doc.: ieee 802.11-01/412r0 submission s. choi, philips research july 2001 slide 1 aligning 802.11e...
TRANSCRIPT
July 2001
Slide 1
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
Aligning 802.11e HCF Aligning 802.11e HCF and 802.11h TPC Operations and 802.11h TPC Operations
Amjad Soomro, Sunghyun Choi, and Javier del Prado
Philips Research-USABriarcliff Manor, New York
July 2001
Slide 2
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
OutlineOutline
• Introduction• Transmit Power Control under HCF• Proposed rules to improve TPC under
HCF
July 2001
Slide 3
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
ReferencesReferences
• IEEE 802.11e QoS draft D1.0• IEEE 802.11-01/169r2: “DFS and TPC Joint
Proposal for 802.11h” by S. Choi, et al
• IEEE 802.11-01/373r0:“NAV Operation Rules under HCF” by J. del Prado, S. Choi, and A. Soomro
July 2001
Slide 4
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
Transmit Power Control (TPC)Transmit Power Control (TPC)
• Mechanism to reduce energy consumption and co-channel interference
• Adapt the radio transmit power to the minimum level required to ensure correct reception of a frame
July 2001
Slide 5
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
BaselineBaseline
• TGh is working on Transmit Power Control (TPC)
• 01/169r2 (baseline of .11h) is assuming per-STA power control during CFP and CFB under the HCF operation
• But...
July 2001
Slide 6
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
TPC under HCFTPC under HCF
• TPC may not be very efficient under the current rules of HCF:– HC needs to “hear” (i.e., CCA busy) all the frames
within its QBSS. Otherwise, it will reclaim the channel after sensing the medium idle for DIFS
– HC needs to “receive” certain frames for the correct operation of the QBSS (e.g., to update TC queue sizes)
Inefficiency: in ESTA-to-ESTA communications, the transmit power may not be as low as it could be
July 2001
Slide 7
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
ExampleExample• Under current rules of HCF, TxOP holder, i.e., ESTA 1,
will need to transmit frames so that they can be received by ESTA 2 and at least heard (and preferably received) by the HC.
Transmission range of ESTA1
ESTA-to-ESTA communication: ideal case
But the HC need to hear the frames
HCESTA2
ESTA1
CCA busy range of ESTA1
HC
ESTA2
ESTA1
July 2001
Slide 8
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
Proposed HCF Rules for TPCProposed HCF Rules for TPC
July 2001
Slide 9
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
GoalGoal
• Reduce the energy consumption: – Increase TPC efficiency for direct ESTA-to-
ESTA transmissions under HCF
July 2001
Slide 10
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
For the First Frame in a Granted TxOP ...
CCA busy range of ESTA1
• The TxOP holder shall transmit the first frame in a granted TxOP at a high enough power so that the HC can hear it and the destination ESTA can receive it
• Use the best power/data rate combination with the above constraint
• The HC needs to hear the first frame to determine whether the polled ESTA received the QoS CF-poll frame correctly or not
Transmission range of ESTA1
HC
ESTA2
ESTA1
July 2001
Slide 11
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
For the Subsequent Frames ….
Transmission range of ESTA1
• The TxOP holder may transmit at the best power/data rate combination so that the destination ESTA can receive the frame correctly
• To update the TC queue size, or update or request a new TxOP, the TxOP holder should transmit at a power/data rate combination so that both the destination ESTA and the HC can receive the frame correctly
HC
ESTA2
ESTA1
July 2001
Slide 12
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
For Last Frames in a Granted TxOP...
Transmission range of ESTA1
• An ESTA should transmit at least the following types of frames at a power/data rate combination to be received by both the HC and the destination ESTA:– QoS data frame with NF=0 – QoS CF-ACK responding to
the QoS frame with NF=0.
• Desirable to save bandwidth, especially when the TxOP holder finishes earlier than the originally granted TxOP
HC
ESTA2
ESTA1
July 2001
Slide 13
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
HC Reclaim Operation Rules
• The HC can reclaim the channel only in the following situations:– When the CCA stays idle for PIFS time immediately after
the end of the QoS CF- Poll frame – Upon reception of a frame from the TxOP holder with
NF=0 and a relevant QoS CF-ACK frame if the normal ACK policy is used
– The granted TxOP expires
• Note that the HC cannot reclaim the channel after sensing the medium idle for DIFS unconditionally– The first difference from 802.11e D1.0
July 2001
Slide 14
doc.: IEEE 802.11-01/412r0
Submission
S. Choi, Philips Research
• During a TxOP, only the TxOP holder is responsible for recovery from the absence of an expected reception.– The second difference from 802.11e D1.0
• The recovery can be done by:– Retransmiting the frame – Sending a frame to another ESTA– Sending a QoS Null Data to the HC with the NF bit equal to 0
(In this manner, the TxOP ends and the HC can reclaim the channel)
• All other ESTAs, including the HC, shall not initiate channel recovery since they cannot determine if the TXOP holder is transmitting/receiving a frame or not
Recovery Rules