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RRC/NAS Message for IMS
For any communication to work, both party (UE and Network in this case) must have a certain set of capability (hardware, software, protocol capability) that is required for the communication. Therefore, before any one party initiate/request communication, they must know the capability of the other party. In most case, each party exchange these capability information at some points. There are couple of points where these information exchange happens as listed below. i) sometime in registration to radio network ii) sometime in application registration iii) sometime at the initial phase of communication setup I will talk mostly about the item i) in this page and you will see some examples in other pages for item ii) and item iii). (e.g, IMS Message example - REGISTER, SDP, Precondition etc)
Attach Request - Domain Specification
If a UE support VoLTE, UE would set its capability in Attach Request as shown below (Highlighted in Red).
Voice domain preference and UE's usage setting Element ID: 0x5d Length: 1 0000 0... = Spare bit(s): 0 .... .1.. = UE's usage setting: Data centric .... ..00 = Voice domain preference for E-UTRAN: IMS PS voice preferred, CS Voice as secondary
There are multiple options that can be set for these IE (Information Elements) as shown below. (If UE sets these IEs to be 'Voice Centric' and 'CS Voice Only', it is highly likely that UE does not support VoLTE or VoLTE functionality is temperarily unavailable.
Refer to
Attach Accept - Network Feature
EPS network feature support Element ID: 0x64 Length: 1 00.. .... = Spare bit(s): 0x00 ..0. .... = ESRPS: network does not support use of EXTENDED SERVICE REQUEST to request for packet services ...0 0... = CS-LCS: no information about support of location services via CS domain is available (0) .... .0.. = EPC-LCS: location services via EPC not supported .... ..0. = EMC BS: emergency bearer services in S1 mode not supported .... ...1 = IMS VoPS: IMS voice over PS session in S1 mode supported
Refer to
Following is an example of FGI(featureGroupIndicator) in UE Capability Information and I highlighted some of the bits that my influence IMS application, especially VoLTE. This is just general idea.. it does not mean that all the highlited bits should be enabled to VoLTE operation. It doesn't mean either that the highlighted bits are the only FGI bits for VoLTE operation. There can be a lot of variations depending on Carrier's requirement.
featureGroupIndicators: 7f0ffc80 [bit length 32, 0111 1111 0000 1111 1111 1100 1000 0000 decimal value 2131754112] 0... .... = Indicator 1: Intra-subframe freq hopping for PUSCH scheduled by UL grant; DCI format 3a; PDSCH transmission mode 5; Aperiodic CQI/PMI/RI report on PUSCH: Mode 2-0 & 2-2 - Not supported .1.. .... = Indicator 2: Simultaneous CQI & ACK/NACK on PUCCH (format 2a/2b); Absolute TPC command for PUSCH; Resource alloc type 1 for PDSCH; Periodic CQI/PMI/RI report on PUCCH: Mode 2-0 & 2-1 - Supported ..1. .... = Indicator 3: 5bit RLC UM SN; 7bit PDCP SN - Supported ...1 .... = Indicator 4: Short DRX cycle - Supported .... 1... = Indicator 5: Long DRX cycle; DRX command MAC control element - Supported .... .1.. = Indicator 6: Prioritised bit rate - Supported .... ..1. = Indicator 7: RLC UM - Supported .... ...1 = Indicator 8: EUTRA RRC_CONNECTED to UTRA CELL_DCH PS handover - Supported 0... .... = Indicator 9: EUTRA RRC_CONNECTED to GERAN GSM_Dedicated handover - Not Supported .0.. .... = Indicator 10: EUTRA RRC_CONNECTED to GERAN (Packet_) Idle by Cell Change Order; EUTRA RRC_CONNECTED to GERAN (Packet_) Idle by Cell Change Order with NACC - Not supported ..0. .... = Indicator 11: EUTRA RRC_CONNECTED to CDMA2000 1xRTT CS Active handover - Not supported ...0 .... = Indicator 12: EUTRA RRC_CONNECTED to CDMA2000 HRPD Active handover - Not supported .... 1... = Indicator 13: Inter-frequency handover (within FDD or TDD) - Supported .... .1.. = Indicator 14: Measurement reporting event: Event A4 - Neighbour > threshold; Measurement reporting event: Event A5 - Serving < threshold1 & Neighbour > threshold2 - Supported .... ..1. = Indicator 15: Measurement reporting event: Event B1 - Neighbour > threshold - Supported .... ...1 = Indicator 16: non-ANR related periodical measurement reporting - Supported 1... .... = Indicator 17: ANR related intra-frequency measurement reporting events - Supported .1.. .... = Indicator 18: ANR related inter-frequency measurement reporting events - Supported ..1. .... = Indicator 19: ANR related inter-RAT measurement reporting events - Supported ...1 .... = Indicator 20: SRB1 and SRB2 for DCCH + 8x AM DRB; SRB1 and SRB2 for DCCH + 5x AM DRB + 3x UM DRB (if indicator 7 is supported) - Supported .... 1... = Indicator 21: Predefined intra- and inter-subframe frequency hopping for PUSCH with N_sb > 1; Predefined inter-subframe frequency hopping for PUSCH with N_sb > 1 - Supported .... .1.. = Indicator 22: UTRAN measurements, reporting and measurement reporting event B2 in E-UTRA connected mode - Supported .... ..0. = Indicator 23: GERAN measurements, reporting and measurement reporting event B2 in E-UTRA connected mode - Not supported .... ...0 = Indicator 24: 1xRTT measurements, reporting and measurement reporting event B2 in E-UTRA connected mode - Not supported 1... .... = Indicator 25: Inter-frequency measurements and reporting in E-UTRA connected mode - Supported .0.. .... = Indicator 26: HRPD measurements, reporting and measurement reporting event B2 in E-UTRA connected mode - Not supported ..0. .... = Indicator 27: EUTRA RRC_CONNECTED to UTRA CELL_DCH CS handover - Not supported ...0 .... = Indicator 28: TTI bundling - Not supported .... 0... = Indicator 29: Semi-Persistent Scheduling - Not supported .... .0.. = Indicator 30: Handover between FDD and TDD - Not supported .... ..0. = Indicator 31: Undefined - Not supported .... ...0 = Indicator 32: Undefined - Not supported
PCO in PDN Connectivity Request
When UE wants to get P-CSCF from Network via NAS message, it may ask for CSCF address by setting the request in PCO of PDN Connectivity Request as shown below.
PCO in PDN Connectivity Request (Just for Example) Protocol Configuration Options Element ID: 0x27 Length: 35 [Link direction: MS to network (0)] 1... .... = Ext: 0x01 Configuration Protocol: PPP for use with IP PDP type or IP PDN type (0) Protocol or Container ID: Internet Protocol Control Protocol (0x8021) Length: 0x10 (16) PPP IP Control Protocol Code: Configuration Request (1) Identifier: 0 (0x00) Length: 16 Options: (12 bytes), Primary DNS Server IP Address, Secondary DNS Server IP Address Primary DNS Server IP Address: 0.0.0.0 Type: Primary DNS Server IP Address (129) Length: 6 Primary DNS Address: 0.0.0.0 (0.0.0.0) Secondary DNS Server IP Address: 0.0.0.0 Type: Secondary DNS Server IP Address (131) Length: 6 Secondary DNS Address: 0.0.0.0 (0.0.0.0) Protocol or Container ID: DNS Server IPv4 Address Request (0x000d) Length: 0x00 (0) Protocol or Container ID: DNS Server IPv6 Address Request (0x0003) Length: 0x00 (0) Protocol or Container ID: P-CSCF IPv6 Address Request (0x0001) Length: 0x00 (0) Protocol or Container ID: P-CSCF IPv4 Address Request (0x000c) Length: 0x00 (0) Protocol or Container ID: IP address allocation via NAS signalling (0x000a) Length: 0x00 (0)
PCO in Activate default EPS bearer context request
If UE request CSCF address via PDN Connectivity Request or by Network Operator's requirement, Network can inform UE of CSCF address by PCO in Activate default EPS bearer context request.
PCO in Activate default EPS bearer context request (Just for Example) Protocol Configuration Options Element ID: 0x27 Length: 72 [Link direction: Network to MS (1)] 1... .... = Ext: 0x01 Configuration Protocol: PPP for use with IP PDP type or IP PDN type (0) Protocol or Container ID: Internet Protocol Control Protocol (0x8021) Length: 0x10 (16) PPP IP Control Protocol Code: Configuration Nak (3) Identifier: 0 (0x00) Length: 16 Options: (12 bytes), Primary DNS Server IP Address, Secondary DNS Server IP Address Primary DNS Server IP Address: 192.168.1.2 Type: Primary DNS Server IP Address (129) Length: 6 Primary DNS Address: 192.168.1.2 (192.168.1.2) Secondary DNS Server IP Address: 192.168.1.2 Type: Secondary DNS Server IP Address (131) Length: 6 Secondary DNS Address: 192.168.1.2 (192.168.1.2) Protocol or Container ID: DNS Server IPv4 Address (0x000d) Length: 0x04 (4) IPv4: 192.168.1.2 Protocol or Container ID: DNS Server IPv6 Address (0x0003) Length: 0x10 (16) IPv6: 2001:0:0:1::2 Protocol or Container ID: P-CSCF IPv6 Address (0x0001) Length: 0x10 (16) IPv6: 2001:0:0:1::2 Protocol or Container ID: P-CSCF IPv4 Address (0x000c) Length: 0x04 (4) IPv4: 192.168.1.2
BCCH-DL-SCH-Message message: c1 (0) c1: systemInformationBlockType1 (1) systemInformationBlockType1 cellAccessRelatedInfo plmn-IdentityList: 1 item Item 0 PLMN-IdentityInfo plmn-Identity .... cellReservedForOperatorUse: notReserved (1) trackingAreaCode: 0001 cellIdentity: 00000000 cellBarred: notBarred (1) intraFreqReselection: notAllowed (1) .... ..0. csg-Indication: False cellSelectionInfo q-RxLevMin: -130dBm (-65) p-Max: 23dBm freqBandIndicator: 1 schedulingInfoList: 2 items ... si-WindowLength: ms20 (5) systemInfoValueTag: 0 nonCriticalExtension nonCriticalExtension ims-EmergencySupport-r9: true (0)
SIB2 (Access Control for MMTEL)
BCCH-DL-SCH-Message message: c1 (0) c1: systemInformation (0) systemInformation criticalExtensions: systemInformation-r8 (0) systemInformation-r8 sib-TypeAndInfo: 1 item Item 0 sib-TypeAndInfo item: sib2 (0) sib2 ac-BarringInfo ...1 .... ac-BarringForEmergency: True ac-BarringForMO-Signalling ac-BarringFactor: p00 (0) ac-BarringTime: s4 (0) ac-BarringForSpecialAC: 10000 (bitmap) ac-BarringForMO-Data ac-BarringFactor: p00 (0) ac-BarringTime: s4 (0) ac-BarringForSpecialAC: 00000 (bitmap) .... ssac-BarringForMMTEL-Voice-r9 ac-BarringFactor: p00 (0) ac-BarringTime: s4 (0) ac-BarringForSpecialAC: 00000 (bitmap) ssac-BarringForMMTEL-Video-r9 ac-BarringFactor: p00 (0) ac-BarringTime: s4 (0) ac-BarringForSpecialAC: 00000 (bitmap)
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