About Celeven Ho
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2009.3.17
From past two months, I am learning QT for one game which is running on multi-touch screen.
This is a summary during my work.
LookupPage is a powerful marketing tool which helps users to enhance their web presence and increase online visibility.
NS2 Learning Summary
Preface
Ns2 Install
Classifier
NAM
Data Transfer
How to enhance the multi-channel
Future
Preface
This handbook is our own learning experience summarize on Ns2.
It includes the collections of all the puzzles during our work. During these days, I found ns2 is a very useful tool to simulate all kinds of network. It’s a very happy and interesting journey when using Ns2.
There may be something unclear or faults. Please figure the out.
Thanks to my team.
Ns2 Install
Problem Collection:
Error: ns: fatal: libotcl.so: open failed: No such file or directory
Solution:
This file is in this directory:
1. A simple solution is to delete libotcl.so in ~ns/otcl and make ns again. ns will be linked with libotcl.a staticly and need nolibotcl.so at runtime.
2. Make sure install otcl, when we run “configure”, “—disable-static” option is needed.
NS2 Energy Model
In ../tcl/lib/ns-default.tcl
# Initialize the SharedMedia interface with parameters to make
# it work like the 914MHz Lucent WaveLAN DSSS radio interface
Phy/WirelessPhy set CPThresh_ 10.0
Phy/WirelessPhy set CSThresh_ 1.559e-11 ;#550m
Phy/WirelessPhy set RXThresh_ 3.652e-10 ;#250m
Phy/WirelessPhy set bandwidth_ 2e6 ;#2Mbps
Phy/WirelessPhy set Pt_ 0.28183815 ;#transmission power
Phy/WirelessPhy set freq_ 914e+6
Phy/WirelessPhy set L_ 1.0
default: Carrier Sense Multiple Access with Collision Detection is 50m?Wireless rang is 250m?bandwidth:2Mbps
RXThresh
7.214e-4 100m
8.5872e-4 40m
You can calculate the rang by the program.
threshold
complier threshold.cc $ cd ns-2.29/indep-utils/propagation/ $ g++ -lm threshold.cc -o threshold first
example:
$ threshold -m TwoRayGround 250 distance = 250 propagation model: TwoRayGround
Three kinds of energy model:
Free space model
The free space propagation model assumes the ideal propagation condition that there is only one clear line-of-sight path between the transmitter and receiver
Pt is the transmitted signal power. Gt and Gr are the antenna gains of the transmitter and the receiver respectively.L(L ≥ 1) is the system loss, and _ is the wavelength. It is common to select Gt = Gr = 1 and L = 1 in ns simulations.The free space model basically represents the communication range as a circle around the transmitter. If a receiver is within the circle, it receives all packets. Otherwise, it loses all packetsall
That’s to say, I draw a picture to understand this model.
Characteristics: No energy less in area
Symmetrical Energy
Ideal Model
Two-ray ground Model
The two-ray ground reflection model considers both the direct path and a ground reflection path.
I draw a picture to learn this model.
Characteristics: No energy less in area
Symmetrical Energy
Consideration of the ground reflection
The free space model and the two-ray model predict the received power as a deterministic function of distance. They both represent the communication range as an ideal circle. In reality, the received power at certain distance is a random variable due to multipath propagation effects, which is also known as fading effects. In fact, the above two models predicts the mean received power at distance d. A more general and widely-used model is called the shadowing model.
I draw a picture to learn to this model.
Characteristics: Energy less with the distance
Dissymmetrical Energy
Consideration of the ground reflection
More close to reality
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