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Underwater superoleophobic‐oleophilic chips were developed to achieve oil extracting from aqueous solution and oil‐droplet condensing to preset microwell. The double‐hierarchical (extracting‐condensing) enrichment strategy drastically improves the sensitivity for organic contaminants or components, whose signal amplification approaches 459.7 times that of primary solution and 25.9 times that of single...
Spectrum sensing is a fundamental technique of cognitive radio (CR) system to detect the presence of primary user (PU) transmissions in the licensed spectrum. This paper investigates secondary user (SU) selection based cooperative spectrum sensing under exponentially embedded family (EEF) criterion. With an aim to estimate the optimal number of cooperative users who are better fitting for participating...
In cognitive radio networks, a critical issue is to exploit the spectrum holes based on spectrum sensing while avoiding interference to the primary users. However, the reliability of sensing is uncertain. In order to increase the probability to access the channel, cognitive users may report false detection results and become malicious users (MUs), which could significantly degrade the performance...
Collaborative sensing is an available technology to increase access opportunity for unused spectrum and avoid interference to the primary users in cognitive radio networks. Due to the complexity of wireless environment and the primary user's location is unknown, the sensing performance will be affected by many unfavorable factors such as multipath fading, shadowing, and so on. Especially, some secondary...
In recent years, cooperative spectrum sensing (CSS) for cognitive radio networks (CRN) have been widely investigated in various research aspects. With an aim to develop easy-to-implement CSS schemes, this paper proposes two optimal strategies to manipulate the transmit powers of the cooperative secondary users (SU) in the CSS intervals. When the joint channel statistics (CS) of the sensing and reporting...
In this paper we address two cooperative wideband spectrum sensing schemes, namely the maximum eigen-vector based algorithm (Max-EV) and the multiple eigen-vector (Mul-EV) based algorithm. They serve to detect the primary user (PU) signals over multiple frequency subbands in the wideband licensed frequency band (LFB). A fusion centre (FC) is operating to collect the raw sensing observations from the...
In cognitive radio networks, secondary users can cooperate based on their own sensing observations so as to detect the primary user more accurately. However, since of location disadvantage, multipath fading or shadowing, sensing contribution of some secondary users may be untrustworthy, which are termed malfunction nodes in this paper. To mitigate this problem we propose a contribution based cooperative...
In this paper, three optimal linear soft fusion schemes for cooperative sensing are proposed on the basis of corresponding optimality criteria, namely Neyman-Pearson (N-P), deflection coefficient maximization (DCM), and linear quadratic optimization (LQO). Multiple cooperative secondary users (SU) in the cognitive radio (CR) network simply serve as relays to provide space diversity for the fusion...
This paper investigates secondary user clusters based cooperative spectrum sensing. Secondary users in the cognitive radio network are grouped into multiple clusters and the cooperative spectrum sensing is performed on a hierarchical architecture of these user clusters, through two levels of user collaborations. The low level cooperation is carried out within each cluster while the high level one...
This paper proposes an optimal soft fusion scheme for cooperative spectrum sensing in cognitive radio (CR) network. Multiple cooperative secondary users (SUs) simply serve as relay nodes in the network to provide space diversity for spectrum sensing. An optimal soft fusion scheme of the relayed sensing observations is derived in Neyman-Pearson framework, on the basis of maximizing the deflection coefficient...
In cognitive radio networks, secondary users are allowed to access the under-utilized spectrum and opportunistically transmit whenever no primary signals are detected. So these unlicensed users need to monitor spectrum accurately to detect the presence of the licensed users. In this paper, we exploit a cooperative spectrum sensing between two secondary users to improve the detection performance when...
This paper investigates the optimal weighting scheme for cooperative spectrum sensing in cognitive radio networks, under the constraint of equal probabilities of false alarm and miss detection. The derived optimal weights are determined by individual signal-to-noise-ratio (SNR) of each cooperative sensing node. However, to obtain the precise realistic measurement of each node's SNR is somehow impractical...
In cognitive radio networks, secondary users are allowed to access the under-utilized spectrum and opportunistically transmit whenever no primary signals are detected. So these unlicensed users need to monitor spectrum accurately to detect the presence of the licensed users. In this paper, we exploit a cooperative spectrum sensing between two secondary users to improve the detection performance when...
This paper investigates energy detection based wideband spectrum sensing for dynamic spectrum access (DSA) systems. The licensed frequency band of interest is resolved into a series of contiguous frequency bins via the FFT engine of the detector. By employing forward consecutive mean excision (FCME) algorithm and exploiting primary user (PU) signal's contiguity in frequency domain, computationally...
A novel subband adaptive array antenna for wideband beamforming with GPFB has been proposed. Simulations showed that the proposed subband beamformer is able to suppress interferences more efficiently. Moreover, faster convergence speed of weights is also gained, the reconstructed output mean square error is almost the same as fullband adaptive array's.
In cognitive radio networks, secondary users are allowed to access the under-utilized spectrum and opportunistically transmit whenever no primary signals are detected. So these unlicensed users need to monitor spectrum accurately to detect the presence of the licensed users. In this paper, we exploit a cooperative spectrum sensing between two secondary users to improve the detection performance when...
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