Intelligent Wireless Local Area Networking

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Intelligent Wireless Local Area Networking

• Qualifying Exam
• Mustafa Ergen

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• Degrees
• BS Middle East Technical University, 2000
• MS University of California Berkeley, 2002
• Selected Publications
• Mustafa Ergen, Pravin Varaiya, Admission Control
  and Throughput Analysis in IEEE 802.11,
  ACM-Kluwer MONET Special Issue on WLAN
  Optimization at the MAC and Network Levels.
• Mustafa Ergen, Sinem Coleri, Pravin Varaiya QoS
  Aware Adaptive Resource Allocation Techniques for
  Fair Scheduling in OFDMA Based Broadband Wireless
  Access Systems, IEEE Transactions on
  Broadcasting, Vol.49 Dec. 2003
• Mustafa Ergen, Duke Lee, Ruchira Datta, Jeff Ko,
  Anuj Puri, Raja Sengupta, Pravin Varaiya,
  Comparison of Wireless Token Ring Protocol with
  IEEE 802.11, Journal of Internet Technology,
  Vol. 4 No. 4.
• Sinem Coleri, Mustafa Ergen, Anuj Puri, Ahmad
  Bahai, Channel Estimation Techniques Based on
  Pilot Arrangement in OFDM Systems, IEEE
  Transactions on Broadcasting VOL. 48, NO. 3
  September 2002, pp 223-229.
• Xuanming Dong, Mustafa Ergen, Pravin Varaiya,
  Anuj Puri Improving the Aggregate Throughput of
  Access Points in IEEE 802.11 Wireless LANs, IEEE
  WLN, Bonn, Germany, October, 2003.
• Mustafa Ergen, Duke Lee, Raja Sengupta, Pravin
  Varaiya Wireless Token Ring Protocol-performance
  comparison with IEEE 802.11, IEEE ISCC, Antalya,
  Turkey, July 2003. Received Best Student
  Paper Award

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Outline

• Introduction to IEEE 802.11
• 4 Markov models of DCF
• Throughput Analysis
• Different data rates
• Unsaturated Traffic
• Application Admission Control
• Application Indoor Throughput
• Next Generation WLANs
• Adaptive Antenna
• Multi-hop Networking
• Positioning
• Conclusion

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Contribution

• Joint Markov Model
• 802.11 Model
• Unsaturated Model
• Individual Throughput with Different Data Rates
• 802.11a Performance Analysis
• Admission Control
• Indoor Throughput

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Introduction to IEEE 802.11
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802.11 MAC Meta-States
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Idle Procedure
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Backoff Procedure
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VCS NAV Update Procedure
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Frame Sequence and Retry Procedure
(RTS CTS) is treated the same as (Data Ack)
with frame length lt aRTSThreshold
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IEEE 802.11 DCF
Time Scale of DCF Function
Saturation Throughput

• OPNET Simulation
• FHSS
• 1Mbps Channel
• Saturation Throughput
• Packet Size 1000bytes
• Inter-arrival time 0.005
• Load 1.6 Mbps

• Observation time
• Determination of discrete events
• Construction of Markov model
• Saturation throughput

RTS/CTS
w/o RTS/CTS
SIFS
SLOT
DIFS
EIFS
time
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4 Markov Models of DCF
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Joint Model
All stations are dependent
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Independent Model
Each station has its own independent channel, but
with same parameter p(n)
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Markov Model Analysis
Case I
Case II
Probability of Tx after/before Tx
CWmin16 CWmax1024
1/20
802.11
802.11b

• Assumption
• Saturation Throughput
• Limitless Retry
• Everybody hears everybody
• Case I No consecutive Transmission

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• t Probability of Transmission of a STA
• p Probability of Channel Busy
• n Number of Stations
• Ptr Probability of Transmission in Medium
• Ps Probability of Successful Transmission in
  Medium
• EP Packet Size
• Ts Duration of Successful Transmission
• Tc Duration of Collision
• s Duration of Slot Time
• S Throughput

Ptr Probability of Transmission Ps Probability
of Successful Transmission
from model
EP Packet Size Ts Duration of Successful
Transmission Tc Duration of Collision s
Duration of Slot Time
given by the PHY layer
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Independent Markov Model

• No freeze in backoff

• Definition
• b0a Probability of being in state 0a
• t Transmission occurs if STA is at 0a
• p Channel Busy if there is one station at 0a
  but me
• Ptr Transmission if there is at least one STA at
  0a
• Ps Successful Transmission if there is one STA
  at 0a

• Freeze in backoff

Assumption constant and independent collision
probability
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Joint Markov Model

• n2
• STA a and STA b
• states 4n
• Dependent STAs in 802.11
• Ptrp0a0bp0a1bp0a2bp0a3bp1a0bp2a0bp3a0b
  At least one Zero State
• Psp0a1bp0a2bp0a3bp1a0bp2a0bp3a0b Only
  one Zero State

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Throughput analysis
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One level backoff

• Independent of access mechanism
• Independent of PHY layer
• FHSS used
• 802.11 Joint Markov Model exactly
• approximates Simulation

OPNET Simulation Ptr ( Total ACK rcvd
Collision)/( Back-off slot Total ACK rcvd
Collision) Ps (Total ACK rcvd)/(Back-off slot
Total ACK rcvd Collision) Verification of
the simulation Simulation Time SLOT
Back-off slot Ts Total ACK rcvd Tc
Collision)
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Throughput
FHSS Data Rate 1Mbps Saturation Throughput
802.11 Joint Markov Model exactly
approximates Simulation
Verification of Duration Values from Simulation
Throughput Mbps
n
Ts0.0088sec Tc0.0088sec
for FHSS
TsTdataSIFSdTackDIFSd TcTdatadEIFS Tbs
TdataSIFSdTackDIFSdSLOT TbcTdatadDIFSSLO
T
Basic Access Mechanism
Ts0.0087sec Tc0.0007sec
TsTrtsSIFSdTctsSIFSdTdataSIFSdTackDIFS
d TcTrtsdEIFS TbsTrtsSIFSdTctsSIFSdTda
taSIFSdTackDIFSdSLOT TbcTdatadDIFSSLOT
RTS/CTS Access Mechanism
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Multi Level Back-off
802.11b

• FHSS
• Data Rate 1Mbps
• Saturation Throughput
• W16
• m7
• CWmin16
• CWmax1024
• Retry Count 255

802.11
Basic Ts0.0088s Tc0.0088s
RTS/CTS Ts0.0090s Tc0.0007s
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Different (Mixed) data rates
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Individual Throughput with Different Data Rates
N8 D4 1 2 3 4 5 6 7 8 Station ID
R1 R2 R1 R3 R4 R1 R4 R1 Data
Rates Ts1 Ts2 Ts1 Ts3 Ts4 Ts1 Ts4 Ts1 Succ.
Dur. Tc1 Tc2 Tc1 Tc3 Tc4 Tc1 Tc4 Tc1 Coll.
Dur. n14, n21, n31, n42

• Throughput distributes evenly among STAs
• ni is the number of stations with data rate i
• D is the total number of data rate choices
• ETs is Average
• ETc is highest of the STA in collision

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Verification in 802.11b
Simulation Scenario Start 5 Stations with 1
Mbps Data Rate Step 1 Station shift to 11
Mbps Stop 5 Stations with 11 Mbps Data Rate
Throughput of all stations is the same!
Throughput
Individual Throughput
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Unsaturated case
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New Model Unsaturated Traffic

• Modifications
• Operation in non-saturated load
• Different Data Rates,
• Modified in IEEE 802.11a

Traffic Intensity
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802.11a OFDM Packet Format
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Throughput with RTS/CTS DR54Mbps
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Analysis
Throughput with Different Data Rates not mixed
l0.1
Throughput with Offered Load DR54Mbps
Throughput with Constant total load l1/n
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Admission Control
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Throughput fixed station same SNR
Fairness Constraint
TimeN
TimeN
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Admission Control w/o Mobility
Total Throughput
Individual Throughput
Data Rates are fixed Without RTS/CTS l0.2 With
RTS/CTS gap will be smaller
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Admission Control w/o Mobility
Probability of being selected
Number of Stations selected at time t
Data Rate vs Throughput
Fairness Constraint
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Admission Control with Mobility
Total Throughput
Individual Throughput
Data Rates are changed in every iteration
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Admission Control with Mobility
Probability of being selected
Number of Stations Selected at time t
Data Rate vs Throughput
Fairness Constraint
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Indoor Throughput
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Indoor Throughput
Access Point Coverage Determination
Signal Power (RSSI Map)

• Access Point Coverage gives the number of
• Mobiles attached per AP

Signal Power gives the data rate of each mobile
Client model (power level 1-30mW) Omni-directional
antennas APs (power level 1-100mW) Model the
interference between the APs and the mobiles
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(No Transcript)
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Performance
Total Throughput 5 AP
Individual Throughput 5 AP
Throughput 50 STAs
Data Rate vs Throughput 5 AP
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Future work
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Intelligent Network

• Problems
• Coverage
• Throughput
• Security
• Interference
• Power Efficiency
• Applications
• WLAN
• Mesh Networks
• UWB

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Adaptive Antenna Infrastructure BSS Only AP
has AA, RTS/CTS/ACK omni directional

• Rate Adaptation Mechanism
• Decrement with timeout
• Increment with received ACK
• Power 1mW
• 10mW in direction
• (45o, 90o, 180o, 360o)
• 0.01mW out of direction

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Adaptive Antenna
Ad hoc All STAs have Adaptive Antenna
Infrastructure Only AP have Adaptive Antenna
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Multi Hop Networking Motivation

• The smaller the range the higher the throughput

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Multi Hop Networking Algorithm
Operation in PCF
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Positioning

• Outdoor
• GPS
• Cellular Networks
• Indoor
• WLAN
• UWB
• Motivation
• Location Aware Applications
• Wireless Security

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Hybrid Method for Positioning

• Hybrid Method
• Achieve the accuracy of fingerprinting with less
  data collection effort,
• Error bound,

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Conclusion

• Markov Model
• Independent Markov Model
• Joint Markov Model
• Different Data Rates
• (Un) Saturated Traffic
• Application Admission Control
• Application Indoor Throughput
• Next Generation WLANs
• Adaptive Antenna
• Multi-hop Networking
• Positioning

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Appendix

• 802.11a
• Slot 9
• SIFS 16
• PIFS 25
• DIFS 34
• EIFS 96

• 802.11
• Slot 50
• SIFS 28
• DIFS 128
• EIFS 384

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