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WPAN/WLAN/WWAN Multi-Radio Coexistence

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Presentation on theme: "WPAN/WLAN/WWAN Multi-Radio Coexistence"— Presentation transcript:

1 WPAN/WLAN/WWAN Multi-Radio Coexistence
IEEE 802 Plenary, Atlanta Tuesday, November , 9:00 PM 2738 Presenters: 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)

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

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

6 Comparison of Wi-Fi / WiMAX / Bluetooth*
Motivation Comparison of Wi-Fi / WiMAX / Bluetooth* Wi-Fi (802.11g) WiMAX (802.16e) Bluetooth Range 100m 1000m 3m Bandwidth 20MHz 10MHz 1MHz Media Access CSMA OFDMA TDMA Peek Data Rate 54Mbps 64Mbps (2x2) 3Mbps QoS Support Low High Medium Spectrum Unlicensed Licensed / Unlicensed TX Power 20dBm 24dBm 0dBm 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 Multi-Radio Concurrent Usages
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 Coexistence Challenges (1): Inter-Radio Interference
Motivation Coexistence Challenges (1): Inter-Radio Interference Interferer GPS UWB BT CDMA 1800 GSM 800 Wi-Fi WiMax CDMA1800 Victim This is about device-level coexistence (not network coexistence) Isolation Requirements Severe Moderate Cautious No-problem >55db db db <25db

9 Coexistence Challenges (2): Multi-Radio Integration
Motivation Coexistence Challenges (2): Multi-Radio Integration Wi-Fi A,B,G,N Near Field Communication WiMAX 60GHz 3G GPS TV- DVB UWB Bluetooth 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 Coexistence-related IEEE Standards
State of the Art Coexistence-related IEEE Standards Standard Year of Publication Scope 2001 2004 (revision) recommended practice for coexistence of fixed broadband wireless access systems 2003 recommended practice for coexistence of WPAN with other wireless devices operating in unlicensed frequency bands 802.11h amendment for spectrum and transmission power management extensions in the 5GHz band in Europe 802.16h ongoing amendment 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 users 802.19 recommended practice for metrics and methods for assessing coexistence of IEEE 802 wireless networks P1900.2 technical 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/WWAN multi-radio device

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

12 Case Study: 802.11/802.15.1 Time Sharing Coexistence Mechanisms
State of the Art Case Study: / 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 , 2003] Table: IEEE packet types SCO-HV1 SCO-HV2 SCO-HV3 ACL TX Duty Cycle 50% 25% 16.5% Varied RX Duty Cycle Total Duty Cycle 100% 33% Schedulable No Yes 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 What is the Problem with Time Sharing (TS)?
State of the Art What is the Problem with Time Sharing (TS)? Device A Device C Inter-Radio Interference Wireless Network 1 Wireless Network 2 TX TX (Multi-Radio) Device B RX RX 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 : 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

14 Today’s OTA Techniques for Time Sharing Coexistence
State of the Art Today’s OTA Techniques for Time Sharing Coexistence Techniques Issues 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 Scan (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 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 PER Performance with UAPSD
State of the Art PER Performance with UAPSD Two .11g Links: VoIP + Data VoIP (bi-directional): Mbps, average inter-arrival time = 37.5ms Data (uplink only): 1000 varied data rate, average inter-arrival time = 500us Configurations DL frame sent right after successfully receiving the trigger frame trigger frame only sent out if it will not overlap with the burst intervals CWmin = 15 a) Uplink Trigger b) Downlink Data Two .11g Links: VoIP (54Mbps)+ Data (Variable) Interference Period: 6 Bluetooth Slots High (up to 40%) downlink PER due to varied channel access time

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

18 Recap: Why Time Sharing?
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 Description of Radio Activity
Media Independent TS Media Independent Description of Radio Activity t Type 1: Duty Cycle Active Inactive T P Type 2: Bitmap 1 1 1 1 1 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 Explicit Coexistence Support
Media Independent TS Explicit Coexistence Support Explicit Coexistence Feedback heterogeneous time granularity Bluetooth slot = 625us, Time Unit = 1024us, symbol = 102.9us, 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 Time Sharing of 802.16 / 802.11 / 802.15.1 Activities
Media Independent TS Time Sharing of / / Activities 3.75ms 625us M S HV3 (33%) 5ms frame Structure DL UL DL UL DL UL Activity (20%) Activity (58%) 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 What is the benefit? Better User Experience
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

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

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?

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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