The use of wireless sensor networks to monitor and control the precise agriculture is one of the areas which received broad concern in recent times, for the services, facilities and the reliability provided by these networks on the monitoring and con
trol level.
This research contributes to the study of the application of this technique in greenhouses deployed over large areas in our country. It offers solutions for networks of monitoring and control, in real time, and ensures a good performance according to the essential evaluating criteria, such as reducing the time-delay, and increases throughput, increases the delivery ratio of packets, and reduces the number of packets lost along with increased network load.
In order to do that, a number of scenarios are proposed. These scenarios are similar to the reality of the construction and operation of the greenhouses in our region relying on ZigBee technique. Wireless sensors networks of these scenarios have been tested, using simulation in order to make conclusion and recommendations to guide the work while installing such networks in place to work as their best for different areas and a large number of lounges
Wireless Sensor Networks (WSN) have applications in many different areas of life, such as health care, environmental monitoring, and military and economic areas and in industrial automation and many other applications.
The development of these net
works and the improvement of their performance occupy an important place of interest in research centers and specialized scientific institutes. The interest in these structures as a way to improve the performance of these networks leads to good results in this area. The cluster structure is one of the most important structures that have received increasing attention over recent years.
This research suggested a modification of the structure of the cluster tree WSN dividing clusters into sub-groups, and each group of these sub-groups operates like a tree from a small amount of nodes. The results that have been obtained by means of simulation indicate a significant improvement in terms of reducing energy consumption and thus an increase in the lifetime of the network, as compared to traditional cluster tree WSN. But that was at the expense of slightly lower rates of transmission and delivery ratio in the nodes of these networks. This leads us to recommend using this method to build the networks used to monitor protected agriculture and other networks with low transmission rates.
The concept of frequency reuse has been successfully implemented in modern cellular communications systems in order to increase the system capacity. Further improvement of capacity can be achieved by employing adaptive arrays at the base station. In
order to track the desired users, direction finding algorithms are used to locate the positions of mobile users as they move within or between cells.
Recently, neural networks-based direction finding algorithms have been supposed for source direction finding. The performance of neural network is evaluated by comparing their prediction, standard deviation and Mean Square Error (MSE) between their predicted and measurement values. The research depends on this context. So, it has been compared the antenna array output signals according to their amplitude, then selected the signal that has the best amplitude in the system’s final output.
A common challenge in designing a wireless system is to overcome
the effects of the wireless channel, such as multi-path propagation,
and Inter-symbol Interference. and the ability of OFDM to combat
the effects of multi-path propagation made it th
e modulation of
choice for third and fourth generation networks.
In OFDM system we transmit data symbols on a large number of
subcarriers, and these data symbols exposed to changes in
amplitude and phase, caused of noise and frequency selective
fading and Doppler shift .
To get the transmitted data at the receiver we must cope with these
changes, so we need to know the channel response at every
subcarrier and every symbol, and for that reason we use PILOTS
and we use many methods to estimate the channel response depend
on pilots, and the most important channel is LMMSE Method.
We will discuss in these issue the wiener filtering method
(LMMSE) which give best performance but it is very complicated,
so we will use Discrete Fourier Transform (DFT) to reduce the
complexity of these method and we will study the BER and MSE in
both case when we use QPSK or 16QAM Modulation .
In this paper, A random modeling has been performed for
gyroscopes' components noise in unit measurements inertial
Crossbow IMU400CD MEMS by Alan Variance. Three random
components were discriminated in the noise sensors in addition to
the estimat
ed coefficients of these components, while the technical
bulletin did not mention but one component. Knowing the random
noise type gives the ability to use it as an output component of the
navigational system; estimating it with the navigation support
means such as GPS or magnetic compass or ... etc. enables to
correct gyroscopes out.
Inertial sensors Gyroscopes are gaining nowadays more and
more research interest in a variety of transport fields (i. e. land, sea
and air). Recent efforts are going towards developing those
traditional electromechanical models to electronic manufacturer
microenvironment technology called Micro Electro Mechanical
System (MEMS).
But in return MEMS gyroscopes suffer precision low when
compared to other types as a result of errors, many appear on the
output of particular random errors that can't be deleted
methodologies calibration known, so it is classified as a type of
noise or random processes where they are modeled using random
modeling techniques stochastic Modeling to identify and
distinguish types of noise in the sensor output. Among the most
famous of these techniques mode Allan Variance (AV).
The Quality of Service (QoS) term is refer to capability of network to prioritization and service distinguish for providing
better service to some service classes and call types.
Because of the lack of resources, from one side, and user's mobility
from the other, provision of QoS guarantees is considered at the head of the challenges that wireless cellular mobile network systems face.
Call Admission Control (CAC) is used for providing and achieving QoS guarantees in wireless systems.
This paper proposes a new CAC algorithm with priority index for providing and achieving QoS guarantees on the call level in
wireless systems in terms of new call blocking probabilities using multiple thresholds to determinate the number of acceptable new calls of each type of service.
Results of simulation provided in this paper show that the application of proposed new CAC algorithm with priority index on
the New Call Bounding Scheme (NCBS) provides a new CAC scheme which has better performance in terms of new call blocking
Probabilities and guarantees any desired level of QoS for new call types with the keeping priority of handoff calls.
Research over the past years has focused on electromagnetic waves and meta-materials. These structures are designed to give electromagnetic properties that cannot be produced by traditional, well known natural structures. Meta-materials obtain their
electromagnetic properties from their structures, not from their components. Meta-materials have new properties that define different mechanisms for electromagnetic wave propagation. These materials have been studied theoretically and have been used in many applications, especially microwaves and photonic fields. This research depends on these kinds of material, explains them, and analyzes the electromagnetic properties that yield from putting columns from these slabs with negative permittivity and permeability coefficient (MMs) in a fractal distribution of a natural medium. This research also compares the resulting properties with the electromagnetic properties that yield natural materials distributed the same way. We use the HFSS simulator which depends on the finite element method for calculating transmission and reflection coefficient for these structures.
The normal Costas frequencies code sequence signal is very well known and important signal in pulse compression Radar. In this paper we present two algorithms to modify Costas sequence by arranging the frequencies of Costas signal in time, first usin
g
binary Costas array and second using Golomb Ruler. These methods enable us to control side-lobes and to improve Doppler frequency resolution of Ambiguity Function (AF).
At first we present the principle of these methods Golomb Ruler and Costas array.
Then we apply these two methods to normal Costas signal, modified Costas signal and step frequency modulation and calculate the AF for all.
The results of comparison have shown that considerable reduction of side-lobes of AF is achieved by using these two methods, and consequently an improvement of AF is obtained.
Rice fading channel simulator is designed by
using two methods, method of Equal Areas (MEA) and method of
Exact Doppler Spread (MEDS). A new procedure for computation
of the parameters of the deterministic simulation model is
presented. This meth
od is named as combination of MEA and
MEDS.
Comparisons between autocorrelation functions of both reference
and simulation models are introduced for different procedures. It is
demonstrated by several simulation results that statistical properties
of simulation and reference models will be more closer according
to the new method than MEDS and MEA.
The advantage of peer-to-peer (P2P) paradigm relies on two main concepts: cooperation among
users and resource sharing. There are many applications based on peer-to-peer paradigm, but
the most popular one is the file sharing. We can classify the fi
le sharing application into
centralized systems, (having a central server), and decentralized systems. Another classification
would be structured and unstructured systems, based on the way of managing the indexing
information. In this paper, we have implemented a centralized peer-to-peer application for file
sharing. Then we evaluated the performance of the system by means of simulation.
