Saturday, November 5, 2011

Paging

Direction: E-UTRAN => UE
Signalling Radio Bearer: N/A
RLC Mode: TM
Logical Channel: PCCH
Transport Channel: PCH

E-UTRAN initiates the paging procedure by transmitting a PAGING message at the UE's paging occasion as specified in TS 36.304. E-UTRAN may address multiple UEs within a PAGING message by including one PagingRecord for each UE

In LTE, there is only one type of PAGING where as in the case of 3G-system, Paging Type1 and Paging Type2 are defined

The PAGING message may be used to inform UEs in RRC_IDLE and RRC_CONNECTED about a system information change. If the UE receives a PAGING message including the systemInfoModification IE, it knows that the system information will change at the next modification period boundary. The UE, if the systemInfoModification is included, should re-acquire the required system information using the system information acquisition procedure

The PAGING message may also be used to inform ETWS (Earthquake and Tsunami Warning System) capable UEs in RRC_IDLE and UEs in RRC_CONNECTED about presence of an ETWS primary notification and/or ETWS secondary notification. An ETWS capable UE should re-acquire SIB10/SIB11 immediately if the etws-Indication is included in the PAGING message

The PAGING message may also be used to inform CMAS (Commercial Mobile Alert System) capable UEs in RRC_IDLE and UEs in RRC_CONNECTED about presence of one or more CMAS notifications. A CMAS capable UE should re-acquire SIB12 immediately if the cmas-Indication is included in the PAGING message

The UE in RRC_IDLE validates each of the PagingRecord, if any, included in the PAGING message. If the ue-Identity included in the PagingRecord  matches one of the UE identities allocated by upper layers, the ue-Identity and the cn-Domain are forwarded to the upper layers

IEs in PAGING message:
CN-Domain: Indicates the origin of paging (ps or cs)
UE-Identity: Provides the NAS identity of the UE that is being paged (S-TMSI or IMSI)
SystemInfoModification: If present, this IE indicates a BCCH modification other than SIB10, SIB11 and SIB12
etws-Indication: If present, this IE indicates an ETWS primary notification and/or ETWS secondary notification
cmas-Indication: If present, this IE indicates a CMAS notification

Example1: PAGING message with only one paging record


 Example2: PAGING message with notification of BCCH modification 

26 comments:

  1. can we combine the systemInfoModifcation is TURE for all UEs and Paging record for one specific UE in one Paging Message?

    ReplyDelete
  2. Hi,

    It certainly, is possible since the IE SystemInformationModification is not for any specific UE (common for all the UEs), the E-UTRAN could include some paging records + SystemInformationModification (set to true)

    Kumar

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  3. Appreciable for the quick reply.
    But small corrections may needed in above content like SIB10 and SIB11 for ETWS and SIB12 for CMAS.

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  4. Hi,

    Thanks a lot for catching this up. It was a typo! I corrected it now

    Thanks again!
    Kumar

    ReplyDelete
  5. Will Network send the Paging message with SystemInformationModification in case ETWS(SIB10/SIB11) transmission has stopped, to indicate the chnage in Scheduling Info in SIB1 (i.e. rmeoval of SIB10 and 11 from Scheduling Info List).

    ReplyDelete
  6. Hi,

    I think it works like this: Once the UE finds that there is ETWS indication present, then it would acquire SIB10/11 for once. If the UE receives the paging once more then would acquire once more and so on.

    The SYstem Information modification can't be used SIB10/11/12 as mentioned in the specification (SystemInfoModification: If present, this IE indicates a BCCH modification other than SIB10, SIB11 and SIB12)

    please correct me if I am wrong

    ReplyDelete
    Replies
    1. Thanks Kumar for your reply. It's clear that netwrok will not send the SystemInfoModification to indicate the SIB10/11 presence/absence.

      Acutally what I want to know is when Netwrok stops the ETWS, will it send the SystemInfoModification to indicate the Modified SIB1 due to removal of SIB10/11 from Scheduling Info List in SIB1.
      Note: Actual change in this case will be in SIB1 (i.e. removal of SIB10/11 from its Scheduling Info parameter) but it will due to ETWS related Information. So I am not sure Will eNodeB send the SystemInfoModification (Paging) to indicate this change.

      Delete
  7. Hello Kumar
    Transport Channel: DL-SCH
    I think it should be PCH instead of DL-SCH.
    What is your views?

    ReplyDelete
    Replies
    1. Hello Kshirod,
      Mr Kumar is right.... in LTE for Paging
      Logical channel---PCCH
      Transport channel--PCH
      Physical channel---PDSCH
      ...... In LTE for SIB
      Logical Channel-----BCCH
      Transport Channe-- DL_SCH
      Transport Channel--DL_SCH
      Transport Channel DL-SCH is used in SIB messages

      Delete
  8. Hi,

    It was a typo (copy paste mistake). I will correct it!

    Thanks
    Kumar

    ReplyDelete
  9. Hi All,

    Can any body tell me the PF and PO for SI messages modification not for ue specific.


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  10. Hi,

    If UE can read change of system information(SystemInfoModification) with the help of TAG value then what is need of paging?What is different scanarios in which UE have to read paging message and
    check the tag value?why network send both change in tag value and paging..while UE can update with only one method?

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  11. Hi Kumar,

    If eNB must send Paging for SI, so how much times eNb must send these message before stop paging for SI.

    ReplyDelete
    Replies
    1. I think the paging for SI change is repeated for 'modificationPeriodCoeff' number of times as actual modification period = modificationPeriodCoeff * defaultPagingCycle.

      Note that the change notification period is same as modification period

      Delete
  12. Hello Kumar,

    I've one doubt regarding the RRC creating the record list,
    In case of downlink data notification from SGW during the RRC_IDLE, ECM_IDEL, & EMM_Registered. The S1AP paging message consists only one UE identity index which is calculated as IMSI % 1024, the eNB receives this S1AP paging message to only one UE. Is this correct my understanding?
    If yes then how and in what scenarios the RRC will create the paging record list.
    The ETWS, CMOS & SI change is commonly broadcasted to all the UEs, UE identity is not required in this message.

    --Venkat.

    ReplyDelete
    Replies
    1. Hi Venkat,
      Sorry, I don't know the paging message contents and how it works between the core and the enodeB. I think the eNodeB gathers the list during one paging cycle.

      Delete
    2. The S1-AP Paging message is used by the MME to inform an eNB about a paging message to a particular UE. During the period of duration between two paging occasions(PO), the eNB may receive multiple S1-AP Paging messages corresponds to multiple UEs in the cell. So, by combining all those S1-AP Paging messages, the eNB composes a single RRC Paging message. A single RRC Paging message can be composed from a maximum of 16 S1-AP Paging messages.

      Delete
  13. Can you give an idea of how we can develop a code for lte paging implementation using c language in client server model.What are the contents of rrc and s1ap messages?..Should we need to take them as seperate functions?

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  14. Hi Kumar ..nice article i need one clarification .. paging with systeminformationModification means that SIB1 content has been changed .. other sibs have changed or not UE get to know only after it read the sib1 systemInfoValueTag which tells if there is any change in SI messages .. am i right here ?

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    Replies
    1. You are absolutely correct. According 36331, section 5.2.2.3, the UE Shall consider any stored system information except SystemInformationBlockType10, SystemInformationBlockType11 and systemInformationBlockType12 to be invalid if systemInfoValueTag included in the SystemInformationBlockType1 is different from the one of the stored system information

      Delete
  15. Nicely explained !!
    Is there any reason that only 16 paging records can be sent at once ?

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    Replies
    1. Probably restriction on the message size and there by resource allocation for Paging message

      Delete
  16. What is the time taken of 1 paging cycle? What is the maximum time duration between two paging cycle ? (in LTE) What is the frame structure ( number of symbols/bits) for paging?

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    Replies
    1. RadioResourceConfigCommon in system information provides all the required parameters to calculate paging occasions.

      Please refer to section 7.1 from 36.304 for a good explanation about the calculations.

      Delete
  17. Hi Kumar,

    I have a small question, can you please explain.
    Sometimes, Why the paging message are missed at the UE.

    Thanks

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  18. Hi Kumar! First of all, Congrats for this great site! I wanted to share my experience with VoLTE. I see situations in which excessive Pagings on the VoLTE call initiating party result in long setup times, since it takes a lot of time to progress on the SIP related signalling (INVITE, TRYING, etc). Do you have some hints why this excessive Paging?

    Many thanks!

    BR,

    David

    ReplyDelete