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1 WPAN/WLAN/WWAN Multi-Radio Coexistence Presenters: Jari Jokela (Nokia) Floyd Simpson (Motorola) Artur Zaks (Texas Instruments) Jing Zhu (Intel) Sponsored.

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Presentation on theme: "1 WPAN/WLAN/WWAN Multi-Radio Coexistence Presenters: Jari Jokela (Nokia) Floyd Simpson (Motorola) Artur Zaks (Texas Instruments) Jing Zhu (Intel) Sponsored."— Presentation transcript:

1 1 WPAN/WLAN/WWAN Multi-Radio Coexistence Presenters: Jari Jokela (Nokia) Floyd Simpson (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) IEEE 802 Plenary, Atlanta Tuesday, November 13 2007, 9:00 PM

2 2 Authors

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

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

6 6 Comparison of Wi-Fi / WiMAX / Bluetooth* Wi-Fi (802.11g) WiMAX (802.16e) Bluetooth Range100m1000m3m Bandwidth20MHz10MHz1MHz Media AccessCSMAOFDMATDMA Peek Data Rate54Mbps64Mbps (2x2)3Mbps QoS SupportLowHighMedium SpectrumUnlicensedLicensed / Unlicensed Unlicensed TX Power20dBm24dBm0dBm Motivation 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 7 Multi-Radio Concurrent Usages WiMAX Coverage Wi-Fi Coverage Bluetooth Coverage in home / office on the road Seamless Handover Motivation Wireless Gateway

8 8 Coexistence Challenges (1): Inter-Radio Interference GPS UWB BT CDMA 1800 GSM 800 Wi-Fi WiMax UWBBT CDMA18 00 GSM 800Wi-FiWiMax Isolation Requirements Severe Moderate Cautious No-problem >55db 40-55db 25-40db <25db Motivation Interferer Victim

9 9 Coexistence Challenges (2): Multi-Radio I ntegration Motivation Near Field Communication 60GHz UWB Bluetooth WiMAX Wi-Fi A,B,G,N 3G TV- DVB GPS 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 10 Coexistence-related IEEE Standards StandardYear of Publication Scope 802.16.22001 2004 (revision) recommended practice for coexistence of fixed broadband wireless access systems 802.15.22003recommended practice for coexistence of WPAN with other wireless devices operating in unlicensed frequency bands 802.11h2003amendment for spectrum and transmission power management extensions in the 5GHz band in Europe 802.16hongoingamendment for improved mechanisms, policies and medium access control enhancements, to enable coexistence among license-exempt 802.16 systems, and to facilitate the coexistence of such systems with primary users 802.19ongoingrecommended practice for metrics and methods for assessing coexistence of IEEE 802 wireless networks P1900.2ongoingtechnical guidelines for analyzing the potential for coexistence or in contrast interference between radio systems operating in the same frequency band or between different frequency bands. State of the Art Lack of coexistence support in air-interface for emerging WPAN/WLAN/WWAN multi-radio device

11 11 TechniquesIssues True Concurrency spectrum partition / mask antenna isolation adaptive frequency hopping transmission power control dynamic frequency selection notch filtering insufficient with limited isolation (< 30dB) and wideband interference may sacrifice performance (e.g. filter reduces dynamic range) media dependent, vendor-specific, component-specific and often not interoperable additional cost and size Perceived Concurrency time sharing / MAC coordination with various time granularity –connection (e.g. sec.) –period (e.g. ms) –packet (e.g. us) best-effort solutions may not exist if wireless stacks is not aware of coexistence needs (e.g. being active 100% of time) Overview of Coexistence Solutions media independent, and potentially scalable, but needs air-interface support not scalable, and not support component sharing State of the Art

12 12 Case Study: 802.11/802.15.1 Time Sharing Coexistence Mechanisms [IEEE 802.15.2, 2003] 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 SCO-HV1SCO-HV2SCO-HV3ACL TX Duty Cycle50%25%16.5%Varied RX Duty Cycle50%25%16.5%Varied Total Duty Cycle100%50%33%Varied SchedulableNo Yes Table: IEEE 802.15.1 packet types Commonly used in cellular headset Most friendly to TS coexistence Difficult to support TS coexistence Compressibility Selectivity Predictability State of the Art PTA: Packet Traffic Arbitration, AWMA: Alternating Wireless Medium Access SCO: Synchronous Connection-Oriented, ACL: Asynchronous Connection-Less, HV: High Quality Voice

13 13 What is the Problem with Time Sharing (TS)? 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 radios performance (Multi-Radio) Device B Device CDevice A Inter-Radio Interference State of the Art TX RX Wireless Network 1 Wireless Network 2

14 14 Todays OTA Techniques for Time Sharing Coexistence TechniquesIssues 802.11 Retransmission ill-guided link adaptation UAPSD / Power Save unpredictable response time not applicable to AP and IBSS CTS-to-self silence the whole channel Quiet coarse granularity silence the whole BSS 802.16 Sleep Mode little guarantee may conflict with its intended usage coarse granularity Scan 802.15.1Retransmission (eSCO & ACL) master role low efficiency due to low data rate 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 State of the Art UAPSD: unscheduled automatic power save delivery, CTS: Clear-To-Send, eSCO: extended SCO

15 15 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 State of the Art

16 16 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 State of the Art

17 17 Listening Sleep Limitations of 802.16e Sleep Mode 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) State of the Art Active Inactive Class A Class B Sleep Mode Coexistence

18 18 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 Media Independent TS

19 19 Media Independent Description of Radio Activity 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 ActiveInactive t T P Type 1: Duty Cycle 1000110001100 Type 2: Bitmap Media Independent TS B

20 20 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, … Media Independent TS

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

22 22 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 Media Independent TS

23 23 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 802.11v – Co-located Interference Reporting AP STA 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 Media Independent TS

24 24 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 Media Independent TS

25 25 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? Conclusion

26 26 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 Conclusion

27 27 Thank You

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