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In a cognitive radio (CR) sensor network, more than one node may sense the same channel simultaneously. If the channel is available, those nodes may start to transmit data in this channel concurrently due to no coordination between them. This may lead to collision and data transmission failure. Thus, energy consumed in channel sensing and data transmission will be wasted. Hence, to achieve the maximum throughput with limited energy, in this paper, we propose a probability-based spectrum sensing scheduling method to enable nodes to determine the optimal sensing time. Each node senses the channels with a probability which is determined by the numbers of channels and nodes. Also, a channel is sensed with a probability which is determined by the number of available channels. This is different from a conventional sensing scheduling with which a node senses channels per request without considering the number of channels and competitive counterparts. First, the probabilities of different cases of node sensing channels are investigated. Then the average throughput achievable, energy consumed, and packet delay are derived. Incorporating the probabilities of the channel being available, detection and false alarm, an optimization problem is formulated to find the optimal sensing time that maximizes the throughput-to-energy ratio. [ABSTRACT FROM AUTHOR]

In this paper, first, two methods of positioning an indoor receiver with transferred global navigation satellite system signals from cellular base stations are proposed. Then, a technique of fusing the position results produced by the two methods through Kalman filter is introduced; thus, the positioning accuracy is improved. To mitigate the near–far problem generated by signals from base stations and satellites, a pulse shaping scheme and the strategy of assigning pulse patterns to base stations are investigated. [ABSTRACT FROM AUTHOR]

Global positioning system (GPS) based indoor positioning techniques generally utilize repeaters to amplify and retransmit the original GPS signals to indoor receivers. In this paper, a GPS repeater based indoor positioning approach is proposed. Unlike most repeater-based indoor positioning techniques in current literature, repeaters are not required to connect to an outdoor antenna with fixed length cables. Neither do repeaters need to be synchronized. Each repeater retransmits the GPS signals continuously to the indoor receivers without sequential switching. Assume more than one satellite is visible to four or more repeaters. At a measuring time instance, the range from a repeater to the user receiver is identical for any travelling satellite signal, which is repeated by this repeater. Incorporating this feature and comparing the ranges measured by means of repeated signals of different satellites, the receiver is able to identify the repeater, which repeats a given satellite signal. With the known coordinates of the identified repeaters and the ranges from repeaters to the receiver, then the receiver position can be found. To compromise the impact of the repeater signal processing time difference on positioning accuracy, this work proposes two methods to calculate the receiver position and fuses the results by Kalman filter. Furthermore, considering the general indoor positioning environments, altitudes of floors of a building are utilized to assist in improving the positioning performance. Simulation results with true repeater coordinate data are provided to verify the proposed approach. [ABSTRACT FROM AUTHOR]

Value of computed tomography (CT) and magnetic resonance imaging (MRI) in the diagnosis of small hepatocellular carcinoma (HCC), and in analysis of the prognostic factors of primary hepatocellular carcinoma (PHC) were compared. A total of 300 patients with PHC were selected from January 2013 to January 2016. Among them, 170 patients were diagnosed with small HCC. Patients were diagnosed by MRI and CT scans, respectively, and diagnostic efficacy of the methods was compared. A single factor and multivariate analysis of prognostic factors were performed on 300 patients. The sensitivity of MRI screening was 78.82%, specificity was 78.46%, accuracy was 78.67%, positive predictive value was 82.72%, and negative predictive value was 73.91%. CT screening showed a sensitivity of 62.35%, a specificity of 73.85%, an accuracy of 67.33%, a positive predictive value of 75.71%, and a negative predictive value of 60.00%. Differences in sensitivity, accuracy, and negative predictive value between MRI and CT screening were statistically significant (P<0.05). There was no statistically significant difference between two groups in specificity and positive predictive value (P>0.05). Diagnostic efficiency of MRI is better than that of CT diagnosis. Univariate analysis showed that age, hepatitis B cirrhosis background, tumor stage, and portal vein embolization were prognostic factors for PHC. Cox multivariate regression analysis showed that the background of liver cirrhosis, tumor stage, and portal thrombosis were independent risk factors for poor prognosis for PHC patient and the differences were statistically significant (P<0.05). MRI is superior to CT in the sensitivity, specificity and accuracy of the diagnosis of small HCC. Individualized comprehensive treatment plans based on the patient's condition may be effective in prolonging the patient's survival time. Imaging diagnosis can provide survival basis for patients, improve diagnostic accuracy, and help to improve the survival rate. [ABSTRACT FROM AUTHOR]

To form cognitive radio nodes into a wireless ad‐hoc network, generally, globally or locally common channels are assumed to be available or some channels are dynamically selected as locally common ones. However, a cognitive radio node is not licensed to any channel for communication. With dynamic channel availability, neither locally nor globally common channels could be assumed available. Therefore, in this study, a new approach for cognitive radio network formation is presented that is not constrained by the availability of common channels. The proposed approach is based on the 'group' concept. Activated cognitive radio nodes form multiple 'groups' according to some criteria. Each group consists of a head node, some gateway nodes and ordinary nodes. During sensing phase, nodes sense channels and negotiate the channel and time slot assignment; thus, during data transmitting phase, each node is able to communicate with its different neighbour nodes in assigned channels during given time slots. Hence, nodes can be connected together to form a network without common channels and the network connectivity is improved. This study presents the network forming process including neighbour node detection, node communication, group formation, time slot assignment, channel assignment and medium access control protocol. Finally, simulations are conducted to investigate the network connectivity. [ABSTRACT FROM AUTHOR]