doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 1 IEEE P Working Group for Wireless Personal Area Networks TM Summary of IEEE WLAN/WPAN Coexistence Mechanisms

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 2 Coexistence Mechanisms Since some WLANs (e.g. IEEE b “Wi-Fi”) and WPANs (e.g. IEEE “Bluetooth”) operate in the same band they interfere with one another. A Coexistence Mechanism is a technique to minimize that interference. Initial Focus on b and Bluetooth

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 3 Coexistence Mechanisms Collaborative Mechanisms –Some form of communication exists between the WLAN and WPAN. –Use this link to provide fair sharing of medium (i.e. air waves) Non-Collaborative Mechanisms –No communication between WLAN and WPAN exists. –Techniques to minimize the effects of the mutual interference

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 4 Collaborative Coexistence Mechanism Intended to be used when b and Bluetooth are in the same physical unit. There are two modes –Alternating Wireless Medium Access (AWMA) –META Both are techniques to schedule WLAN and WPAN transmission to avoid interference.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 5 Collaborative Mechanism The Collaborative Coexistence Mechanism relies on physical signals between the two radios within a common unit (e.g. laptop). These physical signals are used to coordinate timing of the WLAN and WPAN transmissions to avoid interference.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 6 Alternating Wireless Medium Access The IEEE b beacon interval is divided into two subintervals –One subinterval is for WLAN operation –One subinterval is for WPAN operation

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 7 Alternating Wireless Medium Access Time IEEE b beacon interval BT-WLAN boundary WPAN WLAN

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 8 Alternating Wireless Medium Access Since each radio has its own subinterval, both radios will operate properly, with no interference. This works even if the two radio are very close to one another, for example, in the same hand-held computer or PDA. The two radios can be separated from one another by only a few centimeters.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 9 Alternating Wireless Medium Access Only the Bluetooth radio in the portable unit needs to be modified. That Bluetooth radio needs to be the master of the Piconet. Standard Bluetooth-enabled devices work with this approach. Since they are slaves they only speak when spoken to. They naturally stay within Bluetooth interval.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 10 Alternating Wireless Medium Access This approach solves interference from nearby and Bluetooth devices, since all the systems are synchronized. –During the interval, no Bluetooth devices transmit. –During Bluetooth interval, no devices transmit.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 11 META The META acts as a “Traffic Cop” between the WLAN and WPAN Medium Access Control (MAC) layers. META controls which wireless systems has access to the medium on a packet- by-packet basis.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 12 META Dynamic algorithm schedules traffic Knowledge of time-frequency collisions is key –Simultaneous transmission or reception allowed –Tx simultaneous with Rx allowed if not in-band (requires good LNA) –Critical for SCO operation-WLAN can work around in-band collisions This figure does not show polls/nulls, which often dominates Bluetooth traffic Time IEEE b beacon interval (Packet widths are not to scale…) WPAN WLAN

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 13 META Block Diagram META Engine Frequency Collision Map WLAN Stack WLAN FIFO2 WLAN FIFO1 WLAN Modem WLAN Modem Decision Logic Decision Logic Bluetooth Stack Backoff & CCA Tx Event Enable Switch Matrix Bluetooth FIFO

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 14 When to use AWMA and when to use META Use AWMA –When there is a high density of mobile users. –Because AWMA eliminates all WLAN/WPAN interference, even nearby users Use META –When there is lower density of users –Better overall throughput, if limited nearby interference

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 15 Non-Collaborative Coexistence Mechanisms Two approaches are being Standardized: 1. Bluetooth Packet Selection and Scheduling 2.Bluetooth Adaptive Frequency Hopping

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 16 Bluetooth Packet Selection & Scheduling The this is a non-collaborative mechanism in which the Bluetooth devices independently detect the presence of b and determine which channels are utilized by b. Then the Bluetooth piconet does not transmit when it hops into one of the channel occupied by b.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 17 Currently allowed under FCC rules, for both low-power and high-power Bluetooth devices This prevents Bluetooth from interfering with frequency-static systems like b This does not improve the Bluetooth performance. Bluetooth Packet Selection & Scheduling

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 18 Adaptive Frequency Hopping Just like the Bluetooth Packet Scheduling technique, the this is a non-collaborative mechanism in which the Bluetooth devices independently detect the presence of b and determine which channels are utilized by b. In AFH the Bluetooth piconet remaps its hopping sequence to “hop around” the frequency band occupied by b

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 19 FCC NPRM Under Current FCC ruled Adaptive Frequency Hopping is only allowed for low-power (< 1 mw) Bluetooth devices. In May 2001 the FCC issued a Notice of Proposed Rule Making. If this Rule Making issues then Adaptive Frequency Hopping will be allowed under high-power Bluetooth devices.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 20 Adaptive Frequency Hopping This allows Bluetooth and b to share the ISM band by minimizing interference. Both b and Bluetooth see improved performance. Requires modifications to Bluetooth Specification. Currently working with SIG to obtain specification modifications.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 21 Adaptive Frequency Hopping AFH consists of three components Channel classification techniques to determine which channels are “good” and which are “bad” Link Manager Commands to exchange information about “Good” and “Bad” channels Methods of remapping bad channels to good channels.

doc.: IEEE /482r0 Submission October 2001 Steve Shellhammer, Symbol Technologies Slide 22 Status The Coexistence Mechanisms are currently being standardized in the Draft IEEE Recommended Practice.