1. Requirements and Implementations for Intra-flow/Intra-AC DiffServ
4/25/2019May 2008
November 2007
doc.: IEEE /2752r1
2019/4/25
Requirements and Implementations for Intra-flow/Intra-AC DiffServ
Date:
Authors:
Jun Li, Thomson Inc..
Peter Ecclesine, Cisco Systems

2. 4/25/2019May 2008
November 2007
doc.: IEEE /2752r1
2019/4/25
Abstract
One of the goals of VTS is to enable link layer adaptation on differentiated frames in a video stream according to channel conditions. This requires an intra-flow/intra-AC differentiated service (intra-Flow DiffServ), which is not supported in e QoS amendments. This proposal discusses the requirements on link layer intra-flow DiffServ and presents solutions accordingly.
Jun Li, Thomson Inc..
Peter Ecclesine, Cisco Systems

3. Outlines Why we need intra-flow/intra-AC DiffServ? Approach
4/25/2019May 2008
November 2007
doc.: IEEE /2752r1
2019/4/25
Outlines
Why we need intra-flow/intra-AC DiffServ?
Approach
Possible Differentiation Fields
Solution 1: Modify QoS control field
Solution 2: Add a 2-type new field before Frame body
Compatibility to e
Management frame modifications for supporting intra-flow DiffServ
Jun Li, Thomson Inc..
Peter Ecclesine, Cisco Systems

4. Why we need intra-flow/intra-AC DiffServ?
2019/4/25
Why we need intra-flow/intra-AC DiffServ?
VTS PAR scope proposed the following MAC enhancement
Graceful degradation of audio video streams when there is insufficient channel capacity, by enabling packet discarding without any requirement for deep packet inspection.
Intra-Access Category prioritization of transport streams by modifying EDCA timing and parameter selection without any requirement for deep packet inspection.
Improved link reliability and low jitter characteristics for multicast/broadcast audio video streams
Differentiated frames have different importance in a video transport stream, e.g.,
Video content dependent MAC frames, e.g.
SVC base layer or enhance layer;
I,P,B frames in MPEG-2 or H.264
Region of interest based encoding
Channel coding frames, e.g.
FEC and/or ARQ
Jun Li, Thomson Inc..

5. 2019/4/25
Approach
Basic idea: define new information fields in MAC frame to realize frame differentiation without requiring deep frame inspection.
Information required:
VTS flag
For distinguishing the VTS MAC frames against legacy frames
VTS stream identification (VTS-SID)
For a pair of source and destination addresses, multiple streams may be served. Need to differentiate one stream from another, so that intra-flow (aka. intra-stream) differentiation can be done for each stream
In case of intra-AC (Access Category of EDCA), VTS-SID may not be required
VTS stream intra-flow differentiation fields
Used for frame differentiation within one video flow, e.g.,
I,P,B frames in MPEG-2 video flow;
video, audio, FEC packets in one video flow
Provide the frame dropping criteria when there is insufficient channel capacity
Jun Li, Thomson Inc..

6. Possible Differentiation Fields
2019/4/25
Possible Differentiation Fields
Priority
Corresponding to content dependent frames for intra-flow or intra-AC
Dropping precedence
How to drop – consecutive or not
Frame category
Video/Audio
FEC
Jun Li, Thomson Inc..

7. Solution 1: Modify QoS control field
2019/4/25
Solution 1: Modify QoS control field
Applicable frame
(sub) types
Bits
0–3
Bit 4
Bits 5-6
Bit 7
Bits 8–15
QoS (+)CF-Poll frames sent by HC
TID
EOSP
Ack Policy
Reserved
TXOP Limit
QoS Data, QoS Null, and QoS Data+CF-Ack frames sent by HC
QAP PS Buffer State 1
Intra-flow/Intra-AC information
QoS data frames sent by non-AP QSTAs
TXOP Duration Requested
Queue Size
The TID subfield (4 bits) identifies the TC or TS to which the corresponding MSDU, or fragment thereof, in the Frame Body field belongs.
The EOSP subfield (1 bit) is used by the HC to indicate the end of the current service period (SP).
The Ack Policy subfield (2 bits) identifies the acknowledgement policy. 00=normal Ack, 10=No Ack, 01= No explicit acknowledgment. 11= Block Ack
Bit 7 flag indicates it is a VTS frame with intra-flow/ intra-Access Category (AC) information included. When the flag is set, intra-flow/intra-Access Category field is contained in bits When the flag is not set, other information is contained in bits 8-15.
Jun Li, Thomson Inc..

8. Example 1: Intra-AC only (solution 1 Contd.)
2019/4/25
Example 1: Intra-AC only (solution 1 Contd.)
Drop
Precedence
Intra-AC
Priority
Reserved
intra-flow/intra-AC information B8 B9
B10
B11
B15
Drop precedence subfield (1 bit) indicates how the frame is dropped. When the flag is set, this frame will be discarded for graceful degradation when there is insufficient channel capacity.
Intra-AC Priority subfield (2 bits) indicates the priority of the frame in the transport stream.
Jun Li, Thomson Inc..

9. Example 2: Intra-Flow DiffServ (solution 1 Contd.)
2019/4/25
Example 2: Intra-Flow DiffServ (solution 1 Contd.)
Drop
Precedence
Intra-Flow
Priority
Reserved
intra-flow/intra-AC information B8 B9
B10
B11
B15
B14
VTS-SID
B13
Frame category
Drop Precedence subfield (1 bit) indicates the Precedence that this frame is discarded for graceful degradation when there is insufficient channel capacity. When the flag is set, this frame will be dropped first when there is insufficient channel capacity.
Intra-Flow Priority subfield (2 bits) indicates the priority of the frame in the transport stream
VTS-SID (3 bits) indicates the stream ID which identifies a given video stream, i.e. frames with the same ID belong to same stream.
Frame category (1 bit) indicates FEC channel coding. When the bit is set, the frame is an FEC frame, otherwise it is a source video frame. This field can be optional.
Jun Li, Thomson Inc..

10. Example 3: Intra-Flow DiffServ (solution 1 Contd.)
2019/4/25
Example 3: Intra-Flow DiffServ (solution 1 Contd.) B0 B4 B8 B9
B10
B11
B13
B14
B15
VTS-SID
(TID)
Drop
Precedence
Intra-Flow
Priority
Reserved
Frame category
Reserved
intra-flow/intra-AC information TS
Info
TSPEC element
Bits: B0 B7 B8 B9
B11
B13
B18
B21
B22
B23
Access policy = 01 UP
Reserved
TS Info field
When TID = 8-15, it can be directly used as VTS-SID. A TSPEC management frame must be used to specify parameters of the stream. In this case, a VTS frame needs to make sure Access policy = 01 (EDCA) and UP (user priority) = AC (access category), in order to compatible with EDCA.
Jun Li, Thomson Inc..

11. Solution 2: Add a 2-type new field before Frame body
2019/4/25
Solution 2: Add a 2-type new field before Frame body
Frame Control
Octets:2 2
Address 1
Duration/ ID
Address 2
Address 3
Sequence control 6
Address 4
QoS Control
VTS control information
Frame Body
2302
FCS 4
VTS control
VTS-SID
Bits: B0 B3 B4 B5 B6 B7 B8
B15
Reserved
Dropping criteria
Priority
B11
B12
B13
Frame category
B14
A 2-byte field, VTS control field, is defined and added before the frame body in the data frame. Priority, Dropping criteria, Frame category fields are defined as same as in solution 1.
The bit 7 in QoS control field (see the following figure) shall be set to 1, based on which the VTS MAC frame can be distinguished by a VTS station.
TID
Bits: B0 B3 B4 B5 B6 B7 B8
B15
VTS
Flag =1
B11
B12
QoS control field in MAC frame
Jun Li, Thomson Inc..

12. Compatibility to 802.11e No compatibility to HCCA
2019/4/25
Compatibility to e
No compatibility to HCCA
It is not required that a VTS device support HCCA function
Backward compatibility to EDCA
VTS devices can process EDCA frames produced by legacy devices.
If all EDCA functions are supported, it is fully compatible.
Forward compatibility to EDCA
Legacy e device can process VTS frames as normal EDCA frames.
However, a frame generated by VTS device may not contain information of QAP PS buffer status, a possible optional function for EDCA
Solution 1 is backward & forward compatible, solution 2 is backward compatible only.
Jun Li, Thomson Inc..

13. Management frame modifications for supporting intra-flow DiffServ
2019/4/25
Management frame modifications for supporting intra-flow DiffServ
Following management frames need to be modified
Beacon frame
Association request / Reassociation request
Association response / Reassociation response
Following information elements / fields contained in the above frames need to be extended
QoS capability information element
QoS info field
Jun Li, Thomson Inc..