Queueing Analysis for Access Points with Failures and Handoffs of Mobile Stations in Wireless Networ

1
Queueing Analysis for Access Points with Failures
and Handoffs of Mobile Stations in Wireless
Networks

• Chen Xinyu
• 2003-10-14

2
Outline

• Wireless network architecture
• System model and assumptions
• Five dispatch strategies
• Analytical results and comparisons
• Conclusions

3
Wireless Network Architecture
4
State Transition Diagram

• Three states for a mobile station
• State 0 Normal, State 1 Recovery, State 2
  Handoff

0
2
1
5
Stationary State Probability
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System Model and Assumptions

• Communications among all three components are by
  message-passing
• The message arrival process for each Mobile
  Station is with a constant rate ?
• The message dispatch requirement D is an
  exponentially distributed random with ?
• The Access Point itself does not undergo
  failures.

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Undispatchable Message

• Undispatchable message
• a message reaches the dispatch facility, however,
  its target mobile station is not in the normal
  state, i.e., in the recovery or handoff state

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Expected Sojourn Time

• Sojourn time
• the time period between that a message enters an
  Access Point and that the message leaves it
• Objective
• Derive the expected message sojourn time in an
  Access Point with different dispatch strategies
  in the presence of failures and handoffs of
  Mobile Stations.

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Dispatch Model (1)

• Basic Dispatch Model

n?
?
q0
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Message Sojourn Time (1)

• Conditioned message dispatch time

• Expected message sojourn time

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Dispatch Model (2)

• Static Processor-Sharing Dispatch Model

?
?
?
12
Message Sojourn Time (2)

• Conditioned message dispatch time

• Expected message sojourn time

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Dispatch Model (3)

• Dynamic Processor-Sharing Dispatch Model

?
?
?
q1
q2
qn
K
14
K Dispatchable Messages

• When a message enters the dispatch facility

15
Message Sojourn Time (3)

• Conditioned message dispatch time

• Expected message sojourn time

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Dispatch Model (4)

• Round-Robin Dispatch Model

?
?
?
q1
q2
qn
?
?
?

• No swap time

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Message Sojourn Time (4)

• Conditioned message dispatch time

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Dispatch Model (5)

• Feedback Dispatch Model

n?
?
q0
19
Possion Arrivals See Time Averages

• Possion Arrivals See Time Averages (PASTA)
• The probability of having M messages in the
  system at a random epoch is equal to the steady
  state probability of having M messages in the
  system at any random time

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Message Sojourn Time (5)
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Analytical Results and Comparisons (1)

• Number of mobile stations

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Analytical Results and Comparisons (2)

• Failure rate

23
Analytical Results and Comparisons (3)

• Message arrival rate

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Analytical Results and Comparisons (4)

• Expected message dispatch requirement

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Conclusions

• Analyze the message sojourn time within an Access
  Point in the presence of failures and handoffs of
  mobile stations in wireless networks
• Consider five dispatch strategies
• Obtain analytical results and comparisons