is optional, for when the call controlling device is the S-CSCE entity  32  shown in  FIG. 1 , the operation an be realized by other devices, such as the TAS  22 , and the S-CSCF entity does not need to execute the operation. 
     At last, the background voice providing means  904  sends a fourth request message to the VMS  42  requesting to establish a call between the second UE  12  and the VMS  42 ; and sends a fifth request message to the second UE  12  requesting to establish a call between the VMS  42  and the second UE  12 . 
     Then, the first receiving means  901  receives a response message from the third UE  13  for responding to the third request message and a response message from the VMS  42  for responding to the second request message. The two response messages indicate that the voice channel between the third UE  13  and the VMS  42  can be established, then, the voice channel between the third UE  13  and the VMS  42  is established, and the third UE  13  sends the voice message to the VMS  42 . 
     The first receiving means  901  receives a response from the second UE  12  for responding to the fifth request message and a response message from the VMS  42  for responding to the fourth request message respectively. The two response messages indicate that the voice channel between the second UE  12  and the VMS can be established, then, the voice channel between the second UE  12  and the VMS  42  is established, and the VMS  42  sends the voice message from the third UE  13  to the second UE  12 . 
     Optionally, before the background voice providing means  904  sends the fourth and the fifth request messages, the first determining means  903  can further determine whether the second UE  12  subscribes to a service for receiving the voice message from the third UE  13  when the second UE  12  is on the call with the first UE  11 . If the second UE  12  subscribes to the service, the background voice providing means  904  executes its sending operation. The second UE  12  can set that it can receive the voice message from other UEs unconditionally during a call. Optionally, the second UE  12  can set in advance some service strategies, for example, the second UE  12  can set that it can receive the voice message from some specific UEs in the call during some specific periods; or the second UE  12  set whether to listen to the voice message or to leave a message according to its own location and the calling party(i.e., the one that leave a message)&#39;s location; or, the second UE  12  can set the priority of other users, when it is on a call with a UE with a higher priority, it will not receive the voice message from the UE with a lower priority; when it is on a call with a UE with a lower priority, it will receive the voice message from the UE with a higher priority. 
     Optionally, if the background voice providing means  904  needs to send the second request message and the third request message, then the determining means  903  can further determine whether the second UE  12  subscribes to the voice message service, if the second UE  12  subscribes to the voice message service, the background voice providing means  904  executes the subsequent operations. 
       FIG. 10  shows a block diagram of a second providing device  1000 , in a VMS in telecommunication networks, for providing a second UE which is on a call with a first UE with a voice message from a third UE, according to an embodiment of the present invention. In  FIG. 10 , the second providing device  1000  includes a second receiving means  1001 , a second determining means  1002  and a second sending means  1003 . 
     Without loss of generality, the network topology shown in  FIG. 1  or  FIG. 6  and the case that the second UE  12  and the first UE  11  are on a call, and the third UE  13  calls the second UE  12  is taken as an example to describe in detail the process of the second providing device  1000  in the VMS  42  or  92  for providing the second UE  12  with a voice message from the third UE  13 . 
     First, the second receiving means  1001  receives a third request message from the call controlling device. The third request message is used to request to establish a call between the third UE  13  and the VMS. For the network topology shown in  FIG. 1 , the third request message is the INVITE message shown in step S 505  in  FIG. 5 , and the call controlling device is the TAS  22  or the S-CSCF entity  32 . For the network topology shown in  FIG. 6 , the third request message is the IAM message shown in step S 707  in  FIG. 7 , and the call controlling device is the switch  83 . Then, the second sending means  1003  sends a sixth request message to the second UE  12 , requesting to establish a call between the second UE  12  and the VMS. For the network topology IS shown in  FIG. 1 , the sixth request message is the INVITE message shown in step S 512  of  FIG. 5 . For the network topology shown in  FIG. 6 , the sixth request message is the IAM message shown in step S 712  of  FIG. 7 . 
     Then, the second receiving means  1001  receives a response message from the second UE  12 . For the network topology shown in  FIG. 1 , the response message is the 200 OK message shown in step S 513  of  FIG. 5 . For the network topology shown in  FIG. 6 , the response message is the ACM and (Pseudo) ANM messages shown in step S 713  and S 714  of  FIG. 7 . 
     Optionally, before the second sending means  1003  sends the sixth request message, the second determining means  1002  can determine whether the second UE  12  subscribes to a service for receiving the voice message from the third UE  13  when the second UE  12  is on the call with the first UE  11 . If the second UE  12  subscribes to the service, the second sending means  1003  then executes its sending operation. 
     It should be noted that those skilled in the art can understand that the formats of the first to the sixth request messages and each response message are not limited to what are shown in  FIG. 3  to  FIG. 5  or  FIG. 7 , and their formats can vary with the change of the adopted telecommunication protocol. 
     Those skilled in the art can understand that the above-described embodiments are for purpose of illustration only, and not construed as limitation of the invention. The present invention is not limited to these embodiments. All technical solutions which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims. Besides, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” does not exclude the presence of elements or steps not listed in the claim or in the description. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In device that includes a plurality of means, one or more functions of the plurality of means can be implemented by one hardware or software module; the words “first”, “second” and “third” only represent name, and do not mean specific order.