How to Implement Network Channel Scheduling in NS2
To implement the Network Channel Scheduling within NS2, we will require to replicate on how several network channels are allocated to the nodes or flows actively, depends on the particular scheduling algorithms. This scheduling can be applied to enhance the resource allocation, increase throughput, and minimise delays in wireless or wired networks. Given below is a stages to execute the network channel scheduling in NS2:
Step-by-Step Implementation:
- Define Network Topology
Initially, describe the nodes, links, and channels are in the simulation. For wireless networks, each node can access to numerous channels, and the scheduling mechanism will decide in which the channel a node will utilize for transmission.
# Create NS2 Simulator instance
set ns [new Simulator]
# Create nodes
set n1 [$ns node]
set n2 [$ns node]
- Set Up Multiple Channels
To replicate the various channels in NS2, we want to describe the channel characteristics and allocate them to nodes. For wireless networks, the below code configures numerous wireless channels.
set channels [list Channel/Wireless Channel/Wired]
# Assign a channel to each link or wireless interface
$ns node-config -channelType Channel/Wireless ;# Assign Wireless channel
- Implement Channel Scheduling Algorithms
There are several channel scheduling algorithms that we can implement, like:
- Round Robin Scheduling
- Priority-based Scheduling
- Weighted Fair Queueing (WFQ)
- Proportional Fair Scheduling
Below is how we can execute the Round Robin Scheduling as an instance:
- a) Round Robin Scheduling
In this method, each flow or node attains access to a channel in turn, dispensing bandwidth equally between all.
set current_channel 0
proc round_robin_schedule {node_id} {
global channels current_channel
set num_channels [llength $channels]
set selected_channel [lindex $channels $current_channel]
# Assign the selected channel to the node
puts “Node $node_id is assigned to channel $selected_channel”
# Update the current channel for the next node
set current_channel [expr ($current_channel + 1) % $num_channels]
return $selected_channel
}
The function round_robin_schedule iterates via obtainable channels and allocates them in turn to each node. The present channel pointer is incremented for the next node, after a node is allocated a channel.
- b) Priority-based Scheduling
If we require to provide priority to the particular nodes or flows depending on specific criteria (like bandwidth needs, QoS), we can execute a priority-based scheduling mechanism.
set priorities [list 1 2 3] ;# Define priority level
proc priority_schedule {node_id priority} {
global channels
# Higher priority nodes get preferred channels
if { $priority == 1 } {
set selected_channel [lindex $channels 0]
} elseif { $priority == 2 } {
set selected_channel [lindex $channels 1]
} else {
set selected_channel [lindex $channels 2]
}
puts “Node $node_id with priority $priority is assigned to channel $selected_channel”
return $selected_channel
}
In this code, the nodes with higher priority are assigned better channels.
- Simulate Packet Flow and Scheduling
To replicate the packet flow and scheduling by routing the packets via the network and applying the scheduling algorithm for channel selection, after defining the scheduling algorithm.
# Simulate traffic from n1 to n2
set udp [new Agent/UDP]
$ns attach-agent $n1 $udp
set null [new Agent/Null]
$ns attach-agent $n2 $null
$ns connect $udp $null
# Schedule channel dynamically for n1 and n2
set channel_n1 [round_robin_schedule 1]
set channel_n2 [round_robin_schedule 2]
# Start transmission
set cbr [new Application/Traffic/CBR]
$cbr set packetSize_ 1000
$cbr set interval_ 0.1
$cbr attach-agent $udp
$ns at 1.0 “$cbr start”
Now, the UDP agent and the CBR (Constant Bit Rate) traffic generator are utilized to replicate traffic flow among the nodes n1 and n2, and the Round Robin scheduling assigns channels actively.
- Trace and Analyze Scheduling
We can use the NS2’s built-in tracing mechanism to log scheduling decisions and traffic patterns for future analysis.
# Open a trace file
set tracefile [open “channel_schedule.tr” w]
$ns trace-all $tracefile
# Log the channel assignments
proc log_schedule {node_id channel} {
global tracefile
puts $tracefile “Node $node_id is using channel $channel at time [$ns now]”
}
log_schedule 1 $channel_n1
log_schedule 2 $channel_n2
- Run the Simulation
When the topology, scheduling algorithm, traffic flow, and tracing are configure then run the simulation:
# Start the simulation
$ns at 10.0 “finish”
proc finish {} {
global ns tracefile
$ns flush-trace
close $tracefile
exec nam out.nam &
exit 0
}
$ns run
This will begin the simulation and record these channel assignments and also traffic flow to the trace file for later investigation.
- Performance Evaluation
To estimate the performance of the scheduling algorithm using NS2’s trace file or envision the outcomes using xgraph or MATLAB, after running the simulation. Metrics to estimate contain:
- Channel utilization
- Packet delivery ratio
- Latency
- Fairness among flows
- Advanced Channel Scheduling Algorithms
Based on the requirements of the network, we can be executed more difficult scheduling algorithms such as:
- Weighted Fair Queueing (WFQ): Ever single node or flow is allocated a weight, and the channel is scheduled rely on this weight to make sure fair bandwidth allocation.
- Proportional Fair Scheduling: Channels are assigned to increase the overall throughput when maintaining fairness between the nodes.
Example of Weighted Fair Queueing (WFQ):
set weights [list 0.5 1.0 1.5] ;# Define weights for each node
proc wfq_schedule {node_id} {
global channels weights
set weight [lindex $weights $node_id]
set selected_channel [lindex $channels [expr int(rand()*[llength $channels])]]
puts “Node $node_id with weight $weight is assigned to channel $selected_channel”
return $selected_channel
}
We instructed you on how to execute and examine the Network Channel Scheduling with the help of given method in the NS2 environment. We plan to offer more details on this concept through the appropriate simulation tools.
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