|
4G/LTE - SMS |
||
|
SMS with LTE (SG-SMS)
Everybody would know what SMS (Short Messaging Service) is. So I will not talk about what SMS is. The question you are more interested in would be "Is it possible to send SMS in LTE ?" and "How to do it ?". Yes, SMS is possible in LTE and there are two ways to implement SMS in LTE. The ideal solution would be doing SMS using IMS. IMS over LTE is specified to transfer any form of data (e.g, voice, SMS and any other form of multi media data), but the question is when every body (both network implementation and UE implementation) will seamlessly implement this IMS on their network and UE. It seems that they are not implemented fully at least for now. So they thought out a kind of interim solution called SG LTE. (It is like we have CS Fallback as an interim solution before they fully implement voice call over IMS). For the over view of SG SMS, refer to this blog. I found the explanation in the blog is short, practical and easy to understand.
In terms of network Architecture, SG SMS goes through a special interface marked in red below.
Followings are the topics I will deal with in this page.
The implementation logic of SG-SMS is very similar to WCDMA SMS. In WCDMA, we injected the SMS message into a DCCH channel and send it to the destination. It means that we carried the message over a control channel, not over a data channel. SG SMS is also using a similar concept, we send the message over a control channel. One example is as follows (This is for MT SMS case).
i) UE <-- NW : RRC Connection Reconfiguration ii) UE --> NW : RR Connection Reconfiguration Comlete iii) UE <-- NW : dlInformationTransfer (DOWNLINK NAS TRANSPORT : SMS message - CP Data) iv) UE --> NW : ulInformationTransfer (UPLINK NAS TRANSPORT : embedd CP-ACK into this message) v) UE --> NW : ulInformationTransfer (UPLINK NAS TRANSPORT : Delivery Report) vi) UE <-- NW : dlInformationTransfer (DOWNLINK NAS TRANSPORT : CP-ACK)
Actually Step iii) carries a special NAS message called "DOWNLINK NAS TRANSPORT" and this NAS message carries CP Data in it.
c1: dlInformationTransfer (1) dlInformationTransfer rrc-TransactionIdentifier: 0 criticalExtensions: c1 (0) c1: dlInformationTransfer-r8 (0) dlInformationTransfer-r8 dedicatedInfoType: dedicatedInfoNAS (0) dedicatedInfoNAS: 27d1356f030407622809012501000481999999001c040a81... Non-Access-Stratum (NAS)PDU 0010 .... = Security header type: Integrity protected and ciphered (2) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) Message authentication code: 0xd1356f03 Sequence number: 4 0000 .... = Security header type: Plain NAS message, not security protected (0) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) NAS EPS Mobility Management Message Type: Downlink NAS transport (0x62) NAS message container Length: 40 NAS message container content: 09012501000481999999001c040a81214365870900003111... GSM A-I/F DTAP - CP-DATA Protocol Discriminator: SMS messages .... 1001 = Protocol discriminator: SMS messages (0x09) 0... .... = TI flag: allocated by sender .000 .... = TIO: 0 DTAP Short Message Service Message Type: CP-DATA (0x01) CP-User Data Length: 37 RPDU (not displayed) GSM A-I/F RP - RP-DATA (Network to MS) Message Type RP-DATA (Network to MS) RP-Message Reference RP-Message Reference: 0x00 (0) RP-Origination Address - (999999) Length: 4 1... .... = Extension: No Extension .000 .... = Type of number: unknown (0x00) .... 0001 = Numbering plan identification: ISDN/Telephony Numbering (Rec ITU-T E.164) (0x01) BCD Digits: 999999 RP-Destination Address Length: 0 RP-User Data Length: 28 TPDU (not displayed) GSM SMS TPDU (GSM 03.40) SMS-DELIVER 0... .... = TP-RP: TP Reply Path parameter is not set in this SMS SUBMIT/DELIVER .0.. .... = TP-UDHI: The TP UD field contains only the short message ..0. .... = TP-SRI: A status report shall not be returned to the SME .... .1.. = TP-MMS: No more messages are waiting for the MS in this SC .... ..00 = TP-MTI: SMS-DELIVER (0) TP-Originating-Address - (1234567890) Length: 10 address digits 1... .... : No extension .000 .... : Type of number: (0) Unknown .... 0001 : Numbering plan: (1) ISDN/telephone (E.164/E.163) TP-OA Digits: 1234567890 TP-PID: 0 00.. .... : defines formatting for subsequent bits ..0. .... : no telematic interworking, but SME-to-SME protocol ...0 0000 : the SM-AL protocol being used between the SME and the MS (0) TP-DCS: 0 00.. .... = Coding Group Bits: General Data Coding indication (0) Special case, GSM 7 bit default alphabet TP-Service-Centre-Time-Stamp Year 13, Month 11, Day 06 Hour 10, Minutes 05, Seconds 55 Timezone: GMT + 5 hours 0 minutes TP-User-Data-Length: (11) depends on Data-Coding-Scheme TP-User-Data SMS text: mt sms test
Actually Step iv) carries a special NAS message called "UPLINK NAS TRANSPORT" and this NAS message carries CP ACK in it.
c1: ulInformationTransfer (9) ulInformationTransfer criticalExtensions: c1 (0) c1: ulInformationTransfer-r8 (0) ulInformationTransfer-r8 dedicatedInfoType: dedicatedInfoNAS (0) dedicatedInfoNAS: 27602658f6040763028904 Non-Access-Stratum (NAS)PDU 0010 .... = Security header type: Integrity protected and ciphered (2) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) Message authentication code: 0x602658f6 Sequence number: 4 0000 .... = Security header type: Plain NAS message, not security protected (0) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) NAS EPS Mobility Management Message Type: Uplink NAS transport (0x63) NAS message container Length: 2 NAS message container content: 8904 GSM A-I/F DTAP - CP-ACK Protocol Discriminator: SMS messages .... 1001 = Protocol discriminator: SMS messages (0x09) 1... .... = TI flag: allocated by receiver .000 .... = TIO: 0 DTAP Short Message Service Message Type: CP-ACK (0x04)
Step v) can be an optional. This is for delivery report.
c1: ulInformationTransfer (9) ulInformationTransfer criticalExtensions: c1 (0) c1: ulInformationTransfer-r8 (0) ulInformationTransfer-r8 dedicatedInfoType: dedicatedInfoNAS (0) dedicatedInfoNAS: 27608e1cd405076309890106020041020000 Non-Access-Stratum (NAS)PDU 0010 .... = Security header type: Integrity protected and ciphered (2) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) Message authentication code: 0x608e1cd4 Sequence number: 5 0000 .... = Security header type: Plain NAS message, not security protected (0) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) NAS EPS Mobility Management Message Type: Uplink NAS transport (0x63) NAS message container Length: 9 NAS message container content: 890106020041020000 GSM A-I/F DTAP - CP-DATA Protocol Discriminator: SMS messages .... 1001 = Protocol discriminator: SMS messages (0x09) 1... .... = TI flag: allocated by receiver .000 .... = TIO: 0 DTAP Short Message Service Message Type: CP-DATA (0x01) CP-User Data Length: 6 RPDU (not displayed) GSM A-I/F RP - RP-ACK (MS to Network) Message Type RP-ACK (MS to Network) RP-Message Reference RP-Message Reference: 0x00 (0) RP-User Data Element ID: 0x41 Length: 2 TPDU (not displayed) GSM SMS TPDU (GSM 03.40) SMS-DELIVER REPORT .0.. .... = TP-UDHI: The TP UD field contains only the short message .... .0.. = TP-MMS: More messages are waiting for the MS in this SC .... ..00 = TP-MTI: SMS-DELIVER REPORT (0) TP-Parameter-Indicator 0... .... : No extension .000 0... : Reserved .... .0.. : TP-UDL not present .... ..0. : TP-DCS not present .... ...0 : TP-PID not present
Step vi) is the CP-ACK for Step v)
c1: dlInformationTransfer (1) dlInformationTransfer rrc-TransactionIdentifier: 0 criticalExtensions: c1 (0) c1: dlInformationTransfer-r8 (0) dlInformationTransfer-r8 dedicatedInfoType: dedicatedInfoNAS (0) dedicatedInfoNAS: 27b0d94c40050762020904 Non-Access-Stratum (NAS)PDU 0010 .... = Security header type: Integrity protected and ciphered (2) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) Message authentication code: 0xb0d94c40 Sequence number: 5 0000 .... = Security header type: Plain NAS message, not security protected (0) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) NAS EPS Mobility Management Message Type: Downlink NAS transport (0x62) NAS message container Length: 2 NAS message container content: 0904 GSM A-I/F DTAP - CP-ACK Protocol Discriminator: SMS messages .... 1001 = Protocol discriminator: SMS messages (0x09) 0... .... = TI flag: allocated by sender .000 .... = TIO: 0 DTAP Short Message Service Message Type: CP-ACK (0x04)
Addional Example - International Number / Message Class / Message Time Stamp
These information is specified in specific information elements in CP-DATA as shown in color below. Red indicate 'International Number Type', Green indicates 'Message Class' and Blue indicate 'Message Time Stamp'
DLT: 147, Payload: lte-rrc.dl.dcch (LTE Radio Resource Control (RRC) protocol) DL-DCCH-Message message: c1 (0) c1: dlInformationTransfer (1) dlInformationTransfer rrc-TransactionIdentifier: 0 criticalExtensions: c1 (0) c1: dlInformationTransfer-r8 (0) dlInformationTransfer-r8 dedicatedInfoType: dedicatedInfoNAS (0) dedicatedInfoNAS: 27d05511ee0507622c090129010004819999990020a40a90... Non-Access-Stratum (NAS)PDU 0010 .... = Security header type: Integrity protected and ciphered (2) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) Message authentication code: 0xd05511ee Sequence number: 5 0000 .... = Security header type: Plain NAS message, not security protected (0) .... 0111 = Protocol discriminator: EPS mobility management messages (0x07) NAS EPS Mobility Management Message Type: Downlink NAS transport (0x62) NAS message container Length: 44 NAS message container content: GSM A-I/F DTAP - CP-DATA Protocol Discriminator: SMS messages .... 1001 = Protocol discriminator: SMS messages (0x09) 0... .... = TI flag: allocated by sender .000 .... = TIO: 0 DTAP Short Message Service Message Type: CP-DATA (0x01) CP-User Data Length: 41 RPDU (not displayed) GSM A-I/F RP - RP-DATA (Network to MS) Message Type RP-DATA (Network to MS) RP-Message Reference RP-Message Reference: 0x00 (0) RP-Originator Address - (999999) Length: 4 1... .... = Extension: No Extension .000 .... = Type of number: unknown (0x00) .... 0001 = Numbering plan identification: ISDN/Telephony Numbering (ITU-T Rec. E.164 / ITU-T Rec. E.163) (0x01) BCD Digits: 999999 RP-Destination Address Length: 0 RP-User Data Length: 32 TPDU (not displayed) GSM SMS TPDU (GSM 03.40) SMS-DELIVER 1... .... = TP-RP: TP Reply Path parameter is set in this SMS SUBMIT/DELIVER .0.. .... = TP-UDHI: The TP UD field contains only the short message ..1. .... = TP-SRI: A status report shall be returned to the SME .... .1.. = TP-MMS: No more messages are waiting for the MS in this SC .... ..00 = TP-MTI: SMS-DELIVER (0) TP-Originating-Address - (1234567890) Length: 10 address digits 1... .... : No extension .001 .... : Type of number: (1) International .... 0000 : Numbering plan: (0) Unknown TP-OA Digits: 1234567890 TP-PID: 0 00.. .... : defines formatting for subsequent bits ..0. .... : no telematic interworking, but SME-to-SME protocol ...0 0000 : the SM-AL protocol being used between the SME and the MS (0) TP-DCS: 17 00.. .... = Coding Group Bits: General Data Coding indication (0) 00.. .... : General Data Coding indication ..0. .... : Text is not compressed ...1 .... : Message class is defined below .... 00.. : Character set: GSM 7 bit default alphabet .... ..01 : Message Class: Class 1 Default meaning: ME-specific TP-Service-Centre-Time-Stamp Year 15, Month 04, Day 07 Hour 13, Minutes 41, Seconds 28 Timezone: GMT + 5 hours 0 minutes TP-User-Data-Length: (16) depends on Data-Coding-Scheme TP-User-Data SMS text: MT SMS - Class1
For further information on these special NAS TRANSPORT Message, you can refer to 24.301
[TS 24.301, clause 8.2.4.13 - Voice domain preference and UE's usage setting] This IE shall be included in WB-S1 mode if the UE supports: - CS fallback and SMS over SGs; or - if the UE is configured to support IMS voice, but does not support 1xCS fallback.
NOTE : If this IE is not configured in the NAS message from UE, Network may not allow SG over SMS. Following is an example of the NAS message from UE configuring this IE. ESM message container: Protocol discriminator = 0x2 (EPS Session Management) EPS bearer identity = 0 Procedure transaction identity = 94 Message type = 0xd0 (PDN connectivity request) Request type = 1 (initial request) ... Last visited registered TAI: ... Voice domain preference and UE's usage setting = 0x07 (IMS PS voice preferred, CS Voice as secondary, Data centric) ...
[TS 24.301, clause 5.6.3.1] The purpose of the transport of NAS messages procedure is to carry SMS messages in an encapsulated form between the MME and the UE. The procedure may be initiated by the UE or the network and can only be used when the UE is attached for EPS services and IMSI attached for non-EPS services and is in EMM-CONNECTED mode.
[TS 24.301, clause 5.6.3.3] The network initiates the procedure by sending a DOWNLINK NAS TRANSPORT message. When receiving the DOWNLINK NAS TRANSPORT message, the EMM entity in the UE shall forward the contents of the NAS message container IE to the SMS entity.
[TS 24.301, clause 9.9.3.22] This information element is used to encapsulate the SMS messages transferred between the UE and the network. The NAS message container information element is coded as shown in figure 9.9.3.22.1 and table 9.9.3.22.1. The NAS message container is a type 4 information element with a minimum length of 4 octets and a maximum length of 253 octets.
|
||
