1. Improvement to TWT Parameter set selection
Month Year
doc.: IEEE yy/xxxxr0
September 2017
Improvement to TWT Parameter set selection
Date:
Authors:
Jarkko Kneckt, Apple
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
September 2017
Abstract
This submission allows the TWT requesting STA to signal repeating times when it is not able or has limited capability to receive or transmit. Normative text is provided in submission r0.
The signalling simplifies the TWT parameter set selection; the TWT responding STA has means to select more suitable alternate times for TWT SPs and transmission of multiple TWT setup requests and responses can be avoided.
The signalling improves transmission reliability, reduces transmission overheads and STA power consumption.
Jarkko Kneckt, Apple
John Doe, Some Company

3. Non-AP STA challenges to be available on a TWT SP
September 2017
Non-AP STA challenges to be available on a TWT SP
A STA may not be available, or has limited transmission/reception capability, during a TWT SP
A STA may exchange data in device-to-device network
A STA may have multiple radios and it cannot operate simultaneously with the radios
Jarkko Kneckt, Apple

4. Current TWT setup signaling communicates one TWT parameter set
September 2017
Current TWT setup signaling communicates one TWT parameter set
The TWT requesting STA communicates one set of TWT parameters to TWT responding STA:
The TWT Interval communicates the interval between TWT start times which affects to transmission delays
The TWT Start Time communicates the timing of the TWT SP
The Nominal Minimum Wake Duration provides the time in which the AP should transmit the first PPDU in TWT SP
Jarkko Kneckt, Apple

5. Selecting times for TWT SPs
September 2017
Selecting times for TWT SPs
The TWT requesting non-AP STA may set the TWT SP start time, duration and interval to values when it can be available
The AP may not be able to schedule TWT SPs on these times
AP may be congested on these times and STA performance may be poor
The interval or TWT duration may not be supported by the AP
The AP may need to propose alternative TWT SP start time, duration or interval
Jarkko Kneckt, Apple

6. Current TWT agreement setup, suggested and demanded TWT agreements
September 2017
Current TWT agreement setup, suggested and demanded TWT agreements
The TWT requesting STA may suggest or demand the use of the TWT parameter set:
When TWT agreement is suggested, the setup may be possible, if the provided single set of TWT parameter values cannot be accommodated
The AP has no means to know how to select alternative values that are suitable for the STA
When TWT agreement is demanded, the setup will be rejected, if the single set of TWT parameter values cannot be accommodated
This is ultimate demand, nothing else is acceptable for the requesting STA
Jarkko Kneckt, Apple

7. Challenges of current TWT setup
September 2017
Challenges of current TWT setup
Currently, the TWT requesting STA cannot indicate the times that are not suitable for it
This may lead to multiple transmissions of TWT setup request and TWT setup response frames that takes time and causes overhead
The TWT SP times may be poorly selected, because unsuitable times cannot be signaled
The link performance may be severely degraded, if TWT SPs are scheduled at times when the non-AP STA performance is poor
This may cause frame loss and transmission delays
Jarkko Kneckt, Apple

8. September 2017
Proposal: Signaling a schedule when a STA is not able to transmit or receive
A TWT requesting STA should list the repeating times, i.e. constrained periods, when it is not able transmit or receive
If needed, the TWT receiving STA should use this information to select the TWT SP times, i.e. select the times when the requesting STA is able to transmit and receive
Jarkko Kneckt, Apple

9. Proposal, TWT Flow setup for power save and for constrained periods
September 2017
Proposal, TWT Flow setup for power save and for constrained periods
One TWT Setup frame requests a single TWT agreement
To setup (1) a TWT flow for power save and a (2) TWT Flow to avoid operation at times when STA is not available, the STA should transmit two TWT Setup request frames:
One TWT Setup frame requesting a TWT flow for power save
One TWT Setup frame requesting a TWT flow for constrained periods, to provide information on the times when STA is not available
The two setup frames may be aggregated to the same PPDU and transmitted at the same time
Jarkko Kneckt, Apple

10. September 2017
TWT setup response
The AP may accept or reject the TWT constrained periods agreement, i.e. schedule when the requesting STA is not available:
If accepted, the requesting STA shall update the constrained periods agreement if its availability changes
When constrained periods and TWT agreement for power save are transmitted in the same PPDU, the AP may accept only TWT Agreement for power save:
The STA shall not update its availability information to the AP
The AP may propose alternative parameters for TWT agreement for power save
The TWT parameter set on constrained periods, i.e. when STA is not available helps to select suitable schedule
Jarkko Kneckt, Apple

11. September 2017
Summary
This submission describes a mechanism for a non-AP STA to indicate the times when it not able or has limited availability to transmit or receive
The TWT Responding STA may propose more suitable alternative TWT SP times
More suitable TWT SP times improves transmission reliability
Transmission of multiple TWT setup request and TWT setup response frames can be avoided
TWT setup signaling is faster and contains relevant information
Jarkko Kneckt, Apple

12. September 2017
Straw poll 1
Do you agree that the TWT requesting STA should be able to indicate the times when it is not able to or has limited capability to transmit or receive?
Jarkko Kneckt, Apple