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The current inefficient utilization of frequency spectrum has alerted regulatory bodies to streamline improvements. Cognitive radio (CR) has recently received considerable attention and is widely perceived as a promising improvement tool in estimating, or equivalently sensing, the frequency spectrum for wireless communication systems. The cognitive cycle in CR systems is capable of recognizing and...
Frequency spectrum sensing is a key and challenging task of modern wireless communication systems. Cognitive radio (CR) has recently been envisioned as an intelligent platform capable of achieving better spectrum sensing and, hence, promotes efficient spectrum utilization. The multi-taper method (MTM) is a good candidate to achieve such a requirement. This paper focuses on the application of MTM spectrum...
The automatic modulation classification (AMC) is linked to the accurate identification of a received signal modulation. The AMC represents an important part of cognitive radio (CR) systems recently envisioned to be an appropriate platform to adjust against changing work conditions. The two main distinguished streams of AMC are either by using the likelihood based (LB) statistical tests or featured...
Differential distributed space-time coding (DDSTC) has been proved to be suitable for wireless relay networks, since it can provide spatial diversity without the need for channel state information at neither the transmitter nor the receiver side. However, DDSTC suffers from significant error floor in fast-fading channel conditions with high Doppler frequencies due to rapid time variations. For this...
The automatic classification of digital modulated signals has been subject to extensive studies over the last decade, with numerous scholarly articles and research studies published. This paper provides an insightful guidance and discussion on the most practical approaches of automatic modulation classification (AMC) in cognitive radio (CR) using likelihood based (LB) statistical tests. It also suggests...
This paper presents a new Zero-Crossing Digital Phase-Locked Loop (ZC-DPLL) for frequency synchronization and tracking. The proposed hyperbolic Σ-Δ based ZC-DPLL has an improved time jitter by a factor of 6.4 and an extended lock-in range by a factor of sinh(π)/π. These significant improvements were achieved by introducing a hyperbolic nonlinearity and a modified Σ-Δ blocks to the original ZC-DPLL...
The scarcity of frequency spectrum used for wireless communication systems has attracted a considerable amount of attention in recent years. The cognitive radio (CR) terminology has been widely accepted as a smart platform mainly aimed at the efficient interrogation and utilization of permitted spectrum. Non-parametric spectrum sensing, or estimation, represents one of the prominent tools that can...
This paper presents a new fast locking phase lock loop architecture for frequency synchronization and tracking. The proposed Hyperbolic Σ-Δ No Delay Tanlock Loop (NDTL) has an extended lock-in range and an improved time jitter. The loop has an intentionally introduced hyperbolic nonlinearity, modified Σ-Δ blocks, and finite state machine (FSM), to adapt the loop filter, extending the locking range...
Indoor localization has received significant attention over the last decade. For WLANs, Received Signal Strength (RSS) based techniques have been the most popular due to the simplicity of measuring the power and the ubiquity of WiFi infrastructure and devices in different indoor environments. Recently, Time-of-arrival (TOA) techniques has been proposed to be incorporated into IEEE 802.11 standards...
This paper presents a different perspective on the collective concept of software-hardware defined radio (SHDR) in cognitive radio (CR) networks. The SHDR is proposed considering the multiple hardware functionalities conceived by software defined radio, which generally reflects on the adaptable recognition of network services and operational conditions. An ad-hoc network scheme is envisaged as an...
This paper presents an efficient hybrid frequency synthesizer, that is capable of both integer and fractional division, design based on the Zero-Crossing Digital Phase-locked Loop architecture. The design uses an efficient adaptation mechanism to maintain the in-lock state following the division process. The fast switching, locking and acquisition of the system make it an excellent candidate for synthesis...
Indoor localization has gained considerable attention in the last decade. Different approaches and techniques have been proposed to solve the indoor location problem from received signal strength (RSS) fingerprinting to time of arrival (TOA) based ultra wideband (UWB) systems. However it is highly desirable for the solution to take advantage of existing network infrastructure such as WLAN. RSS based...
This paper describes the design and performance analysis of a new approach for frequencysynchronization and transfer over packet networks. The proposed system utilizestimestamps-based with raised cosine pulse shaping first order adaptive zero-crossing digital phase-locked loop (AZC-DPLL). The system is designedto recover frequency as well as packets, independently of the input signal level in the...
A zero-crossing digital phase locked loop (ZCDPLL) system with dual gain selection technique for fast acquisition, reliable locking and improved phase noise and jitter performance is proposed. The system is designed and simulated based on adaptive loop gain techniques. It utilizes the wide locking range properties and fast acquisition of the high gain loop and enhanced noise performance of the low...
The objective of this work is to evaluate the performance of the Sigma — Delta first order Zero Crossing Digital Phase Locked Loop (SD-ZCDPLL) and compared with the conventional ZCDPLL in the absence and presence of noise. A one bit sigma-delta modulator is used as a part of the proposed structure. The analysis and evaluation of the proposed SD-ZCDPLL has shown to give improvement in the locking range...
An adaptive dual loop phase locked loop (PLL) system with auto selection technique for fast acquisition, reliable locking and improved noise performance is proposed. The system utilizes the wide locking range properties and fast acquisition of the first order loop and enhanced noise performance of the second order loop. The simulation results confirmed the new system's ability to switch between 2nd...
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