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
conclusion

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