Spectrum Sensing Techniques and Cognitive Radio Networks: An Analysis

This report provides an in-depth analysis of spectrum sensing techniques within the context of cognitive radio networks. It begins by establishing the growing need for wireless applications and the resulting scarcity of the frequency spectrum, emphasizing the inefficiencies of traditional spectrum allocation. The report then delves into the concept of cognitive radio, explaining its ability to intelligently sense the radio environment and adapt transmission parameters for optimal spectrum utilization, including modulation, carrier frequency, and transmission power. A comprehensive literature review covers cognitive radio networks, digital modulation, spectrum sensing methods, signal detection, link budgets, and agile transmission techniques. The report also explores the application of MATLAB for system modeling and implementation, and concludes with a discussion of the challenges and opportunities in this field. The report highlights the potential of cognitive radio to address spectrum scarcity, enable dynamic spectrum access, and improve the overall efficiency of wireless communication systems.

SPECTRUM SENSING TECHNIQUES AND COGNITIVE RADIO
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ABSTRACT
The mobile communication networks in the modern age are adopting a level of intelligence to
ensure that they sense and automatically adapt to the environment accordingly. The mobile
multimedia networks are faced with several challenges like the scarce resource allocation of the
frequency spectrum and the interference of channels during communication. There is a lot of
wastage when a given section of the frequency spectrum is allocated yet unused. Most of the
cognitive networks are applied to enable dynamic spectrum access, co-existence of different
wireless networks, and interference management. The cognitive radio paradigm is set to drive the
next generation of standards and principles governing the mobile communication and cellular
networks. The cognitive radio technology ensures that the communication systems have flexible
development and there is the deployment of the highly adaptive radios where systems are built
upon the software defined radio technology.
The cognitive radio technology opens several frontiers that can be explored to develop better and
more efficient wireless communication systems for wireless and mobile computing. The systems
end up forming the cognitive radio networks in the cellular mobile communication networks by
extending the radio link features and attributes to a given network layer function. The system
classifies the CRN architecture into a number of unidirectional links and structures. This paper
seeks to carry out an analysis on the MATLAB software for the cognitive network and the
performance analysis of the spectrum-reuse. Common networks introduce issues for the protocol
design, power efficiency, spectrum management and detection, for the emotional awareness and
improved algorithm design. The radio resource allocation policies and economic considerations
are posed by the inherent transmission misappropriations on the wireless links and mobility of
the mobile network end users.
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TABLE OF CONTENTS
INTRODUCTION.....................................................................................................................................4
LITERATURE REVIEW.........................................................................................................................6
Cognitive radio networks.........................................................................................................................6
Digital modulation.................................................................................................................................11
Spectrum sensing...................................................................................................................................12
Signal detection & Link budgets and cognitive radio network design...................................................18
Agile transmission techniques in cognitive radio networks...................................................................20
SYSTEM MODELLING & MATLAB IMPLEMENTATION............................................................20
CONCLUSION........................................................................................................................................21
REFERENCES........................................................................................................................................21
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INTRODUCTION
There is a growing need for the wireless applications and services and as a result the spectrum
resources are needed to meet this demand. The spectrum is allotted to services where the service
provider acquires a frequency band or block from the telecommunication regulatory body in a
given nation. All the services provided require some frequency block which is expected to
increase rapidly and it is able to move towards a fully wireless system where the spectrum is
enhanced. It is very difficult to find a frequency block years later as the primary spectrum is
already assigned to several existing services. The regulatory bodies do not allow the unlicensed
users to access the licensed spectrum. These unlicensed users are required to use a highly
complex, interference-prone frequency band with other unlicensed users. There is indeed a huge
spectrum scarcity problem for the primary frequency spectrum band. A swift scan of the
frequency bands allocated for services in urban settings reveals many unoccupied frequency
bands in the spectrum while those occupied may only be partially occupied. The remaining parts
are heavily used. The radio spectrum, for instance, is quite a limited resource. The resource is
governed by telecommunication bodies and national communication regulatory bodies such as
the federal communication commission in the United States of America.
Cognitive networks are used in the development of the experimental protocol stack to be
implemented in system networks, for instance, cognitive radios. The networks are developed to
have scalable auto-configuration and network management. The dynamic network layer seeks to
support the functionality of the system such that there is IP, group messaging, and rich queries
for the system. The network build on the foundation of the cognitive radio using the GNU radio,
KU agile radio, and the Rutgers radio which has a protocol stack built upon it. The network layer
has an overlay with structured and unstructured for the P2P and the DHT. The services are used
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to map better and particular overlays. The overlay is used to determine the appropriate
application layer of the semi-persistent links between participating nodes that is used to forward
messages between the distributed application elements.
The current wireless communication systems are implemented in the telephony and interactive
internet data for the multimedia type of application. All communication systems desire improved
data rate during transmission and little or no interference. The frequency spectrum is a very
scarce resource that is allocated by telecommunication bodies to the different service providers.
These service providers are able to transmit information to the different mobile users using their
allocated frequency range in the spectrum with a guard band aimed at avoiding interference
between different channels. The technology used in cognitive radio networks presents a new
approach to the use of the scarce resource, that is, the frequency spectrum.
The concept is implemented in the wireless communication networks to ensure that the available
radio spectrum is used comprehensively and that the frequencies can be re-used in different cells
on the mobile communication networks. The cognitive radio technology opens several frontiers
that can be explored to develop better and more efficient wireless communication systems for
wireless and mobile computing. The systems end up forming the cognitive radio networks in the
cellular mobile communication networks by extending the radio link features and attributes to a
given network layer function. The system classifies the CRN architecture into a number of
unidirectional links and structures. This paper seeks to carry out an analysis on the MATLAB
software for the cognitive network and the performance analysis of the spectrum-reuse. Common
networks introduce issues for the protocol design, power efficiency, spectrum management and
detection, for the emotional awareness and improved algorithm design.
The system provides a solution to the crowding problem that results when too many service
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providers have purchased the frequency bands and the remaining bands are limited. The
cognitive radio networks perform the cognitive operations such as the sensing of the spectrum to
determine unused sections of the spectrum. The analysis seeks to determine interference spots,
noise temperature in the transmission network, radio channel characteristics, and the availability
of power in the spectrum. The mobile communication field has encountered advancements in
technology by adopting intelligent systems to have features such as smart antennae, cognitive
packets, smart radios, smart packets, and ultimately cognitive networks. The cognitive networks
employ a wide knowledge base to ensure that the networking technology is addressed using the
common aspect of the technology implemented. The cognitive radio is analysed as the most
preferred cognitive network within the system level scope of mobile communication. The
network intelligence ensures that the resources implemented are understood from a user
requirement point of view and the resources are only allocated to meet these requirements. The
model seeks to improve performance in the networks as well as ensure quality services. The
paper seeks to define the spectrum sensing techniques employed in the efficient implementation
of the fixed frequency spectrum allocation for the wireless communication networks while
utilizing the unused channels or frequency blocks in the network.
LITERATURE REVIEW
Cognitive radio networks
The cognitive network for the radio spectrum is a novel technology that seeks to improve the
spectrum utilization. It allows another user to borrow the unused portion of the frequency band in
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the radio spectrum and in this case, the unlicensed services share the frequency band with
primary licensed users. The cognitive radio operates in a radio frequency environment and it
selects the communication parameters needed to optimize the spectrum usage as well as to adapt
the transmission and reception accordingly. The communication parameters under focus in the
implementation of the cognitive radio are the carrier frequency of a signal, the type of
modulation employed, and the transmission power alongside the signal bandwidth. The cognitive
radio network has a level of intelligence that enables it to sense its surrounding in order to easily
adapt to the current radio environment. The cognitive radio snoops to find holes in the spectrum.
The system provides the frequency in the spectrum holes to the unlicensed users without
interfering or causing harm to the primary user. The cognitive radio is constantly sensing the
spectrum to ensure that once the primary user is back online, the unlicensed user is denied of
service or is transferred to yet another identified spectrum hole. The move seeks to reduce any
form of interference or breach of spectrum use. The allocation to the spectrum holes for the
unlicensed users is a challenge as the different spectrum holes may have the primary users on
different modulation schemes, data rates depending on the transmission device or mobile
equipment being used, and the transmission power in that channel. The secondary users or those
assigned by the cognitive radio network may cause some form of interference such that the
variable propagation environment may be different from their inherent parameters.
The cognitive radio can provide the spectral awareness technology to support FCC initiatives in
spectral use. The software defined radio is developed as a basic platform on which the cognitive
radio is established or built. The software defined radios are the result of the evolutionary
process based on the purely hardware-based equipment to fully support the software-based
equipment. The process is defined that the hardware driven radios, digital radios, and the
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software defined radios are involved. The hardware driven radios constitute the transmit
frequencies, type of modulation, and the radio frequency parameters where the hardware may
have changes. The digital radio in the process is concerned with proper signal processing and
transmission of the digital signals. The signal may be programmed for use in the given system.
This paper discusses the software defined radios for all the functions, modes, and applications to
be configured and reconfigured by the software. Cognitive radio network reference a smart and
alert network that knows what services are available and it can identify them. The system goes
ahead to use the empty spectrum to communicate even more efficiently. The services that
interest the users in a given proximity are easily identified and the system is able to know the
current degree of needs and the future likelihood of the user requirements. The system is able to
learn and recognize the usage patterns of the users so that the Model based reasoning is
employed to meet this objective.
Applications are continuously changing and allocated frequency blocks have diminished the
available limited spectrum. Frequency is a key communication parameter alongside time and
space which run on the 3 degrees of freedom for a communication system for support. The
frequency separates users on the variation of the different frequency bands. The traditional
method requires analog filtering and the system is able to exploit wide bandwidths and DSP as
well as higher frequencies. They tend to present CMOS technology which allows the
communication system to implement up to 100GHz for the system allocation. There is a space
and angle factor that reduces the transmit power. It decreases the radius of omnidirectional cells.
The implementation of the UWB, 60 GHz cognitive radio on the 3 degrees of freedom exploits
the angular nature of the spatial channel by implementing multiple channels. The implementation
further focuses on the use of impulse filtering and sense interference and avoidance.
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The illustration below seeks to describe the cognitive cycle employed for a flexible mobile
multimedia communication scheme such that,
The SDR products and technique are implemented in modern mobile communication systems
and they are actively being improved by standard bodies and organizations. The cognitive radios
have the ability to implement the protocols and policies beyond traditional communications. The
software defined radio defines the type of radio that digitizes its radio frequency and
intermediate frequency functions. Some of the functions that are set up in the digital domain
include the waveform synthesis. The model seeks to obtain a greater flexibility of the system for
the radio operation modes. The SDR does not exhibit the level of intelligence in spectrum
synthesis and sensing as the cognitive networks do.
Mitola’s research defined the cognitive radio as a growing research area with increased interest
in being the next generation of the software defined radio which lacked the intelligence to
navigate through unused spaces in the radio spectrum. The cognitive radio network makes smart
decisions on the frequency and bandwidth that the ISP configures to ensure the communication is
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highly reliable and efficient for the spectrum being used. The radio network has been analyzed
for years with the aim of defining the radio environment and its own behavior. Simon Haykin, in
signals and communication, defined the cognitive radio networks as an intelligent wireless
communication system that is in sync with the radio surroundings. The system that uses the
mode of understanding to build and learn from the environment while adapting to its internal
state of the statistical variation for the incoming radio frequency stimuli. The system seeks to
provide highly reliable communication at all times while efficiently implementing the radio
spectrum.
The mobile communication networks in the modern age are adopting a level of intelligence to
ensure that they sense and automatically adapt to the environment accordingly. The mobile
multimedia networks are faced with several challenges like the scarce resource allocation of the
frequency spectrum and the interference of channels during communication. There is a lot of
wastage when a given section of the frequency spectrum is allocated yet unused. Most of the
cognitive networks are applied to enable dynamic spectrum access, co-existence of different
wireless networks, and interference management. The cognitive radio paradigm is set to drive the
next generation of standards and principles governing the mobile communication and cellular
networks. The cognitive radio technology ensures that the communication systems have flexible
development and there is the deployment of the highly adaptive radios where systems are built
upon the software defined radio technology.
Digital modulation
The carrier signal in a cellular network undergoes modulation such that the message signal is
superimposed to a carrier signal. The sine wave on which the attributes of the information signal
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when the signal is modulated. During modulation any reliable message signal can be detected by
an appropriate demodulator sub-system. There are two types of modulation are the analog and
digital modulation. The following block diagrams illustrate the digital and analog modulation
techniques:
Modulation ensures the digital and analog information is converted to a waveform that is suitable
for transmission over a given medium. It involves the variation of different parameters of a
signal as a function of time or frequency. Some of the common analog modulation techniques
employed in common systems are the amplitude shift keying, frequency shift keying, and phase
shift keying.
Spectrum sensing
The cognitive cycle performs spectrum sensing, management, mobility, and sharing. The
cognitive radio system detects the unused sections of the spectrum, also known as the spectrum
holes. It initiates sharing the spectrum holes with unlicensed users while the primary users of the
frequency blocks do not encounter harmful interference from these new users. The cognitive
radio network senses these using the best techniques to ensure no interference with the primary
users. The network seeks to analyze the communication parameters in a given spectrum hole
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before assigning it to a new service. The service needs to be accommodated in the
communication attributes of a given spectrum hole as sensed. The service assigned to these
unused portions of the spectrum need to demonstrate a match between the user communication
requirements and the communication parameters of the unused spectrum portions. The cognitive
network users are able to exchange frequency of operation once the user requires of the
frequency block or channel. The cognitive users must share the limited spectrum holes hence the
sharing process is scheduled using different scheduling methods. The spectrum sharing is quite a
challenge for the implementation of the cognitive radio network in many mobile communication
networks.
The cognitive radio exploits the time degree of freedom by sensing if a signal is present before
taking the relevant measures to assure that there is no interference. The cognitive radio may opt
to use the time and frequency communication parameters to sense the spectral environment over
the wise bandwidth and transmit signals within the white spaces. It detects if a primary user is in
the frequency block at a given time or if the primary users wishes to use the block and moves to
another new white space. The system ensures that the service moved to a new white space is able
to adapt bandwidth and power levels with the aim of meeting QOS requirements. The spectrum
sensing is key in enabling the functionality and it must be very sensitive to limit unwanted
interference.
When sensing very weak signals,
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