1 WPAN/WLAN/WWAN Multi-Radio Coexistence Presenters: Jari Jokela (Nokia) Floyd Simpson (Motorola)...

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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)

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

IEEE 802 Plenary, Atlanta Tuesday, November 13 2007, 9:00 PM

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Authors

Name Company Address Phone email Jari Jokela Nokia Visiokatu 3, Tampere,

Finland +358504860445 [email protected]

m Floyd Simpson Motorola 8000 W. Sunrise Blvd

Plantation, FL 33322, USA

1-954-723-5269 [email protected]

Artur Zaks Texas Instruments 26 Zarchin St, Raanana, Israel

+972- 9 7476853

[email protected]

Jing Zhu Intel 2111, NE 25th Ave., Hillsboro, OR 97124

+1 (503) 2647073

[email protected]

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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.

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Agenda

motivation state of the art media independent time sharing conclusion

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Many Radios with Limited Spectrum and Limited Space

Near Field Communication

60GHzUWB BluetoothWiMAX Wi-Fi

A,B,G,N 3G TV- DVB GPS

MotivationMotivation

FM

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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

Unlicensed

TX Power 20dBm 24dBm 0dBm


Wireless technologies have different sweet spots of operation in terms of coverage, QoS, power, throughput, etc.

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.*Other names and brands may be claimed as the property of others.

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Multi-Radio Concurrent Usages

WiMAX CoverageWiMAX Coverage

Wi-Fi CoverageWi-Fi Coverage

Bluetooth CoverageBluetooth Coverage

Bluetooth CoverageBluetooth Coverage

in home / officein home / office

on the road on the road

Seamless HandoverSeamless HandoverSeamless HandoverSeamless Handover


Wireless GatewayWireless Gateway

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Coexistence Challenges (1): Inter-Radio Interference

GPS

UWB

BT

CDMA 1800

GSM 800

Wi-Fi

WiMax

UWBBTCDMA1800GSM 800Wi-FiWiMax

Isolation Requirements

Severe Moderate Cautious No-problem>55db 40-55db 25-40db <25db


Interferer Interferer Victim Victim

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Coexistence Challenges (2): Multi-Radio Integration


Near Field Communication

60GHzUWB BluetoothWiMAX 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

• 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

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Coexistence-related IEEE StandardsStandard Year of

PublicationScope

802.16.2 20012004 (revision)

recommended practice for coexistence of fixed broadband wireless access systems

802.15.2 2003 recommended practice for coexistence of WPAN with other wireless devices operating in unlicensed frequency bands

802.11h 2003 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 802.16 systems, and to facilitate the coexistence of such systems with primary users

802.19 ongoing recommended practice for metrics and methods for assessing coexistence of IEEE 802 wireless networks

P1900.2 ongoing 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.

State of the ArtState of the Art

Lack of coexistence support in air-interface for emerging WPAN/WLAN/WWAN multi-radio device

Lack of coexistence support in air-interface for emerging WPAN/WLAN/WWAN multi-radio device

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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

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


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Case Study: 802.11/802.15.1 Time Sharing Coexistence Mechanisms

[IEEE 802.15.2, 2003][IEEE 802.15.2, 2003]

Basic Ideas• per-packet authorization of all

transmissions• arbitrate the radio activity by priority

when collision happensOver-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-HV1 SCO-HV2 SCO-HV3 ACL

TX Duty Cycle 50% 25% 16.5% Varied

RX Duty Cycle 50% 25% 16.5% Varied

Total Duty Cycle 100% 50% 33% Varied

Schedulable No No No Yes

Table: IEEE 802.15.1 packet typesTable: IEEE 802.15.1 packet types

Commonly used in Commonly used in cellular headsetcellular headset

Most friendly to TS Most friendly to TS coexistencecoexistence

Difficult to support Difficult to support TS coexistenceTS coexistence

Compressibility

Selectivity

Predictability


PTA: Packet Traffic Arbitration, AWMA: Alternating Wireless Medium AccessSCO: Synchronous Connection-Oriented, ACL: Asynchronous Connection-Less, HV: High Quality VoicePTA: Packet Traffic Arbitration, AWMA: Alternating Wireless Medium AccessSCO: Synchronous Connection-Oriented, ACL: Asynchronous Connection-Less, HV: High Quality Voice

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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 radio’s performance

(Multi-Radio) Device B

Device CDevice A

Inter-Radio Interference


TXTX TXTX

RXRX RXRX

Wireless Network 1Wireless Network 1

Wireless Network 2Wireless Network 2

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Today’s OTA Techniques for Time Sharing CoexistenceTechniques Issues

802.11

Retransmission ill-guided link adaptation

UAPSD / Power Save unpredictable response timenot applicable to AP and IBSS

CTS-to-self silence the whole channel

Quiet coarse granularitysilence the whole BSS

802.16

Sleep Mode little guaranteemay conflict with its intended usagecoarse granularity

Scan

802.15.1 Retransmission

(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 SCOUAPSD: unscheduled automatic power save delivery, CTS: Clear-To-Send, eSCO: extended SCO

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Limitations of UAPSD

ACK

Trigger Frame or PS-POLL

(3.75mSec for HV3)

BT Inactivity period (2.5mSec for HV3)

STA

BT_Active

AP

ACKT2T1 T3

DL Data Frame T4

Difficult to predict T4 due Difficult to predict T4 due to Access Point to Access Point implementation specifics, implementation specifics, varied channel access time varied channel access time and transmission timeand 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


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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

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

6 Mbps 9 Mbps 12 Mbps 18 Mbps 24 Mbps 36 Mbps 48 Mbps 54 Mbps

Background Data RatePE

R

Interference Burst Length= 0

Interference Burst Length = 1 BT Slot

Interference Burst Length = 2 BT Slots

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

6 Mbps 9 Mbps 12 Mbps 18 Mbps 24 Mbps 36 Mbps 48 Mbps 54 Mbps

Background Data Rate

PER

Interference Burst Length= 0

Interference Burst Length= 1 BT Slot

Interference Burst Length= 2 BT Slots

a) Uplink Trigger b) Downlink Data


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ListeningListening SleepSleep

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)


Active ActiveInactiveInactive

Class AClass A

Class BClass B

Sleep ModeSleep Mode

CoexistenceCoexistence

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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 TSMedia Independent TS

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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

Active Inactive

t

T

P

Type 1: Duty Cycle

1 0 0 0 1 1 0 0 0 1 1 0 0

Type 2: Bitmap


B

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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, …


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Time Sharing of 802.16 / 802.11 / 802.15.1 Activities

DLDL ULUL

802.15.1 HV3(33%)

802.16 frame Structure

802.16 Activity (58%)802.11 Activity (20%)

MM SS

DLDL ULUL DLDL ULUL

Note: the pattern may change over time if radios are not in sync

625us

5ms


3.75ms

Explicit coexistence support enables seamless time sharing of radio activates, reduces the collisions, and ensures desirable performance on individual radio

Explicit coexistence support enables seamless time sharing of radio activates, reduces the collisions, and ensures desirable performance on individual radio

15ms

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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


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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

APAP STASTA

Co-located Interference RequestCo-located Interference Request

Other radio operation is

started causing

performance degradation


started causing

performance degradation

Co-located Interference ReportCo-located Interference Report


stopped


stopped

Co-located Interference ReportCo-located Interference Report


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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


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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

ConclusionConclusion

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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

ConclusionConclusion

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Thank You

1 WPAN/WLAN/WWAN Multi-Radio Coexistence Presenters: Jari Jokela (Nokia) Floyd Simpson (Motorola)...

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