8.1 Radio Resource Functionality(A/Gb Mode)

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8.1 Radio Resource Functionality (A/Gb mode)
8.1.1 Cell Selection and Reselection
  An MS (in any mode of operation - A, B, or C) cannot camp on more than one cell. If the MS is in idle mode, see TS 23.122 [7b], it shall use cell selection and reselection procedures as described in TS 43.064 [11] and specified in TS 23.122 [7b] and TS 45.008 [16b].
一个MS（任意模式的，A/B/C类都可以）同一时刻，只能访问一个小区而不能同时驻留在多个小区。如果MS在idle模式，参考TS23.122，它将使用在TS43.064以及在TS23.122和TS45.008中阐明的小区选择和重选流程来选择小区。
8.1.2 Discontinuous Reception(不连续接收)
  In A/Gb mode an MS may use discontinuous reception (DRX) or not. If using DRX, the MS shall also be able to specify other DRX parameters that indicate the delay for the network to send a page request or a channel assignment to the MS (see TS 43.064 [11]).
  The DRX parameters shall be indicated by the MS in the attach procedure. The SGSN shall then send these parameters in each page request to the BSS that uses this information and the IMSI to calculate the correct paging group.
  在A/Gb模式，一个MS可以使用或不使用不连续接收(DRX).如果使用了DRX，MS应能指明一些其他的DRX参数，来指示网络侧发送寻呼请求或信道分配给MS的延迟。（参考TS43.064)。
  DRX参数应由MS在附着流程中指明。SGSN应将这些信息放到每个寻呼请求中发给BSS，并使用这些信息和IMSI来计算正确的寻呼组。
  DRX usage is independent of the MM states IDLE, STANDBY and READY. When a GPRS MS in READY state uses DRX, DRX has to be considered when assigning a packet data channel for downlink transfer. The SGSN shall therefore indicate the DRX parameters for the MS in all packet transmission requests to the BSS.
In A/Gb mode an MS shall not apply DRX in READY state during the GPRS attach and routeing area update procedures.
  DRX的使用和MS的状态是IDLE、STANDBY还是READY是没有关系的。当一个READY状态的MS使用了DRX，DRX将在为下行数据传递分配数据包信道的时候被考虑进去。SGSN应为这个MS的所有包传输请求，来将这个DRX参数发送给BSS。
  At inter SGSN change to an SGSN operating in A/Gb mode, the DRX parameters are sent from the old SGSN to the new SGSN as part of the MM context information. Hence, unless the DRX parameters have been altered, the UE should not include the DRX parameters in the Routing Area Update message sent to an A/Gb mode SGSN.
  If the UE wishes to alter its GERAN or UTRAN/E-UTRAN DRX Parameters while in A/Gb mode, then it shall send a Routing Area Update Request message to the SGSN containing its new DRX Parameters. If ISR had been activated for the MS, then the MS shall deactivate ISR by setting its TIN to "P-TMSI" so that the MS performs a Tracking Area Update when it next enters E-UTRAN coverage. When the UE performs that Tracking Area Update, the MME will receive the updated DRX parameters within the MM context information sent by the old SGSN and hence the UE should not include them again in the Tracking Area Update.
  在A/Gb模式的inter-SGSN变化发生时，DRX参数作为MM上下文信息的一部分由old SGSN发送给new SGSN。因此，除非DRX参数发生了变化，UE都不会在RAU消息中包含DRX参数并发送给一个A/Gb模式的SGSN。
  如果一个UE期望在A/Gb模式下改变它的GERAN或UTRAN/E-UTRAN DRX参数，那么它应发送一个RAU请求消息给SGSN并包含新的DRX参数信息。如果ISR为了这个MS激活了，那MS应通过将TIN设置为"P-TMSI"而将ISR去激活，这样MS就可以在下一次进入E-UTRAN覆盖范围的时候执行一个TAU。当UE执行了这个TAU，MME将从old SGSN发过来的MM上下文信息里收到更新的DRX参数，因此UE不应再在TAU中携带这个DRX参数。

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主要目的是为了能让手机节电。
前言
   现代的手机具有比以往产品复杂得多的电路，仅是让接收器、音频和处理器一直运行着等待一个电话就会迅速耗尽电池的电量。
   对许多产品来说，很多时候都是器件“开着”但并没在使用。处于“待机”状态的手机就是最明显的这类例子。用户将手机“开着”等待来电，但事实上它大部分时间什么事都不做。
  手机大部分时间什么事都不做这一事实可被用来延长电池寿命。手机中的处理器完全可以在大部分时间都把很多功能关掉。它要仔细地规划醒来后的时间，以便检查是否有来自基站的传呼信号，验证是否还在覆盖范围内，在必要时切换到一个新蜂窝，以及检查是否有来电。由于呼叫方的耐心也许有限，因此来电通知不会持续很长时间。尽管让接收器长时间关着可以节省电池使用时间，但经常打开它听听来电可减少错过来电的情况。

不连续接收和发射
   GSM系统具有称为“不连续接收”(Discontinuous Receive，DRx)的节电方案。具体情况是，手机一直睡眠，每隔几个“多帧”(大约相当于八分之一秒的时间段)才醒来一次。系统可以指示手机每秒4次醒来检查是否有来电(DRx2)，或大约每秒1次(DRx9)醒来。这种作法牺牲的是检测到来电所需的时间。在DRx操作中，处理器将关闭接收器并使自己进入低功耗的睡眠模式。一个内部定时器会在经过适当的睡眠时间之后重新启动处理器。
   醒来的过程实际上相当复杂。在处理器醒来之后，它必须开启RF电路的DC电压。首先它要打开并调整合成器使之有机会稳定，然后它要打开接收器的各个模拟放大器部分并指示它们执行各自的校准例程。天线开关要切换到“接收”，并且RF前端要开启。DSP要启动并开始转换收到的突发数据。一旦接收到了数据，接收器的RF和模拟部分就会关闭，同时DSP会完成对已接收数据的解码，然后处理器将决定如何处理这些数据。除非处理器需要根据这些数据采取行动，否则它就会让自己进入睡眠，直到下次被唤醒。
  我们是可以简单地在突发接收之前提前足够多的时间就将所有东西都打开，以便使合成器可以调整好，并使DC自适应例程得以进行，但如果把各种电路的开启时间错开以便它们只在需要时才开启，那么几微秒的时间就可以节省几十毫安。其结果可能是，待机时的平均电流消耗可以节省多达10%，这显然相当于待机时间增长了10%，从而可能使你的产品具有竞争优势。
  在GSM手机通话期间，RF电路的时序也是类似的，但突发接收的发生要频繁得多，大约每4.6毫秒一次，同时突发接收与突发发射混杂在一起。对于GSM所用的时隙，接收器和发送器RF以及模拟部分每个都开启约八分之一的时间。显然发射期间的功率放大器是最耗电流的，但具体消耗多少则不一定，因为对RF输出功率进行了动态控制使其信号强度刚好足够达到基站。此外，GSM还有一项称为“不连续发射”(DTx) 的功能，它使发射器在用户没有说话时跳过发射脉冲。这一功能延长了电池使用时间，因为几乎每个人用电话时都有50%的通话时间是只听不说的。定期发射脉冲仍然是需要的，以便使网络可以确认电话仍在覆盖范围内并且仍在通话中。

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  A/Gb mode Radio Resource Management functions are defined in TS 24.007 [12]. The radio interface layer 3 protocol is specified in TS 24.008 [13].
A/Gb模式的无线资源管理功能在TS24.007中定义。空中接口的层3协议在TS24.008中定义。

8.1.3.1 Layer Functions
  GPRS radio resource management procedures are required for the following functions:
-  allocation and release of physical resources (i.e. timeslots) associated with a GPRS channel;
-  monitoring GPRS channel utilisation to detect under-utilised or congested GPRS channels;
-  initiating congestion control procedures; and
-  distribution of GPRS channel configuration information for broadcasting to the MSs.
  The radio resource management features that are required for PS handover are detailed in TS 43.129 [87].
  GPRS无线资源管理流程要求完成以下功能：
- 分配和释放和某一个GPRS信道相关联的物理资源（也就是时隙）。
- 监管GPRS信道利用率来检测超负荷或拥塞的GPRS信道；
- 发起拥塞控制流程；并且
- 将GPRS信道的配置信息通过广播的方式分发给MS。
  针对PS切换所要求的无线资源管理特性在TS43.129中描述。

8.1.3.2 Model of Operation
8.1.3.2.1 Dynamic Allocation of Radio Resources
  An A/Gb mode cell may or may not support GPRS.
  A cell supporting GPRS may have GPRS radio resources allocated at a given instance. If no GPRS radio resources are allocated, an MS can request allocation of such resources. MSs may then use these radio resources. The PLMN may dynamically increase, to a PLMN operator-defined maximum, or, decrease to an operator-defined minimum, the radio resources allocated.
  The network broadcasts GPRS system information on the common control channels.
  A/Gb mode radio resources are dynamically shared between GPRS and CS domain services.
  一个A/Gb模式的小区也许能也许并不能支持GPRS。
  一个支持GPRS的小区在一个给定的例子中可以有分配到的GPRS无线资源。如果没有GPRS无线资源分配，MS可以请求这些资源的分配。MSs然后就可以使用这些无线资源。PLMN可以根据需要，将分配的无线资源动态的增加到一个PLMN运营商定义的最大值，或者减少到定义的最小值。
  网络侧在公共控制信道（CCH）上广播GPRS系统消息。
  A/Gb模式的无线资源在GPRS和CS域提供的服务上动态的共享。

8.1.3a Ready to Standby state transition in S4 architecture
  When idle mode packet buffering is performed in the S GW, the SGSN needs to inform the S GW each time that the MS changes from READY state to STANDBY state. The following figure illustrates the procedure between SGSN and S GW.
  当Idle模式的数据包在SGW中有执行缓存，SGSN需要在每一次MS从READY转换到STANDBY状态的时候都通知SGW。下面的图例就描述了这个在SGSN和SGW之间的流程。

Figure 55-5: READY to STANDBY transition within the network using S4

1. The READY timer expires in the SGSN.
2. If PDP Contexts associated are to be preserved:
-  if ISR is activated for that MS, the SGSN shall send a Release Access Bearers Request to the S GW to remove the SGSN address for user plane and downlink S4 GTP-U TEID;
-  if ISR is not activated for that MS, the SGSN may send a Release Access Bearers Request to the S GW to remove the SGSN address for user plane and downlink S4 GTP-U TEID.
3. If the S GW received a Release Access Bearers Request, the S GW returns a Release Access Bearers Response to SGSN.
  1 SGSN中的READY timer超时。

  2 如果关联的PDP上下文被保持：

- 如果ISR为这个MS激活，SGSN应发送Release Access Bearers Request给SGW来删除用户面的SGSN地址和下行S4 GTP-U TEID;

- 如果ISR没有为这个MS激活,SGSN可以发送Release Access Bearers Request给SGW来删除用户面SGSN地址和下行S4 GTP-U TEID.

  3 如果SGW收到了这个请求，SGW返回一个Release Access Bearers Response给SGSN。

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  An MS in STANDBY state is paged by the SGSN before a downlink transfer to that MS. The paging procedure shall move the MM state to READY to allow the SGSN to forward downlink data to the radio resource. Therefore, any uplink data from the MS that moves the MM context at the SGSN to READY state is a valid response to paging.
  The SGSN supervises the paging procedure with a timer. If the SGSN receives no response from the MS to the Paging Request message, it shall repeat the paging. The repetition strategy is implementation dependent.
  The MS shall accept pages also in READY state if no radio resource is assigned. This supports recovery from inconsistent MM states in the MS and the SGSN.
  The GPRS Paging procedure in A/Gb mode is illustrated in Figure 56.
  一个STANDBY状态的MS在接收下行数据传递之前，首先要接收来自SGSN的寻呼。寻呼的流程应将MM状态迁移到READY，来允许SGSN来转发下行数据到这个空口的资源。因此，任何从MS来的上行数据都将做为一个有效的寻呼响应，并将在SGSN中MM上下文的状态变更为READY状态。
  SGSN通过一个计时器来监管寻呼流程。如果SGSN没有在寻呼请求消息发送后从MS收到任何响应，它将重复进行寻呼。重复的策略和具体的实现有关。
  如果没有分配任何空口资源的话，即使MS在READY状态也应接受这个寻呼。这将使得MS和SGSN的MM状态的不一致现象消除，并且同步。
  GPRS A/Gb模式的寻呼流程在图例56中描述。

Figure 56: GPRS Paging Procedure (A/Gb mode)

NOTE: The procedure describes the flow when there is an established user plane between SGSN and GGSN with Gn/Gp based SGSN, or between SGSN and S GW with S4 based SGSN. In case of an S4 based SGSN, when the S GW has no downlink user plane TEIDs, procedure steps (A) and (B) are defined in clause 8.1.4A.
  注释：流程描述了当在SGSN和GGSN之间（这个SGSN是基于Gn/Gp的）或SGSN和SGW之间（这个SGSN是基于S4的）建立了用户平面的数据流。如果是基于S4 SGSN的case，当SGW没有下行用户数据的TEID，流程中的步骤(A)和（B）在章节8.1.4A中描述。

1)  The SGSN receives a DL PDU for an MS in STANDBY state. Downlink signalling to a STANDBY state MS initiates paging as well.
2)  The SGSN sends a BSSGP Paging Request (IMSI, P TMSI, Area, Channel Needed, QoS, DRX Parameters) message to the BSS serving the MS. IMSI is needed by the BSS in order to calculate the MS paging group. P TMSI is the identifier by which the MS is paged. Area indicates the routeing area in which the MS is paged. Channel Needed indicates GPRS paging. QoS is the negotiated QoS for the PDP context that initiates the paging procedure, and indicates the priority of this Paging Request relative to other Paging Request messages buffered in the BSS. DRX Parameters indicates whether the MS uses discontinuous reception or not. If the MS uses discontinuous reception, DRX Parameters in combination with the IMSI indicate when the MS is in a non-sleep mode able to receive paging requests.
  1）SGSN收到了一个发给STANDBY状态MS的下行PDU。也可以是到MS的下行的信令消息。

  2）SGSN发送一个BSSGP 寻呼请求(IMSI、P-TMSI、区域、需要的信道、QOS、DRX参数）消息给为MS服务的BSS。IMSI是需要包含的，因为BSS需要它来计算MS寻呼组。P-TMSI是在寻呼MS对MS的标识。区域则指明了MS寻呼的路由区。需要的信道指明了GPRS寻呼。QOS指的是发起寻呼流程为这个PDP上下文协商的QOS，并且指明了这个寻呼请求相对于那些缓存在BSS中的寻呼请求的优先级的对比。DRX参数指明了MS是否使用不连续接收。如果MS使用了不连续接收，DRX参数将和IMSI一起来指明当一个MS是在非睡眠模式能接收寻呼请求。

3)  The BSS pages the MS with one Paging Request (P TMSI, Channel Needed) message in each cell belonging to the addressed routeing area. This is described in TS 43.064 [11].
4)  Upon receipt of a GPRS Paging Request message, the MS shall respond with either any single valid LLC frame (e.g. a Receive Ready or Information frame) that implicitly is interpreted as a page response message by the SGSN. The MS shall not use the LLC NULL frame as a page response. When responding, the MS changes MM state to READY. The Packet Channel Request precedes the response and Packet Immediate Assignment procedures as described in TS 43.064 [11].
5) Upon reception of the LLC frame, the BSS adds the Cell Global Identity including the RAC and LAC of the cell and sends the LLC frame to the SGSN. The SGSN shall then consider the LLC frame to be an implicit paging response message and stop the paging response timer.
  3）BSS带上寻呼请求（P-TMSI、需要的信道）在指明的路由区的每个小区来寻呼MS。这在TS43.064中描述。

  4）一旦接收到一个GPRS寻呼请求消息，MS应响应任意类型的单一的有效LLC帧（例如一个Receive Ready或Information帧），这个帧将被隐含的做为寻呼响应消息发给SGSN。MS不应使用LLC NULL帧做为寻呼响应。当响应了的话，MS的状态切换为READY。Packet Channel Request处理响应，和Packet Immediate Assignment流程在TS43.064描述。

  5）一旦接收到LLC帧，BSS加入CGI(小区全球标识符）以及小区的RAC和LAC然乎发送给SGSN。SGSN应认为这些帧是一个隐含的寻呼响应消息并且停止寻呼响应计时器。

8.1.4A Paging response for GPRS Downlink Transfer with no established user plane on S4

Figure 56a: Paging with no established user plane on S4

Figure 56b: Paging Response with no established user plane on S4

NOTE: Steps A, B and E are common for architecture variants with GTP based S5/S8 and PMIP-based S5/S8. For a PMIP-based S5/S8, procedure steps (C) are defined in TS 23.402 [90]. Steps C and D concern GTP based S5/S8.
   注释：步骤A/B/E对于采用基于GTP还是PMIP的S5/S8架构来说都是公共的。对于基于PMIP的S5/S8，步骤C在TS23.402描述。步骤C和D和基于GTP的S5/S8架构相关。

A) When the S GW receives a downlink PDU and no downlink user plane exists for the UE at S4, the S GW buffers the downlink data packet and identifies which SGSN is serving that UE.
   If that SGSN has requested the S-GW to throttle downlink low priority traffic and if the downlink data packet is received on a low priority bearer to be throttled (see clause 5.3.6.5), the SGW drops the downlink data packet. The steps below are not executed.
   Otherwise the S-GW sends a Downlink Data Notification message to the SGSN.
Steps between A and B are described in clause 8.1.4.
  A)当SGW收到一个下行PDU并且没有关于这个UE的下行用户平面在S4接口存在的时候，SGW将这些下行数据报文缓存起来，并识别出是哪个SGSN为这个UE提供服务。

  如果那个SGSN请求SGW将低优先级的下行流量扼杀掉并且如果下行数据报文是在一个低优先级的将被扼杀的承载中收到的话（参考章节5.3.6.5），SGW丢弃下行数据报文。下面的步骤将不会执行。

  除此以外，SGW将发送Downlink Data Notification消息给SGSN。步骤A和B在章节8.1.4描述。

B) Upon reception of the LLC frame in STANDBY state and if the user plane tunnel does not exist, the SGSN shall indicate the paging response from GERAN by sending a Modify Bearer Request (SGSN user plane address, RAT Type, TEID) to the Serving GW. The S GW is now able to transmit downlink data towards the UE.
C) If the RAT Type has changed compared to the last reported RAT Type, the S GW shall send the Modify Bearer Request message (RAT Type) to the PDN GW.
D) The PDN GW sends the Modify Bearer Response to the S GW.
E) The S GW sends a Modify Bearer Response to the SGSN.
    B)一旦SGSN在STANDBY状态接收到LLC帧并且没有用户平面隧道存在，SGSN应发送一个Modify Bearer Reqeust（SGSN用户面地址、RAT类型、TEID）给SGW来指示从GERAN收到了寻呼响应。SGW现在能够将下行数据传递给UE了。

  C）如果RAT类型和上次报告的RAT类型发生了变化，SGW应发送一个Modify Bearer Reqeust(RAT类型)消息给PGW。

  D)PGW发送一个Modify Bearer Response给SGW。

  E)SGW发送一个Modify Bearer Response给SGSN。

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8.1.5.1 General
  The RAN Information Management (RIM) procedures provide a generic mechanism for the exchange of arbitrary information between applications belonging to the RAN nodes. The RAN information is transferred via the SGSN core network node(s). In order to make the RAN information transparent for the Core Network, the RAN information is included in a RIM container that shall not be interpreted by the Core Network nodes.
  The RIM procedures are optional both in the RAN node and in the SGSN. For the Gb interface the use of RIM procedures is negotiated at start/restart of the Gb link. For the Iu interface there is no negotiation of using RIM procedures or not at Iu link start/restart.
  RIM流程提供了一个在RAN节点的应用部分之间交换信息的新的交换机制。RAN的相关信息将通过SGSN核心网节点进行传递。为了使得RAN的这些信息对核心网络来说是透明的，RAN信息将被包含在一个RIM容器(container)当中，并且不被核心网络节点解释。
  RIM流程对于RAN节点和SGSN来说都是可选的。Gb接口中关于RIM是否使用是在Gb链路的启动/重启的时候进行协商的。对于Iu接口来说，是否使用RIM流程则在Iu链路启动/重启的时候不进行协商。
  The RAN information is transferred in RIM containers from the source RAN node to the destination RAN node by use of messages. Each message carrying the RIM container is routed and relayed independently by the SGSN(s). Any relation between messages is transparent for the SGSN, i.e. a request/response exchange between RIM applications, for example, is routed and relayed as two independent messages by the SGSN.
  The interfaces which will be used are the Gb (BSSGP) , the Iu (RANAP), the Gn (GTPv1) and the S16 (GTPv2) interfaces. The RAN information in the RIM container shall be transparent for the Core Network. An SGSN supporting the RIM procedures provides addressing, routeing and relay functions.
   RAN的信息被包含在RIM容器做为消息的一部分从源RAN节点到目的RAN节点进行传递。每个消息都包含了RIM容器，并且都独立地通过SGSN进行路由和中继找到下一跳。消息之间的任何联系对SGSN来说都是透明的，也就是在RIM上层应用之间的请求/响应交换，举个例子，这在SGSN中将做为两个独立的消息进行路由和中继。
   使用的接口包括Gb（BSSGP)、Iu（RANAP)、Gn（GTPV1)和S16（GTPV2）接口。RIM容器当中的RAN信息应对核心网来说是透明的。一个支持RIM流程的SGSN提供了寻址、路由和中继的功能。
8.1.5.2 Addressing, routeing and relaying
8.1.5.2.1  Addressing
  All the messages used for the exchange of RAN information contain the addresses of the source and destination RAN nodes. A BSS is addressed by Routeing Area Identity (RAI) + Cell Identity (CI) of one of its cells. An RNC is addressed by Global RNC-Id.
  所有的包含了RAN信息的消息都包含了源和目的RAN节点的地址信息。一个BSS是由一个RAI+CI来标识地址信息。一个RNC的地址信息由全局RNC-Id来标识。
8.1.5.2.2  Routeing
  The following description applies to all the messages used for the exchange of RAN information.
The source RAN node sends a message to its SGSN including the source and destination addresses. An RNC sends in addition a RIM routing address, which is a copy of the destination address. From the destination address or from the RIM routing address, the SGSN shall decide whether or not it is connected to the destination RAN node.
  If the SGSN is not connected to the destination RAN node, then it shall use the destination address or the RIM routing address to route the message encapsulated in a GTP message to the correct SGSN via the Gn interface. If the destination address or RIM routing address identifies an RNC the SGSN includes the RIM routing address in the GTP message. If the SGSN received the message from a BSC it copies the destination address from the message into the RIM routing address.
  The SGSN connected to the destination RAN node decides which RAN node to send the message to based on the destination address or on the RIM routing address.
  下面的描述适用于所有RAN信息的交换的消息。源RAN节点发送一个消息给它的SGSN并包含了源和目的地址。一个RNC另外还发送了一个RIM路由地址，这是从目的地址拷贝过来的。根据目的地址或者RIM路由地址，SGSN应决定是否和目的RAN节点有连接。
  如果SGSN没有和目的RAN节点连接，那它应使用目的地址或RIM路由地址来进行路由，并将这个消息封装到GTP消息中通过Gn接口给到正确的SGSN。如果目的地址或RIM路由地址识别出来了一个RNC，那SGSN将在GTP消息中包含RIM的路由信息。如果SGSN从一个BSC收到了相应的消息，它将把消息的目的地址复制到RIM路由地址。
  连接到目的RAN节点的SGSN将根据目的地址或RIM路由地址来决定给哪个RAN节点发送消息。
8.1.5.2.3 Relaying
  The SGSN performs relaying between BSSGP messages, RANAP messages and GTP messages as described in TS 48.018 [78], TS 25.413 [56b] and TS 29.060 [26].
  SGSN在BSSGP/RANAP/GTP消息之间执行中继的功能，这些在规范48.018/25.413/29.060中分别描述上述三种协议。
8.1.5.3 Applications using the RIM Procedures
   The RAN node applications, which use the RIM procedures, are fully transparent for the SGSN. These applications are described in RAN specifications. An example is the Network Assisted Cell Change described in TS 48.018 [78] and TS 25.413 [56b].
   RAN节点的上层应用，也可以使用RIM流程，这对SGSN是完全透明的。这些相关的上层应用在RAN的规范中描述。一个例子就是网络侧辅助的小区更改（NACC)，这在TS48.18和TS25.413描述。

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  In Network Operation Mode II and III, paging from one CN domain is done independently from the state of the MS in the other CN domain, i.e. no paging co-ordination on core network level is done.
  在网络模式II和III，从一个核心网域来的寻呼和在另一个核心网域的MS的状态是完全独立的，也就是说在核心网络这个级别，没有寻呼的协调需要完成。
  It is, however, possible to do paging co-ordination on BSS level in these cases. This means that for each paging request received from one CN domain, the BSC determines whether the MS is engaged with the other CN domain or not. In order to achieve this, the context that is prepared within the BSC for an MS engaged with one of the CN domains must contain the IMSI, which is the common MS identity for the two CN domains.
  这就是，有可能在这些例子中在BSS这个级别完成寻呼的协调。这意味着对于从一个核心网域（CS或PS)来的寻呼请求，由BSC来判断这个MS是否有到其他的核心网域的连接，从而决定通过哪个空口的信道对这个MS发起请求。为了实现这个目标，在BSC中为这个参与某个核心网域（CS或PS)的MS所准备的上下文中一定要包含IMSI，因为这是两个核心网域（CS或PS)的公共的MS身份信息。
  If the BSC determines that the MS is engaged with the PS domain, the CS paging will be done on a packet data channel for the MS in question.
  BSC通过查找对应的MS在BSC中的上下文，发现MS正在使用PS域，如果这时有一个到MS的CS寻呼请求（即有个MS的呼入电话），那CS的寻呼将通过一个PS的数据报文信道对MS进行寻呼。
  If the BSC determines that the MS is engaged with the CS domain, the PS paging (packet notification) will be done on a CS dedicated channel for the MS in question.
  BSC通过查找对应的MS在BSC中的上下文，发现MS正在使用CS域，如果这时有一个到MS的PS寻呼请求（即有MS的下行数据），那PS的寻呼将通过一个CS的专用信道对MS进行寻呼。（否则这个MS有可能无法收到这个寻呼请求）。
  If no context is found for the MS, "normal CS paging" is performed on the CCCH paging channel and "normal PS paging" is performed on the CCCH paging channel or the packet paging channel, as applicable.
  如果没有找到这个MS的上下文信息，“正常的CS寻呼”将在CCCH寻呼信道，并且“正常的PS寻呼”也在CCCH寻呼信道或数据寻呼信道完成。
  If BSS paging co-ordination for CS paging is active in a cell or not, shall be indicated as system information to the MSs. For proper operation, the mode should be the same in each cell of a routeing area.
  BSS paging co-ordination for PS paging shall always be active in a cell where DTM is supported and is applicable to MSs supporting DTM.
  如果针对CS寻呼的BSS寻呼协调在这个小区是激活的，或者没有激活，都应做为系统信息指示给MS。对于正确的操作，一个路由区的每个小区的模式应该是相同的。
  针对PS寻呼的BSS的寻呼协调应在这个支持DTM的小区一直是active的，并且对于支持DTM的MS也适用。

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