Layer 3 messages (2G)
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This document discusses L3 messages and system information messages in GSM networks. L3 messages are used for controlling mobile station behavior in idle and dedicated modes and for location updates. System information messages are downlink messages sent on the BCCH or SACCH channels to provide mobile stations with needed network information like cell parameters and neighbor cell lists. Examples of system information messages and their contents are provided.
Layer 3 messages (2G)
- 1. Prepared by Abdulrahman Fady
- 2. L3 Messages is the messages transferred between MS and Network (BSC or MSC ) to control the MS behavior in idle mode and in dedicated mode as well as tell MS when to do Location update L3 Messages are UL and DL and conveyed on Control channels ◦ BCCH ◦ PCH ◦ SDCCH ◦ SACCH ◦ FACCH
- 4. What are system Information Messages ◦ Downlink messages ◦ sent on BCCH channel or SACCH channel ◦ Used to inform MS by all the needed information to enable it to do its operations in normal way ◦ SI messages transmitted periodically from BTS and MS reads them every 30 sec for serving cell and every 5 minutes for six strongest cells ◦ There are a lot of SI types e.g. SI type 1, SI type 2
- 5. Direction : DL Channel : BCCH Contents ◦ BCCH Frequency ◦ Available frequencies ◦ RACH Control parameters as MAXRET ◦ Cell Barring ◦ Emergency
- 6. Direction : DL Channel : BCCH Contents ◦ BCCH frequency ◦ MAXRET ◦ Call re-establishment control ◦ NCC permitted range ◦ Cell Barring
- 7. Direction : DL Channel : BCCH Contents PLMN ID (MCC & MNC) Cell ID LAC MFRMS AGBLK Mapping Method ATT T3212 RL_timeout Selection Parameters ACCMIN MAX-TX-PWR-UL CRH Cell reselection CRO PT TO Half rate support SI scheduling
- 9. Direction : DL Channel : BCCH Contents PLMN ID (MCC & MNC) Cell ID LAC Cell Selection Parameters Cell Reselection Parameters
- 10. Direction : DL Channel : BCCH Contents Other Band BA list
- 11. Direction : DL Channel : BCCH Contents Same Band BA list
- 12. Direction : DL Channel : BCCH Contents GPRS Information EGPRS Supported Power control Network Mode
- 13. Direction : DL Channel : SACCH Contents GPRS Information Cell ID LAC PLMN ID RL timeout DTX info Band
- 14. Direction : DL Channel : SACCH Contents BA list
- 15. Direction : DL Channel : SACCH Contents Part from Active BA list
- 16. Direction : DL Channel : SACCH Contents Part from Active BA list Multi band reporting
- 17. Immediate Assignment ◦ SDCCH assignment during Call Setup Measurement Report ◦ MS should report 6 strongest neighbors cells to BSC Handover Command ◦ BSC instruct the MS to do HO to certain Cell Handover Access ◦ MS starts HO process Handover Complete ◦ Message sent after HO completed Successfully
- 18. Direction : DL Channel : AGCH Contents Inform MS about SDCCH that will be used in call Setup
- 19. Direction : UL Channel : SACCH Contents Six strongest neighbors
- 20. Direction : DL Channel : SACCH Contents Instruct the MS to handover to a certain cell by sending its information BCCH BSIC MAIO /HSN
- 21. Direction : UL Channel : FACCH Contents MS tries to access the new cell using this message
- 22. Direction : UL Channel : FACCH Contents MS inform the network that the HO has been completed successfully