Optimal Number Of Secondary Users Research Articles

Adaptive Multicriteria Thresholding for Cooperative Spectrum Sensing in Cognitive Radio Ad Hoc Smart Grid Networks under Shadowing Effect

Cognitive radio is expected to be implemented in smart grids since it presents high reliability, high accuracy and low transmission time by utilizing licensed bands opportunistically. Shadowing environment affects the performance of channel availability detection of local spectrum sensing since it occurs occasionally. Therefore, the cooperative spectrum sensing is encouraged to be used for addressing shadowing issues. The principle cooperative spectrum sensing techniques suffer from unreliable local information from secondary users (SUs) who are encountered by the shadowing effect. Then, several alternative methods, adaptive majority rule and improved weight algorithm (IMA) is proposed by taking the SUs reliability into account. However, the unreliable SUs are still considered according to the algorithm. Therefore, in this paper, we propose an adaptive multi-criteria thresholding (AMT) to determine the channel availability according to the SUs reliability. The main contribution of AMT is three-fold. First, the new reliable weight calculation is proposed by utilizing analytic hierarchy process (AHP) under three major criteria. Second, AMT is flexible to the number of SUs since it adapts the decision weight on the optimal number of SUs according to the reliable SUs. Third, the shadowing issue is addressed by taking only reliable SUs into account.

Optimization of cooperative secondary users in cognitive radio networks

In this paper, we identified the optimal number of secondary users in a cooperative spectrum sensing by maximizing the energy efficiency. We obtain the mathematical expressions and simulation results for the optimal number of secondary users using OR and AND fusion rules. We conducted the simulation for both OR and AND rules in two categories, One by keeping signal to noise ratio constant and second by keeping the detection threshold constant. Based on the analysis we showed that the performance obtained for OR rule is better than the AND rule. We hope that our results will be useful for improving the energy efficiency in identifying the un-utilized spectrum.

Throughput analysis in proposed cooperative spectrum sensing network with an improved energy detector scheme over Rayleigh fading channel

In this paper, we have proposed the cooperative spectrum sensing network in which each CR is equipped with multiple antennas and an improved energy detector (IED) technique is considered as detection scheme. The CRs utilize the selection combining (SC) technique based on the decision statistics obtained by an IED with multiple antennas in-order to make binary decisions about the primary user (PU). The analysis of average channel throughput and network utility function (NUF) is performed for the proposed CSS system with multiple antennas at each CR using an IED scheme over Rayleigh fading channel. The performance is analyzed using different fusion rules (k=1+n and k=M−n) at fusion center, where k is the number of selected CRs, M is the total number of CRs, and n is a positive integer (n=2). The error rate is considered in reporting channel (R-channel) to show the effect of an error rate on the channel throughput and NUF. Performance of error free and error present R-channel is compared using MATLAB simulations. The impact of several network parameters like detection threshold (λ), multiple antennas at each CR (Z), the number of secondary users (M), and the error rate in R-channel on the performance of throughput and NUF are shown using the simulation results. The optimal number of secondary users are calculated to maximize the average channel throughput for various fusion rules.

Fast Cooperative Energy Detection under Accuracy Constraints in Cognitive Radio Networks

Cooperative energy detection (CED) is a key technique to identify the spectrum holes in cognitive radio networks. Previous study on this technique mainly aims at improving the detection accuracy, while paying little attention to the performance of detection time. This paper concentrates on the issue of fast CED, which is achieved by minimizing its detection time subject to the constraints on detection accuracy. Firstly, the prevalent counting rule based CED algorithm is optimized. Taking the special cases of counting rule (AND rule and OR rule), for example, we show that detection time can be minimized by selecting an optimal number of secondary users. Moreover, we prove that OR rule is superior to AND rule in detection time, and thus OR rule based CED is faster than AND rule based CED. Then, a sequential test (ST) based CED algorithm is proposed to exploit the benefit of ST and detect primary user even faster. After analyzing its detection time, we illustrate that ST based CED is able to spend the minimal detection time in satisfying the accuracy constraints by choosing an optimal sample number. Simulation results are provided to verify the effectiveness of both fast algorithms discussed in this paper.

Advanced Energy Detector Based Cooperative Spectrum Sensing In Cognitive Networks

Cognitive radio is a befitting hopeful technology for future. Spectrum sensing is the most critical function of cognitive radio. Most of the spectrums sensing processes proposed earlier become impractical at lower signal to noise ratio conditions. Paper presents advanced cooperative spectrum sensing technique used in cognitive radio (CR) systems. By spectrum sensing it detects the presence of a primary user (PU) on a concerned spectrum. The accuracy of spectrum sensing depends on both sensing time and number of sensing nodes (secondary users) participating in the sensing process. We derive the optimal number of secondary users for cooperative spectrum sensing based on adaptive threshold energy detection to minimize spectrum detection error in conventional as well as improved energy detector.

Throughput Analysis for a Dynamic Spectrum Sharing Model with Finite Primary Users and Infinite Secondary Users

In this paper we present throughput analysis for a dynamic spectrum-sharing model. We assume that number of primary users allocated to a channel is fixed all the time. But the number of primary users is different for different channels. Primary users allocated to a specific channel compete to access the channel and the secondary users or cognitive users sense the channel whether the channel is free or not. The transmission probabilities of primary and secondary users are different. The packet transmission delay of secondary users is considered in this paper. Our objective is to find the optimal number of secondary users to maximize the total throughput of primary and secondary users.

Non-coherent Power Decomposition-Based Energy Detection for Cooperative Spectrum Sensing in Cognitive Radio Networks

As the fundamental component of dynamic spectrum access, implementing spectrum sensing is one of the most important goals in cognitive radio networks due to its key functions of protecting licensed primary users from harmful interference and identifying spectrum holes for the improvement of spectrum utilization. However, its performance is generally compromised by the interference from adjacent primary channels. To cope with such interference and improve detection performance, this paper proposes a non-coherent power decomposition-based energy detection method for cooperative spectrum sensing. Due to its use of power decomposition, interference cancellation can be applied in energy detection. The proposed power decomposition does not require any prior knowledge of the primary signals. The power detection with its interference cancellation can be implemented indirectly by solving a non-homogeneous linear equation set with a coefficient matrix that involves only the distances between primary transmitters and cognitive secondary users (SUs). The optimal number of SUs for sensing a single channel and the number of channels that can be sensed simultaneously are also derived. The simulation results show that the proposed method is able to cope with the expected interference variation and achieve higher probability of detection and lower probability of false alarm than the conventional method in both hard combining and soft combining scenarios.

Cooperative TV spectrum sensing in cognitive radio for Wi-Fi networks

This paper presents cooperative spectrum sensing techniques for cognitive radio (CR) systems. The spectrum sensing detects the presence of a primary user (service) on an associated spectrum. The accuracy of spectrum sensing depends on both sensing time and number of sensing nodes (i.e. secondary users) participating in the sensing process. We derive optimal number of secondary users for cooperative spectrum sensing to minimize spectrum detection error probability and optimal spectrum sensing time to maximize data transmission throughput. A system model which consists of a primary TV spectrum and multiple Wi-Fi secondary users is considered. The proposed CR scheme can solve recent spectrum shortage problem in Wi-Fi networks due to traffic explosion by smart phones. We propose K-out-of-N-rule which is the most efficient cooperative sensing rule by analytical and numerical results.

Throughput Maximization Problem in a Cognitive Radio Network

Throughput maximization problem is considered in this paper. Here, throughput analysis is done for fixed allocation of channels. Fixed allocation of channels means number of primary users allocated to a channel is considered to be fixed but the number of users is different for different channels. Primary users allocated to a specific channel compete to access the channel and the cognitive users sense the channel whether the channel is free or not. The transmission probabilities of primary and secondary users are different. In this paper we consider the delay related to channel access of secondary users. We consider number of secondary users is very large. Our objective is to find the optimal number of secondary users to maximize the total throughput of primary and secondary users.