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Effects of Location Awareness on Concurrent Transmissions for

Cognitive Ad Hoc Networks Overlaying Infrastructure-Based

Systems

(Synopsis)

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ABSTRACT

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.

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OBJECTIVE OF THE PROJECT

EXISTING SYSTEM

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

infrastructure-based network. In the present hybrid ad

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.

PROPOSED SYSTEM

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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

following:

We are going to 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. 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

significantly.

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 infrastructure-

based 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.

INTRODUCTION

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FEASIBILITY STUDY

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.

Economic Feasibility :

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:

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.

Operational Feasibility :

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

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The above figure is an illustrative example for the coexistence of two CR devices establishing a peer-to-

peer 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 infrastructure-

based 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

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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 infrastructure-

based 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-of-

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sight, 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

component.

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.

Software Requirements:

# OPERATING SYSTEM : Windows XP

# TECHNOLOGY : J2SDK1.4.1 And

above

Hardware Requirements:

# PROCESSOR : Pentium III

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# CLOCK SPEED : 550 MHz

# HARD DISK : 20GB

# RAM : 128MB

# CACHE MEMORY : 512KB

# OPERAING SYSEM : Windows 2000

Professional

# MONITOR : Color Monitor

# KEYBOARD : 104Keys

# MOUSE : 3Buttons

MODULE DESCRIPTION

Base Station: 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.

Cognitive Radio: A cognitive radio transceiver is able to

adapt to the dynamic radio environment and the network

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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

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.

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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

multimedia services.