Mobility Management Services
The services offered by mobility management are described in the following:

Registration
After power-on or SIM insertion the mobile station searches for a cell and tries to register on it. Selecting
a network is the sense of the registration procedure.

Normal Location Updating
If the mobile station is not registered by the network or changes a location area a normal location updating
is processed. That means the registration by the network is updated.

Periodic Location Updating
If the network uses periodic location updating this procedure is used by the mobile station to update its
registration by the network in periodic times.

IMSI Attach
If indicated by the network the mobile station updates its registration after initial cell selection althought
the SIM card shows the updated state.

IMSI Detach
If indicated by the network the mobile station de-registers itself during SIM removing or power-off.

TMSI Reallocation
The TMSI Reallocation procedure is used by the network to assign a new or changed temporary subscriber
identity to the mobile station.

Authentication
The authentication procedure is used to calculate and compare the authentication parameter.
Identification
The base station uses the identication procedure to request the various identifications from a mobile
station.

MM-Connection Management
MM handles the various connections from call control, supplementary services and short message
services.

Net Request
The net request procedure requests all available networks and presents it to the man machine interface.

如图，MM各个状态的转换和条件。

Overview

This section offers a brief description of the different layers which constitute the mobile station Protocol Stack. It is also intended to offer an overview of the intersystem interface. The Protocol Stacks are used to define the functionality of the GSM protocols for interfaces. The GSM specifications are normative when used to describe the functionality of interfaces, but the stacks and the subdivision of protocol layers do not imply or restrict any implementation.

1 PL - Physical Layer

The base of the Protocol Stack rests on the physical layer.

2 DL - Data Link

The Data Link Layer (DL) is used to handle an acknowlowdged connection between mobile and base station. The LAPDm protocol is used.

3 RR - Radio Resource

Radio Resource (RR) manages the resources of the air-interface. That means configuration of physical layer, cell selection and cell reselection, data transfer, RR-Connection handling.

4 MM - Mobility Management

Mobility Management (MM) handles registration aspects for the mobile station. It detects changes of location areas and updates a mobile station in the new location area.

5 CC - Call Control

Call Control (CC) provides the call functionality. This includes call establishment, call maintenance

procedures like Hold, Retrieve or Modify, and call disconnection.

6 SS - Supplementary Services

Supplementary Services (SS) handles all call independent supplementary services like call forwarding or call barring.

7 SMS - Short Message Services

Short Message Services (SMS) is used for sending and receiving point-to-point short messages. Additionally the reception of cell broadcast short messages is included. Call Control (CC), Supplementary Services (SS) and Short Message Services (SMS) together are referred to as Connection Management (CM) sometimes.

8 MMI - Man Machine Interface

The man machine interface (MMI) is the interface to the user. Normally it is connected with a keypad as input device and a display as output device. In G23, there is a AT Command Interpreter (ACI), therefore, sometimes the MMI is also referred to as ACI in the present document if “the layer above layer 3″ is to be identified.

Between the several entities data interfaces are defined. These data interfaces are called Service

Access Points (SAPs), indicating that an upper layer uses the services of a lower layer.

The GSM specification do not set out any implementation of the Protocol Stack. The following diagrams show the implementation described in all these documents for the mobile station. All entities Technical Document GSM Protocol Stack Message Sequence Charts MM (6147.203.97.102), v0.3 Draft

except the Man Machine Interface and Physical Layer are implemented as part of the Protocol Stack - with ACI seen as an integral part of the stack in almost all cases.

For GPRS, there are more entities.

9 GRR (RLC/MAC) – Radio Link Control/Medium Access Control

This layer contains two functions: The Radio Link Control function provides a radio-solution-dependent reliable link. The Medium Access Control function controls the access signalling (request and grant) procedures for the radio channel, and the mapping of LLC frames onto the GSM physical channel.

10 LLC – Logical Link Control

The LLC entity provides multiple highly reliable logical links for asynchronous data transfer between the MS and the network. It supports variable-length information frames, acknowledged and unacknowledged data transfer, flow and sequence control,error detection and recovery, notification of unrecoverable errors, user identity confidentiality, and ciphering of user and signaling data.

11 GMM – GPRS Mobility Management

The GMM entity provides procedures for the mobility of the MS, such as informing the network of its present location, and user identity confidentiality. It manages the GMM context (attach, detach, routing area updating), supports security functions such as authentication of user and MS, controls ciphering of data, and initiates the response to paging messages.

12 SM – Session Management

The main function of the session management (SM) is to support PDP context handling of the user terminal. Session Management activates, modifies and deletes the contexts for packet data protocols (PDP). Session Management services are provided at the SMREG-SAP and the SNSM-SAP for anonymous and non-anonymous access. The non-anonymous and anonymous access procedures for PDP context activation and PDP context deactivation are available at the SMREG-SAP.In addition there exists a PDP context modification for non-anonymous PDP contexts.

13 SNDCP - Subnetwork Dependant Convergence Protocol

SNDCP carries out all functions related to transfer of Network layer Protocol Data Units (N-PDUs) over GPRS in a transparent way. SNDCP helps to improve channel efficiency by means of compression techniques. The set of protocol entities above SNDCP consists of commonly used network protocols. They all use the same SNDCP entity, which then performs multiplexing of data coming from different sources to be sent using the service provided by the LLC layer.

14 GACI – GPRS Application Control Interface

The GACI is the GPRS extension of the ACI. It is specified in GSM 07.07 and 07.60. It is responsible for processing of the GPRS related AT Commands to setup, activate and deactivate the PDP context parameter. It also provides functionality for the interworking between GMM/SM/SNDCP and a packet oriented protocol like PPP.

15 GSMS - GPRS Short Message Service

Like GACI, GSMS, the GPRS Short Message Service, is also not a new entity of its own, but it is the GSM SMS entity enhanced by GPRS functionality.

（1）当内核完成它自己内部由一些目标依赖部分组成的启动程序后，它将调用Application_Initialize()函数，这是实体进入内核所有应用程序的入口点。

（2）调用在Application_Initialize()函数中StartFrame（）函数。这是实体对于框架来说的主要的进入点。StartFrame（）主要负责内存池的创建，任务中实体任务的创建，启动作为当前应用程序一部分的任务。

（3）用于进行通信的分区内存池通过os_CreateParti tionPool()的调用而被创建。不同分区的大小和数目用户可以通过修改配置文件xxxconst.h来进行控制。

（4）如同任务的堆栈的内存分配一样，队列内存的分配是通过os_CreateMemoryPool()而得到的，它的大小也可以通过调整xxxconst.h而进行改变。

（5）在xxxcomp.c中有一张包含了所有在应用程序中的实体的pei_create（）函数地址的表。实体可能以一个单独的任务运行也可能是共享一个任务。框架调用每一个pei_create函数并根据该函数的参数而创建一个实体。

（6）调用os_CreateTask()而创建一个任务。

（7）当所有任务都被创建后，框架像创建他们一样也使用相同的启动命令来启动他们。在进一步的初始化（如L1层和他的驱动）后，Application_Initialize()将会返回，内核中的调度将会被激活。

（8）任务根据他们的优先级不同而依次被调度。对于所有的任务来说，这里只有一个任务实体的函数。每个任务它都只被调用一次。每个任务都有它自己的堆栈空间和处理由所有框架函数通过pf_TaskEntry()发出的请求。

（9）在任务中每个实体函数消息队列通过os_CreateQueue()的调用而被创建。队列中实体的数量是通过pei_create()中输出的结构体而得知。

（10）pei_init()被调用。它的函数地址也是通过pei_create()中输出的结构体而得知。

（11）在pei_init()中当前被调度的实体同其他实体进行通信的通信通道被打开。这是通过调用vsi_c_open()来完成的。打开一个通信通道意味着向框架请求得到队列中的那些实体的句柄。如果一个实体的句柄因为相应的任务没有被调度而不能被请求，这时pei_init()将会返回一个错误信息，当前活动的任务将会被阻塞100ms以使内核能够调度比当前任务优先权低的任务。然后pei_init()将再次被调用。当所有被请求的句柄都被得到后，一个内部的数据库将通过pei_init()而被初始化。.

（12）如果与一个任务进行通信的所有的任务并没有都被调度，那么该任务可能被阻塞。

（13）如果一个任务在一个活动的主体中运行，pei_run将被调用。实体的主要循环也包含在pei_run()中。

（14）对于运行在被动活动主体中的任务其主要的循环已经进入了。任务将会进入os_ReceiveFromQueue()同时被阻塞直到它的消息队列接收到一个消息为止。