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May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis 802.11 Coex Simulation and Analysis Date: 2019-05-16 Authors: Name Affiliations Address Phone Email Chung-Ta Ku Mediatek Mediatek +1-408526-1899 [email protected] Paul Cheng James Wang Mediatek Gabor Bajko Mediatek Yongho Seok Mediatek 2840 Junction Ave San Jose, CA 95134 James Yee Mediatek Thomas Pare Mediatek Submission

Slide 1 [email protected] [email protected] Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Outline Simulation Setup Simulation Parameters Analysis Airtime Usage (Medium usage time) Simulation Results Analysis & Issues System TP Simulation Results Analysis & Issues Conclusions Submission Slide 2 Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Priority Classes in IEEE and ETSI AP EDCA Parameter AIFSN Td CWmin CWmax TXOP Limit

Voice (VO) 1 25 us 3 7 2.080ms Video (VI) 1 25 us 7 15 4.096ms Best effort (BE) 3 43 us 15 63 2.528ms Background (BK) 7 79 us 15 1023 2.528ms ETSI Priority class P0 Td CWmin

CWmax maxCOT Class 4 1 25 us 3 7 2ms Class 3 1 25 us 7 15 4ms Class 2 3 43 us 15 63 6ms Class 1 7 79 us 15 1023 6ms IEEE (VO) LAA (Class 1)

ETSI (class 4) busy SIFS AIFSN=1 16 9 9 Backoff 9 9 TX 9 Td = 25 us Non-AP STA default EDCA parameter in Table 9-155 of REVmd. ETSI parameters in Table 7 and 8 of EN301893 v2.1.1 Observation (key difference highlighted in dashed circle): IEEE default TXOP Limit and larger CWmax versus equivalent ETSI priority class COT and CWmax can affect medium utilization rate Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Simulation Setup Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis OMNeT++ Baseline Simulation Setup (IEEE vs IEEE) Simulation Time: 10s

Full-buffer traffic loads UDP Packet Size = 1472 Bytes 2 IEEE Links Using 11ac, 20MHz, no SGI, Nss =1 MPDU Size = 1552 Bytes, fixed MCS 8 IEEE AC CCA-CS = -82 dBm CCA-ED = -62 dBm TX Power = 20 dBm (0.5, 9.5) AP (0.5 + X, 9.5) STA Distance Y = 9m AP STA (0.5, 0.5) (0.5 + X, 0.5) Distance X = 10m, 20m, 30m, Submission Chung-Ta Ku, Mediatek May 2019

2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis OMNeT++ Coexist Simulation Setup (ETSI vs IEEE) Simulation Time: 10s Full-buffer traffic loads UDP Packet Size = 1472 Bytes 1 IEEE Link Using 11ac, 20MHz, no SGI, Nss =1 MPDU Size = 1552 Bytes, fixed MCS 8 IEEE AC 1 ETSI(LAA) Link Using LTE, 20MHz , Nss =1 TBSize = 75376 Bytes, fixed MCS 28 LAA priority class CCA-CS = -82 dBm CCA-ED = -62 dBm

TX Power = 20 dBm Submission (0.5, 9.5) eNB (0.5 + X, 9.5) UE Distance Y = 9m AP STA (0.5, 0.5) (0.5 + X, 0.5) Distance X = 10m, 20m, 30m, Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Airtime Usage - Simulation Results Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Distance X = 10m Airtime Usage (sec) (IEEE vs IEEE) (sec) 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0

1.0 0.0 IEEE 1 IEEE 2 5.9 5.9 1.9 1.9 VO 5.5 5.6 1.2 1.2 5.1 5.1 5.0 5.1 0.6 0.6 0.6 0.6 VI BE BK Observation Airtime includes successful transmission time and collision time Airtime = (10s collision time)/2 + collision time

From VO to BE category: CWmin => collision time => Airtime Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Distance X = 10m Airtime Usage (sec) (ETSI vs IEEE) (sec) ETSI IEEE 10.0 8.0 7.4 7.1 5.8 6.0 3.0 2.0 TXOP 5.0 4.0 4.0 0.0 7.1 1.6 1.6

Class 4 vs VO 2ms 2.080ms 1.0 1.0 Class 3 vs VI 4ms 4.096ms 0.8 0.3 Class 2 vs BE 6ms 2.528ms 3.0 0.7 0.3 Class 1 vs BK 6ms 2.528ms Observation ETSI Class 2 and 1 have airtime advantage mainly contributed by using larger TXOP ETSI Class 4 and 3 still has some airtime advantage despite EDCA parameters being the same as ETSIs. We will analyze this case. Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Airtime Usage - Simulation Results (BE & BK use 6ms TXOP Limit) Submission

Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Airtime Usage Distance X = 10m (sec) (IEEE vs IEEE) (sec) 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 5.9 5.9 1.9 1.9 VO 5.5 5.6 1.2 1.2 VI IEEE 1 IEEE 2 5.2 5.2 5.2 5.2

0.5 0.5 0.5 0.5 BE BK Observation Airtime includes successful transmission time and collision time Airtime = (10s collision time)/2 + collision time From VO to BE category: CWmin => collision time => Airtime Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Airtime Usage Distance X = 10m (sec) (ETSI vs IEEE) (sec) 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 TXOP

ETSI IEEE 7.4 5.8 5.0 5.5 1.0 0.5 4.0 1.6 1.6 Class 4 vs VO 2ms 2.080ms 1.0 Class 3 vs VI 4ms 4.096ms 4.9 5.3 5.0 0.5 0.5 0.5 Class 2 vs BE 6ms 6ms Class 1 vs BK 6ms 6ms Observation

All ETSI Class 4, 3, 2, 1 have airtime advantage despite TXOP limit being the same as ETSIs Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Airtime Usage and TP - Analysis Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Factors Affect Medium Access and Utilization EDCA Parameters AIFSN(Td), CWmin, CWmax, TXOP Limit BA time out IEEE waiting for BA timeout issue (LAA uplink ACK is via licensed spectrum) CW Adjustment issue In LAA, it adjusts CW based on reference subframe which is transmitted at least 4ms ago. By doing so, we observed LAA gets slight advantage (delay the doubling of CW) over IEEE, which adjusts the CW based on the last receiving PPDU (0ms ago). Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Issue due to Waiting for BA Timeout

Observation When collision happens LAA transmitter starts to sense the channel once the media become idle immediately after a collision (yellow part). Note LAA uses the licensed band for uplink ack. IEEE transmitter waits for STA to send BA for a duration of 58us (i.e, Wait for BA Timeout), and then starts to sense the channel (yellow part) Thus, LAA has higher channel access probability especially in a high collision environment Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Distance X = 10m VO vs Class 4 (Prob.) IEEE : fixed TXOP 2.08ms ETSI (LAA): scan TXOP 1.9ms ~ 2.4ms TXOP vs CA Prob. 100% 80% 55% 60% 40% 45% 20% 0% 1.9ms 65% 62% 35% 38% 2.0ms 2.1ms Region II 49%

49% 50% 51% 51% ETSI (LAA) 2.2ms 2.3ms 2.4ms Varying LAA TXOP Region I Observation 50% Region I Regardless of TXOP (COT), CA prob. (probability of gaining channel access) is approximately equal Region II Affected by Waiting for BA Timeout Issue ETSI (LAA) gets advantage by easily obtaining the channel after collision Conclusion Submission The red dashed circle shows the CA prob. of current VO vs Class 4 parameters in spec, where Waiting for BA Timeout issue is the main factor cause unfairness of CA prob. The ratio of CA prob. 65% vs 35% here is what was observed in airtime simulation results 7.4s vs 4.0s Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis System TP - Simulation Results Submission Chung-Ta Ku, Mediatek

May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis System TP (Mbps) (IEEE vs IEEE) (Mbps) 60.0 50.0 40.0 30.0 29.4 29.4 34.0 33.6 32.8 34.1 33.7 33.5 20.0 10.0 0.0 VO VI BE IEEE 1 BK IEEE 2 Observation TP is proportional to successful TX time and Data Rate Successful TX time = (10s collision time)/2

From VO to BE category: CWmin => collision time => successful TX time => TP Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis System TP (ETSI vs IEEE) (Mbps) (Mbps) 60.0 51.9 49.3 50.0 50.9 38.2 40.0 31.0 30.0 19.9 19.8 Class 2 vs BE Class 1 vs BK 18.1 20.0 10.0 0.0 Class 4 vs VO TXOP 2ms

2.080ms Class 3 vs VI 4ms 4.096ms ETSI 6ms 2.528ms 6ms 2.528ms IEEE Observation TP is determined by successful TX time and Data Rate The average MAC data rate in simulation are Submission ETST(LAA) MCS28: 84Mbps IEEE MCS8: 75.4Mbps Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis System TP - Simulation Results (based on BE & BK use 6ms TXOP Limit) Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis

System TP (Mbps) (IEEE vs IEEE) (Mbps) 60.0 50.0 40.0 30.0 29.4 29.4 35.9 33.6 32.8 35.6 35.6 35.4 20.0 10.0 0.0 VO VI IEEE 1 BE BK IEEE 2 Observation TP is proportional to successful TX time and Data Rate Successful TX time = (10s collision time)/2 From VO to BE category: CWmin => collision time => successful TX time => TP Submission

Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis (Mbps) System TP (ETSI vs IEEE) (Mbps) 60.0 49.3 50.0 39.0 38.2 40.0 31.0 33.5 Class 3 vs VI Class 2 vs BE 30.0 36.5 34.5 18.1 20.0 10.0 0.0 Class 4 vs VO TXOP 2ms 2.080ms 4ms 4.096ms ETSI

6ms 6ms Class 1 vs BK 6ms 6ms IEEE Observation TP is determined by successful TX time and Data Rate Average MAC data rate in simulation are ETST(LAA) MCS28: 84Mbps IEEE MCS8: 75.4Mbps The differences in TP is the results of BA timeout. Submission Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis CW Adjustment Issue Reference subframe Reference subframe HARQ-ACK for SF0 is ready Update as CW (v1) Use CW (v1) from SF0 HARQ-ACK

for SF3 is ready Update as CW (v2) A: use CW referenced from the last reference subframe transmitted at least 4ms ago 4ms B: use CW referenced from the last reference subframe transmitted immediately before (same as IEEE) Use CW (v2) from SF3 Observation Submission 0ms Previous simulation results (Slide 8 to Slide 22) use mechanism B. When using mechanism A (adopted in LAA), we would see some discrepancy between collision count (occurs 800 times) and doubling CW count (occurs 600 times), which is unexpected When switching LAA to use mechanism B (the same as IEEE), the collision count and doubling CW count can be matched (ex: both occur 800 times) Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis The impact of CWmax To evaluate the impact of CWmax, we use a simplified simulation which contains more devices. (previous OMnet simulation does not have enough devices to reach CWmax) The simulation assumes perfect ED and the TXOP limit of BE is set to 2.528ms (solid line) and 6ms (dashed line, same as ETSI priority class 2), respectively. Total airtime utilization is significantly different (IEEE is less than ETSI PC2).

CWmax = 63 Submission Slide 24 Chung-Ta Ku, Mediatek May 2019 2019-TECH-Mediatek-0895-01-802.11 Coex Sim & Analysis Conclusions System level simulation regarding 802.11 and LAA is presented to evaluate fairness for medium occupancy Multiple factors impacting coexistence fairness were investigated Timeout for BA Default EDCA parameters CW adjustment Proper setting of EDCA Parameters can be used to mitigate the effects of medium utilization (subject to further study) Due to the use of licensed channel, LAA has advantage in medium utilization in some cases Submission Slide 25 Chung-Ta Ku, Mediatek

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