Dream Destination Free Essays

What might be your fantasy goal on the off chance that you don't have to stress over the spending plan and time? Sun, sand and ocean, a thousand ‘Robinson Crusoe’ islands, gigantic tidal ponds with various profundities and endless shades of blue and turquoise, astonishing submerged coral gardens; an ideal normal blend for the perfect tropical occasion goal. Anyway there is a whole other world to the Maldives than simply that. Mal Dives contains 1,190 coral islands, framing an archipelago of 26 significant atolls on Southwest of Sri Lanka, on the equator. We will compose a custom paper test on Dream Destination or then again any comparative subject just for you Request Now It extends 820 kilometers north to south and 120 kilometers east to west. 02 are occupied, 87 are elite retreat islands. The climate there is commonly warm and sticky. There are sun sparkles the entire year through, and the normal temperature is around 29 †32 degrees Celsius. The roots of the Maldivians are lost in ancient history, however history uncovers that the islands have been populated for more than 3,000 years prior. Early pilgrims were voyagers on the Silk Route and from the Indus Valley Civilization. Inalienably warm, cordial and affable commonly, it is anything but difficult to feel good and loose with a Maldivian. A pleased history and rich culture advanced from the primary pilgrims who were from different pieces of the world venturing to every part of the oceans in antiquated occasions. The Maldives has been a mixture of various societies as individuals from various pieces of the world came here and settled down. A portion of the neighborhood music and move for example look like African impacts, with handbeating of drums and melodies in a language that isn't known to any however positively speaks to that of East African nations. As one would expect there is an incredible South Asian impact in a portion of the music and moving and particularly in the conventional food of the Maldivians. Anyway a significant number of the South Asian traditions particularly as to ladies are not fundamentals of life here †for example, the Sub Continent’s custom of withdrawing ladies from general visibility. Truth be told ladies assume a significant job in the public arena †not astonishing considering the reality men spend the entire outing adrift angling. A large number of the customs are emphatically identified with the oceans. Dhivehi is the language verbally expressed in all pieces of the Maldives. English is generally spoken by Maldivians and guests can without much of a stretch make themselves clear getting around the capital island. In the retreats, an assortment of dialects are spoken by the staff including English, German, French, Italian and Japanese. After a brief glance at Mal Dives’ geology, atmosphere, causes, societies and dialects, it’s time for me to reveal to you my own motivation to pick Mal Dives as my fantasy goal. The Beaches in the Maldives are marvelous. Families invest their energy there with for unwinding, and couples may go there for nectar mind-set. I am so keen on a portion of the hotels which are assembled directly on the ocean. It stimulates my longing to bounce into the ocean toward the beginning of the day and I am certain I can remain in the hotel for an entire day. Another exceptional action is scuba jumping. Maldives is prized as one of best jumping goals, it is where a diver’s blessing from heaven. Plunging Safaris will lead you to energizing spots scarcely ever visited previously. It is the best chance to find the amazing excellence of the captivating submerged realm known as the best submerged landscape on the planet. What's more, since I appreciate taking pictures, I will attempt to fill my photograph collections with photographs of Mal Dives. I accept the normal wonderful scenes of Mal Dives will intrigue my loved ones. Perhaps I will even attempt to take pictures submerged. Ideally I will find the opportunity to take a few pictures with mermaids. Despite the fact that I don’t need to stress over spending plan and time, I despite everything need to design my timetable for the excursion to Mal Dives. I think I will go through at any rate 5 days 4 evenings there with a notable individual of mine. I intend to make this outing sentimental for my young lady as I wish to win her heart effectively. The initial 2 evenings I will decide to remain in Olhuveli Beach Spa Resort, and I plan to remain at the Honeymoon Water Villa. During the stay at Olhuveli, we can do numerous sorts of water sports there, for example, windsurfing or kite boarding. Afterward, we will go to a sun spa to unwind. The glorious Sun Spa at Olhuveli adopts an incorporated and all encompassing strategy to your wellbeing, giving all encompassing medicines to your body, brain and soul. At that point, the remainder of the special seasons I will be in Soneva Fushi in Mal Dives. The explanation I pick this retreat is that it includes its wilderness and sea shore side area. It is exceptional to the point that everything there is by all accounts made of wood. I am anticipating strolling in the woods in the early morning before breakfast. Afterward, I will remain around the pool for the remainder of the morning. Afterward, in the wake of sleeping in the wood house, we will do cycling before supper to end the day. Be that as it may, Mal Dives is reviled with mounting proof of a natural fiasco. Government researchers dread the ocean level is ascending to 0. 9cm per year, and the Maldives could get dreadful inside 100 years. What we can do to help Mal Dives is to diminish the discharge of ozone depleting substance, for example, utilizing machines effectively, and abstaining from utilizing plastic sacks from markets. It is imperative to secure and save such a delightful spot as Mal Dives. To summarize, as the point says, I picked Mal Dives to be my fantasy goal since I don’t need to stress over the move and time. Be that as it may, I may need to chip away at my dialects (for instance, to become familiar with some Dhivehi, and in particular, improve my English. ) Anyhow, I trust I am now one bit nearer to my fantasy goal. I say thanks to Wells for allowing me the chance to connect with myself in the examination on Mal Dives and to get familiar with some English when composing this discourse. This is actually an extraordinary practice. Much obliged to you for tuning in. Asset: http://www. visitmaldives. com/http://www. olhuveli. com/http://www. sixsenses. com/soneva/ Instructions to refer to Dream Destination, Papers

Fitzgeralds Translation of Omar Khayyam Coursework

Fitzgeralds Translation of Omar Khayyam - Coursework Example The best piece of his sonnets was made during his childhood in the tranquil and excellent scene of Nishpur. The deciphered rendition of his popular Rubaiyat (Quatrains) was first distributed by Edward Fitzgerald in 1859, which put him on the map all through the Western world. On the off chance that the disposition communicated in the popular Quatrains, says Gibbs, isn't the most courageous or lifted up, none-the-less they got the specific tone of the age, and voiced it as impeccably as eight centuries sooner they had voiced the distributed indulgence of the refined society of Isfahan. Postcolonialism is simply the revaluation of Western culture's origination of itself in the light of the stifled history of misuse of other people groups on which Western monetary prosperity and circulation of riches is based (Robert 2003, p. 1). Postcolonial analysis is portrayed by a suspicion concerning those liberal ideas of good and political equity which generally existed together joyfully with unfair frontier rehearses. Reliable with this scrutinize, it additionally attempts to reformulate increasingly conceivable ideas for understanding what really occurred under imperialism, reclaiming past occasions from pilgrim belief systems of progress from freedom, and developing new classes for mapping a safe world from the colonized perspective. In examining recorded work of Omar Khayyam it turns out to be increasingly more common to liken chronicled contrasts with social contrasts. The issues looked by the Edward Fitzgerald crossing chronicled limits are so like those of the social anthropologist that no expression of remorse for this conflation looks vital. Both hermeneutical acts are so firmly partnered in methodology and purpose that we effectively overlook their disparities, or that one must, in some sense, be an analogy for the other. Or then again maybe 'metonym' for the other is increasingly exact, if presumption of that progression with the past empowering discourse is broadened or strengthened by the equal of deciphering Omar Khayyam's societies. Since societies are as often as possible contemporaneous with out own, they can, whenever permitted, argue in a more clear way than the past. Similarly, translators of recorded contrast (like Fitzgerald) keep up the equal at their end by understanding as a ruler of interpr etation the exertion by which they attempt to enroll the Omar's voice in which the past answers to their inquiries, an interpretation which may include adjustments to the language into which the interpretation passes. At the point when Edward Fitzgerald entered the modified scene of another culture, he picked not exclusively to make an interpretation of old style implications into English implications yet in addition to transpose1 certain outsider propensities for discourse and thought. He did this since, similar to every single incredible artist, he thought about language and structure, and realized that the language of English verse itself would be reinforced and advanced by the minor infringement to which he was eager to subject it. He likewise found the old world itself was a long way from being a uniform field. Edward Fitzgerald dangers misshaping the English language under the weight of converting into it an outsider structure. In any case, the hindrance of standing up to trouble is a fortifying and advancing of the artist's language. This

9 Books That Are a Call to Action Against Rape Culture

9 Books That Are a Call to Action Against Rape Culture (Image by Chase Carter, via Flickr) I dont know why it  took me so damn long to read Rebecca Solnits  Men Explain Things to Me.  As someone who writes about female sexuality, consent, and rape culture for a living, Solnits book should have been considered  required reading. Becauseâ€"though the book as a whole is about the gender wars in generalâ€"the two pieces that  really  donkey-kicked me in the gut were the ones that tackled domestic violence and sexual assault. In The Longest War, Solnit writes that every three years, the death toll from domestic violence tops 9/11s casualties, though no one declares war on this particular kind of terror. In #YesAllWomen, Solnit writes about the changing conversation around rape culture, and on how womens voices are growing louder, and their experiences more visible. Reading this slim collection was like hearing a rallying cry, and I knew it should be required reading not just for me, but for all men and women. But beyond Solnits book, what else should be on the curriculum? Unspeakable Things  by Laurie Penny I first discovered Pennys work by going down a rabbit hole of brilliance revealed in Molly Crabapples  Drawing Blood. In  Unspeakable Things,  Penny presents a raw, ranting manifesta on gender and power, including the prevalence of sexual violence. Missoula  by  Jon Krakauer I eat up every single thing Krakauer writes, but this one was hard to get through. About a series of sexual assaults at the University of Montana and the long slog toward possible justice,  Missoula  is relentless in its hopelessness, and places a spotlight on the impotence  of  our justice system. Valerie wrote a great roundup of related reads just last year. Bad Feminist  by Roxane Gay Gays collection is about many things, including race and pop culture and even competitive scrabble. But there is also much to read here about gender and femininity, safety and sexual violence. Gay is brilliant about all of it, bringing her sharp eye and her quiet humor and a sense of solid matter-of-factness to everything she explores. Yes Means Yes!  edited  by Jaclyn Friedman and Jessica Valenti Jaclyn Friedman is a writer, speaker, and activist. Jessica Valenti is the woman behind Feministing. Together, they present an anthology that unpacks issues of rape culture and explores the shift in consent education from no means no to yes means yes. Asking for It  by Louise ONeill Recently published,  Asking for It  is  a YA novel that tackles head-on a young girls rape, the public shaming she has to endure afterward, and the effects this has on her as a woman. Its good to see more and more works of YA refusing to flinch in the face of an issue that is sadly common. Asking for It  by Kate Harding It carries the same title, but this version of  Asking for It  is actually a nonfiction exploration of rape culture that combines in-depth research and reportage. We Should All Be Feminists  by Chimamanda Ngozi Adichie I read this one after falling in love with Adichies  Americanah  (which I could rave about in a post all its own). In this extended essay adapted from  a TEDx talk about feminism, Adichie tackles the many reasons we should well, all be feminists obviously, giving a glimpse of the sexual violence that has occurred in  Nigeria, showing the universality of the ever-enduring  war on women. Luckiest Girl Alive  by Jessica Knoll The protagonist of this novel has been the victim of a gang rape. The reader follows her attempts to rise above and past this traumatizing incidents personal repercussions. It is only recently that Knoll revealed just how much this story grew out of her own personal experience. Her heart-wrenching personal essay on Lenny Letterâ€"in which she comes out as a victim of sexual assaultâ€"had me in tears. For more fiction that tackles issues of sexual assault, read this roundup Nicole wrote last year. April was Sexual Assault Awareness Month. It is now May. This topic is evergreen. It continues to be worth our while to amplify the voices that shout out against rape culture and then, perhaps, to add our own.

Basketball Is A Popular And Beloved Sport Essay - 1405 Words

Basketball is a very popular and beloved sport that is still being played today. Michael Jordan, who played for the Washington Wizards and the Chicago Bulls once said, â€Å"Just play, have fun, and enjoy the game† (BrainyQuote 2016). Whether playing with friends for fun or by professionals for entertainment or simply watching from home, basketball is enjoyed all over the world. Beginning with a unique history, basketball has evolved over time from a simple idea into a professional career choice for those with the unique skill set. During the winter of 1892 in a town in Massachusetts a physical education teacher, Dr. James Naismith, at a YMCA school created a game where young men could play indoors apart from going outside in the freezing cold. To be prepared for the game, Dr. Naismith came up with some rules for the game, gathered two peach baskets for hoops, a soccer ball, becoming the first basketball game in history. The young men did not know how to play the game, but they still had fun doing it. The game only lasted thirty minutes with the final score being 1 point to 0 points. During this game, William R. Chase became the first person to ever score in a basketball game (Faurschou, 2016). Dr. Naismith came up with thirteen rules. While four out of the thirteen rules that he came up with, are no longer followed in today s version of basketball, the nine that are left were slightly modified and are still in use today. The original thirteen rules are as follows: The ball isShow MoreRelatedBasketball Is The Most Popular And Beloved Sports Essay1359 Words   |  6 PagesProfessional Basketball Basketball is one of the most popular and beloved sports that is played today. Michael Jordan who played for the Washington Wizards and the Chicago Bulls once said, â€Å"Just play, have fun, and enjoy the game† (BrainyQuote 2016). 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Spectrum sensing in cognitive radios using energy detection technique - Free Essay Example

Sample details Pages: 29 Words: 8570 Downloads: 7 Date added: 2017/06/26 Category Statistics Essay Did you like this example? Chapter 1.Introduction In recent years there has been an enormous growth in wireless communication devices and wireless users. The ever increasing demand for higher speed and reliability made researchers think about intelligent radios like Cognitive Radios (CR). But major amount of spectrum is available for licensed users. There are various communication bodies like the International Telecommunication Union (ITU), European Conference of Postal and Telecommunications Administrations (CEPT) also European Telecommunications Standards Institute (ETSI) who works on standards of communication that defines the use of spectrum for licensed and unlicensed users. 1.1 Background Spectrum is a valuable resource in communication. Over the past few years as the use of various wireless technology is increasing rapidly so we either need more spectrum or make efficient use of current spectrum to satisfy their needs. One way of making efficient use of spectrum is employing spectrum sharing technique. There are many spectrum sharing techniques available like energy detection, cyclostationary feature detector, and matched filter. Of the above technique matched filter and cyclostationary gives more accurate result but they are bit complex and computationally harder as compared to energy detection technique. Energy detection is the simplest of above three and computationally less complex. Don’t waste time! Our writers will create an original "Spectrum sensing in cognitive radios using energy detection technique" essay for you Create order 1.2 Motivation Survey has shown that at any given time only portion of spectrum is utilized. According to a report published by FCC (Federal Communications Commission America) in 2003 has set a set of rule for efficient use of spectrum for licensed and unlicensed users. Also OFCOM (Office of Communications United Kingdom) has noticed the underutilization of spectrum. At any given time only portion of spectrum is utilized. Even if the system says there are no frequencies available, there is still some frequency available. These available frequencies are known as spectrum holes or white spaces. Some of the bands are completely occupied by users while some bands go unutilized. And that is inefficient use of spectrum. We must have noticed that in cases of emergencies like the train bomb blast in July 2006 in Mumbai, India cellular network actually failed to support huge amount of customer at the same time, this was also the case during 9/11 in USA. If we were having cognitive radios at that time peop les would have been able to talk to their families and inform about their safety. As we are moving from 3G (Third generation) to 4G (Fourth Generation) we need to make certain changes in our wireless technologies. Below shown is the measurement of 0 GHz to 6 GHz at Berkley Wireless Research Center (BWRC). Figure 1 Measurement of 0-6 GHz Spectrum Utilization at BWRC [20] 1.3 Aim and Objective This thesis emphasises on understanding Cognitive radios, the importance of spectrum sensing for todays world, the issues regarding the same. A simplified Matlab code is used to support our thesis. As the thesis follows you will find more about cognitive radios and spectrum sensing with a technique to generate white space at a specific frequency. The main objective of the thesis is to do survey on spectrum sensing and spectrum sensing techniques. Then do plan a model for the same. A model can be supported by a Matlab code. And after all this we need to analyse the model we suggested and further improvements that can be done in that. 1.4 Thesis Organisation Our thesis is organised as follows: Chapter.2 Literature Review This chapter begins with a brief history about cognitive radios .Which is followed by a detail explanation of Cognitive radios and spectrum sensing and some of the spectrum sensing techniques used. At the end of this chapter a business model for spectrum sensing and multi resolution of CR is given. Chapter.3 System Description This chapter basically deals with sampling and its importance to us. Also you will find technique to get your spectrum at specific center frequency under generation of White Spaces. Chapter.4 Simulation/Design Analysis As the name suggests, this chapter deals with simulation model and detail explanation of the code used for spectrum sensing using energy detection. In this chapter we have shown the output of the simulation used. Chapter.6 Future Work This chapter suggests some of the future work to be done with this thesis which could be useful for further research in this field. Chapter.7 Conclusion This gives the concluding part of the thesis. Chapter 2 Literature Review In this chapter we are going to discuss about the cognitive radios, like what are they and why are they so important to us. The chapter begins with a short history of cognitive radios, which is followed by a general discussion on OFDM, some of the challenges faced by cognitive radios in real environment, and also some of the applications of cognitive radios. We have tried to explain spectrum sensing in brief and the techniques used for spectrum sensing in todays world. Finally a business model for spectrum sensing is showed which is preceded by multi-resolution of Cognitive radios. 2.1 History of cognitive radios Dr. Joseph Mitola III was the first to introduce or propose the theory of Cognitive radios in 1999. According to Dr. Joseph Mitola Cognitive radios will be the radios that are smart and intelligent enough to find the available bandwidth in a spectrum. It will also have knowledge of right information that has to be passed to the user. And user does not have to take some extra effort for that. It is supposed to do this automatically. He has also mentioned in his PhD dissertation that CR is natural extensions of software defined radios. In 2002 the FCC published a report prepared by Spectrum Policy Task Force [SPTF] which says that majority of spectrum is underutilized. And there is actually is not shortage of spectrum but rather we need to make efficient use of the current spectrum. Also in same year 2002 Professor Cave from UK presented a report which speaks of the possibility of selling bandwidth to the user depending on their requirement. But it would not be fair to give unlicensed user allow to use licensed spectrum. So in December 2002 FCC issued a Notice of Enquiry (NOI) to see TV channel bands can be made available to unlicensed users. Then in 2003 FCC forms a set of rules and proposed interference temperature model for keep track of interference. Later in the same year Notice of Proposed Rulemaking (NPRM) tried to see into issues related to cognitive radio technology where it also pointed out Cognitive radios is a advanced technology which could help efficient use of spectrum by licensed users in own network and by sharing spectrum and with unlicensed users by negotiating when required. This encouraged many researchers in the field of cognitive radios. Major progress in cognitive radios took place in the year 2004, where FCC published NRPM which showed possibility of allowing secondary users to use licensed spectrum. FCC opened three bands for unlicensed users which are 6525 to 6700 MHz, 12.75 to 13.15 GHz and 13.2125-13.25 GHz. This allowed cognitive dev ices to transmit six times more. Also IEEE standards are working parallel to the FCCs. Spectrum pooling system by Professor Timo A Weiss from Karlsruhe University Germany), OFDM based Cognitive radios by professor Ian F Akyildiz et al from GIT (USA) are some of the promising works in Cognitive radios. there are many researches are done, many still going on in Europe, Asia, and America, exploring various aspects of cognitive radios. In Jan 2010 first call over a CR network was made in university of Oulu using CRAMNET (Cognitive Radio Assisted Mobile Ad Hoc Network). 2.2 Cognitive radio With the development of wireless communication devices and technologies in WLAN and WAN spectrum is becoming scarcer. Low frequency bands which are near few GHz are very scarce and highly congested. In current wireless system we are using fixed spectrum allocation scheme. In fixed spectrum allocation scheme a part of spectrum is owned by an operator. Unlicensed users are not allowed to use that spectrum. This leads to the problem of spectrum scarcity. Survey has shown that more than 50% of the spectrum is underutilized. This is where Cognitive Radio (CR) is comes into picture. CR is introduced to solve the problem of spectrum sharing. Cognitive Radios actually scans the spectrum and during scanning it looks for spectrum holes. The main objective of the cognitive radios is to look for opportunities or white spaces in spectrum band as quickly and as much as possible. And when we say opportunity, opportunity could be in time or frequency domain. Also when we locate this spectrum holes opportunistically we also need to vacant the occupied spectrum as soon as primary user comes back. Here primary user means the users whose spectrum we are using (licensed user) and secondary means the unlicensed users. Cognitive radio is a pattern for wireless communication technology in which either a network or a wireless node changes its transmission or reception parameters to communicate efficiently avoiding interference with licensed or unlicensed users. These altered parameters are associated with the active monitoring of several factors in the external and internal radio environment e.g. radio frequency spectrum, user behaviour. Cognitive radio can be said as next generation of software defined radio (SDR). They are flexible in terms of their transmission characteristics in terms of frequency, bandwidth, ISP which makes smart decisions to configure the SDR at any point in time to achieve a particular goal. By combining these two technologies makes a radio intelligent and flexible and which helps to adapt it to the variations in the environment, user requirements as per the other radio users. Adaptation to changes and requirements should lead to highly reliable communication whenever and wherever required, while making efficient use of spectrum. Good cognitive radio uses analysis done for long period to know about the environment and also his own behaviour. There are various parameters taken into account to decide transmission and reception changes, we can distinguish certain types of cognitive radio. The main two are as follow: Full Cognitive Radio : It is also known as Mitola radio in which every possible parameter which can be observed by a wireless node is taken into consideration to take decision Spectrum Sensing Cognitive Radio: It is the type in which only the radio frequency spectrum is considered. And Depending on the parts of the spectrum available for cognitive radio, we can distinguish as: Licensed Band Cognitive Radio: It is the type in which cognitive radio is capable of using bands assigned to licensed users, apart from unlicensed bands, such as U-NII band or ISM band. Unlicensed Band Cognitive Radio: This can only utilize unlicensed parts of radio frequency spectrum only or the bands which are free to use. 2.3 About OFDM OFDM stands for Orthogonal Frequency Division Multiplexing. It is generally a type of Frequency Division Multiplexing (FDM) rather a special case in FDM. What makes it special is its orthogonal behaviour. Now the word orthogonal basically means mutually independence. When we say A is orthogonal to B, we mean that A has no vector in direction of B and vice versa or in other words A and B is mutually independent. Or the integral of two signals over one period is 0. In OFDM a single signal is first multiplexed and modulated independently to create orthogonal signals. This means the signal is first divided into number of smaller streams and then modulated further before transmission. For example imagine a slicing of cheese and grilling or cheese. Slicing is like FDM where whole data is sent in a bunch and grilling is like OFDM where the data to be sent is first divided into smaller data and then processed to transmit further like OFDM. Figure shown below is one more way to understand the concept of OFDM. On the left hand side is a big container which carry whole bunch of data at one time and take it to the destination. And on right hand side is four smaller containers where each carry smaller portion of data and take it to the destination. These smaller containers can be assumed as sub-carriers. And in case of OFDM they are orthogonal sub-carriers. The main advantage over here is that even if some of the cheese is lost during grilling, still we have not lost all the cheese. In OFDM input data with high data rate is first passed thorough serial to parallel converter. This parallel divided data is then modulated on individually. And parallel to serial conversion is done before transmission. This parallel divided data is our sub-carriers. These sub-carriers must be orthogonal. 2.4 Cognition cycle Above figure shows the rough model of Cognition Cycle. It reads the surrounding environment and makes decision accordingly. When we say decision we mean cognitive radio sense the requirement or urgency that may be in terms of changing a channel or churning from one technology to another depending upon the scenario. There are different stages where it observes the environment, learns it and then plans its action make required decision and then execute its plans. It is much like a radio with a power of thinking which was not been able before. The figure below shows the cognitive radio architecture suggested by Dr. Mitola. 2.4.1 Some important terms 2.4.1.1Wireless Environment/Outside world- It refers to a communication environment that includes any communication devices and the frequency bands they are working in. 2.4.1.2 Spectrum sensing- It is the technique used by cognitive radios to sense the spectrum. This action involves finding availability of white spaces or spectrum holes in the spectrum. 2.4.1.3 Spectrum Management- It involves catching the best spectrum available so as to satisfy user communication requirements. Cognitive radios should decide on the best spectrum band so that it can meet the Quality of service required for all available frequency bands, therefore these functions are necessary for Cognitive radios. These management functions can be classified as: Spectrum analysis Spectrum decision Spectrum Mobility: It is defined as the process when a cognitive radio device exchanges its frequency of operation. Cognitive radio networks target to use the spectrum in a dynamic manner by allowing the radio terminals to operate in the best available frequency band, maintaining seamless communication requirements during the transition to better spectrum. Spectrum Sharing: providing the fair spectrum scheduling method. One of the major challenges in open spectrum usage is the spectrum sharing. It can be regarded to be similar to generic media access control MAC problems in existing systems 2.5Cognitive Radio Challenges Three main problems experienced by CR are as follows: Interference (Mainly because of Hidden Nodes). Security. Control. They are described as follows: 2.5.1 Interference and the Hidden Node Problem Ideally while designing a CR we should consider that it does not have any impact on existing radio users, but in practically some impact is expected. If a particular user have non-cognitive radios, it is essential to study and make a note that how they would be affected by the interference of CR, mainly with respect to sharing resources such as spectrum, time, space etc. CR adaptive nature could be difficult to predict and thus making it hard to control the behaviour of a CR which will concern for user who faces CR interference issue. In communication industry the main concern about CR is the hidden node problem. This scenario arises when a CR is not capable to detect an interference with any of non-cognitive radios within its range, not only because of CRs own spectrum sensing is ineffective but also due to some non-cognitive radios are hidden. For example, if a transmitting contemporary user is not in the range from the CR, its transmission power may not be strong enough at the CRs location, it may be reduce than the noise floor which makes it more difficult to get detected. As the CR might not be able to detect a transmission by a contemporary user and similarly unaware of availability of the receiving by a contemporary user. Consequently, if it is confirmed as safe to use the contemporary users frequency and CR starts transmitting, at the contemporary receiving end it will create interference. The CR may have a limited view of spectrum provided from wide spectrum measurements which may cause interference with the receiving user. The localised spectrum view denotes that a CR should be potential to find transmitting user those are communicating below the noise level, since the strength of the received signal is very weak at the CRs location. Similarly a situation can occur where the signal attenuate by distance, thus user transmission is blocked by obstacles such as buildings, towers, hills or mountains. For example consider a CR in a valley would have a limi ted picture of the surrounding radio environment, as compared to that if it were located on top of a hill. 2.5.2 Security Concerns CR may be vulnerable to malicious effect, resulting into unexpected or problematic behaviour of individual CRs or complete networks. This problem springs up from the potential to re-program CRs in an unauthorized way. Hacking or placing a vulnerable code, virus on a network might enable criminals to steal valuable information from a CR through electronically, fool a network operator into charging others for services or achieve potentially widespread denial-of-service. A considerable amount of regulatory work will require to be done to clarify who would be responsible for the various security areas of CR, software developers, manufacturers, network operators and CR users themselves may all have a role to play. The CR security issue is closely related to that of SDR, which already discussed and hence not repeated here. Instead, a brief summary of the issues is given. Downloading software updates over an air interface poses some specific problems for security. Several digital signatures will be required for each piece of downloaded software in order to meet likely regulatory requirements. Exactly who is necessary to authorize software downloads must be standardized before any large scale deployment of over-the-air updates can be realized. 2.5.3 Burden of Control and Regulatory challenges A CR in reality will have some effect on different spectrum users the compliance of these new radios is likely to focus on a Policy module defined within a CR, which will determine the boundaries of CR behaviour. It is important while studying CR; to consider how users would not be affected by interference from CR devices and the exact operation and nature of a proposed CR policy system must be understood carefully. It is likely to include a detail case study of the specifications and characteristics of all the contemporary users for a specific CR or complete network of CRs may share the resources. The effort in controlling CR devices, it is necessary to ensure their behaviour is properly or not, even in the case of faulty or tampered devices, that measures are quickly implemented to intense problems. This will involve policies and standards which are created in a universal digitally interpretable policy, so that all CRs can understand the same. Monitoring techniques and powerful alg orithms are required to enable detection and identification of bad CRs and in this way it provides traceability to find or determine who is responsible for the issue. In addition to these challenges, spectrum regulators and spectrum managers will require providing access to licensed spectrum in such a way that is traceable, transparent and highly dynamic. If CRs are allowed to cover international territory additional effort will be required, due to the necessity to provide and collaborate cooperation with other countries. Assuming that acceptable control of CR policy behaviour is technically possible and feasible, it may turn out to be such a great burden that it will be simply not economically viable and the benefits of CR are outweighed by this burden. 2.6 Important Applications for Cognitive Radio are Downloading of audio and video files on mobile handsets. This application requires moderate data rates and near-ubiquitous coverage. Emergency services communications: It requires interoperability and a moderate data rate with local coverage. Broadband wireless networking: Very high data rate required but CR users have option to accept limited coverage, e.g. hot spots. Multimedia wireless and sensor networking: Broad range of data rates may be required. 2.7 Spectrum Sensing Spectrum sensing is the process performing measurements on the part of spectrum and on the basis of measured data making a decision related spectrum usage. As the requirement and quantity of users is getting increased day by day, it is necessary for ISPs to have large amount of spectrum in order to achieve the QOS (Quality of Service). This leads the interest in unlicensed spectrum access and spectrum sensing is vital concept of this. In a situation where there are licensed user and any unlicensed exists, licensed user (primary user) is to be protected and no unlicensed user can interfere any licensed users operation and such cases Spectrum sensing is also useful to detect the existence or non existence of a primary user. Spectrum sensing is an important concept for exploring spectrum opportunities for the secondary spectrum usage in real-time. It detects the unused spectrum and shares it without any noticeable interference with other users. It is an important requirement of the Cogn itive Radio in order to sense spectrum holes. Detecting primary users is the most efficient way to detect spectrum holes. 2.8 Spectrum Sensing Techniques Available Spectrum sensing plays a vital role in cognitive radios. And the type of spectrum sensing techniques to choose more or less depends upon the spectrum sensing technique. A method such as energy detection proves to be one of the simplest of all, but it doesnt works well at low SNR, varying noise levels, fading. On the other hand technique such as Matched filters shows better performance, but they comes complex receiver design. We are going to discuss some of these techniques as we proceed further. 2.8.1 Matched Filter Technique This is the technique which takes minimum amount of sensing time. In this method of spectrum detection, receiver receives a pilot signal along with the data that is sent by the transmitter. A pilot signal is a single frequency that is used for synchronisation. All the secondarys those are struggling for spectrum should have knowledge of this pilot signal. There should` be tight timing synchronisation between primary and secondary. They are also required to know about the kind of modulation being used, pulse shaping. Also secondarys must have another receiver for every primary. This kind of techniques also fails when there is frequency offset. Examples of this technique are TV signals, CDMA with pilot, also used in OFDM. 2.8.2 Energy Detection technique This is the most simples of all techniques. In this the receiver has no knowledge of the transmitted signal. The receivers need not to have knowledge about the modulation type or any kind of pilot signal. Earlier energy detection was done with the help of a LPF (Low Pass Filter), Digital to Analog converter (D/A), and square law device that used to calculate the energy of the signal. Later it is done by making use of fast Fourier transform (FFT). This is known as periodogram method in energy detection. 2.8.2 Cyclostationary Feature Detection Signals are modulated with sine waves or cyclic prefix as in OFDM. And they are periodic. This periodic property of a signal helps it to be cyclostationary. This technique basically uses this principle of spectral correlation to detect the spectrum. Even if signals have similar PSD (Power Spectral Density) but they have do not have similar spectral correlation. 2.9 Multi-resolution for Cognitive Radio Sensing The concept of multi-resolution for Cognitive Radio can be applied with different methods but, the basic idea is the same. The whole spectrum is first sensed by using a coarse resolution. After this first step fine resolution sensing is done on a part of interested bands. In this way CR avoids itself from sensing the spectrum at one time and thus saving time and power. In this way, the sensing time is reduced and the power also been saved from unrequited computations. Also the multiple antenna architecture helps parallel processing and enables to reduce the sensing time. But, it increases the chip area and consumption of power which is not desirable. Also for coarse resolution sensing the mixer has to produce many frequencies and Also it should switch to one frequency for beginning the fine resolution sensing. If the signal is low pass signal then we can use fine resolution to scan the whole spectrum. Because low pass signal has low center frequencies and its sampling is doable. But for pass band signals it is not feasible to scan the whole spectrum. Because, for example say if we have some signal with center frequency of 850 MHz, it is not practically possible to do sample that signal. As according to Nyquist theorem sampling rate should be at least twice that of center frequency. Therefore it is practically not possible to sample a signal at 1600 Mega Hertz. 2.10 Business Model for Spectrum Sensing So far we have discussed about Cognitive radios and spectrum sensing in details. Since this is telecom, and telecom involves huge capital investment. One of the most costly things in telecom is getting the license itself and then comes the infrastructure and installations etc. Currently most of countries work on static spectrum allocation basis. For spectrum sensing to work we need some kind of regulation or set of rules that all will be ready to work with. A team from Brussels University has suggested a model for the same. The same model is discussed in brief below. This model is divided into four main categories. i. Ownership- Ownership simply means the ownership of license. One who has license is authorized to use particular band of spectrum. And if another licensee wants to share a spectrum then it will depends on parameters discussed below. If the operator is unlicensed then there is now issue of ownership. ii. Exclusivity- Exclusivity means whether or not a particular operator is exclusively assigned a band of spectrum. That will be issue of regulator to decide to exclusively assign a spectrum to a specific user. If it is assigned exclusively then nobody can access that band of frequency, and if not then those bands of frequencies will be available for sharing. iii. Tradability- Tradability means whether or not a terminal is allowed to switch between frequencies from different operators. If tradability is permitted frequency band or bands can be auctioned for sale or given on lease. iv. Neutrality- It is possible that some of frequency bands can be accessed by number of RATs (radio Access Technology) or may be limited to a particular RAT. If frequency bands are not available to number of RATs then that band need to address more issues, such as setting technical conditions to access the band and coordinating the cooperation between multiple technologies. Unlicensed: Unlicensed deals with the band of frequencies which are free to use, like ISM band. Common example for this is Wi-Fi which operates in 2.4GHz. This band of frequency is available to all and there is special condition to access this band. Single RAT Pool: This pool is related to a group of licensees which are not exclusively assigned any band of frequency and using same RAT. Multi RAT Pool: It is similar to Single RAT Pool except that it has multiple RATs. Single RAT Market: In this each operator is assigned with a separate frequency, but that can be accessed by the conditionally secondarys. Multi RAT Market: In this the operator is a licensee and is exclusively assigned with a band of frequency, and also with tradability. Flexible Operator and Static Spectrum: If a particular band of spectrum is exclusively assigned to an operator and without tradability. And if there is only one RAT, then it is known as Static Spectrum else Flexible Operator. 2.11 Survey outcome As per the literature review we concludes to use Energy detection technique for spectrum sensing as it is the fastest spectrum detection technique available and also it is simpler as compared to other techniques. There are many researches done in this field and many are still doing. Because of the survey we get knowledge about various techniques available in market. This led us to do a simulation model with one of the spectrum sensing technique. Now as far as selection of spectrum sensing technique is concerned, we selected Energy detection technique. The same could be seen in next part of the thesis which includes its design and implementation in simulation model. Chapter 3 Simulation Design 3.1 Sampling and Its Importance Sampling is a process of converting the continuous analog signal to a discreet analog signal and the samples signal is the discreet time representation of the original signal. If the message is coming from a digital source, then it is in the form to be processed by digital communication systems. But in real life not every signal is digital, message signal can be analog. In situation like these, we have to first convert the analog signal into discreet time signal, this is sampling. For this process to work well, sampling rate should be selected carefully or in other words it should satisfy Nyquist criterion. And Nyquist Criterion says that the sampling frequency should be at least twice the maximum frequency in signal. Fs 2fmax or T=1/ fmax Where Fs is sampling frequency, fmax is maximum frequency in the signal. T=Sampling period. Sampling is like reading a signal in analog form and taking its value at that instant of time. So more the samples we take better the resolution of the signal and, signal can be recovered more accurately. But if we take less number of samples, then resolution of the signal decreases. If we go on reducing the sampling rate, then times comes when it is difficult to recover the original signal from the sampled signal or in other words original information in the signal is lost. This is also known as aliasing. Aliasing is the effect which takes place if the signal is sampled less than twice the maximum frequency. 3.2 Types of Signal 3.2.1 Time limited signal- It is a signal which exists for only certain duration of time. Out of this duration, signal does not exist. A rectangular pulse of duration T seconds can be considered as time limited signal. x(t)=A for 0tT and x(t)=0 .otherwise 3.2.2 Band Limited signals- It is a signal which has a frequency spectrum which exists only over a certain range of frequency. The value of signal outside this range of frequency is zero. Mod(X(f))=A .-BfB and Mod(X(f)) =0 .otherwise. 3.3 Sampling Of Low pass and Band Pass signal Low pass sampling theorem states that- a) A band limited signal of finite energy, which has no frequency components higher than W Hertz, is completely described by the specifying the values of the signal at instants of time separated by 1/2W seconds and b) A band limited signal of finite energy, which has no frequency components higher than W Hertz, may be recovered from the knowledge of its samples taken at rate of 2W samples per seconds.[J.Chitodes] Band Pass sampling theorem states that- A Bandpass signal x(t) whose maximum bandwidth is 2W can be completely represented into and recovered from its samples if it is sampled at minimum rate of twice the bandwidth. Figure 3.4 shows us the spectrum of low pass signal and its spectrum after sampling. Low pass signal are the signal which works well under Nyquist criterion (Fs 2fmax) without any special alteration. There is another type of sampling known as Band-pass sampling. This is the type of sampling applied to a high frequency signals or the signals which cannot pass through low pass filters. These signals have high frequency, normally in 100s of mega hertz. Here we cannot use Nyquist theorem directly. As practically it is not possible to sample a signal at such a high frequency. So what we do is, we represent the signal in terms of inphase (I) and quadrature (Q) components of a signal before sampling. This I and Q component is made by multiplying I and Q with sin(2*fc*t) and cos(2*fc*t) respectively. We can also say that we are actually moving a window of size of the bandwidth over the center frequency of the signal. In our Matlab code we have used low pass sampling even though the frequencies are quite high, because it is not a practical model but a simulation model. In low pass sampling we sample the whole available while in band pass signal we sample a window of bandwidths. 3.4 Design Specifications Our design specification deals with requirement for measuring the center frequencies in the spectrum and calculating the spectrum hole or white space. Figure 3.6 shows a spectrum with two signals in it. Measurement of the center frequency is shown in Generation of White Space. Since we have used a low pass sampling our model will scan whole spectrum and try to locate spectrum holes within it. And these holes are located with energy detection on basis of a threshold. Our model to work well we need more than one signal in a spectrum. 3.5 Generation of White Spaces 3.5.1 What are they White spaces are basically the bands of frequencies that go unused. They are also known as spectrum hole. From the name spectrum hole, it suggests they are the holes in the spectrum, which could be filled if they are used properly. In todays communication world, most of countries works on static spectrum allocation basis. That means a particular operator will have a dedicated band of frequencies, no matter whether he uses it or not but it will be reserved for that operator as they have paid for getting the license for that from the government. In this case, if we think of bigger picture and scan the whole spectrum for a particular duration of time say one day. We will find that there are lot of frequency bands which are not fully utilized. These some of unused bands are known as White Spaces or Spectrum Holes. 3.5.2 Factors responsible for creation of white spaces White spaces get created because all the bands in the frequency bands in the spectrum are not used efficiently. Because we have different technologies working in various bands of spectrum but we do not have any practical implementation on large scale of any radio to work on whole spectrum at same time. 3.5.3 How they can be avoided It is difficult to avoid all the white spaces. But we surely can reduce it to some extent. And for that we need a special radio which can work on whole spectrum. Radio which is smart enough that could take important decisions without any human interference. This is where cognitive radios come into picture. But besides the radio, it also needs some set of rules or some regulation to make it work. Keeping this in mind the same has been discussed in Business Model foe Cognitive Radios in Chapter 2. 3.5.4 Regarding this Thesis As far as this Thesis is concerned we are taking help of Simulation to show spectrum sensing in Matlab. And the technique which we used for that is Energy Detection technique. Now to show a spectrum we first need multiple signals in our spectrum. Those signals are the OFDM signals. And the frequency gap in between those signals is our white spaces. To show spectrum sensing it is important to create this white space. We have tried not to use the frequencies which are too high or too low. We have tried to make complex calculations looks simpler for easy understanding. 3.5.5 Parameters/Variables Used Number of carriers is denoted by variable k. Tu is useful OFDM symbol period. T is baseband elementary period. G is cyclic prefix. And total symbol duration is Ts which is equal to delta+G, where (delta= g*Tu). As said before we are using 2N-IFFT, so IFFT/FFT length FS is 4096. Rs is the simulation period. Carrier to elementary period ratio is q is 10. Carrier frequency fc = q*(1/T). As we want to add two signals later we have kept our sampling frequency of whole system as Sf. Sf = 700 MHzs. 3.5.6 Calculations for OFDM signal 1 For signal 1: Tu= 100 *106 sec. Therefore, T=Tu/2048 = 48.8281*10-9 sec. fc=q/T = 204.79*106 Hz This is the center frequency for OFDM signal1. And, Rs=4*fc=819.199*106. Carrier spacing = (kmax * (kmin-1))/Tu = (1705*1704/100*10-6) = 29036.16*106 Spacing between two carriers = 29036.16*106 / 1705 = 17.03*106 Hz. Now, we are having total 1705 symbols that are transmitted with a rate of T/2 seconds to IFFT block. That is, one symbol is transmitted every T/2 seconds. As we are using 4-QAM, it means we are using 2 bits per symbol. That is, two bits are transmitted every T/2 seconds. Therefore, one bit every T/4 seconds. So, the bit rate for OFDM symbol 1 = T/4 = 122.07*10-6 seconds. 3.5.7 Calculations for OFDM signal 2 For signal 2: Tu2 = 80 *106 sec. Therefore, T2=Tu2/2048 = 39.06*10-9 sec. fc2=q/T2 = 256.00 * 106 Hz This forms the center frequency of OFDM signal2. And, Rs2=4*fc2=1024.00*106. Carrier spacing = (kmax * (kmin-1))/Tu2 = (1705*1704/80*10-6) = 36295.2 * 106 Spacing between two carriers = 36295.2 * 106 * 106 / 1705 = 21.28*106 Hz. Similarly to case 1 bit rate for OFDM signal 2 is calculated as, One bit is transmitted every T2/4 seconds. So, the bit rate for OFDM symbol 2 = T2/4 = 9.765*10-9 seconds. And from our code, to change the center frequency we just need to alter Tu (useful OFDM symbol period) or the sampling frequency Sf. For Tu as 100 micro seconds and 115 micro seconds we are getting OFDM signals with center frequencies around 200 MHz and 265 MHZ respectively. In this way we have created a white space of around 40 MHzs. In this chapter we found the center frequency measurement technique which is followed by results analysis in the next part of our thesis. Chapter 4 -Simulation and Result Analysis 4.1 Introduction So far we have seen how cognitive radios work. Cognitive radios are not only for research but it is a need of todays communication system. Moreover cognitive radios are more reliable than the traditional radios. We have also discussed the role of cognitive radios in sensing the spectrum, various methods used for spectrum sensing. In our thesis we have explained many spectrum sensing techniques like matched filter, energy detection, cyclostationary features. Cognitive radios are simple extension of software defined radios. But it is flexible characteristics of frequency and bandwidth and Intelligent Signal Processing (ISP) as an add-on. With the help of it makes smart decision at correct time. Now cognitive radios and ISP generally means with the physical layer but not compulsory, ISP can be installed at higher levels too. For CR to get the smartness it needs this ISP. Of all the above spectrum detection techniques discussed we found that energy detection is the simplest one and one of the fastest technique available for spectrum sensing. Hence we have tried to show simulation for spectrum sensing by using energy detection technique. Simulations are done using Matlab. Matlab Code (m.file) is supported with sufficient comments when needed for better understanding. In this chapter we have tried to explain the output of the system at various points. Orthogonal Frequency Division Multiplexing (OFDM) is well suited for cognitive radios because of its robustness. OFDM can provide large data rate even in impaired channel. For decades there has been a lot of research done in the field of OFDM. OFDM is basically a bunch of large number orthogonal waveforms which does not overlap with each other (as they are orthogonal). OFDM consist of subcarriers which are narrow-band and these subcarriers are transmitted in parallel while transmission. OFDM is good with handling multipath interference. Multipath interference gives rise to frequency selective fading and Inter Symbol Interference (ISI). Because OFDM has narrow band we get flatness in channel which helps to overcome frequency selective fading. Modulation of symbols in OFDM is done at very low rate, this makes symbol much longer than our channel impulse response, and this in turn helps to overcome ISI. That is one of the reasons why we have chosen OFDM for our simulation. In our Matlab code we have generated two OFDM signal, both with different centre frequencies. This two signals acts like the signals transmitted by two different transmitters and they met up in air. So we have added these two signals. Now signal can be considered as the signal received at the receiver end of the system, as we have not considered noise in our system. Then we have found the energy of this added signal and calculated its energy. 4.2 Simulation Analysis of OFDM signals 1 and signal 2 We want the OFDM spectrum should be centered on frequency fc. And to get that we are using 2N-IFFT to get the spectrum centered at fc. The elementary period of the OFDM is considered to be T/2. The symbol duration Tu is considered using 2048-IFFT; hence we will be using 4096-IFFT in our code. Figure 4.1 shown below is the block diagram of a typical OFDM system. The elementary period T is defined for baseband signal, whereas we are going to perform the simulation on pass-band signal. For this we need to relate elementary period T to the time period of 1/Rs which should be at least double the carrier frequency. Input data is being created using rand function. The numbers generated by this function is decided by the internal state of generator. This function generates a stream of random numbers which are distributed uniformly. Also note that the state of rand function is set to 0 (rand(state,0)). By setting the state of rand function to state zero resets the generator to a same fixed state. Hence we get same results every time. If we do not set the state to zero then we will get unique set of result every time we run the program. It would be better programming practise to set the state of rand function because Matlab reset the state at every start-up. With the help of rand function Kmax+1 complex numbers are generated and stored into variable a. The variable info forms our actual input data to the system. This variable has 4096 points, in which zeros are padded at the beginning and at the end 853 points. Zero padding is done to avoid symbol overlapping or aliasing. M=Kmax+1; rand(state,0); a=-1+2*round(rand(M,1)). + 1i*(-1+2*round(rand(M,1))).; info =zeros(FS,1); info((FS-((A/2)-1)):FS) = [ a(((A/2)+1):A).]; info(1:(A/2)) = [ a(1:(A/2)).]; carriers=FS.*ifft(info,FS); The Below figure shows the real and imaginary part of the signal carriers which forms our input signal. We can also notice that signal carriers uses time period of T/2. (a) OFDM Signal 1(b) OFDM Signal 2 (a) OFDM Signal 1(b) OFDM Signal 2 The purpose of zero padding is to assure frequency domain symbols are communicated in orthogonal sub channels. The length of the cyclic prefix is to be kept at least as long as impulse response of the channel at the receiver. Due to sharp transitions OFDM signal causes spurious emission which in turn leads to attenuation and thus further lengthening the impulse response of the channel. This is then followed by an IFFT block which performs IFFT on the signal info. At its output we get a signal carriers which is an IFFT of info with 4096 points. Signal carriers is plotted in time domain and frequency domain in figure 4.1, 4.11 and figure 4.2 and 4.12 respectively. We can notice that signal carriers has time period of T/2 and signal carriers is a baseband signal. To plot the signal in frequency domain pwelch function is used. pwelch function gives the power spectral density (PSD) of a signal by employing modified periodogram method. The output of the IFFT block is then fed to the reconstruction filter or low pass filter. Filter filters out the frequency components out of band and only passes frequencies which are in band. The signal carriers is sent the through the filter g(t). (a) OFDM Signal 1(b) OFDM Signal 2 Below shown is signal carriers after pulse shaping in time domain. (a) OFDM Signal 1(b) OFDM Signal 2 (a) OFDM Signal 1(b) OFDM Signal 2 Signal carriers after pulse shaping in frequency domain.For reconstruction filter we are using bandwidth as Rs and time period as 2/T. Therefore we have (2/T=40.95 MHz) 17 MHz = 23 MHz (for OFDM signal 1) and (2/T2=51.20 MHz) 17 MHz = 34.20 MHz (for OFDM signal 2) as our transition bandwidth for the filters. At the output of filter we get periodic frequency response as required by discreet time system as seen in figure 4.6 and 4.16. Now, in our code the signal carriers is used to produce signal chips which is then convolved and pulsed shaped to form a signal dummy and u. In Matlab convolution is similar to multiplication of two signals. The signal u is plotted in time and frequency domain in figure 4.4, 4.14 and figure4.5, 4.15 respectively. The signal u is the passed through a filter. As a filter we used Butterworth filter of order 13 with approximate cut off frequency of 1/T. Figure 6 shows the filter response. (a) OFDM Signal 1(b) OFDM Signal 2 Response of Digital to Analog Filter. In our case we are using Butterworth filter of order 13. And figure 4.9 (a)/(b) and 4.10 (a)/(b) shows the out of filter uoft in time and frequency domain. (a) OFDM Signal 1(b) OFDM Signal 2 (a) OFDM Signal 1(b) OFDM Signal 2 Signal output after filtering in frequency domain. Lastly we do Up-Conversion on the signal. Up-Conversion actually converts the baseband OFDM signal to an IF (Intermediate Frequency) signal, so that the signal is ready for transmission. It also minimizes the impulse response duration of the OFDM signal. Input to the Up converter is stream of baseband symbols. Till now we got I and Q. Now this I and Q are modulated with sin () and cos () and then finally added and then transmitted. Where = 2*fc*t. below figure show time response of our OFDM signal. (a) OFDM Signal 1(b) OFDM Signal 2 (a) OFDM Signal 1(b) OFDM Signal 2 These baseband symbols are sampled at baseband sampling rate. Each symbol takes one of the M complex values. The value of the complex number and M forms the basic parameter for modulation. For example, 16-QAM will have 16 different complex numbers on complex plane or signal constellation; 4-QAM will have four different complex values. Up conversion is also necessary as, for the frequencies which are in Giga Hertz (GHz) traditional signal processing devices do not perform well and transistors become unstable. And one more reason for that is, it is difficult to implement amplifiers and filters that can be tuned to different frequencies, rather it would be much easier to implement a tuneable oscillator. This gives us the simulation analysis of OFDM signal 1.Generation of OFDM signal 2 is similar to OFDM signal 1. The only change we have done is in Tu (OFDM period). In first case Tu is 100 micro seconds, while in second signal Tu is 80 microseconds. This gives us OFDM signal 1 with center frequency as 42 MHz and OFDM 2 signal with center frequency 85 Mega Hertz. By creating OFDM signal 1 and OFDM signal 2 we have managed to generate two frequency band in a spectrum which we will using to testing the spectrum sensing. These to signals are transmitted in air and at the receiver we will be receiving another signal which will be the addition of these two. To keep our code simple we are not adding noise to our system. In future we plan to study the simulation of our system with noise. So in next part of our code we add these two signals. Signal s_tilde from OFDM signal 1 and signal s_tilde2 from OFDM signal 2 is added in time domain. (a) OFDM Signal 1(b) OFDM Signal 2 This added signal has real as well as imaginary components. So we remove imaginary parts by taking only real part of the signal and using it for further analysis. This real part of the added signal is then plotted in time domain and frequency domain. Next task is to sense the spectrum. For sensing the spectrum we are using Energy detection technique. In which we basically we sample the whole spectrum and take energy at each time sample. This energy which is taken at each time sample is then compared to a threshold. (a) OFDM Signal 1(b) OFDM Signal 2 If the signal has energy beyond threshold then decision could be taken as that band of spectrum is occupied or not available, and if detected energy is less than the threshold then we could say that a particular band in a spectrum is available, which can be seen in above figure. Now setting this threshold is an important task for this technique to function better. Energy detection technique is no doubt one of the fastest spectrum sensing technique available, but we must recall that according to basic definition of cognitive radios, it should not only sense the spectrum fast but also need to be accurate. And for our technique to be more accurate we can employ some more techniques with energy detection which are discussed above. But in our code we have tried to keep it simple, so the threshold is decided by (maximum energy +minimum energy)/2. This looks simple and it is effective too. This chapter showed us the results of our model. With this we end this chapter and take a step forward towards some future work we had in our mind while doing this thesis. Chapter 5 Conclusion The main aim of this thesis was to understand Cognitive radios, spectrum sensing and to provide a basic simulation tool for future work. Spectrum sensing and Cognitive radios are discussed in details and simulation is performed using Matlab. Various spectrum sensing techniques have been discussed, and simulation is done using Energy detection Technique, because it is one of the fastest detection technique and also simplest of all. Mean value of energy is taken as the threshold for spectrum sensing. However we have not considered noise in our system for simplicity, but it cannot be ignored in real time systems. And with this we conclude our thesis, but we still need to keep in mind that more work need to do in Cognitive radios. Chapter 5 Future Work This thesis will form a basic tool for any further research in the field of spectrum sensing or cognitive radios. Currently we are able to detect the spectrum roughly, in future we would like to sense the spectrum with more accurate spectrum sensing techniques. Also we intend that our receiver will sense he spectrum and will give a feedback to the transmitter. This feedback will give information about the white spaces or spectrum holes in the spectrum and then transmitter will adjust its parameters (in our code we can do that by adjusting Tu Useful OFDM Period) and then try to use the spectrum available. Currently we have not taken noise into account. If we consider noise and feedback from receiver, then a complete cognitive radio system will be ready.

Personal Academic Goals Essay - 693 Words

Personal Academic Goals Life is a continual learning process, which requires a strong method to develop better ways of apprenticeship. Personally, being able to obtain a higher education gives me an opportunity to be better in many ways. Everyone should have any personal goals in life in order to survive, prosper and succeed in every journey that life gives. As for me, being a University of Phoenix student, I hope to achieve all of my goals on which I have been trying to pursue and obtain through the years. They are goals that I believe I need to have to be a successful member of the society, and through attending the university I also hope to gain a more positive image of myself, build my personal growth, along with achieving†¦show more content†¦As for my employer, my leaders have every intention to encourage me to align my personal life, which is school, with my professional life. Also, encountering new people will provide me with the opportunity to improve myself as well as to help others wit h their improvement. By taking advantage of my employers Tuition Assistance Program I believe that both my employer and I will benefit from my continued education. Bachelors of Science in Business concentrated in Information systems through the University of Phoenix will open me a new world of successfulness, and I feel that school and my employer will help me to be able accomplish my goals. Meeting new people at every class will allow me to have the opportunity to expand my horizons. In addition, moving on into new learning adversities will also open new doorways in the world of competitiveness, and also will challenge me to get to another stage of my life. Looking for new areas of personal development being backed up by a title and away from getting some extra digits in my paycheck will help me to strengthen my values and criteria toward this challenging world. 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Charlie Bird free essay sample

Did the drugs sake Charles Jazz what it was or did the man have the built in ability to squeeze the perfect notes out of a saxophone making it do his will without hardly having to give it a thought. On August the 29th In the year of 1920 a baby was born to a family In Kansas City. Kansas. The childs name was Charles Parker Jar. He was the newborn son of Adelaide (Eddie) Bailey Parker, who was African-American-Choctaw, and Charles Parker, Sir. , an African-American. His mother migrated to Kansas City from Oklahoma where she met Charles Parker Sir. Charles Sir. Ad been In Mississippi and Tennessee and had mom to Kansas to pursue a career as an entertainer. Charles Sir. And Eddie separated leaving Charles without a father figure. Charles Sir. Never realized his dream of becoming an entertainer and is reported to have been working on a train as a waiter or chef when he died. At the age of 15 Charles began to show a great interest In music. He Joined the school band where he was given an alto horn but soon switched to the baritone horn and soon developed a love for the alto saxophone. His mother had more idealized views of Charles academics then those that are given by the school and friends.A Fellow Student, Lawrence Keyes was quoted as saying, If he had been as conscientious about his school work as he was his music, he would have become a professor, but he was a terrible truant He was doomed to be a perpetual freshman. ( CTD. In Charlie Parker, His Music and Life 4 The result of this initial burst of curiosity was that Charlie began pestering his mother to buy him an instrument of his own. (Priestley 12)His mother purchased a used saxophone from the local pawn shop for forty-five dollars and had it overhauled. Charles soon lost interest in the horn and loaned it to a friend.His friend had his saxophone for around two years before he decided to get It back. During this time Charles frequented Kansas Clues bars and clubs taking advantage of the Jazz scene and soaking in the artists styles and sounds There are many references in available literature stating how Charlie would sit in with any band or group of musicians, wherever and whenever there was an opportunity. (birdlimes. Co. UK). Most of the time he would have to hang around outside of the clubs because he couldnt get In. Doing this exposed him to a vast array of professional musicians, some of which would exposed to marijuana, and pills.He has been quoted when talking about his introduction to drugs saying It all came from being introduced too early to night life. When youre not mature enough to know whats happening-?well, you goof. (CTD. In Charlie Parker, His Music and Life 7) He talked about his his introduction to heroin to a bassist by the name of William Buddy Jones. He told him that at the age of fifteen he got high from heroin for the first time. Buddy retells the event, Getting high for the first time at fifteen, Bird told me what he felt. He pulled out $1. , which was worth more in those days and he said, Do you mean theres something like this in the world? How much of it will this buy? (CTD. In Charlie Parker, His Music and Life 8) From the age of thirteen drugs play more and more of a role in Charles daily life. Charles began to play with a band called the Deans of Swing and did so for about a year and a half. During this time he became close friends with a man by the name of Robert Simpson. Simpson was an older gentleman not unlike most of the people Charles liked to be around. Lawrence Keyes claims that Charles worshiped Simpson, and was with more often then not.Shortly after the Deans broke up at the age of twenty-one Simpson died, and Keyes claims that Charles was a complete wreck afterwards. This event helped to spiral Charles farther down the path of his drug addiction. Charles married Rebecca Ruffian on July the 25 of 1936, a girl whom he met in 1934 when she, her mother and her siblings boarded a room from Charles mother. When Rebecca was three months pregnant with Charlies first child he called her into their room and asker her to sit down. Rebecca had no idea what Charlie was doing until she saw his reflection in the mirror injecting himself in the arm.He convinced her that he had to take heroin to alleviate the pain from a wreck he had recently been involved in that broke three ribs, and fractured his spine. She never seemed to learn the truth about his history with heroin or chose to ignore it and believe what he had told her. 1936 was a transitional year for Charles, his technique developed and so did his love for drugs. The wreck that had injured Charles so badly had happened on his way to the Ozark Mountains where he was to play a Thanksgiving Job. Charles continued afterward taking Jobs in the Ozarks. He often played with a saxophonist named Tommy Douglass.Douglass helped Charles develop some techniques such as passing cords and the woodwind technique. Trumpeter Clarence Davis later used his armature disk recorder to make the first recordings of Charles. Charles was away from Kansas City for an extended amount of time during this summer and when he returned he was the most popular player there. In 1937 Charles met a man by the name of Jay McMahon, who was a pianist. These two artist would soon find themselves working together. McMahon was was the pianist of a band formed by Henry Buster Smith, a 12 piece or sometimes smaller ensemble. Buster invited Charles to Join. Charles had a fairly close relationship with the older McMahon He used to call me his dad, and I called him my boy. (CTD. In Charlie Parker, His Music and Life 12). Buster helped Charles Jar with his improvisation and his sound. Buster was quoted saying that Charles was an apt pupil. He would have breakthroughs in his music but not be able to follow up on them, and they would be lost. He had an affair on Rebecca and then later held a gun to her head trying to get back some letters between himself and his mistress.He had to leave the band he had been playing with because of his drug habit, and then he had run in with the law. One night he kept a taxi for several hours running up a bill for $10 that he could not pay. When the taxi driver decided he was going to take Charles horn for payment he was stabbed. Charles went to Jail. From this point Charles went to New York for some period of time. Doing so he stopped in a club while passing through Chicago called the 65 Club where he met singer Billy Stickiness. Stickiness would later become the leader of Charles big band.Charles finally made it to New York and found his way to Busters place where against his wife will he allowed Charles to stay with him at his apartment. Buster reported that he did not know how Charles got there but he sure was in sad shape. While living With Buster, Charles had to resort to working odd Jobs, cleaning bars and washing dishes until he met pianist Art Datum. Its believed that Datum had an influence on Charles even though Charles never mentions him as one because after this time of his life he began to use some of Tatums techniques. The technique they shared was known as side-slipping or playing out of key. Between late 1937 and 1939 Charles played at many clubs and dance halls form The Parisian, to Clark Monomers Uptown House. Charles Played in many Harlem sightless soaking in many different pop songs, sounds and styles. In 1937 Charles had his next big break through. While playing one night with a guitarist named Biddy Fleet he figured out how to play the sounds he had often said that he could hear but couldnt play, He found that by using higher intervals of a cord as a melody line and backing them with appropriately related [chord] changes, he could play this thing hed been hearing. (Woodcock 17). This along with Charles Ozark mountain breakthrough propelled him through the next five years of his life but little is known of his activities throughout the rest of 1939. Biddy Fleet claimed that Charles would disappear for weeks at a time probably due to his drug habit. Charles returned to Kansas in 1940 with valuable experience and soon reestablished a connection with McMahon and Joined his band. It was with this band he made his first commercial recordings. McMahon had taken Charles into the band thinking that he was off heroin which he soon found out was not the truth.Despite the fact that Charles was still a Junkie he and the band soon became a family. This was the first time Charles felt accepted by his peers. Some say that the band spoiled Charles by over looking his habit and unreliability. When Charles heroin habit would begin to show itself to badly McMahon would make him take a few days off. Gene Ramey said that the band was motivated by Charles when his drug addiction was under control, he was quoted saying, The Jay McMahon Band . .. was the only band Ive ever Know that seemed to spend all its spare time Jamming or rehearsing El this was inspired by Bird, because the new ideas he was bringing to the band made everybody anxious to play. (CTD. In Charlie Parker, His Music and Life 19) It was during times like this that Charles Addiction seemed to subside and the music took ore control over his life. Likes of Dizzy Gillespie and helped in the beginning development of Bebop. Dizzy formed a combo with bassist Oscar Petrified and began to play steady gigs at the Onyx Club. Dizzy had sent Charles a telegram and invited him to Join but it would seem that he did not receive it and missed out on the first steady gig for a bebop band.Soon after that he moved along to form the first Bebop Big Band. It was during this time that Sarah Vaughan began to notice that Charlie had taken an interest in classical music. She said he would listen to something on the bus and then get on tag and play it, his way. Charlie soon left the Big Band because he felt that it lacked individual freedom. Charlie now without a full time band went back to playing whatever gigs he could get, however he continued to play with Dizzy whenever he had the opportunity.In 1945 Dizzy formed a quintet to work several nightclubs on fifty-second street in New York. The band members often changed but the front line was always Dizzy and Charles. Dizzy being the more stable of the two was normally the first name on the bill. This sometimes made Charles Jealous of Tizzys popularity and its unclear if he new that it was because of his drug addiction and inability to handle himself in a professional business like manner. In the fall Dizzy dissolved his big ban and received and offer to play in Billy Bergs Nightclub in Los Angels. Even though Dizzy knew about Charles habit and it related reliability issues he took Charles as his partner once more. This began one of the most tragic times in Charles life. Dizzy was contracted to take 5 men to California to play an eight week engagement. Because of Charles issues he took a stand in for the inevitable times that Charles would be missing in action or passed out somewhere unable to play. Dizzy did not want the management on his back because of Charles. Charles was even more unpredictable in California due to fact that it was harder to get his hands on his heroin there.This is when the infamous photo of Charles was taken where he looked so strung out that he couldnt hold his head up and the guys standing next to him where holding him upright. When the eight week engagement was over and it was tie to fly back to New York Charles could not be found. Charles ended up cashing in his plane ticket and staying n California due to his addiction. While on his layover of sorts in California Charles got to play with Miles Davis at he Finale Club. When Charles heroin dealer was arrested in Los Angels he spiraled out of control. He began to drink heavily to alleviate the withdrawal symptoms he was having.Charles became missing until Howard McGee found him. He was living in a garage that had been converted to a room but was lacking heat, at which time McGee took Charles in. From this time on Charles had nothing but problems. Deteriorating health due to alcohol and drug abuse began to make him have more then reliability problems. In a recording session with dial records, Charles begin to shake, he was barely able to blow his horn, and had muscular spasms. Not long after he made it back to his hotel by taxi he was picked up by the police and taken too hospital because he was walking around nude.There were also several reported accidents where he had set hotel rooms on fire. Charles was assigned six months at a state hospital by the Judge that heard his case. In 1946 Ross Russell got Charles out by having him transferred to 1949 Charles had become angry with Russell. He claimed that Russell refused to get him released until he agreed to renew his recording contract. He was also upset that Russell released the recordings from the day he had his spasms, and lost his mind. Parker even said at some point that the recordings of that day were his worst recordings of all time.After Charles had been released he played at the Hi-De-Ho Club in a band that was extensively recorded. During this time Just after his release he sounded as if he was back to his best. Charles also recorded two more releases for the Dial label before returning to New York where he stayed until his death. When Charles returned to New York he was taken in and cared for by two women that were important in his life, Doris Sydney and Chant Richardson. He married Doris in 1948. Charles was now a well known recording artist. He was also sought after as a band leader.Charles health was now the best it had been since his teenage years. Although he appeared to be stable he was still dealing with feelings of chaos in his life Charles soon returned to his heroin and drinking. Back on his drugs of choice Charles got together a quintet, his main unit from 1947 to 1950. The quintet rarely changed members and had great continuity. A really nice quote from Charles about music Music is your own experience, your own thoughts, your wisdom. If you dont live it, it wont come out your horn. They teach you theres a boundary line to music. But, man, theres no boundary line to art. (whom. Chem.. . Com) The quintet did some recording for the Savoy label which became its documentation. The quintet is considered to be Charles best work, and recordings of them continued to turn up even after his death. Charles managed to keep a strong stage presence even with his Heroin habit for the most part but from time to time it began to show. In 1948 Charles was so high and drunk that he relived himself in a public telephone booth in a club the quintet was playing at resulting in he band not getting paved for the gig. In 1949 Charles was performing a live broadcast in which he was to do a solo from Tizzys Grooving High.Charles wasnt able to play the notes due to his diminished physical and mental state. Kenny Dirham had to carry the group after Charles failed on the solo and then continues to miss notes and drop in and out of the performance. In 1950 Charles and Doris divorced. Doris was Charles third wife and couldnt take the stress of Charles drug addiction any longer. Charles then moved in with Chant Richardson, the two never married but she did take his name. Charles considered Chants daughter his own and they had two children of their own together. This year also brought about the breakup of the quintet.Charles was booked to play a gig in Denmark and tried to get off heroin long enough to make it. Once again as in the past he used large amounts of alcohol to deal with the lack of heroin in his system. Even with the alcohol intake the recording that were made in Denmark got him invited to France to play with Roy Eliding in the Salon Du Jazz. Charles did not fulfill his obligations there due to his partying. Also as a result of all the drinking Charles had one he returned with a stomach ulcer. Charles daughter Pre was born with a heart defect which required expensive medical treatment.This is something that his addiction to heroin and alcohol had biggest blows to Charles and Doris life together. Hearing the news while out of town on a gig Charlies reported first response was to get drunk, and then he gave away his heroin. This was also the year that Charles last commercial recording was made. Charles last important gig was to be part of an all-star band appearing at Birdman. The first night went well while the second night was ridden with problems. Charles and Pianist Bud Powel Clashed and couldnt work together that night. Charles Began to drink, became drunk and was asked to leave by management.Little did the band know or realize that the next day was the one year anniversary of Preps death and it was weighing heavily on Charles mind. On March 9, 1955 Charles met his death. There are three versions of what happened at the end but the most likely one involves throwing up blood from his ulcers Just before passing away. The actual facts about how he died isnt really relative t this paper. This paper was to hopefully show that because of Charles Parker Jar. s drug addiction his life was cut short and his musical abilities were not enhanced or caused by the drugs that he used.Charles himself said Any musician who says he is playing better either on tea, the needle or when he is Juiced is a plain, straight liar. (CTD. Bird: The Legend of Charlie Parker 57) . Events in this paper show that his sound was best when he was somewhat clean, somewhat because once he started on drugs I dont believe he was ever without something in his system. If it had not been for his short 35 year old life and his drug abuse there is no telling how far Charles loud have taken his talent and in what directions Jazz might have gone.