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Implementation of spectrum sensing techniques for cognitive radio systems
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This work presents a method for real-time detection of secondary users at the cognitive wireless technologies base stations. Cognitive radios may hide themselves in between the primary users to avoid being charged for spectrum usage. To deal with such scenarios, a cyclostationary Fast Fourier Transform accumulation method (FAM) has been used to develop a new strategy for recognising channel users under perfect and different noise environment conditions. Channel users are tracked according to the changes in their signal parameters, such as modulation techniques. MATLABÂź Simulation tool was used to run various modulation signals on channels, and the obtained spectral correlation density function shows successful recognition between secondary and primary signals. We are unaware of previous efforts to use the FAM characteristics or other detection methods to make a distinction between channel users as presented in this thesis. A novel combination of both cognitive radio technology and ultra wideband technology is interdicted in this thesis, looking for an efficient and reliable spectrum sensing method to detect the presence of primary transmitters, and a number of spectrum-sensing techniques implemented in ultra wideband and cognitive radio component (UWB-CR) under different AWGN and fading settings environments. The sensing performance of different detectors is compared in conditions of probability of detection and miss detection curves. Simulation results show that the selection of detectors rely on the different fading scenarios, detector requirements and on a priori knowledge. Furthermore, result showed that the matched filter detection method is suitable for detecting signals through UWB-CR system under various fading channels. A general observation is that the matched filter detector outperforms the other detectors in all scenarios by an average of SNR=-20 dB in the level of probability of detection (Pd) , and the energy detector slightly outperforms the cyclostationary detector, in the level Pd at SNR=-20 dB. Furthermore, the thesis adapts novel detection models of cooperative and cluster cooperative wideband spectrum sensing in cognitive radio networks. In the proposed schemes, wavelet-based multi-resolution spectrum sensing and a proposed approach scheme are utilized for improving sensing performance of both models. On the other hand, cluster based cooperative spectrum sensing with soft combination Equal Gain Combination (EGC) scheme is proposed. The proposed detection models could achieve improvement of transmitter signal detection in terms of higher probability of detection and lower probability of false alarm. In the cooperative wideband spectrum sensing model, using traditional fusion rule, existing worst performance of false alarms by measurement is 78% of the sensing bands at an average SNR=5 dB; this compares with the proposed model, which is by measurement 19% false alarms of scanning spectrum at the same SNR for cluster cooperative wideband spectrum sensing. The proposed combining methods shows improvements of results with a high probability of detection (Pd) and low probability of false alarm (Pf) at an average SNR=-16 dB compared with other traditional fusion methods; this is illustrated through numerical results
On Employing a Savitzky-Golay Filtering Stage to Improve Performance of Spectrum Sensing in CR Applications Concerning VDSA Approach
Abstract
In this paper, a filtering stage based on employing a Savitzky-Golay (SG) filter is proposed to be used in the spectrum sensing phase of a Cognitive Radio (CR) communication paradigm for Vehicular Dynamic Spectrum Access (VDSA). It is used to smooth the acquired spectra, which constitute the input for a spectrum sensing algorithm. The sensing phase is necessary, since VDSA is based on an opportunistic approach to the spectral resource, and the opportunities are represented by the user-free spectrum zones, to be detected through the sensing phase. Each filter typology presents peculiarities in terms of its computational cost, de-noising ability and signal shape reconstruction. The SG filtering properties are compared with those of the linear Moving Average (MA) filter, widely used in the CR framework. Important improvements are proposed
CYCLOSTATIONARY FEATURES BASED LOW COMPLEXITY MUTLIRESOLUTION SPECTRUM SENSING FOR COGNITVE RADIO APPLICATIONS
The demand for variety of services using wireless communication has grown remarkably in the past few many years, consequently causing an acute problem of spectrum scarcity. Today, it is one of the most challenging problems in modern wireless communication. To overcome this, the concept of cognitive radio has been proposed and this technology is fast maturing.
The first and foremost function a cognitive radio must do is to sense the spectrum as accurately as possible and do it with least complexity. Among many techniques of spectrum sensing, the Multi-resolution Spectrum Sensing (MRSS) is a popular technique in recent literature. Various multi resolution techniques are used that include wavelet based spectrum estimation and spectral hole detection, wavelet based multi-resolution in analog domain and multi-resolution multiple antenna based detection. However, the basic idea is the same - the total bandwidth is sensed using coarse resolution energy detection, then, fine sensing is applied to the portion of interest. None of these techniques, however, use multi-resolution sensing using cyclostationary features for cognitive radio applications which are more reliable but computationally expensive.
In this thesis, we suggest a cyclostationary features based low complexity multi-resolution spectrum sensing for cognitive radio applications. The proposed technique discussed in this thesis is inspired by the quickness of multi-resolution and the reliability of cyclostationary feature detection. The performance of the proposed scheme is primarily evaluated by its complexity analysis and by determining the minimum signal-to-noise ratio that gives 90% probability of correct classification. Both subjective and objective evaluation show that the proposed scheme is not only superior to the commonly used energy detection method but also to various multi-resolution sensing techniques as it relies on the robustness of cyclostationary feature detection. The results found are encouraging and the proposed algorithms are proved to be not only fast but also more robust and reliable
Channel Phase Processing in Wireless Networks for Human Activity Recognition
The phase of the channel state information (CSI) is underutilized as a source
of information in wireless sensing due to its sensitivity to synchronization
errors of the signal reception. A linear transformation of the phase is
commonly applied to correct linear offsets and, in a few cases, some filtering
in time or frequency is carried out to smooth the data. This paper presents a
novel processing method of the CSI phase to improve the accuracy of human
activity recognition (HAR) in indoor environments. This new method, coined Time
Smoothing and Frequency Rebuild (TSFR), consists of performing a CSI phase
sanitization method to remove phase impairments based on a linear regression
and rotation method, then a time domain filtering stage with a Savitzy-Golay
(SG) filter for denoising purposes and, finally, the phase is rebuilt,
eliminating distortions in frequency caused by SG filtering. The TSFR method
has been tested on five datasets obtained from experimental measurements, using
three different deep learning algorithms, and compared against five other types
of CSI phase processing. The results show an accuracy improvement using TSFR in
all the cases. Concretely, accuracy performance higher than 90\% in most of the
studied scenarios has been achieved with the proposed solution. In few-shot
learning strategies, TSFR outperforms the state-of-the-art performance from
35\% to 85\%.Comment: submitted to IEEE Transactions on Mobile Computing (under review
Field Measurements in Determining Incumbent Spectrum Utilization and Protection Criteria in Wireless Co-existence Studies
Studies of spectrum sharing and co-existence between diïŹerent wireless communication systems are important, as the current aim is to optimize their spectrum utilization and shift from static exclusive spectrum allocation to more dynamic co-existence of diïŹerent systems within same frequency bands. The main goal of this thesis is to provide measurement methodologies for obtaining realistic results in modeling incumbent spectrum utilization and in determining incumbent protection criteria.
The following research questions are considered in this thesis: Q1) How should ïŹeld measurements be conducted and used to model incumbent spectrum utilization? Q2) How should ïŹeld measurements be conducted and used to determine protection criteria for incumbents in a co-existence scenario with mobile broadband? and Q3) Which licensing methods and technological solutions are feasible to enable spectrum sharing in frequency bands with incumbents?
To answer to Q1, this thesis describes the development of a spectrum observatory network concept created through international collaboration and presents measurement methodologies, which allow to obtain realistic spectrum occupancy data over geographical areas using interference map concept. A cautious approach should be taken in making strong conclusions from previous single ïŹxed location spectrum occupancy studies, and measurements covering larger geographical areas might be needed if the measurement results are to be used in making spectrum management decisions. The ïŹeld interference measurements considered in Q2 are not covered well in the current research literature. The measurements are expensive to conduct as they require substantial human resources, test network infrastructure, professional level measurement devices and radio licenses. However, ïŹeld measurements are needed to study and verify hypotheses from computer simulations or theoretical analyses in realistic operating conditions, as ïŹeld measurement conditions can not or are not practical to be adequately modeled in simulations. This thesis proposes measurement methodologies to obtain realistic results from ïŹeld interference measurements, taking into account the propagation environments and external sources of interference. Less expensive simulations and laboratory measurements should be used both to aid in the planning of ïŹeld measurements and to complement the results obtained from ïŹeld measurements.
Q3 is investigated through several ïŹeld interference measurement campaigns to determine incumbent protection criteria and by analyzing the spectrum observatory data to determine the occupancy and trends in incumbent spectrum utilization. The ïŹeld interference measurement campaigns have been conducted in real TV White Space, LTE Supplemental Downlink and Licensed Shared Access test network environments, and the obtained measurement results have been contributed to the development of the European spectrum regulation. In addition, ïŹeld measurements have been conducted to contribute to the development and technical validation of the spectrum sharing frameworks.
This thesis also presents an overview of the current status and possible directions in spectrum sharing. In conclusion, no single spectrum sharing method can provide universally optimal eïŹciency in spectrum utilization. Thus, an appropriate spectrum sharing framework should be chosen taking into account both the spectrum utilization of the current incumbents and the future needs in wireless communications.Siirretty Doriast
D21.3 Analysis of initial results at EuWIN@CTTC
Deliverable D21.3 del projecte europeu NEWCOM#The nature of this Deliverable of WP2.1 (âRadio interfaces for next-generation wireless systemsâ) is mainly descriptive and its purpose is to provide a report on the status of the different Joint Research Activities (JRAs) currently ongoing, some of them being performed on the facilities that are available at EuWInPeer ReviewedPreprin
D13.2 Techniques and performance analysis on energy- and bandwidth-efficient communications and networking
Deliverable D13.2 del projecte europeu NEWCOM#The report presents the status of the research work of the
various Joint Research Activities (JRA) in WP1.3 and the results
that were developed up to the second year of the project. For
each activity there is a description, an illustration of the
adherence to and relevance with the identified fundamental
open issues, a short presentation of the main results, and a
roadmap for the future joint research. In the Annex, for each
JRA, the main technical details on specific scientific activities
are described in detail.Peer ReviewedPostprint (published version
Deteção e caracterização de sinais DVB-T para implementação do modelo LSA em Portugal
With the necessity of more efficient use of the spectrum
due to the demand from the consumers, the spectrum
regulatory entities must find ways to make better use of the
available spectrum and create techniques that allow good QoS
and the same reliability as before. Taking this into account,
RSPG proposed the concept of the Licensed Shared Access
(LSA) model which makes use of three dimensions to perform
the frequency sharing: time, frequency and geolocation.
The objective of this dissertation is to present a system
that can incorporate the LSA Model in Portugal and its
purpose is to locate, detect and characterize the incumbentsâ
signal in order to verify if there are good conditions for the
incumbentsâ signal to be transmittedCom a necessidade de uma maior eficiĂȘncia no uso do
espectro radioelĂ©trico devido Ă s exigĂȘncias dos consumidores,
as entidades reguladoras tentam arranjar soluçÔes para tornar
essa utilização de espetro mais eficaz mantendo sempre a
qualidade de serviço e confiabilidade do mesmo. Tendo isto
em conta a RSPG propĂŽs o conceito de modelo Licensed Shared
Access (LSA) que faz uso de trĂȘs dimensĂ”es para realizar
partilha de espetro: tempo, frequĂȘncia e geolocalização.
O objetivo desta dissertação é apresentar um sistema a
ser incorporado no modelo LSA em Portugal, cujo propĂłsito
Ă© localizar, detetar e caracterizar o sinal do incumbente de
modo a verificar se este tem condiçÔes para transmitir o seu
sinal ou nãoANACOMMestrado em Engenharia Eletrónica e TelecomunicaçÔe
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