L.4 MBMS Download Profile
26.3463GPPMultimedia Broadcast/Multicast Service (MBMS)Protocols and codecsRelease 17TS
L.4.1 Introduction
The MBMS Download Profile primarily defines the required, expected and permitted usage of FLUTE FDT attributes and elements by the BM-SC, and the corresponding mandatory versus optional support for those FDT parameters by the MBMS Client. The MBMS Download Profile is associated with the delivery of both non-real-time (NRT) file delivery services as well as DASH-formatted streaming services, using the FLUTE protocol. The FDT attributes and elements are categorized at the FDT-Instance level (i.e., the FDT-Instance element of the FDT) and at the File level (i.e., the File element of the FDT). The Download Profile constrains the large set of FDT parameters specified in sub-clause 7.2 of this document, which includes both the FDT elements and attributes defined by the IETF FLUTE standard, RFC 3926 [9] and various 3GPP-defined FDT extensions for MBMS. The MBMS Download Profile is based on existing and planned deployments of eMBMS services containing both NRT file contents as well as DASH-formatted media components.
Other topics addressed by the MBMS Download Profile include the usage of the XML Schema elements schemaVersion and delimiter for forward and backward compatibility support, RTSP control of FLUTE sessions, Application Layer FEC, usage of the LCT Header Extension "EXT_FTI", the means to signal the end of the FLUTE session or the end of individual file transmissions, and timing-related fields in LCT such as Sender Current Time (SCT), Expected Residual Time (ERT), and the LCT Extension Header’EXT_TIME’.
The usage of OMA Push and RTSP (as defined in clause 7.4) are excluded from the MBMS Download Profile.
In addition, an implementation profile of the SDP for a FLUTE session is included, based on the description in clause 7.3 of this specification.
L.4.2 Common FDT-Instance and File Attributes
The following FDT attributes, defined at both the FDT-Instance and File levels, shall be carried in the FDT sent by the FLUTE sender, under either the File-Instance or File element, and shall be supported by the FLUTE receiver:
– Content-Type
– FEC-OTI-FEC-Encoding-ID
– FEC-OTI-Maximum-Source-Block-Length
– FEC-OTI-Encoding-Symbol-Length
– FEC-OTI-Scheme-Specific-Info
NOTE: See sub-clause L.4.4 on the usage rule for these parameters at the File level of the FDT.
The following FDT attribute, defined at both the FDT-Instance and File levels, may be carried in the FDT sent by the FLUTE sender, under either the File-Instance or File element, and shall be supported by the FLUTE receiver:
– Content-Encoding set to ‘gzip’
The following FDT parameters, defined at both the FDT-Instance and File levels, shall not be used by the FLUTE sender, in either the File-Instance or File element:
– Content-Encoding attribute set to a value other than ‘gzip’
– FEC-OTI-FEC-Instance-ID attribute (not applicable to Rel-9 FEC schemes)
– Group element
NOTE: These parameters are optional to support by the FLUTE receiver.
L.4.3 FDT-Instance specific Elements and Attributes
The following parameters, defined at the FDT-Instance level, shall not be used by the FLUTE sender:
– Complete attribute
– mbms2008:FullFDT attribute
– MBMS-Session-Identity-Expiry element
NOTE: With the exception of Complete, which is mandatory, these parameters are optional to support by the FLUTE receiver.
L.4.4 FDT File specific Elements and Attributes
The following attributes, defined at the File level, shall be carried in the FDT sent by the FLUTE sender, and shall be supported by the FLUTE receiver, subject to the qualifications indicated below:
– Content-Location
– TOI
– Content-Length
– Content-MD5
– This attribute should be included in the FDT for non-DASH services
– This attribute may be included in the FDT for DASH Segments.
The following element may be carried in the FDT sent by the FLUTE sender, and shall be supported by the FLUTE receiver:
– mbms2007:Cache-Control
The following attributes shall only be carried in the in the File element of the FDT sent by the FLUTE sender, for the purpose of replacing or overriding corresponding attributes at the FDT-Instance level.
– Content-Type
– FEC-OTI-FEC-Encoding-ID
– FEC-OTI-Maximum-Source-Block-Length
– FEC-OTI-Encoding-Symbol-Length
– FEC-OTI-Scheme-Specific-Info
The following attributes shall not be carried in the FDT sent by the FLUTE sender:
– Transfer-Length
– mbms2009:Decryption-KEY-URI
– mbms2012:FEC-Redundancy-Level
– MBMS-Session-Identity
NOTE: With the exception of Transfer-Length, which is mandatory, these parameters are optional to support by the FLUTE receiver.
L.4.5 Version and Delimiter Schema
As indicated in Annex J.2, this specification defines two XML Schema elements necessary for the UE and the network side to maintain forward and backward compatibility: schemaVersion and delimiter. These elements are used by the following schemas: USBD, Schedule Description, Filter Description and FDT. Whichever schema version supported by the UE will not affect compliance to this Download Delivery Profile. If the UE supports multiple versions of the FDT schema, the UE selects the schema version according to the rules specified in clause 7.2.10.1. As indicated in Annex J.2, the supported delimiter element has value = "0" as set by the network, and the element content should be ignored by the UE.
L.4.6 Void
L.4.7 Other Aspects of FLUTE Delivery
Regarding Application Layer FEC support, the two FEC schemes referenced in this specification, the Compact No-Code FEC scheme as specified in RFC 5052 [12], and the Raptor FEC scheme as specified in RFC 5053 [91] are optional to implement by the BM-SC and mandatory to support by the UE. File fragmentation into blocks is supported. In the case of the Compact No-Code FEC scheme, the blocking algorithm as defined in RFC 3695 [13] should be used. For the Raptor FEC scheme, specification of the blocking algorithm should comply with the recommendations on the derivation of the relevant parameters as defined in RFC 5053 [91].
As indicated in sub-clause 7.2.4 of this specification, congestion control is not used for FLUTE delivery in MBMS, and therefore, FLUTE channelization should be provided by a single FLUTE channel with single rate transport.
Regarding FLUTE session description, an instance of Session Description fragment, comprising an SDP file, will contain all parameters as defined in clause 7.3 of this specification.
The LCT Header Extension "EXT_FTI" as defined by ALC [10], for the purpose of communicating FEC Object Transmission Information, should be used in FLUTE packets that carry symbols of FDT Instance(s). FEC Object Transmission Information in FLUTE packets which carry symbols of content files should be conveyed by the FEC-OTI parameters in the FDT, and for which the expectations on network usage and UE support are specified in clauses 5.2.1.1 and 5.2.1.2.
Timing related fields in LCT corresponding to Sender Current Time (SCT) and Expected Residual Time (ERT), either in the form of the T and R flags in the LCT header, or carried in the LCT Extension Header ‘EXT_TIME’, are not used in the Download Delivery Profile. The network should set these flags/fields to zero, and the UE should ignore them.
L.4.8 SDP Parameters for FLUTE Session
This clause specifies the implementation profile for the SDP parameters of an MBMS download delivery session, which are identified and described in clause 7.3.2 and its sub-clauses. It should be noted that not all of these SDP parameters (carried in the Session Description fragment of MBMS User Service Announcement) are necessarily applicable. Table L.4.8-1 summarizes those that are mandatory, optional or not applicable (should not be present in the SDP), along with clarification text, for an associated FLUTE session. The MBMS receiver is required to support both the mandatory and optional SDP parameters.
Table L.4.8-1: SDP Profile for FLUTE Session
|
SDP Parameter |
Required |
Optional |
Not Applicable |
Clarification |
|
No. of channels in FLUTE session |
✓ |
Only one FLUTE channel is allowed per FLUTE session |
||
|
Source IP address |
✓ |
As defined in clause 7.3.2.1 |
||
|
Destination IP address |
✓ |
As defined in clause 7.3.2.3 |
||
|
TSI |
✓ |
As defined in clause 7.3.2.4 |
||
|
Session timing |
✓ |
As defined in clause 7.3.2.6. If both the SDP’s session timing parameters and the Schedule Description metadata fragment are present, the session schedule in the latter shall take precedence. |
||
|
Transport protocol ID |
✓ |
As defined in clause 7.3.2.13 |
||
|
Media type and format description |
✓ |
As defined in clause 7.3.2.14 |
||
|
Data rate |
✓ |
As defined in clause 7.3.2.10 |
||
|
Mode of MBMS bearer per media |
✓ |
As defined in clause 7.3.2.7 |
||
|
FEC capabilities and related parameters |
✓ |
As defined in clauses 7.3.2.8 and 7.3.2.11 |
||
|
Per-media service language |
✓ |
For DASH-formatted content, is described by the @lang attribute in the MPD. Not applicable for NRT content. |
||
|
QoE metrics |
✓ |
As defined in clauses 8.3.2.1 and 8.4 |
||
|
Alternative TMGI |
✓ |
As defined in clause 7.3.2.12 |