1,720,973 research outputs found
Spectrum Sensing: A Distributed Approach for Cognitive Terminals
No full textCognitive Radios is emerging in research laboratories as a promising wireless paradigm, which will integrate benefits of software defined radio with a complete aware communication behavior. To reach this goal many issues remain still open, such as powerful algorithms for sensing the external environment. This paper presents a further step in the direction of allowing cooperative spectrum sensing in peer-to-peer cognitive networks by using distributed detection theory. The approach aims at improving the radio awareness with respect to stand alone scenario as it is shown with theoretical and experimental results. The aim of this paper is to present a spectrum sensing procedure based on distributed network of cognitive terminals (CT). Time Frequency Analysis is employed as part of a classification framework, where multiple devices cooperate to sense the spectrum and, in particular, to classify overlapping air interfaces. Each device carries out the first two steps of cognitive cycle (observation and analysis) working together other CTs to obtain a more detailed and correct radio scene representation. All previous solutions are based on single terminal approach, with no cooperation among devices: this paper aims at improving the flexibility and the generality of spectrum sensing by proposing a distributed classification of air interfaces by means of a network of cooperating cognitive terminals. The distributed algorithm which this work is
based on is the theoretical scheme developed by Varshney, namely the distributed detection without fusion. In order to explain how this objective is reached, it is shown an example in which two air interfaces, Direct Sequence Code Division Multiple Access (DS-CDMA) and Frequency Hopping Code Division Multiple Access (FH-CDMA), are classified by using distributed cooperative terminals. Two cases of study are considered: IEEE WLAN 802.11b and Bluetooth. The paper starts with an analysis of cognitive terminals with their components in case of stand alone (Section III) architecture. Then, the proposed distributed solution is discussed in Section IV, while details are provided in Section V with proposed framework and its sub-parts (Sections VI and VII). Theoretical bases of distributed detection are explained in Sub-Section VII-B. Experimental and theoretical results are reported in Section VIII. Mathematical steps are detailed in Appendix
"Localization and classification of partially overlapped objects using self-organizing trees"
No full textThis paper exploits an innovative technique to improve performances related to localization, tracking and classification of objects in a video surveillance system. The developed strategy has been applied to the problem of interaction between objects, i.e. well tuned traditional algorithms are able to track and classify objects whenever they enter the scene well-isolated from the other moving objects, but the state-of-the-art techniques fail when an occlusion situation is verified from the beginning. The performances of the developed algorithms have been evaluated on sequences of real images and experimental results have shown the validity of the approach
A distributed approach to mode identification and spectrum monitoring for cognitive radios
No full textIn this paper a distributed approach to mode identification and spectrum monitoring is studied. A Wireless Network composed by Cognitive Terminals is used to classify air interfaces present in the radio scene. The use of cooperative strategies and an advanced signal processing tool, Time Frequency analysis, allows to improve the radio awareness of device. Results in the terms of error probability, modeling the probability density function of considered features as Asymmetric Generalized and Generalized Gaussian functions, are compared to error rate showing good performance and coherence of theoretical model with experimental results
"A novel method for static and dynamic location sensing employing WLAN network infrastructure"
No full text
“A novel combined algorithm for 32-QAM carrier recovery"
No full textIn this paper a novel method to realize the synchronization process in case of 32-QAM will be presented. The system is based on the times-n carrier recovery and doesn't depend on data decision. Starting from the Park and Ahn method which tracks, after a non linearity, the carrier recovery only for the in-phase symbols of a 16-QAM modulation, the proposed method combines a Phase Lock Loop and a Costas loop to use also in-quadrature symbols to solve the problem of tracking process. Moreover the algorithm has been extended to a 32 QAM modulation and it has been tested with received symbols corrupted by phase noise and thermal noise. Numerical results are presented to support the effectiveness of the proposed algorithm
"A Simple Mode Identification Algorithm for Multicarrier Signals for Software Radio based Receivers"
No full text“A distributed wireless sensor network for radio scene analysis”
No full textIn this paper a distributed approach to mode identification is considered.
A Wireless Sensor Network composed by Software De-
fined and Cognitive terminals is used to classify air interfaces present
in the radio scene. Two modes, namely Frequency Hopping Code
Division Multiple Access and Direct Sequence Code Division Multiple
Access, are identified employing a signal processing technique,
Time Frequency analysis, and distributed decision theory.
Results in the terms of error probability are obtained, modeling the
probability density function of considered features as Asymmetric
Generalized and Generalized Gaussian functions
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