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Effects of Location Awareness on Concurrent Transmissions for
Cognitive Ad Hoc Networks Overlaying Infrastructure-Based
Through wideband spectrum sensing, cognitive radio (CR) can identify
the opportunity of reusing the frequency spectrum of other wireless
systems. To save time and energy of wideband spectrum, we
investigate to what extent a CR system incorporating the location
awareness capability can establish a scanning-free region where a
peer-to-peer ad hoc network can overlay on an infrastructure-based
network. Based on the carrier sense multiple access with collision
avoidance (CSMA/CA) medium access control (MAC) protocol, the
concurrent transmission probability of a peer-to-peer connection and
an infrastructure-based connection is computed. It is shown that the
frequency band of the legacy system can be reused up to 45 percent
by the overlaying cognitive ad hoc network when CR users have the
location information of the primary and secondary users.
OBJECTIVE OF THE PROJECT
The existing things are consider the coexistence issue of the hybrid
infrastructure-based and overlaying ad hoc networks has been
addressed but in different scenarios. The idea of combining ad hoc link
and infrastructure based link was proposed mainly to extend the
coverage area of the infrastructure-based network. That is, the
coverage area of ad hoc networks is not overlapped with that of the
hoc/infrastructure-based network, which maintain the peer-to-peer
cognitive radio (CR) users are located within the coverage area of the
existing legacy wireless network. In this, to further improve the
throughput of a wireless local area network (WLAN), it was suggested
that an access point (AP) could dynamically switch between the
infrastructure mode and the ad hoc mode.
In this project, we are trying to provide the basic idea of utilizing
location awareness to facilitate frequency sharing in a concurrent
transmission manner. Specific achievements are summarized in the
We are going to show that a CR device having location
information of other nodes can concurrently transmit a peer-topeer data in the presence of an infrastructure based connection
in some region. We also dimension the concurrent transmission
(or the scanning-free) region for CR users. Nevertheless, the
wideband spectrum sensing procedure is still needed but is
initiated only when the CR user is outside the concurrent
transmission region. Therefore, the energy consumption of CR
systems with location awareness capability can be reduced
Based on the CSMA/CA MAC protocol, a physical/MAC cross-layer
analytical model is developed to compute the coexistence
probability of a peer-to-peer connection and an infrastructurebased connection. Based on this analytical model, we find that
concurrent transmission of the secondary CR users and the
primary users in the legacy system can significantly enhance the
total throughput over the pure legacy system.
All projects are feasible given unlimited resources and infinite
time. But the development of software is plagued by the scarcity of
resources and difficult delivery rates. It is both necessary and prudent
to evaluate the feasibility of a project at the earliest possible time.
Three key considerations are involved in the feasibility analysis.
This procedure is to determine the benefits and savings that are
expected from a candidate system and compare them with costs. If
benefits outweigh costs, then the decision is made to design and
implement the system.
Otherwise, further justification or alterations
in proposed system will have to be made if it is to have a chance of
being approved. This is an ongoing effort that improves in accuracy at
each phase of the system life cycle.
Technical feasibility centers on the existing computer system
(hardware, software, etc.,) and to what extent it can support the
proposed addition. If the budget is a serious constraint, then the
project is judged not feasible.
People are inherently resistant to change, and computers have been
known to facilitate change. It is understandable that the introduction
of a candidate system requires special effort to educate, sell, and train
the staff on new ways of conducting business.
ALGORITHM & EXPLANATION
The above figure is an illustrative example for the coexistence of two CR devices establishing a peer-topeer ad hoc link and a primary user connecting to the infrastructure-based network, where all the devices
(MS1, MS2, and MS3) use the same spectrum simultaneously.
The above figure illustrates a hybrid ad hoc/infrastructure-based
network consisting of two CR devices (MS1 and MS2) and a primary
user MS3. Assume that the secondary CR users MS1 and MS2 try to
make a peer-to-peer connection, and the n primary user MS3 has been
connected to the base station (BS) or AP of the legacy infrastructurebased system. In the figure, MS1, MS2, and MS3 are located at (r1,
θ1), (r2, θ2), and (r3, θ3), respectively; the coverage area of the BS
is πr2. All the primary and secondary users stay fixed or hardly move.
We assume that the CR devices can perform the positioning technique
to acquire their relative or absolute position by using GPS or detecting
the signal strength from the BSs of legacy systems. The location
information is broadcasted by using the geographical routing protocols.
Although both the positioning and geographical routing may waste
time and consume energy, they have no need to be processed for
every data transmission. They are only performed when a new node
joins or the node changes its position. Furthermore, with the help of
upper layers, the location information is already stored in the device.
Therefore, compared to the spectrum sensing at every transmission,
we believe that the additional energy consumption and memory space
due to the positioning and location update is relatively small.
Based on the CSMA/CA MAC protocol, multiple users contend the
channel, and only one mobile station within the coverage of the BS can
establish an infrastructure-based communication link at any instant. To
set up an extra peer to peer ad hoc connection in the same frequency
band of the primary user, the secondary users not only require
ensuring that the current infrastructure-based link quality cannot be
degraded but also has to win the contentions between other feasible
secondary users. Here, we consider that both primary and secondary
users have identical transmit power. It is reasonable to assume that
only one secondary user can establish a link after the contention at
one instance due to the similar interference range. Denote SIRi and
SIRa as the received signal-to-interference ratios (SIRs) of the
infrastructure-based and ad hoc links, respectively.
Then, we can define the coexistence (or concurrent transmission)
probability (PCT) of the infrastructure-based link and CR-based ad hoc
link in an overlapped area as follows:
Where zi and za are the required SIR thresholds for the infrastructurebased and ad hoc links, respectively. To obtain the concurrent
transmission region, it is crucial to calculate the coexistence probability
of both the infrastructure and ad hoc links. If the link quality of the
primary user cannot be guaranteed, CR devices have to sense and
change to other frequency bands.
We consider the two-ray ground reflection model in which there exist
two paths between the transmitter and receiver. One is the line-ofsight, and the other is reflected from ground. Thus, the received power
can be written as
Where Pr and Pt are the received and transmitted power levels at a
mobile station, respectively; hbs and hms represent the antenna heights
of the BS and the mobile station, respectively; Gbs and Gms stand for
the antenna gains of the BS and the mobile station, respectively; r is
the distance between the transmitter and receiver; α is the path loss
exponent; and 10ξ/10 is the logs normally distributed shadowing
In our project, we are going to create an environment as a base
station, some cognitive radios and some users. We are going to place
some video frames in the base station for simulating the concept
overlaying. Whenever, the user wants to retrieve a file with the carrier
frequency through cognitive radios. For each GUI window as consider
as a system. Also we will monitor the status of every cognitive radio.
# OPERATING SYSTEM
# CLOCK SPEED
# HARD DISK
# CACHE MEMORY
# OPERAING SYSEM
Cognitive device must be able to detect
very reliably whether it is far enough away from a primary
base station and/or whether this primary base station is
silent at a given point in time. For an individual detector
this is very difficult due to different radio propagation
paths and it may need to sense primary user signals
buried deep under the noise floor.
A cognitive radio transceiver is able to
adapt to the dynamic radio environment and the network
parameters to maximize the utilization of the limited radio
resources while providing flexibility in wireless access. In
this project, we show that a CR device having location
information of other nodes can concurrently transmit a
peer-to-peer data in the presence of an infrastructure
based connection in some region. We also dimension the
concurrent transmission (or the scanning-free) region for
CR users. Note that a concurrent transmission region of a
CR system is equivalent to a scanning-free region. A
Cognitive Radio is a radio that can change its transmitter
parameters based on interaction with the environment in
which it operates.
Users: The identity of the users of radios who wish to join
a network needs to be assured. In the CSMA/CA MAC
protocol, multiple users contend the channel, and only one
mobile station within the coverage of the BS can establish
an infrastructure-based communication link at any instant.
To set up an extra peer-to-peer ad hoc connection in the
same frequency band of the primary user, the secondary
infrastructure-based link quality cannot be degraded but
also has to win the contentions between other feasible
secondary users. Here, we consider that both primary and
secondary users have identical transmit power. It is
reasonable to assume that only one secondary user can
establish a link after the contention at one instance due to
the similar interference range.
Multimedia frames: Wireless multimedia applications
require significant bandwidth and often have to satisfy
relatively tight delay constraints. Radio spectrum is a
scarce resource. Limited available bandwidth is considered
one of the major bottlenecks for high-quality multimedia
wireless services. A reason for this is the fact that a major
portion of the spectrum has already been allocated. On the
other hand, actual measurements taken on the 0–6 GHz
band and other spectrum occupancy measurements on
licensed bands, such as TV bands, show the significant
under utilization of the spectrum. Since Cognitive Radio
can operate in different frequency bands which provides