1. 1 Channel Overview 3 Types 1.Broadcast Control Channel: Point to Multipoint, Downlink (BTS) to MS) (A)BCCH (Board cast Control Channel) It inform the Mobile about system confirmation parameter (LAI, Cell -Identity, Neighbouring Cell Identity. MS select best cell to attach BCCH on full power, never Frequency hopped. (B)FCCH (Frequency Correction Channel) Which is used to allow a MS to accurately tune to a BS; FCCH Transmits a constant frequency burst of the Radio carrier that is used by the MS for frequency correction.

2. 2 (C)SCH (Synchronization Channel);- SCH is used to synchronize time. SCH carries TDMA Frame number and BSIC (Base Station Identity Code) 2.CCCH (Common Control channel). They are Point To Multi Point and UP or Down link and carry signaling information necessary for Access Management function (e.g. allocation of dedicated control channels.) This include --- 1.PCH (Paging Channel)- Down Link, used for paging when Incoming call. 2.RACH (Random Access Channel)- Used by MS to request allocation of a specific dedicated control channel. (SDCCH) either in response to a paging message or for call Origination/Registration from the MS. This is an uplink Channel and Point to Point. 3.AGCH- Down Link- To assign a specific dedicated control channel (SDCCH) to MS (When MS request on RACH). It is Down Link Channel.

3. 3 Dedicated Control Channel Full Duplex, Point, For Signalling between BTS, & Certain MS. (A)SACCH- (Slow Associated Control Channel) (B)FACCH- (Fast Associated Control Channel) (C)SDCCH- (Stand Alone Dedicated Control Channel) Duplex chl.which is always allocated to TCH or SDCCH. SACCH- Slow Associated Control Channel. It is used for: -Radio link supervision measurement -Power Control -Timing Advance Information In 26 Frame Traffic Multiframe 13 th frame (frame no. 12) is used fro SACCH. SACCH – for NON URGENT PROCEDURES.

4. 4 (II)FACCH – Fast Associated Control - Used for Urgent Signalling; like handover during a call. - During call data is transmitted over TCH instead of Traffic data, this is marked by a flag known as stealing Flag. (III)SDCCH – Stand alone dedicated Control Channel. - Duplex, P to P used for Signalling in Higher Layer. - Carry all Signals when no TCH is allocated to MS. - Used for Service request, location update, Subscribers Authentication, Ciphering, Equipment Validation, Assignment of a TCH

5. 5 MS enters a new area under the control of new VLR. MS came from old VLR. MS listen to LAI (on BCCH) and compare this LAI to old LAI (in SIM) 1. MS detects a new LA and send channel request over RACH. 2. BSS receives channel request and allocates a SDCCH and forward channel assignment on AGCH. 3. MS send Location update request on SDCCH. In this message are TMSI & old LAI 4. BSS send update request to MSC. 5. MSC inform VLR for Location update request. MS can identify itself by IMSI or TMSI, in this case it is TMSI, and old LAI. Channel Request RACH Dedicated Signaling Channel Assignment AGCH Location Update Request (TMSI,old LAI SDCCH Location Update Request (TMSI,old LAI Location Update Request (TMSI,old LAI MSMSBSSMSCNew VLR 1 2 3 5 4 Um B A Mobile Location Update-Request for Service

6. 6 6.VLR analyses that TMSI received is old. For registration the IMSI of MS is required. VLR request to MSC to get IMSI 7. MSC forward, request for IMSI to MS through BSS. 8. MS reads IMSI and send to BSS over SDDCH and BSS sends to MSC. 9. MSC forwards the IMSI to VLR Request IMSI IMSI Acknowledge (IMSI) MSBSSMSCNew VLR 6 7 8 9 Um B A SDCCH IMSI Acknowledge (IMSI)

7. 7 AUTHENTICATION:- Key Ki is required it resides is 1-AUC, 2-SIM, Ki never transmitted on AIR. 10.New VLR sends request to HLR for authentication parameters for this IMSI. 11. HLR send request to AUC. 12. AUC using IMSI extracts subs Ki, AUC then generate a RAND Applies the Ki, RAND to Authentication algorithm (A3) and cipher Key generation algorithm (A8) to produce SRES, and cipher Key (Kc) AUC then returns to HLR an authentication triplets RAND, SRES, Kc. 13. HLR forward authentication triplets to VLR. Get Authentication Parameters (IMSI) MS New VLR MSC 10 11 12 13 D B Get Authentication Parameters (IMSI) Authentication Parameters (SRES,Kc RAND) HLRAUC Authentication Parameters (SERES,Kc RAND)

8. 8 Authenticate Mobile Station (RAND) MS New VLR MSC 14 15 16 17 D B Authentication Response (SRES) Authentication Response (SRES) SDCCH HLRAUC 14.VLR keeps 2 parameter Kc, SRES for later use and send message (including RAND) to MSC for MS authentication. 15.MSC send authentication request to MS, MS reads Ki from SIM, Applies RAND, Ki to algorithm (A3) and Cipher Key generation algorithm (A8) to produce SRES and Kc, MS saves Kc and will use Kc for ciphering. 16. MS returns the generated SRES to MSC. 17 MSC send SRES to VLR, VLR compares 2 SRES. It equal, MS passes authentication if unequal then SIM disabled. Now MS is under the control of new VLR and MS can be deregistered from old VLR. Authenticate Mobile Station (RAND) SDCCH

9. 9 Update Location (MSRN) New VLR HLR 18 19 20 21 DD De-register Mobile Station 18. VLR allots MSRN. New VLR sends message to HLR informing it that a given IMSI has changed location and send I/c call on MSRN. 19. HLR insert the MSRN into the record of IMSI, Now HLR returns to the VLR a copy of Subs profile. 20. HLR will send a message to old VLR for deleting the old entry of IMSI. 21. Old VLR frees up the old MSRN and deallocates the VLR entry for the specified IMSI, and sends an acknowledgement to HLR Old VLR Location Update Mobile Station De-registered Mobile location update

10. 10 Cipher_uplink_Channel SDCCH MS BSS 22 23 24 25 UmA Cipher_Radio_Channel (Kc) MSC Uplink_Channel_Ciphered SDCCH 26 Cipher_Radio_Channel (Kc) B The HLR&Old VLR have been informed that MS has been registered with an MSC, under control of New VLR, New VLR will allocate a TMSI, before this radio channel is encrypted. 22.VLR request MSC to Cipher Radio Channel. Cipher Key is included in this message 23.MSC forward this message to BSS. 24. BSS retrieves the Kc and ask MS to Cipher in uplink. 25. MS uses Kc already generated (during authentication) to cipher the Uplink and sends Confirmation over the ciphered channel to BSS. 26BSS sends Ciphered complete message to MSC. New VLR Ciphering Completed The BSS Ciphers The down_link_channel CIPHERING

11. 11 SDCCH MS BSS 27 28 29 30 UmA Location Update Accept (TMSI) MSC 31 Location Update Accept B 27. VLR Informs MSC for MS Location update. In this message New TMSI included. 28. MSC forward LA updation message (TMSI) to MS 29. MS stores New TMSI in SIM. MS now sends update complete message to MSC. 30. MSC request BSS to release signalling connection. 31. BSS sends “Radio resource” channel release to MS and releases SDCCH. 32. BSS then inform MSC that radio channel released. New VLR Clear Signaling Connection Release Radio Signaling Channel Location Update Complete SDCCH 32 Clear Complete TMSI-REALLOCATION

12. 12 MOBILE TO LAND CALL SCENARIO FOLLOWING PHASES ARE PERFORMED:- 1.REQUEST FOR SERVICE 2.AUTHENTICATION 3.CIPHERING 4.EQUIPMENT VALIDATION 5.CALL SETUP 6.RELEASE

13. 13 MS BSS 1 2 3 4 UmA Dedicated Signaling Channel Assignment AGCH MSC Channel Request RACH B Assume that MS is registered with system and has been allocated TMSI User enter the MSISDN and them presses the “send” Key 1. MS send a channel request on RACH. 2. BSS allocates a SDCCH on AGCH. MS Now Communicate on SDCCH with BSS & MSC till TCH is allocated 3. MS send Service request to BSS on SDCCH. In this message are TMSI & LAI. 4. BSS send Service request to MSC 5. MSC forward service request to VLR. Now Authentication & Ciphering phases take place. VLR Service Request SDCCH Service Request 5 The Authentication Phase The Ciphering Phase MOBILE TO LAND CONNECTION

14. 14 IMEI Request SDCCH MS MSC 6 7 8 9 F Check IMEI 6.MSC request MS to send IMIE. 7. MS send IMEI. 8. MSC request EIR to Check IMEI. EIR check that IMEI is within valid range and valid equipment. 9. EIR returns the results to MSC if results are – ve then MSC drop the call. If call continue, then MSC inform the N/W of the event. EIR IMEI Response (IMEI) SDCCH IMEI Check Results EQUIPMENT VALIDATION

15. 15 SDCCH MS BSS 10 11 UmA Call Setup Request) MSC Access Subscriber Data (DD,SI) B There are 2 steps in setting a call -Setting of a voice path between MS & MSC by allocating a radio traffic channel & a voice Trunk -Setting a voice path between MSC & PSTN. 10. MS send a call setup request to MSC. It included dialled digit 11. MSC request VLR to supply subs parameters. Requested message contain digit dialled (DD) and service indication (SI). 12. VLR will check for call barring etc. VLR will supply subs data for call processing. 13 MSC will inform MS that call is proceeding. New VLR Subscriber Data 12 SDCCH Call Proceeding) 13

16. 16 MS BSS UmA MSC B 14 MSC allocates a trunk to BSS for serving MS and request the BSS (TN) to allocate a radio channel (TCH) for MS. 15 BSS allocate Radio channel on SDCCH. 16. MS tunes TCH and send acknowledgement to BSS 17.BSS connects the radio channel to assigned trunk of MSC, BSS deallocate the SDCCH, BSS send trunk & radio assignment message to MSC. New VLR Assign Trunk & Radio (TN) Assign Radio Channel (TCH) SDCCH Radio Assignment Complete SDCCH 16 15 14 17 Trunk & Radio Assignment Complete

17. 17 Networking Setup (DD.) MS MSC 18 19 20 21 Connect (Answer) CALL SETUP – WITH LAND N/W - A path has been established between MS & MSC now a path will be established from MSC to PSTN 18. MSC send a N/W setup message to PSTN. In message are dialled digit and details of Trunk to be used for call. 19. PSTN inform MSC with networking alerting message. MS will hear ringing tone from PSTN. 20. MSC inform MS that the destination number is being alerted. 21. When B. party go off-hook, PSTN will inform the MSC of this event. Billing start, MS is connected to the destination party. 22. MSC informs the MS that the Connection has been established. 23. MS acknowledges the receipt of the connect message. PSTN Alerting TCH Networking Alerting 22 Connect TCH 23 Connect Acknowledgment TCH

18. 18 MS BSS UmA MSC B 24. MS initiate the release of call by pressing end button. MS will send the Disconnect message to MSC. 25. MSC send Release message to PSTN End to END connection is terminated. 26. MSC send Release message to MS. 27. MS send Release Complete message. 28. Voice Trunk between MSC & BSS is released. 29. The Traffic channel is cleared. 30. The Release of the Resources is completed. PSTN Disconnect TCH Release TCH Release Complete TCH 26 25 24 27 Networking Release Clear Command 28 Channel Release 29 TCH Clear Command 30 RELEASE OF CALL

19. 19 LAND TO MOBILE CALL PHASES OF A LAND TO MOBILE CALL. 1.ROUTING ANALYSIS 2.PAGING 3.AUTHENTICATION 4.CIPHERING 5.EQUIPMENT VALIDATION 6.CALL SETUP 7.RELEASE

20. 20 Home MSC C HLR Assume that MS is already registered and allocated TMSI and MS in his home system 1. PSTN subscriber dials MS ISDN. 2. GMSC request HLR to provide routing information about this MS. 3. HLR provide MSRN to GMSC, if MS is roaming is its home MSC area then MSRN = MS ISDN, if roaming in different MSC area then MS ISDN & MSRN are different. Assume that MS roaming in Home MSC area. 4. MSC inform VLR for a call to MS, In the message is MSRN. 5. VLR respond to MSC by LAI & TMSI. PSTN Incoming Call (MSISDN) Get Route (MSISDN) 3 2 1 4 Routing Information (MSRN) 5 Incoming call (MSRN) Perform Page (LAI, TMSI) VLR ROUTING ANALYSIS

21. 21 Home MSC C If MS is barred for I/c calls, then VLR inform MSC accordingly, them MSC will connect announcement. IF MS ROAMING IN ANOTHER MSC AREA. 4. The call is routed from home MSC to the visited MSC and MSRN is transmitted then to the VLR 5. The VLR sends a message to the visited MSC asking it to performs paging by passing to it the new LAI & TMSI of the MS. PSTN Route the Call (MSRN) 5 4 Incoming call (MSRN0 Perform Page (LAI, TMSI) VLR D Visited MSC

22. 22 BSS A 6. MSC used LAI given by VLR to determine which BSS should page, included in the message is the TMSI. 7. BSS broadcast TMSI, of MS in paging channel (PCH). 8. MS detects TMSI, or IMSI on paging channel MS asks channel request on RACH. 9. BSS allocates SDCCH on AGCH. Now onwards MS communicate as SDCCH till MS gets a TCH. 10. MS responds paging on SDCCH, in the message MS sends TMSI, LAI. 11. BSS send this message to MSC. 12. MSC informs its VLR that MS has responded. MS Perform Page (TMSI) 7 6 Page PCH Channel Request RACH Home or Visited VLR B Home or Visited MSC Um 8 9 Dedicated Signaling Channel Assignment AGCH 10 Page Response (TMSI,LAI) SDCCH 11 Page Response PAGING 12 Page Response

23. 23 BSS A Authentication Ciphering, Equipment validation are done in same manner as in Mobile to Land call. In the case, the MS is visiting a new MSC area, the authentication and Equipment Validation are performed as follows. -The Visited VLR request the authentication parameters from the Home AUC through the Network connecting the two MSCs and then through the “HOME” HLR. -The Equipment Validation phase involves the visited MSC & the “HOME EIR”. There are again two steps in setting up a voice path for a call from a mobile to a PSTN subscriber. -The call setup with the mobile :- A voice path is created between MS & MSC by allocating a TCH and a voice trunk. -The call setup with the land N/W:- Where a voice path is established between the MSC & a PSTN N/W MS Home or Visited VLR B Home or Visited MSC Um The Authentication The Cipher phase The Equipment Validation N/W

24. 24 Call Setup MS BSS 13 14 15 16 13. MSC inform MS that a call can be setup. 14. MS perform compatibility check it acknowledges the call setup message by setup confirm. 15. MSC selects a trunk to BSS and request BSS to allot a radio channel (TCH). 16. BSS allot TCH and transmits an Assignment command over SDCCH to MS. 17. MS tunes to TCH and transmits an assignment complete message back to BSS. MS user phone rings. MS do not use SDCCH after it gets TCH. 18. BSS on receiving assignment complete message connects the TCH to Trunk. SDCCH is free now and send Assignment Complete Message to MSC. Assign Radio Channel SDCCH Assign Trunk & Radio Channel 18 Trunk & Radio Assignment Complete Home or Visited MSC SDCCH Call Setup Confirm SDCCH 17 Radio Assignment Complete SDCCH

25. 25 MS 19 20 21 22 19. MS got TCH, MS begin alerting the user after if receives a TCH. A alerting message is sent to MSC. 20. MSC on getting alerting indication from MS will generate ringing to calling party and send a N/W alerting to PSTN. 21. Mobile subscribers answers, MS stops alerting and send connect message to MSC. 22. MSC removes audible tone to PSTN, and connects PSTN trunk to BSS trunk and send connect message to PSTN, Billing start. 23. MSC send a connect acknowledge to MS. Connect (off-hook) TCH Network Alerting Connect Home or Visited MSC 23 Connect Acknowledge TCH PSTN Mobile Alerting TCH Start Billing

26. 26 BSS A 24.MSC receives a Release message from the N/W to terminate the end to end connection. 25.MSC send disconnect message to MS. 26.MS send Release to MSC 27.MSC send Release complete to MS. 28.Voice trunk between MSC & BSS in cleared. 29.The Traffic channel is released. 30.The recourses are completely released. MS Network Release Disconnect) 26 25 24 27 Release TCH 28 Clear Command PSTN Um Home or Visited MSC TCH Clear Command 30 29 RELEASE

27. 27 Phase of a Mobile to Mobile call -Request for Service -Authentication* -Ciphering* -Equipment Validation* -Call Setup -Release -Routing Analysis -Paging -Authentication* -Ciphering* -Equipment Validation* -Call Setup -Release  Phase might not occur Originating Mobile Terminating Mobile

28. 28 Mobile to Mobile call phase divided in 2 parts Originating Mobile Point 1.MS to MSC is same as part of MS to Land call. 2.Terminating Mobile part same as land to Mobile call, i.e. PSTN to MSC Part.