11n 40 MHz and BT coexistence test results

1. 11n 40 MHz and BT coexistence test results Authors:

2. Objective • Measure performance impact on 802.11n and Bluetooth (BT) when 802.11n operates in 20 MHz and 40 MHz • Measurements made in accordance to test scenarios specified in [1] and [2] • Test Scenarios • BT Profiles: SCO, ACL and A2DP • 802.11n: 20 MHz/40 MHz Harish Ramamurthy, Marvell Semiconductor Inc.

3. Test Setup • Anechoic shielded room used • Separation of WLAN devices is 3m due to test facility constraints • 11g performance not measured due to time constraints • Laptop is the primary 802.11n transmitter • 802.11n Setup • Throughput test using IxChariot • Aggregation ON and video priority used to maximize medium utilization Harish Ramamurthy, Marvell Semiconductor Inc.

4. BT Adaptive Frequency Hopping (AFH) Definitions • AFH off • All 79 MHz channels are used and none of the channels are blocked • AFH on: Two types of AFH used • Manual AFH • Manually remove or blacklist channels that get affected by 802.11 and some margin at the edges. • For e.g. when using 40 MHz with 2, 6 channel, block all lower channels (except for first four) and enable all higher channels (top twenty seven) • Regular AFH • Present results with both regular and manual AFH Harish Ramamurthy, Marvell Semiconductor Inc.

5. Tests Outline • Quantitative Test Setups • #1: SCO: Measure Mean Opinion Score (MOS) • #2: ACL: Measure BT throughput • Qualitative Test Setups • #4: SCO • #5.1: A2DP: Distance between BT and 802.11n = 0.5 meters • #5.2: A2DP: Distance between BT and 802.11n = 0.5 meters • #5.3: A2DP: Distance between BT and 802.11n = 1.5 meters Harish Ramamurthy, Marvell Semiconductor Inc.

6. Test Setup #1: BT SCO performance • Refers to use-case 1 of [1] & [2]. Adjustments • 22 Mbps data rate not measured due to time constraints • Setup • Refer slide 3. • Bluetooth Setup • SCO link: MOS measured using PESQ P.862 method • AFH on: Manual AFH was used • The tester was standing between bluetooth devices Harish Ramamurthy, Marvell Semiconductor Inc.

7. Test Setup #1: BT SCO performance Harish Ramamurthy, Marvell Semiconductor Inc.

8. Test Setup #2: ACL performance • Setup • Refer slide 3. • Bluetooth Setup • ACL link: 10000 packets of length 160 bytes of type DH5 • Maximum achievable throughput in this configuration is about 315 kbps • BT performance: Measure throughput • AFH on: Manual AFH was used Harish Ramamurthy, Marvell Semiconductor Inc.

9. Test Setup #2: ACL performance Harish Ramamurthy, Marvell Semiconductor Inc.

10. Discussion: Quantitative Test Results • 802.11n High medium utilization (No throughput throttling) • Without AFH, performance of BT degrades in the presence of 802.11n for both 20 and 40MHz • MOS is not acceptable for both 20 MHz and 40 MHz • 802.11n throughput also gets severely affected (down 30 %) • Manual AFH greatly improves the performance of BT in the presence of 802.11n for both 20 and 40MHz • MOS is comparable for 20 MHz and 40 MHz • 802.11n throughput has slight degradation • 802.11n Low medium utilization (1 Mbps) • 802.11n and BT performance are not degraded considerably (<10%) Harish Ramamurthy, Marvell Semiconductor Inc.

11. Qualitative Tests • Perception tests for audio quality of BT SCO and A2DP in presence of 802.11n 20 MHz and 40 MHz • The data presented here is for reference only and it is not intended to be interpreted as comparing different implementations and their performance. Results are presented for limited number of scenarios • Note • “blips”: minor interruption in audio of duration <2 second • “dropouts”: major interruption in audio of duration >= 2seconds Harish Ramamurthy, Marvell Semiconductor Inc.

12. Test Setup #4: BT SCO – Qualitative Tests • Equipment • Plantronics Voyager 855 headset and Marvell BT • Setup similar to use-case 1 of [1] & [2]. Adjustments • 22 Mbps data rate not measured due to time constraints • AFH • Regular AFH Harish Ramamurthy, Marvell Semiconductor Inc.

13. Test Setup #4: BT SCO – Qualitative Test Results • AFH Disabled • 802.11n: No throughput throttling • 20 MHz: Audio is distorted but remains intelligible (on the threshold of being acceptable/unacceptable) • 40 MHz: Audio is heavily distorted and marginally intelligible (unacceptable) • Running 1 Mbps (Both 20 MHz and 40 MHz) • Audio quality is very good but do hear occasional dropouts (not often) • AFH Enabled • Regular AFH • 802.11n: No throughput throttling • Audio quality was very good for both 20 MHz and 40 MHz • With 40 MHz hear slightly higher number of dropouts • 802.11n: 1 Mbps throughput. For both 20 MHz and 40 MHz: • No audible effect Harish Ramamurthy, Marvell Semiconductor Inc.

14. Test Setup #5.1: BT A2DP • Equipment • Marvell BT Devices • Setup similar to use-case 3 of [1] & [2]. Refer slide 4. • AFH • Manual AFH Harish Ramamurthy, Marvell Semiconductor Inc.

15. Test Setup #5.1: BT A2DP – No 802.11n throughput throttling – Qualitative Test Results Harish Ramamurthy, Marvell Semiconductor Inc.

16. Test Setup #5.1: BT A2DP – Varying Throughput – Qualitative Test Results * Empirical search: Throughput was varied in steps of 5 Mbps Harish Ramamurthy, Marvell Semiconductor Inc.

17. Test Setup #5.2: BT A2DP – Qualitative Tests • Equipment • Plantronics Pulsar 590A headset and stereo adapter • Setup similar to use-case 3 of [1] & [2]. Adjustments: • 22 Mbps data rate not measured due to time constraints • AFH • Regular AFH Harish Ramamurthy, Marvell Semiconductor Inc.

18. Test Setup #5.2 : BT A2DP – Qualitative Test Results • AFH Disabled • 802.11n: No throughput throttling. For both 20 MHz and 40 MHz • Lots of dropouts. Audio quality was not acceptable • 1 Mbps (Both 20 MHz and 40 MHz) • Audio quality is very good but hear dropouts occasionally • AFH Enabled • 802.11n: No throughput throttling • 20 MHz: Periods of music and periods of dropouts. • 40 MHz: Lots of dropouts. Audio quality was not acceptable • Regular AFH algorithm i.e. no manual blacklisting Harish Ramamurthy, Marvell Semiconductor Inc.

19. Test Setup #5.3: BT A2DP • Equipment • Plantronics Pulsar 590A headset and stereo adapter • Setup similar to use-case 3 of [1] & [2]. Adjustments: • Increased distance between 802.11 tx and BT tx to 1.5m • 22 Mbps data rate not measured due to time constraints • AFH • Regular AFH algorithm i.e. no manual blacklisting Harish Ramamurthy, Marvell Semiconductor Inc.

20. Test Setup #5.3: BT A2DP –Qualitative Test Results • AFH Disabled • 802.11n: No throughput throttling • 20 MHz: Audio quality is good but do hear blips • 40 MHz: Audio quality is good but because of higher dropouts it is not acceptable • AFH Enabled • 802.11n: No throughput throttling • 20 MHz: Audio quality is very good • 40 MHz: Audio quality is good to very good with some blips Harish Ramamurthy, Marvell Semiconductor Inc.

21. Discussion: Qualitative Test Results • SCO • No tests were done with manual AFH • With regular AFH enabled, the audio went from unacceptable to near perfect • A2DP • With regular AFH • With distance between BT Tx and 802.11 Tx equal to 0.5 m, audio quality for both 20 MHz and 40 MHz was unacceptable • With distance increased to 1.5 m, audio quality improved significantly for both 20 MHz and 40 MHz • Note: The headset remained 0.5 m away from 802.11n Tx. This still emulates a user working on a laptop while listening to music and amounts to moving the BT tx (stereo) away by 1m • With manual AFH • Audio quality is good in both 20 MHz and 40 MHz Harish Ramamurthy, Marvell Semiconductor Inc.

22. References [1] “11n 40MHz BT test cases”, Eldad Perahia (Intel) et al • Available at https://mentor.ieee.org/802.11/file/08/11-08-0971-00-000n-11n-40mhz-bt-test-cases.ppt [2] “Bluetooth test cases for 802.11n 40 MHz”, John R. Barr (Motorola) et al • Available at https://mentor.ieee.org/802.11/file/08/11-08-0984-00-000n-bluetooth-test-cases-for-802-11n-40-mhz.ppt Harish Ramamurthy, Marvell Semiconductor Inc.

23. Backup Slides Setup, detailed test results etc.

24. Test Setup #1: SCO performance Harish Ramamurthy, Marvell Semiconductor Inc.

25. Test Setup #1: SCO performance with 1Mbps 11n Throughput Harish Ramamurthy, Marvell Semiconductor Inc.

26. Test Setup #2: ACL performance Harish Ramamurthy, Marvell Semiconductor Inc.

27. Test Setup #2: ACL performance – 802.11n 1 Mbps throughput Harish Ramamurthy, Marvell Semiconductor Inc.