[PPT模板]GSM信令流程介绍.ppt
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1、呼叫信令流程讲义 内容简介 内内 容容 q无线空中接口 q信道描述 q信令描述 q测量过程 q系统类型消息 q主叫信令流程 q被叫信令流程 q掉话信令判断 qERICSSON常见故障分析方法 q问题定位与案件分析 无线空中接口描述 一、无线空中接口 1、频率分配 The following frequency bands are allocated to the system: The carrier separation is 200kHz, this provides 124 carriers in the GSM 900 band, 374 carriers in the GSM 180
2、0 band and 299 in the GSM 1900 band. Since each carrier is shared by eight MSs, the total number of channels are: 无线空中接口描述 124 x 8 = 992 channels in GSM 900 374 x 8 = 2992 channels in GSM 1800 299 x 8 = 2392 channels in GSM 1900 Each of these channels, that is one time slot on a Time Division Multip
3、le Access (TDMA) frame, is called a physical channel. A variety of information is transmitted between the BTS and the MS. There are different types of logical channels depending on the type of information being transmitted。 Each logical channel is used for a specific purpose, e.g. paging, call setup
4、 or speech. These logical channels are mapped onto the physical channels, for example, speech is sent on the logicalchannel Traffic Channal(TCH) and during transmission this is allocated to a certain physical channel, say Time Slot 6(TS6) on a TDMA frame. 无线空中接口协议 2、空中接口协议 无线空中接口简称(Um)接口,即 BTS至MS的接口
5、。 用于BTS与MS之间的无线链路通信称作 LAPDm协议。用于携带BTS至MS之间的 各种信息。 信道描述 二、信道描述 1、LOGICAL CHANNELS(逻辑信道) There are 12 logical channels in the system. Two are used for traffic, nine for control signaling and one for message Distribution。 Traffic CHannels (业务信道): There are three types of TCHs: Full rate channel: - used
6、 for full rate speech at 13kbps or data up to 9.6kbps Half-rate channel: - used for half rate speech at 6.5kbps or data up to 4.8kbps Enhanced Full Rate: - used for full rate speech at 控制信道 2、CONTROL CHANNELS(控制信道) There are three different groups of control channels with each group containing three
7、 different logical channels。 2.1、Broadcast CHannels (BCH)(广播信道)(Downlink Only) Frequency Correction Channal(FCCH)(频率校正信道) - used for frequency orrection of MS Synchronization CHannel(SCH)(同步信道) - carries information about the TDMA frame number and the Base Station Indentity Code(BSIC) of the BTS Bro
8、adcast Control CHannel(BCCH)(广播控制信道) -Broadcasts cell specific information to the MS 公共控制信道 2.2、Common Control CHannels (CCCH)(公共控制信道) Paging Channel(PCH)(寻呼信道) - used on the downlink to page the MS Random Access Channel(RACH)(随机接入信道) - used on the uplink by the MS to request allocation of an SDCCH,
9、 either as a page response or an access at MS call origination/registration Access Grant Channel(AGCH)(允许接入信道) - used on the downlink to allocate an SDCCH or TCH to an MS. An allocation to a TCH can be done in the case of an Immediate Assignment on TCH, see Appendix A。 专用控制信道 2.3、Dedicated Control C
10、Hannels (DCCH) (Uplink and Downlink)(专用控制信道) Stand alone Dedicated Control Channel(SDCCH) (独立专用控制信道) - used for system signaling during call setup or registration, uplink and downlink, as well as the transmission of short text messages in idle mode。 Slow Associated Control Channel(SACCH)(慢速随 路控制信道)
11、- control channel associated with a TCH or a SDCCH. Measurement Reports from the MS to the BTS are sent on the uplink。 专用控制信道 (see section on Measurement Reports)。 On the downlink the MS receives information from the BTS on what transmitting power to use and also instructions on Timing Advance(TA) T
12、he SACCH is also used for the transmission of short text messages in call connected (busy) mode。 Fast Associated Control Channel(FACCH)(快速随路控制 信道) - Control channel associated with a TCH. Also referred to as Fast Associated Signaling(FAS),the FACCH works in stealing mode. That is, 20 ms of speech is
13、 replaced by a control message. It is used during handover as SACCH signaling is not fast enough. Used on uplink and downlink。 小区广播信道 2.4、Cell Broadcast CHannel (CBCH)( 小区广播信道) This is used only on the downlink to carry Short Message Service Cell Broadcast(SMSCB) CBCH uses the same physical channel
14、as the SDCCH。 信令描述 三、信令描述 CALL SETUP, MOBILE TERMINATED CALL The following call case is an example of how logical channels are used. The steps involved in a call setup are as follows: 1、PAGING(寻呼) The MSC/VLR finds the subscriber data in its database and initiates a call setup procedure by sending a
15、 Paging message to the relevant BSCs. The message contains the LAI and IMSI or TMSI。 2、Paging Command(寻呼命令) 信令描述 The BSC sends a message to all BTSs in the indicated Location Area(LA)。The message contains the IMSI or TMSI, the paging group (see Chapter on Radio Network Configuration, parameter MFRMS
16、),the Transceiver Unit (TRU/TRX) identity, the channel type and the time slot number。 3、Paging request(寻呼请求) This message is sent on a PCH from the BTSs to the MS. The information contains the IMSI or TMSI。 4、Channel request(信道请求) The paged MS responds by sending a short access burst on a RACH。 A sh
17、ort burst is used because this is the MSs first access with the network and a TA value has not yet been set.The message is received by the BTS where the access delay is registered。 信令描述 5、Channel required(信道需求) This message from the BTS to the BSC contains information such as the access delay value。
18、 6、Channel activation(信道激活) The BSC selects an idle SDCCH or TCH and requests activation of the channel。 7、Channel activation acknowledge(信道激活证实) The BTS acknowledges the activation request to the BSC。 8、Immediate assignment(立即指配) This message is sent transparently from the BSC to the MS via an AGCH
19、. The message contains information on the frequency,time slot number and the SDCCH sub channel that the MS should use, as well as the TA defining how much the MS must advance in bursts。 信令描述 Set Asynchronous Balance Mode (SABM) is used in order to establish a multiple frame operation. This is a type
20、 of LAPDm signaling. Unnumbered Acknowledged (UA) is used to acknowledge SABM。 注: SABM:为置异步平衡模式 作用:建立确认模式的第一帧 UA:无编号响应 作用:对SABM帧的应答 9、Paging response(寻呼响应) This message from the MS uses an SDCCH or TCH on the radio path. It contains, among other information, the IMSI or TMSI and the MS classmark. Th
21、e BSC adds the CGI, and the signal is forwarded to the MSC/VLR 。 信令描述 10、Authentication request(鉴权请求) The RAND parameter is forwarded by the “Authentication Request” signal from the MSC/VLR to be used by the MS for authentication and ciphering. The MS uses RAND together with its own Subscriber Authe
22、nticationKey(Ki), which is stored in the SIM card, to calculate the Ciphering Key( Kc)and a Signed Response(SRES)。 注:移动台在SDCCH上发送IMSI,用于VLR去提取其数据(三参数组) ,以进行下一步的鉴权、加密。鉴权在SDCCH信道上进行,其中 RAND、KC、SRES称为三参数组,由AUC产生。 11、 Authentication respone(鉴权响应) This message from the MS to the MSC/VLR contains SRES。 信令
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