Network Simulator 3 aims at developing the software environment to build up the library first and then the user program. It is open-source software. Along with connecting sources to sinks by uniform mechanism, this network traces the system built under the concepts of tracing sinks and tracing sources.  Network Simulator Schedule NS3  is a new topic which talks about the experiment settings of the network and its uses. To make research, this topic will help greatly. There are more topics to be explored in upcoming pages. Our Experts have done in-depth research to make it easier.

Detailed Study of Simulator Schedule NS3

           To make scheduling as simple, the Simulator Application Programming Interface (API) is used. API is designed to make two applications communicate with each other. It is intermediary software. There are different types in scheduling methods,

Types of Schedule Methods

• ScheduleNow methods
  • The current simulation time is scheduled for the event, before the simulation time is converted for the next event, they will execute the current event after finished.
• Schedule Methods
  • There is a delay between the expiration date of the target event and the current simulation, to provide the scheduled event in the future.

Scheduling of Simulation Events

           To control the Scheduling of simulation events, the class ns3::Simulator is used. There is a simulation clock internally, maintained as a 64-bit integer. It is specified by the user through the Time::SetResolution function. 

Than the user-specified accuracy, it is impossible to specify the expiration time of the event. Events accuracy is scheduled in First in, First out order where the expiration time of the event is the same modulo. The first expiring one in the scheduled queue is the first inserted event.

           The member function, ns3::Simulator::Schedule, is performed by the scheduling process of the below parameters and as an Id for the scheduled event, it returns the value.

• Obj – the member method is invoked by this object.
• a1 –   to pass to the invoked method, this is the first argument.
• a2 –  to pass to the invoked method, this is the second argument.
• Time – The relative expiration time of the event.
• mem_ptr – to invoke member method pointer.

An event is scheduled to perform the expiration at destroy time, the process used is The member function, ns3:: Simulator::ScheduleDestroy. The events that are scheduled to expire at the “Destroy” time are Scheduled by the method of First in, First out. All normal events have expired when the parameters are applied on the Simulator::Destroy.

• obj – the object on which to invoke the method.
• mem_ptr – to invoke member method pointer.
• a1 –  to pass to the invoked method, this is the first argument.
• a2 – to pass to the invoked method, this is the second argument.
• a3 – to pass to the invoked method, this is the third argument.
• a4 – to pass to the invoked method, this is the fourth argument.
• a5 – to pass to the invoked method, this is the fifth argument.
• ns3::Simulator::ScheduleWithContext, member function used to perform the context-based process. It can be called from any thread because this method is thread-safe, based on the parameter.
• Context –  context parameter is user-specified.
• time – the relative expiration time of the event.
• obj –   the object on which to invoke the method.
• mem_ptr – to invoke member method pointer.
• a1 –   to pass to the invoked method, this is the first argument.
• a2 – to pass to the invoked method, this is the second argument.
• a3 – to pass to the invoked method, this is the third argument.

To change out the different implementations, the Simulator Schedule NS3  provides a mechanism, member function, ns3::Simulator::SetImplementation. 

For instance, a single-threaded Simulator performs no synchronization of real-time, this is the default implementation.

A new simulator implementation can be substituted to call this method, it can synchronize events to a real-time clock and multi-threaded. By the ns3:: Simulator::SetScheduler, member function, at any time, the scheduler can set the event. Before we start using, events in the previous scheduler will be transmitted to New Simulator Scheduler NS3.

The method ns3::Simulator::Stop invokes an event, it will be the final event scheduled by the Simulator::run method before coming back to the caller.

Packet Scheduling Algorithm in NS3

1. Priority Set Scheduler (PSS)

Priority Set Scheduler is Quality of Service Scheduler which combines Frequency Domain (FD) and Time-Domain (TD) packet allocates one scheduler to scheduling operations. It controls the scheduling of events particularly Target Bit Rate (TBR).

• Channel and Quality of Service Aware (CAQ) Scheduler

The head of line delay (HOL), the guaranteed bit rate (GBR), and channel quality over different subbands is considered by the Long Term Evolution MAC, downlink Scheduling Algorithm, Channel, and Quality of Service Aware Scheduler. 

The Channel and Quality of Service Aware Scheduler are based on joining Frequency Domain and Time Domain. In the Channel and Quality of Service Aware Scheduler, the users are grouped by the priority in the Time Domain. The main aim of Grouping is to make Frequency Domain Scheduling to take care of the flows which come first with the highest Head of Line delay.

1. Round Robin Scheduler (RR)

The Round Robin Scheduler works by making division among the resources available in the active flows, that is, it divides by logical channels that have a non-empty Radio Link Control (RLC). 

If the number of active flows is lesser than the Resource Block Group (RBG), then all the flows are grouped in the same subframe. All the flows cannot be scheduled into the subframe when the Resource Block Group is lesser than the number of active flows; in the subframe, the allocation will begin from the last flow, one which was not allocated.

1. Proportional Fair (PF) Scheduler

The Proportional Fair Scheduling Algorithm gives a fair tradeoff between system throughput and proves by choosing the user with the highest instantaneous data rate relative to its average data rate. The scheduler complexity and overhead are increased by allotting the slot positions of radio resources informed, where the work is done by the Proportional Fair Scheduler in every block.

Simulation Parameters

   There are some particular parameters for simulation which are discussed below:

• Number of EnodeB – 1
• Simulation duration – 5s
• Radius – 60m
• Frame Structure – FDD
• UEs number – From 20 to 100
• Packet Interval – 1ms
• User speed – Constant velocity (10m/s)
• Bandwidth – 25 (DL transmission bandwidth in no. of RB)
• Quality of Services                
• GBR Conversational video
• GBR Conversational VoIP
  • VoIP codec – G.711
  • VoIP guaranteed bit rate – 12.2 kbps
• Video file – st_highway_cif (MPEG4)
  • Video guaranteed bit rate – 64 kbps
  • Pathloss Model – Cost231
  • Propagation Loss Model

Latest Intersting Research Topics

In Simulator Schedule ns3, our experts have designed some of the research topics; we hope this will provide more ideas for the selection of the topic.

• Collision and Energy based routing design for WSN with IoT networks 
• Classification and detection of network-based autonomous vehicles behaviors in C-V2X technology 
• Data Dissemination using a dynamic broadcast timer for SDN based VANET applications 
• Conflict flow classification and detection by Machine Learning for SDN 
• 5G Multi-RAT networks: Network Selection using Multi-criteria decision-making algorithms. 

Thus our article will be useful to gain more knowledge about Simulator Schedule NS3. There is numerous numbers of topics available to our experts. Experts are ready to give guidance and support for your research. So you can communicate with them.