Discussion on MAC Calibration Power Saving Test July 2014 doc.: IEEE 802.11-12/xxxxr0 January 2015 Discussion on MAC Calibration Power Saving Test Date: 2015-01-12 Authors: Yanchun Li (Huawei Technologies) Osama Aboul-Magd (Huawei Technologies)

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)

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)

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 802.11 spec. ProbeDelay =100us (between the range [0, Max PPDU+SIFS+ACK] suggested by [2]) Yanchun Li (Huawei Technologies)

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)

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)

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)

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)

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=0.54375%) 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)

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) = 39110.5us 39110.5us /40ms=97.77625% Yanchun Li (Huawei Technologies)

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)

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 0.54375% 0.8400% 97.77625% 98.2000% 0.9600% 0% Simulation 0.54% 0.84% 97.78% 98.20% 0.96% U-APSD off 98.3200% 98.2200% 98.32% Yanchun Li (Huawei Technologies)

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)

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)

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) 0.00029906 0.000924 0.0025872 3.217E-06 0.05401 0.002957 power percentage 7.84% 24.23% 67.84% 0.08% 93.2963% 1.5961% 5.1075% sum power (Watt) 0.00381349 0.057891 U-APSD off Simulation 98.32% 0.84% 0.00% 98.20% 0.96% 0% 0.054076 93.90281% 1.60452% 4.49267% sum power 0.0575872 Energy Efficiency Ratio =0.0662 Yanchun Li (Huawei Technologies)

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)

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 0.0662. Some text changes in simulation scenario are needed to let everyone get power saving test results aligned. Yanchun Li (Huawei Technologies)

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)

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)

Reference [1] 11-14-0980-05-00ax-simulation-scenarios.docx (2014 Nov) January 2015 Reference [1] 11-14-0980-05-00ax-simulation-scenarios.docx (2014 Nov) [2] 11-12-0840-01-00ah-ap-assisted-medium-synchronization.pptx [3] 11-14-1495-00-00ax-power-save-calibration-results.pptx Yanchun Li (Huawei Technologies)

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)

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)