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Frequency spectrum scarcity has been a strong research motivation. Those researches have focused on developing methodologies to utilize frequency spectrum as much as it could be. Meanwhile, this spectrum utilization and its great revenue should not affect the quality of services being provided by network providers. In most cases, statistics have shown that only quarter of the spectrum is well utilized...
Spectrum sensing is used to detect spectrum holes and find active primary users, while randomly selecting channel for sensing leads to secondary user's lower throughput in high traffic cognitive radio networks. Spectrum prediction forecasts future channel states on the basis of historical information. A new frame structure is proposed in this paper for the imperfect spectrum prediction, improving...
In the current literature on cognitive radio, it is commonly assumed that fixed time durations are assigned for spectrum sensing and data transmission. It is however possible to improve the performance by finding the best tradeoff between sensing time and network throughput. In this paper, we formulate the sensing-throughput problem to dynamically assign a number of SUs for cooperatively sensing each...
Cognitive Radio Network (CRN) provides a promising method to expand usage of the underutilized spectrum resources. Spectrum sensing is a key functionality for the operation of secondary overlay CRN systems without causing harmful interference to the licensed primary users. Through the collaboration among spatially distributed CR users, spectrum sensing can provide reliable decisions. However, CRN...
In this article, we develop an analytical framework for performance evaluation and comparison between decision and data fusion rules for cooperative relay based cognitive radio networks. Our unified analytical formulas for the data fusion rules are sufficiently general to tackle generalized stochastic channel models with independent but non-identically distributed (i.n.d) link statistics. We also...
Supporting secondary users through a collateral network dedicated to spectrum sensing has been recently proposed as a mean to overcome spectrum sensing limitations of secondary devices. Building on this idea, we propose a protocol for a Wireless Sensor Network (WSN) to support secondary devices of an Opportunistic Spectrum Access (OSA) network. We examine the fundamental tradeoff between the statistics...
Spectrum sensing is essential for the success of the cognitive radio networks. In traditional spectrum sensing schemes, Secondary Users (SUs) are responsible for the spectrum sensing which could be very time and resource consuming. It leads to a great deal of inefficiency in spectrum usage and introduces many practical challenges. To tackle these challenges and leverage the spectrum opportunity more...
Cooperative spectrum sensing for cognitive radio (CR) networks has been widely studied to increase the reliability of the primary user detection. However, when there are a large number of cooperating CRs, this typically leads to an increase in overhead in sensing reporting as well as in sensing report combining. A large number of CRs participating in cooperative spectrum sensing also increases the...
Power saving and management is a critical aspect of cooperative spectrum sensing in cognitive radio networks, in which a group of secondary cognitive radio nodes share the task of spectrum sensing in order to detect gaps in the spectral bands temporally or spatially not utilized by primary transceivers, facilitating dynamic allocation of physical layer and networking resources that finds application...
In cognitive radio systems, secondary users should continuously sense the licensed spectrum in case a primary user starts to transmit. Whether or not the secondary users can sense the spectrum during the secondary communication is an attractive problem. In this paper, we consider a particular wireless cooperative communication system acting as a secondary system, and demonstrate that by exploiting...
CORAL is a WiFi based wireless terminal building block that can be used to implement cognitive radio networks (CRN). Its cognitive capabilities are created by providing a PHY and MAC control framework around a standard off-the-shelf WiFi router containing multiple radios. In doing this we implement a CRN that has sensing capabilities and is able to control radio emissions in space, time, and by channel...
In this paper, we consider a cognitive radio (CR) system in non-ideal fading wireless channels and propose a cooperative spectrum sensing scheme based on linear parallel access channel (PAC),serving as an alternative way to improve the cooperative spectrum sensing performance. We assume that the gains of the observation and transmission channels are all known which is available since we use standard...
Cognitive Radio (CR) seems to be a promising solution to the radio spectrum congestion problem by opportunistic uses of the spectral holes to achieve efficient use of the frequency resource by allowing the coexistence of licensed (primary) and unlicensed (secondary) users in the same bandwidth. According to the cooperative wireless communication (CWC) concept the active nodes may increase their effective...
This paper focuses on the spectrum sensing issues in the unslotted cognitive radio networks with wireless fading channels. To overcome the energy-inefficiency problem of the existing continuous/fixed-schedule spectrum sensing schemes in the cognitive radio networks, we propose an efficient spectrum sensing scheme for secondary users (SUs). The design goal of our proposed scheme is to save the sensing...
We propose the queue-aware spectrum sensing schemes for interference-constrained opportunistic transmissions of secondary users (SUs) in cognitive radio networks. Specifically, we employ the energy detection for SUs to sense the spectrum-usage status of the primary users (PUs). Unlike the traditional energy detector using a fixed energy threshold to decide the presence of the PUs' signals, we dynamically...
Many earlier works have studied the problem of cooperative spectrum sensing in cognitive radio networks. However, relay selection was not considered which can improve the performance of cooperative communication systems. In this paper, the detection probability and false alarm probability are evaluated when relay selection is executed for cooperative spectrum sensing in cognitive radio networks. The...
Cognitive Radio (CR) has been considered as a promising concept for improving the utilization of limited radio spectrum resources for future wireless communications and mobile computing. As cognitive radio network (CRN) is a general wireless heterogeneous network, it is very essential for detecting the misbehaving or false nodes in the network. So in this paper we propose a trust aware model which...
Detection of spectral white space and the adoption of optimal secondary user transmission policies are the two crucial aspects of a Cognitive Radio system. In this paper we study the problem of optimal utilization of time domain holes in an unsaturated IEEE 802.11 network. We also design a scheme for the coexistence of a secondary system with an IEEE 802.11 network such that it does not affect the...
Spectrum sensing is one of the key enabling technologies in Cognitive Radio Networks (CRNs). In CRNs, secondary users (SUs) are allowed to exploit the spectrum opportunities by sensing and accessing the spectrum, which exhibit many critical limitations in practical environments. In this paper, we propose a new sensing service model that uses dedicated wireless spectrum sensor networks (WSSN) for spectrum...
The speed and accuracy of spectrum sensing techniques are essential factors in the performance of cognitive radio networks. The limitations imposed by computational complexity and limited monitoring time window impede the success of spectrum sensing operation performed by cognitive radio nodes. Compressive sensing technique is viewed as a novel approach to solve scalability problems in some signal...
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