Cooperative sensing under limited band control channel in cognitive radio networks

In the context of cognitive radio the cooperative spectrum sensing has been proposed to overcome the problem associated with the local sensing for example the hidden node problem due to noise uncertainty, fading, and shadowing. However, sensing results reporting requires perfect channel to avoid the performance degradation. It also requires a large bandwidth under the hypothesis of large number of cognitive users. This paper presents a hard decision auto-correction reporting scheme that is able to correct the error in the reported bit directly. This system further minimizes the average number of the reporting bits by allowing only the user with detection information (binary decision 1) to report its result. The sensing performance is investigated and the numerical results show significant decrease in reporting bits without affecting the sensing performance

Cognitive radio technology for flexible spectrum sharing

Recent study by FCC Spectrum-Policy Task Force (SPTF) found that while the available spectrum becomes increasingly scarce, the assigned spectrum is significantly underutilized. Cognitive radio (CR) technology refers to a new type of radio hat uses real-time interaction with its environment to determine transmitter parameters such as frequency, power, and modulation. This paper presents a preliminary survey of CR with the goal of quantifying spectral occupancy and thereby gaining some insight into its feasibility. Two case studies were investigated: ultra-wide bandwidth technology as a transmission technique suitable for implementing a cognitive radio system was discussed, and a comparable measurement of TV spectrum band in an urban environment is also presented

Enhanced distributed cooperative spectrum sensing for cognitive radio networks

Cognitive radio will gain acceptance only when the primary detection model is accurate to insure no interference to primary system. Cooperative sensing for primary detection is degraded by the reliability of local node sensing in high fading environments. Further, managing the control channel and fusion node is problematic aspect. For instance, to ensure the local sensing is reported correctly to fusion centre requires very low bit error rate (BER) channel. Another issue, that reporting channel needs large bandwidth to carry the reporting traffics. In order to improve the sensing performance and reduce the reporting error, a distributed architecture for processing and fusion of sensing information is considered. This thesis proposes an adaptive and distributed detection threshold based on maintained probability of false alarm to increase reliability of sensing under Rayleigh fading channel. The link quality status of the sensing channel of the candidate nodes is used to determine the detection threshold dynamically and the reporting link status is used for dynamic selection of fusion node for the distributed cooperative sensing. Furthermore a dynamic TDMA MAC is proposed for media access and information exchange where the noise estimation is also used for the nodes reporting scheduling; this method increases the sensing time for the later scheduled cognitive radios. The proposed distributed scheme shows a significant improvement in the overall detection readability. The probability of detection, and bit error rate (BER) were used as performance metrics in the analytical and simulation results to validate the proposed method over the direct cooperation and non-cooperative sensing. Also analytical formulation with possible candidate selection criteria is used to investigate and optimize the distributed cooperation gain. The results show that by employing such distribution and selection technique, the reporting error due to the fading channel is reduced up to 42% based on number of candidate nodes. Results also shown that the method significantly improved the sensing performance by increase the probability of detection up to 0.9 at <0.1 probability of false alarm. Sensitivity requirement is reduced dramatically by more than 95% with varying number of nodes and probability of detection. Receiver operation characteristic (ROC) curve with the parameters and performance achieved verified that the probability of detection Pd can be improved significantly while maintaining probability of false alarm <0.1

Cooperative sensing in cognitive radio networks-avoid non-perfect reporting channel

Problem statement: Cognitive radio is a candidate technology for more efficient spectrum utilization systems based on opportunistic spectrum sharing. However, a common assumption regarding cognitive radios is that they are unlicensed spectrum users that should defer to (avoid interfering with) existing primary sources. Therefore effective sensing of primary users was a major focus of current research. Cooperative spectrum sensing had been proposed to overcome the problem associated with the local sensing node problem-due to noise uncertainty, fading and shadowing. However, reporting the sensing result required perfect channel to avoid degradation in sensing performance due to fading. It also required a large bandwidth assuming large number of cognitive user. Approach: In this study we presented a hard decision auto-correction reporting scheme that directly corrects the errors in the reported bit and further minimizes the average number of reporting bits by allowing only the user with a detection information to report its result. We used analytical formulation to investigate the reporting scheme, by employing such selection technique; the reporting error due to the fading channel was reduced. Results: The sensing performance was investigated and we showed through simulations and probabilistic analysis the sensing performance improvements achieved via the proposed method. Numerical result showed much decrease in reporting bit without affecting the sensing performance

Efficient Energy Mechanism in Heterogeneous WSNs for Underground Mining Monitoring Applications

Wireless Sensor Networks (WSNs) play an important role in underground mining applications. In particular, they help to collect information using sensors and provide monitoring of complex mine environments to avoid potential risks and manage operations. Despite the importance of WSNs, they face the problem of energy consumption and the difficulty of replacing the batteries of the sensor nodes. The distributed energy-efficient aggregation protocol (DEECP) helps to reduce the power consumption of the WSN. This protocol enables an increase in the lifetime of a WSN. The DEECP algorithm uses the clustering concept and selects cluster heads (CHs) according to the election probability based on the ratio between the residual energy and network average energy of each node. However, this method does not provide an optimum solution because it does not take into account the different sensor energy levels. In addition, the algorithm does not consider the effect of the distance between the base station and sensor node likely be chosen to become a CH. This can significantly affect the performance of the WSN. This paper proposes an optimization threshold for CH selection based on three energy levels of a sensor, namely, low, high, and super as well as the measurement of the distances between base stations and possible nodes to be selected as CHs to optimize the CH selection method. The proposed approach is evaluated and compared with DEECP in terms of dead nodes, alive nodes, and network throughput. The results show that the proposed approach outperforms DEECPs in terms of network stability and lifetime