Presentation on theme: "WPAN/WLAN/WWAN Multi-Radio Coexistence"— Presentation transcript:
1 WPAN/WLAN/WWAN Multi-Radio Coexistence IEEE 802 Plenary, AtlantaTuesday, November , 9:00 PM2738Presenters: Jari Jokela (Nokia)Floyd Simpson (Motorola) Artur Zaks (Texas Instruments)Jing Zhu (Intel)Sponsored by Stuart J. Kerry ( WG Chair) with support from Roger B. Marks ( WG Chair)
3 AbstractThis 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 Many Radios with Limited Spectrum and Limited Space MotivationMany Radios with Limited Spectrum and Limited SpaceWi-FiA,B,G,NNear Field CommunicationWiMAX60GHz3GGPSTV- DVBUWBBluetoothFM
6 Comparison of Wi-Fi / WiMAX / Bluetooth* MotivationComparison of Wi-Fi / WiMAX / Bluetooth*Wi-Fi (802.11g)WiMAX (802.16e)BluetoothRange100m1000m3mBandwidth20MHz10MHz1MHzMedia AccessCSMAOFDMATDMAPeek Data Rate54Mbps64Mbps (2x2)3MbpsQoS SupportLowHighMediumSpectrumUnlicensedLicensed / UnlicensedTX Power20dBm24dBm0dBmWireless 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 Multi-Radio Concurrent Usages MotivationMulti-Radio Concurrent UsagesWiMAX CoverageBluetooth CoverageBluetooth CoverageWireless Gatewayon the roadWi-Fi CoverageSeamless Handoverin home / office
8 Coexistence Challenges (1): Inter-Radio Interference MotivationCoexistence Challenges (1): Inter-Radio InterferenceInterfererGPSUWBBTCDMA 1800GSM 800Wi-FiWiMaxCDMA1800VictimThis is about device-level coexistence (not network coexistence)Isolation RequirementsSevere Moderate Cautious No-problem>55db db db <25db
9 Coexistence Challenges (2): Multi-Radio Integration MotivationCoexistence Challenges (2): Multi-Radio IntegrationWi-FiA,B,G,NNear Field CommunicationWiMAX60GHz3GGPSTV- DVBUWBBluetoothFMAntenna 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 SolutionWhat is next? Reconfigurable / Software Defined RadioMulti-radio usage and performance should not be sacrificed
10 Coexistence-related IEEE Standards State of the ArtCoexistence-related IEEE StandardsStandardYear of PublicationScope20012004 (revision)recommended practice for coexistence of fixed broadband wireless access systems2003recommended practice for coexistence of WPAN with other wireless devices operating in unlicensed frequency bands802.11hamendment for spectrum and transmission power management extensions in the 5GHz band in Europe802.16hongoingamendment for improved mechanisms, policies and medium access control enhancements, to enable coexistence among license-exempt systems, and to facilitate the coexistence of such systems with primary users802.19recommended practice for metrics and methods for assessing coexistence of IEEE 802 wireless networksP1900.2technical 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.Lack of coexistence support in air-interface for emerging WPAN/WLAN/WWANmulti-radio device
11 Overview of Coexistence Solutions State of the ArtOverview of Coexistence SolutionsTechniquesIssuesTrueConcurrencyspectrum partition / maskantenna isolationadaptive frequency hoppingtransmission power controldynamic frequency selectionnotch filteringinsufficient with limited isolation (< 30dB) and wideband interferencemay sacrifice performance (e.g. filter reduces dynamic range)media dependent, vendor-specific, component-specific and often not interoperableadditional cost and sizePerceivedtime sharing / MAC coordination with various time granularityconnection (e.g. sec.)period (e.g. ms)packet (e.g. us)best-effortsolutions may not exist if wireless stacks is not aware of coexistence needs (e.g. being active 100% of time)not scalable, and not support component sharingmedia independent, and potentially scalable, but needs air-interface support
12 Case Study: 802.11/802.15.1 Time Sharing Coexistence Mechanisms State of the ArtCase Study: / Time Sharing Coexistence MechanismsBasic Ideasper-packet authorization of all transmissionsarbitrate the radio activity by priority when collision happensOver-The-Air (OTA) Requirementsmaintain radio duty cycles at friendly/low levelprovide flexibility to (re)schedule radio activityforecast schedule for other radios to reactCompressibilitySelectivityPredictability[IEEE , 2003]Table: IEEE packet typesSCO-HV1SCO-HV2SCO-HV3ACLTX Duty Cycle50%25%16.5%VariedRX Duty CycleTotal Duty Cycle100%33%SchedulableNoYesDifficult to support TS coexistenceCommonly used in cellular headsetMost friendly to TS coexistencePTA: Packet Traffic Arbitration, AWMA: Alternating Wireless Medium AccessSCO: Synchronous Connection-Oriented, ACL: Asynchronous Connection-Less, HV: High Quality Voice
13 What is the Problem with Time Sharing (TS)? State of the ArtWhat is the Problem with Time Sharing (TS)?Device ADevice CInter-RadioInterferenceWirelessNetwork 1WirelessNetwork 2TXTX(Multi-Radio)Device BRXRXRadio activities may not always be locally controllable802.11: frame may arrive at any time due to random access802.16: base station to schedule all the activities of a mobile station: master to schedule but usually power constrainedChallenging to provide desirable performance on each of the coexisting radiosthe performance on one radio is usually protected at the cost of the other radio’s performance
14 Today’s OTA Techniques for Time Sharing Coexistence State of the ArtToday’s OTA Techniques for Time Sharing CoexistenceTechniquesIssues802.11Retransmissionill-guided link adaptationUAPSD / Power Saveunpredictable response timenot applicable to AP and IBSSCTS-to-selfsilence the whole channelQuietcoarse granularitysilence the whole BSS802.16Sleep Modelittle guaranteemay conflict with its intended usageScan(eSCO & ACL)master rolelow efficiency due to low data rateCommon ProblemsInexplicit, after-thought and case-specific, and difficult to be applied to new usagesLow reliability and low efficiency due to lack of explicit / reliable support in air-interfaceUAPSD: unscheduled automatic power save delivery, CTS: Clear-To-Send, eSCO: extended SCO
15 State of the ArtLimitations of UAPSDDifficult to predict T4 due to Access Point implementation specifics, varied channel access time and transmission timeUnpredictable AP response time for downlink trafficNot applicable to AP experiencing jamming co-located interferenceswireless residential gatewayNot efficient to use with asymmetric or heavy traffic (e.g. data, video, etc.)video streamingadditional overhead due to trigger frame / PS poll
16 PER Performance with UAPSD State of the ArtPER Performance with UAPSDTwo .11g Links: VoIP + DataVoIP (bi-directional): Mbps, average inter-arrival time = 37.5msData (uplink only): 1000 varied data rate, average inter-arrival time = 500usConfigurationsDL frame sent right after successfully receiving the trigger frametrigger frame only sent out if it will not overlap with the burst intervalsCWmin = 15a) Uplink Triggerb) Downlink DataTwo .11g Links: VoIP (54Mbps)+ Data (Variable)Interference Period: 6 Bluetooth SlotsHigh (up to 40%) downlink PER due to varied channel access time
17 Limitations of 802.16e Sleep Mode State of the ArtLimitations of e Sleep ModeClass AListeningSleepClass BSleep ModeCoexistenceActiveInactiveNot applicable to multiple interferences reports with different patternCoarse granularity: frame duration (5ms)Bluetooth Slot: 625 usinefficient when only a small portion is interferedLittle flexibilityRx and Tx may be treated differently in coexistenceLittle reliability & Best-Effortcoexistence is about avoiding interference and protecting radio activitiesreliability is important, and time info needs to be respectedOther limitationsNot applicable to other states (e.g. network entry)may be intended for other usage (scanning)
18 Recap: Why Time Sharing? Media Independent TSRecap: Why Time Sharing?Power / Frequency control is ineffective in mitigating wideband co-located interferencefurther limited by other network factors, e.g. channel, link budget, etc.not support component sharing due to integrationLow duty-cycle radio activity is possiblebroadband / MIMO techniques more bits/s802.11: 20MHz 40MHz802.16: 5MHz 10MHz 20MHzMIMO: 1x2 2x2 4x4Media independent description of radio activity is possibleHigh Data RateCoverageQoS SupportSecurityLow PowerMobilityMulti-Radio CoexistenceDesign Considerations ofan Air-Interface
19 Media Independent Description of Radio Activity Media Independent TSMedia Independent Description of Radio ActivitytType 1: Duty CycleActiveInactiveTPType 2: Bitmap11111Bt: starting time of an activity cycleT: duration of each activity burst (Type 1)B: bitmap (Type 2)x: time unitP: burst period – i.e., interval between bursts both type 1 and type 2 descriptions can be periodic, and P indicate the duration for one periodN: number of burstss: type of activity: TX, RX, or both
20 Explicit Coexistence Support Media Independent TSExplicit Coexistence SupportExplicit Coexistence Feedbackheterogeneous time granularityBluetooth slot = 625us, Time Unit = 1024us, symbol = 102.9us, frame = 5msRequirement 1: scalable time unitsynchronizationclock driftperiod mismatchRequirement 2: information update & feedback controlExplicit Coexistence Protectionreliable and beyond best-effortlink adaptation, scheduling, etc.Requirement 3: reliable protectionGoal: Media Access Control with multiple constraintsQoS, channel condition, traffic arrival, multi-radio coexistence, …
21 Time Sharing of 802.16 / 802.11 / 802.15.1 Activities Media Independent TSTime Sharing of / / Activities3.75ms625usMSHV3(33%)5msframeStructureDLULDLULDLULActivity (20%)Activity (58%)15msExplicit coexistence support enables seamless time sharing of radio activates, reduces the collisions, and ensures desirable performance on individual radioNote: the pattern may change over time if radios are not in sync
22 What is the benefit? Better User Experience Media Independent TSWhat is the benefit?Better User Experiencesupport more multi-radio concurrent usagescheaper / smaller device without sacrificing functionality & performanceMore efficient usage of wireless medium and spectrumprevent ill-guided air-interface behaviorreduce frame loss and improve reliabilityseamless interaction among radiosEasier and lower cost integration of multiple wireless technologiesunified interface / signalingscale to number of radios and number of vendors
23 802.11v – Co-located Interference Reporting Media Independent TS802.11v – Co-located Interference ReportingSimple protocol enables terminal to indicate it is using several radios simultaneously and performance of WLAN RX is degradedReport allows terminal to indicate interference time characteristics, level, and other informationAutomatic reporting is supported, i.e., whenever STA realize co-located interference is changed it can send Report to APAP 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 logicsAPSTACo-located Interference RequestOther radio operation is started causing performance degradationCo-located Interference ReportOther radio operation is stoppedCo-located Interference Report
24 Media Independent TSBeyond IEEEWi-Fi Alliance Converged Wireless Group (CWG) is working to extend CWG RF Test Plan to cover Bluetooth / Wi-Fi / Cellular coexistence testingBluetooth 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 coexistenceWiMAX 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’ approachKey enabler is power save mode of WiMAX/Wi-Fi for time sharing and BT MAC retransmission capabilityCurrently working on harmonizing on the key WiMAX system requirements to support time sharing at MAC level
25 ConclusionSummaryMulti-radio concurrent usage is becoming the norm, and coexistence is the limiting factorExisting approaches are ineffectivelimited true concurrency (due to cost, size, etc.)best-effort perceived concurrencyMedia independent time-sharing is promising, but coexistence-awareness in air interface is the mustexplicit coexistence feedback / protectionIs a more coordinated approach to support coexistence in wireless necessary, or even possible?
26 ConclusionCall to ActionDevelop standard-based, scalable, and reliable coexistence solutions, considering the following issuesheterogeneous time granularitysynchronizationreliable protectionAdd explicit coexistence support to individual air interface to enablePredictability: forecast activity for other radios to reactCompressibility: maintain radio duty cycles at friendly levelSelectivity: provide flexibility to (re) schedule activity
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