1. Clarification on Some HCF Frame Exchange Rules
Month 1998
doc.: IEEE /xxx
October 2001
Clarification on Some HCF Frame Exchange Rules
Sunghyun Choi and Javier del Prado
Philips Research USA
Srinivas Kandala and Ken Nakashima
Sharp Labs
S. Choi, Philips & S. Kandala, Sharp

2. Outline Response depending on frame subtypes Error handling
Month 1998
doc.: IEEE /xxx
October 2001
Outline
Response depending on frame subtypes
ACK or not
ACK vs. QoS CF-ACK
Error handling
SIFS or PIFS
RTS/CTS during CFP and CFB
S. Choi, Philips & S. Kandala, Sharp

3. October 2001
ACK or Not?
Whether different subtypes of Data frames require an acknowledgement is not explicitly specified.
It was more true with , but we have “No Ack” bit in QoS control field with e.
Resolution: Clarify that
A data type frame of any subtype with “No Ack” bit set to zero will require an acknowledgement.
A detailed usage of QoS control field should be reflected in Figure 14.5.
S. Choi, Philips & S. Kandala, Sharp

4. October 2001
QoS CF-ACK or ACK?
Which of QoS CF-ACK or ACK should be used to acknowledge a QoS data reception is not clear.
QoS CF-ACK is a data type with 30 bytes typically, and ACK is a control type with 14 bytes.
QoS CF-ACK can update the queue status with HC. (assuming that “QoS null frames” in Figure 14.5 of IEEE e/D1.2 include “QoS CF-ACK”.)
Per , ACK is used under DCF and CF-ACK is supposed to be used for CF-pollable STAs under PCF.
S. Choi, Philips & S. Kandala, Sharp

5. QoS CF-ACK or ACK? (Cont.)
October 2001
QoS CF-ACK or ACK? (Cont.)
In terms of the function, ACK is equivalent to QoS CF-ACK w/ NF=1 & No Ack = 1.
Resolution:
Clarify that ACK and QoS CF-ACK w/ NF=1 & No Ack = 1 are equivalent, and either of them can be used for relevant situations.
Clarify that ACK cannot be used instead of QoS CF-ACK w/ either or both of NF & No Ack bits set to zero.
S. Choi, Philips & S. Kandala, Sharp

6. PIFS or SIFS after Error?
October 2001
PIFS or SIFS after Error?
When an ESTA (including HC) in charge of channel recovery does not start receiving an expected frame within PIFS, it will recover by transmitting a frame after PIFS.
What happens when an erroneous frame is received by such an ESTA is not clear.
Resolution: add the following in
If an erroneous frame is received at the ESTA, which expects a response to its transmission, the ESTA may initiate the recovery by transmitting a frame after SIFS from the end of the last reception.
S. Choi, Philips & S. Kandala, Sharp

7. RTS/CTS during CFP/CFB
October 2001
RTS/CTS during CFP/CFB
Per e/D1.2, RTS/CTS exchange is allowed during CFP and CFB
However, what happens if the RTS/CTS exchange is not successful should be clearly stated.
Apparently, we don’t want the TXOP holder or the HC to go to the back-off in this case.
S. Choi, Philips & S. Kandala, Sharp

8. RTS/CTS during CFP/CFB (Cont.)
October 2001
RTS/CTS during CFP/CFB (Cont.)
Resolution: add the following in
The RTS sender can recover from the failure of the successful CTS reception by transmitting a frame (1) within PIFS from the end of the RTS transmission if the PHY-CCA-indicate(busy) does not occur, and (2) within SIFS from the end of the last frame reception if the frame after the RTS transmission is received in error.
S. Choi, Philips & S. Kandala, Sharp