1 / 22

IEEE P802.15 Working Group for Wireless Personal Area Networks TM

IEEE P802.15 Working Group for Wireless Personal Area Networks TM. Summary of IEEE 802.15.2 WLAN/WPAN Coexistence Mechanisms. Coexistence Mechanisms.

gyala
Télécharger la présentation

IEEE P802.15 Working Group for Wireless Personal Area Networks TM

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. IEEE P802.15 Working Group for Wireless Personal Area NetworksTM Summary of IEEE 802.15.2 WLAN/WPAN Coexistence Mechanisms Steve Shellhammer, Symbol Technologies

  2. Coexistence Mechanisms • Since some WLANs (e.g. IEEE 802.11b “Wi-Fi”) and WPANs (e.g. IEEE 802.15.1 “Bluetooth”) operate in the same band they interfere with one another. • A Coexistence Mechanism is a technique to minimize that interference. • Initial Focus on 802.11b and Bluetooth Steve Shellhammer, Symbol Technologies

  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 Steve Shellhammer, Symbol Technologies

  4. Collaborative Coexistence Mechanism • Intended to be used when 802.11b 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. Steve Shellhammer, Symbol Technologies

  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. Steve Shellhammer, Symbol Technologies

  6. Alternating Wireless Medium Access • The IEEE 802.11b beacon interval is divided into two subintervals • One subinterval is for WLAN operation • One subinterval is for WPAN operation Steve Shellhammer, Symbol Technologies

  7. Alternating Wireless Medium Access IEEE 802.11b beacon interval BT-WLAN boundary WPAN WLAN Time Steve Shellhammer, Symbol Technologies

  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. Steve Shellhammer, Symbol Technologies

  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. Steve Shellhammer, Symbol Technologies

  10. Alternating Wireless Medium Access • This approach solves interference from nearby 802.11 and Bluetooth devices, since all the systems are synchronized. • During the 802.11 interval, no Bluetooth devices transmit. • During Bluetooth interval, no 802.11 devices transmit. Steve Shellhammer, Symbol Technologies

  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. Steve Shellhammer, Symbol Technologies

  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 IEEE 802.11b beacon interval WPAN WLAN Time (Packet widths are not to scale…) Steve Shellhammer, Symbol Technologies

  13. META Block Diagram Enable WLAN FIFO2 WLAN Modem WLAN FIFO1 WLAN Stack Decision Logic Frequency Collision Map META Engine Backoff & CCA Switch Matrix Tx Event Decision Logic Bluetooth Stack WLAN Modem Bluetooth FIFO Enable Steve Shellhammer, Symbol Technologies

  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 Steve Shellhammer, Symbol Technologies

  15. Non-Collaborative Coexistence Mechanisms • Two approaches are being Standardized: 1. Bluetooth Packet Selection and Scheduling 2. Bluetooth Adaptive Frequency Hopping Steve Shellhammer, Symbol Technologies

  16. Bluetooth Packet Selection & Scheduling • The this is a non-collaborative mechanism in which the Bluetooth devices independently detect the presence of 802.11b and determine which channels are utilized by 802.11b. • Then the Bluetooth piconet does not transmit when it hops into one of the channel occupied by 802.11b. Steve Shellhammer, Symbol Technologies

  17. Bluetooth Packet Selection & Scheduling • Currently allowed under FCC rules, for both low-power and high-power Bluetooth devices • This prevents Bluetooth from interfering with frequency-static systems like 802.11b • This does not improve the Bluetooth performance. Steve Shellhammer, Symbol Technologies

  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 802.11b and determine which channels are utilized by 802.11b. • In AFH the Bluetooth piconet remaps its hopping sequence to “hop around” the frequency band occupied by 802.11b Steve Shellhammer, Symbol Technologies

  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. Steve Shellhammer, Symbol Technologies

  20. Adaptive Frequency Hopping • This allows Bluetooth and 802.11b to share the ISM band by minimizing interference. • Both 802.11b and Bluetooth see improved performance. • Requires modifications to Bluetooth Specification. • Currently working with SIG to obtain specification modifications. Steve Shellhammer, Symbol Technologies

  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. Steve Shellhammer, Symbol Technologies

  22. Status • The Coexistence Mechanisms are currently being standardized in the Draft IEEE 802.15.2 Recommended Practice. Steve Shellhammer, Symbol Technologies

More Related