IEEE P802.11
Wireless LANs
Comment Resolutions on DL MU Operation 	
Date:  2016-09-14	
Author(s):	
Name	Affiliation	Address	Phone	email	
Simone Merlin	Qualcomm, Inc.	5775 Morehouse Dr.
San Diego, CA 92121	+1.858.845.1243	smerlin@qti.qualcomm.com	
Alfred Asterjadhi					
Raja Banerjea					
George Cherian					
Abhishek Patil					
Tomo Adachi	Toshiba				
Resolution for CIDs:
32, 33, 169, 221, 250, 427, 429, 753, 754, 755, 756, 950, 1502, 1503, 1504, 1505, 1506, 1508, 1801,    1901, 1902, 1903, 2320, 2467, 2632, 2633, 2634, 2635

CID	Commenter	Comment	Proposed Change	Resolution	
32	Ahmadreza Hedayat	"The frame type and address type (unicast, groupcast) of MPDUs may be different across A-MPDUs within a same HE MU PPPDU." This sentence is not clear. There are restrictions in the number of payloads addressed to a given STA, and this sentence seems to ignore such restriction.	Fix this statement such that it reflects the restriction on the maximum one payload for a given STA in a DL MU PPDU.	Reject.
The PHY only allows to allocate one RU to a STA. The resource unit carries a PSDU which includes the A-MPDU for the STA. That is ‘one payload’ per STA 

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33	Ahmadreza Hedayat	The word "groupcast RU" has been mentioned in the spec only once and in this sentence, and without a prior definition: "A groupcast frame in a groupcast RU of an HE MU PPDU shall not include information intended for a STA that is identified as the recipient of another RU in the same HE MU PPDU". There is no definition of groupcast RU in the SFD.	Remove the reference to groupcast RU. Suggestion: "A groupcast frame in an HE MU PPDU shall not include information intended for a STA that is identified as the recipient of another RU in the same HE MU PPDU."	Revised. PHY defines a “STAID for Broadcast” in SIG-B per user info. 

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169	Alfred Asterjadhi	These fields (DL OFDMA Capable, and DL MU MIMO Capable) are not defined anywhere in the HE Capabilities element. Eventually remove these two paragraphs (2nd and 3rd). Similar observation (though may be with a different resolution) for the statements in P74L56-60 (UL MU counterparts).	As in comment.	Revised

Defined capabilities

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221	Alfred Asterjadhi	An AP shall not transmit to a STA an HE MU PPDU with the HE-SIG-B allocating more than one RUs (see 26.3.9.8.3 (Time domain encoding)), unless the STA set the DL OFDMA Capable subfield of the HE Capabilities element to 1.
DL - OFDMA is mandatory, change text accordingly	As in comment.	Revised. 

Removed sentence since DL OFDMA is mandatory 

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250	Anton Kiryanov	The meaning is not clear. The intension is that an AP shall not allocate OFDMA-RUs to the STA that is not OFDMA capable? For such a STA an AP can allocate the whole channel (e.g. 20 MHz channel)	Rewrite according to the comment	Revised. Removed sentence as OFDMA is mandatory 

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427	Brian Hart	"is based on" is vague	"follows ... with the following exceptions"	Revised. Unnecessary sentence. All A-MPDUs follow the rules of the A-MPDU context.

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429	Brian Hart	for a STA	fro a STA or group of STAs (assuming two groupcast RUs for disjoint STA subsets are allowed at the same time .. which they should be)	Reject. Currently there is only support for one Broadcast RU and there can be only one. 
	
753	Jarkko Kneckt	What is a frame type? Is it PPDU type, MPDU type or something else	Clarify what is a frame type.	Revised. ‘Frame type’ is the frame type. Added also subtype

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754	Jarkko Kneckt	Unicast and group cast are L3 and above concepts. MAC layer should talk about MAC address individual/group bit settings.	Change from unicast and groupcast to talk about individual/group addressing of the MAC address.	Revised

Changed

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755	Jarkko Kneckt	Groupcast RU is not defined.	Define groupcast RU concept and rules how it is used.	Revised

The PHY section refers to an RU allocated to a “STAID for Broadcast”. I used that terminology

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756	Jarkko Kneckt	Can groupcast RU contain also individually addressed frames? For instance to a receiver of the group addressed frames	Define groupcast RU concept and rules how it is used.	Revised

The PHY section refers to an RU allocated to a “STAID for Broadcast”. I used that terminology

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950	Junichi Iwatani	In the current draft specification, if a non-HE (lagacy) transmission uses the primary channel (20MHz or 40MHz), the secondary channels (up to 140MHz) are not available for HE transmissions. This is a waste of frequency resources and degrades the performance when non-HE STAs and HE-STAs coexist. This problem should be solved since non-HE STAs may be used for many years especially for home appliances.	For the better utilization of the frequency channels, the 11ax specifications should have a mechanism that allows a non-HE transmission and HE transmissions at the same time, at least for DL transmissions from an HE-AP.	[commenter will provide resolution] 	
1502	Mark RISON	"An AP shall not transmit to a STA an HE MU PPDU with the HE-SIG-B allocating more than one RUs (see 26.3.9.8.3 (Time domain encoding)), unless the STA set the DL OFDMA Capable subfield of the HE Capabilities element to 1." -- why can't it use DL MU-MIMO?	Restrict the restriction to the frequency domain	Revised. Removed the sentence

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1503	Mark RISON	It says "the STA set"	Change to "the STA sets"	Revised. Sentence was removed

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1504	Mark RISON	It says "the STA set"	Change to "the STA sets"	Accept 

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1505	Mark RISON	"the DL OFDMA Capable subfield of the HE Capabilities element" -- there is no such subfield	Refer to a subfield that exists	Revised, Removed the sentence since the feature is mandatory

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1506	Mark RISON	"the DL MU MIMO Capable subfield of the HE Capabilities element" -- there is no such subfield	Refer to a subfield that exists	Revised

Added capability

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1508	Mark RISON	"in an HE MU PPDU in either DL OFDMA or DL MU MIMO" -- can't it be both?	Delete "in either DL OFDMA or DL MU MIMO"	Accept	
1801	Robert Stacey	DL MU capability signaling is not present in HE Capabilities element. References are made to a DL OFDMA Capable subfield and a DL MU MIMO Capable subfield which do not exist. The VHT Capability element includes MU capability as well and the relationship between VHT capability and HE capability is not clear.	Add MU capability signaling to HE Capabilities element. Define what they mean for AP and non-AP STA. Define relationship (setting) wrt VHT Capabilities.	Revised. Added capability. HE and VHT DL MU operation are independently defined and have independent capabilities

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1901	Sigurd Schelstraete	Missing subfield in HE Capabilities element	Text refers to "DL OFDMA Capable subfield of the HE Capabilities element". No such subfield is currently defined. Add appropriate subfield in HE Capabilities element.	Revised. Removed sentence

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1902	Sigurd Schelstraete	Missing subfield in HE Capabilities element	Text refers to "DL MU MIMO Capable subfield of the HE Capabilities element". No such subfield is currently defined. Add appropriate subfield in HE Capabilities element.	Revised

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1903	Sigurd Schelstraete	"shall end at the same time" is ambiguous	There is only one transmission, even if the PPDU format is MU. Propose to clarify that the data of all users is padded to fill the same number of symbols.	Revised

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2320	Yasuhiko Inoue	In the current draft specification, if a non-HE transmission uses the primary channel (20MHz or 40MHz), the secondary channels are not available for HE transmissions. This is a waste of frequency resources and degrades the system level performance. It is necessary to solve this problem since non-HE (legacy) STAs will be used for many years.	For the better utilization of the frequency channels, the 11ax specifications should have a mechanism that allows a non-HE transmission and HE transmissions at the same time (at least for DL transmissions from an HE-AP).	[commenter will provide resolution] 	
2467	Yongho Seok	According to the following STA-ID definition (refer Table 26-19) in an HE DL MU PPDU ,
"For single BSS AP, the STA-ID for Broadcast will be 0;
For Multiple BSS AP, the STA-ID for Broadcast to a specific BSS will follow the group addressed AID assignment in the TIM according to the existing Multi-BSSID TIM operation;
For Multiple BSS AP, the STA-ID for Broadcast to all BSS of the AP will have a special STAID value reserved."

It seems that the number of the groupcat RU in an HE MU PPDU has limited as the following:
For single BSS AP, the number of the groupcat RU in an HE MU PPDU is limited to one;
For Multiple BSS AP, the number of the groupcat RU in an HE MU PPDU is limited to the number of the multiple BSSs;

Specify a constraint for number of the groupcat RU in an HE MU PPDU.	As per comment		
2632	Young Hoon Kwon	It is not clear if an AP can transmit a DL MU PPDU in a TXOP that is obtained from a non-AP STA. For example, when a STA obtains a TXOP by sending frames to the serving AP, it is not clear if the AP is allowed to send DL MU PPDU as a response to the UL frame.	As mentioned in the comment, clarify if an AP is allowed to send a DL MU PPDU in a TXOP that is obtained from a non-AP STA.	Reject. 
The STA is the owner of the TXOP. allowing MU PPDU from the AP  in response to the STA will results in multiple possible response types and durations which the STA cannot predict and hence cannot manage properly in term e.g. of NAV settings.	
2633	Young Hoon Kwon	This is not enough. Rules for allocating RUs to a STA needs to be described. For example, an AP shall not allocate more than one RU to a STA within a DL MU PPDU.	Add the following text after 3rd paragraph: "An AP shall not allocate more than one RUs to a STA within a DL MU PPDU. If an AP allocates RUs for unicast traffic and broadcast/multicast traffic simultaneously, the target STA for the unicast traffic may ignore RUs for broadcast/multicast traffic."	Revised

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2634	Young Hoon Kwon	DL MU MIMO Capable  and DL OFDMA capable subfields are not defined in HE Capabilities element in subclause 9.4.2.213.	Define DL MU MIMO Capable and DL OFDMA subfields in HE Capabilities element in subclause 9.4.2.213.	Revised

Defined DL MU MIMO. DL OFDMA is mandatory

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2635	Young Hoon Kwon	Definition for transmission success in case of DL MU transmission needs to be described in this sub-clause, which has been accepted in the SFD.	Add the following text at the end of the sub-clause: "When an AP initiates a DL MU transmission soliciting more than one immediate response frames, the DL MU transmission is successful if the AP receives the response frame correctly from at least one STA indicated by any trigger information in the DL MU transmission.".	Revised. Definition of successful need to be put in the right context with a related behavior. I assume the usage of this ‘successful’ definition is for TXOP continuation,  The text was already added in resolution of comments   (#593 1530 2631)  (#39) .(#1531)	

1905	Sigurd Schelstraete	25.5.2.1	Missing subfield in HE Capabilities element	Text refers to "UL MU MIMO Capable subfield of the HE Capabilities element". No such subfield is currently defined. Add appropriate subfield in HE Capabilities element.	Revised	

Please modify section 25.5.1 as follows

25.5.1 	HE DL MU operation
25.5.1.1 	General
HE DL MU operation allows an AP to transmit simultaneously to one or more non-AP STAs in DL OFDMA, DL MU-MIMO or both.
 (#221,250, 1502, 1505, 1901)
An AP shall not transmit to a STA an(#2829) HE MU PPDU with the HE-SIG-B allocating, in an RU, spatial streams to more than one recipient STA, unless the STA sets the Downlink MU-MIMO on Partial Bandwidth Rx #1507) Capable subfield of the HE Capabilities element to 1.
The transmission of each RU in an HE MU PPDU (#1507, 1508) shall be padded to end at the same time, indicated by the L-SIG field as described in 26.3.9.5 (L-SIG). (#1903)
The padding procedure for each A-MPDU in an HE MU PPDU is defined in 25.10.3
25.5.1.2 	HE MU PPDU payload
(#427)The frame type, subtype subfields in the frame control field (#753) and the receiver address type (individually addressed or group addressed(#1509)) in MPDUs may be different across A-MPDUs in different RUs within a same HE MU PPDU(#598).An AP shall not set more than one STA-ID in the HE-SIG-B to indicate the same value. If an AP sets one of the STA-ID in the HE-SIG-B to match the AID of a non-AP STA, then the non-AP STA may disregard any RU allocated to a STAID for Broadcast within the same DL MU PPDU. (#2633)
An MPDU(#1510) sent in an RU of an HE MU PPDU that is allocated to a STAID for Broadcast, (#33, 754, 755, 756) hall not include information intended for a STA that is identified as the recipient of another RU in the same HE MU PPDU.

Change the capability element 

B1	B2-3	B4	B5	B6	B7-8	B9-15	
Downlink MU-MIMO on Partial Bandwidth Rx	UL MU MIMO	PPE Thresholds Present	TWT Requester Support	TWT Responder Support	Fragmentation Support	Reserved	
1	2	1	1	1	2	11(#725)	
Figure 9-ax2—		Figure 9-ax2—		Figure 9-ax2—	HE Capabilities Information field format	

Downlink MU-MIMO on Partial Bandwidth Rx field indicates support by a non-AP STA to receive an MU-MIMO transmission on an MU in an HE MU PPDU where the RU does not span the entire PPDU bandwidth . The field is set to 1 if the STA supports the reception and is set to 0 otherwise. 
B1 of the UL MU MIMO subfield indicates the STA supports transmission of full bandwidth UL MU-MIMO transmission 
B2 of the UL MU MIMO subfield indicates the STA supports transmission of UL MU-MIMO transmission on an RU in an HE MU PPDU where the RU does not span the entire PPDU bandwidth.

For reference only (from resolution of #2535 in a separate document),

A DL MU PPDU may carry PSDUs addressed to multiple recipients, hence multiple frame exchenges are performed simultaneously.  If at least one of those frame exchanges requires an immediate response (i.e. AP includes at least one Trigger Freame or UL MU Schduling indication) and if AP receives an immediate response with at least one correct MPDU from at least one of the solicited STAs, the rules referred to a successful frame exchange defined in this clause apply.  (#593 1530 2631)  (#39) .(#1531)