GSM Call Process

Category: Education

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Slide 1: 

GSM call process By: Mohamed saeed abd el kreem mohamed

Slide 2: 

GSM Call Process 10/1

Introduction: : 

Introduction: A mobile station (MS) can be in one of the following states: Detached – MS is powered off or the SIM card is deactivated Attached – MS power is on and the SIM card is activated. An attached MS can be: Idle – MS has no dedicated channel allocated. It just listens to base stations broadcasted signals to remain attached Active (dedicated) – MS has a dedicated connection to the network 10/2

Call process procedure : 

Call process procedure Mobile initialization authentication and security Location update Outgoing voice call Incoming voice call Call hand over International roaming SMS 10/3

Mobile initialization : 

Mobile initialization Frequency synchronization(FCCH channel) Time synchronization(SCH channel) overhead information acquisition : When a mobile station is successful in synchronizations it reads four time-slot long Broadcast Control channel (BCCH) for the system information The information in the BCCH channel includes: Location Area ID (LAI) Cell ID (CID) Information about the locations of common control channels (paging, random access and access grant channels) Base station’s minimum received signal power to access the network Update period (location update) 10/4

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RACH send channel request AGCH receive SDCCH Authentication and TMSI allocation request traffic channel assignment command SDCCH send call establishment request SDCCH send the setup message and desired number traffic channel assignment complete FACCH receive alert signal ringing sound FACCH acknowledge connect message and use TCH FACCH receive connect message Outgoing voice call Authentication and TMSI allocation response 10/5

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Incoming voice call The PSTN subscriber keys in the MS’s telephone number (MSISDN) and Forwarding call to GSMC The GMSC analyzes the MSISDN to find out which HLR the MS is registered in The HLR translates MSISDN into IMSI, and determines which MSC/VLR is currently serving the MS. 4. The HLR requests an MSRN from the serving MSC/VLR 5. The MSC/VLR returns an MSRN via HLR to the GMSC. 6. The GMSC analyses the MSRN and routes the call to the MSC/VLR 7. The MSC/VLR knows which LA the MS is located in. A paging message is sent to the BSC’s controlling the LA. 8. The BSC’s distribute the paging message to the BTSs in the desired LA 10/6

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Receive signaling channel SDCCH on AGCH Receive alert signal and generate ringing on FACCH Authentication request on SDCCH Generate Channel Request on RACH Answer paging message on SDCCH Authentication response on SDCCH Receive call setup message on SDCCH Receive connect message on FACCH Receive traffic channel assignment on SDCCH Mobile receives paging message on PCH Incoming voice call FACCH acknowledge connect message and switch to TCH 10/7

SMS(Short message service): : 

SMS(Short message service): The Short Message Service (SMS) allows a mobile subscriber to send and receive text messages composed of 160 characters at most. These messages can be read on the phone’s LCD panel and they are delivered using the signaling channel SACCH; so short messages can be received while a call is in progress. The short messages sent or received are handled by the Short Message Service Center (SMSC), which consists of three parts: Service Center SC Short Message Service GMSC SMS-GMSC Short Message Service Inter-working MSC SMS-IWMSC 10/8

Short Message Delivery Process : 

Short Message Delivery Process 10/9

Unsuccessful delivery : 

Unsuccessful delivery Retry method Usage of “Alert Service Center” in the HLR 10/10

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