Presentation on theme: "Doc.: IEEE 802.15-08-0126-01-003c Submission March, 2008 Inha Univ.Slide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)"— Presentation transcript:
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 1 Project: IEEE P 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, , Republic of Korea] Voice: , FAX: , 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 c standard] Notice: This document has been prepared to assist the IEEE P 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 P
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 2 Overview Review of Aggregation Process –Current Draft (DFx): New Proposal of Aggregation Process –Modified Aggregation Process –New PHY frame formatting
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 3 Review of Aggregation Process in DFx Incompatible with & 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.
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 4 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. –The PHY puts the subframes together, as described in, 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.
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 5 Current DFx Supported fragment size encoding –The encoding of the preferred fragment size for SC mode used in the Capability IE
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 6 Current DFx 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.
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 7 Current DFx
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 8 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
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 9 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.
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 10 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.
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 11 Modified Aggregation Process Aggregation is one of PHY functions. Transparent to MAC layer Fragmentation control field of every MPDU is maintained.
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 12 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.
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 13 Current DFx
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 14 New Proposal of Aggregation at source
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 15 New PHY frame formatting of Aggregation
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 16 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 1 st MPDU –MAC header is exactly the MAC header of 1 st MPDU to be aggregated in one PHY frame. –Subheaders are the simplified MAC headers of the rest MPDUs that are aggregated after the 1 st one. –There are 1 MAC header and (n – 1) subheaders. Note –It should be consistent with PHY frame without aggregation.
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 17 Summary of Aggregation Process Aggregation shall be regarded as a PHY enhancement –Rearrange section 8.7a to section PHY frame format Frame Header –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 & 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
doc.: IEEE c Submission March, 2008 Inha Univ.Slide 18 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.