How to Implement H & off Management in NS2

To implement the Handoff (H) and Offloading (Off) Management in ns2, it is used for mobile nodes which are vital for replicating mobility in wireless networks like cellular networks or Mobile Ad-Hoc Networks (MANETs). H encompasses transmitting a mobile node’s connection from one base station or access points to other when the node travels. Off refers to offloading traffic from a cellular network (like LTE) to a less jammed network (like Wi-Fi).

Here’s the technique to implement handoff management and offloading management in NS2:

Steps to Implement Handoff (H) and Offloading (Off) Management:

  1. Handoff Management: Replicate mobile nodes travelling amongst base stations or access points and transitioning their network connections (handoff) depends on their location.
  2. Offloading Management: Replicate the offloading of traffic from a cellular network (like LTE) to a Wi-Fi network in terms of conditions like load or signal strength.
  1. Handoff (H) Management in NS2

Handoff management grants mobile nodes to swap amongst various access points or base stations when move. For instance, a mobile node linked to Base Station 1 will need to connect to Base Station 2 as it moves out of range of the first base station.

Example: Handoff Between Base Stations in NS2

Step 1: Set up Base Stations imitate two base stations (or access points) and mobile nodes that travel amongst them.

# Create an NS2 simulator instance

set ns [new Simulator]

# Open trace and NAM files for logging

set tracefile [open “handoff_management.tr” w]

set namfile [open “handoff_management.nam” w]

$ns trace-all $tracefile

$ns namtrace-all-wireless $namfile 1000 1000

# Define wireless channel and network parameters

set chan_1_ [new Channel/WirelessChannel]

set topo [new Topography]

$topo load_flatgrid 1000 1000

set prop [new Propagation/TwoRayGround]

set netif [new Phy/WirelessPhy]

set mac [new Mac/802_11]

set ll [new LL]

set ifq [new Queue/DropTail/PriQueue]

set ant [new Antenna/OmniAntenna]

# Configure mobile nodes

$ns node-config -adhocRouting AODV \

-llType $ll \

-macType $mac \

-ifqType $ifq \

-ifqLen 50 \

-antType $ant \

-propType $prop \

-phyType $netif \

-channel $chan_1_ \

-topoInstance $topo

Step 2: Define Base Stations and Mobile Nodes

Design two base stations and a mobile node that dispatches between them. Handoff will happen as the node travels out of the range of the first base station and into the range of the second.

# Define two base stations (static nodes)

set bs1 [$ns node]

set bs2 [$ns node]

# Position base stations (bs1 at (100, 100) and bs2 at (900, 900))

$bs1 set X_ 100

$bs1 set Y_ 100

$bs2 set X_ 900

$bs2 set Y_ 900

# Create a mobile node (IoT device or phone) that moves between the two base stations

set mobile_node [$ns node]

# Set the initial position of the mobile node near bs1

$mobile_node set X_ 150

$mobile_node set Y_ 150

$mobile_node set Z_ 0

# Move the mobile node towards bs2, simulating handoff

$mobile_node setdest 850 850 20   ;# Move towards bs2 at 20 m/s

Step 3: Implement Handoff Trigger

Handoff happens when the mobile node moves out of the range of bs1 and into the range of bs2. You can execute a basic handoff according to the distance or signal strength, yet for simplicity, we’ll assume the handoff happens when the node is halfway amidst the two base stations.

# Define a procedure to trigger handoff based on node position

proc check_handoff {node bs1 bs2} {

global ns

# Get node position

set x [$node set X_]

set y [$node set Y_]

# Calculate the distance between the mobile node and the base stations

set dist_bs1 [expr sqrt(($x – 100) * ($x – 100) + ($y – 100) * ($y – 100))]

set dist_bs2 [expr sqrt(($x – 900) * ($x – 900) + ($y – 900) * ($y – 900))]

# If the node is closer to bs2, trigger handoff

if {$dist_bs2 < $dist_bs1} {

puts “Handoff: Mobile node switching to bs2 at time [$ns now]”

$ns at 1.0 “handoff_to_bs2 $node $bs2”

} else {

$ns at 1.0 “check_handoff $node $bs1 $bs2”

}

}

# Define a handoff procedure

proc handoff_to_bs2 {node bs2} {

# Attach the mobile node to bs2

$node setdest 900 900 0   ;# Simulate handoff by moving to bs2’s area

}

# Start checking for handoff after the node starts moving

$ns at 2.0 “check_handoff $mobile_node $bs1 $bs2”

Step 4: Run the Simulation

Set the simulation duration and execute it.

# Set the simulation end time

$ns at 30.0 “finish”

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exit 0

}

# Run the simulation

$ns run

  1. Offloading (Off) Management in NS2

Offloading management comprises exchanging traffic from a cellular network (e.g., LTE) to a Wi-Fi network to minimize blockage and improve efficiency. We can mimic this in NS2 by stating two networks (such as., LTE and Wi-Fi) and offloading traffic amongst them based on network conditions.

Example: Traffic Offloading from Cellular (LTE) to Wi-Fi

Step 1: Create Two Networks (LTE and Wi-Fi)

Simulate two various access networks (like LTE and Wi-Fi). Devices can offload their traffic to the Wi-Fi network when particular conditions are satisfied (e.g., blockage in the LTE network).

# Define two base stations: LTE and Wi-Fi

set lte_bs [$ns node]

set wifi_bs [$ns node]

# Position the LTE and Wi-Fi base stations

$lte_bs set X_ 500

$lte_bs set Y_ 500

$wifi_bs set X_ 700

$wifi_bs set Y_ 700

Step 2: Define Mobile Node and Offloading Traffic

Develop a mobile node that shifts its traffic from the LTE base station to the Wi-Fi base station when a certain condition is met (e.g., when it travels inside range of the Wi-Fi access point).

# Define mobile node

set mobile_node [$ns node]

# Attach UDP agent for traffic on LTE network

set udp_lte [new Agent/UDP]

set null_lte [new Agent/Null]

$ns attach-agent $mobile_node $udp_lte

$ns attach-agent $lte_bs $null_lte

$ns connect $udp_lte $null_lte

# Create CBR traffic on LTE network

set cbr_lte [new Application/Traffic/CBR]

$cbr_lte attach-agent $udp_lte

$cbr_lte set packetSize_ 512

$cbr_lte set rate_ 100Kb

# Attach UDP agent for traffic on Wi-Fi network

set udp_wifi [new Agent/UDP]

set null_wifi [new Agent/Null]

$ns attach-agent $mobile_node $udp_wifi

$ns attach-agent $wifi_bs $null_wifi

$ns connect $udp_wifi $null_wifi

# Create CBR traffic on Wi-Fi network (used for offloading)

set cbr_wifi [new Application/Traffic/CBR]

$cbr_wifi attach-agent $udp_wifi

$cbr_wifi set packetSize_ 512

$cbr_wifi set rate_ 200Kb

Step 3: Implement Offloading Trigger

Offloading happens when the mobile node travels into range of the Wi-Fi base station, permitting it to swap its traffic from LTE to Wi-Fi.

# Offloading based on node position (closer to Wi-Fi network)

proc check_offloading {node lte_bs wifi_bs} {

global ns

# Get node position

set x [$node set X_]

set y [$node set Y_]

# Calculate distance to Wi-Fi BS

set dist_wifi [expr sqrt(($x – 700) * ($x – 700) + ($y – 700) * ($y – 700))]

# If the node is close to Wi-Fi, offload traffic

if {$dist_wifi < 100} {

puts “Offloading traffic to Wi-Fi at time [$ns now]”

$ns at 1.0 “offload_to_wifi $node”

} else {

$ns at 1.0 “check_offloading $node $lte_bs $wifi_bs”

}

}

# Offload procedure

proc offload_to_wifi {node} {

puts “Traffic is now handled by Wi-Fi”

}

# Start checking for offloading at the beginning of the simulation

$ns at 2.0 “check_offloading $mobile_node $lte_bs $wifi_bs”

Step 4: Run the Simulation

# Set the simulation end time

$ns at 30.0 “finish”

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exit 0

}

# Run the simulation

$ns run

The above manual have aggregated the valuable information including snippet codes about how to simulate the characteristics of the Handoff (H) Management and Offloading (Off) Management to establish it in the ns2 environment for the wireless networks.

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