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Primary User Emulation (PUE) attack is one of the major concerns and problems in cognitive radio networks. Essentially, an intruder who tries to interfere and occupy the vacant spectrum of the primary user (PU) can emulate or impersonate the primary user by mimicking certain characteristics and features of the primary user signal. As a direct result, it may seem to secondary users (SUs) as though...
In this paper we consider the cognitive radio system based on spectrum sensing, and propose an error correction technique for its performance improvement. We analyze secondary user link based on Orthogonal Frequency-Division Multiplexing (OFDM), realized by using Universal Software Radio Peripheral N210 platforms. Parameters of low density parity check codes and interleaver that provide significant...
Current wireless networks are characterized by a static spectrum allocation policy, where governmental agencies assign wireless spectrum to license holders on a long term basis for large geographical regions. Because of the increase in spectrum demand, this policy faces spectrum scarcity in particular spectrum bands. As a result, a significant amount of spectrum is underutilized. Hence, dynamic spectrum...
Spectrum, environment and location awareness capabilities play a vital role in the autonomous and adaptive characteristics of cognitive radio. Knowledge of a cognitive radio (CR) user's location and type of environment may enhance optimisation of dynamic spectrum management and channel allocation. In this paper, a method for determining the near future location of a secondary user (SU) in a CR network,...
Accurate information regarding a cognitive radio user's location and environment can enhance the adaptive and spectral awareness capabilities of cognitive radio systems. In this paper, a single-path multiband Time-of-Arrival (TOA) positioning technique for cognitive radio is proposed and the performance evaluated using maximum-likelihood (ML) location estimation for a typical rural scenario where...
Cognitive radios (CR) are an efficient approach to deploy a secondary network in the vacant portions of the spectrum licensed to primary networks. However, when primary users return to a channel used by a CR, the later should vacate the channel and start a restoration process by searching and sensing other channels. The restoration process objective is to find the best channel in the shortest time...
Cognitive radio is an emerging technology for sensing and dynamic access of spectrum in mobile radio environments. It aims at dynamically allocating unused bandwidth among secondary users without causing harmful interference to the primary users. This approach, which has clear economical benefits, has recently attracted significant research effort. In this paper, we propose a new approach to dynamic...
In Orthogonal Frequency Division Multiple Access (OFDMA) based Cognitive Radio (CR) systems, optimal power loading schemes are devised such that the transmission rate is maximized while maintaining interference from Secondary Users (SUs) to Primary Users (PUs) below a specified threshold. The power loading algorithms however do not distinguish between data and pilot symbols. A similar situation exists...
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 coherent multiple access channel (MAC) serving as an alternative way to improve the cooperative spectrum sensing performance. We assume that the gains of the observations and transmission channels are all known which is available since we use standard...
Spectrum under-utilization calls for the open and dynamic spectrum access mechanism, which allows the unlicensed user equipped with cognitive radios to opportunistically sense and access the spectrum that not occupied by primary users. In practice due to the hardware limitations, each cognitive radio user may be only able to sense a portion of the interested wide span spectrum. Hence, a hardware-constrained...
Radios for public safety communication have some of the most stringent requirements for access, reliability and robustness. While wireless technology has seen tremendous strides in the past decade, large parts of the public safety infrastructure have unfortunately lagged behind. Today the majority of the Land Mobile Radios (LMR) used by police and fire departments, among others, utilize bandwidth...
Existing research in transport protocols for wireless ad-hoc networks has focused on reliable end-to-end packet delivery under uncertain channel conditions, route failures due to node mobility and link congestion. In a cognitive radio (CR) environment, there are several key challenges that must be addressed apart from the above concerns. The intermittent spectrum sensing undertaken by the CR users,...
Dynamic spectrum access (DSA) is an emerging notion in cognitive radio, aiming to improve the spectrum usage with reliable secondary access to the spectral resources. The main challenge in DSA is the detection of spectral opportunities and their efficient utilization without causing interference to the primary users. For this goal, we propose to make use of a reinforcement learning approach: the Multi...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
We propose a novel distributed cross-layer optimization approach for cognitive radio wireless networks. A cognitive radio is a wireless device that is capable of sensing the prevailing environmental conditions and automatically adapting its operating parameters in order to enhance the performance of both the system and potentially the whole network. Given the lack of a centralized intelligence to...
Wireless communication services have been increasing rapidly and this progress has caused a shortage in frequency resources. Cognitive radio technology is expected to enable frequency resources to be used more efficiently. When several wireless communication systems simultaneously use cognitive radio technology, the priority level of each system for frequency use is set and the frequency resource...
In this paper, we propose a cognitive radio-based multi-user resource allocation framework for mobile ad hoc networks using multi-carrier DS CDMA modulation over a frequency-selective fading channel. In particular, given pre-existing communications in the spectrum where the system is operating, in addition to potential narrow-band interference, a channel sensing and estimation mechanism is provided...
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