WO2012019532A1 - 一种实现会话锚定的方法和系统 - Google Patents

一种实现会话锚定的方法和系统 Download PDF

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Publication number
WO2012019532A1
WO2012019532A1 PCT/CN2011/078124 CN2011078124W WO2012019532A1 WO 2012019532 A1 WO2012019532 A1 WO 2012019532A1 CN 2011078124 W CN2011078124 W CN 2011078124W WO 2012019532 A1 WO2012019532 A1 WO 2012019532A1
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Prior art keywords
anchor
session
user
anchoring
information
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PCT/CN2011/078124
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English (en)
French (fr)
Inventor
邹常乐
李振东
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中兴通讯股份有限公司
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Publication of WO2012019532A1 publication Critical patent/WO2012019532A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/1066—Session management
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L67/00—Network arrangements or protocols for supporting network services or applications
    • H04L67/14—Session management
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L67/00—Network arrangements or protocols for supporting network services or applications
    • H04L67/2866—Architectures; Arrangements
    • H04L67/30—Profiles
    • H04L67/306—User profiles
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/20—Manipulation of established connections

Definitions

  • the present invention relates to the field of communications, and in particular, to a method and system for implementing session anchoring. Background technique
  • 3G mobile communication networks such as Global System for Mobile communications (GSM), Universal Mobile Telecommunications System (UMTS), and Circuit Switch (CS) Business, and formed a good coverage.
  • GSM Global System for Mobile communications
  • UMTS Universal Mobile Telecommunications System
  • CS Circuit Switch
  • the packet switching (PS) network carries voice and other services, and can directly access the Internet Protocol (IP) multimedia subsystem (IP Multimedia Core Network Subsystem, IMS), the IMS provides communication services including voice services.
  • IP Internet Protocol
  • IMS IP Multimedia Core Network Subsystem
  • LTE/SAE Long Term Evolution/System Architecture Evolution
  • IMS IP-based network architecture proposed by 3GPP. It builds an open and flexible service environment. It is independent of access and can support multimedia applications and provide users with rich multimedia services.
  • the control layer and the service layer are separated.
  • the control layer does not provide specific services, and only provides the necessary triggering, routing, and accounting functions to the service layer.
  • the service triggering and control functions in the control layer are completed by the Call Session Control Function (CSCF).
  • CSCF Call Session Control Function
  • the CSCF is divided into a proxy CSCF (P-CSCF), a check CSCF (I-CSCF), and a monthly advisory CSCF ( S-CSCF) Three types, of which the primary responsibility is S-CSCF, and the I-CSCF type is optional.
  • the service layer is composed of a series of application servers (ASs) that can provide specific service services.
  • the AS can be an independent entity or exist in the S-CSCF.
  • the control layer S-CSCF controls the service trigger according to the subscription information of the user, invokes the service on the AS, and implements the service function.
  • AS and S-CSCF can be collectively referred to as service equipment (SE, Server Equipment).
  • SE service equipment
  • SE Server Equipment
  • the end-to-end device in the session is called User Equipment (UE), which is responsible for interaction with users. Some UEs have multiple accesses.
  • the network mode includes accessing the network through the PS domain of 3GPP, accessing the network through other non-3GPP data domains, and even accessing the network through the CS domain.
  • the CS network and the PS network can be used as the network.
  • An access method of the IMS network that is, the user can establish an IMS session through the LTE/S AE or the CS, and the IMS provides various types of service control, and the LTE/SAE or the CS provides the network access for the user.
  • the UE communicates with each entity in the IMS network using a standard Session Initiation Protocol (SIP).
  • SIP Session Initiation Protocol
  • the network may decide to anchor the session to a logical functional entity.
  • FIG. 1 is a service scenario in which a UE anchors all sessions when a UE establishes a session through an LTE/SAE access network.
  • the user When the user performs voice service in the source radio access coverage area, the user directly accesses the IMS, establishes an IMS session with the remote user, and the signaling part of the session is anchored to the access handover control function entity of the currently camped network (Access Transfer On the Control Function, ATCF, the media part is anchored on the access gateway (AGW) controlled by the access handover control function entity.
  • ATCF Access Transfer On the Control Function
  • ATCF Access Transfer On the Control Function
  • the media part is anchored on the access gateway (AGW) controlled by the access handover control function entity.
  • AGW access gateway
  • the ATCF and the AGW controlled by the ATCF are combined.
  • the UE and the remote end establish a session anchored on the ATCF (Signaling Anchor) and AGW (Media Anchor) of the UE currently camping on the network, and the AGW is controlled by the ATCF:
  • the UE is responsible for interacting with the user, and can establish a session through different access modes such as PS/CS;
  • the ATCF is responsible for anchoring the signaling part of the UE session and controlling the AGW to anchor the media part of the user session;
  • the ATCF is a logical functional entity, and the actual physical location may be located in a certain network element on the signaling path when the UE performs IMS registration by visiting the network LTE/SAE, such as P-CSCF/IBCF (Interconnection Border Control Function). Wait.
  • P-CSCF/IBCF Interconnection Border Control Function
  • the AGW is responsible for anchoring the media part of the UE session under the control of the ATCF;
  • the AGW can be located at the TrGW (Transition Gateway) of the visited place, the PDN GW or the P-GW (Packet Data Network Gateway), the MGW (Media Gateway) of the CS domain or the IMS domain, etc. Flexible deployment based on actual conditions.
  • the IMS is responsible for processing a session established by the UE through various access networks, including an initial call session. And the terminating session, etc., and is responsible for establishing a session with the remote end;
  • the IMS in the figure is located in the home network of the user, and includes network elements such as a CSCF and various ASs, such as a Service Consistency and Continuity Application Server (SCC AS) that provides service consistency and continuity;
  • network elements such as a CSCF and various ASs, such as a Service Consistency and Continuity Application Server (SCC AS) that provides service consistency and continuity;
  • SCC AS Service Consistency and Continuity Application Server
  • the Remote End establishes an IMS session with the UE; the Remote End may be a UE, or may be a server providing a service, such as a streaming media server.
  • FIG. 2 is a flowchart of a session anchoring when an existing UE performs IMS registration through LTE/SAE and establishes a voice session, and the ATCF/AGW anchors a session of the UE when the session is established, and the specific description thereof is as follows:
  • Step 201 The UE initiates an IMS registration request on the current camping network, and the request message arrives.
  • Step 202 The ATCF sends the registration message to the S-CSCF of the user visited place.
  • the ATCF carries the visited session transfer number (Single Session Transfer Number - Single Radio, vSTN-SR) in the registration message;
  • vSTN-SR is used for SRVCC procedures that may occur to subsequent users
  • the registration message in this step needs to first reach the I-CSCF of the user's home location, and the I-CSCF interacts with the Home Subscriber Server (HSS) to determine the S-CSCF serving the user, and then the I-CSCF will The message is routed to the S-CSCF for processing.
  • HSS Home Subscriber Server
  • the I-CSCF and the S-CSCF are described together, and the related process of the HSS is omitted.
  • Steps 203-204 after the S-CSCF processes the registration request, the registration response is returned to the UE through the original path.
  • Step 205 After processing the registration message of the user, the S-CSCF performs third-party registration with the corresponding application server (Application Server, AS) instead of the UE according to the initial filter criterion (iFC); If the user is an SRVCC user, the S-CSCF needs to perform third-party registration with the SCC AS instead of the UE, and carries the vSTN-SR in step 202;
  • AS Application Server
  • the vSTN-SR will be downloaded to the LTE/SAE network element through the HSS advancement process and transmitted to the CS network element by the LTE/SAE network element when the SRVCC process is triggered. It can also be transmitted to the corresponding LTE/SAE or CS network through other means. Yuan to achieve SRVCC;
  • Step 206 The UE initiates an IMS session, and the session request of the IMS session arrives at the ATCF, where the session description protocol (SDP) information of the UE, such as an IP address, a media stream coding format, and a port number, is carried.
  • SDP session description protocol
  • Step 207 The ATCF anchors the session of the user, and anchors the media part to an AGW controlled by the ATGW.
  • the ATCF sends a session request to the S-CSCF, where the SDP information of the AGW is carried;
  • step 208al-209a2 is performed; otherwise, steps 208b-209b are performed;
  • Step 208al According to the trigger of the iFC, the S-CSCF routes the received session request to the SCC AS for processing;
  • Step 208a2 the SCC AS sends the received session request to the remote UE.
  • Step 209al The remote UE returns a session response to the SCC AS, where the SDP information of the remote UE is carried.
  • Step 209a2 The SCC AS sends a session response to the S-CSCF.
  • Step 208b the S-CSCF sends the session request to the remote UE.
  • the call is not triggered to be processed by the SCC AS; according to the iFC, the session request may be triggered to be processed by other ASs, and then returned to the S-CSCF and sent to the remote UE;
  • Step 209b The remote UE returns a session response to the S-CSCF, where the SDP information of the remote UE is carried.
  • Step 210 The S-CSCF returns a session response to the ATCF, where the remote SDP information is carried.
  • the media is divided into two segments, namely: UE to AGW-segment, AGW to remote segment, so that users can provide a better user experience due to certain service needs, for example, if the user is SRVCC
  • the user can be controlled by the ATCF in the subsequent SRVCC handover to reduce the voice interruption time during handover and provide a better user experience.
  • the ATCF/AGW anchor session method in the above call setup process has the following disadvantages: ATCF cannot distinguish whether the user needs to anchor the session, so for all ATCF-enabled sessions, the media plane needs to be anchored on the AGW. For example, for non-SRVCC users, ATCF will also anchor its session. This will cause waste of network resources (such as AGW resources); and because the media of the UE to the remote UE is anchored on the AGW, an anchor point is added in the communication process, which is likely to cause the user's service quality and user experience. Negative Effects. Summary of the invention
  • the main object of the present invention is to provide a method and system for implementing session anchoring to ensure that only anchors that need to be anchored are provided with anchoring, thereby minimizing waste of network resources.
  • a method for implementing session anchoring including:
  • the user information it is preliminarily determined whether an anchor session is required, and an anchor indication is issued at an initial determination that an anchor timing is required; and whether the final decision is to anchor the session according to the anchor indication.
  • the user information is user subscription information
  • the preliminary determining process includes: determining, according to the user subscription information, whether the user is a voice call continuity SRVCC user in a single channel mode, and initially determining that the anchoring is required when the determination result is yes. Conversation.
  • the user information is capability information of the terminal currently used by the user
  • the preliminary determining process includes: Determining whether the terminal currently used by the user is an SRVCC terminal according to the user terminal capability information, and initially determining that an anchor session is required when the determination result is yes.
  • the final decision process includes:
  • the final decision process includes:
  • a system for implementing session anchoring comprising an anchoring preliminary determining unit and an anchoring decision unit;
  • the anchor preliminary determining unit is configured to initially determine whether an anchoring session is required according to the user information, and issue an anchoring instruction to the anchoring decision unit according to a preliminary determination that an anchor timing is required;
  • the anchor decision unit is configured to determine, according to the received anchor indication, whether the session is anchored.
  • the user information is user subscription information, and the anchor preliminary determination unit performs the preliminary determination when:
  • the user information is user terminal capability information, and is used to indicate whether the terminal currently used by the user has SRVCC capability;
  • the anchor preliminary determination unit When the anchor preliminary determination unit performs the preliminary determination, it is further used to:
  • the SRVCC user it is determined according to the user terminal capability information whether the terminal currently used by the user has the SRVCC capability, and when the determination result is yes, it is initially determined that the anchor session needs to be established.
  • the anchor decision making unit performs the final decision when used to:
  • the anchor decision making unit performs the final decision when used to:
  • the method and system for implementing session anchoring of the present invention can ensure that only the sessions that need to be anchored are anchored, thereby minimizing the waste of network resources. Moreover, since anchoring is not performed without anchor timing, there is no unnecessary anchor point, so there is no adverse effect on the user's service quality and user experience due to unnecessary anchor points.
  • FIG. 1 is a schematic structural diagram of call anchoring in a prior art LTE/SAE
  • FIG. 2 is a schematic diagram of a signaling flow of a call anchor in the prior art
  • FIG. 3 is a flowchart of implementing session anchoring according to Embodiment 1 of the present invention.
  • FIG. 5 is a flowchart of implementing session anchoring according to Embodiment 3 of the present invention.
  • FIG. 6 is a schematic flow chart of implementing session anchoring according to the present invention.
  • FIG. 7 is a system diagram of implementing session anchoring according to an embodiment of the present invention. detailed description
  • the network element in the IMS network may provide information such as an anchor prompt for indicating whether anchoring is required to the ATCF, and finally determine whether the anchor session needs to be anchored by the ATCF to avoid causing the network. Waste of resources.
  • FIG. 3 is a flowchart of implementing session anchoring according to Embodiment 1 of the present invention, where the process includes the following steps:
  • Step 301 The UE initiates an IMS registration request in the LTE/SAE, and the request message arrives at the ATCF.
  • Step 302 The ATCF sends the registration request message to the S-CSCF of the user visited place.
  • the ATCF carries the vSTN-SR allocated to the user in the registration request message; Step 303 to step 304: After the S-CSCF processes the registration request, the S-CSCF returns a registration response message to the UE through the original path.
  • Step 305 After processing the registration request message of the user, the S-CSCF performs third-party registration with the corresponding AS according to the iFC, if necessary;
  • Step 306 The UE initiates an IMS session establishment request, where the SDP information of the UE is carried.
  • Step 307 After receiving the session establishment request in step 306, the ATCF forwards the message to the S-CSCF of the IMS network to which the UE belongs.
  • the session establishment request forwarded by the ATCF carries the SDP information of the UE, and the ATCF inserts an indication for anchoring the media of the user session in the session establishment request, indicating that the AGW is not allocated for the call;
  • Step 308 The S-CSCF triggers the call to the SCC AS according to the iFC.
  • Step 309 Since the vSTN-SR is received in step 305, the SCC AS explicitly deploys the ATCF/AGW for anchoring the session.
  • the SCC AS is based on various information, such as whether the user is an SRVCC user (which can be determined by applying user subscription information), UE capability information (this information is used to indicate whether the user currently uses the SRVCC capable terminal), and whether the calling user UE roams. Whether the remote UE roams, the policy configured by the operator, or other factors determine whether the media of the session needs to be anchored at the visited place. If it is determined that anchoring is required, the SCC AS indicates that the call setup request is rejected in the form of sending a reject message to the S-CSCF, etc., indicating that the media that needs to anchor the session is indicated;
  • the refusal message may also carry the determination information on the SCC AS, such as UE capability information, whether the user roams, etc., to provide the ATCF with an anchor decision;
  • the SCC AS determines whether to send a reject message to the ATCF based on various information, and carries an anchor indication. The main judgment is based on whether the user is an SRVCC user. If the user is not an SRVCC user, the user does not need to anchor the session, and thus does not send a rejection message to the ATCF. If the user is an SRVCC user, other factors may be considered comprehensively.
  • ATCF sends a reject message and carries With anchor indication;
  • Step 310 The S-CSCF sends a reject message to the ATCF.
  • Step 311 After receiving the reject message, the ATCF determines whether the media of the session needs to be anchored according to factors such as an anchor indication provided by the message, a local network policy, and UE capability information. The ATCF then initiates a new session establishment request to the UE home IMS network;
  • the SDP information of the AGW is carried in the session establishment request in this step; otherwise, the SDP information of the UE is still carried;
  • the setup request in step 312 carries the SDP information of the AGW or the UE.
  • Step 312 The S-CSCF sends a session establishment request to the SCC AS.
  • Step 313 The SCC AS sends a session establishment request to the remote UE through the S-CSCF.
  • Step 317 The ATCF replies to the UE with a session establishment response, which carries the SDP response information.
  • step 311 if the ATCF allocates the AGW to the session to anchor the media, that is, carries the SDP information of the AGW, the message in step 317 is carried.
  • the SDP of the AGW is sent to the UE. If the ACF does not allocate the AGW to the session to anchor the media, that is, the SDP information of the UE is still carried in the step 311, the ATCF sends the SDP information of the remote UE to the UE.
  • FIG. 4 is a flowchart of implementing session anchoring according to Embodiment 2 of the present invention, where the process includes the following steps:
  • Step 401 The UE initiates an IMS registration request in the LTE/SAE, and the request message arrives at the ATCF.
  • Step 402 The ATCF sends the registration request message to the S-CSCF of the user visited place.
  • the ATCF carries the vSTN-SR allocated to the user in the registration request message;
  • Step 403 to Step 404 after processing the registration request, the S-CSCF replies to the UE with the registration response message through the original path;
  • Step 405 After the S-CSCF processes the registration message of the user, according to the iFC, the third-party registration is performed for the UE to the corresponding AS according to the required time;
  • Step 406 The UE initiates an IMS session establishment request, where the SDP information of the UE is carried.
  • Step 407 After receiving the session establishment request, the ATCF forwards the message to the S-CSCF of the IMS network to which the UE belongs.
  • the session establishment request sent by the ATCF carries the SDP information of the UE, and the ATCF inserts an indication for anchoring the media of the user session in the session establishment request, indicating that the AGW is not allocated for the call;
  • Step 408 The S-CSCF triggers the call to the SCC AS according to the iFC.
  • Step 409 Since the vSTN-SR is received in step 405, the SCC AS explicitly deploys the ATCF/AGW for anchoring the session.
  • the SCC AS determines whether the session needs to be anchored in the visited place according to various information, such as whether the user is an SRVCC user (can be determined according to user subscription information), UE capability information, whether the user roams, an operator configured policy, or other factors. Media. If it is determined that anchoring is required, the SCC AS sends an anchor indication to the S-CSCF indicating the media that needs to anchor the session;
  • the anchor indication can be carried by a temporary response established for the session
  • Step 409a The SCC AS sends a session establishment request to the remote UE through the S-CSCF, and carries the SDP information of the UE.
  • Step 409b The remote UE sends a session establishment response to the SCC AS through the S-CSCF, where the SDP response information of the remote UE is carried.
  • step 409 occurs in parallel with step 409a; step 410, the S-CSCF sends an anchor indication to the ATCF; Step 411: After receiving the anchor indication, the ATCF determines whether the media of the session needs to be anchored according to the anchor indication, the local network policy, the UE capability information, and the like. The ATCF then initiates a session update request to the UE home IMS network;
  • the SDP information of the AGW is carried in step 411; otherwise, the SDP information of the UE is still carried;
  • Step 412 The S-CSCF sends a session update request to the SCC AS.
  • Step 413 If the SDP information in step 412 is different from the SDP information in step 408, the SCC AS sends a session update request to the remote UE through the S-CSCF; otherwise, the SCC AS does not perform step 413, and then no more steps. 414;
  • Step 414 The remote UE sends a session update response to the SCC AS through the S-CSCF, where the new SDP information of the remote UE is carried.
  • Step 415 to step 416 the SCC AS sends a session establishment response to the ATCF through the S-CSCF, where the SDP response information received in step 414 is carried; if the step 413 to step 414 are not performed, the SDP response information in step 409b is carried. ;
  • Step 417 The ATCF returns a session establishment response to the UE.
  • step 411 if the ATCF allocates an AGW for the session to anchor the media, that is, carries the SDP information of the AGW, the message of step 417 carries the SDP of the AGW to the UE; if the ATCF does not allocate the AGW for the session to anchor the media, That is, the SDP information of the UE is still carried in the step 411, and the ATCF sends the SDP information of the remote UE in the step 416 to the UE.
  • FIG. 5 is a flowchart of implementing session anchoring according to Embodiment 3 of the present invention, where the process includes the following steps:
  • Step 501 to step 512 are the same as step 401 to step 412 in FIG. 4, the only difference is that step 409a and step 409b are not included in FIG. 5;
  • Step 513 The SCC AS sends a session establishment request to the remote UE through the S-CSCF, where the SDP information received in step 512 is carried.
  • Step 514 The remote UE sends a session establishment response to the SCC AS through the S-CSCF, where the new SDP information of the remote UE is carried.
  • Step 515 to step 516 the SCC AS sends a session establishment response to the ATCF through the S-CSCF, where the SDP response information received in step 514 is carried;
  • Step 517 The ATCF returns a session establishment response to the UE.
  • step 511 if the ATCF allocates an AGW to the session to anchor the media, that is, carries the SDP information of the AGW, the message of step 517 carries the SDP of the AGW to the UE; if the ATCF does not allocate the AGW for the session to anchor the media, That is, the SDP information of the UE is still carried in the step 511, and the ATCF sends the SDP information of the remote UE in step 516 to the UE.
  • FIG. 6 is a schematic diagram of a process for implementing session anchoring according to the present invention. The process includes the following steps:
  • Step 610 Initially determine whether an anchor session is required according to user information such as user subscription information, and issue an anchor indication at an initial determination that an anchor timing is required. For example, if the user is determined to be an SRVCC user according to the subscription information of the user, or if the UE has the SRVCC capability or the like according to the UE capability information, it is determined that the anchor session is required.
  • user information such as user subscription information
  • Step 620 Determine whether the final decision is to anchor the session according to the anchoring instruction.
  • the operation logic when the operation logic is relatively simple, the final decision can be directly determined upon receiving the anchor indication: an anchor session is required. When the operation logic is relatively complex, it may further determine whether to anchor the session according to factors such as the local network policy, whether the UE has SRVCC capability, or the like after receiving the anchor indication.
  • FIG. 7 is a system diagram of implementing session anchoring according to an embodiment of the present invention, where the system includes a connection initial determination unit and an anchor decision unit.
  • the anchoring preliminary determining unit may be set in a functional entity capable of acquiring user subscription information and performing logical judgment, such as an SCC AS, and the anchoring decision unit may be disposed in a functional entity capable of performing access control on the UE, such as an ATCF.
  • the anchor preliminary determination unit may initially determine whether an anchor session is required according to user information such as user subscription information, and issue an anchor indication to the anchor decision unit in an initial determination of the anchor timing, and may carry some factors affecting the decision. (such as UE capability information, etc.), the anchor decision unit finally decides whether to anchor the session according to the received anchor indication and the like.
  • the anchor decision unit can further trigger subsequent anchor session operations.
  • the method for implementing session anchoring in the present invention ensures that only the anchoring session is anchored, whether it is a method or a system, thereby minimizing the waste of network resources. Moreover, since anchoring is not performed without anchor timing, there is no unnecessary anchor point, so there is no adverse effect on the user's service quality and user experience due to unnecessary anchor points.

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Abstract

本发明公开了一种实现会话锚定的方法和系统，均可根据用户信息初步判定是否需要锚定会话，并在初步判定需要锚定时发出锚定指示；根据锚定指示最终决策是否锚定会话。本发明实现会话锚定的方法和系统，均可保证只对需要锚定的会话提供锚定，因而能够尽量减少网络资源的浪费。并且，由于在不需要锚定时不会进行锚定，因此不存在不必要的锚定点，所以不会因不必要的锚定点对用户的业务质量和用户体验造成不利影响。

Description

一种实现会话锚定的方法和系统 技术领域
本发明涉及通信领域， 具体涉及一种实现会话锚定的方法和系统。 背景技术
在 2G、 3G移动通讯网络中， 如全球移动通讯系统（ Global System for Mobile communications , GSM )、 通用移动通讯系统 ( Universal Mobile Telecommunications System, UMTS ), 釆用电路交换（ Circuit Switch, CS ) 方式提供语音业务， 并形成了良好的覆盖。
由于无线接入网络向分组交换发展，通过分组交换（Packet Switch, PS ) 网络承载语音以及其他业务， 并能够直接接入网络互联协议 （Internet Protocol, IP )多媒体子系统 ( IP Multimedia Core Network Subsystem, IMS ), 由 IMS提供包括语音业务在内通讯业务。 随着多种高速宽带移动接入方式 的出现， 移动通信标准组织提出了被称为 LTE/SAE ( Long Term Evolution/ System Architecture Evolution,长期演进 /系统架构演进）的下一代网络架构， 该网络架构使得演进的无线通信系统能够提供更高的传输速率， 更短的传 输延时， 并具有更低的成本， 同时支持 3GPP ( 3rd Generation Partnership Project , 第三代合作伙伴计划 ) 内部接入系统之间的移动性， 以及 3GPP接 入系统和非 3GPP接入系统之间的移动性等。
随着无线宽带技术以及 IP技术的发展， 整个网络向全 IP的方向演进， 通讯网络的核心网向 IMS演进。
IMS是由 3GPP提出的一种基于 IP的网络架构， 构建了一个的开放而 灵活的业务环境， 与接入无关， 可以支持多媒体应用， 能够为用户提供丰 富的多媒体业务。 在 IMS业务体系中， 控制层和业务层是分离的， 控制层不提供具体业 务， 只向业务层提供必要的触发、 路由、 计费等功能。 控制层中业务触发 和控制功能是呼叫会话控制功能（ Call Session Control Function , CSCF )完 成的， CSCF分为代理 CSCF ( P-CSCF )、查 i句 CSCF ( I-CSCF )和月良务 CSCF ( S-CSCF )三种类型， 其中负主要责任的是 S-CSCF, I-CSCF类型是可选 的。 业务层是由一系列应用服务器（ Application Server, AS )组成， 能提供 具体业务服务， AS可以是独立的实体， 也可以存在于 S-CSCF中。 控制层 S-CSCF根据用户的签约信息控制业务触发， 调用 AS上的业务， 实现业务 功能。 AS和 S-CSCF可以统称为服务设备（SE, Server Equipment )„ 会话 中的端到端设备称为用户设备 ( User Equipment , UE ), 负责与使用者的交 互。有的 UE具有多种接入网络的方式， 包括通过 3GPP的 PS域接入网络、 通过其他非 3GPP的数据域接入网络， 甚至可以通过 CS域接入网络等。 即 CS网络， PS网络（包括 LTE/SAE ) 均可作为 IMS网络的一种接入手段， 即用户可以通过 LTE/S AE或 CS , 建立 IMS会话， 由 IMS提供各类业务控 制， 由 LTE/SAE或 CS为用户提供网络接入。 UE通过 IMS建立各种会话 请求时， UE与 IMS 网络中的各个实体使用标准的会话发起协议（Session Initiation Protocol, SIP )通讯。
当 UE建立一个 IMS会话时， 根据不同的需要（如运营商策略、 流量 控制和统计、 切换优化等）， 网络可以决定将会话锚定在某个逻辑功能实体 上。
图 1是 UE通过 LTE/SAE接入网络建立会话时锚定所有会话的业务场 景。 用户在源无线接入覆盖区进行语音业务时， 直接接入 IMS, 与远端用 户建立 IMS会话， 且该会话的信令部分锚定在当前驻留网络的接入切换控 制功能实体（Access Transfer Control Function, ATCF )上， 媒体部分则锚 定在接入切换控制功能实体控制的接入网关（ Access Gateway, AGW )上。 由于无线频语干扰等限制 , UE无法同时接入 LTE/SAE和 2G/3G的 CS网 络， 所以当用户移出上述 LTE/SAE覆盖区域时， 为了保证语音业务的连续 性， 网络侧将用户的会话切换到 CS网络。 由于此类切换更新远端的过程较 长， 而 UE本地切换接入网的过程较短， 这两个过程并行发生， 较难同步， 所以此类切换用户的语音中断时间较长。 此类切换称为单信道模式的语音 呼叫连续性， 或单模的语音呼叫连续性（ Single Radio Voice Call Contiuity , SRVCC ); 如果由 ATCF/AGW作为锚定点控制发生切换， 可以缩短在切换 过程中由于远端更新过程过长而引起的语音中断， 提高用户体验。
为简化图示和描述， 将 ATCF和受 ATCF控制的 AGW合一描述。
如图 1 所示， UE和远端 （Remote End )建立了会话， 该会话锚定在 UE当前驻留网络的 ATCF (信令锚定）和 AGW (媒体锚定）上， AGW受 ATCF控制：
101、 UE负责与使用者的交互， 并能通过 PS/CS等不同接入方式建立 会话；
102、 ATCF负责锚定 UE会话的信令部分， 并控制 AGW锚定用户会 话的媒体部分；
ATCF 为逻辑功能实体， 实际物理位置可以位于 UE 通过拜访网络 LTE/SAE 进行 IMS 注册时在信令路径上的某一网元， 如 P-CSCF/IBCF ( Interconnection Border Control Function, 互通边界控制功能)等。
103、 AGW负责在 ATCF控制下， 锚定 UE会话的媒体部分；
AGW可以位于拜访地的 TrGW ( Transition Gateway, 过渡网关 ) , PDN GW或 P-GW ( Packet Data Network Gateway, 分组域网络网关）， CS域或 IMS域的 MGW ( Media Gateway, 媒体网关）等， 可以根据实际情况灵活 部署。
104、 IMS负责处理 UE通过各种接入网所建立的会话， 包括始呼会话 和终呼会话等， 并负责与远端建立会话；
图中的 IMS位于用户的归属地网络， 包含 CSCF和各种 AS等网元， 如提供业务一致性和连续性的业务一致性和连续性应用服务器 （ Service Consistency and Continuity Application Server, SCC AS );
105、 Remote End与 UE建立 IMS会话； 该 Remote End可能是 UE, 也 可能是提供服务的服务器等， 如流媒体服务器。
图 2是现有的 UE通过 LTE/SAE进行 IMS注册， 并建立语音会话时的 会话锚定流程图， ATCF/AGW在会话建立时锚定 UE的会话， 其具体描述 下：
步骤 201、 UE在当前的驻留网络发起 IMS注册请求，该请求消息到达
ATCF;
步骤 202、 ATCF将注册消息送至用户拜访地的 S-CSCF;
ATCF 在注册消息中携带为该用户分配的拜访地的单模切换号码 ( Visited Session Transfer Number - Single Radio , vSTN-SR );
如果用户是 SRVCC用户， vSTN-SR用于后继用户可能发生的 SRVCC 过程；
该步骤中的注册消息需要先到达用户归属地的 I-CSCF, 由 I-CSCF与 归属签约服务器（ Home Subscriber Server, HSS )交互以确定服务该用户的 S-CSCF, 然后由 I-CSCF将该消息路由至所述 S-CSCF处理。 为简化图示和 描述， 这里将 I-CSCF和 S-CSCF合一描述， 且省略了 HSS的相关流程； 步骤 203-204、 S-CSCF处理完注册请求后， 通过原路径向 UE回复注 册响应消息；
步骤 205、 S-CSCF处理完用户的注册消息后，根据初始过滤准则（ initial Filter Criteria, iFC ), 在需要时代替 UE向相应的应用服务器（Application Server, AS )进行第三方注册； 如果用户是 SRVCC用户 , S-CSCF需要代替 UE向 SCC AS进行第三 方注册， 并携带步骤 202中的 vSTN-SR;
vSTN-SR将通过 HSS 推进过程被下载给 LTE/SAE 网元， 并在触发 SRVCC过程时由 LTE/SAE网元传给 CS网元； 也可通过其他途径传给相应 的 LTE/SAE、 CS网元， 以实现 SRVCC;
步骤 206、 UE发起 IMS会话， 该 IMS会话的会话请求到达 ATCF, 其 中携带有 UE的会话媒体描述协议（ Session Description Protocol, SDP )信 息， 如 IP地址、 媒体流编码格式、 端口号等；
步骤 207、 ATCF锚定该用户的会话， 将媒体部分锚定在其所控制的一 个 AGW上。 ATCF向 S-CSCF发送会话请求， 其中携带有 AGW的 SDP信 息；
如果 UE是 SRVCC的签约用户， 则执行步骤 208al-209a2; 否则， 执 行步骤 208b-209b;
步骤 208al、 根据 iFC的触发， S-CSCF将收到的会话请求路由到 SCC AS处理；
步骤 208a2、 SCC AS将收到的会话请求发送至远端 UE;
步骤 209al、 远端 UE向 SCC AS回复会话响应， 其中携带有远端 UE 的 SDP信息；
步骤 209a2、 SCC AS向 S-CSCF发送会话响应；
步骤 208b、 S-CSCF将会话请求发送给远端 UE;
该步骤中， 由于用户不是 SRVCC用户， 所以呼叫不会触发给 SCC AS 处理；根据 iFC,会话请求有可能会先触发给其他 AS处理，随后返回 S-CSCF 并被发向远端 UE;
步骤 209b、远端 UE向 S-CSCF回复会话响应， 其中携带有远端 UE的 SDP信息； 步骤 210、 S-CSCF向 ATCF回复会话响应，其中携带有远端 SDP信息； 步骤 211、 ATCF向 UE回复会话响应，其中携带有 AGW的 SDP信息； 上述步骤完成后， UE与远端 UE之间的会话建立完成， 且会话锚定在 ATCF/AGW上。如图所示 ,此时媒体分为两段，分别为： UE到 AGW—段， AGW到远端一段，这样用户由于某种业务需要，可以提供更好的用户体验， 比如：用户如果是 SRVCC用户，则在后继发生 SRVCC切换时，可以由 ATCF 控制， 以减少切换中的语音中断时间， 提供较好的用户体验。
但上述呼叫建立过程中 ATCF/AGW锚定会话的方法存在如下弊端： ATCF无法区分用户是否需要锚定会话， 所以对于所有经过 ATCF的会话， 都需要将其媒体面锚定在 AGW上。 比如对于非 SRVCC用户， ATCF也会 对其的会话进行锚定。 这样会造成网络资源（如 AGW资源）的浪费； 而且 由于 UE到远端 UE的媒体锚定在 AGW上， 使得通信过程中增加了一个锚 定点， 很有可能对用户的业务质量和用户体验造成不利影响。 发明内容
有鉴于此， 本发明的主要目的在于提供一种实现会话锚定的方法和系 统， 以保证只对需要锚定的会话提供锚定， 尽量减少网络资源的浪费。
为达到上述目的， 本发明的技术方案是这样实现的：
一种实现会话锚定的方法， 包括：
根据用户信息初步判定是否需要锚定会话， 并在初步判定需要锚定时 发出锚定指示； 根据锚定指示最终决策是否锚定会话。
其中， 所述用户信息为用户签约信息， 所述初步判定的过程包括： 根据用户签约信息判断用户是否为单信道模式的语音呼叫连续性 SRVCC用户， 并在判断结果为是时初步确定需要锚定会话。
其中， 所述用户信息为用户当前使用终端的能力信息， 所述初步判定 的过程包括： 根据用户终端能力信息判断用户当前使用的终端是否为 SRVCC终端， 并在判断结果为是时初步确定需要锚定会话。
其中， 所述最终决策的过程包括：
在收到锚定指示时直接确定需要锚定会话。
其中， 所述最终决策的过程包括：
在收到锚定指示后根据包括本地网络策略在内的因素最终确定是否锚 定会话。
一种实现会话锚定的系统， 包括锚定初步判定单元、 锚定决策单元； 其中，
所述锚定初步判定单元， 用于根据用户信息初步判定是否需要锚定会 话， 并在初步判定需要锚定时向所述锚定决策单元发出锚定指示；
所述锚定决策单元， 用于根据收到的锚定指示最终决策是否锚定会话。 其中， 所述用户信息为用户签约信息， 所述锚定初步判定单元进行所 述初步判定时用于：
根据用户签约信息判断用户是否为 SRVCC用户，并在判断结果为是时 初步确定需要锚定会话。
其中， 所述用户信息为用户终端能力信息， 用于表明用户当前使用的 终端是否具有 SRVCC能力；
所述锚定初步判定单元进行所述初步判定时， 还用于：
针对 SRVCC用户，根据用户终端能力信息判断用户当前使用的终端是 否具有 SRVCC能力， 并在判断结果为是时初步确定需要锚定会话。
其中， 所述锚定决策单元进行所述最终决策时用于：
在收到锚定指示时直接确定需要锚定会话。
其中， 所述锚定决策单元进行所述最终决策时用于：
在收到锚定指示后根据包括本地网络策略在内的因素最终确定是否锚 定会话。
本发明实现会话锚定的方法和系统， 均可保证只对需要锚定的会话提 供锚定， 因而能够尽量减少网络资源的浪费。 并且， 由于在不需要锚定时 不会进行锚定， 因此不存在不必要的锚定点， 所以不会因不必要的锚定点 对用户的业务质量和用户体验造成不利影响。 附图说明
图 1为现有技术 LTE/SAE中呼叫锚定的架构示意图；
图 2为现有技术的呼叫锚定的信令流程示意图；
图 3为本发明实施例一的实现会话锚定的流程图；
图 4为本发明实施例二的实现会话锚定的流程图；
图 5为本发明实施例三的实现会话锚定的流程图；
图 6为本发明实现会话锚定的流程简图；
图 7为本发明实施例的实现会话锚定的系统图。 具体实施方式
总体而言， 在会话建立过程中， 可以由 IMS网络中的网元向 ATCF提 供用于表示是否需要锚定的锚定提示等信息， 并最终由 ATCF决策是否需 要锚定会话， 以避免造成网络资源的浪费。
以下通过附图及具体实施例对以上实现有选择锚定会话的方法进行具 体说明：
参见图 3 , 图 3为本发明实施例一的实现会话锚定的流程图， 该流程包 括以下步骤：
步骤 301、 UE在 LTE/SAE发起 IMS注册请求，该请求消息到达 ATCF; 步骤 302、 ATCF将注册请求消息送至用户拜访地的 S-CSCF;
ATCF在注册请求消息中携带为该用户分配的 vSTN-SR; 步骤 303至步骤 304、 S-CSCF处理完注册请求后， 通过原路径向 UE 回复注册响应消息；
步骤 305、 S-CSCF处理完用户的注册请求消息后， 根据 iFC, 在需要 时代替 UE向相应的 AS进行第三方注册；
步骤 306、 UE发起 IMS会话建立请求， 其中携带有 UE的 SDP信息； 步骤 307、 收到步骤 306中的会话建立请求后， ATCF将其转发给 UE 归属的 IMS网络的 S-CSCF;
ATCF转发的会话建立请求中携带有 UE的 SDP信息， 同时， ATCF在 会话建立请求中插入用于锚定用户会话的媒体的指示， 表明没有为该呼叫 分配 AGW;
步骤 308、 S-CSCF根据 iFC, 将呼叫触发到 SCC AS处理；
步骤 309、 由于在步骤 305中收到了 vSTN-SR, 所以 SCC AS明确拜访 地部署了用于锚定会话的 ATCF/AGW。 SCC AS根据各种信息， 比如、 用 户是否为 SRVCC用户（可以应用用户签约信息予以判定）、 UE能力信息（该 信息用于表明用户当前是否使用具有 SRVCC 能力的终端）、 主叫用户 UE 是否漫游、 远端 UE是否漫游、运营商配置的策略或其他因素， 判断是否在 拜访地需要锚定该会话的媒体。 若判断需要锚定， 则 SCC AS以向 S-CSCF 发送拒绝消息等形式表明拒绝所述呼叫建立请求， 指示需要锚定该会话的 媒体；
通常， 在拒绝消息中也可能携带 SCC AS上所具有的判定信息， 如 UE 能力信息， 用户是否漫游等信息， 以提供给 ATCF做锚定判定；
SCC AS根据多种信息判断是否向 ATCF发送拒绝消息， 以及携带锚定 指示。其中，主要的判断依据为用户是否为 SRVCC用户：如用户不是 SRVCC 用户，则不需要锚定会话，进而不向 ATCF发送拒绝消息；如用户是 SRVCC 用户， 则可能综合考虑其他因素， 最终决定向 ATCF发送拒绝消息， 并携 带锚定指示；
步骤 310、 S-CSCF向 ATCF发送拒绝消息；
步骤 311、 ATCF收到拒绝消息后， 根据消息提供的锚定指示等信息， 以及本地网络策略、 UE能力信息等因素， 最终决策是否需要锚定该会话的 媒体。 ATCF随后向 UE归属 IMS网络发起新的会话建立请求；
如果 ATCF最终决策需要分配 AGW以锚定 UE会话的媒体，则在本步 骤的会话建立请求中携带 AGW的 SDP信息； 否则， 仍然携带 UE的 SDP 信息；
当然， 如果有其他因素， 比如本地策略是否允许锚定等， 或者 ATCF 有 UE的能力信息 （用于表明 UE是否为 SRVCC UE ), 则可以综合所有因 素以判断是否需要锚定会话， 最终决策在步骤 312 中的建立请求中携带 AGW或 UE的 SDP信息；
步骤 312、 S-CSCF向 SCC AS发送会话建立请求；
步骤 313、 SCC AS通过 S-CSCF, 向远端 UE发送会话建立请求； 步骤 314至步骤 316、 远端 UE通过 S-CSCF/SCC AS向 ATCF回复会 话建立响应， 其中携带有远端 UE的 SDP应答；
步骤 317、 ATCF向 UE回复会话建立响应，其中携带有 SDP应答信息； 在步骤 311中，如果 ATCF为会话分配了 AGW以锚定媒体， 即携带了 AGW的 SDP信息， 则步骤 317的消息中携带 AGW的 SDP给 UE; 如果 ATCF没有为会话分配 AGW以锚定媒体， 即步骤 311中仍然携带了 UE的 SDP信息， 则 ATCF将远端 UE的 SDP信息发送给 UE。
参见图 4, 图 4为本发明实施例二的实现会话锚定的流程图， 该流程包 括以下步骤：
步骤 401、 UE在 LTE/SAE发起 IMS注册请求，该请求消息到达 ATCF; 步骤 402、 ATCF将注册请求消息送至用户拜访地的 S-CSCF; ATCF在注册请求消息中携带为该用户分配的 vSTN-SR; 步骤 403至步骤 404、 S-CSCF处理完注册请求后， 通过原路径向 UE 回复注册响应消息；
步骤 405、 S-CSCF处理完用户的注册消息后， 根据 iFC, 在需要时代 替 UE向相应的 AS进行第三方注册；
步骤 406、 UE发起 IMS会话建立请求， 其中携带有 UE的 SDP信息； 步骤 407、 收到会话建立请求后， ATCF将其转发给 UE归属的 IMS网 络的 S-CSCF;
ATCF发送的会话建立请求中携带有 UE的 SDP信息， 同时， ATCF在 会话建立请求中插入用于锚定用户会话的媒体的指示， 表明没有为该呼叫 分配 AGW;
步骤 408、 S-CSCF根据 iFC, 将呼叫触发到 SCC AS处理；
步骤 409、 由于在步骤 405中收到了 vSTN-SR, 所以 SCC AS明确拜访 地部署了用于锚定会话的 ATCF/AGW。 SCC AS根据各种信息， 比如用户 是否为 SRVCC用户 （可以根据用户签约信息予以判定）、 UE能力信息、 用 户是否漫游、 运营商配置的策略或其他因素， 判断是否在拜访地需要锚定 该会话的媒体。 若判断需要锚定， 则 SCC AS向 S-CSCF发送锚定指示， 指 示需要锚定该会话的媒体；
所述锚定指示可以通过针对会话建立的临时响应携带；
步骤 409a、 SCC AS通过 S-CSCF向远端 UE发送会话建立请求， 携带 UE的 SDP信息；
步骤 409b、远端 UE通过 S-CSCF向 SCC AS回复会话建立响应， 其中 携带有远端 UE的 SDP应答信息；
如果 SCC AS触发步骤 409 , 则步骤 409与步骤 409a并行发生； 步骤 410、 S-CSCF向 ATCF发送锚定指示； 步骤 411、 ATCF收到锚定指示后，根据该锚定指示以及本地网络策略、 UE能力信息等因素， 最终决策是否需要锚定该会话的媒体。 ATCF随后向 UE归属 IMS网络发起会话更新请求；
如果 ATCF最终决策需要分配 AGW以锚定 UE会话的媒体，则在步骤 411中携带 AGW的 SDP信息； 否则， 仍然携带 UE的 SDP信息；
步骤 412、 S-CSCF向 SCC AS发送会话更新请求；
步骤 413、如果步骤 412中的 SDP信息与步骤 408中的 SDP信息不同， 则 SCC AS通过 S-CSCF向远端 UE发送会话更新请求； 否则， SCC AS不 执行步骤 413 , 进而也不再有步骤 414;
步骤 414、 远端 UE通过 S-CSCF向 SCC AS回复会话更新响应， 其中 携带有远端 UE的新 SDP信息；
步骤 415至步骤 416、 SCC AS通过 S-CSCF向 ATCF回复会话建立响 应， 其中携带有步骤 414中收到的 SDP应答信息； 如果没有执行步骤 413 至步骤 414, 则携带步骤 409b中的 SDP应答信息；
步骤 417、 ATCF向 UE回复会话建立响应；
在步骤 411中，如果 ATCF为会话分配了 AGW以锚定媒体， 即携带了 AGW的 SDP信息， 则步骤 417的消息中携带 AGW的 SDP给 UE; 如果 ATCF没有为会话分配 AGW以锚定媒体， 即步骤 411中仍然携带了 UE的 SDP信息， 则 ATCF将步骤 416中的远端 UE的 SDP信息发送给 UE。
参见图 5 , 图 5为本发明实施例三的实现会话锚定的流程图， 该流程包 括以下步骤：
步骤 501至步骤 512与图 4中的步骤 401至步骤 412—致， 唯一区别 在于图 5中不包含步骤 409a和步骤 409b;
步骤 513、 SCC AS通过 S-CSCF向远端 UE发送会话建立请求， 其中 携带有步骤 512中收到的 SDP信息； 步骤 514、 远端 UE通过 S-CSCF向 SCC AS回复会话建立响应， 其中 携带有远端 UE的新 SDP信息；
步骤 515至步骤 516、 SCC AS通过 S-CSCF向 ATCF回复会话建立响 应， 其中携带有步骤 514中收到的 SDP应答信息；
步骤 517、 ATCF向 UE回复会话建立响应；
在步骤 511中，如果 ATCF为会话分配了 AGW以锚定媒体， 即携带了 AGW的 SDP信息， 则步骤 517的消息中携带 AGW的 SDP给 UE; 如果 ATCF没有为会话分配 AGW以锚定媒体， 即步骤 511中仍然携带了 UE的 SDP信息， 则 ATCF将步骤 516中的远端 UE的 SDP信息发送给 UE。
由以上所述各流程可见， 最初的锚定判断有可能触发后续的锚定决策， 并且在锚定决策完成之后， 如果最终确定需要锚定会话， 则触发后续的锚 定会话操作， 如： 图 3中的从步骤 311开始的操作， 图 4中的从步骤 411 开始的操作， 以及图 5中的从步骤 511开始的操作。 基于此， 本发明实现 会话锚定的操作思路可以表示如图 6所示。 参见图 6, 图 6为本发明实现会 话锚定的流程简图， 该流程包括以下步骤：
步骤 610: 根据用户签约信息等用户信息初步判定是否需要锚定会话， 并在初步判定需要锚定时发出锚定指示。 如： 根据用户的签约信息判定用 户为 SRVCC用户， 或根据 UE能力信息确定 UE有 SRVCC能力等， 则确 定需要锚定会话。
步骤 620: 根据锚定指示最终决策是否锚定会话。
结合前述的各流程， 需要说明的是， 在操作逻辑比较简单时， 可以在 收到锚定指示时就直接确定最终决策： 需要锚定会话。 在操作逻辑相对复 杂时， 则可以在收到锚定指示后进一步根据本地网络策略等因素、 UE是否 有 SRVCC能力等最终确定是否锚定会话。
为了保证上述操作能够顺利进行， 可以设置如图 7所示的系统。 参见 图 7, 图 7为本发明实施例的实现会话锚定的系统图， 该系统包括相连的锚 定初步判定单元、锚定决策单元。其中，锚定初步判定单元可以设置于 SCC AS等能够获取用户签约信息并进行逻辑判断的功能实体中， 锚定决策单元 则可以设置于 ATCF等能够对 UE进行接入控制的功能实体中。
具体应用时， 锚定初步判定单元可以根据用户签约信息等用户信息初 步判定是否需要锚定会话， 并在初步判定需要锚定时向锚定决策单元发出 锚定指示， 并可能携带一些影响决策的因素 （如 UE能力信息等）， 由锚定 决策单元根据收到的锚定指示等内容最终决策是否锚定会话。
并且， 如果最终确定需要锚定会话， 锚定决策单元进一步可以触发后 续的锚定会话操作。
图 7所示各单元所能实现的具体操作已在前述各流程中详细描述， 在 此不再赘述。
综上所述可见， 无论是方法还是系统， 本发明实现会话锚定的技术， 均可保证只对需要锚定的会话提供锚定， 因而能够尽量减少网络资源的浪 费。 并且， 由于在不需要锚定时不会进行锚定， 因此不存在不必要的锚定 点， 所以不会因不必要的锚定点对用户的业务质量和用户体验造成不利影 响。
以上所述， 仅为本发明的较佳实施例而已， 并非用于限定本发明的保 护范围， 凡在本发明的精神和原则之内所作的任何修改、 等同替换和改进 等， 均应包含在本发明的保护范围之内。

Claims

权利要求书
1、 一种实现会话锚定的方法， 包括：
根据用户信息初步判定是否需要锚定会话， 并在初步判定需要锚定时 发出锚定指示； 根据锚定指示最终决策是否锚定会话。
2、根据权利要求 1所述的方法，其中， 所述用户信息为用户签约信息， 所述初步判定的过程包括：
根据用户签约信息判断用户是否为单信道模式的语音呼叫连续性 SRVCC用户， 并在判断结果为是时初步确定需要锚定会话。
3、 根据权利要求 1所述的方法， 其中， 所述用户信息为用户当前使用 终端的能力信息， 所述初步判定的过程包括：
根据用户终端能力信息判断用户当前使用的终端是否为 SRVCC终端， 并在判断结果为是时初步确定需要锚定会话。
4、 根据权利要求 1至 3任一项所述的方法， 其中， 所述最终决策的过 程包括：
在收到锚定指示时直接确定需要锚定会话。
5、 根据权利要求 1至 3任一项所述的方法， 其中， 所述最终决策的过 程包括：
在收到锚定指示后根据包括本地网络策略在内的因素最终确定是否锚 定会话。
6、一种实现会话锚定的系统， 包括锚定初步判定单元、锚定决策单元； 其中，
所述锚定初步判定单元， 用于根据用户信息初步判定是否需要锚定会 话， 并在初步判定需要锚定时向所述锚定决策单元发出锚定指示；
所述锚定决策单元， 用于根据收到的锚定指示最终决策是否锚定会话。
7、根据权利要求 6所述的系统，其中， 所述用户信息为用户签约信息， 所述锚定初步判定单元进行所述初步判定时用于：
根据用户签约信息判断用户是否为 SRVCC用户，并在判断结果为是时 初步确定需要锚定会话。
8、 根据权利要求 7所述的系统， 其中， 所述用户信息为用户终端能力 信息， 用于表明用户当前使用的终端是否具有 SRVCC能力；
所述锚定初步判定单元进行所述初步判定时， 还用于：
针对 SRVCC用户，根据用户终端能力信息判断用户当前使用的终端是 否具有 SRVCC能力， 并在判断结果为是时初步确定需要锚定会话。
9、 根据权利要求 6至 8任一项所述的系统， 其中， 所述锚定决策单元 进行所述最终决策时用于：
在收到锚定指示时直接确定需要锚定会话。
10、 根据权利要求 6至 8任一项所述的系统， 其中， 所述锚定决策单 元进行所述最终决策时用于：
在收到锚定指示后根据包括本地网络策略在内的因素最终确定是否锚 定会话。
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