20/40MHz BT Experiments

1. 20/40MHz BT Experiments Authors: Date: 2009-05-10 Vinko Erceg, Broadcom

2. Introduction • In this presentation we report on performance of a pair of Bluetooth devices in the presence of 20 MHz and forced 40 MHz WLAN transmissions (also two additional BT transmissions in one experiment) • The experiments were performed in a controlled environment – laboratory screen room (with open and closed door) Vinko Erceg, Broadcom

3. Description of the setup • WLAN traffic: • Production .11n STA • Production .11n AP • Fully loaded bidirectional traffic generated using IPERF • 20MHz and 40MHz transmissions • BT ACL traffic: • Production master device • Production slave device • ACL mode DM5 (approximately 1 Mbps) traffic was streamed from master to the slave Bluetooth device Vinko Erceg, Broadcom

4. BT Device Parameters • Class II BT Master: +4dBm transmit power • Standard low gain omnidirectional antennas • AFH algorithm enabled • When measured in the laboratory screen room BT AFH algorithm masks off 43 MHz in the presence of the WLAN 40 MHz transmissions only • When measured in the laboratory screen room BT AFH algorithm masks off 23 MHz in the presence of the WLAN 20 MHz transmissions only Vinko Erceg, Broadcom

5. Experiment Setup 1 • Separation between BT devices and 20/40MHz laptop was 0.5m • BT master and slave were connected to laptops • WLAN channels: primary 6, secondary 2 20/40MHz AP 20/40MHz STA 2m Distance BT Master BT Slave ISM Band Spectrum Display Vinko Erceg, Broadcom

6. Experiment Setup 2 • Separation between BT Slave and 20/40MHz laptop was 0.5m • Separation between BT Master and 20/40MHz laptop was 1m • BT Master was under the table, non-line-of-sight to BT slave • BT master and slave were connected to laptops • WLAN channels: primary 6, secondary 2 20/40MHz AP 20/40MHz STA 2m Distance BT Slave BT Master ISM Band Spectrum Display Vinko Erceg, Broadcom

7. Experiment Setup 3 Distant 20MHz WLAN signal • Same as experiment setup 1 but with the screen room door open: distant 20 MHz WLAN signal occupied channel 6 at the power level of approximately 25 dB lower than the STA received power, measured at the BT slave • Original WLAN AP and STA transmitted signals on channel 1, 20 MHz only 20 MHz AP 20 MHz STA 2m Distance BT Slave BT Master OPEN DOOR ISM Band Spectrum Display Vinko Erceg, Broadcom

8. Experiment Setup 4 Distant 20MHz WLAN signal • Same as experiment setup 3 with addition of two distant BT signals (3-10m away, signals arriving through the screen room open door, same as distant WLAN signal) • Original WLAN AP and STA transmitted signals on channel 1, 20 MHz only 20 MHz AP 20 MHz STA BT signal 2m Distance BT signal BT Slave BT Master OPEN DOOR ISM Band Spectrum Display Vinko Erceg, Broadcom

9. Measurement Procedure for Setups 1 and 2 • Both Master and Slave BT devices were reset before every measurement run to make sure that AFH masking was reset • BT devices established connection and nominal throughput was measured for 20-30 seconds • After that WLAN bi-directional traffic was started and run for 60 seconds • After WLAN traffic was stopped BT devices were run for additional 20-30 seconds Vinko Erceg, Broadcom

10. Measurement Procedure for Setup 3 • Both Master and Slave BT devices were reset before every measurement run to make sure that AFH masking was reset • BT devices established connection and nominal throughput was measured for 20-30 seconds with the presence of a distant 20 MHz WLAN signal on channel 6 • After that 20 MHz WLAN bi-directional traffic was started on channel 1 and run for 60 seconds • After WLAN traffic was stopped BT devices were run for additional 20-30 seconds with the presence of a 20 MHz distant WLAN signal on channel 6 Vinko Erceg, Broadcom

11. Measurement Procedure for Setup 4 • Both Master and Slave BT devices were reset before every measurement run to make sure that AFH masking was reset • BT devices established connection and nominal throughput was measured for 20-30 seconds with the presence of a distant 20 MHz WLAN signal on channel 6 and two distant BT signals • After that 20 MHz WLAN bi-directional traffic was started on channel 1 and run for 60 seconds • After WLAN traffic was stopper BT devices were run for additional 20-30 seconds with the presence a 20 MHz distant WLAN signal on channel 6 and two distant BT signals Vinko Erceg, Broadcom

12. BT Throughput and Retransmissions Results: Setup 1 – 20 MHz WLAN 20MHz on 20MHz off Vinko Erceg, Broadcom

13. BT Throughput and Retransmissions Results: Setup 1 – 40 MHz WLAN 40MHz on 40MHz off Vinko Erceg, Broadcom

14. BT Throughput and Retransmissions Results: Setup 2 – 20 MHz WLAN 20MHz on 20MHz off Vinko Erceg, Broadcom

15. BT Throughput and Retransmissions Results: Setup 2 – 40 MHz WLAN 40MHz on 40MHz off Vinko Erceg, Broadcom

16. BT Throughput and Retransmissions Results: Setup 3 – 2 x 20 MHz WLAN 20MHz on 20MHz off Vinko Erceg, Broadcom

17. Side-to-Side Comparison: 40 MHz vs. Two 20 MHz WLAN Two 20 MHz WLAN 40 MHz WLAN Vinko Erceg, Broadcom

18. BT Throughput and Retransmissions Results: Setup 4 – 2 x 20 MHz WLAN and 2 x BT 20MHz on 20MHz off Vinko Erceg, Broadcom

19. Conclusions • BT performance in the presence of 40 MHz WLAN transmissions is comparable to the common scenario of traffic from two 20 MHz WLAN networks • No significant BT throughput loss and retransmissions were observed in the case of 20 MHz, 40 MHz WLAN, nor two 20 MHz WLAN transmissions • When either 20 MHz or 40 MHz WLAN traffic is activated, BT AFH algorithm takes short time to adapt • Most BT retransmissions were observed in the presence of the two 20 MHz WLAN signals with two additional BT signals Vinko Erceg, Broadcom