Cognitive radioEfficient spectrum utilization is a great challenge for today’s wireless communications, to overcome this challenge; CR has emerged as a key technology that enables opportunistic access to the spectrum.
A CR is an intelligent wireless communication system that is aware of its surrounding environment and adapts accordingly its internal parameters to achieve reliable and efficient communications 1.Following an opportunistic manner, CR enables unlicensed (secondary) users to exploit the spectrum allocated to licensed (primary) users. As a consequence, innovative and energy efficient MAC and routing protocols must be implemented to improve the coexistence between different users, as well as managing the scarce resources in an efficient way without degrading primary user communication performances.
Best services for writing your paper according to Trustpilot
In general, the main aspects of the cognitive network consist in a behavior-oriented architecture with agents that have a sensor-based robust behavior with slow rate of processing, distributed control, small size, and inexpensive low power consumption hardware 4.Since a wireless networks and wireless sensor networks is comprised of low power consumption devices with limited processor capabilities, in such an infrastructure cognition should be implemented.In recent technology , wireless sensor networks is one of the areas with the highest demand for cognitive networking.Traditionally, these wireless sensor network have been exploited as enabling technology for Ambient Intelligence 5, and adding cognition capabilities to the existing wireless network infrastructure is expected to provide many benefits and advantages such as (i) higher transmission range, (ii) a lower number of nodes required to cover an specific area, and (iii) lower energy consumption per bit. Indeed, the higher communication range provides CWSNs with a smaller number of hops per route. This also provides a smaller average end-to-end delay.Applied those cognitive networks refers to the process of making decision and making action based on network condition’s in order to achieve end to end goals.
When cognitions applied on wireless network it helps the network to achieve better performance by the means of awareness and information sharing in the network. When we added cognitive networks incorporated with wireless networks, there are two objectives to achieve, to make aware of, adapt dynamically to application requirements and the environment in which it is deployed and help the network to achieve its end to end goals by providing holistic approach to the network that is the information about the network status from the network, MAC layer and application requirements from the application layer.The main objective, cognitive wireless network nodes should change their transmission and reception parameters according to the radio environment. Cognitive capabilities are based in four technical components 1, sensing spectrum monitoring 2, analysis and environment characterization 3,optimization for the best communication strategy based on different constraints that is reliability, power consumption and security etc. 4, adaptation and collaboration strategy. cognitive technology will not only provide access to new spectrum it also provides better propagation characteristics by changing the system parameters like transmit power, modulation scheme, constellation size and carrier frequency.it can achieve wide variety of data all these things improve the network life, power consumption and reliability in a wireless network.
Designing wireless networks helps the network more aware of the concurrent conditions of the network but above all can make decisions based on the information, and take actions.In 91 Baumgarten and Mulvenna present the potentials and challenges of future sensor networks, and provide the foundations for sensor nodes with self-adapting ambient intelligence. As an instance, cognitive wireless network could provide access not only to new spectrum (rather than the worldwide available 2.4 GHz band), but also to the spectrum with better propagation characteristics.
A channel decision of lower frequency leads to more advantages in a CWN such as higher transmission range, fewer sensor nodes required to cover a specific area, and lower energy consumption.Cognitive nodes are designed the same infrastructure as wireless nodes but are able to handle cognition processes and manage decisions and actions by commanding other nodes. cognitive nodes in the network, the performance of the network would be improved, as well as the cost, like the energy consumption and the delay 8; in particular, the cost added due to cognition will be as low as possible, and can benefit from previous developments in the design of wireless nodes.Leverage of the previous features of wireless sensor networks and cognitive networks have some basic differences those differences are in wireless sensor network each node send and receive data or it is idle state, in cognitive network wireless network many tiny expensive sensors where each node operated on limited battery energy and there is another state which is called sensing state.
in this sensing state those nodes sense the spectrum to find spectrum holes or spectrum opportunities. So far, each node has various task for transmission and reception of data to consume energy for their tasks.Spectrum sensing task in the cognitive sensing state can be performed either by distrubted and centralized scheme. In a distributed scheme, each node competes with other nodes to access available spectrum 9 and they must have the ability sense the whole channel and determine an optimal scheme to maximize its benefit such as the number of transmissions over time.
Sensor nodes in a CN can measure and provide accurate information at various locations within the network. In addition, a CWN could provide access not only to new spectrum (rather than the worldwide available 2.4 GHz band), but also to the spectrum with better propagation characteristics 9. As an instance, if the transmission power of the secondary user remains the same, its transmission range increases at lower frequencies 12.Analytical Models and Simulations tools for WirelessSensor Networks based on Software Defined RadioThe combination of the CR paradigm and the WSNs is a promising field of research, since it allows the coexistence of overlapping wireless networks in ISM bands by minimizing the interference 24.
II. SPECTRUM SENSINGSpectrum sensing is defined as sensing the radio spectrum to find the spectrum holes in the local neighborhood of the cognitive radio receiver in unsupervised manner. The spectrum holes stands for those sub bands of the radio spectrum that are underutilized at specific instant of time and particular geographic location.Spectrum sensing is the ability to determine and sense whether license user is present or absent. Objective of cognitive radio is that unlicensed user needs to detect the presence of licensed user or shift to another frequency band or stay in the same band by changing its modulation scheme to avoid interference.Spectrum sensing transmitted signal by detect the presence given receiver, cognitive radio Radio to dynamically access the spectrum holes that dynamically appear is predicated upon its ability to detect these white spaces in the first place.Cognitive radioIt’s a radio technique that aims to utilize radio spectrum more efficiently by intelligently exploiting licensed spectrum.
There is increasing number of smartphones and laptops every year which have different QOS requirements these are fast internet, web browsing and multimedia downloads.2238375228600Multimedia00MultimediaCR applications are247650186055Military network00Military network237680545529500407670019685Cellular network00Cellular network1184275114935003085465194945001885950138430CR Application00CR Application1184275242570002948305201930009525114935Emergency network00Emergency network3486150191135Leased network 00Leased network cognitive radio provide service to all users at the same time. That is Use the vacant bandwidth: STs use those spectrums, which are not occupied by primary receivers(users).
Sharing bandwidth: STs can share spectrum as long as they don’t interfere with primary usersCognitive radio network has two types of radio resource are licensed and unlicensed band, licensed bands need small bandwidth and high reliability. those unlicensed radio bands (cognitive radio users) need broadband bandwidth, low reliability but the challenges are to jointly utilize both bands to increase system performance.Types of spectrum sensing Spectrum sensing is the task of finding of spectrum holes by sensing the radio spectrum in the local neighborhood of the cognitive radio receiver in unsupervised manner. The spectrum holes stand for those sub bands of the radio spectrum that are underutilized at the particular instant of space and geographic location.
Spectrum sensing is the capability to determine and sense whether license user is present or absent. The cognitive radio objective is unlicensed users needs to detect the presence of licensed user or shift to another frequency band or stay in the same band by changing its modulation scheme to avoid interference. Spectrum sensing detect the presence of a transmitted signal by a given receiver.
cognitive radio has an ability to access the dynamic spectrum holes that dynamically appear is predicated upon its ability to detect these white in the first place.Spectrum sensing technique are direct and indirect technique, Direct technique is frequency domain out in which estimation is carried out directly from signal approach. Indirect technique also time domain approach and its estimation performed using autocorrelation of the signal.Types of spectrum sensing technique1371600205106001390650233680004410075138430Energy detection00Energy detection186690081280Inferenced based00Inferenced based3819525774700038004759652000-200025253365Spectrum sensing 00Spectrum sensing 1885950243840Cooperative system00Cooperative system4429125210185Match filter Detection00Match filter Detection1123950191135003829050110490001828800186690Non-cooperative system 00Non-cooperative system 4457700243840Cyclo-stationary feature 00Cyclo-stationary feature 139065011493500340042518161000Non-cooperative sensing techniqueNon-cooperative sensing technique means SU relies on its sole effort to detect the presence of a PU transmission spectrum band. This technique has three types which shows in above diagram.1. Energy DetectionIf the secondary user cannot gather sufficient information about the PU signal, the optimal detector is an energy detector, also called as a radiometer.
Energy detection is a non coherent detection method that is used to detect the licensed User signal. If the noise power is known, then energy detector is good choice It is a simple method in which prior knowledge of primary or licensed user signal is not required, it is one of popular and easiest sensing technique of noncooperative sensing in cognitive radio networks. It is common method for detection of unknown signal. There are some drawbacks such as it requires a longer sensing time to achieve good results and unable to differentiate between source of received energy that is It cannot distinguish between noise and primary user.
2.Matched Filter DetectionPrevious WorkMuch research has been done with the help of network simulator. This section gives a detailed report of research that have been implemented with the help of NS2 simulator in the past few years.
NS (from network simulator) is a name for serious of discrete event network simulator, specifically ns-1, ns-2 and ns-34. All of them are discrete event computer network simulator, primary used in research and teaching.ImplementationIn this research, two different protocols have been implemented to show the difference between the result of the proposed system from the existing system. The two the protocols are In this project, two different protocols have been implemented to show thedifference between the results of the proposed system from existing system. The twoprotocols are DSR (Dynamic Source Routing) and TRP (Topology Refresh Protocol)namely.
3. RESEARCH METHODOLOGYThis chapter presents the research methodology used to carry out the research under consideration. This thesis covers all parts of a standard research methodology approach starting from the problem identification to solution and from implementation to validation of results. We have used qualitative, quantitative analysis and experimental methods to answer the research problem under consideration.The work started with the literature review of CR.
Firstly a thorough study of cognitive radio paradigm was conceded. After getting conversant with the working principles of CRs, through journals and research papers, we narrow downed the scope to a more specific area of interest that is spectrum sensing. Spectrum sensing was chosen because of its key role in making CR realizable. A further refined search was carried out on spectrum sensing in cognitive radio using IEEE explore website to get deep knowledge about the current research in the area of spectrum sensing. Additionally, we conduct meeting with our advisor DR. Asrat atenafu to get further insight into the problem.
On the foundation of knowledge base collected over a period of time we defined our research question. We made deductive and statically hypothesis to answer the research problems, to strengthen our defined hypothesis and to motivate our answer, we figured out if there any free spaces in the congested 300GB ISM band.The most important part of any CR is to find the underutilized bandwidth in available radio spectrum in an efficeint manner. The underutilized bandwidth or spectrum holes should be found with the minimal information about spectrum as it is difficult to consider all the dimensions of radio spectrum while monitoring the spectrum for spectrum holes.Study about the all the available spectrum sensing techniques was carried out in terms of qualitative analysis. For experimental and quantitative analysis we used a test bench called MATLAB and LINX ubuntu which is an NS2,Firstly we found out which technique of spectrum sensing is most robust for ISM bands.
After conducting a qualitative research, we found that energy detection method and wavelet detection method was most appropriate for the problem that we consider. We implemented the algorithem over the testbench and gathered the results in forms of raw data constituting FFT values of spectrum at different instances of time. The data collected in real time was arranged in tables so that results could be monitored in graphical way.CHAPTER 4The concept of Cognitive Radio (CR) 1, 88can be synthetized as: devices equipped with the capability to observe and learn from the operating environment, and adapt their wireless communication parameters in order tooptimize network performance.Cognitive radio has key attributes are learn, sense and adapt, their learning mechanisms are necessary to acquire information about communication parameters and to capture the underutilized spectrum by sensing the surrounding.
adaptive and dynamic adjustment of the transmission parameters that is transmission power allows better spectrum utilization. Future wireless communications will require an increasing opportunistic use of the licensed radio frequency spectrum, and the CR paradigm provides a suitable framework for this aim. The main objective of CR paradigm is to improve spectrum usage efficiency, while minimizing the problem of spectrum over-crowdedness 2.Indeed, a CR system is based on the fact that the different parts of the channel are not only allocated to fixed and pre-assigned users, but idle segments of the spectrum are made available to other users.
