View
215
Download
0
Tags:
Embed Size (px)
Citation preview
Queueing Analysis for Access Points with Failures and Handoffs of
Mobile Stations in Wireless Networks
Chen Xinyu and Michael R. Lyu
The Chinese Univ. of Hong Kong
2004-03-08
Big Sky, MT
CUHK 2
Outline
Wireless network architecture
System model and assumptions
Five dispatch strategies
Analytical results and comparisons
Conclusions
CUHK 3
Cell
Wireless Network Architecture
Access Point Mobile Station Static Host
Radio LinkWired Link
Handoff: a mechanism for a Mobile Station to seamlessly
change a connection from one Access Point to another
CUHK 4
State Transition Diagram
Three states for a mobile station State 0 – Normal, State 1 – Recovery, State 2 – Handoff
0
2 1
R: Recovery time H: Handoff time
CUHK 5
Stationary State Probability
CUHK 6
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 variable with rate
The Access Point itself does not undergo failures
CUHK 7
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
CUHK 8
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.
CUHK 9
Dispatch Model (1)
Basic Dispatch Model
n
q0
CUHK 10
Message Sojourn Time (1)
Conditioned message dispatch time
Expected message sojourn time
CUHK 11
Dispatch Model (2)
Static Processor-Sharing Dispatch Model
/n
q1
/n
q2
/n
qn
CUHK 12
Message Sojourn Time (2)
Conditioned message dispatch time
Expected message sojourn time
CUHK 13
Dispatch Model (3)
Dynamic Processor-Sharing Dispatch Model
q1 q2 qn
/K /K /K K
CUHK 14
K Dispatchable Messages
When a message enters the dispatch facility
CUHK 15
Message Sojourn Time (3)
Conditioned message dispatch time
Expected message sojourn time
CUHK 16
Dispatch Model (4)
Round-Robin Dispatch Model
q1 q2 qn
No swap time
CUHK 17
Message Sojourn Time (4)
Conditioned message dispatch time
CUHK 18
Dispatch Model (5)
Feedback Dispatch Model
n
q0
CUHK 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
CUHK 20
Message Sojourn Time (5)
CUHK 21
Analytical Results and Comparisons (1)
Number of mobile stations
CUHK 22
Analytical Results and Comparisons (2)
Failure rate
CUHK 23
Analytical Results and Comparisons (3)
Message arrival rate
CUHK 24
Analytical Results and Comparisons (4)
Expected message dispatch requirement
CUHK 25
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