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WPAN/WLAN/WWAN Multi-Radio Coexistence

WPAN/WLAN/WWAN Multi-Radio Coexistence. IEEE 802 Plenary, Atlanta Tuesday, November 13 2007, 9:00 PM . Presenters: Jari Jokela (Nokia) Floyd Simpson (Motorola) Artur Zaks (Texas Instruments) Jing Zhu (Intel)

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WPAN/WLAN/WWAN Multi-Radio Coexistence

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  1. WPAN/WLAN/WWAN Multi-Radio Coexistence IEEE 802 Plenary, Atlanta Tuesday, November 13 2007, 9:00 PM Presenters: Jari Jokela (Nokia) FloydSimpson (Motorola) Artur Zaks (Texas Instruments) Jing Zhu (Intel) Sponsored by Stuart J. Kerry (802.11 WG Chair) with support from Roger B. Marks (802.16 WG Chair)

  2. Authors

  3. Abstract This presentation gives an overview on multi-radio coexistence with radios operating on adjacent and overlapping unlicensed or licensed frequency bands, covering use cases, problem analysis, and possible directions for solution. It shows that coexistence has to consider both proximity and collocation. Collocation imposes big challenges due to limited isolation and various interference sources. Need for cost-effective solution leads to approach where antennas are shared by multiple radios thus introducing the requirement for multi-radio time resource coordination. Today’s solutions are neither effective, nor scalable with number of radios and number of vendors. Standardization efforts are needed to provide information service, command, and air-interface support necessary for addressing coexistence issues.

  4. Agenda • motivation • state of the art • media independent time sharing • conclusion

  5. Motivation Near Field Communication Wi-Fi A,B,G,N 60GHz UWB Bluetooth GPS TV- DVB WiMAX 3G Many Radios with Limited Spectrum and Limited Space FM

  6. Motivation Comparison of Wi-Fi / WiMAX / Bluetooth* Wireless technologies have different sweet spots of operation in terms of coverage, QoS, power, throughput, etc. *Other names and brands may be claimed as the property of others.

  7. Motivation Multi-Radio Concurrent Usages WiMAX Coverage Bluetooth Coverage Bluetooth Coverage Wireless Gateway on the road Wi-Fi Coverage Seamless Handover in home / office

  8. Motivation WiMax Wi-Fi GSM 800 CDMA1800 BT UWB WiMax Wi-Fi GSM 800 CDMA 1800 BT UWB GPS Coexistence Challenges (1): Inter-Radio Interference Interferer Victim Isolation Requirements Severe Moderate Cautious No-problem >55db 40-55db 25-40db <25db

  9. Motivation Near Field Communication Wi-Fi A,B,G,N 60GHz UWB Bluetooth GPS TV- DVB WiMAX 3G Coexistence Challenges (2): Multi-Radio Integration FM • Antenna sharing is more and more commonly being used for multi-radio integration due to limited space on small form-factor device. • Wi-Fi & Bluetooth Integrated Solution • What is next? Reconfigurable / Software Defined Radio • Multi-radio usage and performance should not be sacrificed

  10. State of the Art Coexistence-related IEEE Standards Lack of coexistence support in air-interface for emerging WPAN/WLAN/WWAN multi-radio device

  11. State of the Art Overview of Coexistence Solutions not scalable, and not support component sharing media independent, and potentially scalable, but needs air-interface support

  12. State of the Art Case Study: 802.11/802.15.1 Time Sharing Coexistence Mechanisms • Basic Ideas • per-packet authorization of all transmissions • arbitrate the radio activity by priority when collision happens • Over-The-Air (OTA) Requirements • maintain radio duty cycles at friendly/low level • provide flexibility to (re)schedule radio activity • forecast schedule for other radios to react Compressibility Selectivity Predictability [IEEE 802.15.2, 2003] Table: IEEE 802.15.1 packet types Difficult to support TS coexistence Commonly used in cellular headset Most friendly to TS coexistence PTA: Packet Traffic Arbitration, AWMA: Alternating Wireless Medium Access SCO: Synchronous Connection-Oriented, ACL: Asynchronous Connection-Less, HV: High Quality Voice

  13. State of the Art What is the Problem with Time Sharing (TS)? Device A Device C • Radio activities may not always be locally controllable • 802.11: frame may arrive at any time due to random access • 802.16: base station to schedule all the activities of a mobile station • 802.15.1: master to schedule but usually power constrained • Challenging to provide desirable performance on each of the coexisting radios • the performance on one radio is usually protected at the cost of the other radio’s performance Inter-Radio Interference Wireless Network 1 Wireless Network 2 TX TX (Multi-Radio) Device B RX RX

  14. State of the Art Today’s OTA Techniques for Time Sharing Coexistence • Common Problems • Inexplicit, after-thought and case-specific, and difficult to be applied to new usages • Low reliability and low efficiency due to lack of explicit / reliable support in air-interface UAPSD: unscheduled automatic power save delivery, CTS: Clear-To-Send, eSCO: extended SCO

  15. State of the Art Limitations of UAPSD Difficult to predict T4 due to Access Point implementation specifics, varied channel access time and transmission time • Unpredictable AP response time for downlink traffic • Not applicable to AP experiencing jamming co-located interferences • wireless residential gateway • Not efficient to use with asymmetric or heavy traffic (e.g. data, video, etc.) • video streaming • additional overhead due to trigger frame / PS poll

  16. State of the Art PER Performance with UAPSD • Two .11g Links: VoIP (54Mbps)+ Data (Variable) • Interference Period: 6 Bluetooth Slots • High (up to 40%) downlink PER due to varied channel access time a) Uplink Trigger b) Downlink Data

  17. State of the Art Limitations of 802.16e Sleep Mode Class A Listening Sleep • Not applicable to multiple interferences reports with different pattern • Coarse granularity: frame duration (5ms) • Bluetooth Slot: 625 us • inefficient when only a small portion is interfered • Little flexibility • Rx and Tx may be treated differently in coexistence • Little reliability & Best-Effort • coexistence is about avoiding interference and protecting radio activities • reliability is important, and time info needs to be respected • Other limitations • Not applicable to other states (e.g. network entry) • may be intended for other usage (scanning) Class B Sleep Mode Coexistence Inactive Active

  18. Media Independent TS Recap: Why Time Sharing? • Power / Frequency control is ineffective in mitigating wideband co-located interference • further limited by other network factors, e.g. channel, link budget, etc. • not support component sharing due to integration • Low duty-cycle radio activity is possible • broadband / MIMO techniques  more bits/s • 802.11: 20MHz  40MHz • 802.16: 5MHz  10MHz  20MHz • MIMO: 1x2  2x2  4x4 • Media independent description of radio activity is possible • High Data Rate • Coverage • QoS Support • Security • Low Power • Mobility • Multi-Radio Coexistence Design Considerations of an Air-Interface

  19. Media Independent TS Media Independent Description of Radio Activity t Active Inactive Type 1: Duty Cycle T P Type 2: Bitmap 1 0 0 0 1 1 0 0 0 1 1 0 0 B • t: starting time of an activity cycle • T: duration of each activity burst (Type 1) • B: bitmap (Type 2) • x: time unit • P: burst period – i.e., interval between bursts •  both type 1 and type 2 descriptions can be periodic, and P indicate the duration for one period • N: number of bursts • s: type of activity: TX, RX, or both

  20. Media Independent TS Explicit Coexistence Support • Explicit Coexistence Feedback • heterogeneous time granularity • Bluetooth slot = 625us, 802.11 Time Unit = 1024us, 802.16 symbol = 102.9us, 802.16 frame = 5ms Requirement 1: scalable time unit • synchronization • clock drift • period mismatch Requirement 2: information update & feedback control • Explicit Coexistence Protection • reliable and beyond best-effort • link adaptation, scheduling, etc. Requirement 3: reliable protection Goal: Media Access Control with multiple constraints • QoS, channel condition, traffic arrival, multi-radio coexistence, …

  21. Media Independent TS Time Sharing of 802.16 / 802.11 / 802.15.1 Activities 3.75ms 625us M S 802.15.1 HV3 (33%) 5ms 802.16 frame Structure DL UL DL UL DL UL 802.16 Activity (58%) 802.11 Activity (20%) 15ms Explicit coexistence support enables seamless time sharing of radio activates, reduces the collisions, and ensures desirable performance on individual radio Note: the pattern may change over time if radios are not in sync

  22. Media Independent TS What is the benefit? • Better User Experience • support more multi-radio concurrent usages • cheaper / smaller device without sacrificing functionality & performance • More efficient usage of wireless medium and spectrum • prevent ill-guided air-interface behavior • reduce frame loss and improve reliability • seamless interaction among radios • Easier and lower cost integration of multiple wireless technologies • unified interface / signaling • scale to number of radios and number of vendors

  23. Media Independent TS 802.11v – Co-located Interference Reporting STA AP • Simple protocol enables terminal to indicate it is using several radios simultaneously and performance of WLAN RX is degraded • Report allows terminal to indicate interference time characteristics, level, and other information • Automatic reporting is supported, i.e., whenever STA realize co-located interference is changed it can send Report to AP • AP can use reported information several ways, 1) it can schedule DL transmissions not to collide with interference slots and 2) it can use information to adjust e.g., rate adaptation and retransmission logics Co-located Interference Request Other radio operation is started causing performance degradation Co-located Interference Report Other radio operation is stopped Co-located Interference Report

  24. Media Independent TS Beyond IEEE • Wi-Fi Alliance Converged Wireless Group (CWG) is working to extend CWG RF Test Plan to cover Bluetooth / Wi-Fi / Cellular coexistence testing • Bluetooth SIG is defining feature requirements for coexistence with broadband wireless access technologies, and Telephony Working Group (TWG) is currently working towards publishing a whitepaper to address Bluetooth/WiMAX coexistence • WiMAX Forum Coexistence Ad-Hoc has reviewed contributions for WiMAX-BT and WiMAX-Wi-Fi coexistence from Motorola, Altair-Semiconductor, Nextwave and others. • Coexistence based on the ‘perceived concurrency’ approach • Key enabler is power save mode of WiMAX/Wi-Fi for time sharing and BT MAC retransmission capability • Currently working on harmonizing on the key WiMAX system requirements to support time sharing at MAC level

  25. Conclusion Summary • Multi-radio concurrent usage is becoming the norm, and coexistence is the limiting factor • Existing approaches are ineffective • limited true concurrency (due to cost, size, etc.) • best-effort perceived concurrency • Media independent time-sharing is promising, but coexistence-awareness in air interface is the must • explicit coexistence feedback / protection • Is a more coordinated approach to support coexistence in wireless necessary, or even possible? • http://www.youtube.com/watch?v=Rh0awIw7PNY

  26. Conclusion Call to Action • Develop standard-based, scalable, and reliable coexistence solutions, considering the following issues • heterogeneous time granularity • synchronization • reliable protection • Add explicit coexistence support to individual air interface to enable • Predictability: forecast activity for other radios to react • Compressibility: maintain radio duty cycles at friendly level • Selectivity: provide flexibility to (re) schedule activity

  27. Thank You

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