The node scenario generation is done using the star.scn file. The Start topology model has the following parameters simulated
4.1.1 Simulation Parameters
Simulation is a flexible means for assessment of the performance offered by a telecommunication system. However, identifying the correct simulation parameters is key for a successful and nearly realistic analysis
of any study. The following discussion focuses on the task of identifying the correct parameters to generate a realistic network scenario, while explaining their meaning and their reason of choice (if any) in detail. General parameters for basic simulations are described here. However, the parameters that impact the network performance are discussed in the next chapter where we introduce the performance analysis of the system.
Traffic Parameters
Traffic Type
This project report is based on results simulated with a FTP application, based on the internet protocol, UDP (User Datagram Protocol). Its primary features are:
. Single Way Transmission (No Acknowledgements)
. Defined Packet size
. Defined Packet Interval
. Unreliable Data Transmission
FTP traffic with a TCP connection is done due to its advanced features like congestion control, requiring dynamic adjustment of the transmission rate based on the traffic conditions; it is hard to implement simplistic and power efficient devices, for menial applications.
Packet Size
The packet size is assumed be to 70bytes. This is exclusive of the RTR, MAC and PHY layer headers.
Traffic Direction
The traffic flows are all one way, with the communication directed to the coordinator. The study is being investigated with particular focus on low datarate wireless sensors communicating with a central node updating it with the application information.
Number of Nodes
The simulation is carried out with 7 active nodes. One of them being the coordinator.
Coordinators
Since a simple star network topology is being simulated, only a single coordinator is present.
Node Movement
The nodes remain stationary.
Node Position
The nodes are placed along an imaginary circle around the coordinator, with radius equal to the personal operating space of the nodes.
The trace and node parameters are summarized in the following table.
Figure 4.1 Star topology parameters
scen_gen
. Parameters: It accepts the following command line parameters
– scen_gen [number-of-nodes] [X-Pos-of-coord] [Y-Pos-of-coord] [Personal-Operating-Space]
Number-of-nodes: Number of nodes to be placed around the coordinator.
X-Pos-of-coord: X position of the coordinator, with respect to the area of the network dimensions.
Y-Pos-of-coord: Y position of the coordinator, with respect to the area of operation of the network.
Personal-Operating-Space: The operating space or the reachabilitiy of the coordinator. The nodes are required to be placed equidistantly around the coordinator, for the test scenarios in this report, within the operating space of the coordinator, this parameter is utilized to arrange the nodes along an imaginary circle drawn around the coordinator with this value
as radius.
Example: scen gen 11 25 25 10
. Functionality: This utility would automatically generate the coordinates of the nodes to place them around the coordinator, along an imaginary circle drawn with a radius equal to the Personal Operating Space. The node position file, holding the positions of all the nodes around the coordinator is generated from star.scn. Currently this file is being generated with the utility, scen gen. However, it is a simple text file, which can be easily edited to place the nodes at desired positions. Note that the positions of the nodes should respect the boundaries of the network mentioned in the source file, star.tcl
Working: Running the utility would create a file, star.scn, to be used by the source scenario file, star.tcl.
The scn file for star.tcl
$node_(0) set X_ 25
$node_(0) set Y_ 25
$node_(0) set Z_ 0
$node_(1) set X_ 20
$node_(1) set Y_ 16.34
$node_(1) set Z_ 0
$node_(2) set X_ 15
$node_(2) set Y_ 25
$node_(2) set Z_ 0
$node_(3) set X_ 20
$node_(3) set Y_ 33.66
$node_(3) set Z_ 0
$node_(4) set X_ 30
$node_(4) set Y_ 33.66
$node_(4) set Z_ 0
$node_(5) set X_ 35
$node_(5) set Y_ 25
$node_(5) set Z_ 0
$node_(6) set X_ 30
$node_(6) set Y_ 16.34
$node_(6) set Z_ 0
The resultant position file for the nodes would like some think like this:
Figure 4.1 Node arrangement
