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Elementary Procedures for CircuitSwitched (CS) Call Control (CC) in
3GPP
Presented by Louis K. H. Kuo
Outline
•
•
•
•
•
•
•

Introduction of Related Backgrounds
Overview on Call Control
Standard L3 Messages
Service State Dia...
Introduction of Related Backgrounds (1/2)
• The radio interface is layered into three protocol layers [1]:
– the physical ...
Introduction of Related Backgrounds (1/2)
• Radio Interface Protocol Architecture (Service Access
Points (SAPs) are marked...
Overview on Call Control (1/4)
• Call Control (CC) Protocol [2] or Call Control Function (CCF)
– One of the protocols of t...
Overview on Call Control (2/4)
• Three Basic Types of Calls
– MO Call
• The terms "mobile originating" or "mobile originat...
Overview on Call Control (3/4)

• Example [5]: To make a phone call.
– From MOC to PTC; from POC to MTC

• Protocol Archit...
Overview on Call Control (4/4)

• The CC service class consists of the following services [6]:
– MS side
•
•
•
•
•

MO and...
Standard L3 Messages (1/9)
• A standard L3 message [6]
– (1) Imperative part

Example: General message organization

• A h...
Standard L3 Messages (2/9)
• A standard IE has one of the formats as follows.

– LV-E and TLV-E are used for EPS Mobility ...
Standard L3 Messages (3/9)

• Example: Type 4 IE of format TLV

– A type 4 standard IE has format LV or TLV. Its LI preced...
Standard L3 Messages (4/9)
• For the EPS protocols (EMM and ESM), a standard L3 message can be
either a plain NAS message ...
Standard L3 Messages (5/9)

• Protocol Discriminator (PD)

(Note that the following contents focus on the standard L3 mess...
Standard L3 Messages (6/9)
• Message Type Octet
– The second octet in a standard L3 message
– When a standard L3 message i...
Standard L3 Messages (7/9)
• Message Type Octet (Cont.)
– When accessing Rel.99 and newer networks 4 3
6
7
5
8
N (SD) or 0...
Standard L3 Messages (8/9)

• Transaction identifier (TI in PS NAS Msg.; TIO in CS NAS Msg.)

– Bits 5 to 8 of octet 1 of ...
Standard L3 Messages (9/9)
• Sub-Protocol Discriminator (SPD)

CTS: Cordless Telephony System

– Bits 5 to 8 of octet 1 of...
Service State Diagram [6] (1/2)
• Service graph of Call Control entity - MS side
• Three partitions: MO call, call clearin...
Service State Diagram (2/2)
• Service graph of Call Control entity - NW side
• Three partitions: MO call, call clearing, M...
Primitive: inter-layer info. in one node
Message: inter-node info.

Service Arrow Diagram (1/3)-MO call setup (Successful ...
Service Arrow Diagram (2/3)-MT call setup (Successful case)
Mobile Station

CC

Network

Setup Request from NW
MM

RR

RR
...
Service Arrow Diagram (3/3)-MO, call and channel release (Successful case)
Mobile Station

CC

Network

MM

L2

L2

RR

RR...
System Log (1/5)
• Environment - QXDM Prof.
>> Item type: Long packets (OTA)
>> Filter/Register on target for items: CC, M...
Presence
M: Mandatory
C: Conditional
O: Optional

System Log (2/5)

• Messages for CS CC [2] in Ex.1
– SETUP message conte...
System Log (3/5)
• Messages for CS CC in Ex.1 (Cont.)
– CC/Call Proceeding (NW to MS)

– CC/Facility (NW to MS)
System Log (4/5)
• Messages for CS CC in Ex.1 (Cont.)
– CC/Alerting (NW to MS)

– CC/Connect (NW to MS)

– CC/Connect Ackn...
System Log (5/5)
• Messages for CS CC in Ex.1 (Cont.)
– CC/Disconnect (MS to NW)

– CC/Release (NW to MS)

– CC/Release Co...
References
• [1] 3GPP TS 25.301 V11.0.0 (2012-09) - 3GPP TSG RAN; Radio Interface
Protocol Architecture (Rel.11)
• [2] 3GP...
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Elementary procedures for Circuit-Switched (CS) Call Control (CC) in 3GPP

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Elementary procedures for Circuit-Switched (CS) Call Control (CC) in 3GPP

  1. 1. Elementary Procedures for CircuitSwitched (CS) Call Control (CC) in 3GPP Presented by Louis K. H. Kuo
  2. 2. Outline • • • • • • • Introduction of Related Backgrounds Overview on Call Control Standard L3 Messages Service State Diagram Service Arrow Diagram System Log References
  3. 3. Introduction of Related Backgrounds (1/2) • The radio interface is layered into three protocol layers [1]: – the physical layer (L1); – the data link layer (L2); – the network layer (L3). U-plane • Layer 2 is split into following sublayers: C-plane – Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP) and Broadcast/Multicast Control (BMC). • PDCP and BMC exist in the U-plane only. • Layer 3 and RLC are divided into Control (C-) and User (U-) planes. • In the C-plane, Layer 3 is partitioned into sublayers (e.g., CC, MM). – Access Stratum (AS): from RRC (Radio Resource Control) to L1 – Non-Access Stratum (NAS): AS and from NAS to the NAS of Mobility Management Entity (MME)
  4. 4. Introduction of Related Backgrounds (1/2) • Radio Interface Protocol Architecture (Service Access Points (SAPs) are marked by circles.) • “Logical” SAPs GC – P2P Communication GC • Between RRC and RLC Nt DC UuS boundary U-plane information C-plane signalling L3 control Radio Bearers control control control control RRC PDCP PDCP L2/PDCP BMC • The Service provided by L2 – Radio Bearer – Signaling Radio Bearers DC Duplication avoidance • Three Types of SAPs in RLC – Acknowledged Mode (AM) – Unacknowledged Mode (UM) – Transparent Mode (TM) Nt RLC RLC RLC L2/BMC L2/RLC RLC RLC RLC RLC RLC Logical Channels MAC L2/MAC Transport Channels PHY L1
  5. 5. Overview on Call Control (1/4) • Call Control (CC) Protocol [2] or Call Control Function (CCF) – One of the protocols of the Connection Management (CM) sublayer • Each CC entity is independent from each other and shall communicate with the correspondent peer entity using its own MM connection. – The present document describes the call control protocol only with regard to two peer entities. • Certain sequences of actions of the two peer entities compose "elementary procedures“. – These elementary procedures may be grouped into the following classes: • • • • call establishment procedures; call clearing procedures; call information procedures; miscellaneous procedures.
  6. 6. Overview on Call Control (2/4) • Three Basic Types of Calls – MO Call • The terms "mobile originating" or "mobile originated" are used to describe a call initiated by the mobile station (MS). – MT Call • The terms "mobile terminating" or "mobile terminated" are used to describe a call initiated by the network (NW). – NW Initialed MO Call [3] • A feature allows the NW to ask the MS to establish a MO connection. • The serving PLMN provides the MS with the necessary information which is used by the MS to establish the connection. • It is mandatory for CCBS ME and is used in the case of a CCBS recall. – Completion of Calls to Busy Subscriber (CCBS) [4]: CCBS is evoked when a called party is busy, this supplementary service (SS) enables the calling party to be connected to a called party
  7. 7. Overview on Call Control (3/4) • Example [5]: To make a phone call. – From MOC to PTC; from POC to MTC • Protocol Architecture [6] – Eight defined architectures – Example: A MS supporting the PS mode of operation UMTS service RABM: RAB Manager REG: REGister SM: Session Management MN: Mobile Network SMS: Short Message Service GSMS: GPRS SMS SS: Supplementary Services PDP: Packet Data Protocol TI: Transaction ID MM: Mobility Management GMM: GPRS MM PD: Protocol Discriminator RABn-SAP MNCC-SAP MNSMS-SAP SMREG-SAP CM MNSS-SAP RABM RAB Entity RAB 1 Entity RAB 2 Entity n RABMSM-SAP SM RAB Control GSMS PDP TI CC TI GMMREG PMMSMS GMMSMSGMMSM- -SAP -SAP SAP SAP SS TI TI MMSMSSAP MMCC-SAP GMMSS2SAP TI GMMSSSAP MMSSSAP MM-sublayer MM GMM GMMRABM-SAP • NAS • MS side RAB1-SAP RAB2-SAP PDCP1-SAP PDCP2-SAP PDCPn-SAP RABMAS-SAP GMM coord MM coord PD PD RR-SAP GMMAS-SAP Access Stratum sublayer PDCP BMC RRC
  8. 8. Overview on Call Control (4/4) • The CC service class consists of the following services [6]: – MS side • • • • • MO and MT call establishment for normal calls; MO call establishment for emergency calls; call maintaining; call termination; call related SS Support. – NW side • • • • call establishment; call maintaining; call termination; call related SS support. • Three matrices to understand CC protocol – L3 massage structure, service state diagram, and service arrow diagram
  9. 9. Standard L3 Messages (1/9) • A standard L3 message [6] – (1) Imperative part Example: General message organization • A header • The rest of imperative part – (2) Non-imperative part – (Note: Both the non-header part of the imperative part and the non-imperative part are composed of successive parts referred as standard Information Elements (IEs).) • A standard IE may have the following parts, in that order: – an Information Element Identifier (IEI); – a Length Indicator (LI); – a value part.
  10. 10. Standard L3 Messages (2/9) • A standard IE has one of the formats as follows. – LV-E and TLV-E are used for EPS Mobility Management (EMM) and EPS Session Management (ESM) only. • Seven types of standard IEs are defined: – format V or TV with value part consisting of 1/2 octet; – format T with value part consisting of 0 octets; – format V or TV with value part that has fixed length of at least one octet; – format LV or TLV with value part consisting of zero, one or more octets; – format LV-E or TLV-E with value part consisting of zero, one or more octets and a maximum of 65535 octets. This category is used in EPS only.
  11. 11. Standard L3 Messages (3/9) • Example: Type 4 IE of format TLV – A type 4 standard IE has format LV or TLV. Its LI precedes the value part, which consists of zero, one, or more octets; if present, its IEI has one octet length and precedes the LI. Example: General message organization • The header of a standard L3 message is composed of two octets, and structured in three main parts. [6] – The Protocol Discriminator (PD) (1/2 octet) – A message type octet – A half octet used in some cases as Transaction Identifier (TI), in some other cases as a subprotocol discriminator, and called skip indicator otherwise.
  12. 12. Standard L3 Messages (4/9) • For the EPS protocols (EMM and ESM), a standard L3 message can be either a plain NAS message or a security protected NAS message: – A plain NAS message • which is composed of two or three octets, and structured in four main parts. – A PD (1/2 octet) – A half octet used in some cases as security header type and in other cases as an EPS bearer identity (1/2 octet) – A message type octet – One octet included in some cases and used as a Procedure Transaction Identity (PTI) – A secure protected message • which is composed of six octets, and structured in four main parts. – – – – The PD (1/2 octet) A half octet used as security header type A message authentication code of four octets A sequence number of one octet • This header is followed by a complete plain NAS message (i.e. including the header of this plain NAS message).
  13. 13. Standard L3 Messages (5/9) • Protocol Discriminator (PD) (Note that the following contents focus on the standard L3 message which is not for the usage of EPS.) – Bits 1 to 4 of the first octet of a standard L3 message – The PD identifies which the standard L3 message belongs. – For future evolution to an extension mechanism • The use of protocol discriminators with one octet length, where bits 4 to 1 are coded as 1 1 1 0. – Messages of such protocols may be not standard L3 messages.
  14. 14. Standard L3 Messages (6/9) • Message Type Octet – The second octet in a standard L3 message – When a standard L3 message is expected, • a message is less than 16 bit long, then this message shall be ignored. – When accessing Rel.98 and older networks, GCC: Group CC BCC: Broadcast CC • Bit 8 is encoded as "0“ LCS: Location Services – Further, value "1" is reserved for possible future use as an extension bit. – If “1” is detected, a protocol entity shall diagnose a "message not defined for the PD" error and treat the message accordingly. • Bit 7 – For RR messages including MM, CC, SS, GCC, BCC and LCS, » bit 7 is used for send sequence number. – For all other standard L3 messages (i.e. the protocols other than MM, CC, SS, GCC, BCC and LCS), » bit 7 is set to a default value. 8 0 7 N (SD) or 0 6 5 4 3 Message type 2 1 8 octet 1 7 6 5 4 3 Message type 2 1 octet 1
  15. 15. Standard L3 Messages (7/9) • Message Type Octet (Cont.) – When accessing Rel.99 and newer networks 4 3 6 7 5 8 N (SD) or 0 Message type – For MM, CC, and SS, • bits 7 and 8 are used for send sequence number – For GCC, BCC, and LCS, 8 0 7 6 N (SD) or 0 • only bit 7 is used for send sequence number 6 7 8 • and bit 8 is set to the default value. 5 4 1 2 octet 1 2 3 1 octet 1 Message type 5 4 3 2 1 Message type – For all other standard layer 3 messages, • Non-RR messages – bits 7 and 8 are set to the default value. (The default values are both 0.) – Exception: For SM protocol, bit 7 is set to 1. • RR messages [7] – bit 8 is set to the default value. (No default value for bit 7) • EPS EMM: EPS Mobility Management ESM: EPS Session Management – bit 7 is set to 1 while bit 8 is 0 for the EMM and 1 for the ESM. octet 1
  16. 16. Standard L3 Messages (8/9) • Transaction identifier (TI in PS NAS Msg.; TIO in CS NAS Msg.) – Bits 5 to 8 of octet 1 of a standard L3 message – The TI allows to distinguish up to 16 bi-directional messages flows for a given PD and a given SAP. • Such a message flow is called a transaction. – An extension mechanism is also defined. • which allows to distinguish up to 256 bi-directional messages flows for a given PD and a given SAP. • which shall not be used unless explicitly stated in the core spec. – TI flag • 0: The message is sent from the side that originates the TI. • 1: The message is sent to the side that originates the TI. – TIO (Bits 7 to 5 in octet 1) – TIE (Bit 7 to 1 in octet 2)
  17. 17. Standard L3 Messages (9/9) • Sub-Protocol Discriminator (SPD) CTS: Cordless Telephony System – Bits 5 to 8 of octet 1 of a standard L3 message – which allows to identify between protocols inside one sublayer. • Skip indicator – – – – Bits 5 to 8 of octet 1 of a standard L3 message The content of skip indicator depends on the protocol and the SAP. The use of this half-octet is consistent for a given PD and SAP. Unless been specified in the protocol, the skip indicator IE is a spare field.
  18. 18. Service State Diagram [6] (1/2) • Service graph of Call Control entity - MS side • Three partitions: MO call, call clearing, MT call
  19. 19. Service State Diagram (2/2) • Service graph of Call Control entity - NW side • Three partitions: MO call, call clearing, MT call
  20. 20. Primitive: inter-layer info. in one node Message: inter-node info. Service Arrow Diagram (1/3)-MO call setup (Successful case) Setup Request from MS Mobile Station CC MNCC-SETUP-REQ MM MMCC-EST-REQ RR RR-EST-REQ (CM SERV REQ) L2 L2 RR MM Network CC DL-RANDOM-ACC-REQ/IND (CHANN REQ) DL-UNIT-DATA-IND/REQ(IMM ASS) DL-ASS-REQ RR-EST-CNF SABM (CM SERV REQ) DL-EST-CNF DL-EST-IND UA (CM SERV REQ) RR-EST-IND (CM SERV REQ) AUTH REQ Authentication & Ciphering AUTH RES CIPH MODE CMD MMCC-EST-CNF RR-SYNC-IND (ciph) CIPH MODE COM RR-SYNC-REQ (ciph) RR-SYNC-CNF (ciph) MMCC-EST-IND (SETUP) SETUP MNCC-CALLPROC-IND CALL PROC MNCC-CALLPROC-REQ ASSIGN CMD MMCC-SYNC-IND (res ass) MNCC-ALERT-IND MNCC-SETUP-CNF RR-SYNK-IND (res ass) RR-SYNC-REQ (res ass) ASSIGN COM RR-SYNC-CNF (res ass) ALERT CONNECT CONN ACK MNCC-SETUP-IND MMCC-SYNC-REQ (res ass) MMCC-SYNC-CNF (res ass) MNCC-ALERT-REQ MNCC-SETUP-RSP MNCC-SETUPCOMPL-IND MO Call Setup DATA FLOW
  21. 21. Service Arrow Diagram (2/3)-MT call setup (Successful case) Mobile Station CC Network Setup Request from NW MM RR RR L2 L2 DL-UNIT-DATA-IND/REQ (PAG REQ) MM CC MMCC-SETUP-REQ RR-EST-REQ (mob id) MMCC-EST-REQ (mob id) DL-RANDOM-ACC-REQ/IND (CHANN REQ) DL-UNIT-DATA-IND/REQ (IMM ASS) DL-EST-REQ RR-EST-IND DL-EST-CONF SABM (PAG RES) DL-EST-IND RR-EST-CNF UA (PAG RES) AUTH REQ Authentication & Ciphering AUTH RES CIPH MODE CMD RR-SYNC-IND (ciph) MNCC-SETUPIND RR-SYNC-REQ (res ass) CIPH MODE COM RR-SYNC-CNF (res ass) MMCC-EST-CNF SETUP MMCC-EST-IND (SETUP) CALL CONF MNCC-CALLCONF-REQ ASSIGN CMD MMCC-SYNC-IND (res ass) RR-SYNC-IND (res ass) ASSIGN COM MNCC-ALERTREQ ALERT MNCC-SETUPRES CONNECT MNCC-SETUPCOMPL-IND CONN ACK MT Call Setup DATA FLOW MNCC-CALLCONF-IND RR-SYNC-REQ (res ass) RR-SYNC-CNF (res ass) MMCC-SYNC-REQ (res ass) MMCC-SYNC-CNF (res ass) MNCC-ALERT-IND MNCC-SETUP-CNF MNCC-SETUPCOMPL-REQ
  22. 22. Service Arrow Diagram (3/3)-MO, call and channel release (Successful case) Mobile Station CC Network MM L2 L2 RR RR MM CC DATA FLOW Disconnect DISCONNECT MNCC-DISC-REQ MNCC-DISC-IND MNCC-REL-IND RELEASE MNCC-REL-REQ RELEASE COM Release MNCC-REL-CNF MMCC-REL-REQ CHANN REL RR-REL-IND DL-REL-REQ DL-REL-CNF Channel Release DISC UA RR-REL-REQ DL-REL-IND MMCC-REL-REQ
  23. 23. System Log (1/5) • Environment - QXDM Prof. >> Item type: Long packets (OTA) >> Filter/Register on target for items: CC, MM, GSM RRM – (Ex.1) The MO call is successful and disconnects by calling user. – (Ex.2) The MT call is successful and disconnects by the calling user.
  24. 24. Presence M: Mandatory C: Conditional O: Optional System Log (2/5) • Messages for CS CC [2] in Ex.1 – SETUP message content (MS to NW) • Transaction ID (trans_id_or_skip_ind = 0x0) – TI values are assigned by the side of the interface initiating a transaction . • Protocol discriminator (prot_disc = 0x3) – Call control; call related SS messages • Message type (msg_type = 0x5) – Call establishment message – SETUP • Bearer capability 1 (bearer_cap_1_incl = 0x1) • Called party BCD number (called_party_bcd_incl = 0x1)
  25. 25. System Log (3/5) • Messages for CS CC in Ex.1 (Cont.) – CC/Call Proceeding (NW to MS) – CC/Facility (NW to MS)
  26. 26. System Log (4/5) • Messages for CS CC in Ex.1 (Cont.) – CC/Alerting (NW to MS) – CC/Connect (NW to MS) – CC/Connect Acknowledge (MS to NW)
  27. 27. System Log (5/5) • Messages for CS CC in Ex.1 (Cont.) – CC/Disconnect (MS to NW) – CC/Release (NW to MS) – CC/Release Complete (MS to NW)
  28. 28. References • [1] 3GPP TS 25.301 V11.0.0 (2012-09) - 3GPP TSG RAN; Radio Interface Protocol Architecture (Rel.11) • [2] 3GPP TS 24.008 V12.3.0 (2013-09) - 3GPP TSG CT; Mobile Radio Interface Layer 3 Spec.; CN protocols; Stage 3 (Re.12) • [3] ETSI TS 100 906 v7.0.1 (1999-07) - Digital Cellular Telecom. System (Phase2+); MS Features (GSM 02.07) ver. 7.0.1 (Rel. 98) • [4] Asterisk 1.4/Call Completion on Busy Subscriber (CCBS) • [5] WCDMA/UMTS第三代無線通訊系統(1)--核心網路架構介紹 • [6] 3GPP TS 24.007 V12.0.0 (2013-06) - 3GPP TSG CT; Mobile Radio Interface Signalling Layer 3; General Aspects (Rel.12) • [7] 3GPP TS 44.018 V12.0.0 (2013-09) – 3GPP TSG GERAN; Mobile Radio Interface Layer 3 Spec.; RRC protocol (Rel.12)

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