65 research outputs found
WN: COGNET: Cognitive radio networks based on OFDM
Issued as final reportNational Science Foundation (U.S.
Recent Advances in Wireless Communications and Networks
This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters
A survey of cognitive radio handoff schemes, challenges and issues for industrial wireless sensor networks (CR-IWSN)
Industrial wireless sensor network (IWSN) applications are mostly time-bound, mission-critical and highly delay sensitive applications therefore IWSN defines strict, stringent and unique QoS requirements such as timeliness, reliability and availability. In IWSN, unlike other sensor networks, late arrival of packets or delay or disruption to an on-going communication are considered as critical failure. Also, because IWSN is deployed in the overcrowded industrial, scientific, and medical (ISM) band it is difficult to meet this unique QoS requirements due to stiff competition for bandwidth from other technologies operating in ISM band resulting in scarcity of spectrum for reliable communication and/or disruption of ongoing communication. However, cognitive radio (CR) provides more spectral opportunities through opportunistic-use of unused licensed spectrum while ensuring minimal interference to licensed users. Similarly, spectrum handoff, which is a new type of handoff in cognitive radio, has the potential to offer increase bandwidth, reliable, smooth and interference-free communication for IWSNs through opportunistic-use of spectrum, minimal switching-delays, and efficient target channel selection strategies as well as effective link recovery maintenance. As a result, a new paradigm known as cognitive radio industrial wireless sensor network (CR-IWSN) has become the interest of recent research efforts. In this paper, we highlight and discuss important QoS requirements of IWSN as well as efforts of existing IWSN standards to address the challenges. We discuss the potential and how cognitive radio and spectrum handoff can be useful in the attempt to provide real-time reliable and smooth communication for IWSNs.The Council for Scientific and Industrial Research (CSIR), South Africa [ICT: Meraka].http://www.elsevier.com/locate/jnca2018-11-01hj2017Electrical, Electronic and Computer Engineerin
Spectrum sharing systems for improving spectral efficiency in cognitive cellular network
Since spectrum is the invisible infrastructure that powers the wireless communication, the demand has been exceptionally increasing in recent years after the implementation of 4G and immense data requirements of 5G due to the applications, such as Internet-of-Things (IoT). Therefore, the effective optimization of the use of spectrum is immediately needed than ever before. The spectrum sensing is the prerequisite for optimal resource allocation in cognitive radio networks (CRN). Therefore, the spectrum sensing in wireless system with lower latency requirements is proposed first. In such systems with high spatial density of the base stations and users/objects, spectrum sharing enables spectrum reuse across very small regions. The proposed method in this Thesis is a multi-channel cooperative spectrum sensing technique, in which an independent network of sensors, namely, spectrum monitoring network, detects the spectrum availability. The locally aggregated decision in each zone associated with the zone aggregator (ZA) location is then passed to a decision fusion centre (DFC). The secondary base station (SBS) accordingly allocates the available channels to secondary users to maximize the spectral efficiency. The function of the DFC is formulated as an optimization problem with the objective of maximizing the spectral efficiency. The optimal detection threshold is obtained for different cases with various spatial densities of ZAs and SBSs. It is further shown that the proposed method reduces the spectrum sensing latency and results in a higher spectrum efficiency. Furthermore, a novel power allocation scheme for multicell CRN is proposed where the subchannel power allocation is performed by incorporating network-wide primary system communication activity. A collaborative subchannel monitoring scheme is proposed to evaluate the aggregated subchannel activity index (ASAI) to indicate the activity levels of primary users. Two utility functions are then defined to characterize the spectral efficiency (SE) and energy efficiency (EE) as a function of ASAI to formulate a utility maximization problem. The optimal transmit power allocation is then obtained with the objective of maximizing the total utility at the SBS, subject to maximum SBS transmit power and collision probability constraint at the primary receivers. Since optimal EE and SE are two contradicting objectives to obtain the transmit power allocation, the design approach to handle both EE and SE as a function of common network parameter, i.e., ASAI, is provided which ultimately proves the quantitative insights on efficient system design. Extensive simulation results confirm the analytical results and indicate a significant improvement in sensing latency and accuracy and a significant gain against the benchmark models on the rate performance, despite the proposed methods perform with lower signalling overhead
Spectrum sharing systems for improving spectral efficiency in cognitive cellular network
Since spectrum is the invisible infrastructure that powers the wireless communication, the demand has been exceptionally increasing in recent years after the implementation of 4G and immense data requirements of 5G due to the applications, such as Internet-of-Things (IoT). Therefore, the effective optimization of the use of spectrum is immediately needed than ever before. The spectrum sensing is the prerequisite for optimal resource allocation in cognitive radio networks (CRN). Therefore, the spectrum sensing in wireless system with lower latency requirements is proposed first. In such systems with high spatial density of the base stations and users/objects, spectrum sharing enables spectrum reuse across very small regions. The proposed method in this Thesis is a multi-channel cooperative spectrum sensing technique, in which an independent network of sensors, namely, spectrum monitoring network, detects the spectrum availability. The locally aggregated decision in each zone associated with the zone aggregator (ZA) location is then passed to a decision fusion centre (DFC). The secondary base station (SBS) accordingly allocates the available channels to secondary users to maximize the spectral efficiency. The function of the DFC is formulated as an optimization problem with the objective of maximizing the spectral efficiency. The optimal detection threshold is obtained for different cases with various spatial densities of ZAs and SBSs. It is further shown that the proposed method reduces the spectrum sensing latency and results in a higher spectrum efficiency. Furthermore, a novel power allocation scheme for multicell CRN is proposed where the subchannel power allocation is performed by incorporating network-wide primary system communication activity. A collaborative subchannel monitoring scheme is proposed to evaluate the aggregated subchannel activity index (ASAI) to indicate the activity levels of primary users. Two utility functions are then defined to characterize the spectral efficiency (SE) and energy efficiency (EE) as a function of ASAI to formulate a utility maximization problem. The optimal transmit power allocation is then obtained with the objective of maximizing the total utility at the SBS, subject to maximum SBS transmit power and collision probability constraint at the primary receivers. Since optimal EE and SE are two contradicting objectives to obtain the transmit power allocation, the design approach to handle both EE and SE as a function of common network parameter, i.e., ASAI, is provided which ultimately proves the quantitative insights on efficient system design. Extensive simulation results confirm the analytical results and indicate a significant improvement in sensing latency and accuracy and a significant gain against the benchmark models on the rate performance, despite the proposed methods perform with lower signalling overhead
SPECTRUM SENSING AND COOPERATION IN COGNITIVE-OFDM BASED WIRELESS COMMUNICATIONS NETWORKS
The world has witnessed the development of many wireless systems and
applications. In addition to the large number of existing devices, such development of
new and advanced wireless systems increases rapidly the demand for more radio
spectrum. The radio spectrum is a limited natural resource; however, it has been
observed that it is not efficiently utilized. Consequently, different dynamic spectrum
access techniques have been proposed as solutions for such an inefficient use of the
spectrum. Cognitive Radio (CR) is a promising intelligent technology that can identify
the unoccupied portions of spectrum and opportunistically uses those portions with
satisfyingly high capacity and low interference to the primary users (i.e., licensed users).
The CR can be distinguished from the classical radio systems mainly by its awareness
about its surrounding radio frequency environment. The spectrum sensing task is the
main key for such awareness. Due to many advantages, Orthogonal Frequency Division
Multiplexing system (OFDM) has been proposed as a potential candidate for the CR‟s
physical layer. Additionally, the Fast Fourier Transform (FFT) in an OFDM receiver
supports the performance of a wide band spectrum analysis. Multitaper spectrum
estimation method (MTM) is a non-coherent promising spectrum sensing technique. It
tolerates problems related to bad biasing and large variance of power estimates.
This thesis focuses, generally, on the local, multi antenna based, and global
cooperative spectrum sensing techniques at physical layer in OFDM-based CR systems.
It starts with an investigation on the performance of using MTM and MTM with
singular value decomposition in CR networks using simulation. The Optimal MTM
parameters are then found. The optimal MTM based detector theoretical formulae are
derived. Different optimal and suboptimal multi antenna based spectrum sensing
techniques are proposed to improve the local spectrum sensing performance. Finally, a
new concept of cooperative spectrum sensing is introduced, and new strategies are
proposed to optimize the hard cooperative spectrum sensing in CR networks.
The MTM performance is controlled by the half time bandwidth product and
number of tapers. In this thesis, such parameters have been optimized using Monte
Carlo simulation. The binary hypothesis test, here, is developed to ensure that the effect
of choosing optimum MTM parameters is based upon performance evaluation. The
results show how these optimal parameters give the highest performance with minimum
complexity when MTM is used locally at CR.
The optimal MTM based detector has been derived using Neyman-Pearson
criterion. That includes probabilities of detection, false alarm and misses detection
approximate derivations in different wireless environments. The threshold and number
of sensed samples controlling is based on this theoretical work.
In order to improve the local spectrum sensing performance at each CR, in the CR
network, multi antenna spectrum sensing techniques are proposed using MTM and
MTM with singular value decomposition in this thesis. The statistical theoretical
formulae of the proposed techniques are derived including the different probabilities.
ii
The proposed techniques include optimal, that requires prior information about the
primary user signal, and two suboptimal multi antenna spectrum sensing techniques
having similar performances with different computation complexity; these do not need
prior information about the primary user signalling. The work here includes derivations
for the periodogram multi antenna case.
Finally, in hard cooperative spectrum sensing, the cooperation optimization is
necessary to improve the overall performance, and/or minimize the number of data to be
sent to the main CR-base station. In this thesis, a new optimization method based on
optimizing the number of locally sensed samples at each CR is proposed with two
different strategies. Furthermore, the different factors that affect the hard cooperative
spectrum sensing optimization are investigated and analysed and a new cooperation
scheme in spectrum sensing, the master node, is proposed.Ministry of Interior-Kingdom of Saudi Arabi
Mobile Ad-Hoc Networks
Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks
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