March, 2008 Inha Univ. Slide 1 doc.: IEEE 802.15-08-0126- 01-003c Submiss ion Project: IEEE P802.15 Working Group for Wireless Personal Area Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Networks (WPANs) Submission Title: [A Modified Aggregation Process] Date Submitted: [March 16, 2008] Source: [Kyungsup Kwak, Seokho Kim, Xizhi An] Company: [Inha University] Address: [6-141B, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon, 402-751, Republic of Korea] Voice: [], FAX: [], E-Mail: [[email protected], [email protected], [email protected]] Re: [] Abstract: [This document gives some comments on aggregation process in current draft standard. In order to make “3c” standard more compatible with “3” and “3b”, we propose a modified aggregation process that is transparent to MAC layer.] Purpose: [To be considered in IEEE 802.15.3c standard] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly
Transcript
March, 2008
Inha Univ.Slide 1
doc.: IEEE 802.15-08-0126-01-003c
Submission
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [A Modified Aggregation Process]Date Submitted: [March 16, 2008]Source: [Kyungsup Kwak, Seokho Kim, Xizhi An]Company: [Inha University]Address: [6-141B, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon, 402-751, Republic of Korea]Voice: [], FAX: [], E-Mail: [[email protected], [email protected], [email protected]] Re: []Abstract: [This document gives some comments on aggregation process in current draft standard. In order to make “3c” standard more compatible with “3” and “3b”, we propose a modified aggregation process that is transparent to MAC layer.]Purpose: [To be considered in IEEE 802.15.3c standard]Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.
March, 2008
Inha Univ.Slide 2
doc.: IEEE 802.15-08-0126-01-003c
Submission
Overview
• Review of Aggregation Process– Current Draft (DFx):
• New Proposal of Aggregation Process– Modified Aggregation Process– New PHY frame formatting
March, 2008
Inha Univ.Slide 3
doc.: IEEE 802.15-08-0126-01-003c
Submission
Review of Aggregation Process in DFx
• Incompatible with 802.15.3 & 3b• In section 8.7a, subframe is confused with MPDU.
– In fact, the fragmentation is the same as section 8.7 – Blk-ACK is unnecessary. In fact subframe just is MPDU and ACK is done on the
MPDU basis, so Dly-ACK can do this job.– Subheader is similar to MAC header, however fragmentation control can not work.
• Functions of different layers are mixed up!– Aggregation shall be realized in PHY layer,
• “Number of subframes” field is in PHY header.• PHY frame is like a kind of “container”, which conveys MPDUs.• PHY only passes frames to the MAC that have passed the HCS test.
– Fragmentation and ACK shall be performed in MAC layer.• When MSDU/MCDU is fragmented, the fragmentation control information for
each fragment must be set correspondingly.• The MAC validates the error free reception of every frame by using FCS.
March, 2008
Inha Univ.Slide 4
doc.: IEEE 802.15-08-0126-01-003c
Submission
Current DFx
• Section 8.7a Aggregation– Upon receiving an MSDU from FCSL, the MAC may fragment
the MSDU into subframes if the length of MSDU exceeds the pPreferred-FragmentSize as described in <xref 12.2.11.2>.
– The PHY puts the subframes together, as described in <xref 12.2.4.1.10>, to form an aggregated frame that is sent as one PHY transmission over the medium.
– The number of subframes accommodated in a single aggregated frame is contained in the PHY header as described in <xref 12.2.4.1.10>.
March, 2008
Inha Univ.Slide 5
doc.: IEEE 802.15-08-0126-01-003c
Submission
Current DFx
• 12.2.11.2 Supported fragment size encoding– The encoding of the preferred fragment size for SC mode used in
the Capability IE
March, 2008
Inha Univ.Slide 6
doc.: IEEE 802.15-08-0126-01-003c
Submission
Current DFx
• 12.2.4.1.10 Number of subframes
– The default setting of the Number of Subframes field shall be 0000 to indicate a non-aggregated frame. When not set to zero, the Number of Subframes field shall indicate the number of subframes minus one. The maximum allowed number of subframes is 16. For an aggregated frame, the frame header shall contain the base header as well as the optional header.
March, 2008
Inha Univ.Slide 7
doc.: IEEE 802.15-08-0126-01-003c
Submission
Current DFx
March, 2008
Inha Univ.Slide 8
doc.: IEEE 802.15-08-0126-01-003c
Submission
Current DFx
Fixed field:• ACK policy• PNID, DestID, SrcID, Stream index
MPDU-specific:• Frame control / retry =
retransmission policy• MSDU number = MSDU number• Fragment number = Subframe ID• Useless? FCS information
March, 2008
Inha Univ.Slide 9
doc.: IEEE 802.15-08-0126-01-003c
Submission
Review of Aggregation Process in DFx
• Prerequisites of Aggregation– ACK policy shall be the same.
• Dly-ACK, Imm/Imp-ACK or No ACK.
– All aggregated MPDUs have the same PNID, DestID, SrcID and Stream index.
• MAC header in PHY frame– One fragment control field in MAC header is not enough
for multiple fragments.• Fragment, MPDU and MAC frame have the same meaning.
– Subheader shall contain fragment control field for corresponding fragment.
March, 2008
Inha Univ.Slide 10
doc.: IEEE 802.15-08-0126-01-003c
Submission
Review of Aggregation Process in DFx
• FCS information is useless and shall be removed– Only Imm-ACK frame has no frame body, and thus no FCS.– All other frames must have FCS.– It is the task of MAC layer to decide the existence of FCS.
• Subframe ID is useless and its function shall be changed.– The “Number of subframes” field in PHY header and “Subframe length” in
subheader can assure that the aggregated MPDUs can be perfectly de-aggregated.
– Subframe ID has its meaning in PHY layer, however it is used to realize some functions of ACK and fragment which are in fact tasks of MAC layer.
– It shall be changed to support fragmentation control that is missed in current aggregation process.
– Instead, the “fragment number” shall be used and the length of this field shall be 7 bits.
– Moreover, a whole “Fragmentation control” (3 octets) shall be added in subheader.
March, 2008
Inha Univ.Slide 11
doc.: IEEE 802.15-08-0126-01-003c
Submission
Modified Aggregation Process
• Aggregation is one of PHY functions.
• Transparent to MAC layer
• Fragmentation control field of every MPDU is maintained.
March, 2008
Inha Univ.Slide 12
doc.: IEEE 802.15-08-0126-01-003c
Submission
Current DFx
• MAC performs fragmentation, so the fragmentation control field is necessary to every fragment, but there is only one MAC header in the flowchart.
• The size of MSDU block is misleading.
March, 2008
Inha Univ.Slide 13
doc.: IEEE 802.15-08-0126-01-003c
Submission
Current DFx
March, 2008
Inha Univ.Slide 14
doc.: IEEE 802.15-08-0126-01-003c
Submission
New Proposal of Aggregation at source
MAC
PHY
Packet#1Packet#2Packet#3…...
MSDU#1MSDU#2
Fragmentation 1MSDU#2
Fragmentation 2MSDU#3
MSDU#1FCS
MACHeader
MPDU#1
MSDU#2Fragmentation 1
FCS
MACHeader
MPDU#2
MSDU#2Fragmentation 2
FCS
MACHeader
MPDU#3
MSDU#3FCS
MACHeader
MPDU#4
Fragmentation
…...
…...
MPDU#1(without header)
HCS
Common
MACHeader
PHYHeader
Opt.
HCS
Subheaders
MPDU#2(without header)
MPDU#3(without header)
MPDU#4(without header)
PHYHeader
PHYHeader
MSDU#1FCS
MACHeader
MSDU#2Fragmentation 1
FCS
MACHeader
MSDU#2Fragmentation 2
FCS
MACHeader
MSDU#3FCS
MACHeader
Common
MACHeader
Indicate information of subheader existence
Extract subheaders
Aggregated MPDUs
Upper Layer
March, 2008
Inha Univ.Slide 15
doc.: IEEE 802.15-08-0126-01-003c
Submission
New PHY frame formatting of Aggregation
From MAC via PHY SAP FCS + frame payload #2 MAC header #2
Concatenate subheaders as MAC subheader PHY header
FCS + frame payload #1 MAC header #1
… … … …
CommonMAC headerConvert each MAC header to subheader subheader #2
subheader #1
Calculate and insert optional HCS
CommonMAC header
Form common MAC header
Add PHY headerMAC subheader
Calculate and insert HCSPHY headerCommon
MAC headerMAC subheader HCS
opt.HCS
PHY headerCommon
MAC headerMAC subheader HCS
opt.HCS
FCS + frame payload #1FCS + frame payload #2… …
Aggregate multiple frames
March, 2008
Inha Univ.Slide 16
doc.: IEEE 802.15-08-0126-01-003c
Submission
MAC Header and Subheader
• Method 1: “Common” MAC header– “Common” MAC header contains PNID, DestID, SrcID and
Stream index. The Fragmentation Control field is useless.– Each subheader contains fragment information.– There are 1 MAC header and n subheaders.
• n: number of subframes
• Method 2: MAC header of 1st MPDU– MAC header is exactly the MAC header of 1st MPDU to be
aggregated in one PHY frame.– Subheaders are the simplified MAC headers of the rest MPDUs
that are aggregated after the 1st one.– There are 1 MAC header and (n – 1) subheaders.
• Note– It should be consistent with PHY frame without aggregation.
March, 2008
Inha Univ.Slide 17
doc.: IEEE 802.15-08-0126-01-003c
Submission
Summary of Aggregation Process • Aggregation shall be regarded as a PHY enhancement
– MAC header and subheader extraction• MAC header compression, a new term?
– Transparent to MAC layer: make clear the concept of layered protocol stack• It is the whole MPDU (not so-called “subframe”) that passes through the PHY SAP.• Compatible with 802.15.3 & 3b: Fragmentation control is necessary to every MPDU
• More suitable to Dly-ACK procedure– MPDU ID in Dly-ACK frame just is the fragmentation control information.
– ACK the aggregated MPDUs• Burst size = n x number of MPDU aggregated in one PHY frame
March, 2008
Inha Univ.Slide 18
doc.: IEEE 802.15-08-0126-01-003c
Submission
MAC header compression
• PHY gets multiple MPDUs via PHY SAP.• PHY separates MAC header from frame payload
(with FCS).• PHY converts multiple MAC headers into one
(common) MAC header and several subheaders.– Subheader has less number of octets than MAC header.
• MAC header decompression just is the reverse process.
