ion response Cipher Mode Command Cipher Mode Command Cipher Mode Command Ciphering Mode Setting Cipher Mode Complete Cipher Mode Complete Cipher Mode Complete TMSI Real Command TMSI Real Command TMSI Real Command Phase 8 TMSI Real Complete TMSI Real Complete Setup TMSI Real Complete Initiation Setup Data Indication Setup Call Proceeding Call Proceeding Call Proceeding Assignment Request Physical Context Request Physical Context Confirm Channel activation Traffic Channel activation acknowledgement Channel Assignment Command Assignment Phase 3 Assignment Command Establish Indication Assignment Complete Assignment Complete Data Indication Assignment Complete RF Channel Release RF Channel Release acknowledgement Alert Alert Alert Confirmation Connect Connect Phase 2 Connect Connect Acknowledgement Connect Acknowledgement Accepted Connect Acknowledgement & Conversation Measurement Report Measurement Report SACCH (System Info 5 or 6) MS Power Control Phase 15 BS Power Control Measurement Report Measurement Report SACCH (System Info 5 or 6) Disconnect Disconnect Disconnect Release Release Release Release Complete Release Complete Release Complete Clear Command Channel Release Channel Release Deactivate SACCH Disconnect LAPDm Phase 4 Release Indication Release Clear Complete RF Channel Release RF Channel Release Acknowledgement, Figure 2.63 MOC scenario signalling illustrated with call phases Radio Network Planning and Optimisation First, the called party is paged; hence the channel request is a response to the paging_request. The first message sent on the SDCCH is the paging_response and not the CM_service_request. The MSC-VLR initiates the setup message, not the MS. Location update and handover signalling charts follow the same philosophy and can be found in the GSM literature. Optimisation through Signalling Charts Practically speaking, the air interface is impossible to trace via a tool. In the BSS subsystem, the most commonly traced and analysed interface is the Abis. Many messages transit on the Abis. Messages rele