1. Discussion on MAC Calibration Power Saving Test
July 2014
doc.: IEEE /xxxxr0
January 2015
Discussion on MAC Calibration Power Saving Test
Date:
Authors:
Yanchun Li (Huawei Technologies)
Osama Aboul-Magd (Huawei Technologies)

2. January 2015
Recap: Test 5 U-APSD
U-APSD which is suitable for bi-directional transmission has been selected by test 5 (Power Saving MAC Calibration) [1]
Yanchun Li (Huawei Technologies)

3. Issues of test 5 U-APSD in current SSD
January 2015
Issues of test 5 U-APSD in current SSD
There are several missing parts in current simulation scenario document[1]
ProbeDelay for STA awake from doze
Encapsulation of application payload
Event sequence
Yanchun Li (Huawei Technologies)

4. The parameter has not yet been clarified in [1] 1) ProbeDelay
January 2015
The parameter has not yet been clarified in [1] 1) ProbeDelay
“A STA that is changing from Doze to Awake in order to transmit shall perform CCA until a frame sequence is detected by which it can correctly set its NAV, or until a period of time equal to the ProbeDelay has transpired.” from spec.
ProbeDelay =100us (between the range [0, Max PPDU+SIFS+ACK] suggested by [2])
Yanchun Li (Huawei Technologies)

5. January 2015
The parameter has not yet been clarified in [1] 2) UDP protocol for VoIP: Packet head overhead
For 120kbps codec VoIP service,
40ms inter-arrival time, 120byte/packet payload.
If using TCP, there will be TCP ACK for each packet.
Fig. 13 in [1] shows there is no TCP ACK.
Yanchun Li (Huawei Technologies)

6. The parameter has not yet been clarified in [1] 3) Event sequence
January 2015
The parameter has not yet been clarified in [1] 3) Event sequence
AP sends Beacon periodically
The Beacon may interrupt STA’s transmission and may affect STA’s listen time
An extra round of AIFS+random backoff will be performed if a Beacon is detected before ProbeDelay timeout
Yanchun Li (Huawei Technologies)

7. The parameter has not yet been clarified in [1] - The event sequence
January 2015
The parameter has not yet been clarified in [1] - The event sequence
Needs further specify
‘the first UL DATA arrives at 0.011’
‘the first DL DATA arrives at 0.01’
‘first Beacon is sent at 0.02’
Yanchun Li (Huawei Technologies)

8. Theoretical Calculation of time in each state - STA Tx/Rx Time
January 2015
Theoretical Calculation of time in each state - STA Tx/Rx Time
Theoretical Calculation of time in each state - STA Tx/Rx Time
STA
Tx Time = 336us /40ms=0.84%
1 Voice Codec Data Payload (268us) in each 40ms
ACK= 68us
Rx Time = Tx Time=0.84%
Operation
Value
Application Layer Packet
120kbps codec,once per 40ms
120 bytes
Transport Layer Packet
+ UDP Header 8 bytes
128 bytes
IP Layer Packet
+ IP Header 20 bytes
148 bytes
MAC PDU
+ MAC Header 30 bytes
178 bytes
PHY SDU (A-MPDU: 1 MPDU per PHY SDU)
Ceiling((16 bit (Service Field)+ 4*8bit(Delimiter) + 174*8bit (MPDU)+ 2bit (Padding)+6bit (CC))/6.5e6,4e-6)
228 us
PHY PDU
+ 11ac PHY Header 40 us
268 us
Yanchun Li (Huawei Technologies)

9. Theoretical Calculation of time in each state - STA Tx/Rx Time
January 2015
Theoretical Calculation of time in each state - STA Tx/Rx Time
STA’s listen time per 40ms (217.5us/40ms= %)
100us (ProbeDelay)+( 34us(AIFS)+9us*15/2 (Backoff)+16us(SIFS) ) =217.5us
ProbeDelay
100 us
217.5 us (Listen Time per 40ms)
Channel Deferral
AIFS
34 us
117.5us in Total x1
=117.5 us
Random Backoff
9*15/2 us
SIFS
16 us
Yanchun Li (Huawei Technologies)

10. Theoretical Calculation of time in each state - STA Sleep Time
January 2015
Theoretical Calculation of time in each state - STA Sleep Time
STA Sleep Time
40ms (period)-336us (Tx Time)-336us(Rx Time)-217.5us(Listen Time) = us
us /40ms= %
Yanchun Li (Huawei Technologies)

11. Theoretical Calculation of time in each state - AP
January 2015
Theoretical Calculation of time in each state - AP
AP needs extra time to transmit beacon
[3] suggest 80 octet for Beacon size
Beacon PSDU duration=Ceiling(80*8 bit/6.5e6bps,4e-6s)=100ms
Consider legacy MAC header, overall duration for beacon
100us+20us =120us (per 100ms)
Yanchun Li (Huawei Technologies)

12. Simulation results Simulation results matches the theoretical analysis
January 2015
Simulation results
Simulation results matches the theoretical analysis
MAC throughput: 29.6 kbps in both DL/UL, PER = 0%
STA AP
Searching RX TX
Sleeping
U-APSD on
Theoretical %
0.8400% % %
0.9600% 0%
Simulation
0.54%
0.84%
97.78%
98.20%
0.96%
U-APSD off % %
98.32%
Yanchun Li (Huawei Technologies)

13. Pie chart (breakdown) of time: U-APSD
January 2015
Pie chart (breakdown) of time: U-APSD
Pie chart (breakdown) of time spent in each power state during the course of the simulation
Yanchun Li (Huawei Technologies)

14. Pie chart (breakdown) of time: Active
January 2015
Pie chart (breakdown) of time: Active
Pie chart (breakdown) of time spent in each power state during the course of the simulation
Yanchun Li (Huawei Technologies)

15. Breakdown of Power Consumption
January 2015
Breakdown of Power Consumption
Power consumption
Energy
Listening RX TX
Sleeping
U-APSD on
current (mA) 50
100
280
0.003
power (Watt)
3.217E-06
power percentage
7.84%
24.23%
67.84%
0.08% %
1.5961%
5.1075%
sum power (Watt)
U-APSD off
Simulation
98.32%
0.84%
0.00%
98.20%
0.96% 0% % % %
sum power
Energy Efficiency Ratio
=0.0662
Yanchun Li (Huawei Technologies)

16. Pie chart (breakdown) of energy consumption: U-APSD on vs. off
January 2015
Pie chart (breakdown) of energy consumption: U-APSD on vs. off
Pie chart (breakdown) of energy consumed in each power state during the course of the simulation
Yanchun Li (Huawei Technologies)

17. January 2015
Conclusions
Our MAC calibration test 5 U-APSD’s simulation results match with the theoretical analysis.
The energy efficiency ratio of U-APSD for delivering 120kbps codec in ideal case is
Some text changes in simulation scenario are needed to let everyone get power saving test results aligned.
Yanchun Li (Huawei Technologies)

18. Proposed Text Changes in [1]
January 2015
Proposed Text Changes in [1]
In simulation scenario document[1], in page 45, insert text as:
Power save test parameters
AIFS=DIFS=34us
RTS/CTS [ OFF ]
MCS = [ 0 ]
DTIM = [ 3 ] STA may not receive Beacons for TIM
Max SP Length = [ 4 ]
ProbeDelay = 100us
Yanchun Li (Huawei Technologies)

19. Proposed Text Changes in [1]
January 2015
Proposed Text Changes in [1]
The size of application layer generated content per 40ms is 120 bytes. Assuming the content is delivered by UDP.  MSDU length:  120 bytes with CWmin=15. (assuming 24 kbps codec, once every 40 ms) for both uplink and downlink
MSDU length:  120 bytes with CWmin=15.
Following event sequence is assumed:
The first UL DATA arrives at 0.011;
The first DL DATA arrives at 0.01;
First Beacon is sent at 0.02.
Yanchun Li (Huawei Technologies)

20. Reference [1] 11-14-0980-05-00ax-simulation-scenarios.docx (2014 Nov)
January 2015
Reference
[1] ax-simulation-scenarios.docx (2014 Nov)
[2] ah-ap-assisted-medium-synchronization.pptx
[3] ax-power-save-calibration-results.pptx
Yanchun Li (Huawei Technologies)

21. Proposed text change in [1]
January 2015
Proposed text change in [1]
ProbeDelay
Power Save Mechanism parameters
Mechanism
Parameter
Definition/Values
Pick one value from the Suggested Set of Simulation Values **
Power save mode (PSM)
Beacon Interval (BI)
100 TU
DTIM
Integer in unit of BI
{ 1, 3 }
PSM timeout
Length of time before STA goes to sleep
{ 50, 100, 200 } ms
Power save polling (PSP)
Beacon Interval
Unscheduled automatic power save delivery (U-APSD)
ProbeDelay
100 us
Max SP Length
Indicate the maximum number of buffered MSDUs, A-MSDUs, and MMPDUs that AP may deliver per SP
{ 2, 4, 6, ∞ } AC
Access Category
All ACs are both delivery and trigger enabled
Yanchun Li (Huawei Technologies)

22. Recap: Power save test parameters in [1]
January 2015
Recap: Power save test parameters in [1]
Power save test parameters
AIFS=DIFS=34us
RTS/CTS [ OFF ]
MCS = [ 0 ]
DTIM = [ 3 ] STA may not receive Beacons for TIM
Max SP Length = [ 4 ]
Output:
MAC throughput
Pie chart (breakdown) of time spent in each power state during the course of the simulation
Pie chart (breakdown) of energy consumed in each power state during the course of the simulation
Yanchun Li (Huawei Technologies)