Interference of Bluetooth and IEEE 802.11: Simulation Modeling and Performance Evaluation

1. Interference of Bluetooth and IEEE 802.11: Simulation Modeling and Performance Evaluation N. Golmie, R.E. VanDyck and A. Soltanian National Institute of Standards and Technology Gaithersburg, MD 20899 USA nada.golmie@nist.gov w3.antd.nist.gov

2. Outline • Motivation and Objectives • Related Work • Overview of Bluetooth and WLAN • Simulation Modeling • Channel, PHY and MAC models • Simulation Scenario • Simulation Results • Summary and Current Work

3. Motivation and Objective • Interference in the 2.4 GHz ISM Band: Bluetooth, HomeRF, IEEE 802.(11,11-b) devices operating in the same environment may lead to significant performance degradation in WPAN and WLAN services. • Our goal is to evaluate the impact of interference on Bluetooth and WLAN performance using detailed MAC and PHY layer simulation models developed to accurately reflect the interference environment.

4. Related Work on Interference Evaluation • Analytical results based on a probability of packet collision: • C. F. Chiasserini, R. Rao, “Performance of IEEE 802.11 WLANs in a Bluetooth Environment,” IEEE Wireless Communications and Networking Conference, WCNC 2000, Chicago IL, September 2000. • S. Shellhammer, “Packet Error Rate of an IEEE 802.11 WLAN in the Presence of Bluetooth,” IEEE 802.15-00/133r0, Seattle WA, May 2000. • N. Golmie and F. Mouveaux, “Interference in the 2.4 GHz Band: Impact on the Bluetooth MAC Access Protocol,” Proceedings of ICC’01, Helsinki, Finland, June 2001. • Experimental measurements: • A. Kamerman,”Coexistence between Bluetooth and IEEE 802.11 CCK: Solutions to avoid mutual interference, IEEE 802.11-00/162r0, July 2000. • I. Howitt et. al.,” Empirical Study for IEEE 802.11 and Bluetooth Interoperability, “ IEEE VTC’2001, May 2001. • D. Fumolari, Link Performance of an Embedded Bluetooth Personal Area Network, “ Proceedings of IEEE ICC’01, Helsinki Finland, June 2001. • Simulation Modeling: • S. Zurbes et.al., “Radio network performance performance of Bluetooth,” Proceedings of ICC’00, New Orleans, LA, June 2000. • J. Lansford,et.al., “Wi-Fi (802.11b) and Bluetooth Simultaneous Operation: Characterizing the Problem,”in Mobilian white paper, www.mobilian.com, September 2000.

5. Bluetooth Baseband

6. WLAN MAC

7. Bluetooth vs 802.11 Specifications • IEEE 802.11 • 1 and 11 Mb/s • Direct Sequence Spread Spectrum • Complementary Code Keying for the 11 Mbits/s. • Carrier Sense Multiple Access with Collision Avoidance • Also virtual carrier sense using request-to-send (RTS) and clear-to-send (CTS) message • Range on the order of 100 m • Up to 1 W Transmitter Power Bluetooth • 1 Mbits/s data rate with TDMA structure (polling) • Frequency hopping on a packet basis • 625 us slot size, 1 MHz channel • Approximately 10 m range • 1 mw to 100 mw Transmitter Power • Low Cost Radio Receivers • Initially designed for one hop operation • 1 Master and up to 7 Slaves • Scatternets to allow multiple hop networks • Voice (SCO) and data links (ACL)

8. System Simulation Modeling Bluetooth Baseband Bluetooth Baseband MAC/PHY Interface “1010100101010110” “1010100101010110” Channel Propagation Model BT Packet WLAN Packet Detailed DSP Transmitter and Receiver Simulation Models WLAN MAC WLAN MAC BER3 BER1 BER2 MAC/PHY Interface Parameters: Desired Signal Packet: Type, Power, Frequency, distance (tx, rx) Interference Packet List: Type, Power, Frequency, distance (tx, rx), Time Offset

9. Channel Modeling • Additive White Gaussian Noise, multipath fading • Path loss model • Received power and SIR depend on topology and device parameters:

10. Physical Layer Modeling • DSP based implementation of transceivers • Design using typical parameters (goal is to remain non-implementation specific) • Bluetooth • Non-coherent Limiter Discriminator receiver, Viterbi receiver with channel estimation and equalization • IEEE 802.11 • Direct Sequence Spread Spectrum (1 Mbits/s) • Complementary Code Keying (11 Mbits/s) • Frequency Hopping (1 Mbits/s)

11. MAC Modeling • MAC behavioral implementation for Bluetooth and IEEE 802.11 (connection mode) • Frequency hopping • Error detection and correction • Different error correction schemes applied to packet segments (Bluetooth) • FCS (802.11) • Performance statistics collection • Access delay, packet loss, residual error, throughput

12. Simulation Scenarios Impact of WLAN Interference on Bluetooth Performance Impact of Bluetooth Interference on WLAN Performance WLAN AP Tx Power 25 mW (0,15) Traffic Distribution for WLAN and BT (LAN Traffic) Offered Load 30 % Of Channel Capacity Packet Size Geometric Distr. Mean 368 bytes Data ACK Data ACK (0,d) WLAN Mobile Tx Power 25 mW Statistics Collection Points Bluetooth Master TX Power 1 mW Data (0,0) (1,0) Bluetooth Slave, Tx Power 1 mW

13. Impact of Interference on Packet Loss Bluetooth and WLAN (11 Mbits/s)

14. Impact of Interference on MAC Access DelayBluetooth and WLAN 11 Mbits/s

15. Impact of Interference on Packet Loss Bluetooth and WLAN (1 Mbits/s)

16. Impact of Interference on MAC Access DelayBluetooth and WLAN 1 Mbits/s

17. Impact of Interference on Number of Errors in BT Voice Packets

18. Summary • Developed detailed MAC and PHY simulation platform to study the impact of interference in a closed loop environment. • Obtained simulation results for mutual interference scenario. • Performance depends on accurate traffic models and distributions. • Scenarios using Bluetooth voice traffic represent the worse interference cases (up to 65% of WLAN packets lost).

19. Current Work • Evaluate the impact of interference for other scenarios including: • Bluetooth, and WLAN Frequency Hopping systems. • Multiple node scenarios • Higher layer traffic models (TCP/IP) • Devise and evaluate coexistence mechanisms: • Packet scheduling • Frequency nulling