TWG-2011-0042-Xx-Generalized Usage of More Data Field

June 2011 doc.: 11-11-0859-00-00ad-MoreData_field.docx

1 IEEE P802.11 2 Wireless LANs

11-11-0859-00-00ad-MoreData_field

Date: 09 June 2011

Author(s): Name Affiliation Address Phone email Payam Broadcom 5300 California Ave. +1 949-926-6840 [email protected] Torab Corporation Irvine, CA 92617 3

page 1 Payam Torab, Broadcom

June 2011 doc.: 11-11-0859-00-00ad-MoreData_field.docx

1 Problem Statement 2 3 This document provides an improved usage of the “More Data” bit in the Frame Control field that results in 4 better utility for the bit in DBand. A DBand STA sets the bit to 1 in any frame it sends out simply if it has data 5 to send during the same SP/TXOP. The information that the other end has “qualified” data to send (e.g., data 6 frames belonging to a TSPEC mapped to the same SP) can be used to grant an RD for example, or to 7 dynamically adjust the SP duration. 8 9 A closely related problem – the absence of an appropriate More PPDU bit in control response frames in 10 DBand to indicate More PPDU in response to an RD grants - is also resolved. As shown in the diagram 11 below, a DBand RD grantee that is also required to send a control response frame such as an Ack or Block 12 Ack, currently does not have a direct way of setting More PPDU to 1 to accept the RD grant (control response 13 frames do not have a QoS Control header, and control wrapper frames are not supported in DBand) – the 14 grantee either has to aggregate a QoS frame (including QoS Null) to be able to tell More PPDU = 1. 15 Aggregating control response and data farmes may not be desirable all the time. Aggregating something as 16 simple as a QoS Null has a performance penalty too, because the aggregate is subject to the minimum MPDU 17 start spacing (density spacing). The simpleset solution is to exempt QoS null frames from density spacing. 18 This is particularly justified given that density spacing was introduced to satisfy decryption speed limits from 19 one MPDU to the next in the aggregate, and since QoS Null frames have no payload they obviously do not go 20 through encryption/decryption. 21 22

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2 June 2011 doc.: 11-11-0859-00-00ad-MoreData_field.docx

1 8.2.4.1.8 More Data field 2 Editor instruction: change this subclause as follows 3 4 The More Data field is 1 bit in length and is used differently in the OBand and in the DBand. 5 6 In the OBand, the More Data field is used as follows: 7 8 ─ It is used to indicate to a STA in PS mode that more MSDUs, A-MSDUs, or MMPDUs are buffered 9 for that STA at the AP. The More Data field is valid in directed data or management type frames 10 transmitted by an AP to a STA in PS mode. A value of 1 indicates that at least one additional buffered 11 MSDU, A-MSDU, or MMPDU is present for the same STA. 12 13 ─ In the OBand, Tthe More Data fieldIt is optionally set to 1 in directed data type frames transmitted by 14 a CF-Pollable STA to the PC in response to a CF-Poll to indicate that the STA has at least one 15 additional buffered MSDU available for transmission in response to a subsequent CF-Poll. 16 17 ─ In the OBand, F f For a STA in which the More Data Ack subfield of its QoS Capability element is 1 18 and that has APSD enabled, an AP optionally sets the More Data field to 1 in ACK frames to this STA 19 to indicate that the AP has a pending transmission for the STA. 20 21 ─ In the OBand, Tthe More Data fieldIt is set to 0 in all other directed frames. 22 23 ─ The More Data fieldIt is set to 1 in group addressed frames transmitted by the AP when additional 24 group addressed MSDUs or MMPDUs remain to be transmitted by the AP during this beacon interval. 25 The More Data field is set to 0 in group addressed frames transmitted by the AP when no more group 26 addressed MSDUs or MMPDUs remain to be transmitted by the AP during this beacon interval. and In 27 the OBand, the More Data field is set to 0 and in all group addressed frames transmitted by non-AP 28 STAs. 29 30 In the DBand, a non-PCP/non-AP STA may set the More Data field to 1 when additional MSDUs remain to 31 be transmitted upon the end of a scheduled SP. The More Data field is set to 0 when no additional MSDUs 32 remain to be transmitted upon the end of a scheduled SP. 33 In the DBand, the More Data field is used as follows: 34 35 ─ In directed frames, it is set to 1 to indicate that the STA has MSDUs or A-MSDUs buffered for 36 transmission to the frame recipient during the same SP/TXOP. 37 38 ─ It is set to 1 in group addressed frames transmitted by the AP when additional group addressed 39 bufferable units (BUs) remain to be transmitted by the AP during this beacon interval. The More Data 40 field is set to 0 in group addressed frames transmitted by the AP when no more group addressed BUs 41 remain to be transmitted by the AP during this beacon interval. 42 43 A DBand STA does not set the More Data bit to 1 if it does not have any MSDUs or A-MSDUs buffered for 44 transmission to the frame recipient during the same SP/TXOP.

45 9.12.3 Minimum MPDU Start Spacing 46 page 1 Payam Torab, Broadcom

June 2011 doc.: 11-11-0859-00-00ad-MoreData_field.docx

1 Editor instruction: change the first paragraph as follows 2 3 An HT STA and a DBand STA shall not start the transmission of more than one MPDU within the time limit 4 described in the Minimum MPDU Start Spacing field declared by the intended receiver. To satisfy this 5 requirement, the number of octets between the start of two consecutive MPDUs in an A-MPDU, measured at 6 the PHY SAP, shall be equal or greater than 7

8 tMMSS × r/8 9 10 where 11 tMMSS is the time (in microseconds) defined in the “Encoding” column of Table 8-123 (Subfields of the 12 A-MPDU Parameters field) for an HT STA and of Error: Reference source not found for a DBand 13 STA for the value of the Minimum MPDU Start Spacing field 14 r is the value of the PHY Data Rate (in megabits per second) defined in clause Error: Reference source 15 not found for a DBand STA and for an HT STA defined in 19.6 (Parameters for HT MCSs) based on 16 the TXVECTOR parameters: MCS, GI_TYPE, and CH_BANDWIDTH 17 18 In DBand, QoS Null frames are not subject to this spacing, i.e., no extra octets are needed before QoS Null 19 frames.