Transcript MSWIM01.ppt

July 21, 01
Interference of Bluetooth and IEEE 802.11:
Simulation Modeling and
Performance Evaluation
N. Golmie, R.E. VanDyck and A. Soltanian
National Institute of Standards and Technology
Gaithersburg, MD 20899
USA
[email protected]
w3.antd.nist.gov
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Outline
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Motivation and Objectives
Related Work
Overview of Bluetooth and WLAN
Simulation Modeling
– Channel, PHY and MAC models
– Simulation Scenario
• Simulation Results
• Summary and Current Work
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Motivation and Objective
• Interference in the 2.4 GHz ISM Band: Bluetooth, HomeRF,
IEEE 802.(11,11-b) devices operating in the same
environment may lead to significant performance
degradation in WPAN and WLAN services.
• Our goal is to evaluate the impact of interference on
Bluetooth and WLAN performance using detailed MAC and
PHY layer simulation models developed to accurately reflect
the interference environment.
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Related Work on Interference Evaluation
• Analytical results based on a probability of packet collision:
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C. F. Chiasserini, R. Rao, “Performance of IEEE 802.11 WLANs in a Bluetooth Environment,”
IEEE Wireless Communications and Networking Conference, WCNC 2000, Chicago IL,
September 2000.
S. Shellhammer, “Packet Error Rate of an IEEE 802.11 WLAN in the Presence of Bluetooth,”
IEEE 802.15-00/133r0, Seattle WA, May 2000.
N. Golmie and F. Mouveaux, “Interference in the 2.4 GHz Band: Impact on the Bluetooth MAC
Access Protocol,” Proceedings of ICC’01, Helsinki, Finland, June 2001.
• Experimental measurements:
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A. Kamerman,”Coexistence between Bluetooth and IEEE 802.11 CCK: Solutions to avoid mutual
interference, IEEE 802.11-00/162r0, July 2000.
I. Howitt et. al.,” Empirical Study for IEEE 802.11 and Bluetooth Interoperability, “ IEEE
VTC’2001, May 2001.
D. Fumolari, Link Performance of an Embedded Bluetooth Personal Area Network, “
Proceedings of IEEE ICC’01, Helsinki Finland, June 2001.
• Simulation Modeling:
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S. Zurbes et.al., “Radio network performance performance of Bluetooth,” Proceedings of ICC’00,
New Orleans, LA, June 2000.
J. Lansford,et.al., “Wi-Fi (802.11b) and Bluetooth Simultaneous Operation: Characterizing the
Problem,”in Mobilian white paper, www.mobilian.com, September 2000.
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Bluetooth Baseband
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
WLAN MAC
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Bluetooth vs 802.11 Specifications
Bluetooth
• 1 Mbits/s data rate with TDMA
structure (polling)
IEEE 802.11
• 1 and 11 Mb/s
– Frequency hopping on a packet
basis
– 625 us slot size, 1 MHz channel
• Approximately 10 m range
– 1 mw to 100 mw Transmitter
Power
– Low Cost Radio Receivers
– Direct Sequence Spread Spectrum
– Complementary Code Keying for
the 11 Mbits/s.
• Carrier Sense Multiple Access with
Collision Avoidance
– Also virtual carrier sense using
request-to-send (RTS) and clear-tosend (CTS) message
• Initially designed for one hop
operation
• Range on the order of 100 m
– 1 Master and up to 7 Slaves
– Scatternets to allow multiple hop
networks
– Up to 1 W Transmitter Power
• Voice (SCO) and data links (ACL)
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
System Simulation Modeling
Bluetooth
Baseband
“1010100101010110”
MAC/PHY Interface
BT Packet
Channel
Propagation
Model
Bluetooth
Baseband
“1010100101010110”
WLAN Packet
Detailed DSP
Transmitter and Receiver
Simulation Models
WLAN MAC
WLAN MAC
BER1 BER2
BER3
MAC/PHY Interface Parameters:
Desired Signal Packet: Type, Power, Frequency, distance (tx, rx)
Interference Packet List: Type, Power, Frequency, distance (tx, rx), Time Offset
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Channel Modeling
• Additive White Gaussian Noise, multipath fading
• Path loss model
32.45  20 log( f .d ) d  8m
Lp  
 58.3  33 log( d / 8) otherwise
• Received power and SIR depend on topology and
device parameters:
PR  PT  LP
SIR  PR  PI
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Physical Layer Modeling
• DSP based implementation of transceivers
• Design using typical parameters (goal is to remain nonimplementation specific)
• Bluetooth
– Non-coherent Limiter Discriminator receiver, Viterbi receiver with
channel estimation and equalization
• IEEE 802.11
– Direct Sequence Spread Spectrum (1 Mbits/s)
– Complementary Code Keying (11 Mbits/s)
– Frequency Hopping (1 Mbits/s)
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
MAC Modeling
• MAC behavioral implementation for Bluetooth and IEEE
802.11 (connection mode)
• Frequency hopping
• Error detection and correction
– Different error correction schemes applied to packet segments
(Bluetooth)
– FCS (802.11)
• Performance statistics collection
– Access delay, packet loss, residual error, throughput
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Simulation Scenarios
WLAN AP
Tx Power 25 mW
Impact of WLAN
Interference
Impact of Bluetooth
on Bluetooth
Interference on WLAN
Performance
Performance
(0,15)
Traffic Distribution for WLAN and BT (LAN Traffic)
Offered Load
30 % Of Channel Capacity
Packet Size
Geometric Distr. Mean 368 bytes
(0,d)
WLAN Mobile
Tx Power 25 mW
Statistics Collection Points
Data
(0,0)
Bluetooth Slave,
Tx Power 1 mW
Bluetooth Master
TX Power 1 mW
(1,0)
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Impact of Interference on Packet Loss
Bluetooth and WLAN (11 Mbits/s)
0.35
0.3
Probability of Packet Loss
WLAN (11 Mbits/s) w BT Voice Interference
0.25
0.2
BT LAN w/ WLAN (11 Mbits/s) Interference
0.15
0.1
BT Voice w/ WLAN (11 Mbits/s) Interference
0.05
WLAN (11 Mbits/s) w/ BT LAN Interference
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Distance of Receiver (BT, WLAN) from Interference Source (BT, WLAN)
(meters)
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Impact of Interference on MAC Access Delay
Bluetooth and WLAN 11 Mbits/s
0.02
Mean Access Delay (seconds)
0.018
0.016
0.014
WLAN (11 Mbits/s) w/ BT LAN Interference
0.012
0.01
BT LAN w/ WLAN (11 Mbits/s) Interference
0.008
0.006
0.004
0.002
WLAN 11 (Mbits/s) w/ BT LAN Interference
0
1
2
3
4
5
6
7
8
9
10
Distance of Receiver (BT, WLAN) from Interference Source (BT, WLAN)
(meters)
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Impact of Interference on Packet Loss
Bluetooth and WLAN (1 Mbits/s)
0.7
0.6
Probability of Packet Loss
WLAN (1 Mbits/s) w / BT Voice Interference
0.5
0.4
0.3
0.2
WLAN (1 Mbits/s) w / BT LAN Interference
0.1
BT LAN w / WLAN (1 Mbits/s) Interference
BT Voice w / WLAN (1 Mbits/s) Interference
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Distance of Receiver (BT, WLAN) from Interference Source (BT, WLAN) (meters)
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Impact of Interference on MAC Access Delay
Bluetooth and WLAN 1 Mbits/s
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Mean Access Delay (seconds)
0.9
0.8
WLAN (1 Mbits/s) w / BT HV1 Interference
0.7
0.6
0.5
0.4
0.3
0.2
0.1
BT LAN w / WLAN (1 Mbits/s) Interference
WLAN 1 (Mbits/s) w / BT LAN Interference
0
1
2
3
4
5
6
7
8
9
10
Distance of Receiver (BT, WLAN) from Interference Source (BT, WLAN) (meters)
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Impact of Interference on Number of Errors in
BT Voice Packets
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Number of Errors
10
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BT HV1 w / WLAN (11 Mbits/s) Interference
6
4
2
BT HV1 w / WLAN (1 Mbits/s) Interference
0
1
2
3
4
5
6
7
8
9
10
Distance of Receiver (BT, WLAN) from Interference Source (BT, WLAN) (meters)
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Summary
• Developed detailed MAC and PHY simulation platform to
study the impact of interference in a closed loop
environment.
– Obtained simulation results for mutual interference scenario.
• Performance depends on accurate traffic models and
distributions.
– Scenarios using Bluetooth voice traffic represent the worse
interference cases (up to 65% of WLAN packets lost).
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Interference of Bluetooth and IEEE 802.11, MSWIM’01
July 21, 01
Current Work
• Evaluate the impact of interference for other scenarios
including:
– Bluetooth, and WLAN Frequency Hopping systems.
– Multiple node scenarios
– Higher layer traffic models (TCP/IP)
• Devise and evaluate coexistence mechanisms:
– Packet scheduling
– Frequency nulling
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Interference of Bluetooth and IEEE 802.11, MSWIM’01