Communication terminal and communication method

0001The present invention relates to a communication terminal device and a communication method for changing a codec used in a mobile communication system.

0002Conventionally, voice calls in the mobile communication system of 3GPP (Third Generation Partnership Project) have been performed using a circuit switching (CS) network of 3GPP. In recent years, VoLTE (Voice over Long Term Evolution) service, which is a voice call using a 3GPP packet switching (PS) network, is being provided.

0003However, the area where VoLTE service is available is limited for the time being. Therefore, when going out of the VoLTE service area during a voice call by VoLTE (hereinafter referred to as VoLTE call), it is necessary to switch to a call using the conventional circuit switching method. As a technique that enables this switching, there is SRVCC (Single Radio Voice Call Continuity) described in Non-Patent Document 1. Hereinafter, the operation of handover by SRVCC will be described with reference to FIGS. 1 and 2.

0004Figure 1 shows a part of the 3GPP mobile communication network configuration. The mobile communication networks shown in Fig. 1 include e-UTRAN (evolved Universal Terrestrial Radio Access Network), e-UTRAN base station (e-node B), PS network, CS network, CS network base station subsystem, and IMS ( It consists of IP Multimedia Subsystem).

0005Specifically, in FIG. 1, e-UTRAN is a radio access network capable of providing VoLTE services. The PS network provides VoLTE services and consists of P-GW (Packet Data Network Gateway), S-GW (Serving Gateway) and MME (Mobility Management Entity). The CS network consists of MSC (Mobile Switching Center) and MGW (Media Gateway). The base station subsystem of the CS network consists of RNC (Radio Network Controller) and node B. IMS performs call control, etc., and is composed of CSCF (Call Session Control Function) and SCC AS (Service Centralization and Continuity Application Server).

0006In FIG. 1, it is assumed that UE100 and UE102, which are mobile communication terminals (UE: User Equipment), are initially connected to the PS network (however, the radio access network, base station, and PS network on the UE102 side are not shown). ). That is, it is assumed that a VoLTE call is being made between UE100 and UE102. At this time, it is assumed that the UE 100 hands over to the CS network (HO: Hand Over) in the middle of the call.

0007Path A, Path B, and Path C shown by the solid line in FIG. 1 indicate the route through which the call data passes. Further, 200, 202, 204 and 206 shown by the broken line in FIG. 1 indicate the route through which the signaling in the SRVCC handover process passes.

0008FIG. 2 is a sequence chart showing the operation of SRVCC handover processing. UE100 and UE102 are initially connected to the PS network (e-UTRAN), respectively, and call data between UE100 and UE102 is transmitted and received through Path A. When UE100 tries to move away from the coverage area of e-UTRAN, e-nodeB detects this and exchanges signaling with RNC / nodeB via MME and MSC / MGW (Signaling 200 shown in Fig. 1). Step 2 (hereinafter referred to as "ST") 200). In ST200, a data path in the CS network is prepared between nodeB and MSC / MGW, and when the preparation is completed, the MME instructs UE100 to hand over to the UTRAN (CS network) side via e-nodeB. Is issued.

0009Simultaneously with the processing of ST200, MSC / MGW exchanges signaling with UE102 via CSCF / SCC AS (signaling 202 shown in FIG. 1; ST202 shown in FIG. 2). As a result, a command is issued to switch the transmission / reception destination of the call data of UE102 from UE100 to MSC / MGW, and Path B is established.

0010After handing over to UTRAN, UE100 exchanges signaling with MSC / MGW via RNC / nodeB (signaling 204 shown in FIG. 1; ST204 shown in FIG. 2). This establishes Path C.

0011After establishing Path C, MSC / MGW exchanges signaling with P-GW / S-GW via MME (Signaling 206 shown in Fig. 1; ST206 shown in Fig. 2). This removes Path A.

0012The operation of SRVCC handover has been described above.

0013Further, as a method for improving SRVCC and shortening the time required for data path switching, there is an SRVCC method (eSRVCC: enhanced-SRVCC) using ATCF (Access Transfer Control Function) enhancement described in Non-Patent Document 3. An example of the operation of this eSRVCC will be described below with reference to FIGS. 3 and 4.

0014Figure 3 shows a portion of the 3GPP mobile communication network configuration that enables eSRVCC. Similar to FIG. 1, the mobile communication network shown in FIG. 3 is composed of e-UTRAN, e-nodeB, PS network, CS network, CS network base station subsystem, and IMS. Here, in IMS, in addition to CSCF and SCC AS, ATCF (Access Transfer Control Function) and ATGW (Access Transfer Gate Way) exist. Although ATCF and ATGW are represented as one node (ATCF / ATGW1120) in FIGS. 3 and 4, they may be represented as separate nodes.

0015In FIG. 3, it is assumed that UE100 and UE102 are initially connected to the PS network (however, the radio access network, base station, and PS network on the UE102 side are not shown). That is, it is assumed that a VoLTE call is being made between UE100 and UE102. At this time, it is assumed that the UE 100 hands over to the CS network (HO: Hand Over) in the middle of the call.

0016Path A, Path B, Path C and Path D shown by the solid line in FIG. 3 indicate the route through which the call data passes. Further, 1100, 1102, 1104 and 1106 shown by the broken line in FIG. 3 indicate the routes through which the signaling in the eSRVCC handover process passes.

0017FIG. 4 is a sequence chart showing the operation of eSRVCC handover. UE100 and UE102 are initially connected to the PS network (e-UTRAN), respectively. In a system that implements eSRVCC handover, in ATCF / ATGW1120, ATCF anchors IMS signaling (IMS signaling), and ATGW anchors call data. In other words, at the start of a call between UE100 and UE102, the IMS signaling of the call start is relayed by ATCF, and if ATCF determines that an anchor of call data in ATGW is necessary, ATGW is assigned as an anchor point of call data. Be done. As a result, the call data between UE100 and UE102 is transmitted and received through Path A and Path B.

0018When UE100 tries to move away from the coverage area of e-UTRAN, e-nodeB detects this and exchanges signaling with RNC / nodeB via MME and MSC / MGW (Signaling 1100 shown in Fig. 3; Fig. 3). ST1100 shown in 4. In ST1100, a data path in the CS network is prepared between nodeB and MSC / MGW, and when the preparation is completed, the MME instructs UE100 to hand over to the UTRAN (CS network) side via e-nodeB. Is issued.

0019Simultaneously with the processing of ST1100, MSC / MGW sends signaling to ATCF. As a result, the ATCF issues an instruction to switch the route to the ATGW, and the ATGW call data transmission / reception destination is switched from UE100 to MSC / MGW (signaling 1102 shown in FIG. 3; ST1102 shown in FIG. 4). That is, Path C is established. When the route switching process to the ATGW is completed, the ATCF transmits a notification signaling to the SCC-AS (signaling 1102 shown in FIG. 3; ST1102 shown in FIG. 4).

0020After handing over to UTRAN, UE100 exchanges signaling with MSC / MGW via RNC / nodeB (signaling 1104 shown in FIG. 3; ST1104 shown in FIG. 4). This establishes Path D.

0021After Path D is established, MSC / MGW exchanges signaling with P-GW / S-GW via MME (Signaling 1106 shown in Fig. 3; ST1106 shown in Fig. 4). This removes Path B.

0022The operation of the eSRVCC handheld has been described above.

0023As the voice codec used in the CS network, the AMR (Adaptive Multi-Rate) codec, which is a narrowband (NB: Narrowband) codec, and the AMR-WB codec, which is a wideband (WB: Wideband) codec, are widely used. Since AMR and AMR-WB can be used by packet switching method, they are also considered to be used in PS network (VoLTE).

0024AMR and AMR-WB support different bit rates. Furthermore, when AMR and AMR-WB are used in the PS network, as described in Non-Patent Document 2, the bit rate is numbered (Frame Type Index) used in the RTP (Real-time Transport Protocol) payload format. Are overlapping on both sides. Therefore, it is necessary to decide whether to use AMR or AMR-WB at the start of the session, whether it is used on the CS network or the PS network. In other words, it is impossible to switch between AMR and AMR-WB without re-negotiating the session.

0025In the prior art, the narrowband codec is a codec that is generally sampled at 8 kHz with a bandwidth of 300 Hz to 3.4 kHz. A wideband codec is a codec that is generally sampled at 16 kHz with a bandwidth of 50 Hz to 7 kHz. An ultra-wideband (SWB) codec is a codec that is generally sampled at 32 kHz with a bandwidth of 50 Hz to 14 kHz.

<p num="0026"><nplcit num="1"><text>3GPP TS23.216 v9.6.0 "Single Radio Voice Call Continuity (SRVCC)"</text></nplcit><nplcit num="2"><text>IETF RFC 4867, "RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs"</text></nplcit><nplcit num="3"><text>3GPP TS23.237 v11.0.0 "IP Multimedia Subsystem (IMS) Service Continuity"</text></nplcit><nplcit num="4"><text>Takashi Koshimizu and Katsutoshi Noshida, "Audio Viedo Callof Single Radio Voice Call Continuity", 2011 IEICE General Conference, B-6-77</text></nplcit><nplcit num="5"><text>Katsutoshi Nishida, Takashi Koshimizu, "Proposal for improvement of IMS-circuit switching handover method for voice call", SRVCC method in the service area based on mobility function, Shingaku Giho NS2010-178, pp85-90</text></nplcit></p>

<p num="0027"> In Fig. 1 or Fig. 3, when UE100 hands over from PS network to CS network, if the codec used in PS network is not supported by CS network, the codec used in UE100 is CS network. Change to a supported codec. If the UE100 codec changes, the following two methods can be considered to enable the continuation of the call between the UE100 and UE102. The first method is to change the codec used in UE102 to the same codec as the modified codec in UE100. The second method is to transcode in MSC / MGW.</p><p num="0028"> The former method is not preferable because it takes time for signaling to change the codec of UE102 and the call is interrupted for a long time. Further, in the eSRVCC handover, since the signaling for route switching at the time of the handover of UE100 is terminated at ATCF, it is not possible to even send the signaling for changing the codec of UE102. That is, in the eSRVCC handover, the codec of UE102 cannot be changed by using the existing signaling.</p><p num="0029"> Therefore, the latter transcoding method is considered to be relatively preferable. However, when transcoding is performed, especially when the bandwidth of the codec (the bandwidth of the signal that is the input / output of the codec) is different, when transcoding from a codec with a wide bandwidth to a codec with a narrow bandwidth, a call is made. Quality degradation will occur.</p><p num="0030"> An object of the present invention is a communication terminal device and a communication method capable of suppressing deterioration of call quality due to transcoding without interrupting a call even when the codec used by one of the terminals during communication is changed. Is to provide.</p>

<p num="0031"> The network node according to one aspect of the present invention is a network node that transcodes communication between two terminals using different codecs, and is a detection means for detecting a codec used by each of the two terminals. When a change in the codec used by one of the two terminals is detected based on the detection result by the detection means, the first codec of the other terminal other than the one terminal, and A determination means for determining whether or not to limit the first bandwidth of the first codec by using the modified second codec of the one terminal, and the first determination means in the determination means. When it is determined that the bandwidth is limited, a configuration including a transmission means for transmitting the signaling for limiting the first bandwidth to the other terminal is adopted.</p><p num="0032"> The terminal according to one aspect of the present invention is a terminal used in a communication system in which transcoding is performed by a network node located between terminals for communication between terminals using different codecs, and the terminal and the terminal are used. A negotiating means for negotiating a first codec used for communication with a partner terminal which is a communication partner of the terminal, and an input signal encoded by the terminal with respect to the negotiated first codec. The change of the first bandwidth determined by the determination means is controlled according to the determination means for determining the bandwidth of 1 and the signaling for limiting the first bandwidth notified from the network node. A configuration is adopted that includes, and a means for changing.</p><p num="0033"> The bandwidth change determination method according to one aspect of the present invention is a bandwidth change determination method in a network node that transcodes communication between two terminals using different codecs, and the two terminals are each used. When the codec to be used is detected and the change of the codec used by one of the two terminals is detected based on the detection result, the first codec of the other terminal other than the one terminal, Then, it is determined whether or not to limit the first bandwidth of the first codec by using the modified second codec of the one terminal, and it is determined that the first bandwidth is limited. If so, the signaling for limiting the first bandwidth is transmitted to the other terminal.</p><p num="0034"> The bandwidth changing method according to one aspect of the present invention is a bandwidth changing method in a terminal used in a communication system in which transcoding is performed by a network node located between terminals for communication between terminals using different codecs. A first codec used for communication between the terminal and the other terminal that is the communication partner of the terminal is negotiated, and the negotiated first codec is encoded in the terminal. The first bandwidth of the input signal is selected, and the change of the first bandwidth is controlled according to the signaling for limiting the first bandwidth notified from the network node, and the first bandwidth is controlled. The first bandwidth is determined according to the control of the bandwidth change of.</p>

<p num="0035"> According to the present invention, even if the codec used by one of the terminals being communicated is changed, the deterioration of the call quality due to transcoding can be suppressed without interrupting the call.</p>

0036<figref num="1">Configuration diagram showing a part of 3GPP mobile communication network</figref><figref num="2">Sequence chart showing SRVCC handover operation</figref><figref num="3">Configuration diagram showing a part of 3GPP mobile communication network that enables eSRVCC</figref><figref num="4">Sequence chart showing the operation of eSRVCC handover</figref><figref num="5">Configuration diagram showing a part of the mobile communication network according to the first embodiment of the present invention.</figref><figref num="6">A block diagram showing a configuration of a network node (MSC / MGW) according to the first embodiment of the present invention.</figref><figref num="7">A flowchart showing an example of a determination method in the change determination unit of the MSC / MGW according to the first embodiment of the present invention.</figref><figref num="8">A block diagram showing a configuration of a terminal (UE) according to the first embodiment of the present invention.</figref><figref num="9">The figure which shows an example of SDP used for the codec negotiation which concerns on Embodiment 1 of this invention.</figref><figref num="10">Sequence chart showing the operation according to the first embodiment of the present invention.</figref><figref num="11">The figure which shows an example of the band limitation request message which concerns on Embodiment 1 of this invention.</figref><figref num="12">A block diagram showing a configuration of a terminal (UE) according to a second embodiment of the present invention.</figref><figref num="13">A block diagram showing a part of the mobile communication network according to the third embodiment of the present invention.</figref><figref num="14">Block diagram showing the configuration of the network node (MSC / MGW) according to the third embodiment of the present invention.</figref><figref num="15">Sequence chart showing the operation according to the third embodiment of the present invention.</figref><figref num="16">A flowchart showing an example of a codec selection method in the codec selection unit of the MSC / MGW according to the third embodiment of the present invention.</figref><figref num="17">Sequence chart showing the operation according to the variation of the third embodiment of the present invention.</figref><figref num="18">A block diagram showing a part of the mobile communication network according to the fourth embodiment of the present invention.</figref><figref num="19">Block diagram showing the configuration of the network node (ATCF / ATGW, MSC / MGW) according to the fourth embodiment of the present invention.</figref><figref num="20">A block diagram showing a configuration of a terminal (UE) according to a fourth embodiment of the present invention.</figref><figref num="21">Sequence chart showing the operation according to the fourth embodiment of the present invention.</figref>

0037Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings.

0038In the following description, the "bandwidth" refers to the bandwidth of the signal that is the input / output of the codec.

0039Further, in the following description, the "codec whose bandwidth does not necessarily need to be specified" means a codec capable of switching the bandwidth of the input signal to be encoded without re-negotiating the session. For example, the non-interoperable mode of the EVS (Enhanced Voice Services) codec is used only on PS networks, and the supported bitrates are common to all bandwidths ("3GPP TSG SA WG4 S4"). -110539 "EVS Permanent Document # 4 (EVS-4): EVS design constraints "). Therefore, in the compatibility mode of the EVS codec, the bandwidth of the input signal to be encoded can be freely changed even during the session if the bandwidth is below the Nyquist frequency (1/2 of the sampling frequency). It is possible to design. Therefore, it is not always necessary to specify the bandwidth from the start to the end of the session. In this case, the encoder sets the bandwidth of the input signal to be encoded according to, for example, the characteristics of the input signal (for example, the frequency characteristics of the input signal and the parameters obtained by analyzing the input signal) or the encoding bit rate. Or change.

0040(Embodiment 1) FIG. 5 is a configuration showing a part of the mobile communication network according to the first embodiment of the present invention. In FIG. 5, the same reference numerals are given to the parts having the same configuration as that of FIG. 1, and the description thereof will be omitted. In FIG. 5, the operations of UE100, 102 and MSC / MGW300 are different from those in FIG.

0041First, the MSC / MGW300 shown in FIG. 5 will be described. The MSC / MGW300 transcodes communications between two terminals that use different codecs.

0042FIG. 6 is a block diagram showing the configuration of the MSC / MGW300 (network node) according to the present embodiment. In order to avoid complicating the explanation, in FIG. 6, the main components related to the band limitation (band change) process closely related to the present invention (for example, ST402 to 406 shown in FIG. 5 (described later)). ) Is shown.

0043In the MSC / MGW 300 shown in FIG. 6, the receiving unit 600 receives call data (hereinafter referred to as communication data), signaling, and the like. For example, when the receiving unit 600 receives the signaling transmitted from the UE 100 and the UE 102 (for example, the signaling 202, 204 shown in FIG. 1), the receiving unit 600 outputs the received signaling to the codec detection unit 604 and the codec bandwidth detection unit 606, respectively.

0044The transmission unit 602 transmits communication data, signaling, and the like. For example, the transmission unit 602 notifies the UE 102 of the signaling output from the signaling generation unit 610.

0045The codec detection unit 604 detects the codecs used by the UE 100 and UE 102, respectively, based on the signaling, communication data, and the like from the UE 100 and UE 102 input from the reception unit 600. Then, the codec detection unit 604 outputs information (detection result) indicating the detected codec to the change determination unit 608.

0046The codec bandwidth detection unit 606 detects the bandwidth of the codec used by the UE 100 and UE 102, respectively, based on the signaling, communication data, and the like from the UE 100 and UE 102 input from the reception unit 600. Then, the codec bandwidth detection unit 606 outputs information (detection result) indicating the bandwidth of the detected codec to the change determination unit 608.

0047The change determination unit 608 is encoded into the UE 102 based on the codec indicated in the information input from the codec detection unit 604 and the bandwidth of the codec indicated in the information input from the codec bandwidth detection unit 606. Determine if the input signal is capable of bandwidth limiting and if bandwidth limiting is required. For example, when the change determination unit 608 detects a change in the codec used by one of the two terminals (UE100 and UE102) based on the detection result of the codec detection unit 604, the codec of the other UE102, Then, it is determined whether or not to limit the bandwidth of the codec of UE102 by using the changed codec of UE100. The change determination unit 608 outputs the determination result to the signaling generation unit 610. The details of the bandwidth change determination process in the change determination unit 608 will be described later.

0048When the change determination unit 608 determines that the bandwidth limitation of the input signal encoded by the UE 102 is possible and the bandwidth limitation is necessary, the signaling generation unit 610 determines that the input signal encoded by the UE 102 is required. Generates a signal that asks the UE 102 to limit the bandwidth of. The signaling requesting the bandwidth limit may include, for example, information indicating the changed bandwidth of the UE 100. The signaling generation unit 610 transmits the generated signaling to the UE 102 via the transmission unit 602. In this way, when the change determination unit 608 determines that the bandwidth of the codec of the UE 102 is limited, signaling for limiting the bandwidth is transmitted to the UE 102 via the transmission unit 602.

0049When UE100 and UE102 use different codecs, the transcoding unit 612 transcodes the communication data from UE100 to UE102 and the communication data from UE102 to UE100.

0050Next, the details of the bandwidth change determination process in the change determination unit 608 of the MSC / MGW300 will be described with reference to FIG. 7.

0051In ST800 shown in FIG. 7, the change determination unit 608 determines whether or not the codec of the UE 100 has been changed based on the detection result (detected codec) of the codec detection unit 604.

0052When the codec of UE100 is changed (ST800: Yes), in ST802, the change judgment unit 608 determines that the codec used in UE102 is the codec A, based on the detection result of the codec detection unit 604. Determine if the codec does not require bandwidth specification.

0053When the codec used in UE102 is a codec that does not require bandwidth specification (ST802: Yes), in ST804, the change determination unit 608 changes the UE100 based on the detection result in the codec bandwidth detection unit 606. Determines if the bandwidth of the later codec is narrower than the maximum bandwidth of the codec currently in use by the UE 102.

0054If the bandwidth of the modified codec of UE100 is narrower than the maximum bandwidth of the codec currently used by UE102 (ST804: Yes), in ST806, the change determination unit 608 will be the input signal encoded to UE102. Judge that bandwidth limitation is possible and necessary. For example, the change determination unit 608 determines that the bandwidth of the codec of the UE 102 is limited (changed) to the bandwidth of the codec after the change of the UE 100.

0055On the other hand, if the UE100 codec has not been changed (ST800: No), the codec used in UE102 is not a codec that does not require bandwidth specification (ST802: No), or the UE100 changed codec. If the bandwidth of is equal to or greater than the maximum bandwidth of the codec currently used by UE102 (ST804: No), in ST808, the change determination unit 608 determines that the bandwidth is not limited to UE102.

0056In this way, specifically, when a change in the codec of one UE is detected, the MSC / MGW300 determines whether the codec of the other UE is a codec whose bandwidth does not need to be specified. Then, it is judged whether or not it is possible to limit (change) the bandwidth of the codec of the other UE. The MSC / MGW300 also determines whether the bandwidth of the modified codec of one UE is narrower than the maximum bandwidth of the codec of the other UE, thereby determining the bandwidth of the codec of the other UE. Determine if restrictions (changes) are needed.

0057Next, UE 100, 102 shown in FIG. 5 will be described.

0058FIG. 8 is a block diagram showing the configuration of UE100, 102 (terminal) according to the present embodiment. In order to avoid complicated explanation, FIG. 8 shows a configuration related to ST400 to 406 (described later) shown in FIG. 5 (for example, a configuration related to ST400 to 406 (described later) shown in FIG. 5), which are closely related to the present invention. Part) is shown.

0059In UE 100, 102 shown in FIG. 8, the receiving unit 700 receives communication data, signaling, and the like. For example, when the receiving unit 700 receives the signaling transmitted from the MSC / MGW 300 (for example, the signaling 202 or 204 shown in FIG. 1), the receiving unit 700 outputs the received signaling to the codec negotiation unit 704 and the signaling analysis unit 710.

0060The transmission unit 702 transmits communication data, signaling (for example, signaling 202 or 204 shown in FIG. 1) and the like.

0061The codec negotiation unit 704 negotiates a codec used for communication between terminals (here, UE100 and UE102). Specifically, the codec negotiation unit 704 creates an SDP (Session Description Protocol) offer or an SDP answer, and negotiates the codec. When the UE (UE100 in FIG. 5) moves to the CS network, the codec negotiation unit 704 of the UE performs codec negotiation based on the negotiation method on the CS network. The codec negotiation unit 704 outputs the result of the coding negotiation to the codec selection unit 706.

0062FIG. 9 shows an example of SDP used for codec negotiation in the embodiment of the present invention. If the calling UE supports a codec that does not necessarily require bandwidth specification (hereinafter referred to as codec A), specify only the sampling frequency for codec A and SDP without specifying the bandwidth. Generate an offer. For example, in FIG. 9, the SDP offer generated by the calling UE includes the conventional WB codec AMR-WB codec (for example, bandwidth: 50 Hz to 7 kHz, sampling frequency: 16000), and the conventional WB codec. The AMR codec (for example, bandwidth: 300Hz to 3.4kHz, sampling frequency: 8000), which is an NB codec, and codec A (sampling frequency: 32000), which does not require specification of the bandwidth, are described.

0063In addition, if the called UE supports codec A, it accepts the condition that no bandwidth is specified and only the sampling frequency of codec A is specified (select codec A shown in FIG. 9). Generate an SDP answer. The codec A may be in an incompatible mode of the EVS codec described above. Here, the maximum bandwidth supported by the sampling frequency 32000 of codec A is equivalent to SWB (Super Wideband), and the encoder has the characteristics of the input signal or the encoding bit rate within this bandwidth even during the session. It is assumed that the bandwidth can be freely changed according to the above.

0064The codec selection unit 706 selects the codec negotiated by the codec negotiation unit 704, and outputs information indicating the selected codec to the bandwidth determination unit 708.

0065The bandwidth determination unit 708 determines the bandwidth of the input signal encoded in the own terminal with respect to the codec selected by the codec selection unit 706. For example, the bandwidth determination unit 708 selects the bandwidth when the bandwidth of the codec selected by the codec selection unit 706 is constant. On the other hand, the bandwidth determination unit 708 determines the bandwidth of the input signal to be encoded when the bandwidth of the codec selected by the codec selection unit 706 can change the bandwidth in one session like the codec A. Determined for each frame. The bandwidth determination unit 708 determines the bandwidth of the input signal to be encoded for each frame in response to, for example, the encoding bit rate, the input signal characteristics, or the request for bandwidth limitation by external signaling. More specifically, the bandwidth determination unit 708 determines the bandwidth of the input signal to be encoded when, for example, the codec mode change unit 712 notifies that the codec bandwidth limitation (change) is requested. , Limit (change) to the requested bandwidth.

0066The signaling analysis unit 710 analyzes the signaling input from the receiving unit 700. The signaling includes, for example, signaling requesting bandwidth limitation from the MSC / MGW300 (signaling for limiting bandwidth). The signaling analysis unit 710 notifies the codec mode change unit 712 of the result of the signaling analysis.

0067The codec mode change unit 712 limits (changes) the bandwidth of the input signal to be encoded when the signaling analysis result input from the signaling analysis unit 710 is signaling that requests the limitation (change) of the bandwidth of the codec. It decides that, and notifies the bandwidth determination unit 708 to that effect. That is, the codec mode changing unit 712 controls the bandwidth change determined by the bandwidth determining unit 708 according to the signaling for limiting the bandwidth of the codec notified from the MSC / MGW300.

0068The signaling analysis unit 710 may analyze other external signaling and notify the codec mode change unit 712 of the analysis result. For example, the signaling analysis unit 710 may analyze the above-mentioned RTCP-APP and notify the codec mode change unit 712 of the analysis result (for example, a request for changing the encoding bit rate). In this case, when the codec mode changing unit 712 determines the encoding bit rate, the codec mode changing unit 712 notifies the bandwidth determining unit 708 of the determined encoding bit rate. Then, the bandwidth determination unit 708 determines the bandwidth according to the determined encoding bit rate.

0069Next, an example of the operation of UE100, 102 and MSC / MGW300 in this embodiment will be described.

0070FIG. 10 is a sequence chart showing the operation of each device of the mobile communication network shown in FIG. In FIG. 10, the same reference numerals are given to the parts having the same operation as in FIG. 2, and the description thereof will be omitted.

0071In the following explanation, in FIG. 5, it is assumed that both UE100 and UE102 are currently connected to a wireless access network that enables VoLTE calling services such as e-UTRAN (however, the wireless access network and base on the UE102 side). Stations and PS networks are not shown). That is, a VoLTE call is started between UE100 and UE102 shown in FIG.

0072At the start of a call, the codec to be used is negotiated between UE100 and UE102 (see, for example, "3GPP TS26.114 v10.0.0" IP Multimedia Subsystem (IMS); Multimedia Telephony; Media Handling and interaction "). .. For example, UE100 and UE102 (codec negotiation unit 704) negotiate the codec for a codec whose bandwidth is not necessarily specified (ST400 shown in FIGS. 5 and 10).

0073Next, as shown in FIG. 5, it is assumed that the UE 100 performs a handover by SRVCC and moves to UTRAN. In other words, assume that UE100 has moved from the PS network to the CS network.

0074In this case, in the process of ST204 in FIG. 10, the codec used in the CS network is re-negotiated between UE100 (codec negotiation unit 704) and MSC / MGW300. Here, for example, it is assumed that the UE100 is negotiated to use the AMR codec and the bandwidth of the codec used by the UE100 is limited to NB (ST402 shown in FIGS. 5 and 10).

0075In addition, the MSC / MGW300 (codec detection unit 604 and codec bandwidth detection unit 606) uses the process of ST202 in FIG. 10 to indicate that the codec used by UE102 is codec A and the maximum bandwidth is SWB. To detect.

0076In addition, the MSC / MGW300 (codec detection unit 604 and codec bandwidth detection unit 606) detects that the codec used in UE100 has become AMR and the bandwidth has been limited to NB by the process of ST204 in FIG. To do.

0077The MSC / MGW300 (change determination unit 608) determines whether the bandwidth of the input signal encoded to the UE 102 can be limited and whether the bandwidth limitation is necessary. Here, the UE100 codec has been changed (ST800: Yes shown in Figure 7), the UE102 codec is Codec A (ST802: Yes shown in Figure 7), and the UE100 AMR codec bandwidth (NB) has been changed. It is narrower than the maximum bandwidth (SWB) of codec A of UE102 (ST804: Yes shown in Figure 7). Therefore, the MSC / MGW300 (change determination unit 608) determines that it is possible and necessary to limit the bandwidth of the input signal encoded by the UE 102 (ST806 shown in FIG. 7).

0078Therefore, the MSC / MGW300 (signaling generator 610) requests the UE 102 to limit the bandwidth of the codec A-encoded input signal to the NB (the bandwidth of the codec after the change of the UE 100). Send (ST404 shown in Figures 5 and 10). This signaling may be included in, for example, a series of signaling in ST202 (ie, IMS signaling), RTCP (Real-time Transport Control Protocol) -APP (Application-defined) (eg, "3GPP TS26.114 v10.0.0". It may be sent by another signaling such as "IP Multimedia Subsystem (IMS); Multimedia Telephony; Media Handling and interaction"). FIG. 11A shows an example of the case where the signaling for notifying the bandwidth limitation is included in the IMS signaling. In addition, FIG. 11B shows an example in which RTCP-APP includes signaling for notifying the bandwidth limitation.

0079UE102 (Signaling Analysis Unit 710) analyzes the signaling from the MSC / MGW300. Then, UE102 (codec mode change unit 712) identifies that the limitation of the bandwidth of codec A is requested. Therefore, the UE 102 (bandwidth determination unit 708) limits the bandwidth of the input signal encoded by the UE 102 to the requested bandwidth (here, NB). The UE 102 then encodes the communication data with a limited bandwidth (ST406 shown in FIG. 10).

0080In this way, the UE 100 uses the modified codec bandwidth (NB) and the UE 102 uses the codec A's bandwidth-limited bandwidth (NB). As a result, both UE100 and UE102 use the same NB as the codec bandwidth. Therefore, in the MSC / MGW300 (transcoding unit 612), the call quality deteriorates even when transcoding from the UE102 side to the UE100 side (transcoding from codec A (ultra-wideband) to AMR codec (narrowband)). Can be suppressed.

0081As described above, in the present embodiment, even if the codec is changed in some UE100s of the UEs in communication, the MSC / MGW300 (network node) is compared with the other UE102s after the change of the UE100. Request a codec bandwidth limit to match the codec bandwidth. In addition, the UE 102 limits the bandwidth of the input signal encoded by the UE 102 according to the UE 100 even when the codec of the UE 100, which is the communication partner during the VoLTE call, is changed (changed to a narrow bandwidth). That is, the UE 102 changes the bandwidth of the input signal to be encoded according to the network condition of the UE 100, which is the communication partner, without interrupting the communication with the UE 100.

0082As a result, even if the network condition of one UE changes, the bandwidth of the codec between the UEs can be maintained at the same level. Therefore, it is possible to suppress the deterioration of call quality that occurs when transcoding from a codec having a wide bandwidth to a codec having a narrow bandwidth. That is, the MSC / MGW300 can perform transcoding while suppressing deterioration of communication quality.

0083Further, in UE102, since only the bandwidth of the input signal to be encoded is limited without changing the codec, signaling for changing the codec becomes unnecessary, and it is possible to prevent the call from being interrupted for a long time. ..

0084Therefore, according to the present embodiment, even if the UE 100 during the VoLTE call is handed over to the CS network and the codec is changed in the handover destination CS network, the band of the input signal encoded by the UE 102 is not interrupted. The width can be limited. As a result, deterioration of call quality due to transcoding from the UE102 side to the UE100 side can be suppressed. That is, according to the present embodiment, even if the codec used by one of the terminals (UE) during the VoLTE call is changed, the deterioration of the call quality due to transcoding can be suppressed without interrupting the call. Can be done.

0085In the above embodiment (see, for example, FIG. 5), the UE 100 is rSRVCC (reverse SRVCC. For example, "3GPP TR23.885 v1.2.0" Feasibility Study of Single Radio Voice Call Continuity (SRVCC) from UTRAN / GERAN to E. -If it supports "UTRAN / HSPA"), there is a possibility that the PS network will be handed over to the CS network and then the PS network will be handed over again. In this case, the MSC / MGW 300 may transmit a signaling for releasing the bandwidth limitation of the codec to the UE 102 when the signal regarding the handover processing from the CS network of the UE 100 to the PS network is received. Alternatively, the MSC / MGW 300 may transmit a signaling to the UE 102 to release the bandwidth limitation of the codec after the UE 100 completes the handover to the PS network.

0086Further, in the above embodiment (see, for example, FIG. 5), a case where the UE 100 is connected to the PS network at the start of a call has been described. However, it is possible that the UE100 is connected to the CS network at the start of the call. In this case, for example, the UE100 starts a call with the UE102 connected to the PS network by the method described in "3GPP TS23.292 v10.3.0" IP Multimedia Subsystem (IMS) centralized services "". Here, when the UE100 supports rSRVCC (that is, when the UE100 can hand over to the PS network), the MSC / MGW300 will contact the UE102 when negotiating a codec with the UE102. You may negotiate in advance to encode the bandwidth of the codec used as the maximum bandwidth. Alternatively, the MSC / MGW 300 may request a bandwidth limit of the input signal encoded by the UE 102 by another signaling after negotiation with the UE 102.

0087Further, in the present embodiment, the SRVCC method has been described, but the present embodiment can also be applied to the eSRVCC method.

0088In the SRVCC method, transcoding is performed in MGW (MSC / MGW300) when the codec used by the UE during communication is different. On the other hand, according to Non-Patent Document 3, in the eSRVCC method, ATGW may perform transcoding instead of MGW transcoding.

0089Here, in the eSRVCC method, when transcoding is performed by ATGW instead of MGW, the functions added to the MSC / MGW300 (see FIG. 5) according to the present embodiment for the SRVCC method are ATCF / ATGW1120 (see FIG. 3). ) Is added. That is, in the eSRVCC method, the ATCF / ATGW1120 includes the receiving unit 600, the transmitting unit 602, the codec detection unit 604, the codec bandwidth detection unit 606, the change determination unit 608, the signaling generation unit 610, and the transcoding unit 612 shown in FIG. Take the configuration to be provided. Here, regarding the transmission unit 602, the codec detection unit 604, the change determination unit 608, the signaling generation unit 610, and the transcoding unit 612 of the ATCF / ATGW1120 in the eSRVCC method, the components of the MSC / MGW300 in the SRVCC method are used. Has the same function.

0090The receiving unit 600 (Fig. 6) of the ATCF / ATGW1120 in the eSRVCC method receives communication data, signaling, and the like. For example, when the receiving unit 600 receives the signaling transmitted from UE100, UE102, ATCF, and MSC / MGW (for example, the signaling 1102 shown in FIG. 3), the received signaling is transmitted to the codec detector 604 and the codec bandwidth. Output to detector 606.

0091The codec detection unit 604 detects the codecs used by the UE 100 and UE 102, respectively, based on the signaling, communication data, and the like from the UE 100, UE 102, ATCF, and MSC / MGW input from the reception unit 600. Then, the codec detection unit 604 outputs information (detection result) indicating the detected codec to the change determination unit 608.

0092The codec bandwidth detection unit 606 detects the bandwidth of the codec used by the UE 100 and UE 102, respectively, based on the signaling, communication data, and the like from the UE 100, UE 102, and MSC / MGW input from the reception unit 600. Then, the codec bandwidth detection unit 606 outputs information (detection result) indicating the bandwidth of the detected codec to the change determination unit 608.

0093Although ATCF / ATGW1120 has been described as one node here, it may be a separate node. Therefore, either one or both of ATCF and ATGW may have the functions of ATCF / ATGW1120 described above. In addition, necessary information may be exchanged between ATCF and ATGW.

0094Further, in the above embodiment, each UE may specify the maximum bandwidth by SDP instead of fixing and not specifying the bandwidth by SDP as shown in FIG. 9 at the time of coding negotiation.

0095Further, in the above embodiment, the case where the MSC / MGW300 and the ATGW transmit a signaling requesting the UE 102 to limit the bandwidth of the input signal to be encoded has been described. However, the MSC / MGW300, and ATGW may transmit signaling requesting an encoding bit rate limit instead of signaling requesting a bandwidth limit. Here, each UE sets the bandwidth of the input signal to be encoded based on the encoding bit rate of the input signal. Therefore, when the MSC / MGW300 and ATGW send a signal to the UE requesting the limit of the encoding bit rate, the UE sets the limited encoding bit rate and is based on the limited encoding bit rate. Therefore, it is possible to limit the bandwidth of the input signal to be encoded. Alternatively, the MSC / MGW300, and ATGW may transmit signaling requesting limits on both bandwidth and encoding bit rate.

0096Further, in the above embodiment, the MSC / MGW300 (Fig. 6) has been described as one node. However, the MSC / MGW300 may be composed of two or more nodes connected to each other by an interface, and each function of the MSC / MGW300 described above may be distributed to these a plurality of nodes.

0097(Embodiment 2) In the first embodiment, the case where the MSC / MGW300 or the ATGW (ATCF / ATGW1120) transmits a signaling requesting the UE 102 to limit the bandwidth of the input signal to be encoded has been described. On the other hand, in the present embodiment, instead of the MSC / MGW300 or ATGW (ATCF / ATGW1120) transmitting the signaling requesting the bandwidth limitation, the UE 102 receives the communication data to receive the bandwidth of the UE100 codec. A case where it is detected that the width is limited and the bandwidth of the encoded input signal of the UE 102 is limited will be described.

0098The UE according to the present embodiment will be described with reference to FIG.

0099In UE 100, 102 shown in FIG. 12, the receiving unit 700, the transmitting unit 702, the codec negotiation unit 704, the codec selection unit 706, and the bandwidth determining unit 708 are components that perform the same operation as in FIG. Omit.

0100The data analysis unit 1200 analyzes the communication data input from the reception unit 700. In the data analysis unit 1200, the upper limit of the codec bandwidth of the communication data from a certain time to a certain time is the upper limit of the codec bandwidth until just before that, or the upper limit of the bandwidth of the codec negotiated at the start of the call. If it is different from the above, it is analyzed that the bandwidth of the codec of the communication data of the communication destination terminal (UE) is limited (changed). The data analysis unit 1200 notifies the codec mode change unit 1202 of the analysis result.

0101The codec mode change unit 1202 determines to limit (change) the bandwidth of the input signal to be encoded based on the analysis result from the data analysis unit 1200, and notifies the bandwidth determination unit 708 to that effect. As a result, the bandwidth determination unit 708 controls the bandwidth change determined by the codec mode change unit 1202.

0102As described above, in the present embodiment, the UEs 100 and 102 determine whether or not the codec of the communication partner terminal has been changed according to whether or not the upper limit of the bandwidth of the codec of the received communication data has been changed. To do. Then, when it is determined that the codec of the communication partner terminal has been changed, the UEs 100 and 102 control the change of the bandwidth of the codec of the own device. As a result, as in the first embodiment, even if the network condition of one UE changes, the bandwidth of the codec between the UEs can be maintained at the same level. Therefore, as in the first embodiment, it is possible to suppress the deterioration of call quality that occurs when transcoding from a codec having a wide bandwidth to a codec having a narrow bandwidth.

0103(Embodiment 3) FIG. 13 is a configuration showing a part of the mobile communication network according to the third embodiment of the present invention. The operation of each node shown in FIG. 13 is as described above (for example, FIG. 5).

0104In FIG. 13, the UE 100 first performs a handover to the CS network at SRVCC (hereinafter, also referred to as SRVCC handover), and transmits / receives communication data to and from the UE 102 existing in the PS network via the MSC / MGW1300. (Path A and Path B shown in Fig. 13). At this time, UE100 uses AMR-WB as the codec used in the CS network, and UE102 uses, for example, the above-mentioned codec A (codec that does not necessarily require bandwidth specification) as the codec used in the PS network, and MSC / Suppose transcoding was done on the MGW1300.

0105Next, it is assumed that UE 102 also performs a handover to the CS network by SRVCC.

0106At this time, according to the handover procedure of Non-Patent Document 1, the communication on the destination CS network of UE102 is terminated by MSC / MGW1302, and the communication destination of MSC / MGW1300 is changed from UE102 to MSC / MGW1302. That is, the route of communication data between UE100 and UE102 is changed to a route passing through Path D, Path C, and Path B.

0107Furthermore, assume that the codec used by UE102 in the CS network has been changed to AMR-WB. In this case, from UE102 to MSC / MGW1302, the communication data transmitted from UE102 to UE100 passes through Path D and is transmitted using AMR-WB. Next, the MSC / MGW1302 transcodes from AMR-WB used by UE102 in the CS network to codec A used in the PS network. Therefore, from MSC / MGW1302 to MSC / MGW1300, the communication data transmitted from UE102 to UE100 passes through Path C and is transmitted using codec A. The MSC / MGW1300 then transcodes from codec A to AMR-WB. Therefore, from MSC / MGW1300 to UE100, the communication data transmitted from UE102 to UE100 passes through Path B and is transmitted using AMR-WB. The same applies to the communication data transmitted from UE100 to UE102.

0108In the present embodiment, a method of minimizing transcoding in the MSC / MGW1300 and 1302 will be described even when both the UE100 and UE102 in communication perform SRVCC handover.

0109First, the MSC / MGW1300 and 1302 shown in FIG. 13 will be described.

0110FIG. 14 is a block diagram showing the configurations of MSC / MGW1300 and 1302 according to the present embodiment. The MSC / MGW1300 and 1302 shown in FIG. 14 may include the functional block shown in FIG. 8 or other functional blocks in addition to the functional blocks shown in FIG.

0111In the MSC / MGW1300 and 1302 shown in FIG. 14, the receiving unit 1500 receives communication data, signaling, and the like.

0112The transmission unit 1502 transmits communication data, signaling, and the like.

0113The signaling analysis unit 1504 analyzes signaling for SRVCC processing, IMS signaling (IMS signaling), and the like. The signaling analysis unit 1504 notifies the signaling analysis result to the signaling generation unit 1506, the terminal position determination unit 1508, and the codec selection unit 1510.

0114The signaling generation unit 1506 generates signaling based on the signaling analysis result of the signaling analysis unit 1504 and the like.

0115The terminal position determination unit 1508 determines whether both terminals (UE100, 102) in communication exist in the PS network or the CS network based on the signaling analysis result of the signaling analysis unit 1504. The terminal position determination unit 1508 outputs the determination result to the codec selection unit 1510 and the route selection unit 1512.

0116The codec selection unit 1510 selects a codec to be used or a codec candidate based on the signaling analysis result of the signaling analysis unit 1504 and the determination result of the terminal position determination unit 1508.

0117The route selection unit 1512 selects a route through which communication data passes based on the determination result of the terminal position determination unit 1508.

0118Next, an example of the operation of the MSC / MGW1300, 1302 in the present embodiment will be described.

0119FIG. 15 is a sequence chart showing the operation of each device of the mobile communication network shown in FIG. Although SCC AS and CSCF are not shown in FIG. 13, it is assumed that they exist as a part of IMS.

0120Currently, it is assumed that both UE100 and UE102 are connected to e-UTRAN and are performing VoLTE communication. That is, it is assumed that UE100 and UE102 currently use the above-mentioned codec A (codec whose bandwidth is not necessarily specified) as the voice codec (ST1400 shown in FIG. 15).

0121Next, the UE 100 hands over to the CS network (SRVCC handover) (a process equivalent to the ST200 process (SRVCC process) shown in FIG. 10). In addition, UE100 hands over to the CS network and establishes a connection with the CS network (processing equivalent to ST204 processing (connection establishment processing) shown in FIG. 10).

0122Simultaneously with the processing of ST200 and ST204, the signaling generation unit 1506 of the MSC / MGW1300 generates the IMS signaling to be transmitted to the UE 102 and transmits it via the transmission unit 1502 (ST1402 shown in FIG. 15). At this time, the signaling generation unit 1506 includes information indicating that the IMS signaling is the IMS signaling generated by the SRVCC handover in the IMS signaling. For example, the information indicating that the IMS signaling is generated by the SRVCC handover may be STN-SR (Session Transfer Number for SRVCC) or the like described in Non-Patent Document 3.

0123In addition to the codec (codec A) used by the UE100 in the PS network, the signaling generator 1506 of the MSC / MGW1300 supports the CS network on its own network (the CS network to which the MSC / MGW1300 belongs). Include a list of codecs in the IMS signaling (ST1402 shown in Figure 15). At this time, the signaling analysis unit 1504 waits for the connection establishment process of ST204, analyzes the signaling related to the connection establishment, obtains the codec information used by the UE 100 in the CS network, and then the signaling generation unit 1506 obtains this codec information. It may be explicitly included in the IMS signaling.

0124As a result, the UE100 to MSC / MGW1300 perform communication using the CS network, and the MSC / MGW1300 to UE102 perform communication using the PS network (ST1404 shown in FIG. 15).

0125Next, UE102 hands over to the CS network (SRVCC handover) (processing equivalent to ST200 (SRVCC processing) shown in FIG. 10). In addition, UE102 hands over to the CS network and establishes a connection with the CS network (processing equivalent to ST204 processing (connection establishment processing) shown in FIG. 10).

0126Simultaneously with the processing of ST200 and ST204, the signaling generator 1506 of the MSC / MGW1302 generates the IMS signaling to be transmitted to the MSC / MGW1300 and transmits it via the transmitter 1502 (ST1406 shown in FIG. 15). At this time, the signaling generation unit 1506 includes information indicating that the IMS signaling is the IMS signaling generated by the SRVCC handover in the IMS signaling. For example, the information indicating that the IMS signaling is generated by the SRVCC handover may be STN-SR (Session Transfer Number for SRVCC) or the like described in Non-Patent Document 3.

0127In addition to the codec (codec A) used by UE102 in the PS network, the signaling generator 1506 of the MSC / MGW1302 supports the CS network on its own network (the CS network to which the MSC / MGW1302 belongs). Include a list of codecs in the IMS signaling (ST1406 shown in Figure 15). At this time, the signaling analysis unit 1504 waits for the connection establishment process of ST204, analyzes the signaling related to the connection establishment, obtains the codec information used by the UE 102 in the CS network, and then the signaling generation unit 1506 obtains this codec information. It may be explicitly included in the IMS signaling.

0128The receiving unit 1500 of the MSC / MGW1300 receives the IMS signaling from the MSC / MGW1302 and outputs it to the signaling analysis unit 1504. By analyzing this IMS signaling, the signaling analysis unit 1504 identifies that the UE 102 has performed the SRVCC handover, and outputs information indicating that the UE 102 has performed the SRVCC handover to the terminal position determination unit 1508. In addition, the signaling analysis unit 1504 outputs a list of codecs included in this IMS signaling (SDP offer) (a list of codecs supported by the CS network to which the MSC / MGW1302 belongs) to the codec selection unit 1510. The terminal position determination unit 1508 determines that both UE100 and 102 are present in the CS network because UE102 performs SRVCC handover. The codec selection unit 1510 is used by using the determination result of the terminal position determination unit 1508 and the codec information (codec list) supported by the CS network to which the MSC / MGW1302 belongs, which is input from the signaling analysis unit 1504. Select the codec to use (ST1406 shown in Figure 15).

0129Further, the route selection unit 1512 selects a route through which communication data passes based on the determination result of the terminal position determination unit 1508 (ST1406 shown in FIG. 15). As a result, communication between UE100 and UE102 takes place through the selected route (ST1408 shown in FIG. 15).

0130Next, FIG. 16 shows an example of a codec selection method in the codec selection unit 1510 of the MSC / MGW1300 shown in FIGS. 13 and 15.

0131In ST1600 shown in FIG. 16, the codec selection unit 1510 determines whether or not both terminals (UE100, 102) in communication move (exist) to the CS network based on the determination result of the terminal position determination unit 1508. to decide.

0132When both terminals during communication are moving to the CS network (ST1600: YES), in ST1602, the codec selection unit 1510 sends the IMS signaling received by the reception unit 1500 to the communication partner terminal (UE102) on the CS network. Determine if the codec information to be used (list of codecs) is included.

0133When the IMS signaling includes the codec information used by the communication partner terminal in the CS network (ST1602: YES), in ST1604, the codec selection unit 1510 has the codec information used by the communication partner terminal (UE102) in the CS network. Determine if the terminal (UE100) on the network side matches the codec in use. If the above codec information matches the codec being used by the terminal (UE100) on the own network side, the process proceeds to ST1614.

0134When both terminals during communication have not moved to the CS network (ST1600: NO), in ST1606, the codec selection unit 1510 corresponds to the codec used in the PS network by its own device (MSC / MGW1300). Judge whether or not. If your device (MSC / MGW1300) does not support the codec used in the PS network (ST1606: NO), proceed to ST1612 processing.

0135If the IMS signaling does not include the codec information used by the communication partner terminal in the CS network (ST1602: NO), or if the own device (MSC / MGW1300) supports the codec used in the PS network, ST1608 In, the codec selection unit 1510 determines whether or not the codec information (codec list) provided by IMS signaling (SDP offer) includes the codec currently being used by the UE (UE100) on the own network side. to decide. If the offered codec list includes the codec currently in use by the UE (UE100) on the own network side (ST1608: YES), the process proceeds to ST1614.

0136If the offered codec list does not include the codec currently in use by the UE (UE100) on the own network side (ST1608: NO), in ST1610, the codec selection unit 1510 performs IMS signaling (SDP offer). Determines if the codec list offered by is included in the codec list supported by your device (MSC / MGW1300). If the provided codec list includes codecs supported by your device (ST1610: YES), proceed to ST1616 processing. If the provided codec list does not include the codecs supported by your device (ST1610: NO), proceed to ST1618 processing.

0137In ST1612, the codec selection unit 1510 selects the codec used in the PS network.

0138In ST1614, the codec selection unit 1510 selects the codec being used by the terminal (UE100) on the own network side as the codec to be used.

0139In ST1616, the codec selection unit 1510 selects the codec to be used from the codecs supported by its own device (MSC / MGW1300) from the provided codec list.

0140In ST1618, the codec selection unit 1510 selects an error.

0141In this way, the MSC / MGW1300,1302 includes the list of codecs supported by the CS network on the own network side in the IMS signaling generated by the handover. Upon receiving the IMS signaling, the MSC / MGW1300 (MSC / MGW1302) first determines that both terminals in communication exist in the CS network. Furthermore, the MSC / MGW1300 (MSC / MGW1302) selects the codec to be used by using the codec information supported by the CS network to which the MSC / MGW of the IMS signaling destination belongs. Specifically, the MSC / MGW1300,1302 is designed so that when both terminals (UE100,102) in communication can use the same codec, both terminals use the same codec. Select the codec to use.

0142That is, when one terminal (UE100) hands over to the CS network and the other terminal (UE102) hands over to the CS network, for example, the MSC / MGW1300 belonging to the CS network on the UE100 side becomes the CS network on the UE102 side. Receive a message from the MSC / MGW1302 to which it belongs, including the codec list (codec group) supported by the CS network on the UE102 side, and use the above codec list and the codec used by UE100 (codec after change). Select the codec used by UE102. For example, the MSC / MGW1300 selects the codec used by the UE100 as the codec used by the UE102 when the received codec list includes the codec used by the UE100 (the modified codec).

0143As a result, both terminals (UE100,102) use the same codec if possible, so transcoding is not performed on the MSC / MGW1300,1302. Therefore, according to the present embodiment, even when both UE100 and UE102 during communication perform SRVCC handover, transcoding in MSC / MGW1300, 1302 can be minimized.

0144Further, in the first embodiment, a method has been described in which the MSC / MGW300 detects a change in the codec bandwidth and transmits a signaling requesting the UE 102 to limit the bandwidth of the input signal to be encoded. On the other hand, in the present embodiment, the MSC / MGW1300,1302 is used for signaling that requests the limitation of the bandwidth of the input signal to be encoded after the terminal on the own network side obtains the codec information used in the CS network. Instead, the codec information is explicitly included in the IMS signaling and transmitted to the communication partner terminal. Even in this case, as in the first embodiment, the bandwidth of the codec between the UEs can be maintained to be the same even if the network condition of one or both UEs changes.

0145If the terminal position determination unit 1508 determines that both UE100 and 102 are present in the CS network, the route selection unit 1512 may switch all the routes on the network side to the routes for the CS network. As this determination method, the terminal position determination unit 1508 may determine, for example, whether or not both terminals support rSRVCC. That is, when both terminals (UE100, 102) do not support rSRVCC, the route selection unit 1512 may switch the route on the network side to the route for the CS network. Whether or not both terminals support rSRVCC can be realized by the same method as the method of registering SRVCC support or obtaining whether or not SRVCC is supported described in Non-Patent Document 3.

0146Further, the terminal (for example, UE102 shown in FIG. 17) receives a signaling or the like requesting a limitation of the bandwidth of the input signal to be encoded, and the communication partner terminal (for example, UE100 shown in FIG. 17) performs a handover by SRVCC. When it is determined that this is the case, communication is performed with the own network side MSC / MGW (for example, MSC / MGW1310 shown in FIG. 17) by signaling (ST200 or ST204 shown in FIG. 15) when the own device performs handover by SRVCC. It may be notified that the other party terminal (UE100) has already performed the handover by SRVCC. As a result, the terminal position determination unit 1508 of the MSC / MGW1310 determines that both terminals (UE100,102) have handed over to the CS network, and supports only the PS network in the codec list of IMS signaling (SDP offer). It is possible to avoid including the codec that is being used. In other words, the MSC / MGW1310 can only include codecs supported by the CS network in the SDP offer (see Figure 17). At this time, the MSC / MGW 1310 may explicitly inform that the own device is an MGW (see, for example, FIG. 17). Further, the MSC / MGW1300 that has received the above notification may decide to communicate with each other in the CS network (see, for example, FIG. 17). Further, the above notification may be included in the existing signaling transmitted from the UE 102 when the UE 102 hands over to the CS network, or may be a new signaling. Further, the above notification may be included in the signaling transmitted to the MME (not shown) before the UE 102 hands over to the CS network (see, for example, Non-Patent Document 4).

0147(Embodiment 4) In the present embodiment, both UEs that communicate with each other perform a handover from the PS network to the CS network by the eSRVCC method, or one UE performs a handover from the PS network to the CS network by the eSRVCC method and the other UE. Describes the case where the SRVCC method is used to perform a handover from the PS network to the CS network. In the present embodiment, in the eSRVCC method, it is assumed that the communication data is anchored by ATGW and transcoding is performed by ATGW.

0148FIG. 18 is a configuration showing a part of the mobile communication network according to the fourth embodiment of the present invention. The operation of each node shown in FIG. 18 is as described above (for example, FIGS. 3 and 5).

0149In FIG. 18, both UE100 and UE102 first exist in e-UTRAN and perform VoLTE communication on the PS network. At this time, it is assumed that the above-mentioned codec A (codec whose bandwidth is not necessarily specified) is used. In FIG. 18, it is assumed that both the network on the UE100 side and the network on the UE102 side support eSRVCC. From this, the current communication paths between UE100 and UE102 are Path A, Path B, and Path C via ATCF / ATGW1700 and ATCF / ATGW1702.

0150Although ATCF / ATGW1700,1702 are represented as one node in FIG. 18, they may be separate nodes. Further, in FIG. 18, when the network on the UE100 side does not support eSRVCC, ATCF / ATGW1700 and Path B do not exist as communication paths between UE100 and UE102, so Path A is UE100 and ATCF /. Established with ATGW1702. Similarly, if the network on the UE102 side does not support eSRVCC, ATCF / ATGW1702 and Path B do not exist as communication paths, so Path C is established between UE102 and ATCF / ATGW1700.

0151Next, it is assumed that each of UE100 and UE102 performs a handover by eSRVCC. In this case, according to Non-Patent Document 3, the communication path between UE100 and UE102 after handover is Path D, Path E, Path via MSC / MGW1704, ATCF / ATGW1700, ATCF / ATGW1702 and MSC / MGW1706. B, Path G, and Path F.

0152In FIG. 18, when the network on the UE100 side does not support eSRVCC, ATCF / ATGW1700 and Path B do not exist as communication paths between UE100 and UE102, so Path E is MSC / MGW1704 and ATCF. Established with / ATGW1702. Similarly, if the network on the UE102 side does not support eSRVCC, ATCF / ATGW1702 and Path B do not exist as communication paths between UE100 and UE102, so Path G is MSC / MGW1706 and ATCF / ATGW1700. Established between and.

0153Here, for example, it is assumed that both codecs used when UE100 and 102 hand over to the CS network are AMR-WB. In this case, the communication data from UE100 to ATCF / ATGW1700 is encoded by AMR-WB. The ATGW1700 then transcodes from AMR-WB to codec A. Therefore, the communication data between ATGW1700 and ATGW1702 is encoded by codec A. The ATGW1702 then transcodes from codec A to AMR-WB again. Therefore, the communication data between ATG W1702 and UE 102 is encoded by AMR-WB.

0154If the network on the UE100 side does not support eSRVCC, transcoding is performed by MSC / MGW1704 instead of ATGE1700. Similarly, if the network on the UE102 side does not support eSRVCC, transcoding is performed by MSC / MGW1706 instead of ATGE1702.

0155In the present embodiment, both UE100 and UE102 during communication perform a handover from the PS network to the CS network by the eSRVCC method, or one UE performs a handover from the PS network to the CS network by the eSRVCC method and the other. In the case where the UE of the above performs handover from the PS network to the CS network by the SRVCC method, a method of minimizing transcoding will be described as in the third embodiment.

0156First, the ATCF / ATGW1700, 1702, and UE100, 102 shown in FIG. 18 will be described.

0157FIG. 19 is a block diagram showing the configurations of ATCF / ATGW1700 and 1702 according to the present embodiment. The ATCF / ATGW1700 and 1702 shown in FIG. 19 may include the functional block shown in FIG. 8 or other functional blocks in addition to the functional blocks shown in FIG.

0158In the ATCF / ATGW1700 and 1702 shown in FIG. 19, the receiving unit 1900 receives communication data, signaling, and the like.

0159The transmission unit 1902 transmits communication data, signaling, and the like.

0160The signaling analysis unit 1904 analyzes signaling for SRVCC processing or eSRVCC processing, IMS signaling (IMS signaling), and the like. The signaling analysis unit 1904 notifies the signaling analysis result to the signaling generation unit 1906, the terminal position determination unit 1908, and the codec selection unit 1910.

0161The signaling generation unit 1906 generates signaling based on the signaling analysis result of the signaling analysis unit 1904 and the like.

0162The terminal position determination unit 1908 determines whether both terminals (UE100, 102) in communication exist in the PS network or the CS network based on the signaling analysis result of the signaling analysis unit 1904. The terminal position determination unit 1908 outputs the determination result to the codec selection unit 1910 and the route selection unit 1912.

0163The codec selection unit 1910 selects a codec to be used or a codec candidate based on the signaling analysis result of the signaling analysis unit 1904 and the determination result of the terminal position determination unit 1908.

0164The route selection unit 1912 selects a route through which communication data passes based on the determination result of the terminal position determination unit 1908 .

0165FIG. 20 is a block diagram showing the configurations of UE 100 and 102 according to the present embodiment. UE100, 102 may include the functional block shown in FIG. 12 or other functional blocks in addition to the functional blocks shown in the figure. In UEs 100 and 102 shown in FIG. 20, the receiving unit 700 and the transmitting unit 702 are components that perform the same operations as in FIG. 12, and the description thereof will be omitted.

0166In UEs 100 and 102 shown in FIG. 20, the communication partner codec change detection unit 2000 detects that the codec used by the communication partner has changed. The reason why the codec used by the communication partner is changed is, for example, that the PS network has been moved to the CS network. Further, the method of detecting the codec change in the communication partner codec change detection unit 2000 is, for example, a method of receiving signaling such as a band limitation notification from the network as shown in the first embodiment and a method of detecting the codec change in the second embodiment. Such a method of detecting that the band of the codec used by the communication partner is limited can be mentioned.

0167When the communication partner codec change detection unit 2000 detects that the communication partner codec has changed, the signaling generation unit 2002 generates signaling for notifying the network that the communication partner codec has changed. ..

0168Next, an example of the operation of UE100, 102 and ATCF / ATGW1700, 1702 in this embodiment will be described. Here, it is assumed that both the network on the UE100 side and the network on the UE102 side support eSRVCC.

0169FIG. 21 is a sequence chart showing the operation of each device of the mobile communication network shown in FIG.

0170When UE100 and UE102 perform connection processing to e-UTRAN and register VoLTE with IMS, for example, information on ATCF (ATCF / ATGW1700,1702) is sent to SCC AS, HSS (not shown) or MME (not shown). (Not shown), and the information is retained at the destination (see, for example, Non-Patent Document 5). Further, at the time of making a call (in this embodiment, it is assumed that the call is made from UE100 to UE102. The same applies to the case of making a call from UE102 to UE100). Determines whether to anchor the session at ATGW (see, eg, Non-Patent Document 3 or Non-Patent Document 5).

0171After that, both UE100 and UE102 are connected to e-UTRAN and perform VoLTE communication. At this time, it is assumed that the above-mentioned codec A (codec whose bandwidth is not necessarily specified) is used as the voice codec (ST1800 shown in FIG. 21).

0172Next, the UE 100 hands over from the PS network to the CS network. At this time, the same processing as the ST200 processing (SRVCC processing) and ST204 processing (connection establishment processing) shown in FIG. 10 is performed. Further, at the same time as the processing of ST200 and the processing of ST204, the same processing as the processing of ST1102 shown in FIG. 4 is performed. As a result, the data communication path between UE100 and UE102 is switched via MSC / MGW1704 (ST1802 shown in FIG. 21).

0173At this time, the signaling generation unit 1906 of the ATCF / ATGW1700 generates a message including the codec (for example, AMR) used by the UE 100 in the CS network, and notifies the SCC AS / CSCF1708 of the message via the transmission unit 1902 ( ST1802') shown in Fig. 21. This notice may be given together with the Access Transfer Update message described in Non-Patent Document 3. After that, as shown in the first embodiment, the ATCF / ATGW1700 may send a bandwidth limitation notification to the UE 102.

0174The communication partner codec change detection unit 2000 of UE102 detects that the codec of UE100 has been changed from codec A (ST1804 shown in FIG. 21).

0175Next, UE102 also hands over from the PS network to the CS network. At this time, the signaling generation unit 2002 of UE102 generates signaling for notifying the network that the codec of UE100, which is the communication partner, has been changed. This signaling may be included in the existing signaling transmitted from the UE 102 when the UE 102 is handed over to the CS network, or may be included in the new signaling (ST1806 shown in FIG. 21). Further, the above notification may be included in the signaling transmitted to the MME (not shown) before the UE 102 hands over to the CS network, and the MME may notify the MSC / MGW1706 (for example, Non-Patent Document 4). reference).

0176Upon receiving the signaling from UE102, MSC / MGW1706 detects that the codec of UE100, which is the communication partner of UE102, has changed, and provides information indicating that the codec of UE100 has changed, ATCF / ATGW1702. Include in INVITE messages sent to.

0177Upon receiving this INVITE message, the signaling analysis unit 1904 of ATCF / ATGW1702 detects that the codec of UE100, which is the communication partner of UE102, has been changed. Therefore, the signaling generation unit 1906 of the ATCF / ATGW1702 generates a signaling for the codec query of the UE100 to the SCC AS / CSCF1708, and transmits the signaling via the transmission unit 1902 (ST1808 shown in FIG. 21). ..

0178The receiver 1900 of ATCF / ATGW1702 receives the reply signaling for the signaling transmitted by ST1808 from SCC AS / CSCF1708. Then, the signaling analysis unit 1904 of ATCF / ATGW1702 analyzes this reply signaling and negotiates a codec with ATCF / ATGW1700 based on the analysis result (information about the codec of UE100) (ST1810 shown in FIG. 21). , Select the codec (ST1812 shown in Figure 21). Note that codec negotiations may take place between ATCF / ATGW1702 and SCC AS / CSCF1708, and between SCC AS / CSCF1708 and ATCF / ATGW1700 (ie, anchored at SCC AS). Note that ATCF / ATGW1700,1702 may perform codec negotiation without going through SCC AS / CSCF1708. In this case, the processing of ST1802 and the processing of ST1808 shown in FIG. 21 are not required.

0179In this way, when the terminal (UE100,102) is handed over, the ATCF / ATGW1700,1702 generates a message including the codec used by the handover terminal in the CS network, and notifies the SCC AS / CSCF1708 of the message. .. In this case, the communication partner terminal communicating with the handover terminal detects that the codec of the handover terminal has been changed. In addition, in ATCF / ATGW1700,1702, when the communication partner terminal that detects that the codec of the handover terminal has been changed is also handed over, the codec of the terminal that was first handed over is changed by the notification from the communication partner terminal. When it is detected that it is, SCC Inquires about the codec of the communication partner to AS / CSCF1708. Then, the ATCF / ATGW1700,1702 negotiates a codec and selects a codec based on the information about the codec (the codec of the terminal that was first handed over) obtained by the inquiry. For example, ATCF / ATGW1700,1702 is a codec to be used so that when both terminals (UE100,102) in communication can use the same codec, the same codec is used by both terminals. Select.

0180That is, when one terminal (UE100) hands over to the CS network and then the other terminal (UE102) hands over to the CS network, the ATCF / ATGW1702 is a codec used by the UE100 in response to an inquiry to SCC AS / CSCF1708. Receive a message including (codec after change), receive a message from MSC / MGW1706 on the UE102 side, including information indicating that UE100 has handed over to the CS network, and information indicating that UE100 has handed over to the CS network. Is received, the codec used by UE102 is selected based on the codec used by UE100.

0181As a result, in both terminals (UE100,102), the same codec is used if possible, as in the third embodiment, so that transcoding is not performed in ATCF / ATGW1700,1702. Therefore, according to the present embodiment, when both UE100 and UE102 during communication perform overload from the PS network to the CS network by the eSRVCC method, transcoding can be minimized as in the third embodiment. it can.

0182If the terminal position determination unit 1908 determines that both UE100 and 102 are present in the CS network, the route selection unit 1912 may switch all the routes on the network side to the routes for the CS network. As this determination method, the terminal position determination unit 1908 may determine, for example, whether or not both terminals support rSRVCC. That is, when both terminals (UE100, 102) do not support rSRVCC, the route selection unit 1912 may switch the route on the network side to the route for the CS network. Whether or not both terminals support rSRVCC can be realized by the same method as the method of registering SRVCC support or obtaining whether or not SRVCC is supported described in Non-Patent Document 3.

0183Further, the terminal (for example, UE102 shown in FIG. 21) receives a signaling or the like requesting the limitation of the bandwidth of the input signal to be encoded, and the communication partner terminal (for example, UE100 shown in FIG. 21) hands over by SRVCC or eSRVCC. When it is determined that the above has been performed, the signal (ST200 / ST204 shown in FIG. 21) when the own device performs the handover by eSRVCC is used to the MSC / MGW on the own network side (for example, MSC / MGW1706 shown in FIG. 21). , The communication partner terminal (UE100) may notify that the handover by SRVCC or eSRVCC has already been performed. As a result, the terminal position determination unit 1908 of MSC / MGW1706 determines that both terminals (UE100,102) have handed over to the CS network, and supports only the PS network in the codec list of IMS signaling (SDP offer). It is possible to avoid including the codec that is being used. This notification may be included in the existing signaling sent from the UE 102 when the UE 102 hands over to the CS network, or may be a new signaling (ST1806 shown in FIG. 21). Further, the above notification may be included in the signaling transmitted to the MME (not shown) before the UE 102 hands over to the CS network (see, for example, Non-Patent Document 4).

0184Further, as shown in FIG. 19, the MSC / MGW1704,1706 may have the same functions as the ATCF / ATGW1700,1702. In FIG. 18, when the network on the UE100 side does not support eSRVCC, the signaling analysis unit 1904 of the MSC / MGW1704 analyzes the signaling including the codec used in the CS network when the UE100 hands over to the CS network. , Get information on the codec used by UE100 in the CS network. Next, the signaling generator 1906 of the MSC / MGW1704 generates information on the codec used by the UE 100 in the CS network, and SCC. Notify AS / CSCF1708. This notification may be included in the INVITE message. Further, in FIG. 18, when the network on the UE102 side does not support eSRVCC, the signaling analysis unit 1904 of the MSC / MGW1706 notifies from the UE102 that the codec of the UE100, which is the communication partner, has been changed. When it receives signaling including, it detects that the codec of UE100, which is the communication partner of UE102, has been changed. Next, the signaling generator 1906 of the MSC / MGW1706 generates a signal for inquiring the UE100 codec to the SCC AS / CSCF1708 and transmits it to the SCC AS / CSCF1708. SCC Upon receiving the reply signaling from AS / CSCF1708, the signaling analysis unit 1904 of the MSC / MGW1706 analyzes this reply signaling and transcodes on the UE100 side based on the analysis result (MSC / MGW1704 or ATCF / ATGW1700). Negotiate a codec with and select a codec. The codec negotiation may be performed between MSC / MGW1706 and SCC AS / CSCF1708, and between SCC AS / CSCF1708 and the node that transcodes on the UE100 side (that is, anchored by SCC AS). May be). As a result, even when one UE performs a handover from the PS network to the CS network by the eSRVCC method and the other UE uses the SRVCC method, transcoding can be minimized as in the third embodiment.

0185(Embodiment 5) In the first, third, and fourth embodiments, when the MSC / MGW or ATCF / ATGW detects a change in the bandwidth of the communication data of one UE during the session, the method of notifying the other UE of the bandwidth limitation. Explained. On the other hand, in the present embodiment, instead of sending the bandwidth limitation notification, or in addition to sending the bandwidth limitation notification, the communication data sent by MSC / MGW or ATCF / ATGW, or the header part of the RTP payload of the communication data. Explain how to explicitly include the bandwidth information in.

0186For example, in the first embodiment, the codec bandwidth detection unit 606 of the MSC / MGW300 detects the bandwidth change of the UE100, and the change determination unit 608 can limit the bandwidth of the input signal encoded to the UE102. Moreover, when it is determined that the bandwidth limitation is necessary, the bandwidth of the communication data sent from the MSC / MGW300 to the UE102 is also limited. At this time, the changed bandwidth information is explicitly included in the communication data itself sent by the MSC / MGW300 or the payload header part of the RTP in which the communication data is stored.

0187When the band information after the change is included in the RTP payload header part, the packets including the band information are limited to the packets sent in a certain period (for example, 200 msec) after the band change, or a certain number of packets (for example, 10 packets). ..

0188When the receiving side (UE102) detects that bandwidth information is added to the payload header of a certain number of RTPs for a certain period of time (for example, 150 msec or more) or a specific number of RTPs (for example, 5 packets or more), the RTP sent after that. Even if the bandwidth information is not added to the payload header, it is determined that the bandwidth of the stored communication data will continue to be limited.

0189Similarly, when the UE 102 that receives the bandwidth limitation notification transmits the bandwidth-limited communication data to the MGW300, the packets sent in a certain period (for example, 200 msec) or a certain number of packets (for example, 10 packets) Bandwidth information is added to the RTP payload header. When the receiving side (MGW300) detects that bandwidth information is added to the payload header of a certain number of RTPs for a certain period of time (for example, 150 msec or more) or a specific number of RTPs (for example, 5 packets or more), the RTP sent after that. Even if the bandwidth information is not added to the payload header, it is determined that the bandwidth of the stored communication data will continue to be limited.

0190Further, in the second embodiment, instead of receiving the bandwidth limitation notification, the data analysis unit 1200 of the UE 102 detects that the bandwidth of the data itself is limited for a certain period of time or more, and limits the bandwidth of the data to be transmitted. The method was explained. Instead of this, the above-mentioned method of the present embodiment (bandwidth information is added to the payload header of a certain number of RTPs (for example, 5 packets or more) or a certain number of times (for example, 150 msec or more)) is used. Then, the codec mode change unit 1202 may decide to change the band.

0191Further, in the first, third and fourth embodiments, the bandwidth limitation notification itself may be included in the RTP payload header. Even when the bandwidth limitation notification is included in the RTP payload header, the number of packets including the bandwidth limitation notification is a certain number of packets sent in a certain period (for example, 100 msec) after it is determined that the bandwidth change notification is necessary. Packets (for example, 5 packets). When the receiving side (UE102) detects that a bandwidth limitation notification is added to the payload header of a certain number of RTPs (for example, 1 packet or more) or for a certain period of time (for example, 20 msec or more), it is sent after that. Even if the bandwidth limit notification is not added to the RTP payload header, it is determined that the notification has been requested to limit (change) the bandwidth. When the bandwidth limitation notification is included in the RTP payload header, the above-mentioned bandwidth information may be included together with the bandwidth limitation notification.

0192As a result, it is possible to explicitly notify the communication partner of the change in the bandwidth of the transmitted data even during the session.

0193Each embodiment of the present invention has been described above.

0194In each of the above embodiments, ATCF / ATGW, MSC / MGW, and SCC AS / CSCF have been described as one node, but they may be separate nodes. That is, one or both of the above-mentioned functions may be provided between ATCF and ATGW, between MSC and MGW, and between SCC AS and CSCF, respectively. In addition, necessary information may be exchanged between ATCF and ATGW, between MSC and MGW, and between SCC AS and CSCF.

0195Further, in each of the above embodiments, when both UE100 and UE102 support handover to the CS network (handover by SRVCC, eSRVCC, etc.), the CS network is used when negotiating a session on the PS network. A codec that is compatible with a supported codec or a codec supported by the CS network may be selected from the beginning.

0196Further, in each of the above-described embodiments, a codec related to voice has been mainly described. However, the present invention is not limited to this, and the present invention can be applied to music, sound, images, and the like.

0197Further, the present invention is not limited to each of the above embodiments, and can be implemented with various modifications.

0198Further, in each of the above embodiments, the case where the present invention is configured by hardware has been described as an example, but the present invention can also be realized by software in cooperation with hardware.

0199Further, each functional block used in the description of each of the above embodiments is typically realized as an LSI which is an integrated circuit. These may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of them. Although it is referred to as LSI here, it may be referred to as IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

0200Further, the method of making an integrated circuit is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. After manufacturing the LSI, a programmable FPGA (Field Programmable Gate Array) or a reconfigurable / processor that can reconfigure the connection or setting of the circuit cells inside the LSI may be used.

0201Furthermore, if an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology or another technology derived from it, it is naturally possible to integrate functional blocks using that technology. There is a possibility of applying biotechnology.

0202The specification contained in the Japanese application of Japanese Patent Application No. 2011-129422, filed on June 9, 2011, Japanese Patent Application No. 2011-247330, filed on November 11, 2011, and Japanese Patent Application No. 2012-030419, filed on February 15, 2012. All disclosures of drawings and abstracts are incorporated herein by reference.

0203The present invention has a function of adjusting the bandwidth or encoding bit rate of the encoded input signal of the codec used by the communication partner when the codec used by one of the communication terminals during communication is changed. It is useful for suppressing quality deterioration due to coding.

0204100,102 UE 200,202,204,206,1100,1102,1104,1106 Signaling 300,1300,1302,1310,1704,1706 MSC / MGW 1120,1700,1702 ATCF / ATGW 600,700,1500,1900 Receiver 602,702,1502,1902 Transmitter 604 Codec detector 606 Codec Bandwidth Detector 608 Change Judgment Department 610,1506,1906,2002 Signaling generator 612 Transcoding section 704 Codec Negotiation Department 706,1510,1910 Codec selection 708 Bandwidth determination unit 710,1504,1904 Signaling analysis department 712,1202 Codec mode change part 1200 Data Analysis Department 1508,1908 Terminal position determination unit 1512,1912 Route selection section 1708 SCC AS / CSCF 2000 Communication partner codec change detector