Cluster-based cooperative subcarrier sensing using antenna diversity-based weighted data fusion

Cooperative spectrum sensing (CSS) is used in cognitive radio (CR) networks to improve the spectrum sensing performance in shadow fading environments. Moreover, clustering in CR networks is used to reduce reporting time and bandwidth overhead during CSS. Thus, cluster-based cooperative spectrum sensing (CBCSS) has manifested satisfactory spectrum sensing results in harsh environments under processing constraints. On the other hand, the antenna diversity of multiple input multiple output CR systems can be exploited to further improve the spectrum sensing performance. This paper presents the CBCSS performance in a CR network which is comprised of single- as well as multiple-antenna CR systems. We give theoretical analysis of CBCSS for orthogonal frequency division multiplexing signal sensing and propose a novel fusion scheme at the fusion center which takes into account the receiver antenna diversity of the CRs present in the network. We introduce the concept of weighted data fusion in which the sensing results of different CRs are weighted proportional to the number of receiving antennas they are equipped with. Thus, the receiver diversity is used to the advantage of improving spectrum sensing performance in a CR cluster. Simulation results show that the proposed scheme outperforms the conventional CBCSS scheme

Peak to average power ratio reduction in NC–OFDM systems

Non contiguous orthogonal frequency division multiplexing (NC-OFDM) is an efficient and adaptable multicarrier modulation scheme to be used in cognitive radio communications. However like OFDM, NC-OFDM also suffers from the main drawback of high peak to average power ratio (PAPR). In this paper PAPR has been reduced by employing three different trigonometric transforms. Discrete cosine transform (DCT), discrete sine transform (DST) and fractional fourier transform (FRFT) has been combined with conventional selected level mapping (SLM) technique to reduce the PAPR of both OFDM and NC-OFDM based systems. The method combines all the transforms with SLM in different ways. Transforms DCT, DST and FRFT have been applied before the SLM block or inside the SLM block before IFFT. Simulation results show the comparative analysis of all the transforms using SLM in case of both OFDM and NC-OFDM based systems

Cooperative subcarrier sensing using antenna diversity based weighted virtual sub clustering

The idea of cooperation and the clustering amongst cognitive radios (CRs) has recently been focus of attention of research community, owing to its potential to improve performance of spectrum sensing (SS) schemes. This focus has led to the paradigm of cluster based cooperative spectrum sensing (CBCSS). In perspective of high date rate 4th generation wireless systems, which are characterized by orthogonal frequency division multiplexing (OFDM) and spatial diversity, there is a need to devise effective SS strategies. A novel CBCSS scheme is proposed for OFDM subcarrier detection in order to enable the non-contiguous OFDM (NC-OFDM) at the physical layer of CRs for efficient utilization of spectrum holes. Proposed scheme is based on the energy detection in MIMO CR network, using equal gain combiner as diversity combining technique, hard combining (AND, OR and Majority) rule as data fusion technique and antenna diversity based weighted clustering as virtual sub clustering algorithm. Results of proposed CBCSS are compared with conventional CBCSS scheme for AND, OR and Majority data fusion rules. Moreover the effects of antenna diversity, cooperation and cooperating clusters are also discussed

Peak to average power ratio based spatial spectrum sensing for cognitive radio systems

The recent convergence of wireless standards for incorporation of spatial dimension in wireless systems has made spatial spectrum sensing based on Peak to Average Power Ratio (PAPR) of the received signal, a promising approach. This added dimension is principally exploited for stream multiplexing, user multiplexing and spatial diversity. Considering such a wireless environment for primary users, we propose an algorithm for spectrum sensing by secondary users which are also equipped with multiple antennas. The proposed spatial spectrum sensing algorithm is based on the PAPR of the spatially received signals. Simulation results show the improved performance once the information regarding spatial diversity of the primary users is incorporated in the proposed algorithm. Moreover, through simulations a better performance is achieved by using different diversity schemes and different parameters like sensing time and scanning interval

Bayesian compressive sensing framework for spectrum reconstruction in Rayleigh fading channels

Compressive sensing (CS) is a novel digital signal processing technique that has found great interest in many applications including communication theory and wireless communications. In wireless communications, CS is particularly suitable for its application in the area of spectrum sensing for cognitive radios, where the complete spectrum under observation, with many spectral holes, can be modeled as a sparse wide-band signal in the frequency domain. Considering the initial works performed to exploit the benefits of Bayesian CS in spectrum sensing, the fading characteristic of wireless communications has not been considered yet to a great extent, although it is an inherent feature for all sorts of wireless communications and it must be considered for the design of any practically viable wireless system. In this paper, we extend the Bayesian CS framework for the recovery of a sparse signal, whose nonzero coefficients follow a Rayleigh distribution. It is then demonstrated via simulations that mean square error significantly improves when appropriate prior distribution is used for the faded signal coefficients and thus, in turns, the spectrum reconstruction improves. Different parameters of the system model, e.g., sparsity level and number of measurements, are then varied to show the consistency of the results for different cases

Surveillance on the Sucking Insect Pests and their Natural Enemies on Tomato Crop

The experiment was conducted at the experimental area of Sindh Agriculture University Tandojam during 2013. The Roma variety was cultivated for this purpose, the all agronomic practices were carried out accordingly. The temperature 15-24ºC and relative humidity 45-68% was recorded during research work. The results of the present experiment showed that sucking insect pests as well as natural enemies’ population was observed through out cropping season from 1st week of March to 1st week of May 2013. The results reveled that the maximum population of whitefly (5.5±0.16/leaf) was recorded followed by jassid (4.7±0.21/leaf), aphid (4.4±0.37/leaf) and thrip (2.9±0.17/leaf) on tomato crop. However, the maximum population chrysoperla carniea (1.2±0.16/plant) was recorded followed by spider (2.6±0.23/plant) and lady bird beetle (2.5±0.22/plant) was recorded on tomato crop. The results further reveled that the over all impact of relative humidity on the most of the insect pests showed negative correlation. However, the temperature showed that over all positive impact of all the insect pests and predators except whitefly and spider. Key Word: Solanum lycopersicum, Surveillance, sucking insect pest, Predator

Efficacy of Neem Kernal Powder and Neem Oil against Helicoverpa Armigera on Sunflower Crop

A field study was carried out during 2013 at the experimental area of Sindh Agriculture University Tandojam during, in RCBD to exmine the efficacy of neem kernal powder, neem oil and Radaint against Helicoverpa armigera on sunflower crop. Four treatments with T1=Neem kernel powder, T2=Neem oil, T3=Radiant and control (Untreated). Variety HO-1 was sown on 1st March 2013. The experiment replicated three times. The results reveled that biopesticides and synthetic pesticides were sprayed against H. armigera on the sunflower crop. The plots treated with radiant showed heighest efficacy (52.60%), followed by the plots treated with Neem seed kernel extract (31.32%) and the plots treated with Neem oil (30.14%) was recorded after 1st spray on sunflower crop. In the second spray the plots treated with radiant also showed heighest efficacy (57.30%), followed by the plots treated with Neem seed kernel extract (33.34%) and plots treated with neem oil (32.27%) was recorded on sunflower crop. However, in 3rd spray the heighest efficacy was recorded in the plots treated with radiant (50.48%), followed by the plots treated with Neem extracts (40.39%) and plots treated with neem oil (36.40%) was recorded. While, in fourth spray, the heighest efficacy was recorded the plots treated with Neem extracts (42.60%), followed by the plots treated with Neem oil (31.40%) and plots treated with Radaint (39.40%) was recorded on sunflower crop. The overall results showed that the biopesticids reduced H. armigera population progressively, as compared to synthetic pesticides. Keywords: Sunflower, Helicoverpa armigera and Neem Product

Efficacy of Insecticides on Rice Crop Against Rice Leaf Folder, Cnaphalocrocis Medinalis Guen. (Pyralidae: Lepidoptera)

A field study was carried out during 2010 at experimental area Sindh Agriculture University Tandojam in RCBD to examine the reduction percentage in the population of C. medinalis on rice crop with three insecticides viz; Deltophos, Tracer, Thioluxan and impact of these insecticides was composed with control plot (untreated). The data showed the maximum reduction (76.19%) in the population of C.medinalis was recorded in the plots treated with Deltaphos followed by Tracer (65.93%) and Thioluxan (46.92%) after 1st spray on rice crop. In the second spray maximum reduction (71.08%) was also recorded in the plots treated with Deltaphos followed by Tracer (57.40%) and Thioluxan (30.15%). Similarly, after 3rd spray the maximum reduction (78.99%) was recorded in the plots treated with Deltaphos followed by Thioluxan (55.88%) and Tracer (54.34%) on rice crop. While, in fourth spray, the maximum reduction (71.92%) was recorded in plots treated with Deltaphos followed by Tracer (39.36%) and Thioluxan (14.36%) on rice crop. The results further indicated that the maximum yield (4783.00kg/ha?1) was recorded in plots treated with Deltophos followed by Tracer (4486.46kg/ha ?1) and  Thioluxan (4033.66kg/ha?1) as compared control (3066.50kg/ ha?1).Highly significantly (P < 0.01) difference in the efficacy of insecticides was recorded during all sprays carried out in cropping season of rice crop. Key word: Oryza sativa, Cnaphalocrocis medinalis. Management and Insecticides

To Head CT Scan or Not: The Clinical Quandary in Suspected Subarachnoid Hemorrhage; a Validation Study on Ottawa Subarachnoid Hemorrhage Rule

Introduction: The Ottawa Subarachnoid Hemorrhage rule (OSR) is a clinical decision tool identified for ruling out subarachnoid hemorrhage (SAH) in those patient above 15 years of age who present to the emergency department (ED) with acute onset atraumatic headache. Objective: The primary objective of this study was to externally validate the OSR in a single national health service (NHS) setting in the UK and secondly, to compare it with our current practice without using a decision rule. Method: A retrospective review of computerized medical records was done for all patients registered with headaches from January to December 2016. The data were manually charted on a data sheet from individual patient records. Patients fulfilling the preset inclusion and exclusion criteria as per the OSR were enrolled in the analysis. According to the OSR, if patient had any of the 6 criteria enlisted (age > 40 years, neck stiffness/pain, witnessed loss of consciousness, onset during exertion, thunderclap headache, limited neck flexion on examination), further diagnostic decision was required. All patients were followed up for 6 months on the computer system as it gets highlighted if the patient is represented again to the ED or is deceased. Results: A total of 737 ED visits with acute headache were reviewed for potential eligibility. Out of these, 649 were estimated to be eligible. On excluding 485 patients that could not meet the predetermined inclusion criteria and 19 patients as per the exclusion criteria, 145 (19.7%) patients were included in the analysis. There were 5 cases of SAH, yielding an incidence of 3.4 % (95% CI 1.3 % – 8.3 %). The sensitivity for SAH was 100% (95% CI, 46.3 % - 100 %); specificity of 44.2 % (95% CI, 36 % - 53 %); positive predictive value of 6.02 % (95% CI 2.2 % - 14.1 %); and negative predictive value of 100% (95% CI, 92.7 % - 100%). Conclusion: Although being poorly specific, the OSR is a highly sensitive, simple tool for ruling out SAH in alert patients with a headache in ED settings

To Head CT Scan or Not: The Clinical Quandary in Suspected Subarachnoid Hemorrhage; a Validation Study on Ottawa Subarachnoid Hemorrhage Rule

Introduction: The Ottawa Subarachnoid Hemorrhage rule (OSR) is a clinical decision tool identified for ruling out subarachnoid hemorrhage (SAH) in those patient above 15 years of age who present to the emergency department (ED) with acute onset atraumatic headache. Objective: The primary objective of this study was to externally validate the OSR in a single national health service (NHS) setting in the UK and secondly, to compare it with our current practice without using a decision rule. Method: A retrospective review of computerized medical records was done for all patients registered with headaches from January to December 2016. The data were manually charted on a data sheet from individual patient records. Patients fulfilling the preset inclusion and exclusion criteria as per the OSR were enrolled in the analysis. According to the OSR, if patient had any of the 6 criteria enlisted (age > 40 years, neck stiffness/pain, witnessed loss of consciousness, onset during exertion, thunderclap headache, limited neck flexion on examination), further diagnostic decision was required. All patients were followed up for 6 months on the computer system as it gets highlighted if the patient is represented again to the ED or is deceased. Results: A total of 737 ED visits with acute headache were reviewed for potential eligibility. Out of these, 649 were estimated to be eligible. On excluding 485 patients that could not meet the predetermined inclusion criteria and 19 patients as per the exclusion criteria, 145 (19.7%) patients were included in the analysis. There were 5 cases of SAH, yielding an incidence of 3.4 % (95% CI 1.3 % – 8.3 %). The sensitivity for SAH was 100% (95% CI, 46.3 % - 100 %); specificity of 44.2 % (95% CI, 36 % - 53 %); positive predictive value of 6.02 % (95% CI 2.2 % - 14.1 %); and negative predictive value of 100% (95% CI, 92.7 % - 100%). Conclusion: Although being poorly specific, the OSR is a highly sensitive, simple tool for ruling out SAH in alert patients with a headache in ED settings