March 2002

J. del Prado and S. Choi, PhilipsSlide 1

doc.:IEEE 802.11-02/223r1

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CC/RR Performance Evaluation CC/RR Performance Evaluation - Revisited- Revisited

Javier del Prado and Sunghyun ChoiPhilips Research USA

Briarcliff Manor, New Yorksunghyun.choi@philips.com

March 2002

J. del Prado and S. Choi, PhilipsSlide 2

doc.:IEEE 802.11-02/223r1

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Simulation GoalSimulation Goal

• In 01/571r0 the results showed a better performance with CC/RR compared to straight PCF– Straight PCF does poll all the stations

• These results were not enough to validate the CC/RR mechanism– HCF should not implement a straight polling, so it is

not a good comparison

• We show new scenarios with more simulation results for further discussion

March 2002

J. del Prado and S. Choi, PhilipsSlide 3

doc.:IEEE 802.11-02/223r1

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Simulation Model Simulation Model

• Used the simulation model provided by AT&T

• The results in 01/571 were obtained with the same simulation model

• Modified to support new scenarios• It supports:

– DCF– PCF (or HCF without TXOP, working in CFP only)– CC/RR– Direct STA-to-STA transmission

March 2002

J. del Prado and S. Choi, PhilipsSlide 4

doc.:IEEE 802.11-02/223r1

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Simulation ScenariosSimulation Scenarios

• 1 AP, 6 voice STAs and 23 FTP heavy and HTTP heavy STAs

• The application parameters are taken from 01/571r1. – All the application start after 100 sec from

the simulation start.

• The WLAN parameters are the same as in 01/571r1. – Beacon interval of 20 ms with CFP of 18 ms

March 2002

J. del Prado and S. Choi, PhilipsSlide 5

doc.:IEEE 802.11-02/223r1

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Simulation ScenariosSimulation Scenarios

March 2002

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doc.:IEEE 802.11-02/223r1

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Simulation ScenariosSimulation Scenarios

March 2002

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doc.:IEEE 802.11-02/223r1

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Simulation ScenariosSimulation Scenarios

• 4 different simulation scenarios:1)Standing Poll (legacy PCF)

- All STA & AP set for Standing Poll- All STA are polled using “Round Robin”- One STA is polled continuously while

it has more data- The CFP ends when all STA have been polled

2)CC/RR- All STA & AP set for CC/RR- CC Parameters chosen from 01/571r0- Polling list updated using RR information- The STAs are polled while enough time in the CFP

Simulated in

01/571r0

March 2002

J. del Prado and S. Choi, PhilipsSlide 8

doc.:IEEE 802.11-02/223r1

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Simulation ScenariosSimulation Scenarios

• New simulation scenarios:3) Polling only voice stations and downlink

traffic to voice stations during CFP- Data downlink traffic transmitted during CP- After polling all voice stations, CFP ends- “Round Robin” polling- A voice STA is polled while it has more data to send

4) Polling voice stations and all downlink traffic during CFP- Uplink data traffic is transmitted during CP

March 2002

J. del Prado and S. Choi, PhilipsSlide 9

doc.:IEEE 802.11-02/223r1

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ThroughputThroughput (moving average of 240) (moving average of 240)

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J. del Prado and S. Choi, PhilipsSlide 10

doc.:IEEE 802.11-02/223r1

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LoadLoad (moving average of 240) (moving average of 240)

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doc.:IEEE 802.11-02/223r1

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Data Dropped APData Dropped AP

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doc.:IEEE 802.11-02/223r1

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Delay (global)Delay (global)

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J. del Prado and S. Choi, PhilipsSlide 13

doc.:IEEE 802.11-02/223r1

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Delay (II)Delay (II) (without Standing Poll) (without Standing Poll)

March 2002

J. del Prado and S. Choi, PhilipsSlide 14

doc.:IEEE 802.11-02/223r1

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Control Traffic Received at APControl Traffic Received at AP

March 2002

J. del Prado and S. Choi, PhilipsSlide 15

doc.:IEEE 802.11-02/223r1

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Control Traffic sent by APControl Traffic sent by AP

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J. del Prado and S. Choi, PhilipsSlide 16

doc.:IEEE 802.11-02/223r1

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Media Access Delay at Voice STA 1Media Access Delay at Voice STA 1

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Media Access Delay at Voice STA #19Media Access Delay at Voice STA #19

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doc.:IEEE 802.11-02/223r1

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Voice Throughput per STAVoice Throughput per STA

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J. del Prado and S. Choi, PhilipsSlide 19

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FTP Traffic servedFTP Traffic served (moving average of 240) (moving average of 240)

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HTTP Traffic servedHTTP Traffic served(moving average of 240)(moving average of 240)

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FTP download timeFTP download time(moving average of 10)(moving average of 10)

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J. del Prado and S. Choi, PhilipsSlide 22

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HTTP Page Response TimeHTTP Page Response Time(moving average of 10)(moving average of 10)

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J. del Prado and S. Choi, PhilipsSlide 23

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HTTP Object Response TimeHTTP Object Response Time(moving average of 10)(moving average of 10)

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J. del Prado and S. Choi, PhilipsSlide 24

doc.:IEEE 802.11-02/223r1

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Conclusions (I)Conclusions (I)

• The scenario was designed to demonstrate the utility of CC/RR. However, comparable performance was achieved without CC/RR.– CC/RR mechanism may even degrade the

overall performance in some cases due to the unnecessary overhead.

• Parameterized QoS streaming will not need the CC/RR mechanism.

• Resource request can be done via QoS Null or another management frame.

March 2002

J. del Prado and S. Choi, PhilipsSlide 25

doc.:IEEE 802.11-02/223r1

Submission

Conclusions (II)Conclusions (II)

• We believe that the performance w/o CC/RR can be better via more intelligent scheduling

• Note that …– HC can poll voice STAs during the CP (not

implemented in the current simulation model)– HC can get information in the QoS control field

of data frames (not implemented in the current simulation model)

• CC/RR complexity is not justified!

March 2002

J. del Prado and S. Choi, PhilipsSlide 26

doc.:IEEE 802.11-02/223r1

Submission

MotionMotion

• Instruct editor to remove all the references to CC/RR & CCI mechanism in the draft

• This motion directly addresses the following comments :– 785 (Ecclesine), 783, 786, 1085 (Sanwalka),

787 (Singla), 788 (Stephans), 932,1667 (Chesson), 2000 (Choi), 1662 (Diepstraten), 1666 (Myles), 1856 (Willams)