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Technical Specification
Universal Mobile Telecommunications System (UMTS);
MBMS synchronisation protocol (SYNC)
(3GPP TS 25.446 version 9.2.0 Release 9)
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3GPP TS 25.446 version 9.2.0 Release 9 1 ETSI TS 125 446 V9.2.0 (2010-06)
Reference
RTS/TSGR-0325446v920
Keywords
UMTS
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ETSI
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3GPP TS 25.446 version 9.2.0 Release 9 2 ETSI TS 125 446 V9.2.0 (2010-06)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
.
ETSI
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3GPP TS 25.446 version 9.2.0 Release 9 3 ETSI TS 125 446 V9.2.0 (2010-06)
Contents
Intellectual Property Rights . 2
Foreword . 2
Foreword . 5
1 Scope . 6
2 References . 6
3 Definitions and abbreviations . 6
3.1 Definitions . 6
3.2 Abbreviations . 6
3.4 Specification notations . 7
4 General . 7
4.1 General aspects for the SYNC protocol for UTRAN . 7
4.1.1 General aspects . 7
4.2 General aspects for the SYNC protocol for E-UTRAN . 8
4.2.1 General aspects . 8
5 SYNC protocol version 1 . 9
5.1 General . 9
5.1.1 Applicablity of SYNC protocol version 1. 9
5.1.1 Operation of the SYNC protocol . 9
5.1.2 Interfaces of the SYNC protocol layer . 9
5.2 SYNC protocol layer services . 9
5.3 Services Expected from the UP Data Transport layer . 9
5.4 Elementary procedures . 10
5.4.1 Transfer of User Data for MBMS procedure . 10
5.4.1.1 Successful operation. 10
5.4.1.2 Unsuccessful operation . 10
5.4.2 Transfer of Synchronisation Information for MBMS procedure (without user data) . 11
5.4.2.1 Successful operation. 11
5.4.2.2 Unsuccessful operation . 11
5.5 Elements for the SYNC protocol . 11
5.5.1 General . 11
5.5.2 Frame format for the SYNC protocol . 12
5.5.2.1 Transfer of Synchronisation Information without payload (SYNC PDU Type 0) . 12
5.5.2.2 Transfer of User Data for MBMS with uncompressed header (SYNC PDU Type 1) . 13
5.5.2.3 Transfer of User Data for MBMS with compressed header (SYNC PDU Type 2) . 14
5.5.2.4 Transfer of Synchronisation Information with Length of Packets (SYNC PDU Type 3) . 15
5.5.3 Coding of information elements in frames . 17
5.5.3.1 PDU Type . 17
5.5.3.2 Timestamp . 18
5.5.3.3 Packet Number . 18
5.5.3.4 Elapsed Octet Counter . 18
5.5.3.5 Total Number Of Packet . 18
5.5.3.6 Total Number Of Octet . 18
5.5.3.7 PDCP Information . 18
5.5.3.8 IPv6 Indicator . 19
5.5.3.9 Uncompressed Payload IP header . 19
5.5.3.10 Header CRC . 19
5.5.3.11 Payload CRC . 19
5.5.3.12 Padding . 19
5.5.3.13 Spare . 19
5.5.3.14 Spare extension . 19
5.5.3.15 Payload fields . 20
th
5.5.3.16 Length of the N Packet . 20
5.5.4 Timers . 20
ETSI
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3GPP TS 25.446 version 9.2.0 Release 9 4 ETSI TS 125 446 V9.2.0 (2010-06)
5.6 Handling of unknown, unforeseen and erroneous protocol data . 20
5.6.1 General . 20
5.6.2 CRC Calculation . 20
5.6.3 Relation between input and output of the Cyclic Redundancy Check . 21
Annex A (informative): Change history . . 22
History . 23
ETSI
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3GPP TS 25.446 version 9.2.0 Release 9 5 ETSI TS 125 446 V9.2.0 (2010-06)
Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
ETSI
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3GPP TS 25.446 version 9.2.0 Release 9 6 ETSI TS 125 446 V9.2.0 (2010-06)
1 Scope
The present document specifies the MBMS Synchronisation Protocol. For the release of this specification it is used on
Iu towards UTRAN and M1 towards E-UTRAN.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 25.410: "UTRAN Iu interface: General Aspects and Principles".
[3] 3GPP TS 25.323: "Packet Data Convergence Protocol (PDCP) specification".
[4] 3GPP TS 25.346: "Introduction of the Multimedia Broadcast Multicast Service (MBMS) in the
Radio Access Network (RAN); Stage 2".
[5] 3GPP TS 36.440: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); General
aspects and principles for interfaces supporting Multimedia Broadcast Multicast Service (MBMS)
within E-UTRAN".
[6] 3GPP TS 36.300: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall
description".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in TR 21.905 [1] and the following apply. A
term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 [1].
RAN Access interface: interface between the Core Network and the Radio Access Network.
RAN Access node: termination point of the RAN Access interface at the Radio Access Network.
MBMS RAB: denotes the Radio Access data bearer together with the RAN Access Interface data bearer for MBMS
service user data transmission.
3.2 Abbreviations
For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
TR 21.905 [1].
SYNC MBMS synchronisation protocol
ETSI
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3GPP TS 25.446 version 9.2.0 Release 9 7 ETSI TS 125 446 V9.2.0 (2010-06)
3.4 Specification notations
For the purposes of the present document, the following notations apply:
Procedure When referring to a procedure in the specification the Procedure Name is written with the first
letters in each word in upper case characters followed by the word "procedure", e.g. Iu Rate
Control procedure.
Frame When referring to a control or data frame in the specification, the CONTROL/DATA FRAME
NAME is written with all letters in upper case characters followed by the words "control/data
frame", e.g. TIME ALIGNMENT control frame.
IE When referring to an information element (IE) in the specification the Information Element Name
is written with the first letters in each word in upper case characters and all letters in Italic font
followed by the abbreviation "IE", e.g. Frame Number IE.
Value of an IE When referring to the value of an information element (IE) in the specification the "Value" is
written as it is specified in subclause 5.6.3 enclosed by quotation marks, e.g. "0" or "255".
4 General
4.1 General aspects for the SYNC protocol for UTRAN
4.1.1 General aspects
The MBMS Synchronisation protocol (SYNC) is located in the User plane of the Radio Network layer over the Iu
interface: the Iu UP protocol layer.
The SYNC protocol for UTRAN is used to convey user data associated to MBMS Radio Access Bearers.
One SYNC protocol instance is associated to one MBMS RAB and one MBMS RAB only. If several MBMS RABs are
established towards one given UE, then these MBMS RABs make use of several SYNC protocol instances.
SYNC protocol instances exist at Iu access point as defined [2] i.e. at CN and UTRAN.
Whenever an MBMS RAB requires transfer of user data in the Iu UP, an Iu UP protocol instance exists at each Iu
interface access points. These Iu UP protocol instances are established and released together with the associated MBMS
RAB.
The following figure illustrates the logical placement of the SYNC protocol layer and the placement of the Data
Streams sources outside of the Access Stratum.
ETSI
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3GPP TS 25.446 version 9.2.0 Release 9 8 ETSI TS 125 446 V9.2.0 (2010-06)
NAS Data NAS Data
Non-Access Stratum
Streams Streams
Radio SYNC
Radio SYNC
proto-
proto-
cols
Transport
cols
TNL Layer
TNL
Protocol
Protocol
Access Stratum
CN
UE
UTRAN
Radio
Iu
(Uu)
Figure 4.1.1-1: SYNC protocol layer occurrence in UTRAN overall architecture (User Plane View)
4.2 General aspects for the SYNC protocol for E-UTRAN
4.2.1 General aspects
The MBMS Synchronisation protocol (SYNC) is located in the User plane of the Radio Network layer over the M1
interface: the M1 UP protocol layer.
The SYNC protocol for E-UTRAN is used to convey user data associated to MBMS Radio Access Bearers.
One SYNC protocol instance is associated to one MBMS E-RAB and one MBMS E-RAB only.
SYNC protocol instances exist at M1 access point as as defined [5] i.e. at EPC and E-UTRAN.
Whenever an MBMS E-RAB requires transfer of user data in the M1 UP, an M1 UP protocol instance exists at each M1
interface access points. These M1 UP protocol instances are established and released together with the associated
MBMS E-RAB.
The following figure illustrates the logical placement of the SYNC protocol layer and the placement of the Data
Streams sources outside of the Access Stratum.
NAS Data NAS Data
Non-Access Stratum
Streams Streams
Radio SYNC
Radio SYNC
proto-
proto-
cols
Transport
cols
Layer
TNL
TNL
Protocol
Protocol
Access Stratum
CN
UE
E-UTRAN
Radio
M1
(Uu)
Figure 4.2.1-1: SYNC protocol layer occurrence in E-UTRAN overall architecture (User Plane View)
ETSI
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3GPP TS 25.446 version 9.2.0 Release 9 9 ETSI TS 125 446 V9.2.0 (2010-06)
5 SYNC protocol version 1
5.1 General
5.1.1 Applicablity of SYNC protocol version 1
This version of the specification specifies the SYNC protocol for UTRAN and E-UTRAN. It is on top of TNL in Iu
(UTRAN) and M1 (E-UTRAN) user plane, i.e. Iu userplane TNL transports SYNC protocol PDUs over the Iu interface,
M1 userplane TNL transports SYNC protocol PDUs over the M1 interface.
As a specification convention, within this specification, the interface between the Core Network and the Radio Access
Network is denoted as the 'RAN Access Interface', the termination point at the Radio Access Network is denoted as
'RAN Access Node', the termination point at the Core Network is denoted as 'Core Network' (CN). Further, 'MBMS
RAB' denotes the Radio Access data bearer together with the RAN Access Interface data bearer for MBMS service user
data transmission.
For the application of the SYNC protocol to UTRAN, the RAN Access Interface is the Iu interface, the RAN Access
Node is the RNC.
For the application of the SYNC protocol to E-UTRAN, the RAN Access Interface is the M1 interface, the RAN Access
Node is the eNB.
5.1.1 Operation of the SYNC protocol
The SYNC protocol layer is present for data streams that originate in the CN and carry additional information within a
specific userplane-frame.
The two strata communicate through a Service Access Point for Non Access Stratum (NAS) Data Streams transfer.
5.1.2 Interfaces of the SYNC protocol layer
As part of the Access Stratum responsibility, the SYNC protocol layer provides the services and functions that are
necessary to handle non access stratum data streams for MBMS. The SYNC protocol layer is providing these services to
the UP upper layers through a Dedicated Service Access Point used for Information Transfer.
The SYNC protocol layer is using services of the Transport layers in order to transfer user plane PDUs over the RAN
Access interface.
5.2 SYNC protocol layer services
The following functions are needed to support the SYNC protocol:
- Transfer of user data along with synchronisation information;
- Transfer of synchronisation information without user data.
5.3 Services Expected from the UP Data Transport layer
The SYNC protocol layer expects the following services from the Transport Network Layer:
- Transfer of user data.
- no flow control
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3GPP TS 25.446 version 9.2.0 Release 9 10 ETSI TS 125 446 V9.2.0 (2010-06)
5.4 Elementary procedures
5.4.1 Transfer of User Data for MBMS procedure
5.4.1.1 Successful operation
The purpose of the Transfer of User Data procedure for MBMS is to transfer RAN Access Interface UP frames from the
RAN Access interface UP protocol layers at CN to the RAN Access interface UP protocol layer at the RAN Access
Node. One RAN Access interface UP instance is associated to a single MBMS RAB only.
The Transfer of User Data procedure is invoked whenever user data for that particular RAB needs to be sent across the
Radio Access interface.
The NAS Data Streams specific functions make the padding of the payload (if needed) so that the Radio Access
interface UP frame payload will be an integer number of octets. Then the NAS Data Streams specific functions perform,
if needed, CRC calculation of the Iu/M1 frame payload and passes the Radio Access interface UP frame payload down
to the Frame Handler function.
The Frame Handler function within the CN retrieves the packet counter and octet counter value from its internal
memory, formats the frame header and frame payload into the appropriate PDU Type and sends the Radio Access
interface UP frame PDU to the lower layers for transfer across the Radio Access interface. If the user data is provided
with compressed IP header, the Radio Access interface UP frame contains PDCP information and the uncompressed IP
header.
The Frame Handler function within the CN is also responsible for appropriate setting of the Time Stamp value in order
to allow all RAN Access nodes to submit the MBMS user data in a synchronised manner.
Upon reception of a user data frame, the RAN Access interface UP protocol layer within the RAN Access node checks
the consistency of the RAN Access interface UP frame as follows:
- The Frame Handler function checks the consistency of the frame header and the consistency of the packet
counter value.
- Then the RAN Access node utilises the time stamp information to schedule the user data on the radio interface
on the next TTI for UTRAN or MCH scheduling period for E-UTRAN as defined in [6].
RAN Access
CN
node
TRANSFER OF USER DATA
Figure 5.4.1.1-1. Successful Transfers of User Data.
5.4.1.2 Unsuccessful operation
If the multiple consecutive RAN Access interface UP frames carrying the user data are incorrectly formatted or cannot
be correctly treated by the receiving RAN Access interface UP protocol layer, or if multiple consecutive frames loss is
detected due gaps in the sequence of the received frame numbers, and in case the RAN Access Interface UP is the Iu
UP, the RAN Access node shall, if packet length information in Type 3 is not provided, cease to provide user data to the
radio interface protocol entities and wait until the next synchronisation sequence if soft combining and MBSFN are
used, or until the next scheduling transmission interval if the MRNC and TDM multiplexing are used. In case the RAN
Access Interface UP is the M1, the RAN Access node shall, if packet length information in Type 3 is not provided,
cease to provide user data to the radio interface protocol entities and wait until the next dynamic scheduling interval, as
described in [6].
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3GPP TS 25.446 version 9.2.0 Release 9 11 ETSI TS 125 446 V9.2.0 (2010-06)
If packet length information in Type 3 is provided, the RAN Access nodes could cease to provide user data to the radio
interface protocol entities for those lost subframes.
5.4.2 Transfer of Synchronisation Information for MBMS procedure
(without user data)
5.4.2.1 Successful operation
The purpose of the Transfer of Synchronisation Information for MBMS procedure is to transfer synchronisation
information from the CN to the RAN Access node at the end of each synchronization sequence (see [4, 6]) to improve
the RAN Access node resynchronization in case of packet loss.
The Frame Handler function within the CN retrieves the synchronisation time stamp from its internal clock and the total
packet counter and total octet counter from its internal memory, formats the frame header and frame payload into the
appropriate PDU Type and sends the RAN Access interface UP frame PDU to the lower layers for transfer across the
RAN Access interface.
If there is no data frame in a synchronization sequence, synchronization information shall still be transmitted.
Furthermore, the SYNC PDU towards RAN Access node could contain length of each packet if supported.
Upon reception of a user data frame, the RAN Access interface UP protocol layer checks the consistency of the RAN
Access interface UP frame as follows:
- The Frame Handler function checks the consistency of the frame header and the consistency of the
synchronisation time stamp, total packet counter, total octet counter and packets length counter value if
contained.
RAN Access
CN
node
TRANSFER OF SYNC INFO
Figure 5.4.2.1-1. Successful Transfers of Synchronisation Information.
5.4.2.2 Unsuccessful operation
If the RAN Access interface UP frame without user data is incorrectly formatted or cannot be correctly treated by the
receiving RAN Access interface UP protocol layer, the RAN Access interface UP protocol layer shall either discard the
frame or pass it to the upper layers with a frame classification indicating a corrupted frame.
5.5 Elements for the SYNC protocol
5.5.1 General
In the present document the structure of frames will be specified by using figures similar to Figure 5.5.1-1.
ETSI
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Number of
Octets
3GPP TS 25.446 version 9.2.0 Release 9 12 ETSI TS 125 446 V9.2.0 (2010-06)
Bits
7 6 5 4 3 2 1 0
Field 1 Field 2 1 Octet 1 Header
part
Field 3 Field 4 2 Octet 2
Field 4 continue Spare Octet 3
2
Field 6 Octet 4 Payload
part
Octet 5
Field 6 continue Padding
0-m
Spare extension
Figure 5.5.1-1. Example frame format.
Unless otherwise indicated, fields which consist of multiple bits within an octet will have the more significant bit
located at the higher bit position (indicated above frame in Figure 5.5.1-1). In addition, if a field spans several octets,
more significant bits will be located in lower numbered octets (right of frame in Figure 5.5.1-1).
On the Iu/M1 interface, the frame will be transmitted starting from the lowest numbered octet. Within each octet, the
bits are sent according decreasing bit position (bit position 7 first).
Spare bits should be set to "0" by the sender and should not be checked by the receiver.
The header part of the frame is always an integer number of octets. The payload part is octet rounded (by adding
'Padding' when needed).
The receiver should be able to remove an additional spare extension field that may be present at the end of a frame. See
descrip
...