Analytical Model ppt

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CS 4554 Network Modeling and Analysis
Project Summer 2000
DELAY / THROUGHPUT CHARACTERIZATION OF THE AD
HOC WIRELESS COMMUNICATIONS FOR SPECIAL
OPERATIONS FORCES(SOF)
Baybora Aksoy,Ltjg. Ilker Sahin,Ltjg.
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Presentation Plan

• System Description
• Goal of the Study
• Assumptions and Limitations
• System Parameters
• System Variables
• Analytical Model
• Delay Calculations
• Simulation with OPNET for Verification
• Comparisons and Conclusions

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System Description

• implementation of ad hoc wireless networking on
  battlefields
• designed to be used by the SOF twelve men-teams
  
• Team members need to be able to send messages
  to
• the other team members and the operation
  center
• Each member of the team is equipped with
  communication devices

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System Description

• These devices allow team members to communicate
  with each other
• The team leader has special communication
  device (Type-I)
• allows him to act as a relay station between
  the team members.
• this private device also allows a connection
  between the team
• and the operation center via satellites
• The team has a back up for this Type I device
  is called Type-II.

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System Architecture
Back up type-II
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Goal of the Study

• Develop an analytical model, which calculates
• the mean transfer delay of the system
• Verify the output of the analytical model with
  simulation.
• Use the Network Modeling and Analysis techniques
• that we learned during the class
• Be familiar to the network simulation tools,
• use OPNET simulation tool.

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Assumptions and Limitations

• System is implemented as a wireless star network.
• Each team member represents a node in star
  topology.
• Central node is the team commander who is also
  the
• gateway to the operation center.

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Assumptions and Limitations

• Transmission medium is air.
• The propagation velocity is the speed of voice
  (3E8 m/s)
• There is no interference in the medium.

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Assumptions and Limitations

• The distance from a node to the central node is
  constant
• and all the distances are the same.
• Power consumption is not modeled.
• There is no power consideration.
• There is 0.25 ms or less latency at each node.
• E-mail, HTTP, Voice and FTP services are
  supported
• in the system.
• This is a M/M/1 model
• Arrival rate of messages to each node and message
• length are represented with Poisson
  distribution.
• There is one server.

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Assumptions and Limitations

• Data rate is 2 Mbps.
• Since the distances between the nodes are small,
• the propagation delay caused by the transmission
  
• media, can be neglected.
• The main system is not analytically modeled.
• The communications are symmetric.
• The intensity of the communications depend on the
  
• mission at hand. It is assumed as a poisson
  distribution. 

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Parameters

• E(D) (The Mean Transfer Delay)
• Time interval between the instant the message is
  
• available at the sending station and the end of
  its
• successful reception at the receiving station
  
• E(W) (Waiting Delay)
• Time elapsed from the availability of a message
• in the source station transmit buffer until the
• beginning of its transmission on the channel
• E(S) (Service Time)
• Time elapsed between the arrival of the first
  bit of
• the message at the destination and the arrival
  of the last bit

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Parameters

• E(Tp) (Propagation Delay)
• Time elapsed from the beginning of the
  transmission
• of the message until the arrival of the first
  bit of the
• message at the destination  
• ? Arrival Rate (bps)
• N Number of nodes
• ? Utilization (bit)

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Parameters

• G Probability that a message from node i
• will have node j as its destination
• Lm Message Size (bit)
• L Distance from central node (m)
• Pv Propagation velocity (3 x 10 m/sec)

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Variables

• ? Arrival Rate (Poisson/Uniform)
• Lm Message Size (General)
• l Distance from central Node

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Analytical Model
Total delay is the sum of three delay
components E(D) E(W) E(S) E(Tp) The
service time is a function of the message size
Lm and channel capacity R E(S) E(Lm)/R
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Analytical Model
Propagation delay is a function of the distance
1 node-hub and the propagation velocity Pv for
the chosen medium (3 x 10 m/sec.)   E(Tp) (l /
Pv)
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Analytical Model
Each message arriving to the system is expected
to wait for E(W) y (? y ) / 2 (1-
?)   y 1 (N-2) ? G E(S)   y 2
1 2 (N-2) ? G (N-2) (N-3) ? G
E(S )   G 1/(N-1)   ? ? E(S) 
2
1
2
1
2
2
2
2
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Calculations
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