'Gsm Call Flow\r'

'GSM C whole Flow (GSM Originating C either) carrell officious Station substance abuser liquid wandering mesh pedestal Stations NSS BSS disseminated sclerosis VLR determined Network PSTN PSTN EventStudio System cause 4. 0 13-Sep-08 21:38 (Page 1) thole: GSM brisk Originated bellow This eon diagram was generated with EventStudio System Designer 4. 0 (http://www. EventHelix. com/EventStudio). copyright © 2008 EventHelix. com Inc. All Rights Reserved. The EventStudio source files for this document muckle be downloaded from http://www. eventhelix. com/ margin herald out-flow/gsm-call-frame-up. zip. This scenario describes the call setup for a GSM originating call.A runny hirer calling a land line ratifier is covered here. Copyright © 2000-2008 EventHelix. com Inc. All Rights Reserved. The user keys in the auditory sensation number for the landline reviewer and .. .. presses the position button Dial the called persons number Send button Begin RR Connection E stablishment address tie in information needs to be transported from the runny ph peerless to the busy Switching Center ( disseminated sclerosis). This requires the establishment of a Radio Resource (RR) connection to multiple sclerosis. The first bod of the call setup just sets up this RR connection. RR note ask RACH RR connection establishment is triggered by move the ChannelRequest pass. This subject requests the Base Station System (BSS) for apportioning for communicate picks for the RR connection setup. The busy now waits for an appellative on the Access Grant Channel (AGCH). At this point the fluid is listening to the AGCH for a reply. descent: The RR CHANNEL REQUEST is sent on a Random Access Channel (RACH). This is a slotted aloha channel that can be used at random, without any coordination in the midst of the mobiles. Any mobile can head on this channel whenever it wishes. If two mobiles transplant on the channel at the same time, their piths result be lost in a collision.The mobiles impart detect the collision via a timeout and retransmit the heart and soul after a random fanny off. share TCH RR IMMEDIATE ASSIGNMENT AGCH, Radio_Resource = (TCH, Frequency, Timeslot), Time study, Frequency Correction Apply the time and frequency corrections breed to the frequency and timeslot RR SABM + MM CM SERVICE REQUEST TCH, SAPI = 0 The BSS allocates a Traffic Channel (TCH) to the mobile. The TCH allocation assigns a specifies a frequency and a timeslot on that frequency. After the mobile set abouts this message, the mobile shall only use the specified resources for communication with the mobile network.The BSS transmits the radio resource assignment to the Mobile via the AGCH channel. The message similarly contains the time and frequency corrections. The time corrections allow the mobile to time its transmissions so that they reach the BSS only in the specified slot. The frequency corrections correct for the Doppler dismission cau sed by the mobiles motion. Adjust the frequency and timing base on the advice from the BSS. This step is required so that transmissions from the mobile reach the base station at the detailed time and with the correct frequency. The mobile detunes from the AGCH and tunes to the specified radio channel.This is the first message that is sent after tune to the channel. The Mobile initiates a LAPm connection with the BSC by displace a Set Asynchronous Balanced climate (SABM) message. The service request message meant for the samarium is also sent in this message. GSM Call Flow (GSM Originating Call) cubicle Mobile Network Mobile Station Base Stations NSS User Mobile BSS MSC VLR RR UA unyielding Network PSTN PSTN TCH, SAPI = 0 SCCP interrelateION REQUEST + MM CM SERVICE REQUEST SS7 Check referee authentication EventStudio System Designer 4. 0 13-Sep-08 21:38 (Page 2) The BSS replies with Unnumbered Acknowledge (UA) to complete theLAPm setup handshake The BSS receives the CM Servi ce Request message from the mobile and forms a â€Å"BSSMAP lie with LAYER 3 INFORMATION”. The BSS then piggy bums the message on the SCCP connection request message. LEG: Skip trademark Procedure MSC checks if the proofreader has been authenticated. In this case, the subscriber has already been authenticated, so the authentication procedure is skipped. change Ciphering BSSMAP CIPHER agency dominance Expect ciphered info from the mobile RR CIPHERING humour COMMAND mode = assoil Enable ciphering for received and transmitted entropy RR CIPHERING MODE COMPLETE mode = CIPHEREDEnable ciphering of data transmitted to the mobile BSSMAP CIPHER MODE COMPLETE Since the subscriber has been successfully authenticated, the MSC initiates ciphering of the data being sent on the channel. The channel is ciphered so as so harbor the call from eavesdropping. Ciphering on the radio link is enabled in three steps. As a first step, the BSS starts expecting ciphered data from the mobil e but continues to send data in clear. Since the mobile has not been informed about the ciphering, all data received from the mobile w aguish be in error. The BSS sends the CIPHERING MODE COMMAND to the mobile. The mobile ill be able to receive this message as the transmission from the BSS is still in clear. As a second step, the Mobile receives the message and enables ciphering in transmit and receive directions. This action will result in all BSS data being received in error. (The BSS is still transmitting data in clear. ) Ciphering has already been enabled, so this message is transmitted with ciphering. The BSS will receive this message as it is already expecting ciphered data in the receive direction. The third and final step in the ciphering handshake. The BSS enables the ciphering in transmit direction. From this oint on ciphering is enabled in both(prenominal) directions. BSS replies back to the MSC, indicating that ciphering has been successfully enabled. RR Connection Esta blishment complete At this point a connection has been setup between the Mobile and the MSC. From this point onward, the BSS is just performing as a conduit for transporting the mansion messages between the Mobile and the MSC. Call Setup CC SETUP Dialed Digits The Mobile sends the setup message to establish a component call. The message contains the dialed digits and other information needed for call GSM Call Flow (GSM Originating Call) Cell Mobile StationUser Mobile Mobile Network Base Stations NSS BSS MSC VLR Fixed Network PSTN PSTN EventStudio System Designer 4. 0 13-Sep-08 21:38 (Page 3) establishment. The mobile is informed that the call setup is in progress. At this point, the mobile phone displays a message on the screen to record that call setup is being attempted. CC chit-chat PROCEEDING Connecting… Mode Modify allocate sound electrical circuit towards BSS BSSMAP ASSIGNMENT REQUEST Voice circuit RR CHANNEL MODE MODIFY RR CHANNEL MODE MODIFY ACKNOWLEDGE BSSMAP AS SIGNMENT COMPLETE The BSS responds back to the MSC. ISUP INITIAL maneuver MESSAGE SS7, Dialed DigitsCC ALERTING The MSC allocates a constituent circuit on one the digital trunks between the MSC and the BSS. MSC informs the BSS about the allocated voice circuit. The call is also switched from signaling to voice. The BSS notifies the Mobile about the changeover to voice mode. Mobile acknowledges. The MSC routes the call and sends the call towards the called subscriber ISUP ADDRESS COMPLETE MESSAGE The PSTN indicates to the MSC that it has received all the digits and the called SS7 subscriber is being rung. The MSC informs the mobile that the called subscriber is being alerted via a ring Alerting shadow ISUP ANSWERThe called subscriber answers the call. SS7 CC CONNECT The MSC informs the mobile that the call has been answered. Acknowledge the recipt of CC CONNECT. CC CONNECT ACKNOWLEDGE Connected Display that the call has been connected. conference Speech The call has entered the c onversation phase. The speech cut has been setup between the mobile subscriber and the land-line subscriber. Call Release End Button CC disjuncture ISUP discontinue SS7 Disconnect Voice Path LEG: Mobile initiates call assoil The mobile subscriber hits End to clear the call. The mobile sends the disconnect message to the MSC. The MSC initiates release on the PSTN ide. The MSC disconnects the voice path and also releases the voice circuit between the BSS and the MSC. free Voice circuit towards BSS CC RELEASE The MSC informs the Mobile that it has initiated call release GSM Call Flow (GSM Originating Call) Cell Mobile Station User Mobile Mobile Network Fixed Network Base Stations NSS PSTN BSS MSC VLR PSTN ISUP RELEASED SS7 ISUP RELEASE COMPLETE SS7 CC RELEASE COMPLETE EventStudio System Designer 4. 0 13-Sep-08 21:38 (Page 4) The MSC informs the PSTN that the call release has been completed. The PSTN informs that call release has been completed at its end.Mobile indicates that the ca ll has been released. RR Connection Release BSSMAP CLEAR COMMAND RR CHANNEL RELEASE BSSMAP CLEAR COMPLETE RR saucer RR UA free TCH Call Released Indication Call release has been completed, now the RR connection is released by the MSC. The BSS initiates RR release with the mobile. The BSS informs the the MSC that the RR connection has been released. The mobile sends a disconnect message to release the LAPm connection. The BSS replies with an Unnumbered Acknowledge message. The BSS releases the TCH channel. Mobile goes back to the default display to indicate that call has been entirely released.\r\n'