The document analyzes the performance of cooperative spectrum sensing for cognitive radio networks with different numbers of cognitive radio (CR) users over various fading channels. It finds that spectrum sensing is more difficult in Rayleigh and Nakagami fading channels compared to non-fading channels. It also determines that spectrum sensing performance improves when more CR users cooperate by sending their local sensing decisions to a fusion center. The paper presents mathematical expressions for detection and false alarm probabilities in non-fading, Rayleigh, and Nakagami fading environments. It observes through simulation that cooperative spectrum sensing provides better detection performance when more CR users participate.
Narrowband Spectrum Sensing for Different Fading Channels for Cognitive Radio...IJMERJOURNAL
Abstract: Nowadays the demand of applications of wireless communication has increased rapidly which causes the scarcity of radio spectrum. To empower future wireless communication services, the radio spectrum management is a very important factor. Cognitiveradio is a promising technology which provides an innovative way to improve utilization efficiency of available electromagnetic spectrum by sensing spectrum and shares it without harmful interference to other users. Narrowband spectrum sensing is the technique where the bandwidth of active primary transmitter in the vicinity of cognitive radio is less than the coherence bandwidth of channel. Fading is one of the greatest impairment of narrowband spectrum sensing. It is deflection of the attenuation. It influences a signal over certain propagation media.A communication channel that experiences fading isknown as fading channel. The effects of fading can be reduced by several fading models. In this paper, performanceanalysis of several realistic fading models on narrowband channel using energy detection method is employed. Finally, performance comparison of various fading models is guaranteed through simulation.
Bounds on the Achievable Rates of Faded Dirty Paper Channel IJCNCJournal
Bounds on the achievable rate of a Gaussian channel in the case that the transmitter knows the
interference signal but not its fading coefficients are given. We generalize the analysis which were studied
in [1] and [4] so that their results are special cases of our analysis. We enforce our bounds by simulations
in which many numerical examples are drawn and investigated under different cases.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
In this paper, we consider the joint optimal sensing
and distributed MAC protocol design for cognitive radio
networks. Specifically, we design a synchronized MAC protocol
for dynamic spectrum sharing among multiple secondary
users, which incorporates spectrum sensing for protecting active
primary users. We perform saturation throughput analysis for
the proposed MAC protocol that explicitly captures spectrum
sensing performance. Then, we find its optimal configuration
by formulating a throughput maximization problem subject to
detection probability constraints for primary users. In particular,
the optimal solution of this optimization problem returns the
required sensing time for primary users’ protection and optimal
contention window for maximizing total throughput of the
secondary network. Finally, numerical results are presented to
illustrate a significant performance gain of the optimal sensing
and protocol configuration.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Classical Discrete-Time Fourier TransformBased Channel Estimation for MIMO-OF...IJCSEA Journal
In this document, we look at various time domain channel estimation methods with this constraint of null carriers at spectrumborders.We showin detail howto gauge the importance of the “border effect” depending on the number of null carriers, which may vary from one system to another. Thereby we assess the limit of the technique discussed when the number of null carriers is large. Finally the DFT with the truncated singular value decomposition (SVD) technique is proposed to completely eliminate the impact of the null subcarriers whatever their number. A technique for the determination of the truncation threshold for any MIMO-OFDM system is also proposed.
Narrowband Spectrum Sensing for Different Fading Channels for Cognitive Radio...IJMERJOURNAL
Abstract: Nowadays the demand of applications of wireless communication has increased rapidly which causes the scarcity of radio spectrum. To empower future wireless communication services, the radio spectrum management is a very important factor. Cognitiveradio is a promising technology which provides an innovative way to improve utilization efficiency of available electromagnetic spectrum by sensing spectrum and shares it without harmful interference to other users. Narrowband spectrum sensing is the technique where the bandwidth of active primary transmitter in the vicinity of cognitive radio is less than the coherence bandwidth of channel. Fading is one of the greatest impairment of narrowband spectrum sensing. It is deflection of the attenuation. It influences a signal over certain propagation media.A communication channel that experiences fading isknown as fading channel. The effects of fading can be reduced by several fading models. In this paper, performanceanalysis of several realistic fading models on narrowband channel using energy detection method is employed. Finally, performance comparison of various fading models is guaranteed through simulation.
Bounds on the Achievable Rates of Faded Dirty Paper Channel IJCNCJournal
Bounds on the achievable rate of a Gaussian channel in the case that the transmitter knows the
interference signal but not its fading coefficients are given. We generalize the analysis which were studied
in [1] and [4] so that their results are special cases of our analysis. We enforce our bounds by simulations
in which many numerical examples are drawn and investigated under different cases.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
In this paper, we consider the joint optimal sensing
and distributed MAC protocol design for cognitive radio
networks. Specifically, we design a synchronized MAC protocol
for dynamic spectrum sharing among multiple secondary
users, which incorporates spectrum sensing for protecting active
primary users. We perform saturation throughput analysis for
the proposed MAC protocol that explicitly captures spectrum
sensing performance. Then, we find its optimal configuration
by formulating a throughput maximization problem subject to
detection probability constraints for primary users. In particular,
the optimal solution of this optimization problem returns the
required sensing time for primary users’ protection and optimal
contention window for maximizing total throughput of the
secondary network. Finally, numerical results are presented to
illustrate a significant performance gain of the optimal sensing
and protocol configuration.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Classical Discrete-Time Fourier TransformBased Channel Estimation for MIMO-OF...IJCSEA Journal
In this document, we look at various time domain channel estimation methods with this constraint of null carriers at spectrumborders.We showin detail howto gauge the importance of the “border effect” depending on the number of null carriers, which may vary from one system to another. Thereby we assess the limit of the technique discussed when the number of null carriers is large. Finally the DFT with the truncated singular value decomposition (SVD) technique is proposed to completely eliminate the impact of the null subcarriers whatever their number. A technique for the determination of the truncation threshold for any MIMO-OFDM system is also proposed.
HORIZONTAL AND VERTICAL ZONE BASED LOCATION TECHNIQUES FOR WIRELESS SENSOR NE...ijwmn
Localization is an important feature in Wireless sensor networks (WSNs). Accuracy in node localization with proper synchronization and required localization of sensor nodes, save node energy and enhance the performance of communication network protocols. In this paper we propose distributed localization algorithms and assume position known Cluster Head (CH) and position unknown three beacon nodes for each cluster. Using trilateration technique beacon nodes are located. Additional beacon node is added to confirm the location of beacon nodes and maintain location accuracy. These position localized beacon nodes help to locate other sensor nodes. The proposed two distributed zone based localization algorithms
are (i) Horizontal Location Position System (H-LPS), where cluster is divided into Horizontal Zones (HZs) and beacon nodes locate in horizontal direction and (ii) Vertical Location Position System (V-LPS), where cluster is divided into Vertical Zones (VZs) and beacon nodes locate in vertical direction. The main advantage of zone based localization is nodes belonging to a bounded zone (horizontal or vertical) are localized and participate in WSN computing. If a bounded zone is eliminated during localization, then nodes do not participate in localization and thus save WSN computing. We provide zone based simulations for H-LPS and V-LPS in comparison with existing localization algorithms like Ad hoc Positioning System (APS), Recursive Positioning Estimation (RPE) and Directed Positioning Estimation (DPE). Performance evaluation of H-LPS and V-LPS illustrate that for zone based localization, H-LPS
and V-LPS perform better that existing localization techniques. Bounded z
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Performance Evaluation of Computationally Efficient Energy Detection Based Sp...IJRST Journal
The rapid growth of bandwidth demanding wireless technologies has led to the problem of spectrum scarcity. However, studies show that licensed spectrum is underutilized. Cognitive radio technology promises a solution to the problem by allowing unlicensed users, access to the licensed bands opportunistically. A prime component of the cognitive radio technology is spectrum sensing. Many spectrum sensing techniques have been developed to sense the presence or not of a licensed user. This paper evaluates the performance of the energy detection based spectrum sensing technique in noisy, fading, jamming, interference environments. Both single user detection and cooperative detection situations were investigated. Closed form solutions for the probabilities of detection and false alarm were derived. The analytical results were varied by numerical computations using Monte Carlo method with MATLAB. The performance of the computationally efficient energy detection (CE-ED) techniques were evaluated by use of Receiver Operating Characteristics (ROC) curves over additive white Gaussian noise (AWGN) and fading (Rayleigh & Nakagami-m) channels. Results show that for single user detection, the energy detection technique performs better in AWGN channel than in the fading channel models. The performance of cooperative detection is better than single user detection in fading environments.
A SIMULATION-BASED PERFORMANCE COMPARISON OF MANETS CDS CREATION ALGORITHMS U...csandit
Mobile Ad Hoc networks (MANETs) are gaining increased interest due to their wide range of
potential applications in civilian and military sectors. The self-control, self-organization,
topology dynamism, and bandwidth limitation of the wireless communication channel make
implementation of MANETs a challenging task. The Connected Dominating Set (CDS) has been
proposed to facilitate MANETs realization. Minimizing the CDS size has several advantages;
however, this minimization is NP complete problem; therefore, approximation algorithms are
used to tackle this problem. The fastest CDS creation algorithm is Wu and Li algorithm;
however, it generates a relatively high signaling overhead. Utilizing the location information of
network members reduces the signaling overhead of Wu and Li algorithm. In this paper, we
compare the performance of Wu and Li algorithm with its Location-Information-Based version
under two types of Medium Access Control protocols, and several network sizes. The MAC
protocols used are: a virtual ideal MAC protocol, and the IEEE 802.11 MAC protocol. The use
of a virtual ideal MAC enables us to investigate how the real-world performance of these
algorithms deviates from their ideal-conditions counterpart. The simulator used in this research
is the ns-2 network simulator.
Performance comparison of blind adaptive multiuser detection algorithmseSAT Journals
Abstract Blind multiuser detection algorithms are used to eliminate the Multiple Access Interference (MAI) and the Near-Far effect in mobile communication systems. Four kinds of blind multiuser detection algorithms applied to code-division multiple-access (CDMA) communication system are studied in this paper. Those algorithms are the Least Mean Squares (LMS), Recursive Least Squares (RLS), Kalman filter and subspace-based Kalman filter algorithms. The resultant signal to interference ratio (SIR) at the output of the receivers controlled by the four kinds of multi-user detection algorithm has been discussed in this paper. Simulation results show that the subspace based Kalman filter algorithm outperforms all other three algorithms. Subspace-based Kalman filter algorithm has faster convergence speed, more practical and the capability of CDMA system can be increased. Keywords: Blind multiuser detection, Code-division multiple access, Mean output energy, Adaptive filtering.
Use of location aided algorithm using wi fi in indoor ad-hoc systemseSAT Journals
Abstract Mobile Ad-Hoc networks are designed to establish a network anytime and anywhere. Unlike other networks, ad-hoc does not require a fixed infrastructure. There are various routing techniques which are related to ad-hoc networking like Destination Sequenced Distance Vector Protocol (DSDV), Dynamic Source Routing Protocol (DSR) and Ad-Hoc On Demand Distance Vector Protocol (AODV). One such routing protocol named Location Aided Routing uses GPS (Global Positioning System) to get the co-ordinates of the nodes which would assist in routing. There is a definite set of drawbacks where GPS is used to get the location for the nodes in the ad-hoc network which is implemented indoor. In this paper, we propose an alternative of using Wi-Fi Positioning System to get the location of the co-ordinates which may prove to be a better solution than GPS indoor. Index Terms: Ad-Hoc Networks, DSDV, DSR, AODV, LAR, GPS, Wi-Fi Positioning System
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
In this paper, a new algorithm for a high resolution
Direction Of Arrival (DOA) estimation method for multiple
wideband signals is proposed. The proposed method proceeds
in two steps. In the first step, the received signals data is
decomposed in a Toeplitz form using the first-order statistics.
In the second step, The QR decomposition is applied on the
constructed Toeplitz matrix. Compared with existing schemes,
the proposed scheme provides several advantages. First, it
requires computing the triangular matrix R or the orthogonal
matrix Q to find the DOA; these matrices can be computed
with O(n2) operation. However, most of the existing schemes
required eignvalue decomposition (EVD) for the covariance
matrix or singular value decomposition (SVD) for the data
matrix; using EVD or SVD requires much more complex
computational O(n3) operation. Second, the proposed scheme
is more suitable for high-speed communication since it
requires first-order statistics and a single snapshot. Third,
the proposed scheme can estimate the correlated wideband
signals without using spatial smoothing techniques; whereas,
already-existing schemes do not. Accuracy of the proposed
wideband DOA estimation method is evaluated through
computer simulation in comparison with a conventional
method.
In the last few years Compressed Sampling (CS) has been well used in the area of signal processing and image compression. Recently, CS has been earning a great interest in the area of wireless communication networks. CS exploits the sparsity of the signal processed for digital acquisition to reduce the number of measurement, which leads to reductions in the size, power consumption, processing time and processing cost. This article presents application of CS for the spectrum sensing and channel estimation in Cognitive Radio (CR) networks. Basic approach of CS is introduced first, and then scheme for spectrum sensing and channel estimation for CR is discussed. First, fast and efficient compressed spectrum sensing (CSS) scheme is proposed to detect wideband spectrum, where samples are taken at sub-Nyquist rate and signal acquisition is terminated automatically once the samples are sufficient for the best spectral recovery and then, after the spectrum sensing, in the second phase notion of multipath sparsity is formalized and a novel approach based on Orthogonal Matching Pursuit (OMP) is discussed to estimate sparse multipath channels for CR networks. The effectiveness of the proposed scheme is demonstrated through comparisons with the existing conventional spectrum sensing and channel estimation methods.
A HYBRID DENOISING APPROACH FOR SPECKLE NOISE REDUCTION IN ULTRASONIC B-MODE ...csijjournal
In the literature a large number of linear and nonlinear denoising approaches for ultrasonic B-mode
images. The main purpose of this paper is to test the effect of hybridization of the Log Gabor filter with the
otheapproaches. The log-Gabor functions, by definition, always have no DC component, and secondly, the
transfer function of the log Gabor function has an extended tail at the high frequency end. Results show
that thhybridization of the Log Gabor with the Median filter gives the best output images and PSNR output
values.
Performance Evaluation of DV-HOP and Amorphous Algorithms based on Localizati...TELKOMNIKA JOURNAL
In the field of high-risk observation, the nodes in Wireless Sensor Network (WSN) are distributed
randomly. The result from sensing becomes meaningless if it is not known from where the originating node
is. Therefore, a sensor node positioning scheme, known as the localization scheme, is required. The
localization scheme consists of distance estimation and position computing. Thus, this research used
connectivity as distance estimation within range free algorithm DV-Hop and Amorphous, and then trilateral
algorithm for computing the position. Besides that, distance estimation using the connectivity between
nodes is not needed for the additional hardware ranging as required by a range-based localization
scheme. In this research compared the localization algorithm based on range free localization, which are
DV-Hop algorithm and Amorphous algorithm. The simulation result shows that the amorphous alg orithm
have achieved 13.60% and 24.538% lower than dv-hop algorithm for each parameter error localization and
energy consumption. On node density variations, dv-hop algorithm gained a localization error that is
26.95% lower than amorphous algorithm, but for energy consumption parameter, amorphous gained
14.227% lower than dv-hop algorithm. In the communication range variation scenario, dv-hop algorithm
gained a localization error that is50.282% lower than amorphous. However, for energy consumption
parameter, amorphous algorithm gained 12.35%. lower than dv-hop algorithm.
Performance Comparison of Energy Detection Based Spectrum Sensing for Cogniti...irjes
With the rapid deployment of new wireless devices and applications, the last decade has witnessed a growing
demand for wireless radio spectrum. However, the policy of fixed spectrum assignment produces a bottleneck for more
efficient spectrum utilization, such that a great portion of the licensed spectrum is severely under-utilized. So the concept of
cognitive radio was introduced to address this issue.The inefficient usage of the limited spectrum necessitates the
development of dynamic spectrum access techniques, where users who have no spectrum licenses, also known as secondary
users, are allowed to use the temporarily unused licensed spectrum. For this purpose we have to know the presence or
absence of primary users for spectrum usage. So spectrums sensing is one of the major requirements of cognitive radio.Many
spectrum sensing techniques have been developed to sense the presence or absence of a licensed user. This paper evaluates
the performance of the energy detection based spectrum sensing technique in noisy and fading environments.The
performance of the energy detection technique will be evaluated by use of Receiver Operating Characteristics (ROC) curves
over additive white Gaussian noise (AWGN) and fading channels.
Spectrum Sensing Detection with Sequential Forward Search in Comparison to Kn...IJMTST Journal
FCC is currently working on the concept of white space users “borrowing” spectrum from free license
holders temporarily to improve the spectrum utilization.
This project provides a relation between a Pf and the SNR value of any spectrum detector to have a
certain performance. Previous spectrum sensing detection techniques are only suitable for Low SNR and
are based on signal information values. But these methods are purely narrow band spectrum applications
In order to overcome the above said drawbacks we propose a novel method of spectrum sensing method
and is suitable for low and high SNR values, the sensed spectrum applicable for wide band applications.
Our proposed method does not require signal information at the receiver and channel information, because
this flexibility sensing rate is very high compared to previous techniques.
Bit Error Rate Assessment of Digital Modulation Schemes on Additive White Gau...inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
A novel scheme to improve the spectrum sensing performanceIJCNCJournal
Due to limited availability of spectrum for license
d users only, the need for secondary access by unli
censed
users is increasing. Cognitive radio turns out to b
e helping this situation because all that is needed
is a
technique that could efficiently detect the empty s
paces and provide them to the secondary devices wit
hout
causing any interference to the primary (licensed)
users. Spectrum sensing is the foremost function of
the
cognitive radio which senses the environment for wh
ite spaces. Energy detection is one of the various
spectrum sensing techniques that are under research
. Earlier it was shown that energy detection works
better under AWGN channel as compared to Rayleigh c
hannel, however the conventional spectrum sensing
techniques have a high probability of false alarm a
nd also show a better probability of detection for
higher
values of SNR. There is a need for a new technique
that shows a reduced probability of false alarm as
well
as an increase in the probability of detection for
lower values of SNR. In the present work the conven
tional
energy detection technique has been enhanced to get
better results.
HORIZONTAL AND VERTICAL ZONE BASED LOCATION TECHNIQUES FOR WIRELESS SENSOR NE...ijwmn
Localization is an important feature in Wireless sensor networks (WSNs). Accuracy in node localization with proper synchronization and required localization of sensor nodes, save node energy and enhance the performance of communication network protocols. In this paper we propose distributed localization algorithms and assume position known Cluster Head (CH) and position unknown three beacon nodes for each cluster. Using trilateration technique beacon nodes are located. Additional beacon node is added to confirm the location of beacon nodes and maintain location accuracy. These position localized beacon nodes help to locate other sensor nodes. The proposed two distributed zone based localization algorithms
are (i) Horizontal Location Position System (H-LPS), where cluster is divided into Horizontal Zones (HZs) and beacon nodes locate in horizontal direction and (ii) Vertical Location Position System (V-LPS), where cluster is divided into Vertical Zones (VZs) and beacon nodes locate in vertical direction. The main advantage of zone based localization is nodes belonging to a bounded zone (horizontal or vertical) are localized and participate in WSN computing. If a bounded zone is eliminated during localization, then nodes do not participate in localization and thus save WSN computing. We provide zone based simulations for H-LPS and V-LPS in comparison with existing localization algorithms like Ad hoc Positioning System (APS), Recursive Positioning Estimation (RPE) and Directed Positioning Estimation (DPE). Performance evaluation of H-LPS and V-LPS illustrate that for zone based localization, H-LPS
and V-LPS perform better that existing localization techniques. Bounded z
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Performance Evaluation of Computationally Efficient Energy Detection Based Sp...IJRST Journal
The rapid growth of bandwidth demanding wireless technologies has led to the problem of spectrum scarcity. However, studies show that licensed spectrum is underutilized. Cognitive radio technology promises a solution to the problem by allowing unlicensed users, access to the licensed bands opportunistically. A prime component of the cognitive radio technology is spectrum sensing. Many spectrum sensing techniques have been developed to sense the presence or not of a licensed user. This paper evaluates the performance of the energy detection based spectrum sensing technique in noisy, fading, jamming, interference environments. Both single user detection and cooperative detection situations were investigated. Closed form solutions for the probabilities of detection and false alarm were derived. The analytical results were varied by numerical computations using Monte Carlo method with MATLAB. The performance of the computationally efficient energy detection (CE-ED) techniques were evaluated by use of Receiver Operating Characteristics (ROC) curves over additive white Gaussian noise (AWGN) and fading (Rayleigh & Nakagami-m) channels. Results show that for single user detection, the energy detection technique performs better in AWGN channel than in the fading channel models. The performance of cooperative detection is better than single user detection in fading environments.
A SIMULATION-BASED PERFORMANCE COMPARISON OF MANETS CDS CREATION ALGORITHMS U...csandit
Mobile Ad Hoc networks (MANETs) are gaining increased interest due to their wide range of
potential applications in civilian and military sectors. The self-control, self-organization,
topology dynamism, and bandwidth limitation of the wireless communication channel make
implementation of MANETs a challenging task. The Connected Dominating Set (CDS) has been
proposed to facilitate MANETs realization. Minimizing the CDS size has several advantages;
however, this minimization is NP complete problem; therefore, approximation algorithms are
used to tackle this problem. The fastest CDS creation algorithm is Wu and Li algorithm;
however, it generates a relatively high signaling overhead. Utilizing the location information of
network members reduces the signaling overhead of Wu and Li algorithm. In this paper, we
compare the performance of Wu and Li algorithm with its Location-Information-Based version
under two types of Medium Access Control protocols, and several network sizes. The MAC
protocols used are: a virtual ideal MAC protocol, and the IEEE 802.11 MAC protocol. The use
of a virtual ideal MAC enables us to investigate how the real-world performance of these
algorithms deviates from their ideal-conditions counterpart. The simulator used in this research
is the ns-2 network simulator.
Performance comparison of blind adaptive multiuser detection algorithmseSAT Journals
Abstract Blind multiuser detection algorithms are used to eliminate the Multiple Access Interference (MAI) and the Near-Far effect in mobile communication systems. Four kinds of blind multiuser detection algorithms applied to code-division multiple-access (CDMA) communication system are studied in this paper. Those algorithms are the Least Mean Squares (LMS), Recursive Least Squares (RLS), Kalman filter and subspace-based Kalman filter algorithms. The resultant signal to interference ratio (SIR) at the output of the receivers controlled by the four kinds of multi-user detection algorithm has been discussed in this paper. Simulation results show that the subspace based Kalman filter algorithm outperforms all other three algorithms. Subspace-based Kalman filter algorithm has faster convergence speed, more practical and the capability of CDMA system can be increased. Keywords: Blind multiuser detection, Code-division multiple access, Mean output energy, Adaptive filtering.
Use of location aided algorithm using wi fi in indoor ad-hoc systemseSAT Journals
Abstract Mobile Ad-Hoc networks are designed to establish a network anytime and anywhere. Unlike other networks, ad-hoc does not require a fixed infrastructure. There are various routing techniques which are related to ad-hoc networking like Destination Sequenced Distance Vector Protocol (DSDV), Dynamic Source Routing Protocol (DSR) and Ad-Hoc On Demand Distance Vector Protocol (AODV). One such routing protocol named Location Aided Routing uses GPS (Global Positioning System) to get the co-ordinates of the nodes which would assist in routing. There is a definite set of drawbacks where GPS is used to get the location for the nodes in the ad-hoc network which is implemented indoor. In this paper, we propose an alternative of using Wi-Fi Positioning System to get the location of the co-ordinates which may prove to be a better solution than GPS indoor. Index Terms: Ad-Hoc Networks, DSDV, DSR, AODV, LAR, GPS, Wi-Fi Positioning System
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
In this paper, a new algorithm for a high resolution
Direction Of Arrival (DOA) estimation method for multiple
wideband signals is proposed. The proposed method proceeds
in two steps. In the first step, the received signals data is
decomposed in a Toeplitz form using the first-order statistics.
In the second step, The QR decomposition is applied on the
constructed Toeplitz matrix. Compared with existing schemes,
the proposed scheme provides several advantages. First, it
requires computing the triangular matrix R or the orthogonal
matrix Q to find the DOA; these matrices can be computed
with O(n2) operation. However, most of the existing schemes
required eignvalue decomposition (EVD) for the covariance
matrix or singular value decomposition (SVD) for the data
matrix; using EVD or SVD requires much more complex
computational O(n3) operation. Second, the proposed scheme
is more suitable for high-speed communication since it
requires first-order statistics and a single snapshot. Third,
the proposed scheme can estimate the correlated wideband
signals without using spatial smoothing techniques; whereas,
already-existing schemes do not. Accuracy of the proposed
wideband DOA estimation method is evaluated through
computer simulation in comparison with a conventional
method.
In the last few years Compressed Sampling (CS) has been well used in the area of signal processing and image compression. Recently, CS has been earning a great interest in the area of wireless communication networks. CS exploits the sparsity of the signal processed for digital acquisition to reduce the number of measurement, which leads to reductions in the size, power consumption, processing time and processing cost. This article presents application of CS for the spectrum sensing and channel estimation in Cognitive Radio (CR) networks. Basic approach of CS is introduced first, and then scheme for spectrum sensing and channel estimation for CR is discussed. First, fast and efficient compressed spectrum sensing (CSS) scheme is proposed to detect wideband spectrum, where samples are taken at sub-Nyquist rate and signal acquisition is terminated automatically once the samples are sufficient for the best spectral recovery and then, after the spectrum sensing, in the second phase notion of multipath sparsity is formalized and a novel approach based on Orthogonal Matching Pursuit (OMP) is discussed to estimate sparse multipath channels for CR networks. The effectiveness of the proposed scheme is demonstrated through comparisons with the existing conventional spectrum sensing and channel estimation methods.
A HYBRID DENOISING APPROACH FOR SPECKLE NOISE REDUCTION IN ULTRASONIC B-MODE ...csijjournal
In the literature a large number of linear and nonlinear denoising approaches for ultrasonic B-mode
images. The main purpose of this paper is to test the effect of hybridization of the Log Gabor filter with the
otheapproaches. The log-Gabor functions, by definition, always have no DC component, and secondly, the
transfer function of the log Gabor function has an extended tail at the high frequency end. Results show
that thhybridization of the Log Gabor with the Median filter gives the best output images and PSNR output
values.
Performance Evaluation of DV-HOP and Amorphous Algorithms based on Localizati...TELKOMNIKA JOURNAL
In the field of high-risk observation, the nodes in Wireless Sensor Network (WSN) are distributed
randomly. The result from sensing becomes meaningless if it is not known from where the originating node
is. Therefore, a sensor node positioning scheme, known as the localization scheme, is required. The
localization scheme consists of distance estimation and position computing. Thus, this research used
connectivity as distance estimation within range free algorithm DV-Hop and Amorphous, and then trilateral
algorithm for computing the position. Besides that, distance estimation using the connectivity between
nodes is not needed for the additional hardware ranging as required by a range-based localization
scheme. In this research compared the localization algorithm based on range free localization, which are
DV-Hop algorithm and Amorphous algorithm. The simulation result shows that the amorphous alg orithm
have achieved 13.60% and 24.538% lower than dv-hop algorithm for each parameter error localization and
energy consumption. On node density variations, dv-hop algorithm gained a localization error that is
26.95% lower than amorphous algorithm, but for energy consumption parameter, amorphous gained
14.227% lower than dv-hop algorithm. In the communication range variation scenario, dv-hop algorithm
gained a localization error that is50.282% lower than amorphous. However, for energy consumption
parameter, amorphous algorithm gained 12.35%. lower than dv-hop algorithm.
Performance Comparison of Energy Detection Based Spectrum Sensing for Cogniti...irjes
With the rapid deployment of new wireless devices and applications, the last decade has witnessed a growing
demand for wireless radio spectrum. However, the policy of fixed spectrum assignment produces a bottleneck for more
efficient spectrum utilization, such that a great portion of the licensed spectrum is severely under-utilized. So the concept of
cognitive radio was introduced to address this issue.The inefficient usage of the limited spectrum necessitates the
development of dynamic spectrum access techniques, where users who have no spectrum licenses, also known as secondary
users, are allowed to use the temporarily unused licensed spectrum. For this purpose we have to know the presence or
absence of primary users for spectrum usage. So spectrums sensing is one of the major requirements of cognitive radio.Many
spectrum sensing techniques have been developed to sense the presence or absence of a licensed user. This paper evaluates
the performance of the energy detection based spectrum sensing technique in noisy and fading environments.The
performance of the energy detection technique will be evaluated by use of Receiver Operating Characteristics (ROC) curves
over additive white Gaussian noise (AWGN) and fading channels.
Spectrum Sensing Detection with Sequential Forward Search in Comparison to Kn...IJMTST Journal
FCC is currently working on the concept of white space users “borrowing” spectrum from free license
holders temporarily to improve the spectrum utilization.
This project provides a relation between a Pf and the SNR value of any spectrum detector to have a
certain performance. Previous spectrum sensing detection techniques are only suitable for Low SNR and
are based on signal information values. But these methods are purely narrow band spectrum applications
In order to overcome the above said drawbacks we propose a novel method of spectrum sensing method
and is suitable for low and high SNR values, the sensed spectrum applicable for wide band applications.
Our proposed method does not require signal information at the receiver and channel information, because
this flexibility sensing rate is very high compared to previous techniques.
Bit Error Rate Assessment of Digital Modulation Schemes on Additive White Gau...inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
A novel scheme to improve the spectrum sensing performanceIJCNCJournal
Due to limited availability of spectrum for license
d users only, the need for secondary access by unli
censed
users is increasing. Cognitive radio turns out to b
e helping this situation because all that is needed
is a
technique that could efficiently detect the empty s
paces and provide them to the secondary devices wit
hout
causing any interference to the primary (licensed)
users. Spectrum sensing is the foremost function of
the
cognitive radio which senses the environment for wh
ite spaces. Energy detection is one of the various
spectrum sensing techniques that are under research
. Earlier it was shown that energy detection works
better under AWGN channel as compared to Rayleigh c
hannel, however the conventional spectrum sensing
techniques have a high probability of false alarm a
nd also show a better probability of detection for
higher
values of SNR. There is a need for a new technique
that shows a reduced probability of false alarm as
well
as an increase in the probability of detection for
lower values of SNR. In the present work the conven
tional
energy detection technique has been enhanced to get
better results.
A SURVEY ON DYNAMIC SPECTRUM ACCESS TECHNIQUES FOR COGNITIVE RADIOijngnjournal
Cognitive radio (CR) is a new paradigm that utilizes the available spectrum band. The key characteristic of CR system is to sense the electromagnetic environment to adapt their operation and dynamically vary its radio operating parameters. The technique of dynamically accessing the unused spectrum band is known as Dynamic Spectrum Access (DSA). The dynamic spectrum access technology helps to minimize unused spectrum bands. In this paper, main functions of Cognitive Radio (CR) i.e. spectrum sensing, spectrum management, spectrum mobility and spectrum sharing are discussed. Then DSA models are discussed along with different methods of DSA such as Command and Control, Exclusive-Use, Shared Use of Primary Licensed User and Commons method. Game-theoretic approach using Bertrand game model, Markovian Queuing Model for spectrum allocation in centralized architecture and Fuzzy logic based method are also discussed and result are shown.
Performance Analysis and Comparative Study of Cognitive Radio Spectrum Sensin...IOSR Journals
Abstract : In cognitive radio, spectrum sensing is an emergent technology to find available and unused spectrum for increasing spectrum utilization and to overcome spectrum scarcity problem without harmful interference to licensed users. Cooperative spectrum sensing is used to give reliable performance in terms of detection probability and false alarm probability as well as in order to reduce fading, noise and shadowing effects on cognitive radio users. In this paper according to detection performance and complexity various cooperative spectrum sensing schemes have been discussed. We have analyzed spectrum sensing with different fusion rules and their comparative behavior has also been studied. Furthermore, we introduced AND-OR fusion rules in 2-bit and 3-bit hard combination schemes. Keywords - Cognitive radio, cooperative spectrum sensing, energy detector, spectrum sensing, hard combination
Performance Analysis and Comparative Study of Cognitive Radio Spectrum Sensin...IOSR Journals
In cognitive radio, spectrum sensing is an emergent technology to find available and unused
spectrum for increasing spectrum utilization and to overcome spectrum scarcity problem without harmful
interference to licensed users. Cooperative spectrum sensing is used to give reliable performance in terms of
detection probability and false alarm probability as well as in order to reduce fading, noise and shadowing
effects on cognitive radio users. In this paper according to detection performance and complexity various
cooperative spectrum sensing schemes have been discussed. We have analyzed spectrum sensing with different fusion rules and their comparative behavior has also been studied. Furthermore, we introduced AND-OR fusion rules in 2-bit and 3-bit hard combination schemes
An Approach to Spectrum Sensing in Cognitive Radio IOSR Journals
Recent research shows that more than 70% of the available spectrum is not utilized
efficiently. The bandwidth becomes expensive due to a shortage of frequencies. Therefore for efficient
utilization of spectrum, we need to sniff the spectrum to determine whether it is being used by primary user or
not. The term cognitive radio refers to the adoption of radio parameters using the sensed information
of the spectrum. There are various spectrum sensing techniques proposed in the literature but still there is
room for researchers in this field to explore more sophisticated approaches. There are three major
categories of spectrum sensing techniques; transmitter detection, receiver detection and interference
temperature detection. This thesis presents a survey of techniques suggested in the literature for
spectrum sensing with a performance analysis of transmitter-based detection techniques.
An Approach to Spectrum Sensing in Cognitive RadioIOSR Journals
Abstract: Recent research shows that more than 70% of the available spectrum is not utilized efficiently. The bandwidth becomes expensive due to a shortage of frequencies. Therefore for efficient utilization of spectrum, we need to sniff the spectrum to determine whether it is being used by primary user or not. The term cognitive radio refers to the adoption of radio parameters using the sensed information of the spectrum. There are various spectrum sensing techniques proposed in the literature but still there is room for researchers in this field to explore more sophisticated approaches. There are three major categories of spectrum sensing techniques; transmitter detection, receiver detection and interference temperature detection. This thesis presents a survey of techniques suggested in the literature for spectrum sensing with a performance analysis of transmitter-based detection techniques. Keywords— Include at least 5 keywords or phrases
A Mathematical Approach for Hidden Node Problem in Cognitive Radio NetworksTELKOMNIKA JOURNAL
Cognitive radio (CR) technology has emerged as a realistic solution to the spectrum scarcity
problem in present day wireless networks. A major challenge in CR radio networks is the hidden node
problem, which is the inability of the CR nodes to detect the primary user. This paper proposes energy
detector-based distributed sequential cooperative spectrum sensing over Nakagami-m fading, as a tool to
solve the hidden node problem. The derivation of energy detection performance over Nakagami-m fading
channel is presented. Since the observation represents a random variable, likelihood ratio test (LRT) is
known to be optimal in this type of detection problem. The LRT is implemented using the Neyman-Pearson
Criterion (maximizing the probability of detection but at a constraint of false alarm probability). The
performance of the proposed method has been evaluated both by numerical analysis and simulations. The
effect of cooperation among a group of CR nodes and system parameters such as SNR, detection
threshold and number of samples per CR nodes is investigated. Results show improved detection
performance by implementing the proposed model.
Spectrum Sensing Detection Techniques for Overlay UsersIJMTST Journal
Spectrum allocated Agency (FCC) is currently working on the concept of white space users “borrowing” spectrum from free license holders temporarily to improve the spectrum utilization, i.e known as dynamic spectrum access (DSA). CRN systems can utilize dispersed spectrum, and thus such approach is known as dispersed spectrum cognitive radio systems. This project provides a tradeoff between a false alarm probability (Pf) and the signal to noise ratio (SNR) value of any spectrum detector to have a certain performance. Moreover, the performance of the cyclostationary detector (CD) and the matched filter detector (MF) is better than the energy detector(ED) especially at low signal to noise ratio values. Unfortunately, the cyclostationary spectrum sensing method, performance is not satisfying when the wireless fading channels are employed. In this project we provide the best trade off for spectrum usage for over lay users.
Bio-inspired route estimation in cognitive radio networks IJECEIAES
Cognitive radio is a technique that was originally created for the proper use of the radio electric spectrum due its underuse. A few methods were used to predict the network traffic to determine the occupancy of the spectrum and then use the ‘holes’ between the transmissions of primary users. The goal is to guarantee a complete transmission for the second user while not interrupting the trans-mission of primary users. This study seeks the multifractal generation of traffic for a specific radio electric spectrum as well as a bio-inspired route estimation for secondary users. It uses the MFHW algorithm to generate multifractal traces and two bio-inspired algo-rithms: Ant Colony Optimization and Max Feeding to calculate the secondary user’s path. Multifractal characteristics offer a predic-tion, which is 10% lower in comparison with the original traffic values and a complete transmission for secondary users. In fact, a hybrid strategy combining both bio-inspired algorithms promise a reduction in handoff. The purpose of this research consists on deriving future investigation in the generation of multifractal traffic and a mobility spectrum using bio-inspired algorithms.
Single User Eigenvalue Based Detection For Spectrum Sensing In Cognitive Rad...IJMER
Scarcity of spectrum is the issue that wireless communication technology has to deal with.
Primary user is the licensed user of the spectrum. When primary user is idle or not using the spectrum
secondary user can utilize the spectrum. This sharing of spectrum can be enabled by cognitive radio
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detection of primary signal at very low SNR (in the range of -20 dB), under noise and interference
uncertainty. This requirement makes spectrum sensing, a hard nut to crack. Another major issue in
detection is hidden node problem wherein the node in vicinity of primary transmitter also indicates
absence of the primary signal since it is hidden behind the large object. There are various algorithms
for detection viz. energy detection, matched filter detection, feature detection (cyclostationary
detection, eigen-value based detection etc.) These algorithms have limitations of complexity,
requirement of signal knowledge and detection performance. In this paper the performance of
eigenvalue based detection (EBD) method in presence of noise and low SNR of the received signal has
been evaluated for a single user.
Effective capacity in cognitive radio broadcast channelsMarwan Hammouda
Abstract—In this paper, we investigate effective capacity by
modeling a cognitive radio broadcast channel with one secondary transmitter (ST) and two secondary receivers (SRs) under quality-of-service constraints and interference power limitations.We initially describe three different ooperative channel sensing strategies with different ard-decision combining algorithms at the ST, namely OR, Majority, and AND rules. Since the channel sensing occurs with possible errors, we consider a combined
interference power constraint by which the transmission power of the secondary users (SUs) is bounded when the channel is sensed as both busy and idle. Furthermore, regarding the channel sensing decision and its correctness, there exist ...
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Performance of cooperative spectrum sensing for different number of cr users in cognitive radio
1. International Journal of Science and Research (IJSR), India Online ISSN: 2319-7064
Volume 1 Issue 3, December 2012
www.ijsr.net
Performance of Cooperative Spectrum Sensing for Different
Number of CR users in Cognitive Radio
Mohammad Alamgir Hossain1
, Shahoreare Ahmed2
, Md. Shamim Hossain3
, Md. Ibrahim Abdullah4
1
B.sc (Hons) & M.sc in CSE, Islamic University, Bangladesh
alamgirlovely@yahoo.com
2
B.sc (Engineer) in EEE, International Islamic University Chittagong, Bangladesh
nshahoreare@gmail.com
3
Department of CSE, Islamic University, Bangladesh
shamimmalitha@yahoo.com
4
Department of CSE, Islamic University, Bangladesh
ibrahim25si@yahoo.com
Abstract: We have studied the performance of cooperative spectrum sensing for different number of CR users in cognitive radio over
non-fading channel AWGN and fading channels such as Rayleigh and Nakagami. This paper presents a simulation comparison of these
fading channels based on fusion OR-rule. We observe that spectrum sensing for different number of CR users is harder in presence of
Rayleigh and Nakagami fading than non-fading AWGN channel. It also shows that spectrum sensing gives better performance when
more number of CR users is cooperated.
Keywords: cognitive radio, cooperative spectrum sensing, fading channels, energy detection
1. Introduction
Cognitive radio is defined as software defined radio
which is aware of its environment, learns from and has the
ability to change its parameters according to these changes in
its environment and the networks requirements [1]. The
concept of cognitive radio has been introduced to alleviate
the spectrum under-utilization problem of wireless
communications. One of the most challenging tasks in
cognitive radio networks is spectrum sensing, which is
required to opportunistically access the idle radio spectrum.
Existing spectrum sensing techniques can be divided into
three types [2]: energy detection, matched filter detection
and cyclostationary detection. Among them, energy
detection has been widely applied since it does not require
any a priori knowledge of primary signals and has much
lower complexity than the other two schemes. The radio
channel is characterized by two types of fading effects: large
scale fading and small scale fading [3], [4]. Small scale
fading models include the well-known Rayleigh, Rice, and
Nakagami-m [5]-[6] distributions. For large scale fading
conditions, it is widely accepted that the probability density
function (PDF) of the fading envelopes can be modeled by
the well-known Log-normal distribution [7], [8]. Due to the
several multipath fading, a cognitive radio may fail to notice
the presence of the PU and then will access the licensed
channel and cause interference to the PU. To combat these
impacts, cooperative spectrum sensing schemes have been
proposed to obtain the spatial diversity in multiuser CR
networks [9-11]. The performance of single CR user based
spectrum sensing in fading channels such as Rayleigh,
Nakagami, Weibull has been studied in [12]. The
performance of cooperative spectrum sensing with censoring
of cognitive radios in Rayleigh fading channel has been
evaluated in [13-15]. Cooperative spectrum sensing
improves the detection performance. All CR users sense the
PU individually and send their sensing information in the
form of 1-bit binary decisions (1 or 0) to Fusion center (FC).
The hard decision combining rule (OR, AND, and
MAJORITY rule) is performed at FC using a counting rule
to make the final decision regarding whether the primary
user present or not [16]-[18]. Cooperative spectrum sensing
has been addressed in [19-22]. However, the existed works
examined the additive white Gaussian noise (AWGN)
channel and the Rayleigh fading channel. In this paper, we
study performance of cooperative spectrum sensing for
different number of CR users in cognitive radio.
The rest of this paper is organized as follows. In Section
II, the system model is introduced. In Section III, detection
and false alarm probabilities of non-fading AWGN and
fading channel such as Rayleigh and Nakagami are
described. Cooperative spectrum sensing over various fading
channels is derived in Section IV. The simulation result and
discussion are presented in section V. Finally, we draw our
conclusions in Section VI.
2. System Model
The local spectrum sensing is to decide between the
following two hypotheses,
1
0
H
H
tnths
tn
tx
(1)
where x(t) is the signal received by secondary user and
s(t) is primary user’s transmitted signal, n(t) is the additive
white Gaussian noise (AWGN) and h is the amplitude gain
of the channel.
The energy collected in the frequency domain is denoted
by Y which serves as a decision statistic. Following the work
145
2. International Journal of Science and Research (IJSR), India Online ISSN: 2319-7064
Volume 1 Issue 3, December 2012
www.ijsr.net
of Urkowitz [23], Y may be shown to have the following
distribution,
1
0
,2
2
2
2
2 H
H
Y
TW
TW
(2)
where TW2
2
and 22
2
TW denote central and non-
central chi-square distributions respectively, each with 2TW
degrees of freedom and a non-centrality parameter of 2γ for
the latter distribution. For simplicity we assume that time-
bandwidth product, TW, is an integer number which we
denote by u.
3. Detection and False Alarm Probabilities
In this section, we give the average detection probability
over Rayleigh and Nakagami fading channels and in closed
form [24]. In communications theory, Nakagami
distributions and Rayleigh distributions are used to model
scattered signals that reach a receiver by multiple paths.
Depending on the density of the scatter, the signal will
display different fading characteristics. Rayleigh and
Nakagami distributions are used to model dense scatters.
Nakagami distributions can be reduced to Rayleigh
distributions, but give more control over the extent of the
fading.
3.1 Non-fading environment (AWGN channel)
In non-fading environment the average probability of
false alarm, the average probability of detection, and the
average probability of missed detection are given,
respectively, by [24]
,2| 1 ud QHYPP (3)
u
u
HYPPf
2/,
| 0
(4)
and
dm PP 1 (5)
where λ denotes the energy threshold. Γ(.) and Γ(.,.) are
complete and incomplete gamma functions respectively [25]
and .,.uQ is the generalized Marcum Q-function defined
as follows,
dxaxIe
a
x
baQ u
ax
u
u
u 1
0
2
1
22
,
where .1uI is the modified Bessel function of (u−1)th
order. If the signal power is unknown, we can first set the
false alarm probability fP to a specific constant. By equation
(4), the detection threshold λ can be determined. Then, for
the fixed number of samples 2TW the detection probability
dP can be evaluated by substituting the λ in (3). As
expected, fP is independent of γ since under 0
H there is no
primary signal present. When h is varying due to fading,
equation (3) gives the probability of detection as a function
of the instantaneous SNR, γ. In this case, the average
probability of detection dP may be derived by averaging (3)
over fading statistics [19],
dxxfQP
x
ud ,2 (6)
where fγ(x) is the probability distribution function (PDF)
of SNR under fading.
3.2 Rayleigh Fading Channels
When the composite received signal consists of a large
number of plane waves, for some types of scattering
environments, the received signal has a Rayleigh distribution
[26]. If the signal amplitude follows a Rayleigh distribution,
then the SNR γ follows an exponential PDF given by
exp
1
f , 0 (7)
In this case, a closed-form formula for dP may be
obtained (after some manipulation) by substituting xf in
(6),
1
2
0
2
1
2!
1
u
u
k
k
dRay
k
eP
2
0 12!
1
212
u
k
k
ee
(8)
3.3 Nakagami Fading Channel
Although Rayleigh and Ricean distributions are the most
popular distributions to model fading channels, some
experimental data does not fit well into neither of these
distributions. Thus, a more general fading distribution was
developed whose parameters can be adjusted to fit a variety
of empirical measurements [25]. This distribution is called
the Nakagami fading distribution. The Nakagami distribution
was introduced by Nakagami in the early 1940’s to
characterize rapid fading in long distance HF channels [27].
It is possible to describe both Rayleigh and Rician fading
with the help of a single model using the Nakagami
distribution. The Nakagami m-distribution is used in
communication systems characterize the statistics of signal
transmitted through multipath fading channels.
The Nakagami distribution is often used for the
following reasons. First, the Nakagami distribution can
model fading conditions that are either more or less severe
than Rayleigh fading. When m=1, the Nakagami distribution
becomes the Rayleigh distribution, when m=1/2, it becomes
a one-sided Gaussian distribution, and when m=∞ the
distribution becomes an impulse (no fading). Second, the
Rice distribution can be closely approximated by using the
following relation between the Rice factor K and the
Nakagami shape factor m [27];
146
3. International Journal of Science and Research (IJSR), India Online ISSN: 2319-7064
Volume 1 Issue 3, December 2012
www.ijsr.net
mmm
mm
K
2
2
1m
12
1
2
K
K
m
Since the Rice distribution contains a Bessel function
while the Nakagami distribution does not, the Nakagami
distribution often leads to convenient closed form analytical
expressions that are otherwise unattainable. Using the
alternative representation of Marcum-Q function given in
[28, eq. (4.74), pp. 104], (1) can be written as,
kun
kn
n
u
k
e
n
e
Q
2!!
,2
1
0
2
0
(9)
If the signal amplitude follows a Nakagami distribution,
then the PDF of γ follows a gamma PDF given by
mm
m
f m
m
exp
1 1
, 0 (10)
where m is the Nakagami parameter. The average dP in
the case of Nakagami channels dNakP can now be obtained
by averaging (3) over (10) and then using again the change
of variable 2x yielding
dxxQ
mx
xP u
m
dNak
,
2
exp
0
2
12
(11)
where
m
m
m
m
1
2
1
(12)
In this case, a closed-form formula of Nakagami
channels can be given by
1
1 1
11
2
;1;
!2
2/u
n
dNak
m
nmF
n
GP
(13)
where .;.;.11 F is the confluent hypergeometric
function [18].
2/2
e
m
m
m
(14)
and
dxxQ
mx
xG u
m
0
2
12
1 ,
2
exp
(15)
Where Q(.,.)=Q(.,.) is the first-order Marcum Q-function.
G1 can be evaluated for inter m with the aid of [25, Eq.(25)]
1
2
1
1 1
!12
m
m
m
m
m
m
mm
e
mm
m
G
m
L
m
m
m
L
m
n
n
n
m
22
2
0
1
(16)
where is the Laguerre polynomial of degree n [25,
8.970].
4. Cooperative Spectrum Sensing over various
Fading Channels
In real communication environments, the hidden terminal
problem, deep fading and shadowing, etc., would deteriorate
the signal detection performance of cognitive users. To
address this issue, multiple cognitive radios can be
coordinated to perform spectrum sensing. Several recent
works have shown that cooperative spectrum sensing can
greatly increase the probability of detection in fading
channels [19], [29].
Let N denote the number of users sensing the PU. Each
CR user makes its own decision regarding whether the
primary user present or not, and forwards the binary decision
(1 or 0) to fusion center (FC) for data fusion. The PU is
located far away from all CRs. All the CR users receive the
primary signal with same local mean signal power, i.e. all
CRs form a cluster with distance between any two CRs
negligible compared to the distance from the PU to a CR.
For simplicity we have assumed that the noise, fading
statistics and average SNR are the same for each CR user.
We consider that the channels between CRs and FC are ideal
channels (noiseless).
Assuming independent decisions, the fusion problem
where k out of N CR users are needed for decision can be
described by binomial distribution based on Bernoulli trials
where each trial represents the decision process of each CR
user. With a hard decision counting rule, the fusion center
implements an n–out-of-M rule that decides on the signal
present hypothesis whenever at least k out of the N CR user
decisions indicate 1H . Assuming uncorrelated decisions, the
probability of detection at the fusion center [30] is given by
N
kl
lN
id
l
idd PP
l
N
P ,, 1 (17)
where idP , is the probability of detection for each
individual CR user as defined by (3) and (6).
OR-rule : In this rule, if any one of the local decisions
sent to the decision maker is a logical one, the final decision
made by the decision maker is one. Cooperative detection
performance with this fusion rule can be evaluated by setting
k=1 in eq. (17).
N
idORd PP ,, 11 (18)
5. Simulation Result and Discussion
All simulation was done on MATLAB version R2011a
over two different fading under Rayleigh and Nakagami
channel and a non-fading channel AWGN. We described the
receiver through its complementary ROC curves for different
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4. International Journal of Science and Research (IJSR), India Online ISSN: 2319-7064
Volume 1 Issue 3, December 2012
www.ijsr.net
values of probability of false alarm and Cognitive Radio
user.
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
10
-4
10
-3
10
-2
10
-1
10
0
Cooperative Spectrum Sensing over non-Fading AWGN Channel
Probability of False alarm (Pfa)
ProbabilityofMissedDetection(Pmd)
CR User=2
CR User=3
CR User=4
Figure 1: Complementary ROC of OR-rule over non-fading
AWGN channel ( =10dB, u=5).
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
10
-4
10
-3
10
-2
10
-1
10
0
Cooperative Spectrum Sensing over Rayleigh Fading Channel
Probability of False alarm (Pfa)
ProbabilityofMissedDetection(Pmd)
CR User=2
CR User=3
CR User=4
Figure 2: Complementary ROC of OR-rule over Rayleigh
fading channel ( =10dB, u=5).
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
10
-4
10
-3
10
-2
10
-1
10
0
Cooperative Spectrum Sensing over Nakagami m=3 Fading Channel
Probability of False alarm (Pfa)
ProbabilityofMissedDetection(Pmd)
CR User=2
CR User=3
CR User=4
Figure 3: Complementary ROC of OR-rule over Nakagami
fading channel ( =10dB, u=5, m=3).
Fig. 1, 2, and 3 show the complementary ROC of fusion
OR rule for different number of cooperative users. CR users
are taken 2, 4 and 6 for simulation. Simulation is done for
cooperative spectrum sensing over non-fading AWGN
channel, Rayleigh and Nakagami fading channel
respectively. Average SNR and u are assumed to be 10 dB
and 5 respectively. Nakagami parameter m are set to be 3.
Simulation result shows that spectrum sensing is better when
more number of users are cooperated. It also shows that in
non-fading AWGN channel the sensing performance is
better than in other channels.
6. Conclusion
We have studied the performance of cooperative
spectrum sensing for different number of Cognitive Radio
users in Cognitive Radio. Performance of cooperative
spectrum sensing over Rayleigh and Nakagami fading are
presented and compared. It has been found that probability
of missed detection is decreased by using different number
of CR users.
We used OR rule as this has better performance than
AND and MAJORITY rule in various channels. We also
observe that spectrum sensing for different number of CR
users is harder in presence of Rayleigh and Nakagami fading
and performance of energy detection degrades more in
Nakagami channels than Rayleigh channel.
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Author Profile
Mohammad Alamgir Hossain received the B.Sc
and M.Sc degrees in Computer Science and
Engineering (CSE) from Islamic University (IU),
Kushtia-7003, Bangladesh in 2010 and 2012
respectively. His current research interest is in the
area of OFDM and Cognitive Radio.
Shahoreare Ahmed is studying B.SC degree with
engineering in Electrical and Electronics
Engineering in International Islamic University
Chittagong, Bangladesh. His current research interest
is in the area of Cognitive Radio, Renewable Energy
and Power System.
Md. Shamim Hossain has been received Bachelor’s
and Master’s degree in CSE from Islamic University,
Kushtia. Courrently he is a Lecturer of the
Department of Computer Science and Engineering
(CSE), Islamic University (IU) His areas of interest
include mobile communication & Cognitive Radio.
Md. Ibrahim Abdullah has been received the
Bachelor’s, Master’s and M.Phil degree in Applied
Physics & Electronics from Rajshahi University,
Rajshahi. Courrently he is an Associate Professor of
the department of CSE, Islamic University, Kushtia-
7003, Bangladesh. His areas of interest include
Network security, Wireless Sensor Network, mobile
communication & Cognitive Radio.
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