2011
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62
A Low-Complexity Cyclostationary-Based Detection Method for Cooperative Spectrum Sensing in Cognitive Radio Networks
2
2
Fast reliable spectrum sensing (SS) is a crucial problem in the cognitive radio systems. To address this issue, cyclostationarity-based detection methods, which are generally more complex but more reliable than energy detection methods, have been proposed. This paper presents a new method to detect the presence of the second-order cyclostationarity in the OFDM-based primary user (PU) signals. The proposed method has a low computational complexity, while it presents a performance close to the well-known GLRT-based Dandawaté-Giannakis's method. Moreover, since the proposed low-complexity method is robust against the noise uncertainty, it can be a good alternative to the energy detection method. We further propose some cooperative spectrum sensing methods to improve the detection performance. Extensive simulation results confirm the superiority of the proposed schemes.
1
10
Hamid
Arezumand
Hamid
Arezumand
Paeiz
Azmi
Paeiz
Azmi
Hamed
Sadeghi
Hamed
Sadeghi
Cooperative
Cyclostationarity-Based
Low-Complexity Spectrum Sensing
Soft Combination
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Bayesian-Based Cooperative Framework for Spectrum Sensing in Cognitive Radio Networks
2
2
Energy detection has been adopted as an alternative spectrum sensing method for cognitive radios due to its low computational complexity and not requiring a priori information about the signal to be detected. However, noise uncertainty and hidden terminal problem make energy detector practically challenging specially in low signal-to noise ratio (SNR) regime. Collaboration among multiple cognitive radios has been recognized as a practical strategy to improve the reliability of spectrum sensing. In this paper, a cooperative spectrum sensing framework is proposed to blindly determine the occupancy of a wideband spectrum. Specifically, contrary to conventional energy detector, the proposed method does not require any knowledge of noise variance to detect the presence of primary signals. Moreover, diversity achieved by cooperation enables the framework to maintain a reasonable performance even in low SNR values. Simulation results confirm the effectiveness of our proposed method in improving both the probabilities of detection and false alarm.
11
18
Vahid
Jamali Kooshkghazi
Vahid
Jamali Kooshkghazi
Nima
Reisi
Nima
Reisi
Mahmoud
Ahmadian
Mahmoud
Ahmadian
Soheil
Salari
Soheil
Salari
cognitive radio
cooperative spectrum sensing
energy detection
Generalized Bayesian estimator
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A Novel Blind Spectrum Sensing Algorithm for Cognitive Radio Systems Based on Algorithmic Information Theory
2
2
In this paper، we propose a new algorithm of spectrum sensing based on algorithmic information theory. Since the proposed algorithm is applied in time domain، resulting in an overall reduction on the system computational complexity. In this paper، we investigate two cases of wideband and narrowband spectrum sensing problems. To sense the spectrum، we propose to use some measures based on algorithmic information theory such as Lempel-Ziv Complexity (LZC)، Higuchi fractal dimension (HFD)، and Algorithmic mutual information (algorithmic MI). LZC and HFD are reliable and promising measures that calculate the complexity of a time series signal in a straight forward manner. On the other hand، algorithmic MI calculates the algorithmic mutual information between two time series signals. Our proposed algorithm is blind in the sense that it requires no prior knowledge of the channel، primary users’ signals، and noise variance. In simulation section، it is shown that our proposed algorithm has better performance in contrast with the other complexity based detectors such as Shannon entropy and spectral entropy based detectors.
19
26
Saeid
Balaneshin Kordan
Saeid
Balaneshin Kordan
Bahman
Abolhassani
Bahman
Abolhassani
Cognitive Radio
Blind Spectrum Sensing
Lempel-Ziv Complexity (LZC)
Higuchi Fractal Dimension (HFD)
Algorithmic mutual information
Entropy
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Joint Antenna Selection and Adaptive Modulation in MIMO Systems in the Presence of CSI Imperfection
2
2
This paper presents a strategy to combine the antenna selection technique and the adaptive modulation method for multiple input multiple output (MIMO) systems. The MIMO architecture significantly improves the performance of wireless systems at the expense of a radio frequency (RF) hardware complexity. However, the advantages of MIMO systems can be mainly maintained with simple hardware using antenna selection technique. Moreover, in order to improve the efficiency, the adaptive modulation method can be implemented. As a practical system design limitation, the perfect channel state information (CSI) may not be achievable. Accordingly, the effect of imperfect channel state information (ICSI) in the proposed systems has been investigated.
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33
Mahshad
Hamedanian
Mahshad
Hamedanian
Abbas
Mohammadi
Abbas
Mohammadi
Abdolali
Abdipour
Abdolali
Abdipour
MIMO
antenna selection
adaptive modulation
CSI imperfection
spectral efficiency
bit error rate
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Joint Power Adaptation and Interference Avoidance for Unlicensed Wireless Systems: A Game Theoretic Approach
2
2
In multiuser wireless systems, waveform adaptation is one of the interference management methods in which the users adaptively change their transmitting waveforms in signal space to enhance the system performance subject to some Quality-of-Service (QoS) requirements. In this paper, the uplink scenario of a Multi Carrier Code Division Multiple Access (MC-CDMA) is considered under slow and frequency selective fading. An admissibility test under maximum received power constraint is presented to check that if there exist feasiblepowers and waveforms for network users to hold the QoS constraint of each user above a predetermined level. In our set-up, a number of licensed (fixed) and unlicensed (agile) users share some orthogonal carriers to send data to a common receiver (or colocated independent receivers), subject to specific target SINRs for users. We analyze this system as a non-cooperative separable game and show the existence of Nash equilibrium point for this joint power control and codeword adaptation game.An iterative distributed algorithm based on better response strategy is presented which at the receiversresults in an ensemble of well-known Generalized Welch Bound Equality (GWBE) optimal waveforms and orthogonal waveforms for oversized users in addition to optimal transmission power for each user. We investigate the properties of fixed point and the effect of algorithm on the performance of fixed users’ network. Finally the algorithm will be confirmed by the numerical examples.
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45
Seyed Mohsen
Beheshti
Seyed Mohsen
Beheshti
Behrad
Mahboobi
Behrad
Mahboobi
Mehrdad
Ardebilipour
Mehrdad
Ardebilipour
Unlicensed communication
interference avoidance
MC-CDMA
waveform adaptation
transmitter optimization
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A Stochastic Geometry Analysis of Hybrid Cellular-Adhoc CDMA Networks
2
2
This paper studies the impact of using multihop wireless adhoc network in conjunction with cellular networks under a probabilistic routing strategy. Our objective is to obtain the outage probability of the twodimensional hybrid CDMA network under path loss. In the proposed network the base stations are placed on a regular grid and users are distributed randomly according to a homogeneous Poisson point process. To obtain the outage probability of the proposed hybrid network, we study the outage probability of a cellular CDMA wireless network on both uplink and downlink as well as the outage probability of a multihop ad hoc CDMA network. We validate our analytical expressions via Monte Carlo simulations. Our results demonstrate that in order to improve the performance of a hybrid wireless network with a large density of users, it is beneficial to use multihop ad hoc communication.
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54
Neda
Banivaheb
Neda
Banivaheb
Keivan
Navaie
Keivan
Navaie
hybrid networks
stochastic geometry
point process
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A Novel DS-CDMA Direction of Arrival Estimator for Frequency- Selective Fading Channel with Correlated Multipath by Using Beamforming Filter
2
2
In this paper, a new method for estimating the direction of arrival of Asynchronous DS-CDMA signals in multipath fading channel is proposed. In the proposed method, first, for removing the effects of undesired paths, we project the coherent signals of the undesired paths perpendicularly to the under process signal, next, the signal is passed through a filter bank.Byusing beam forming filters, the effectof other users on the desired users signal is decreased and hence, the search area is decreased almost to one tenth. In this algorithm, searching all angles is not required,to estimate the number of sources does not require any information criteria, andalso, the number of users can exceed the number of antenna arrays contrary to many of the conventional methods. Simulation results are illustrated to confirm the efficiency of the method.
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62
Farid
Samsami Khodadad
Farid
Samsami Khodadad
Ghosheh
Abed Hodtani
Ghosheh
Abed Hodtani
S. Bagher
Hosseini Karani
S. Bagher
Hosseini Karani
Hossein
Khoshbin Ghasem
Hossein
Khoshbin Ghasem
Direction of arrival estimation
orthogonal projection
beam forming
frequency-selective fading channel
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