1. Fair Quiet for DFS Date: 2011-10-18 Authors: February 2008
doc.: IEEE /2376r0
Date: October, 2011
Fair Quiet for DFS
Date:
Authors:
Liwen Chu Etc.
Liwen Chu, STMicroelectronics

2. Why Is Partial VHT Quiet Operating Channel Required
Date: October, 2011
Why Is Partial VHT Quiet Operating Channel Required
5GHz band include DFS channels and non-DFS channels.
There is no quiet requirement on non-NFS channels by regulations.
In VHT BSS with DFS + non-DFS operating channels, VHT AP/STAs should be able to transmit frames on primary channel during secondary channel DFS detection.
5.15~5.35 GHz
5.47~5.725 GHz
5.725~5.825 GHz 36 40 44 48 52 56 60 64
100
104
108
112
116
120
124
128
132
136
140
144
149
153
157
161
165
5.25 ~ 5.35
5.47 ~ 5.725
DFS band
DFS band
Primary 80MHz, non-DFS band
Secondary 80MHz, DFS band 2

3. BSS Usable Channel Width
Date: October, 2011
The current Solution
A new Quiet Channel element is defined in .11ac. It is always combined with Quiet element to indicate whether a subset of an operating channel needs to be quieted.
BSS Usable Channel Width indicates the channel width that may be used during quiet duration.
AP Quiet Mode indicates if the AP is able to transmit on one frequency segment and perform radar detection on the other frequency segment at the same time, e.g.
1---- being able to transmit on one frequency segment and perform radar detection on the other frequency segment at the same time.
0---- not being able to transmit on one frequency segment and perform radar detection on the other frequency segment at the same time.
Element ID
Length
BSS Usable Channel Width
AP Quiet Mode
Octets:
Quiet Channel element
Element ID
Length
Quiet Count
Quiet Period
Quiet Duration
Quiet Offset
Octets:
Quiet element 3

4. Issues with the current Solution
Date: October, 2011
Issues with the current Solution
When Quiet element and Quiet Channel element are received by .11a/n STAs, these STAs will be quiet during Quiet Duration, and the Quiet Channel element will be ignored. When Quiet element and Quiet Channel element are received by VHT STAs, they will exchange frames on usable channels indicated by Quiet channel element during quiet duration.
So if the AP indicates that the primary 80MHz channel is usable through Quiet Channel element and Quiet element, VHT STAs and the VHT AP can use the primary 80 MHz channel to transmit frames. But the legacy STAs will be quiet since they think the whole operating channel is used to detect radar during quiet duration. This is a fairness issue with legacy.
There is no mechanism for a non-AP STA to tell its peer STA/AP its Quiet mode. Exchanging frames with a STA that is not able to transmit on one frequency segment and perform radar detection on the other frequency segment at the same time may interfere the radar detection.
It would be better if the VHT non-AP STA could communicate whether it can sense and exchange frames at the same time. 4

5. Element Updating: Extended Quiet Element (p. 1 of 2)
Date: October, 2011
Element Updating: Extended Quiet Element (p. 1 of 2)
Define a new Extended Quiet element with extends the Quiet Channel element to include the data fields of the Quiet element. In this way, legacy devices will ignore this element (and not mistakenly go quiet) and VHT STAs will know the BSS-usable channel width during the Quiet Duration.
Quiet Count, Quiet Period, Quiet Duration, Quiet Offset are used to describe the exact time of quiet duration.
BSS Usable Channel Width is used to describe which channel can be used to transmit frames during the quiet duration, if any.
AP Quiet Mode indicate if an AP can transmit on one frequency segment and perform radar detection on the other frequency segment at the same time.
Element ID
Length
Quiet Count
Quiet Period
Quiet Duration
Quiet Offset
BSS Usable Channel Width
AP Quiet Mode
Octets:
Extended Quiet element 5

6. Date: October, 2011
Element Updating : STA Quiet Mode in STA’s VHT or Extended Capability Element (p. 2 of 2)
Add a STA Quiet Mode (1 bit) to indicate whether the STA is able to transmit on one frequency segment and perform radar detection on another frequency segment at the same time.
When both the AP and non-AP peer STA, or two non-AP peer STAs, support transmission on one frequency segment and can perform radar detection on the other frequency segment at the same time, they can use BSS usable channel bandwidth to transmit frames during a quiet duration.
STA Quiet Mode can be added to either the VHT Capability element or the Extended Capability element. 6