July 2010doc.: IEEE 802.11-10/914r0
IEEE P802.11
Wireless LANs
Date: 2010-07-15
Author(s):
Name / Company / Address / Phone / email
Solomon Trainin / Intel /
Assaf Kasher / Intel /
Carlos Cordeiro / Intel /
Sai (Saishankar) Nandagopalan / Broadcom /
James Yee / Mediatek /
Editor’s instructions: modify the text as follows:
Apair of mSTAs that have established a beamformed link may maintain this link. This subclause describes procedures that allow a pair of mSTAs to maintain a beamformed link that was established between them.
The beamformed link is a result of the most recent success of the procedures (9.25.4.3, 9.25.5.3).
The mSTAs shall negotiate the dot11BeamLinkMaintenanceTime following the rules defined in 7.3a.6.
If the dot11BeamLinkMaintenanceTime has been defined the mSTAs shall implement Beam Link Maintenance Timer to control the beamformed link. The mSTA shall keep the Beam Link Maintenance Timer per each beamformed link. The timer range and resolution shall be of the dot11BeamLinkMaintenanceTime range and resolution. After it is set the Beam Link Maintenance Timer shall count down. The timer shall be stopped when it reaches value zero. The Beam Link Maintenance Timer shall be halted during BT and ABFT. If the beamformed link uses SP allocation only, the Beam Link Maintenance Timer shall be halted during SPs of other links and during CBP(s).
The Beam Link Maintenance Timer shall be set to the dot11BeamLinkMaintenanceTime (7.3a.6) when the source mSTA and destination mSTA successfully completes the beamforming.
The AP/PCP mSTA shall set the Beam Link Maintenance Timer to the dot11BeamLinkMaintenanceTime (7.3a.6) when it receives response from the non-AP/PCP mSTA during AT and it receives the SPR frames as response to the Poll frame, and it receives the response frames using antenna directed towards the mSTA.
The non-AP/PCP mSTA shall set the Beam Link Maintenance Timer to the dot11BeamLinkMaintenanceTime (7.3a.6) when it receives request from the AP/PCP mSTA during AT, and it receives the Poll and the Grant frames and it receives the frames using the beamformed link with the AP/PCP mSTA.
The mSTA shall set the Beam Link Maintenance Timer to the dot11BeamLinkMaintenanceTime (7.3a.6) when the immediate response or acknowledgement (ACK, BA, mmWaveCTS, mmWaveDTS) has been received from the mSTA of the beamformed link.
The mSTA shall set the Beam Link Maintenance Timer to the dot11BeamLinkMaintenanceTime (7.3a.6) when the transmission of the immediate response or acknowledgement (ACK, BA, mmWaveCTS, mmWaveDTS) has been completed to the mSTA of the beamformed link.
To prevent expiration of the Beam Link Maintenance Timer when the mSTA does not have MSDU to send it may transmit the null data frames to maintain the beamformed link.
The destination STA of an SP waits for aSlotTime + aPHY-RX-START-Delay from the start of the SP for a PHY-RXSTART.indication to occur. If a PHY-RXSTART.indication does not occur during this time, the The destination STA of the SP should shall configure its receive antenna to a quasi-omni antenna patternfollowing the expiration of the dot11BeamLinkMaintenanceTime for reminder of the SP and during any SP following the expiration. this time.
If a PHY-RXSTART.indication does occur during this time, the STA should wait for the corresponding PHY-RXEND.indication to determine whether the MPDU transmission was successful. The recognition of anything else other than a valid frame sent by the source STA of the SP and addressed to the destination STA of the SP should be interpreted as beamformed link breakage by the destination STA. Following the determination of the beamformed link, the destination STA of the SP should configure its receive antenna to a quasi-omni antenna pattern.
The destination STA of an SP may transmit a mmWaveDTS frame to the source STA of the SP following the rules in 9.23.6.5 mmWave Protected Period, if the NAV timer at the destination STA has a non-zero value and the destination STA wants to prevent the source STA of the SP to re-start beamforming with the destination STA.
Any time after dot11BeamLinkMaintenanceTime aSlotTime + aPHY-RX-START-Delay has elapsedfrom the start of the SP, the source STA of the SP may transmit initiate an RTS ISS frame to restore the beamformed link with the destination STA of the SP following the rules defined in 9.25.1.and, in this case, the RTS shall be transmitted at MCS 0. The source STA of the SP should restart beamforming with the destination STA after no more than dot11ShortRetryLimit RTS retransmission attempts without a response CTS.
The destination STA of an SP waits for aSlotTime + aPHY-RX-START-Delay from the start of the SP for a PHY-RXSTART.indication to occur. If a PHY-RXSTART.indication does not occur during this time, the The responder mSTA of the beamformed link in the CBP should shall configure its receive antenna to a quasi-omni antenna patternfollowing the expiration of the dot11BeamLinkMaintenanceTime during the time it is not involved in any other transaction..
If a PHY-RXSTART.indication does occur during this time, the STA should wait for the corresponding PHY-RXEND.indication to determine whether the MPDU transmission was successful. The recognition of anything else other than a valid frame sent by the source STA of the SP and addressed to the destination STA of the SP should be interpreted as beamformed link breakage by the destination STA. Following the determination of the beamformed link, the destination STA of the SP should configure its receive antenna to a quasi-omni antenna pattern.The destination STA of an SP may transmit a mmWaveDTS frame to the source STA of the SP following the rules in 9.23.6.5 mmWave Protected Period, if the NAV timer at the destination STA has a non-zero value and the destination STA wants to prevent the source STA of the SP to re-start beamforming with the destination STA.
Any time after dot11BeamLinkMaintenanceTime aSlotTime + aPHY-RX-START-Delay has elapsedfrom the start of the SP, the source initiator mSTA of the beamformed link in the CBPof the CBP may transmit initiate the an RTS ISS frame to restore the beamformed link with the responder STA following the rules defined in 9.25.1.and, in this case, the RTS shall be transmitted at MCS 0. The source STA of the SP should restart beamforming with the destination STA after no more than dot11ShortRetryLimit RTS retransmission attempts without a response CTS.
To maintain a beamformed link between a PCP/AP and a non-PCP/non-AP STA, the PCP/AP should send a frame with its antenna pattern directed to the STA at least once every aMinBTPeriod beacon intervals and the STA should send a frame with its antenna pattern directed to the PCP/AP at least once every aMinBTPeriod beacon intervals. If the PCP/AP does not receive a frame with a MCS other than MCS 0 from the STA after dot11ShortRetryLimit transmission attempts, it assumes that the beamformed link with the STA is invalid and should schedule time in the beacon interval for the PCP/AP to initiate beamforming training with the STA whose beamformed link became invalid
If a mSTA detects degradation in the link quality between itself and another mSTA, the mSTA can use beam tracking or beam refinement to improve the link quality. The mSTA can request the PCP/AP mSTA to schedule an SP to perform BF with the other mSTA or use a CBP to perform BF. The mSTA can use the A-BFT to perform BF if the other mSTA is its PCP/AP. A PCP/AP mSTA can perform BF with a non-PCP/non-AP STA during a CBP or by scheduling an SP between the PCP/AP mSTA and the non-PCP/non-AP mSTA through an Extended Schedule element transmitted in a mmWave Beacon or Announce frames.
If the link quality between a PCP/AP mSTA and a non AP/PCP mSTA degrades, but the mSTA can still receive mmWave Beacon frames and the A-BFT present field set to 1, the mSTA should improve the link quality by performing beamforming during the A-BFT period as described in 9.25.4.
Editor’s instructions: append new subclause after 7.3a.5 Beamforming Control field
7.3a.6 Beamformed Link Maintenance field
BeamLink Master/Slave / BeamLink Maintenance Unit Index / BeamLink Maintenance valueBits: / 1 / 1 / 6
Figure 68 – Beamformed Link Maintenance field
Table 18 – Encoding of BeamLink Maintenance Index
BeamLink Maintenance Unit Index / BeamLink Maintenance Unit(us)
0 / 32
1 / 2000
The Beamformed Link Maintenance field provides the mSTA with dot11BeamLinkMaintenanceTime. The time is calculated as:
dot11BeamLinkMaintenanceTime =
BeamLink_Maintenance_Unit * BeamLink_Maintenance_Value
The BeamLink Master/Slave field is set to 1 to indicate that the mSTA is the Master of the data transfer and set to 0 if the mSTA is a slave of the data transfer. The mSTAs use the BeamLink Master/Slave field to negotiate the dot11BeamLinkMaintenanceTime as presented in the table 19.
Table 19 – The Beamformed Link Maintenance negotiation
mSTA-A / mSTA-BBeamLink Master/Slave / BeamLink Master/Slave / dot11BeamLinkMaintenanceTime (mSTA-A) vs.
dot11BeamLinkMaintenanceTime (mSTA-B) / Result
0 / 0 / = / dot11BeamLinkMaintenanceTime (mSTA-A)
1 / 0 / Don’t care / dot11BeamLinkMaintenanceTime (mSTA-A)
1 / 1 / = / dot11BeamLinkMaintenanceTime (mSTA-A)
1 / 1 / Undefined
The BeamLink Maintenance Unit Index is used as defined in the Table 18.
The BeamLink Maintenance value if >0 is used to calculate the dot11BeamLinkMaintenanceTime, otherwise the dot11BeamLinkMaintenanceTime is left undefined.
Editor’s instructions: modify the text of “7.2.1.17 Sector sweep feedback”and “7.2.1.18 Sector sweep ACK (SS-ACK)” by adding new field ”the Beamformed Link Maintenance field” one octet long.
Editor’s instructions: append new information element to the Table 7-26 – Element IDs as follows:
Information element / Element ID / Length (in octets) / ExtensibleBeamLink Maintenance element / <ANA> / 1 / subelements
Editor’s instructions: add new subclause after 7.3.2.109 Cluster Report element
7.3.2.110 BeamLink Maintenance element
The format of the BeamLink Maintenance element is shown in Figure 61. The BeamLink Maintenance element is included in management action frames, such as the Probe, Announce and the Information Request and Response frames, transmitted between non-AP/PCP mSTA and AP/PCP mSTA. The element is included in the Probe and Information Request and Response frames transmitted between non-AP/PCP mSTAs.
Element ID / Length / Beamformed Link Maintenance fieldOctets / 1 / 1 / 1
Figure 61 – BeamLink Maintenance element
The Beamformed Link Maintenance field is defined in 7.3a.6
Submissionpage 1Solomon Trainin et al