DEVELOPMENT OF SPECTRUM OPTIMIZATION IN WHITE SPACES USING SPECTRUM SENSING AND GEOLOCATION TECHNIQUES

ABSTRACT

Today, wireless networks are characterized by a static spectrum assignment policy. Day after day, there has been an increasing demand in this technological area due to its benefits to human activities and exploration. This spectacular growth in wireless services had also resulted to an increase in spectrum demand to meet up with the human quest. However, an increase in voice demand has been experienced as more people unplug their wired phones and rely strictly on wireless devices for all of their calling needs. Researches from numerous authors have it that radio spectrum has become a scarce commodity due to its high demand. To alleviate the spectrum overcrowding problem, this research went into considering an alternative means. The vacant spectrum allocated to TV broadcast was considered as the most suitable solution to the spectrum crunch. With TV White Spaces (TVWS) which referred to the unoccupied portions of spectrum in the UHF/VHF terrestrial television frequency bands, the aforementioned problem will be overcome. Analysis of its availability were first considered in four locations namely Asaba and environ, Awka and environs, Nkpor and environ, Ubulu-Uku and environ. To achieve optimal channel allocation with high quality of service (QoS), the object oriented development methodology and geolocation techniques were used, also rule based system were employed to formulate the inference rule for the knowledge base, while Genetic algorithm was used to optimize the fitness of the channel for allocation. The hypertext Preprocessor (PHP) with cascading style sheet (CSS) and JavaScript were used as the programming language to achieve this task. Our result showed that over 70 percent available spectra detected and unutilized can be utilized without causing harmful interference to the primary users.

CHAPTER ONE

INTRODUCTION

1. Background of Study

Electronic wireless communication is transmitted with the use of Electromagnetic Frequency Spectrum (Goldsmith, 2006). It is a unique natural resource shared by various types of services which is free from depletion but subject to congestion through use. It has facilitated a sequence of revolutions in human communication. Although, if left unplanned, spectrum congestion can lead to harmful interference and hinder users from getting the best these services have to offer. Traditionally, spectrum band is allocated relatively over a long period of time for the use of a license operator. The use of radio spectrum in each country is nationally regulated by assigned government agency which is responsible for allocating spectrum bands to operators. In Nigeria, the Nigerian Communications Commission (NCC) is responsible for allocation of spectrum. This approach is termed the Fixed Spectrum Allocation (FSA) scheme. With this, the radio spectrum is split into bands and allocated on absolute basis to distinct technology based services, e.g. mobile telephony, radio and TV broadcast services.

Different spectrum bands offer different physical characteristics. Higher frequencies do not carry signals as far and do not penetrate buildings as easily, and lower frequencies have capacity limitations and create more interference. The UHF spectrum is particularly attractive because it is located between 200 MHz and 1 GHz offering an optimal balance between transmission capacity and distance coverage (COM, 2007). New services competing for the VHF and UHF band include mobile television, digital television, and wireless broadband and enhanced phone services.

Following the roll out of commercial mobile communication networks in many parts of the world, the radio frequency is becoming more valuable than ever. Individuals, businesses and governments rely on this natural resource for communication. The growth of Internet as a standard communication platform fueled the emergence of new services like wireless Internet access. As more devices are competing for wireless access, the available radio spectrum is becoming congested. The reserve radio resource pool is also depleting. Hence, in the future new allocations will inevitably become impossible, risking the growth of the whole wireless ecosystem come to a halt. The need to accommodate an ever-increasing number of users and offer bandwidth-rich applications using a limited spectrum challenges the system designer to continuously search for solutions that use the spectrum more efficiently. One technology that has successfully met this need is the digital television technology. The conversion from analogue to digital television will enable a country to benefit from increased spectrum efficiency since less bandwidth capacity is needed to provide the same television services compared to the analogue television.

Radio spectrum is the lifeblood of all wireless communications. Since early 20th century when large-scale commercial use of radio spectrum started, utilization of wireless is a significant factor in many economies around the world. Its contribution has been amplified with the advent of mobile communications in latter part of 20th century due to proliferation of mobile Internet and smart devices in the last few years. New access technologies and increased device capabilities in recent years have resulted in an exponential surge in demand for wireless data communications. This explosive demand has in many cases led to network congestion and the wireless industry is developing means to mitigate the problem through implementation of new techniques supplementing any additional exclusive spectrum.

In this dissertation the TV white space is explored as a solution to surmount the aforementioned problems. TV White Spaces refers the unoccupied portions of spectrum in the UHF/VHF terrestrial television frequency bands. The concept of sharing the highly valued UHF spectrum resource and its use with the primary terrestrial television service is a primary concern today. Wireless broad-band applications are the main focus of trials, nonetheless, the usefulness of this highly sought after spectrum is also being considered for other applications, such as machine-to-machine communications (M2M). TV White Spaces (TVWS) spectrum is a secondary spectrum technology that can take advantage of unused television spectrum in a dynamic manner.

In the developed countries, a process known as Digital Switch Over (DSO) has been completed that basically vacates the UHF and VHF bands as they have started TV broadcasting in Digital band.

In Nigeria, the VHF and UHF frequency bands are mainly occupied by television services. Presently, television broadcasting is analogue however; the government has began the process of DSO. In 2016 December to precise, the digital transition was tested in Abuja, Nigeria capital and the government promised to complete transition in other states before the deadline date. Transition to digital means spectrum can be used more efficiently and this also implies that some bandwidth can be released for new services. The released spectrum is known as the “digital dividend”. The digital dividend is a unique opportunity to meet the fast growing demand for wireless communication services. However, its benefit can only be fully reaped if proper planning is made, ahead of time, for the use of the released spectrum.

However, there is a great deal of underutilized bandwidth that can be found in the digital terrestrial television. A valuable chunk of this spectrum is allocated to television broadcasting which is particularly underutilized. When TV stations are

allocated, the FCC intentionally spreads them out and puts blank channels in between stations in any geographic area to prevent adjacent channel interference between these high-powered broadcast transmitters. These blank channels are referred to as White Space.

The unused portions of the UHF spectrum, popularly referred to as white spaces, represent a new frontier for wireless networks, offering the potential for substantial bandwidth and long transmission ranges. These white spaces include, but are not limited to, 312 MHz of available bandwidth from channel 21 (474 MHz) to 70 (866 MHz), with the exception of channel 52, 53, 59 and 60 marked as reserved in Nigeria.

Subsequently, Akyildiz et al.(2006) found that spectrum use is intense on certain portions while a significant amount remains underutilized. High utilization is common in the cellular and frequency modulation (FM) radio bands, while other bands indicate low usage levels. Though, most of the license owners do not transmit all the time in all geographic locations where the license covers. Records from the FCC indicate that spectrum allocated in the bands below 3GHz have a utilization range of 15% to 85% (Smitha and Vinod, 2012). The current fixed spectrum management approach is therefore, inefficient since it leaves many portions on it unutilized and creates artificial shortage. New and more efficient management techniques are needed to make use of these free portions of the spectrum, also known as “spectrum holes” or “white spaces.” The development of new bandwidth demanding wireless technologies would depend on the availability of radio spectrum. As spectral resources become more limited, the agencies recommend that significant efficiency can be realized by deploying wireless devices that coexist with primary users. As a result, Dynamic Spectrum Access (DSA) was proposed to solve the inefficiency caused by the static allocation of spectrum as affirmed by (Mitola and Maguire, 1999). The basic idea

of DSA is to allow frequency bands that are not being used by their licensed users, (also known as Primary Users (PUs)), to be utilized by cognitive radios CRs, (Secondary Users (SUs)) as long as they do not cause any harmful interference to PUs. Thus the secondary users take advantage of the available resources with minimal interference to the primary users. Consequently, groundbreaking techniques that provide new ways of exploiting the available spectrum are required. With this concept, use of existing radio spectrum is enhanced by opportunistic spectrum access (OSA) of the frequency bands that are not occupied by the licensed or primary user.

The report made by International Telecommunication Union (ITU) shows that the progress made in digital technologies has permitted the evolution of terrestrial television, making it more spectrally efficient by allowing, through digital compression techniques, the transmission of multiple high-quality TV programmes in one single spectrum channel (where before it was possible to transmit only one programme per channel with analogue TV) (Gomez, 2013). Such advancement resulted in the opportunity to reallocate new available UHF frequencies as a result of the analogue TV to digital TV transition (the Digital Dividend) for other uses, namely by wireless broadband applications, in response to the rapidly growing demand for mobile bandwidth.

Broadband internet access has become an essential element of modern life and a critical enabling agent for the global information age economy. In order to tap into the evolving means of lifestyle and source new means of livelihood in a global village, ubiquitous and affordable access to broadband internet service is critical. In Nigeria, according to Nigerian National Broadband Plan (2013-2018), there is appreciable number of submarine cable landings on the shores of the country providing over 9Tbits/s of combined capacity. However, there are concerns about the fact that all the landings are cited Lagos and as such access to

other parts of the country is choked due to the limitations of distribution infrastructure to the rest of the country. Some of the challenges to the roll-out of effective broadband to the coastal and hinterland regions of Nigeria include the geographical topology and economic implications. As a result, most operators usually shy away from providing broadband in rural areas, leading to underserved and unserved regions. Thus there is the need to invest in alternative technologies which could complement coverage range with adequate downlink capacity. Among the promising solutions for extending broadband reach into unserved and/or underserved areas is an emerging networking approach known as TV White Space (TVWS). The term TV White Spaces usually refers to unoccupied portions of spectrum in the VHF/UHF terrestrial television frequency bands in some geographical areas (Gomez, 2013). This portion of the spectrum uses unlicensed, VHF/UHF TV channels to enable the transmission of internet traffic wirelessly over long distances.

These White Spaces vary in number of unused channels as a function of location, due to usage by licensed and unlicensed uses such as terrestrial analogue television broadcasting, Digital Television Broadcasting (DTB) and Program Making and Special Events (PMSE) uses. The spectrum range which includes (European range is 470-790MHz) are notable for their propagation qualities. TV White Space spectrum has the ability to broadcast signals over long distances. It permits more expansive reach than conventional Wi-Fi networks, which utilize higher frequencies that limit their range at a fixed power level. A typical outdoor Wi-Fi signal travels about 100metres versus TV White Space signals that may extend to 400metres at the same power level, or up to as far as 10km at higher power. This impressive reach has spawned the nickname “Super Wi-Fi” for TV White Space networks.

In addition to their impressive range, VHF and UHF frequencies are able to convey energy through physical obstacles. This is because radio signals traversing these frequencies has longer wavelength which has an ability to penetrate walls and buildings with lesser attenuation. These propagation characteristics allow TV White Space enabled broadband access networks to connect over long distances without line-of-sight restrictions, and/or to enable very fast internet connectivity over short distances and through physical obstacles.

As a result of these core basic characteristics – superior range and physical penetration coupled with unlicensed access to spectrum – the economics of TV White Space networks become attractive. There is no direct cost required to use or acquire unlicensed White Space spectrum, the cost associated with TV White Space as an internet delivery medium is instead mainly tied to developing technologies such as antenna and radios that make use of TV White Space. This, just like Wi-Fi can lead to rapid technological innovations tied to the use of TV White Space which can result to cheaper microchips and even technological cost.

Thanki (2014), posited that TV White Space spectrum has the potential to be the world’s first globally available, broadband – capable licensed exempt band in the optimal sub – 1GHz spectrum. In unconnected urban and rural areas, entrepreneurs could use inexpensive, but reliable, Wi-Fi and other types of radio equipment capable of operating on TV band white spaces spectrum to deliver cost-effective broad-band services.

Cognitive Radio (CR) technology has emerged as the key solution to overcome the increasing need of spectrum for wireless communications (3G and 4G cellular system, Wireless Fidelity (WiFi), and Internet, through the implementation of the Opportunistic Spectrum Sharing (OSS) paradigm. It has become the enabling
technology for the next generation (xG) network. Cognitive radio (CR) is an intelligent wireless communication system that is aware of its surrounding environment and under a certain methodology is able to use the current available spectrum momentarily without interfering with the primary user who paid to be served in that area (Mitola, 1999). For instance, let us imagine a portable radio that is able to communicate to its base which is relatively in proximity. This pair can be seen as secondary system and can be pictured as relative local service. Now assume the system is working at the same spectrum of the cellular phone system, which is the primary system; The secondary system should work in a kind of opportunistic way to borrow spectrum without interfering with the primary users or degrading the quality of its service. It therefore means that Cognitive Radio System should be able to scan and sense the spectrum around and find any available spot in frequency to establish its communication, that has to be released once a primary user comes back to claim the spot. Hence, it can be deduce that CR is an intelligent radio platform saddled with the ability to exploit its environment to increase spectral efficiency and capacity (Maninder et al.2012). CR’s are regarded as transceivers that automatically detect (sense the existence of) available channels in a wireless spectrum and accordingly, change their transmission or reception parameters (Naroa, 2011). The CR technology is used for identification, utilization and management of vacant spectrum, known as Spectrum Holes or White Space (Rehan and Yasir, 2010). A spectrum hole is a region of space-time frequency, where a primary user is absent and a particular secondary use is possible. The concept of spectrum hole (white space) and spectrum in use are illustrated in Figure 1.1

As a matter of fact, the initial phase of the cognitive cycle consists of the sensing process. Hence, it is evident that reliable spectrum sensing is the most critical function of the cognitive radio process. By sensing and adapting to the environment, a cognitive radio has the ability to fill in the spectrum holes and serve its users without causing harmful interference to the primary user. Ultimately, a spectrum sensing scheme should give a general picture of the medium over the entire radio spectrum. This allows the cognitive radio network to analyze all parameters (time, frequency and space) in order to ascertain spectrum usage. From the aforesaid, it is essential that there should be efficient spectrum detection techniques that ensure secondary user transmissions, while safeguarding primary users.

Basically, the secondary user identifies “gaps” in the spectrum, known as spectrum holes or white spaces and puts them to use. These white spaces originate from partial or no occupations by the incumbent users, i.e. primary users (PU) for example Digital TV broadcasters. The secondary communication can be executed once the white spaces are identified in the spatial-temporal domain

(Baldini et al.2012). The function of spectrum sensing therefore, is to be aware of the spatial-temporal electromagnetic environment by determining the frequencies occupied by the PU.

A number of methods have been proposed for identifying spectrum opportunities in a scanned frequency band. Typically, spectrum sensing is grouped within three main detection approaches, namely, transmitter based detection methods, cooperative detection methods and interference based methods. Transmitter detection methods consist of matched filter, cyclostationary and energy detection. These techniques are further classified as coherent, semi-coherent or non- coherent; that is, either having complete, partial or no prior knowledge of the transmitter respectively. Schemes that are cooperative include centralized, distributed and cluster based sensing methods. Whereas transmitter and cooperative detection methods “perceive” spectrum to avoid interference to primary transmitters; interference based detection guarantees minimal primary receiver interference.

Geolocation however, is the identification of the real-world geographic location of an object, such as a radar source, mobile phone or Internet-connected computer terminal. It may also refer to the practice of assessing the location, or to the actual assessed location. Geolocation is closely related to the use of positioning systems but may be distinguished from it by a greater emphasis on determining a meaningful location (e.g. a street address) rather than just a set of geographic coordinates. The Haversine formula was employed to determine the distribution and positioning of different White Space Agents (WSAs) in relation with the White Space Device (WSD), in order to help determine the distance between two WSA. This is because it is an important equation in navigation, giving great- circle distances between two points on a sphere from their longitudes and latitudes. This can help in locating the WSAs and also to help determine the

initial co-ordinate of the new facility (xi, yi) defined by centre of gravity using the great distance techniques. Hence, this directed towards spectrum optimization in white spaces using spectrum sensing and geolocation techniques.

1.1             Statement of the Problem

Spectrum sensing is the ability to detect radio signals and estimate the relative location of primary users in order not to interfere with them. Typically, spectrum sensing errors occurs at a very alarming rate. These errors include misdetection (MD) and false alarm (FA). Misdetection means that the spectrum is occupied by primary users (PUs) but the spectrum sensing result says it is available for secondary users (SUs), which will result in transmission collision and influence both PUs’ and SUs’ current transmission. However, false alarm occurs in the opposite way, when SUs believe that the spectrum is being used by PUs but actually the spectrum is idle, which will waste transmission opportunities for SUs. Wrong determination of the exact location of primary users, provoking unwanted interference or white space misdetection has become a big challenge in our today’s wireless world. These aforementioned problems are in the increase due to increase in the demand of wireless devices. Therefore, the problem this work intends to address is the cohabiting of primary and secondary users without interference and continuity in secondary user’s transmission by switching them to available spectrums.

1.2             Aim and Objectives of the Study

The aim of this study is to develop spectrum optimization in white spaces using spectrum sensing and geolocation techniques.

The objectives of this dissertation are to develop a system that should be able to:

1. Optimize the White Space Device (WSD) ability to learn spectrum availability.

• Overcome false detection, misdetection of spectrum holes and eliminate interference.
  • Provide a spectrum sensing model that can find the exact location of white spaces and primary users.

1.3             Significance of the Study

As is known, to eliminate interference, the frequency reuse approach is followed in Digital TV planning similar to cellular network, avoiding the use of the same channel in two neighboring allotments. There are large areas where a certain group of TV channels are deliberately not used. They are called white spaces in TV spectrum (TVWS). Considering the great economical value of TV spectrum, it was proposed to use TVWS for low-power wireless networking on non- interfering (secondary) basis with the licensed (primary) DTV service. At the same time, restrictions imposed on white space devices (WSDs) to protect primary users should not devaluate spectrum for secondary use. The lack of knowledge about the locations of primary receivers as well as unreliability of estimation of the aggregate interference impact caused by the large number of secondary devices accessing the spectrum are reported to be among the key challenges for the use of TVWS which significantly this dissertation is looking forward in overcoming such. Since the research work will be providing WSDs with a list of available channels, the geolocation database will contain recommended parameters for path loss calculations as well as minimum distances which could be ensured for a certain inhabited locality.

TV White spaces are vacant, unused or interleaved frequencies located between broadcast TV channels in the Very High Frequency / Ultra High Frequency (VHF/UHF) range, which can be found between 474 MHz and 866 MHz. The VHF range includes channels two to thirteen (2 – 13), located between 30 and

300 MHz on the electromagnetic spectrum, while the UHF range includes

channels twenty-one to seventy ( 21 – 70), located at 474MHz and above. The merit of propagating at lower frequency is that lower frequencies propagate better over distance and through walls. The merit of propagating at lower frequency is that lower frequencies propagate better over distance and through walls. The logic behind this is to utilize the unused spectrum of the incumbent systems for secondary access so that white space devices with low power can utilize this spectrum without causing interference with the incumbent systems. The unused Broadcast TV channels vary sparingly from one location to another. The TV White space devices will have the flexibility to sense, operate and log on to unused TV White Space channels. This is possible with the use of a database that houses unused channels called geolocation database technology which is the most concern of this work. It is worthy to mention that TV white spaces are very large, dormant spectrum resource that operator could benefit from providing low cost communications. Creating new technologies that will work with this TVWS spectrum with the motive of bridging the gap between digital divide for generations to come is very essential in this contemporary society.

This dissertation can be of great significant because the TVWS will bridge the gap of Digital Divide in Africa and in Nigeria especially. TVWS is an invaluable technology system that could foster the development of Nigeria’s ICT connectivity. When TVWS connectivity is achieved in most Nigerian States, it could supplement end to end broadband internet access coverage of rural and some parts of urban areas in Nigeria. Internet penetration would improve causing reduction in bridging the gap of digital divide. Information professionals need to teach young people how make to make efficient use of TVWS devices and understand their potential. The TVWS occupy a spot in the TV band delivering broadband to challenging rural areas and also making patchy urban Wi-Fi network seamless. With deployment of this work, incumbent operator could

incorporate TVWS spectrum to provide seamless connectivity to areas with

limited connectivity. A TVWS network in the UHF band of TVWS (600MHz) operating at the same power levels as current Wi-Fi devices (40 or 100 mW) needs around 16 times fewer access point to deliver the same coverage as Wi-Fi in 2GHz.This technology is well suited to provide low cost communication to rural communities with poor telecommunications infrastructure (Microsoft 4Africa Initiatives, 2013) affirmed.

However, the recent technology of cognitive radios offers the promise of being a disruptive technology innovation that will enhance the future wireless world. Cognitive radios are fully programmable wireless devices that can sense their environment and dynamically adapt their transmission waveform, channel access method, spectrum use, and networking protocols as needed for good network and application performance. It is anticipated that cognitive radio technology will soon emerge from early stage laboratory trials and vertical applications to become a general-purpose programmable radio that will serve as a universal platform for wireless system development, much like microprocessors have served a similar role for computation. The usage of the radio spectrum is significantly inefficient, and therefore the cognitive radio especially when it is optimize with good model can be extremely useful to exploit the unused spectrum from time to time, as long as the vacancy appears in the spectrum.

This study is significant due to the potential low power TVWS provides. These benefits include rural broadband; due to the favourable radio propagation characteristics for radio frequencies below 1 GHz, TVWS provides a communications environment for affordable wireless broadband services to rural and under-privileged communities in developing countries, particularly those sparsely populated countries with large geographical size. Trials in some countries have demonstrated the potential of TVWS technology to bridge digital divide3 and provide affordable access to the Internet to serve billions of people

that are yet to be connected. Also in hot-spot coverage; TVWS could be used to provide fixed or mobile communications in hot-spots. This is similar to Wi-Fi hot-spots for use in public areas and in M2M communications; TVWS could be used to provide low data rate connections between sensors and devices used for the purposes of control, telemetry or remote monitoring. This can help resolve connectivity challenges to enable the evolving Internet of Things (IoT) or M2M communications. As such communications would demand tens of billions of telecommunications connections by wireless means, the long-range, low-power and low-cost characteristics of TVWS devices may be very suitable for meeting the challenges and demand of IoT/M2M in this regard.

This dissertation is also significant because the increasing demand for wireless connectivity, as part of the evolution of Information and Communication Technologies (ICTs) in the “digital information era”, is driving the research into alternative forms of spectrum utilization in recent years. Securing access to efficient and sustainable ICT infrastructure has become a major goal worldwide, especially considering the vital role that ICTs play across all areas of human life, such as education, health, science, financial markets, security and civil protection, media, entertainment and business development. With a steep increase in the demand for mobile connectivity, the pressure on the supply side of the resource (the radio spectrum) becomes inevitable. While levels of spectrum demand are likely to vary across different regions depending on factors such as population density, geographic characteristics, and scale of development of broadband fixed networks; the rise of advanced consumer mobile devices and data-demanding mobile applications has considerably increased the usage of bandwidth in mobile spectrum bands in both mobile networks (e.g. 3G & 4G) and non-license local area networks (e.g. WiFi access). Also, emerging economies are embracing more and more the benefits of wireless broadband communication therefore realizing

more value from the radio spectrum as a national infrastructure resource. It also

provides a more affordable and flexible alternative for internet access to citizens and contributes in a more expeditious way to reducing the digital divide.

This dissertation is also significant because of the potential benefits of rural and urban broadband deployment. It means that the highly favorable propagation characteristics of the TV broadcast spectrum (as compared to unlicensed 2.4 or 5 GHz bands) will allow for wireless broadband deployment with greater range of operation (including the ability to pass through buildings, weather, and foliage) at lower power levels. Thus, the TVWS could be used to provide better broadband service in less densely populated areas. Hundreds of urban centers across the nation are already deploying first generation wireless local area networks to provide broadband access to residents. Use of the TVWS for such municipal broadband networks could increase the quality of service and decrease the deployment costs for these networks. More so, it will enhance public safety communication; that is to say that public agencies can have access to spectrum in the TV band; this would improve the capacity and quality of their networks, as well as facilitate their expanded use for e-government and consumer services. In emergencies, the TVWS can also provide supplementary services to augment public safety communications. It can also help in education and enterprise video conferencing. The TVWS could be used to give local high schools and middle- schools the same multimedia capabilities available to major university campuses: mobile, high speed Internet access for every student and teacher with a laptop or portable wireless device. In personal consumer applications, TVWS could be used to provide new services and applications to consumers by taking advantage of the improved signal reliability, capacity, and range of the TV broadcast spectrum. Wireless local area networks using low power and battery operated devices could enable new communications technologies that bring safety, convenience,   and   comfort   to   consumers   in   their   homes.   The   favorable

propagation and bandwidth characteristics of the TV broadcast spectrum could

enable enhanced video security applications for commercial, residential, and government purposes. Some examples of security applications using the white space devices include perimeter video surveillance, robust wireless secure area monitoring, and childcare monitoring in the home or in childcare facilities. The highly favorable propagation characteristics of the TV broadcast spectrum will allow for wireless broadband deployment with greater range at lower transmits power levels. This could, therefore, reduce the number of cell/sites needed to cover a geographical area as compared with the conventional High Speed Packet Downlink Access (HSPDA), Wide Code Division Multiple Access (WCDMA) and Worldwide Interoperability for Microwave Access (WiMAX) systems and subsequently reduce the energy consumption.

Sensing only cannot provide adequate protection to the broadcasting service and the primary users, taking into account current technologies. This dissertation shall extend into employing geolocation with access to database and multiagents, which shall help record valid information about the available frequencies, exchange information about the locations, switch unlicensed users synchronously to the available frequencies and perform proper handover incase the transmitting device is moving to another location.

1.4             Scope of the Study

This research work is centered on the utilization of terrestrial communication technology as an alternative means of reducing the high competition in our spectrum world today. With the digital switchover, the so called digital dividend or white spaces appeared in the TV bands. TV White Spaces (TVWS) are vacant, unused or interleaved frequencies located between broadcast TV channels in the Very High Frequency / Ultra High Frequency (VHF/UHF) range, which can be found between 177MHz and 226 MHz on VHF and 474 MHz and 866 MHz on UHF. These white spaces are unused frequency bands within the TV transmission

spectrum. There are also a range of other innovative usages of TVWS that might appear due to the favourable propagation characteristics. This study concern therefore, is optimal utilization of the white spaces within four locations namely Awka regions and environs, Nkpor and environs, Asaba and environs, Ubulu-Uku and environs. Though, there are other regions in Nigeria where the utilization of white spaces can also be harnessed. The study will be using spectrum sensing and geolocation techniques to determine the white space availability.

1.5             Limitations of the Study

The limitations encountered in carrying out this research work includes restrictions in the use of required instruments/tools by relevant companies, provision of separate secure network system for white spaces that will not interrupt with normal communication for that period. Another major constraint in this work is the different bodies involved and their respective policies.

1.6           Definition of Terms

Allele: This is the value a gene takes for a particular chromosome

Chromosome: This is the literal string encoded form of solutions that the classical genetic algorithm paradigm deals with.

Cognitive Radio (CR): This is a form of wireless communication in which a transceiver can intelligently detect the communication channels that are in use and the channels that are not and instantly move into vacant channels while avoiding occupied ones. This optimizes the use of available radio-frequency (RF) spectrum while minimizing interference to other users. Put differently it is a radio that employs model-based reasoning to achieve a specified level of competence in radio related domains.

Crossover Operator: This is a recombination operator in genetic algorithm,

where new solution in new generation is created by taking into account more than one solution from previous generation.

Fitness Function: A fitness function simply defined is a function which takes the solution as input and produces the suitability of the solution as the output.

Gene: This is one element position of a chromosome

Genetic algorithms (GAs): This a search-based optimization technique based on the principles of genetics and natural selection. It can also be seen as a computer programs that mimic the processes of biological evolution in order to solve problems and to model evolutionary systems.

Genetic Operators: These alter the genetic composition of the offspring. These include crossover, mutation, selection, etc.

Genotype: This is the population in the computation space. In the computation space, the solutions are represented in a way which can be easily understood and manipulated using computing system.

Geolocation: This is the identification of the real-world geographic location of an object, such as a radar source, mobile phone or Internet-connected computer terminal. It can be seen as the practice of assessing the location.

Mutation Operator: This is a recombination operator in genetic algorithm, where new solution is created from the single solution by changing some characteristics within it.

Mutation: This can be defined as a small random tweak in the chromosome, to get a new solution. It is used to maintain and introduce diversity in the genetic population and is usually applied with a low probability.

Optimization: This is the act of designing and developing systems to take maximum advantages of the resources available.

Phenotype: This is the population in the actual real world solution space in which solutions are represented in a way they are represented in real world situations.

Pixels: All the terrain covered by a geo-location database is represented as “pixels” which are squares of prearranged dimensions

Population: This is a subset of all the possible (encoded) solutions to the given problem. It can also be defined as a set of chromosomes.

Primary Users (PUs): These are known as licensed users that can access the wireless network resources according to their license.

Secondary Users (SUs): These are seen as unlicensed users that are equipped with cognitive radio capabilities to opportunistically access the spectrum.

Sensor: This is a device that detects and responds to some type of input from the physical environment. The specific input could be light, heat motion, moisture, pressure, etc.. The output is generally a signal that is converted to human readable display at the sensor location or transmitted electronically over a network for reading or further processing.

Spectrum Hole: This is defined as a band of frequencies assigned to a primary user, but, at a particular time and specific geographic location, the band is not being utilized.

Spectrum Sensing: A CR user can only allocate an unused portion of the spectrum. Therefore, the CR user should monitor the available spectrum bands, capture their information, and then detect the spectrum holes.

Spread Spectrum: This is a form of wireless communications in which the frequency of the transmitted signal is deliberately varied. This result in a much greater bandwidth than the signal would have if its frequency were not varied.

Transceiver: A transceiver is a combination transmitter/receiver in a single package. The term applies to wireless communications’ devices such as cellular telephones, cordless telephone sets, handheld two-way radios, and mobile two- way radios. Occasionally the term is used in reference to transmitter/receiver devices in cable or optical fiber systems.

TV White Spaces: These refers to the unoccupied portions of spectrum in the UHF/VHF terrestrial television frequency bands

White Space Device (WSD): A device that can make use of the white space spectrum is often termed as white space device (WSD). It is an unlicensed device that operates in a spectrum that generally provides communications of broadband data and other services for consumers and businesses.

White Space Spectrum: This refers to unused broadcasting spectrum at individual locations which could be made available for other applications, such as wireless broadband

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