1. Interference Signalling Enhancements
Month Year
doc.: IEEE yy/xxxxr0
Mar 2010
Interference Signalling Enhancements
Authors:
Date:
Allan Thomson, Cisco Systems
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
Mar 2010
Abstract
As part of the implementation evaluation of the current collocated interference feature in TGv SB, several significant issues were raised about the viability of the feature
This proposal highlights a solution to resolve TGv SB Recirc #1 CIDs 2 and 13
Allan Thomson, Cisco Systems
John Doe, Some Company

3. An Example Use Case: WiFi Voice Client with BT Headset
Month Year
doc.: IEEE yy/xxxxr0
Mar 2010
An Example Use Case: WiFi Voice Client with BT Headset
The client wants to use voice over wifi and BT headset at the same time. BT is periodic at 3.75ms intervals with 1.25ms active and 2.5ms silence, AP has to transmit after the U-APSD trigger frame and before the BT transmission by the handset
Client U-APSD
Trigger Frame
Client
3.75ms
AP U-APSD
Voice Frames AP
Allan Thomson, Cisco Systems
John Doe, Some Company

4. Month Year
doc.: IEEE yy/xxxxr0
Mar 2010
Problem
The currently defined collocated interference feature has the following issues:
1) Requires the AP implement some form of scheduling and when combined with all interactions and services the AP has to provide for BSS operation becomes a significantly complex task
2) Does not make use of existing frames and AP interactions and therefore requires additional complexity on both AP and client
3) Does not take into account important state such as power save provided by U-APSD
Allan Thomson, Cisco Systems
John Doe, Some Company

5. AP Guiding Principles/Objectives
Maximize over-the-air throughput in the BSS
Minimize wasted transmissions to absent clients
Provide scalable solution for up to 100’s of clients in the BSS
Provide solution such that existing performance is not negatively impacted
Transmit packets in order received subject to priority
Don’t give devices reporting collocated interference greater priority than devices without interference
Minimize development

6. Solution Introduction
Month Year
doc.: IEEE yy/xxxxr0
Mar 2010
Solution Introduction
Extend the U-APSD signalling that takes place to allow the client to report interference free intervals and have the AP integrate that logic into the delivery of frames
Provide two mechanisms
1) Immediate AP transmission based on trigger frames
2) Absolute AP transmission based on TSF offset to 0
Solution aspects:
Advertisement
Client Reporting Mechanism
AP Mediation Mechanism
Allan Thomson, Cisco Systems
John Doe, Some Company

7. Month Year
doc.: IEEE yy/xxxxr0
Mar 2010
Example #1: WiFi Voice Client with Periodic BT Interference every 3.75ms with 1.25ms active BT
Client setup (not shown): Sends ADDTS coexistence for 2ms duration
Client sends U-APSD trigger frame after each BT interference period
AP transmits buffered frames to client after receiving trigger frame until end of duration
Client U-APSD
Trigger Frame
Client
BT Frames
1.25
1.25
3.75ms
AP U-APSD
Voice Frames
Optional AP
EOS U-APSD
Frame AP
Allan Thomson, Cisco Systems
John Doe, Some Company

8. Month Year
doc.: IEEE yy/xxxxr0
Mar 2010
Example #2: WiFi Voice Client with Periodic BT Interference every 3.75ms with 1.25ms active BT
Client setup (not shown): Sends ADDTS coexistence for 3.75ms interval with TSF 0 Offset = 2
Client sends U-APSD trigger frame after each BT interference period
AP transmits buffered frames to client after receiving trigger frame until end of adjusted duration calculated based on interval of interference and offset from TSF
John Doe, Some Company

9. Mar 2010
Advertisement
Add new bit to Extended Capabilities IE to indicate U-APSD Coexistence service
Both AP and non-AP STA would set the bit when supporting the feature
If either does not support the feature then coexistence while using U-APSD is not available
Allan Thomson, Cisco Systems

10. Client Reporting Mechanism
Mar 2010
Client Reporting Mechanism
Order IE 1
Category 2
Action 3
Dialog Token 4
TSPEC 5
TCLAS 6
TCLAS Processing 7
Coexistence (optional)
Include in ADDTS Request frame an optional “coexistence” IE
The client receives a ADDTS response that acknowledges positive acceptance by the AP that coexistence will be provided for the Duration requested
Allan Thomson, Cisco Systems

11. Mar 2010
Coexistence IE
TSF 0 Offset only used if non-AP STA wants AP to adjust for TSF drift of interference
Interval/Duration defines how long the AP is able to transmit to the non-AP STA after receiving a U-APSD trigger frame
TSF 0 Offset field is microseconds since TSF time 0
0 indicates unused
Interval/Duration field is measured in microseconds and defined in 4 octets
0 is a reserved value
Element ID
Length
TSF 0 Offset
Interval/Duratio n
Optional Subelements
Octets: 1 8 4
variable
Allan Thomson, Cisco Systems

12. Client Advertisement Behavior
Mar 2010
Client Advertisement Behavior
If the non-AP STA has advertised support for U-APSD Coexistence feature in the Extended Capabilities IE then it has the capability to detect interference and request use of the coexistence feature
The non-AP STA shall not include the Coexistence IE in the ADDTS frame unless the AP has also advertised support for the Coexistence feature in the Extended Capabilities IE
Allan Thomson, Cisco Systems

13. Client Behavior – Interference Detected
Mar 2010
Client Behavior – Interference Detected
Upon determination that interference is occurring the non-AP STA shall include the Coexistence IE in the ADDTS frame indicating the preferred Duration when the AP should transmit frames to the non-AP during the U-APSD service period
ADDTS frame with Coexistence requested:
Order IE
Value 1
Category
QoS (1) 2
Action
ADDTS request (0) 3
Dialog Token N 4
TSPEC
QoS Flow #1 Parameters 5
TCLAS
QoS Flow #1 Traffic 6
TCLAS Processing
QoS Flow #1 Processing 7
Coexistence
Duration = 2ms
Allan Thomson, Cisco Systems

14. Client Behavior – Interference Changes
Mar 2010
Client Behavior – Interference Changes
Upon determination that interference is changing, the non-AP STA may issue another ADDTS frame to update the Duration field as necessary
ADDTS frame with Coexistence modified:
Order IE
Value 1
Category
QoS (1) 2
Action
ADDTS request (0) 3
Dialog Token N 4
TSPEC
QoS Flow #1 Parameters 5
TCLAS
QoS Flow #1 Traffic 6
TCLAS Processing
QoS Flow #1 Processing 7
Coexistence
Duration = 4ms
Allan Thomson, Cisco Systems

15. Client Behavior – No Interference Detected
Mar 2010
Client Behavior – No Interference Detected
Upon determination that interference has stopped and the non-AP STA no longer needs the AP to provide coexistence protection but continues to use QoS Services for U-APSD SP the non-AP STA may transmit a ADDTS frame without the Coexistence IE
ADDTS frame sent to stop interference protection without CoexistenceIE
Order IE
Value 1
Category
QoS (1) 2
Action
ADDTS request (0) 3
Dialog Token N 4
TSPEC
QoS Flow #1 Parameters 5
TCLAS
QoS Flow #1 Traffic 6
TCLAS Processing
QoS Flow #1 Processing 7
Coexistence
Duration = 2ms
Allan Thomson, Cisco Systems

16. Client Behavior – No QoS Required & No Interference Detected
Mar 2010
Client Behavior – No QoS Required & No Interference Detected
Upon determination that interference has stopped and the non-AP STA no longer needs the AP to provide QoS services or coexistence protection for U-APSD SP the non-AP STA may transmit a DELTS frame without the Coexistence IE
DELTS frame sent to stop interference protection without CoexistenceIE
Order IE
Value 1
Category
QoS (1) 2
Action
ADDTS request (0) 3
Dialog Token N 4
TSPEC
QoS Flow #1 Parameters 5
TCLAS
QoS Flow #1 Traffic 6
TCLAS Processing
QoS Flow #1 Processing 7
Coexistence
Duration = 2ms
Allan Thomson, Cisco Systems

17. Mar 2010
AP Behavior
If the AP has advertised support for U-APSD Coexistence feature in the Extended Capabilities IE then it shall process U-APSD Coexistence IE otherwise it shall ignore
AP should never receive a Coexistence IE from a non-AP STA is the AP has not already advertised support for this feature
An AP that supports U-APSD Coexistence and accepts an ADDTS request shall limit the U-APSD Service Period to the duration specified in the ADDTS Coexistence element.
Allan Thomson, Cisco Systems

18. Mar 2010
U-APSD SP Termination
Normal behavior for AP is that it sets the EOSP bit in the last frame transmitted in the U-APSD service period
If the AP determines that the frame to be transmitted cannot be transmitted before the Duration field expires then it needs to notify the non-AP STA somehow
Explicit Termination:
New normative behavior required to define that the AP transmits a QoS null frame in this circumstance with the EOSP bit set to terminate the U-APSD SP
Implicit Termination:
New normative behavior required to defined that both the AP and non-AP STA will implicitly terminate the SP after the Duration time has expired after reception of the U-APSD Trigger frame at the AP
Allan Thomson, Cisco Systems

19. Mar 2010
Questions ?
Allan Thomson, Cisco Systems