Foreword1 Scope2 References3 Definitions, symbols and abbreviations4 Main Concepts5 General Circuit Switched Core Network Domain Architecture6 Call Establishment6.1 Basic Mobile Originating Call6.2 Basic Mobile Terminating Call6.3 Basic Mobile to Mobile End to End Call Examples6.3.1 Basic Call Establishment Connection Model for LCLS6.3.2 LCLS established, Basic Call Example with BICC based CS core network, forward bearer establishment6.3.3 LCLS not established, Basic Call Example with BICC based CS core network6.3.4 LCLS established, Basic Call Example with SIP-I based CS core network6.3.5 LCLS established, Basic Call Example with BICC based CS core network, backward bearer establishment7 Call Clearing and LCLS Break/Re-establishment7.1 Call Clearing7.2 LCLS Break7.2.1 MSC server Initiated7.2.2 BSS Initiated7.2.3 Intermediate Node/GMSC Server Initiated7.2.4 LCLS Break Example Call Flows7.3 LCLS Re-establishment7.3.1 MSC server Initiated7.3.2 BSS Initiated7.3.3 Intermediate Node / GMSC Server Initiated7.3.4 LCLS Re-establishment Example Call Flows8 Handover/Relocation8.1 UMTS to UMTS8.2 UMTS to GSM8.2.1 General8.2.2 Intra-MSC UMTS to GSM Handover8.2.3 Inter-MSC UMTS to GSM Handover8.3 GSM to UMTS8.3.1 Intra-MSC GSM to UMTS Relocation8.3.2 Inter-MSC GSM to UMTS Relocation8.4 GSM to GSM8.4.1 Intra-MSC Inter-BSS GSM to GSM Handover8.4.2 Inter-MSC GSM to GSM Handover8.4.3 Subsequent Inter-MSC GSM to GSM Handover back to the Anchor MSC8.4.4 Subsequent GSM to GSM Handover to a third MSC8.4.5 BSS Internal Handover8.5 Handling of GSM Services after UMTS to GSM Handover9 Compatibility Issues10 General (G)MSC server-MGW Procedures11 Identities12 Operational Aspects13 Interactions with Other Services13.1 Enhanced Multi-Level Precedence and Pre-emption service (eMLPP)13.2 Call Deflection Service13.2.1 General13.2.2 Notification to the Calling Subscriber13.2.3 Initial Addressing13.2.4 Backward LCLS Negotiation13.2.5 LCLS Through-Connection13.2.6 Example13.3 Line identification Services13.4 Call Forwarding Services13.4.1 Principles13.4.2 Call Forwarding Unconditional (CFU)13.4.3 Call Forwarding on mobile subscriber Busy (CFB)13.4.4 Call Forwarding on No Reply (CFNRy)13.4.5 Call Forwarding on mobile subscriber Not Reachable (CFNRc)13.5 Call Waiting (CW)13.6 Call Hold (CH)13.6.1 Principles13.6.2 Call Hold after Answer, LCLS established13.6.3 Call Hold after Answer, LCLS not established13.6.4 Establishment of a new call, the original call is hold13.6.5 Retrieval of the held call, ongoing call is on-hold/completed13.7 Multiparty (MPTY)13.8 Closed User Group (CUG)13.9 Advice of Charge (AoC)13.10 User-to-User Signalling (UUS)13.11 Call Barring Services13.12 Explicit Call Transfer (ECT)13.13 Completion of Calls to Busy Subscriber (CCBS)13.14 Multiple Subscriber Profile (MSP)13.15 Multicall13.16 Calling Name Presentation (CNAP)13.17 Alternate Speech/Fax13.18 Modification of the Access Bearer13.19 GSM Fax13.20 Voice group call service (VGCS), Voice broadcast service (VBS)14 Interactions with Other Network Features and Services14.1 Customised Applications for Mobile network Enhanced Logic (CAMEL)14.2 IST14.3 Operator Determined Barring (ODB)14.4 DTMF14.5 OR14.6 Providing tones or announcements14.6.1 General14.6.2 Handling of tones or announcements during an LCLS call14.7 Global Text Telephony14.8 Emergency Calls14.9 Subscriber and equipment trace14.10 Customized Alerting Tone14.11 Tandem Free Operation (TFO)14.12 Transcoder Free Operation (TrFO)14.13 CS Data Calls14.14 RTP Multiplexing15 Tunnelling16 Messages/Procedures and their contents17 Bearer Redirect18 (G)MSC MGW Tandeming19 Timers20 Multiple Realms20 Multiple Realms 12 Operational Aspects 23.2843GPPLocal Call Local Switch (LCLS)Release 17Stage 2TS Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM 12.1 Charging No impact.