Wi Fi 802 11b and Bluetooth An Examination of Coexistence Approaches Abstract This paper analyzes different approaches to resolving the interference problems between the Wi Fi and Bluetooth wireless technologies This analysis explores the strengths and weaknesses of these interference mitigation approaches and goes on to explain what is necessary for achieving satisfactory combination performance and true Coexistence without Compromise The contents are based on Mobilian Corporation s coexistence research and development work including a thorough analysis of the problems and various experiments to understand the interference issue In investigating different approaches to interference mitigation this paper gives technical data and uses common wireless technology terms The information presented is targeted to readers who have a basic understanding of wireless networking We recommend that readers without this understanding read Mobilian s first white paper Wi Fi 802 11b and Bluetooth Simultaneous Operation Characterizing the Problem www mobilian com April 11 2001 Disclaimer and Copyright Windows Hardware Engineering Conference Author s Disclaimer and Copyright Mobilian TrueRadio Sim OP TrueConnectivity and Coexistence without Compromise are all trademarks of Mobilian Corporation WinHEC Sponsors Disclaimer The contents of this document have not been authored or confirmed by Microsoft or the WinHEC conference co sponsors hereinafter WinHEC Sponsors Accordingly the information contained in this document does not necessarily represent the views of the WinHEC Sponsors and the WinHEC Sponsors cannot make any representation concerning its accuracy THE WinHEC SPONSORS MAKE NO WARRANTIES EXPRESS OR IMPLIED WITH RESPECT TO THIS INFORMATION Microsoft DirectX MS DOS Win32 Win64 Windows and Windows NT are registered trademarks of Microsoft Corporation Other product and company names mentioned herein may be the trademarks of their respective owners An Examination of Coexistence Approaches 2 Table of Contents 1 0 2 0 Executive Summary 3 Background 4 2 1 Technical Background 5 2 1 1 Bluetooth Wireless Personal Area Networking WPAN 5 2 1 2 802 11b Wireless Local Area Networking Wi Fi 6 2 1 3 Wi Fi Bluetooth Interaction and Interference 6 3 0 Interference Mitigation Approaches 8 3 1 Collocation without Coexistence Mechanism 9 3 1 1 Overview 9 3 1 2 Analysis 9 3 2 Driver level Modal Switching Between Wi Fi and Bluetooth 10 3 2 1 Overview 10 3 2 2 Analysis Dual mode Radio Switching 11 3 2 2 1 Dual mode Radio Switching 11 3 2 2 2 Leaving the Network without Signaling 12 3 2 2 3 Leaving the Network with Signaling 12 3 2 3 Analysis Driver level Switching 12 3 2 3 1 Throughput and Time delay Concerns 12 3 2 3 2 Impacts of Bluetooth Polling Activities 14 3 3 Adaptive Hopping 14 3 3 1 Overview 14 3 3 2 Analysis 15 3 3 2 1 Adaptive Hopping as Optional Profile Operational Mode 15 3 3 2 2 Adaptive Hopper Must Accurately Sense and Respond to Interferers 15 3 3 2 2 1 Bluetooth Difficulty in Detecting Wi Fi Signal 16 3 3 2 2 2 Congested Wireless Environments are Particularly Troublesome 17 3 3 2 3 Adjacent Channel Noise 19 3 3 2 4 Number of Channels 19 3 4 MAC level Switching 19 3 4 1 Overview 19 3 4 2 Analysis 19 3 5 Simultaneous Operation 20 3 5 1 Overview 20 3 5 2 Analysis 22 4 0 Summary 22 5 0 Appendix 1 In band versus Out of band Noise 24 5 1 Signals and Noise 24 5 1 1 Types of Noise 24 5 2 Bluetooth and Wi Fi Interference Cases 26 6 0 Appendix 2 Path Loss Models Employed 28 References Error Bookmark not defined Table of Figures Figure 1 Performance Hierarchy of Coexistence Approaches for Collocated Wi Fi Bluetooth 9 Figure 2 Geometry of Measurement and Simulation Environment 10 Figure 3 Measurement of Wi Fi Throughput in the Presence of Collocated Bluetooth 10 Figure 4 Conceptual Wireless System Diagram 11 Figure 5 Basic Geometry of Bluetooth and Wi Fi Penetrated Corporation 17 Figure 6 Likely Location of Two Adaptive Hoppers 18 Figure 7 Simultaneous Operation Covers Entire Conceptual Wireless System Diagram 21 Figure 8 Ganymede Chariot Graph of Mobilian Corporation s TrueRadio Demonstration 22 Figure 9 Mobilian s TrueRadio Performance in Collocated Scenario 23 Figure 10 In Band versus Out Of Band Noise 25 Figure 11 White Noise and Colored Noise are Very Different 25 Figure 12 Typical Transmit Mask 26 Figure 13 Path Loss as a Function of Distance Indoor 2 4 GHz ISM Band 28 2001 Mobilian Corporation All rights reserved An Examination of Coexistence Approaches 3 Executive Summary Wireless markets from wide area networks to local and personal area networks are widely expected to be the significant market of the 21st Century Investment capital is flowing to wireless companies worldwide and market forecasts consistently project hundreds of millions of installed units With this expansion comes increased opportunity for market innovation and consequently wireless penetration into the core fabric of our everyday lives This growth is spurred by increasing demand for maximum convenience and immediate access to desired information It is facilitated by an unlicensed frequency spectrum providing unlimited free access to whomever wishes to build a wireless device capable of complying with regulatory standards These forces are working together to create traffic and device density in the unlicensed frequencies and consequently opportunities for interference between the protocols using those frequencies As these trends develop the need for multiple wireless devices operating at the same time will increase resulting in still greater potential for interference That is why simultaneous operation is becoming an important topic of discussion in today s market Simultaneous operation is the ability of different fully standards compliant wireless systems to operate simultaneously in any scenario while experiencing minimal or no degradation in performance This definition includes wireless devices that can give the user outstanding performance without a list of operational caveats The device should just work regardless of other devices within its operating environment Wireless local area networking WLAN and wireless personal area networking WPAN are two networks in particular for which simultaneous operation is growing in importance WLAN WPAN simultaneous operation will occur more and more frequently as users begin completing everyday tasks such as copying or printing a file from their WLAN PC while using a WPAN enabled mouse