IEEE P802.11
Wireless LANs
SU-MIMO beamforming optimization	
Date:  2017-12-6	
Author(s):	
Name	Affiliation	Address	Phone	email	
Lei Huang	Panasonic			lei.huang@sg.panasonic.com	
Motozuka Hiroyuki	Panasonic				

Abstract

This submission proposes to optimize the MIMO phase of SU-MIMO beamforming in case of both initiator and responder have antenna pattern reciprocity. In addition, this submission fixes some bugs and add some clarifications in the current 11ay draft specification.

Discussion: 

•	Antenna pattern reciprocity has been used by MU-MIMO BF protocol to shorten MU-MIMO BF training time. Similarly, antenna pattern reciprocity can also be used by SU-MIMO BF protocol to shorten SU-MIMO BF training time.

•	We proposed the MIMO phase of SU-MIMO BF consists of a non-reciprocal MIMO phase or a reciprocal MIMO phase. The reciprocal MIMO phase makes full use of antenna pattern reciprocity of both initiator and responder.

Proposed changes to D1.0:

1.	Modify the Table 9 as follows:

Table 9—MIMO Setup Control element format
Field	Size (bits)	Meaning	
Element ID	8		
Length	8		
Element ID Extension	8		
SU/MU	1	Sets to 1 to indicate SU-MIMO beamforming and sets to 0 to indicate MU-MIMO beamforming.	
Non-reciprocal/Reciprocal SU-MIMO Phase	1	Sets to 1 to indicate the non-reciprocal MIMO phase and sets to 0 to indicate the reciprocal MIMO phase. This field is reserved when the SU/MU field is set to 0.	
EDMG Group ID	8	Indicates the EDMG Group ID of target MU group. This field is reserved when the SU/MU field is set to 1.	
Group User Mask	32		
DL/UL MU-MIMO Phase	1	Set to 1 to indicate downlink MIMO phase and sets to 0 to indicate uplink MIMO phase. This field is reserved when the SU/MU field is set to 1.	
L-TX-RX	8	Indicates the requested number of consecutive TRN-Units in which the same AWV is used in the transmission of the last M TRN subfields of each TRN-Unit. This field is reserved when the SU/MU field is set to 0.	
Requested EDMG TRN-Unit M	4	The value of this field plus one indicates the requested number of TRN subfields in a TRN-Unit transmitted with the same AWV following a possible AWV change. This field is reserved when the SU/MU field is set to 0.	
Link Type	1	Sets to 1 to indicate initiator link and set to 0 otherwise. This field shall be set to 1 when the SU/MU field is set to 0.	
MIMO FBCK-REQ	10	Indicates channel measurement feedback requested for the link specified by the Link Type field.	
Reserved	6		

2.	Modify the clause 10.38.9.2.2.3 as follows:

10.38.9.2.2.3 MIMO phase
10.38.9.2.2.3.1 General 

The MIMO phase enables the training of transmit and receive sectors and DMG antennas to determine best combinations of transmit and receive sectors and DMG antennas for SU-MIMO operation. The initiator shall start the MIMO phase an MBIFS following the end of the SISO phase. 

The MIMO phase consists of a non-reciprocal MIMO phase or of a reciprocal MIMO phase.  

The non-reciprocal MIMO phase and the reciprocal MIMO phase shall be supported by all EDMG STAs that are SU-MIMO capable. 

10.38.9.2.2.3.2 Non-reciprocal MIMO phase

The non-reciprocal MIMO phase is shown in Figure 99 and consists of four subphases: an SU-MIMO BF setup subphase, an initiator SU-MIMO BF training (SMBT) subphase, a responder SMBT subphase, and an SU-MIMO BF feedback subphase. Each subphase shall be separated by an MBIFS.

Figure 99—The non-reciprocal MIMO phase of the SU-MIMO beamforming

It is mandatory to perform the SU-MIMO BF setup subphase. 
In the SU-MIMO BF setup subphase, the initiator shall send a MIMO BF Setup frame with the SU/MU field set to 1, the Non-reciprocal/Reciprocal SU-MIMO Phase field set to 1 and the Link Type field set to 1 to the responder. In case of channel aggregation, the Aggregation Requested subfield of the MIMO FBCK-REQ field in the MIMO BF Setup frame should set to 1. The TA field and the RA field of the MIMO BF Setup frame shall be set to the MAC addresses of the initiator and the responder, respectively. The MIMO BF Setup frame shall indicate a unique dialog token in the Dialog Token field for identifying SU-MIMO BF training and the number of transmit sector combinations requested for the initiator link () in the Number of TX Sector Combinations Requested subfield of the MIMO FBCK-REQ field. The MIMO BF Setup frame shall also indicate whether time domain channel response is requested as part of SU-MIMO BF feedback in the Channel Measurement Requested subfield of the MIMO FBCK-REQ field. If the time domain channel response is requested as part of SU-MIMO BF feedback, the Channel Measurement Requested subfield of the MIMO FBCK-REQ field shall be set to 1 and the Number of Taps Requested subfield of the MIMO FBCK-REQ field shall indicate the number of channel taps requested in time domain channel response. The L-TX-RX field and the Requested EDMG TRN-Unit M field of the MIMO BF Setup frame shall indicate the number of TRN subfields requested for receive AWV training in the following responder SMBT subphase. Additionally, based on the SNRs of the transmit sectors collected from the responder in the SISO phase, the initiator may select a subset of candidate transmit sectors per DMG antenna to reduce the initiator SMBT training time. Each DMG antenna should have the similar number of candidate transmit sectors in order to avoid biasing a DMG antenna. 
Note: If the initiator has antenna pattern reciprocity, the subset of candidate transmit sectors per DMG antenna selected by the initiator for the initiator SMBT subphase can also be used to reduce the number of TRN subfields required for receive AWV training in the following responder SMBT subphase. 
The responder shall send a MIMO BF Setup frame with the SU/MU field set to 1, the Non-reciprocal/Reciprocal SU-MIMO Phase field set to 1 and the Link Type field set to 0 a SIFS following the reception of the MIMO BF Setup frame from the initiator. In case of channel aggregation, the Aggregation Requested subfield of the MIMO FBCK-REQ field in the MIMO BF Setup frame should set to 1. The TA field and the RA field of the MIMO BF Setup frame shall be set to the MAC address of the responder and the initiator, respectively. The MIMO BF Setup frame shall indicate a unique dialog token in the Dialog Token field for identifying SU-MIMO BF training and the number of transmit sector combinations requested for the responder link () in the Number of TX Sector Combinations Requested subfield of the MIMO FBCK-REQ field. The MIMO BF Setup frame shall also indicate whether time domain channel response is requested as part of SU-MIMO BF feedback in the Channel Measurement Requested subfield of the MIMO FBCK-REQ field. If the time domain channel response is requested as part of SU-MIMO BF feedback, the Channel Measurement Requested subfield of the MIMO FBCK-REQ field shall be set to 1 and the Number of Taps Requested subfield of the MIMO FBCK-REQ field shall indicate the number of channel taps requested in time domain channel response. The L-TX-RX field and the Requested EDMG TRN-Unit M field in the MIMO BF Setup frame shall indicate the number of TRN subfields requested for receive AWV training in the following initiator SMBT subphase. Additionally, based on the SNRs of the transmit sectors collected from the initiator in the SISO phase, the responder may select a subset of candidate transmit sectors per DMG antenna to reduce the responder SMBT training time. Each DMG antenna should have the similar number of candidate transmit sectors in order to avoid biasing a DMG antenna. 
Note: If the responder has antenna pattern reciprocity, the subset of candidate transmit sectors per DMG antenna selected by the responder for the responder SMBT subphase can also be used to reduce the number of TRN subfields required for receive AWV training in the following initiator SMBT subphase
All frames transmitted during the MIMO BF setup subphase should be sent using the DMG control mode or using a non-EDMG duplicate PPDU transmitted with the DMG Control modulation class. 
The initiator shall initiate the initiator SMBT subphase an MBIFS following the reception of the MIMO BF Setup frame from the responder. In the initiator SMBT subphase, the initiator shall transmit EDMG BRP-RX/TX packets to the responder. Each EDMG BRP-RX/TX packet shall be separated by SIFS. Each transmitted EDMG BRP-RX/TX packet is used to train one or more transmit sectors and, for each transmit sector, a number of receive AWVs. In each EDMG BRP-RX/TX packet, the initiator shall include, for each selected transmit sector, TRN subfields in the TRN field of the PPDU for the responder to perform receive AWV training. For each EDMG BRP-RX/TX packet, the TXVECTOR parameter EDMG_TRN_LEN shall be set to a value greater than zero, and the parameters RX_TRN_PER_TX_TRN and EDMG_TRN_M shall be set to the values of the L-TX-RX and Requested EDMG TRN-Unit M fields in the MIMO BF Setup frame received from the responder, respectively. The initiator may transmit each EDMG BRP-RX/TX packet to train multiple TX DMG antennas simultaneously by using the TRN subfields defined in 30.9.2.2.6 and, therefore, reduce training time. The TX Antenna Mask field of each EDMG BRP-RX/TX packet shall indicate the TX DMG antenna(s) which is being used by the initiator to transmit the EDMG BRP-RX/TX packet. The BRP CDOWN field of each EDMG BRP-RX/TX packet shall indicate the number of remaining EDMG BRP RX/TX packets to be transmitted by the initiator in the initiator SMBT subphase. 
The responder shall initiate the responder SMBT subphase an MBIFS following the reception of an EDMG BRP-RX/TX packet with the BRP CDOWN field set to 0 from the initiator. In the responder SMBT subphase, the responder shall transmit EDMG BRP-RX/TX packets to the initiator. Each EDMG BRP-RX/TX packet shall be separated by SIFS. For each EDMG BRP-RX/TX packet, the TXVECTOR parameter EDMG_TRN_LEN shall be set to a value greater than zero, and the parameters RX_TRN_PER_TX_TRN and EDMG_TRN_M shall be set to the values of the L-TX-RX and Requested EDMG TRN-Unit M fields in the MIMO BF Setup frame received from the initiator in the SU-MIMO BF setup subphase, respectively. The responder may transmit each EDMG BRP-RX/TX packet to train multiple TX DMG antennas simultaneously by using the TRN subfields defined in 30.9.2.2.6 and, therefore, reduce training time. The TX Antenna Mask field of each EDMG BRP-RX/TX packet shall indicate the TX DMG antenna(s) which is being used by the responder to transmit the EDMG BRP-RX/TX packet. The BRP CDOWN field of each EDMG BRP-RX/TX packet shall indicate the number of remaining EDMG BRP RX/TX packets to be transmitted by the responder in the responder SMBT subphase. 
The initiator shall initiate the SU-MIMO BF feedback subphase an MBIFS following the reception of an EDMG BRP-RX/TX packet with the BRP CDOWN field set to 0 from the responder. All frames transmitted during the SU-MIMO BF feedback subphase should be sent using the DMG control mode. In the SU-MIMO BF feedback subphase, the initiator shall send to the responder a MIMO BF Feedback frame with the SU/MU field set to 1 and the Link Type field set to 0. In case of channel aggregation, the Aggregation Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame should be set to 1. The TA field of the MIMO BF Feedback frame shall be set to the MAC address of the initiator and the RA field shall be set to the MAC address of the responder. The MIMO BF Feedback frame shall carry the dialog token in the Dialog Token field that identifies the SU-MIMO BF training. The Number of TX Sector Combinations Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame indicates the number of best transmit sector combinations, , recommended by the initiator for responder link. The EDMG Channel Measurement Feedback element in the MIMO BF Feedback frame shall indicate  best transmit sector combinations in the EDMG Sector ID Order field and the BRP CDOWN field, which are determined based on channel measurement data captured from the responder SMBT subphase. The Channel Measurement Feedback element in the MIMO BF Feedback frame shall contain SNRs corresponding to the  transmit sector combinations in the SNR field. If the Channel Measurement Requested subfield of the MIMO FBCK-REQ field in the MIMO BF Setup frame received from the responder in the preceding SU-MIMO BF setup subphase is 1, the Channel Measurement Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame shall be set to 1 and the Channel Measurement Feedback element in the MIMO BF Feedback frame shall contain channel measurements corresponding to the  transmit sector combinations in the Channel Measurement field. If the Tap Delay Requested subfield of the MIMO FBCK-REQ field in the MIMO BF Setup frame received from the responder in the preceding SU-MIMO BF setup subphase is 1, the Tap Delay Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame shall be set to 1 and the EDMG Channel Measurement Feedback element in the MIMO BF Feedback frame shall contain relative tap delays for the measurements in the Tap Delay field. 
The responder shall send a MIMO BF Feedback frame to the initiator with the SU/MU field set to 1 and the Link Type field set to 1 a SIFS following reception of a MIMO BF Feedback frame from the initiator. In case of channel aggregation, the Aggregation Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame should be set to 1. The TA field of the MIMO BF Feedback shall be set to the MAC address of the responder and the RA field shall be set to the MAC address of the initiator. The MIMO BF Feedback frame shall carry the dialog token in the Dialog Token field that identifies the SU-MIMO BF training. The Number of TX Sector Combinations Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame shall indicate the number of best transmit sector combinations, , recommended by the responder for initiator link. The EDMG Channel Measurement Feedback element in the MIMO BF Feedback frame shall indicate  best transmit sector combinations in the EDMG Sector ID Order field and the BRP CDOWN field, which are determined based on channel measurement data captured from the initiator SMBT subphase. The Channel Measurement Feedback element in the MIMO BF Feedback frame shall contain SNRs corresponding to the  transmit sector combinations in the SNR field. If the Channel Measurement Requested subfield of the MIMO FBCK-REQ field in the MIMO BF Setup frame received from the initiator in the preceding SU-MIMO BF setup subphase is 1, the Channel Measurement Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame shall be set to 1 and the Channel Measurement Feedback element in the MIMO BF Feedback frame shall contain channel measurements corresponding to the  transmit sector combinations in the Channel Measurement field. If the Tap Delay Requested subfield of the MIMO FBCK-REQ field in the MIMO BF Setup frame received from the initiator in the preceding SU-MIMO BF setup subphase is 1, the Tap Delay Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame shall be set to 1 and the EDMG Channel Measurement Feedback element in the MIMO BF Feedback frame shall contain tap delays corresponding to the  transmit sector combinations in the Tap Delay field.
The  best transmit sector combinations (or equivalently  best TX-RX AWV configurations) for the initiator link and the  best transmit sector combinations (or equivalently  best TX-RX AWV configurations) for the responder link shall be determined in such a way that no transmit or receive AWV come from the same DMG antenna. The algorithms for determining the  best transmit sector combinations for the initiator link and for determining the  best transmit sector combinations for the responder link are implementation dependent.
10.38.9.2.2.3.3 Reciprocal MIMO phase

The reciprocal MIMO phase might shorten the SU-MIMO BF training time. The initiator may initiate a reciprocal MIMO phase if the following conditions are met:
•	The SU-MIMO Supported field in initiator’s and responder’s EDMG Capabilities element equals one; and
•	The Antenna Pattern Reciprocity field in initiator’s and responder’s DMG Capabilities element equals one
The reciprocal MIMO phase is shown in Figure x and consists of three subphases: an SU-MIMO BF setup subphase, an initiator SMBT subphase and an SU-MIMO BF feedback subphase. Each subphase shall be separated by an MBIFS.

Figure x—The reciprocal MIMO phase of the SU-MIMO beamforming

It is mandatory to perform the SU-MIMO BF setup subphase. 
In the SU-MIMO BF setup subphase, the initiator shall send a MIMO BF Setup frame with the SU/MU field set to 1, the Non-reciprocal/Reciprocal SU-MIMO Phase field set to 0 and the Link Type field set to 1 to the responder. In case of channel aggregation, the Aggregation Requested subfield of the MIMO FBCK-REQ field in the MIMO BF Setup frame should set to 1. The TA field and the RA field of the MIMO BF Setup frame shall be set to the MAC addresses of the initiator and the responder, respectively. The MIMO BF Setup frame shall indicate a unique dialog token in the Dialog Token field for identifying SU-MIMO BF training and the number of transmit sector combinations requested for the initiator link () in the Number of TX Sector Combinations Requested subfield of the MIMO FBCK-REQ field. The MIMO BF Setup frame shall also indicate whether time domain channel response is requested as part of SU-MIMO BF feedback in the Channel Measurement Requested subfield of the MIMO FBCK-REQ field. If the time domain channel response is requested as part of SU-MIMO BF feedback, the Channel Measurement Requested subfield of the MIMO FBCK-REQ field shall be set to 1 and the Number of Taps Requested subfield of the MIMO FBCK-REQ field shall indicate the number of channel taps requested in time domain channel response. Additionally, based on the SNRs of the transmit sectors collected from the responder in the SISO phase, the initiator may select a subset of candidate transmit sectors per DMG antenna to reduce the initiator SMBT training time. Each DMG antenna should have the similar number of candidate transmit sectors in order to avoid biasing a DMG antenna. 
The responder shall send a MIMO BF Setup frame with the SU/MU field set to 1, the Non-reciprocal/Reciprocal SU-MIMO Phase field set to 0 and the Link Type field set to 0 a SIFS following the reception of the MIMO BF Setup frame from the initiator. The TA field and the RA field of the MIMO BF Setup frame shall be set to the MAC address of the responder and the initiator, respectively. The MIMO BF Setup frame shall indicate a unique dialog token in the Dialog Token field for identifying SU-MIMO BF training. The L-TX-RX field and the Requested EDMG TRN-Unit M field in the MIMO BF Setup frame shall indicate the number of TRN subfields requested for receive AWV training in the following initiator SMBT subphase. Based on the SNRs of the transmit sectors collected from the initiator in the SISO phase, the responder may select a subset of candidate receive sectors per DMG antenna to reduce the initiator SMBT training time. Each DMG antenna should have the similar number of candidate receive sectors in order to avoid biasing a DMG antenna.
All frames transmitted during the MIMO BF setup subphase should be sent using the DMG control mode or using a non-EDMG duplicate PPDU transmitted with the DMG Control modulation class. 
The initiator shall initiate the initiator SMBT subphase an MBIFS following the reception of the MIMO BF Setup frame from the responder. In the initiator SMBT subphase, the initiator shall transmit EDMG BRP-RX/TX packets to the responder. Each EDMG BRP-RX/TX packet shall be separated by SIFS. Each transmitted EDMG BRP-RX/TX packet is used to train one or more transmit sectors and, for each transmit sector, a number of receive AWVs. In each EDMG BRP-RX/TX packet, the initiator shall include, for each selected transmit sector, TRN subfields in the TRN field of the PPDU for the responder to perform receive AWV training. For each EDMG BRP-RX/TX packet, the TXVECTOR parameter EDMG_TRN_LEN shall be set to a value greater than zero, and the parameters RX_TRN_PER_TX_TRN and EDMG_TRN_M shall be set to the values of the L-TX-RX and Requested EDMG TRN-Unit M fields in the MIMO BF Setup frame received from the responder, respectively. The initiator may transmit each EDMG BRP-RX/TX packet to train multiple TX DMG antennas simultaneously by using the TRN subfields defined in 30.9.2.2.6 and, therefore, reduce training time. The TX Antenna Mask field of each EDMG BRP-RX/TX packet shall indicate the TX DMG antenna(s) which is being used by the initiator to transmit the EDMG BRP-RX/TX packet. The BRP CDOWN field of each EDMG BRP-RX/TX packet shall indicate the number of remaining EDMG BRP RX/TX packets to be transmitted by the initiator in the initiator SMBT subphase. 
The responder shall initiate the SU-MIMO BF feedback subphase an MBIFS following the reception of an EDMG BRP-RX/TX packet with the BRP CDOWN field set to 0 from the initiator. The responder shall send a MIMO BF Feedback frame to the initiator with the SU/MU field set to 1 and the Link Type field set to 1. In case of channel aggregation, the Aggregation Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame should be set to 1. The TA field of the MIMO BF Feedback shall be set to the MAC address of the responder and the RA field shall be set to the MAC address of the initiator. The MIMO BF Feedback frame shall carry the dialog token in the Dialog Token field that identifies the SU-MIMO BF training. The Number of TX Sector Combinations Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame shall indicate the number of best transmit sector combinations, , recommended by the responder for initiator link. The EDMG Channel Measurement Feedback element in the MIMO BF Feedback frame shall indicate  best transmit sector combinations in the EDMG Sector ID Order field and the BRP CDOWN field, which are determined based on channel measurement data captured from the initiator SMBT subphase. The Channel Measurement Feedback element in the MIMO BF Feedback frame shall contain SNRs corresponding to the  transmit sector combinations in the SNR field. If the Channel Measurement Requested subfield of the MIMO FBCK-REQ field in the MIMO BF Setup frame received from the initiator in the preceding SU-MIMO BF setup subphase is 1, the Channel Measurement Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame shall be set to 1 and the Channel Measurement Feedback element in the MIMO BF Feedback frame shall contain channel measurements corresponding to the  transmit sector combinations in the Channel Measurement field. If the Tap Delay Requested subfield of the MIMO FBCK-REQ field in the MIMO BF Setup frame received from the initiator in the preceding SU-MIMO BF setup subphase is 1, the Tap Delay Present subfield of the MIMO FBCK-TYPE field in the MIMO BF Feedback frame shall be set to 1 and the EDMG Channel Measurement Feedback element in the MIMO BF Feedback frame shall contain tap delays corresponding to the  transmit sector combinations in the Tap Delay field.
The  best transmit sector combinations (or equivalently  best TX-RX AWV configurations) for the initiator link shall be determined in such a way that no transmit or receive AWV come from the same DMG antenna. The determined  best transmit and receive sector combinations for the initiator link shall be treated as the  best receive and transmit sector combinations for the responder link, respectively, where  = . The algorithm for determining the  best transmit sector combinations for the initiator link is implementation dependent. 
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SP: Do you agree to accept the proposed text modification on 11ay D1.0 as in IEEE 802.11-17/1233r1?