关于移动性管理(Mobility Management)的常见问答

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1 What does the Mobility Management (MM) layer do?
  The main function of the Mobility Management sublayer is to support the mobility of user terminals, such as informing the network of its present location and providing user identity confidentiality. A further function of the MM sublayer is to provide connection management services to the different entities of the upper Connection Management (CM) sublayer.
  MM子层的主要功能是来支持用户终端的移动性，例如告知网络侧关于用户的位置并且保证用户身份的私密性。另外MM子层还有一个功能是为不同的上层连接管理（CM)子层实体提供连接管理。
2 Sometimes MM is referred to as GMM; are they the same?
  MM sub-layer consists of two types of procedures; MM procedures for non-GPRS services and GMM procedures for GPRS services. The G in GMM stands for GPRS.
  MM子层由两个流程来组成; 针对非GPRS业务的MM流程（即CS的语音业务）以及针对GPRS业务的GMM流程。G在GMM中代表GPRS。
3 What are MM Procedures?
  Depending on how they can be initiated, three types of MM procedures can be distinguished:
1）MM common procedures: A MM common procedure can always be initiated whilst a RR connection exists. The procedures belonging to this type are:
Initiated by the network:
- TMSI reallocation procedure;
- authentication procedure;
- identification procedure;
- MM information procedure;
- abort procedure.
  However, abort procedure is used only if an MM connection is being established or has already been established i.e. not during MM specific procedures or during IMSI detach procedure, see subclause 4.3.5.
Initiated by the mobile station:
- IMSI detach procedure (with the exceptions specified in subclause 4.3.4).
2） MM specific procedures: A MM specific procedure can only be initiated if no other MM specific procedure is running or no MM connection exists. The procedures belonging to this type are:
- normal location updating procedure;
- periodic updating procedure;
- IMSI attach procedure.
3） MM connection management procedures: These procedures are used to establish, maintain and release a MM connection between the mobile station and the network, over which an entity of the upper CM layer can exchange information with its peer. A MM connection establishment can only be performed if no MM specific procedure is running. More than one MM connection may be active at the same time.
   取决于这些流程是怎样发起的，分成3种类型的MM流程：
1）MM公共流程; 一个MM的公共流程可以在一个RR连接存在的时候发起。属于这种类型的流程包括：
由网络侧发起的：
- TMSI重分配流程；
- 鉴权流程；
- 身份获取流程；
- MM信息流程；
- 中止流程。
  然而，中止流程仅用于这个MM连接将要或已经建立，也就是不在某些特定的MM流程中出现，例如IMSI去附着流程。参考章节4.3.5.（规范的章节）。
由MS发起的：
- IMSI去附着流程（有一个例外情景在章节4.3.4描述）
2）MM特定的流程：一个MM特定流程仅当没有其他的MM特定流程在运行时或者没有MM连接存在时才能发起。属于这种类型的流程包括：
- 正常的位置更新流程；
- 周期性更新流程；
- IMSI附着流程。
3）MM连接管理流程; 这些流程用于建立，维持以及释放一个在MS和网络侧之间的MM连接，这些连接为上层CM层实体交换信息提供了下层的通道。一个MM连接建立只能在没有MM特定的流程运行的时候执行。可以有多个MM连接在同一时刻变成active。
4 What are GMM procedures?
  Depending on how they can be initiated, two types of GMM procedures can be distinguished:
1) GMM common procedures: In Iu mode, a GMM common procedure can always be initiated whilst a PS signalling connection exists.
  The procedures belonging to this type are:
  Initiated by the network when a GMM context has been established:
- P-TMSI (re-) allocation;
- GPRS authentication and ciphering;
- GPRS identification;
- GPRS information.
2) GMM specific procedures:
Initiated by the network and used to detach the IMSI in the network for GPRS services and/or non-GPRS services and to release a GMM context:
- GPRS detach.
Initiated by the MS and used to attach or detach the IMSI in the network for GPRS services and/or non-GPRS services and to establish or release a GMM context:
- GPRS attach and combined GPRS attach;
- GPRS detach and combined GPRS detach.
Initiated by the MS when a GMM context has been established:
- normal routing area updating and combined routing area updating;
- periodic routing area updating.
In UMTS, initiated by the MS and used to establish a secure connection to the network and/or to request the resource reservation for sending data:
- Service Request.
   取决于这些流程是怎样发起的，分成2种类型的GMM流程：
1) GMM公共流程; 在Iu模式，一个GMM的公共流程可以在当一个PS信令连接（即Iu connection）存在的时候发起。
  属于这种类型的流程包括：
当一个GMM上下文要建立时由网络侧发起：
- P-TMSI（重分配）分配：
- GPRS鉴权和加密;
- GPRS身份获取；
- GPRS信息。
2）GMM特定流程;
由网络侧发起，用于将和GPRS业务及/或非GPRS业务的IMSI去附着，并释放一个GMM上下文;
- GPRS去附着。
由MS发起用于GPRS业务及/或非GPRS业务的IMSI去附着，用于建立或释放一个GMM上下文;
- GPRS附着和联合GPRS附着;
- GPRS去附着和联合去GPRS去附着。
由MS在建立了一个GMM上下文的时候发起:
- 正常的RAU以及联合的RAU;
- 周期性RAU。
在UMTS中，由MS发起的用于建立到网络侧的一条安全连接，并且/或请求为发送数据进行资源预留;
- 服务请求流程.
5 Do i need to have RR (RRC) connection to perform Mobility Management functions?
  Yes. If you do not have a RR connection than you need to establish one to perform MM functions. You cannot perform any MM/GMM procedures without RRC conection.
   是的。执行MM功能之前一定要先建立一个RRC连接。   
6 How is MM signalling done?
  After RRC connection has been setup, the direct transfer messages are used to perform MM signalling.
   在RRC连接建立后，直传消息将用于执行MM信令。
REFERENCES:
[1] 3GPP TS 24.008 - Mobile radio interface Layer 3 specification; Core network protocols; Stage 3
[2] 3GPP TS 24.007 - Mobile radio interface signalling layer 3; General aspects
[3] 3GPP TS 44.018 - Mobile radio interface layer 3 specification, Radio Resource Control (RRC) protocol
[4] 3GPP TS 23.060 - General Packet Radio Service (GPRS); Service description; Stage 2
[5] 3GPP TS 23.012 - Location Management Procedures
[6] 3GPP TS 29.002 - Mobile Application Part (MAP) specification
[7] 3GPP TS 25.331 - RRC Protocol Specification
[8] 3GPP TS 25.304 - User Equipment (UE) procedures in idle mode and procedures for cell reselection in connected mode
[9] 3GPP TS 23.122 - NAS Functions related to Mobile Station (MS) in idle mode

回复Bestflora的帖子：
该流程可选。如果实现了该流程，则RR连接存在的任何时候，都应能处理该流程。网络侧向MS发MM Information消息开始该流程，MS在收到消息后，使用该消息中所带的参数更新存储在MS中的相应信息。如果MS不支持该消息，则可以发MM STATUS消息(Cause 97)作为返回。
    可以参考http://wenku.baidu.com/view/9c44d737a32d7375a4178063.html 的第13页。这个文档叫GSM Um接口第三层MM子层。

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