Simulation of Resources
allocations for heterogeneous IP
networks
Tutor : Dr. Yehuda Ben-shimol
Presented by : Sharon Sason
Ayelet Eshel
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Projects
motivation
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LSRT – large scale rural telephony
The Challenge:
Delivering the power of
telecommunication to the
remote regions of the globe.
Providing access to reliable
,low cost telephone and
data services.
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The Answer – heterogenic Network
The Topology (star
VSAT- very small
aperture terminal
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HUB-Composed of a
very large -15 to 36configuration)
foot (4,5 -11m)antenna. The HUB
controls and manages
the network.
Multiple access to the satellite
network
• Uplink – The Bandwidth allocated for the access
from the VSATs to the HUB.
• Downlink – The Bandwidth allocated for the access
from the HUB to the VSATs.
• Multiple VSATs compete on the uplink resource
while only the HUB use the downlink , so the
multiple access problem refers only to the uplink.
• The solution must take under consideration the
special characteristics of the satellite network.
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Satellite network special characteristics
• Delay – Long distances creates
large delay (270 msec).
• Packet loss – heavy packet loss due to atmospheric
conditions.
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Solution :
FTDMA protocol
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FTDMA – Frequency and Time
Division Multiple Access.
Frequency
This protocol is a
Combination of
FDMA and
TDMA ,in order
To Reduce
collisions.
Time
Time
slot 1
Channel
0
Channel
1
Channel
2
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Time
slot 2
Time
slot 3
FTDMA – RA/DA
Two operation modes implement the protocol.
1) RA – Random Access : a station randomly selects a
frequency channel, and transmit in the beginning of a
time slot (slotted aloha). There is a low probability
for collisions.
2) DA - Dedicated Access : a station receives specific
allocations of time and frequency channel , and
transmit accordingly. The probability for collisions is
zero.
•There
are separated frequency zones for RA and for DA
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Real time/Non real time - applications
• Non real time applications (http/FTP/email) - will
be sent in RA mode.
• Real time applications (voice/video) – requests for
time and frequency allocations will be sent in RA.
When the request is granted the session will
continue in DA mode using the allocated resources.
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FTDMA – for real time applications
1. VSAT sends request to the HUB in
RA mode.
2. HUB - responds by allocating
resources and send them
to the VSAT.
3. The source sends data
to the destination in DA
mode.
HUB
4. VSAT sends a close session signal to the HUB
which release resources.
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Implementation
Tool
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OPNET
network technology development environment
• Hierarchical Network
Modeling
• Object-oriented Modeling
• Finite State Machine
Modeling
• Highly Efficient Simulation
Engine
• Comprehensive Model
Library
• Integrated Analysis,
Animation,
and Debugging Tools
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OPNET
Main Editors
Network
Editor
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Process
Editor
Node
Editor
Our Model
Indoor
outdoo
r
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HUB
Indoor/outdoor node model
Indoor
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Outdoor
Our Outdoor Mac Layer – Process model
Transmit the
packets of this
session in DA
Waiting for
mode (every
something to
Receiving the
begging of its
first packet of time slot happen
the session,
schedule an Receive allocation
event for
packet from the
allocation
physical layer of
request
the satellite
network and
register the
Sending request
session as DA
to the hub in RA
with the given
mode
allocations
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Outdoor – Real time sessions management
Time
DA
Frequency's
Time
slot 1
IP source
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Channel
0
Channel
1
Channel
2
IP destination
IP source
IP destination
Time
slot 2
Time
slot 3
HUB – allocation table
Time
DA
Frequency's
Time slot 0 Time slot 1 Time slot 2
Outdoor 0
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Channel 0
Session 1
Session 2
Channel 1
Session 6
2
Session 4
Channel 2
Session 5
Session 3
Outdoor 1
Session 7
Outdoor 2
Next Stage …
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Analyses
Collecting network
performance statistics
and analyzing the results
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The END
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