As You Like It Essay

‘As You Like It’ Essay Belonging is the inclusion of both acceptance and alienation. Belonging is security, connection and camaraderie where as not belonging is estrangement, ostracism and seclusion. To belong to people, communities or places can create positive as well as negative outcomes. People’s perceptions of belonging are constantly changing due to personal, historical, cultural and social contexts. In Shakespeare’s ‘As You Like It’ incorporates both aspects of belonging; acceptance and alienation. Different types are presented throughout the play by showing connections to place, to people and to ideas. Each connection that is presented details the characters emotions, actions and morals and values. Connections to certain places is expressed throughout the play but is not restricted to a single environment. Various characters including Orlando, Rosalind and Duke Senior all achieved a sense of belonging through their banishment/withdrawal from the court environment to the Forest of Arden. The Court, once a place where these characters rightfully belonged and had created affinities with, now had became a hostile and foreign environment forming negative outcomes. Not long after, they created connections to the Forest of Arden by the forest providing them with a place of protection and a place to heal their wounded emotions. The forest and the Court are juxtaposed because both environments are necessary to create balance and unity between the characters so they can live happy and fulfilled lives. Rosalind and Orlando had to be banished from the Court, to then thrive and find themselves in the Forest of Arden enabling them to then return to the Court to live their lives where they rightfully belong displaying the importance of these environments. Connections to people are what forms their morals and values and defines their actions. Celia is a perfect example of a connection to a person. She demonstrated the power of love and one’s connection to a person through her loyalty and devotion to Rosalind by showing that she would abandon everything; the Court life and her father, to follow Rosalind into the forest. She had displayed that there is no home at the court, no sense of belonging, without her Rosalind. This connection that Celia had with Rosalind created positive effects to herself and conveyed how belonging to a person was necessary for a positive outcome. Connections to certain ideas define who people are but they also can be poignant and thought provoking toward the audience. Through the play the quote ‘All the world’s a stage’ pessimistically tells us that we all are one in this life. The play affirms that everyone belongs to the same human race and they all have the same ending. This idea is expressed in the dance at the end. It represents a social ritual where everyone belongs and they celebrate love, marriage and common humanity. Ideas can also shape ones perceptions of the world and how they act toward them. Belonging can not just create positive or negative outcomes but it can either enrich or diminish a person’s life; their actions, decisions, morals and values and emotions. In Shakespeare’s ‘As You Like It’ everyone experiences positive outcomes because it is one of his comedies. Belonging throughout the play established its importance to the characters and also detailed the connections they had with each other, their environment and themselves. It also showed how belonging is continually modifying to one’s circumstances but also by their personal, historical, cultural and social contexts.

Dynamic Character Essay

In the novel, Fahrenheit 451, the main character, Guy Montag, qualifies as a dynamic character. A dynamic character is, by definition, a character that undergoes important changes throughout the course of the novel. Because he goes through a metamorphosis as he struggles through internal conflict during the novel, Guy Montag is a dynamic character. In the beginning, Montag is a very normal man relative to his society. He is a city fireman and burns books and houses without regret. Montag loves everything about his job; the power, the destruction of houses and books, and even the smell of the kerosene that he churns out daily. He even feels pride and satisfaction in the jobs he carries out. His change, though, soon begins when he meets with a peculiar girl named Clarisse. Clarisse makes Montag actually think, an uncommon thing in this peculiar society. Her pure innocence brings out a different side of him; one that doesn’t involve thoughtless burnings. He then, as a result of her insight, begins to question himself and even the society he lives in. Another influence on Montag is the suicidal woman whose house he was about to burn. He ponders what in books can be important enough to die for. Her gruesome suicide pushes Montag over the edge and he forces himself to finally open a book. Montag continues his metamorphosis from a heartless book burner to a philosophical learner. Guy continues gaining information and forming his opinion about his odd society. Montag soon realizes that there is no return from his change when he is forced to burn his own house and murder Beatty. In a way he is burning his own past and all that goes with it. His subsequent fleeing of the seen also symbolizes the final step in his change. It is Montag literally leaving his past of senselessness and destruction. Guy Montag becomes a sensible, book loving educator. His metamorphosis is complete with memorizing books in a contribution to end the norm of his  society. He makes a tremendous change both mentally and physically. Because of his change, though it caused him great hardships, Guy Montag is a dynamic character.

Asian American Literature Essay Research Paper It

Asiatic American Literature Essay, Research PaperIt is true that all people are created different, and therefore no two civilizations will of all time be the same. Throughout Asiatic American literature at that place seems to be a battle between the Asiatic civilization and American civilization. More specifically, there is a battle between Asiatic adult females and their Asiatic American girls, and what it means to be feminine, and how a adult female should move. The chief battle is between how the American adult female should move and how the Asiatic adult female should move. However, the behaviour of the Asian adult female seems to be dominant through out the narrative because although the girls and the female parents may non acquire along all of the clip, the female parents to have a batch of regard from their girls. Therefore, the female parents sentiment on how they should move, which is acting like the Asian adult female, is most apparent. This is the instance in The Joy Luck Club, written by Amy Tan and besides in the short narrative # 8220 ; Waiting for Mr. Kim, # 8221 ; written by Carol Roh-Spaulding. These two narratives have really different significances, nevertheless they are similar in the facet that they are all Asiatic adult females with Asiatic American girls seeking to acquire their girls to maintain and utilize their Asiatic heritage. There are certain behaviours that Asiatic adult females are expected to hold, and the female parents feel that their girls should utilize these behaviours. In The Joy Luck Club, the novel traces the destiny of the four mothers-Suyuan Woo, An-mei Hsu, Lindo Jong, and Ying-ying St. Clair-and their four daughters-June Woo, Rose Hsu Jordan, Waverly Jong, and Lena St. Clair. Through the experiences that these characters go through, they become adult females. The female parents all fled China in the 1940 # 8217 ; s and they all retain much of their heritage. Their heritage focuses on what is means to be a female, but more significantly what it means to be an Asiatic female. In the short narrative # 8220 ; Waiting for Mr. Kim, # 8221 ; the chief female character Gracie understands what it means to be an Asiatic female, but she does oppugn the significance because of her sisters. Her sisters ran off from place before their matrimony could be arranged and eloped. This is wholly against Asiatic civilization, and it causes Gracie to oppugn her heritage and her Asiatic muliebrity. In both of these narratives there are certain features of females that are the same, they are interior strength, obeisance, award and regard, the good of the whole is better than the good of the person, and happening things out for yourself. In the chapter # 8220 ; Scar # 8221 ; the feature of award and regard is foremost noticed. In this chapter An-mei finds out how her female parent fundamentally deserted her, her female parent did go forth for a good ground, which was to keep the award of her household, but either manner her female parent left her. Her grandma had to raise her, and she learned much about the Asiatic adult female from her. An-mei was demoing some disrespect towards on of her aunts, and her aunt told her that she was being disrespectful. Her grandma so interjected and said, # 8220 ; When you lose your face, An-mei? it is like dropping your necklace down a well. The lone manner you can acquire it back is to fall in after it. # 8221 ; She was speaking about A-mei # 8217 ; s female parent, and how she left because she had disrespected the household and she was dishonourable to the household name. The lone manner for her female parent to recover regard and award was to go forth and make it on her ain, which is a feature of an Asiatic adult female. Another feminine feature that comes from that scene is being able to make things on your ain. However, this is an American influence. This characteristic comes from the chapter # 8220 ; Rules of the Game. # 8221 ; This is a curious chapter in the book because it is a chapter where the adult female is non seen as inferior to the adult male. Waverly # 8217 ; s brother, Vincent, received a cheat set for Christmas. However, Waverly is the 1 who took full usage of the cheat set. She was a natural, she would crush her brothers in cheat, which would usually be looked down upon in Asiatic civilization, but she was encouraged. She was even given lessons in cheat, and she was a national title-holder. Unlike An-mei # 8217 ; s female parent, Waverly was conveying award to the household name. When Waverly is encouraged to stand out in cheat she learns something from her female parent. Her female parent said in her broken English, # 8220 ; This American regulations? Every clip people come out from a foreign state, must cognize regulations. You non cognize, justice say, Too bad, travel back. They non stating you why so you can utilize their manner to travel frontward. They say, Don # 8217 ; Ts know why, you find out your self. # 8221 ; This is an American usage, more than an Asiatic 1. She is explicating that in order to win as an Asiatic female in the United States, so there are certain things that you will hold to happen out on your ain. Besides in this chapter was the theme/characteristic of inner streng th. Waverly says she six when her mother taught her the â€Å"art of invisible strength.† Waverly was walking by the candy store when she was a young child, and she was begging her mother to take her inside. Her mother refused to take her inside, which angered Waverly. Then her mother went on to explain, â€Å"Wise guy, he not go against wind. In Chinese we say, Come from South blow with wind-poom!-North will follow. Strongest wind cannot be seen.† This means that the strongest way to win an argument is to keep to yourself, which Waverly used in her chess matches. Waverly goes on to say, â€Å"A little knowledge withheld is a great advantage one should store for future use.† Another example of invisible strength, inner strength, is the â€Å"The Moon Lady.† Ying-ying’s mother was telling her how a woman should act when she said, â€Å"A boy can run and chase dragonflies?But a girl should stand still.† The girl would have a better chance cat ching the dragonfly than the boy, she would catch the dragonfly with inner strength, rather than muscle like the boy. The chapter, â€Å"The Moon Lady,† has another characteristic of what it is to be female, which is the good of the whole is more important than the good of the individual. They were all on their way to see the Moon Lady, and if you see the Moon Lady, you receive one wish from her. Ying-ying asked what a â€Å"secret wish† was, and the answer was that is was on that you cannot ask. Ying-ying was young as this point, so she asked why. Amah’s response to Ying-ying was, â€Å"This is because?because if you ask it?it is no longer a wish but a selfish desire?Haven’t I taught you-that it is wrong to think of our own needs? A girl can never ask, only listen.† Here she is telling that by making a wish for herself she is being selfish and forgetting that she is not the important one, but the good of the whole is the important one. Amah is als o hinting at obedience when she tells her daughter that she is not to ask questions, but just listen to the men and go along with it. Arranged marriages are a very tough thing to go through. Marrying someone because one has to has to be hard because one is not marrying out of love. This is exactly the case in â€Å"Waiting for Mr. Kim.† Gracie two twin sisters have already run away from to and eloped with two men. Their marriages were not arranged because they left before their father could arrange them. Now, with her sisters gone, Gracie is the only remaining daughter, and she is somewhat frowned upon because she was the â€Å"third daughter.† She did not really like the two men that her father was thinking of arranging the marriage with, but it did not matter. It did not matter because as her mother told her, â€Å"Girls don’t choose.† The girls just sit there and look pretty while their fathers choose for them, they have to comply with their fatherâ₠¬â„¢s decision. They are obedient, and at the same time respectful of the decision that is made. Another characteristic that appears in this story is that women made to think that they are second class compared to men. When her Mr. Kang, Gracie’s father, would walk, he would sometimes reach back to hold Mrs. Kang’s hand, but she would pull away. Not only would she pull away, but she would â€Å"stay behind as she cleaned her purse or took forever with her coat, just to have it the way she had learned it, her husband a few places ahead, women behind.† Her mother not only believes that this is how women should act and it is a part of their femininity, but she is passing this way of thinking onto her daughter. Her mother is relaying the message to her daughter that no matter what you need to show your husband respect and let him know that he is in charge. Both of these stories have displayed that there are certain characteristics of females and they are inner stren gth, the good of the whole is better than the good of the individual, find things out for oneself, honor and respect, and obedience. All of these characteristics have displayed not only what it means to be feminine, but also what it means to be female. It is not so much an Asian female, but it is because that is how their mothers were raised and that is how their mothers will raise them. There are really no American females for the daughters, or mothers, to see and mimic. The only way of life that the mothers know is the Asian way of life, therefore that is the only way that can be passed down onto their daughters. Sometimes that is hard for the daughters to understand because the daughters have grown up in American culture, and they know what it is like to be an American woman. No matter how one views this situation, these stories focus on what it means to an Asian female, but more generally what the mothers know best on how to teach their daughters on how to be female.

Boost of Economic Prosperity Essay Example | Topics and Well Written Essays - 250 words

Boost of Economic Prosperity - Essay Example Every field demands effective decision making that enables the producers to conduct their business with the least amount of resources. It was Adam Smith’s theory of the â€Å"invisible hand† that facilitated the comprehension of the mechanics of a society in the simplest manner. The knowledge of economics not only benefits one professionally, it also helps to know the difference between right choices and wrong ones on a personal level. It facilitates the comprehension of the global ongoing activities in the economic sector and how everything affects the life of a common man. Specifically, the global depression has changed the world and has made the common man suffer due to few wrong choices by decision makers in the economic arena. I aspire to attain greater knowledge in the field of economics and acquire a Masters degree to comprehend economic activities to a greater extent and devise solutions to reduce the effect of wrong decisions. I shall be very grateful if you grant me the admission and help me pursue my dream of acquiring further education.

Safety management Essay Example | Topics and Well Written Essays - 250 words

Safety management - Essay Example Moreover, drums that have been made with non-combustible and absorbent materials such as vermiculite are recommended to avoid any cases of leakage. The drum should therefore undergo thorough sealing. It should then be labeled DANGER CHEMICAL PCB WASTE and should be written in English or the understood language. PCB containers are not supposed to be stacked and should be well secured from any form of insecurity. Firefighting materials should also be ready in case of any fire. Upon disposal, the PCB materials should undergo incineration of temperatures above 1,100Â °C. In addition, there should be a mean radiance of 2 seconds with minimum access to oxygen content of 3%. After decontamination, the excavator should be removed from the site by a fork lift that should be positioned away from the contaminated building. Using the fork lift, the excavator should be lifted and transported to the necessary site where further decontamination process should be carried on to ensure zero tolerance of contamination. Published under the Waste Disposal Ordinance (Cap.354) Section 35. (2014). CODE OF PRACTICE ON THE HANDLING, TRANSPORTATION AND DISPOSAL OF POLYCHLORINATED BIPHENYL WASTE. Environmental Protection Department Hong Kong,

Marketing Makes Strong Fashion Brands Essay Example | Topics and Well Written Essays - 500 words

Marketing Makes Strong Fashion Brands - Essay Example The essay "Marketing Makes Strong Fashion Brands" discovers the role of marketing in the future of the fashion brands. The stage is called Outward Marketing. Without properly undergoing through these two stages, difficulties may arise according to Carter McNamara, MBA, â€Å"As a result, they often end up trying to push products onto people who really don't want the products at all. Effective inbound marketing often results in much more effective and less difficult outbound marketing and sales.† The key therefore is to conduct good inbound marketing as a foundation to outbound marketing. Bearing this advice in mind, businesses will have a fair chance of succeeding in the highly competitive market. The strongest element in Inbound Marketing that leading companies spend a lot on is Outbound marketing is the outward manifestation that directly interacts with people. The most powerful element of outbound marketing is advertising. The Britannica Concise Encyclopedia defines adverti sing techniques and practices as making â€Å"the public to notice products for the purpose of persuading the public to respond in a certain way.† People will know of the product, identify with it and buy it. Ioana Chioveanu (2006), names this as â€Å"persuasive advertising which induces brand loyalty in consumers who would otherwise buy the cheapest alternative on the market.† This is the very essence of advertising and companies spend a lot on advertising. In fact a survey of the Leading National Advertisers.

Air Service Agreements (Part 1) Essay Example | Topics and Well Written Essays - 250 words

Air Service Agreements (Part 1) - Essay Example The Chicago Convention of 1944 also created an independent organization, the heir to the International Commission for Air Navigation. The new organization exists and is a key player in international law: the International Civil Aviation Organization (ICAO), based in Montrà ©al (ICAO, 2007). Both the U.S and U.K signed a convention relating to the regulation of aerial navigation which influenced other states like Italy, japan, Brazil, France, Greece and Poland to sign. They modified their domestic laws to reflect the newfound jurisdiction. England was the first off the mark with their air aviation act 1920. In 1958, the U.S adopted its own version of sovereignty called the federal aviation act (Geloso, 2008). Bermuda I led to the agreement between United States and Great Britain on the first two freedoms that is the right to fly over territory of another country and the right to land for essential repairs, refuelling or to escape adverse weather conditions in another country. The United States also agreed that the international air transport association an international body that would set fares subject to the two government’s approval. Bilateral agreement became the model for a series of future bilateral agreements between United States and other countries (Marin,

Truth and Context Essay Example | Topics and Well Written Essays - 1250 words

Truth and Context - Essay Example When context is all there is no validity for truth. The credibility of the concept of truth is in the acceptance of something that the popular belief teaches as existing. If everything in the world is subject to context, it would mean that there is no thing that may be termed "truth". The concept is philosophically weak, in spite of the long efforts to define and comprehend what "truth" really means. As Bacon in his 'Of Truth' tells, 'What is truth Said jesting Pilate, and would not stay for an answer." (Essays of Francis Bacon). The understanding of truth in relation to context is, therefore, essential especially in the modern world, where "lack of trust mirrors the absence of truth in public life." (Lee 1997). It is of great significance to comprehend what context and truth mean and their relation to one another. There are many definitions for the term "context" and according to the Dictionary of Terms, context "includes the political, social, historical, psychological, institutional, and aesthetic factors that shape the way we understand the performance event." (Dictionary of Terms. 2006). Another definition reads "The circumstances relevant to something under consideration." (CERN Engineering Data Management Service. 2001). There are many such varying definitions all of which means truth in a given circumstances. Context does not give truth in the wider sense of the word. Is it true that context determines and narrows down the scope of truth The various construal of the term truth, an opened ended word, gives the notion that if "context is all" truth is almost impossible. Chris Richards finds that the definition of truth is various and he is interested in the definitions "conformity with fact or reality" and "an obvious or accepted fact". As he points out, the former definition, as in the Correspondence theory, "ties truth with relationship between thoughts and words in one part, and things and objects in the other." (Richards 2007). He also makes clear, as the Constructive Theory teaches that truth is created by social progress. The latter definition seems to be more correct as it gives the notion that truth is understood in the context. We understand the concept truth when there is a mass recognition of the fact. Sociological interpretation of the concept also confirms the Consensus Theory that truth is a matter of conformity. Truth when deemed false is not regarded as true. In the modern life also truth, many a time, goes unrecognised when people around us do not understand the fact in context. Truth, most of the times, is made by the public acceptance, leaving the concept to the discretion of people. Truth is context-bound and relative in nature. Let us not forget that "a bare assertion is not necessarily the naked truth." (Prentice 2007). Therefore, a contextualized view of truth is not completely acceptable. Having said that, one cannot ignore the possibility of this narrow understanding of truth, especially in a modern materialistic world. People understand truth in many possible ways. The popular understanding of truth is relative and only relative truth exists in this modern world. Here, we find not truth but truths. The

RETAIL STRATEGY Essay Example | Topics and Well Written Essays - 2500 words

RETAIL STRATEGY - Essay Example In the face of economic growth and radical economic volatility at home, the most attractive retailing options may lie in Asia. Although few domestic retailers are positioned to capitalize on international opportunities, virtually all retailers will be affected by the emergence of the one-world marketplace. As the international borders and barriers come down and the free flow of products goes up, even the smallest mom-and-pop store will be swept up in change. The main trends in the retail industry include fragmentation, specialization and differentiation. Increasing cultural diversity and ethnic insulation lead to market fragmentation. Certainly a number of established retailers are poised to capitalize on the one common denominator that cuts across racial and ethnic diversity--the persistent emphasis on bang-for-the- buck, or value. However, currently most retailers are ill equipped to capitalize on the new opportunities promised by market fragmentation because they do not have access to the expertise required to understand the behavioral manifestations of cultural heritage and ethnic identification (Levy and Weitz 2004). The leading retailers of the 1990s will be those that shore up the knowledge gap by recruiting, hiring, training, and promoting people or by employing outside consultants from cultural and ethnic backgrounds corresponding to those market fragments that promise the greatest profit potential (The Committee for the Histor y of Retailing and Distribution 2009). Although the UK market has grown in absolute terms, the 1990s promise smaller targets of opportunity, both in sheer size and in duration. The factors fueling population growth are conspiring to produce what some have termed "the death of the mass market--and mass marketing" (Levy and Weitz 2004). Although birthrates continue their downward trend,

Academic Qualification Ensures Success in Life Essay Example for Free

Academic Qualification Ensures Success in Life Essay The definition of success differs from person to person and field to field. One could take economic success as a touchstone to label a person successful in life, ignoring his of her other failures, like divorce, health, inefficiency, etc. Others may look at a capacity for overcoming challenges, irrespective of what someone earns and the nature of their private life. So who is a successful person and who is a failure? Do school and college grades and examination results provide a way of predicting or ensuring future success? If that is true, then we should encourage as many young people as possible to go to university and work hard to gain formal qualifications. But is it true? Aren’t some college drop-outs like Bill Gates and Richard Branson hugely successful icons of success? And should we automatically consider the millions of young people who have not had the opportunity to gain academic certificates to be failures in life? Success never depends upon grades. If success and opportunities were measured by grades then the corporate world and potential marriage partners would not ask for biodata in resumes, where other qualifications are also mentioned. Nor would they interview the prospects in order to find out what they are like as people, rather they would give a blind appointment to the people with the best paper qualifications. So qualifications alone are never enough, success depends upon physical characteristics, personality, and a willingness to work hard. Success is not getting a grade or a degree, if that was it then why arent all the graduates from Harvard, Oxford or Cambridge uniformly successful? The rule of success is hard work and destiny of course. If a student of engineering gets good grades but he is not practically effective in relationship-buildings and solving crises or proper planning, even though he may be successful in getting a job but it will not lead him far. On the way he is sure to fade out. If you look into a directory of successful people who are doctors, engineers and IT professionals, then you will notice that many of them dream to be employed by people like Bill Gates or Richard Branson, who are prosperous despite not having college degrees. In other words, prosperity does not depend upon academic qualifications but upon opportunities provided by entrepreneurs who may not be necessarily be highly educated. Successful entrepreneurs even benefit from not having academic qualifications, because going to college and taking examinations forces people to learn and think like millions of other graduates. This actually makes it less likely that they will come up with the truly mould-breaking insights and â€Å"disruptive† ideas on which successful innovations and new business models are built. Unfortunately the materialistic world has changed the concept of success. It has become a rat-race where every student chases grades and therefore the entire perception of success and prosperity has changed. Rather than studying to reach our full potential, we do it because we think it is necessary for a successful career. So we spend ten years in school and a few more years of our precious life in college to get educated, then more time is passed in hunting for jobs. Even after that we may find ourselves in the wrong profession and lacking job satisfaction. And then recession comes along, when we are told that our wealth has been blown away by the foolishness of expensive fat-salaried CEOs. Now comes a time when we go to work with a constant fear of losing the job we don’t enjoy. Is this the correct understanding of prosperity? So now the definition of success is changed. If you are able to save your job then you are successful! Can academic qualification stop us from becoming a civilization of drunkards, rapists and war-mongers, marked by broken families, domestic violence and crime? If you look at countries where the largest number of people have higher academic qualifications, they are the ones most affected by social breakdown. And would you call the conduct of the US wars on Iraq and Afghanistan a successful example of the superiority of the US economy and society? In fact true success is shown in having the moral courage to speak out against atrocities and injustice, showing generosity towards the poor, and respecting our parents. These are characteristics which are found in people from all social and educational backgrounds, but often absent in many educated Americans and Europeans, in spite of the universities they have been to and the grades they have achieved. Often academic qualifications have no real relevance to the jobs graduates are employed to do. A few decades ago employers in areas such as banking, engineering, management and government service recruited people straight from school at the age of 15 or 16, training them on the job and promoting them to higher levels of responsibility according to their ability. Today none of these jobs has changed very much, but all now require applicants have a university degree. Why has this changed? One reason is that the upper and middle classes are trying to protect their own jobs – demanding new recruits have expensive academic qualifications excludes many talented young people from poorer backgrounds.

On the Implant Communication and MAC Protocols for a WBAN

On the Implant Communication and MAC Protocols for a WBAN Abstract Recent advances in micro-electro-mechanical systems (MEMS), wireless communication, low-power intelligent sensors, and semiconductor technologies have allowed the realization of a wireless body area network (WBAN). A WBAN provides unobtrusive health monitoring for a long period of time with real-time updates to the physician. It is widely used for ubiquitous healthcare, entertainment, and military applications. The implantable and wearable medical devices have several critical requirements such as power consumption, data rate, size, and low-power medium access control (MAC) protocols. This article consists of two parts: body implant communication, which is concerned with the communication to and from a human body using RF technology, and WBAN MAC protocols, which presents several low-power MAC protocols for a WBAN with useful guidelines. In body implant communication, the in-body radio frequency (RF) performance is affected considerably by the implants depth inside the human body as well as by the muscle and fat. We observe best performance at a depth of 3cm and not close to the human skin. Furthermore, the study of low-power MAC protocols highlights the most important aspects of developing a single, a low-power, and a reliable MAC protocol for a WBAN. Keywords: In-body, on-body, RF communication, Implant, WBAN 1. Introduction Cardiovascular diseases are the foremost cause of deaths in the United States and Europe since 1900. More than ten million people are affected in Europe, one million in the US, and twenty two million people in the world [1]. The number is projected to be triple by 2020, resulting in an expenditure of around 20% of the gross domestic product (GDP). The ratio is 17% in South Korea and 39% in the UK [2]. The healthcare expenditure in the US is expected to be increased from $2.9 trillion in 2009 to $4 trillion US dollars in 2015 [3]. The impending health crisis attracts researchers, industrialists, and economists towards optimal and quick health solutions. The non-intrusive and ambulatory health monitoring of patients vital signs with real time updates of medical records via internet provide economical solutions to the health care systems. A wireless body area network (WBAN) is becoming increasingly important for healthcare systems, sporting activities, and members of emergency as well as military services. WBAN is an integration of in-body (implants) and on-body (wearable) sensors that allow inexpensive, unobtrusive, and long-term health monitoring of a patient during normal daily activities for prolonged periods of time. In-body radio frequency (RF) communications have the potential to dramatically change the future of healthcare. For example, they allow an implanted pacemaker to regularly transmit performance data and the patients health status to the physician. However, the human body poses many wireless transmission challenges. This is partially conductive and consists of materials having different dielectric constants and characteristics impedance. The interface of muscles and fats may reflect the RF wave rather than transmitting it. The key elements of an RF-linked implant are the in-body antenna and the communi cation link performance. Also, in the case of many implants and wearable sensors, a low-power MAC protocol is required to accommodate the heterogeneous traffic in a power-efficient manner. This article is divided into two parts: body implant communication and WBAN MAC protocols. In the body implant communication part, we look at the RF communication link performance at various depths inside a human (artificial) body. In the MAC part, we review the existing low-power MAC protocols and discuss their pros and cons in the context of a WBAN. We further provide alternative MAC solutions for in-body and on-body communication systems. The rest of the article is divided into three sections. In section 2, we present a discussion on body implant communication including in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. Section 3 discusses several low-power MAC protocols and realizes a need for a new, a low-power, and a reliable MAC protocol for a WBAN. The final section concludes our work. 2. Body Implant Communication There are several ways to communicate with an implant that includes the use of electromagnetic induction and RF technology. Both are wireless and their use depends on the application requirements. Further, the key elements of an RF-linked implant are the in-body antenna and the communication link performance. The following part discusses in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. 2.1. In-body Electromagnetic Induction Several applications still use electromagnetic coupling to provide a communication link to an implant device. In this scheme, an external coil is held very close to the body that couples to a coil implanted just below the skin surface. The implant is powered by the coupled magnetic field and requires no battery for communication. Data is transferred from the implant by altering the impedance of the implanted loop that is detected by the external coil and electronics. This type of communication is commonly used to identify animals that have been injected with an electronic tag. Electromagnetic induction is used when continuous, long-term communication is required. The base band for electromagnetic communication is typically 13.56 MHz or 28 MHz, with other frequencies also available. The choice of a particular band is subject to regulation for maximum specific absorption rate (SAR). The inductive coupling achieves best power transfer efficiency when uses large transmit and receive coil s. It, however, becomes less efficient when the space is an issue of the device is implanted deep inside the human body. Furthermore, inductive coupling technique does not support a very high data rate and cannot initiate a communication session from inside of the body. 2.2. In-body RF Communication Compared with the electromagnetic induction, RF communication dramatically increases bandwidth and supports a two-way data communication. The band designated for the in-body RF communication is medical implant communication service (MICS) band and is around 403 to 405 MHz. This band has a power limit of 25  µW in the air and is usually split into ten channels of 300 kHz bandwidth each. The human body is a medium that poses numerous wireless transmission challenges. It consists of various components that are not predictable and will change as the patient ages, gains or losses weight, or even changes posture. Values of dielectric constant (ÃŽ µr), conductivity (ÏÆ') and characteristic impedance (Zo) for some body tissue are given in table 1 [4]. This demonstrates that these two tissue types are very different. Also, the dielectric constant affects the wavelength of a signal. At 403 MHz, the wavelength in the air is 744mm, but in muscle with ÃŽ µr = 50 the wavelength reduces to 105mm, which helps in designing implanted antennas. 2.3. In-body Antenna Design A modern in-body antenna should be tuneable by using an intelligent transceiver and software routine. This enables the antenna coupling circuit to be optimised. Due to the frequency, and available volume, a non-resonant antenna is commonly used. It has a lower gain than a resonant antenna. This makes design of the antenna coupling circuit very important. Antenna options are dictated by the location of the implant. A patch antenna can be used when the implant is flat. Patch antennas are comprised of a flat insulating substrate coated on both sides with a conductor. The substrate is a body compatible material with a platinum or a platinum/iridium conductor. The upper surface is the active face and is connected to the transceiver. The connection to the transceiver needs to pass through the case where the hermetic seal is maintained, requiring a feed-through. The feed-through must have no filter capacitors present; these are common on other devices. An implanted patch antenna is electrically larger than its physical size because it is immersed in a high (ÃŽ µr) medium. It can be much larger electrically if the substrate is of higher (ÃŽ µr), such as titania or zirconia. A loop antenna can also be attached to the implant. This antenna operates mostly by the magnetic field, whereas the patch operates mostly by the electric field. The loop antenna delivers performance comparable to that of a dipole, but with a considerably smaller size. In addition, the magnetic permeability of muscle or fat is very similar to that of an air, unlike the dielectric constant that varies considerably. This property enables an antenna to be built and used with much less need for retuning. A loop antenna can be mounted on the case in a biocompatible structure. 2.4. In-body Link Performance The demonstration system consists of a base-station, an implant, antennas, and a controlling laptop. The base-station contains a printed circuit board (PCB) with a wakeup RF circuit, a Zarlink ZL70101 IC, and a micro-controller. It sends a wakeup signal on industrial, scientific, and medical (ISM) 2.4 GHz band to power up the implant to communicate. It also supports communication within the MICS band. The implant contains a Zarlink ZL70101 IC, a micro-controller, and a battery. The power limits of the wakeup signal for ISM and MICS bands transmitters are 100mW and 25  µW respectively. Experiments that measure the performance of an implant inside a living body are difficult to arrange. The alternative is to use 3D simulation software or a body phantom defined in [5]. The use of 3D simulation software is time consuming and hence practically not valuable. Therefore, measurements are generally performed using the body phantom and immersing a battery-powered implant into it [6]. Since no additional cables are attached to the test implant, the interference errors in the measurements are minimal. The body phantom is filled with a liquid that mimics the electrical properties of the human body tissues. The test environment is an anechoic chamber that includes a screened room. The interior walls of the room have sound-absorbent cones to minimize any reflections from walls or the floor that could distort the results. In real life, however, the results will be affected by the reflections from walls, desks, and other equipment and hardware. The body phantom is mounted on a woo den stand (non-conductive). The distance from the body phantom to the base-station is 3m. The MICS base-station dipole antenna is mounted on a stand. 1(a) shows the anechoic chamber with a body phantom (on the wooden stand), a log periodic test antenna (foreground), and a base-station dipole (right). The log periodic antenna is used to calculate the power radiated from the body phantom. A depth is defined as the horizontal distance between the outer skin of the phantom and the test implant. Vertical polarization of the implant is the case when the long side of the box and the patch antenna is vertical. The link performance is measured once the communication link is established. The measurements include the effective radiated power (ERP) from the implant, the received signal at the implant from the base-station, and the link quality. Measurements are made over a set distance with all the combinations of implant and test antenna polarisations, i.e., vertical-vertical (V-V), horizontal-vertical (H-V), vertical-horizontal (V-H), and horizontal-horizontal (H-H) polarisations. Typical results are shown in 1(b) where the ERP is calculated from the received signal power and the antenna characteristics. The measurement of the signal levels is done with the log periodic antenna and the spectrum analyzer. It can be seen in the that there is a significant difference in signal levels with polarisation combinations and depths. For a V-V polarisation, the ERP increases from a 1cm depth to a maximum between 2 and 7 cm, and then it decreases. The gradual increase is due to the simulated body acti ng as a parasitic antenna. The also shows how the signal level is affected by the depth with different polarisation. Such a test needs to be done with the antenna that is to be used in the final product. To measure the received signal at the implant, the Zarlink ZL70101 has an inbuilt receive signal strength indication (RSSI) function that gives a measure of the signal level detected. RSSI is a relative measurement with no calibration. The implant receives and measures a continuous wave signal transmitted by the base-station. In this case, the implant and the base-station antennas are vertically polarised. 1(c) shows an increase in the signal level at a depth between 3 and 4cm for a 15dec power. The power settings refer to the base-station and are cond to set the ERP to 25  µW. Signal levels are not valuable unless they are related to data transmission. One way to maintain the link quality is to measure the number of times the error correction is invoked during the transmission of 100 blocks of data. Two types of error correction codes, i.e., error correction code (ECC) and cyclic redundancy code (CRC) are invoked to maintain data integrity and reliability. The fewer ECC and CRC invocations result in better link quality. In 1(d), the error correction is lowest at a depth between 3 and 5 cm. A sample of ECC data collected at a 3cm implant depth is given in Table 2. The Count indicates the number of data blocks, the Time (ms) indicates the block transmission time, and the ECC indicates the number of times it is invoked. During the transmission of 100 blocks of data at a 3cm depth, the ECC is invoked 368 times, which is further equivalent to an average 3.68 times (as given in 1(d)). 2.5. Discussion The ERP, RSSI, as well as the ECC and CRC plots show that the implant demonstrates the best performance at a depth between 3 and 5 cm. The depth and position of an implant is not chosen for engineering performance but for the best clinical reasons. The implant designer must be aware of the possible losses through the human body. The attenuation and the parasitic antenna effects vary from patient to patient, with the position of the implant and with the time as the patient gains, or looses weight. Therefore, these factors need to be built into the link budget. 3. WBAN MAC Protocols Some of the common objectives in a WBAN are to achieve maximum throughput, minimum delay, and to maximize the network lifetime by controlling the main sources of energy waste, i.e., collision, idle listening, overhearing, and control packet overhead. A collision occurs when more than one packet transmits data at the same time. The collided packets have to be retransmitted, which consumes extra energy. The second source of energy waste is idle listening, meaning that a node listens to an idle channel to receive data. The third source is overhearing, i.e., to receive packets that are destined to other nodes. The last source is control packet overhead, meaning that control information area added to the payload. Minimal number of control packets should be used for data transmission. Generally MAC protocols are grouped into contention-based and schedule-based MAC protocols. In contention-based MAC protocols such as carrier sense multiple access/collision avoidance (CSMA/CA) protocols, nodes contend for the channel to transmit data. If the channel is busy, the node defers its transmission until it becomes idle. These protocols are scalable with no strict time synchronization constraint. However, they incur significant protocol overhead. In schedule-based protocols such as time division multiple access (TDMA) protocols, the channel is divided into time slots of fixed or variable duration. These slots are assigned to nodes and each node transmits during its slot period. These protocols are energy conserving protocols. Since the duty cycle of radio is reduced, there is no contention, idle listening and overhearing problems. But these protocols require frequent synchronization. Table 3 compares CSMA/CA and TDMA protocols. 3.1. WBAN MAC Requirements The most important attribute of a good MAC protocol for a WBAN is energy efficiency. In some applications, the device should support a battery life of months or years without interventions, while others may require a battery life of tens of hours due to the nature of the applications. For example, cardiac defibrillators and pacemakers should have a lifetime of more than 5 years, while swallowable camera pills have a lifetime of 12 hours. Power-efficient and flexible duty cycling techniques are required to minimize the idle listening, overhearing, packet collisions and control packet overhead. Furthermore, low duty cycle nodes should not receive frequent synchronization and control information (beacon frames) if they have no data to send or receive. The WBAN MAC should also support simultaneous operation on in-body (MICS) and on-body channels (ISM or UWB) at the same time. In other words, it should support multiple physical layer (Multi-PHYs) communication or MAC transparency. Other important factors are scalability and adaptability to changes in the network, delay, throughput, and bandwidth utilization. Changes in the network topology, the position of the human body, and the node density should be handled rapidly and successfully. The MAC protocol for a WBAN should consider the electrical properties of the human body and the diverse traffic nature of in-body and on-body nodes. For example, the data rate of in-body nodes varies, ranging from few kbps in pacemaker to several Mbps in capsular endoscope. In the following sections, we discuss proposed MAC protocols for a WBAN with useful guidelines. We also present a case study of IEEE 802.15.4, PB-TDMA, and S-MAC protocols for a WBAN using NS2 simulator. 3.2. Proposed MAC Protocols for a WBAN In this section, we study proposed MAC protocols for a WBAN followed by useful suggestions/comments. Many of the proposed MAC protocols are the extension of existing MAC protocols originally proposed for wireless sensor networks (WSNs). 3.2.1. IEEE 802.15.4 IEEE 802.15.4 has remained the main focus of many researchers during the past few years. Some of the main reasons of selecting IEEE 802.15.4 for a WBAN were low-power communication and support of low data rate WBAN applications. Nicolas et.al investigated the performance of a non-beacon IEEE 802.15.4 in [7], where low upload/download rates (mostly per hour) are considered. They concluded that the non-beacon IEEE 802.15.4 results in 10 to 15 years sensor lifetime for low data rate and asymmetric WBAN traffic. However, their work considers data transmission on the basis of periodic intervals which is not a perfect scenario in a real WBAN. Furthermore, the data rate of in-body and on-body nodes are not always low, i.e., it ranges from 10 Kbps to 10 Mbps, and hence reduces the lifetime of the sensor nodes. Li et.al studied the behavior of slotted and unslotted CSMA/CA mechanisms and concluded that the unslotted mechanism performs better than the slotted one in terms of throughput and lat ency but with high cost of power consumption [8]. Intel Corporation conducted a series of experiments to analyze the performance of IEEE 802.15.4 for a WBAN [9]. They deployed a number of Intel Mote 2 [10] nodes on chest, waist, and the right ankle. Table 4 shows the throughput at a 0dBm transmit power when a person is standing and sitting on a chair. The connection between ankle and waist cannot be established, even for a short distance of 1.5m. All other connections show favourable performance. Dave et al. studied the energy efficiency and QoS performance of IEEE 802.15.4 and IEEE 802.11e [11] MAC protocols under two generic applications: a wave-form real time stream and a real-time parameter measurement stream [12]. Table 5 shows the throughput and the Power (in mW) for both applications. The AC_BE and AC_VO represent the access categories voice and best-effort in the IEEE 802.11e. Since the IEEE 802.15.4 operates in the 2.4 GHz unlicensed band, the possibilities of interference from other devices such as IEEE 802.11 and microwave are inevitable. A series of experiments to evaluate the impact of IEEE 802.11 and microwave ovens on the IEEE 802.15.4 transmission are carried out in [13]. The authors considered XBee 802.15.4 development kit that has two XBee modules. Table 6 shows the affects of microwave oven on the XBee remote module. When the microwave oven is ON, the packet success rate and the standard deviation is degraded to 96.85% and 3.22% respectively. However, there is no loss when the XBee modules are taken 2 meters away from the microwave oven. 3.2.2. Heartbeat Driven MAC Protocol (H-MAC) A Heartbeat Driven MAC protocol (H-MAC) [14] is a TDMA-based protocol originally proposed for a star topology WBAN. The energy efficiency is improved by exploiting heartbeat rhythm information in order to synchronize the nodes. The nodes do not need to receive periodic information to perform synchronization. The heartbeat rhythm can be extracted from the sensory data and hence all the rhythms represented by peak sequences are naturally synchronized. The H-MAC protocol assigns dedicated time slots to each node to guarantee collision-free transmission. In addition, this protocol is supported by an active synchronization recovery scheme where two resynchronization schemes are implemented. Although H-MAC protocol reduces the extra energy cost required for synchronization, it does not support sporadic events. Since the TDMA slots are dedicated and not traffic adaptive, H-MAC protocol encounters low spectral/bandwidth efficiency in case of a low traffic. For example, a blood pressure node may not need a dedicated time slot while an endoscope pill may require a number of dedicated time slots when deployed in a WBAN. But the slots should be released when the endoscope pill is expelled. The heartbeat rhythm information varies depending on the patient condition. It may not reveal valid information for synchronization all the time. One of the solutions is to assign the time slots based on the nodes traffic information and to receive synchronization packets when required, i.e., when a node has data to transmit/receive. 3.2.3. Reservation-based Dynamic TDMA Protocol (DTDMA) A Reservation-based Dynamic TDMA Protocol (DTDMA) [15] is originally proposed for a normal (periodic) WBAN traffic where slots are allocated to the nodes which have buffered packets and are released to other nodes when the data transmission/reception is completed. The channel is bounded by superframe structures. Each superframe consists of a beacon used to carry control information including slot allocation information, a CFP period a configurable period used for data transmission, a CAP period a fixed period used for short command packets using slotted aloha protocol, and a configurable inactive period used to save energy. Unlike a beacon-enabled IEEE 802.15.4 superframe structure where the CAP duration is followed by CFP duration, in DTDMA protocol the CFP duration is followed by CAP duration in order to enable the nodes to send CFP traffic earlier than CAP traffic. In addition, the duration of inactive period is configurable based on the CFP slot duration. If there is no CFP t raffic, the inactive period will be increased. The DTDMA superframe structure is given in 2(a). It has been shown that for a normal (periodic) traffic, the DTDMA protocol provides more dependability in terms of low packet dropping rate and low energy consumption when compared with IEEE 802.15.4. However, it does not support emergency and on-demand traffic. Although the slot allocation based on the traffic information is a good approach, the DTDMA protocol has several limitations when considered for the MICS band. The MICS band has ten channels where each channel has 300 Kbps bandwidth. The DTDMA protocol is valid only for one channel and cannot operate on ten channels simultaneously. In addition, the DTDMA protocol does not support the channel allocation mechanism in the MICS band. This protocol can be further investigated for the MICS band by integrating the channel information in the beacon frame. The new concept may be called Frequency-based DTDMA (F-DTDMA), i.e., the coordinator first selects one of the channels in the MICS band and then divides the selected channel in TDMA superframe (s) according to the DTDMA protocol. However the FCC has imposed several restrictions on the channel selection/allocation mechanism in the MICS band, which further creates problems for the MAC designers. 3.2.4. BodyMAC Protocol A BodyMAC protocol is a TDMA-based protocol where the channel is bounded by TDMA superframe structures with downlink and uplink subframes as given in 2(b) [16]. The downlink frame is used to accommodate the on-demand traffic and the uplink frame is used to accommodate the normal traffic. There is no proper mechanism to handle the emergency traffic. The uplink frame is further divided into CAP and CFP periods. The CAP period is used to transmit small size MAC packets. The CFP period is used to transmit the normal data in a TDMA slot. The duration of the downlink and uplink superframes are defined by the coordinator. The advantage of the BodyMAC protocol is that it accommodates the on-demand traffic using the downlink subframe. However, in case of low-power implants (which should not receive beacons periodically), the coordinator has to wake up the implant first and then send synchronization packets. After synchronization, the coordinator can request/send data in the downlink subframe. The wake up procedure for low-power implants is not defined in the BodyMAC protocol. One of the solutions is to use a wakeup radio in order to wake up low-power implants before using the downlink subframe. In addition the wakeup packets can be used to carry control information such as channel (MICS band) and slot allocation information from the coordinator to the nodes. Finally, the BodyMAC protocol uses the CSMA/CA protocol in the CAP period which is not reliable for a WBAN. This should be replaced by slotted-ALOHA as done in DTDMA. Further details on low-power MAC protocols (originally proposed for WSNs) for a WBAN are given in Appendix I. 3.3. Case Study: IEEE 802.15.4, PB-TDMA, and SMAC Protocols for a WBAN In this section, we investigate the performance of a beacon-enabled IEEE 802.15.4, preamble-based TDMA [17], and SMAC protocols for an on-body communication system. Our analysis is verified by extensive simulations using NS-2. The wireless physical parameters are considered according to a low-power Nordic nRF2401 transceiver (Chipcon CC2420 radio [18] is considered in case of IEEE 802.15.4) [19]. This radio transceiver operates in the 2.4-2.5 GHz band with an optimum transmission power of -5dBm. We use the shadowing propagation model throughout the simulations. We consider a total of 7 nodes firmly placed on a human body. The nodes are connected to the coordinator in a star topology. The distribution of the nodes and the coordinator is given in 3(a). The initial nodes energy is 5 Joules. The packet size is 120 bytes. The average data transmission rate of ECG, EEG, and EMG is 10, 70, and 100 kbps. The transport agent is a user datagram protocol (UDP). Since the traffic is an uplink t raffic, the buffer size at the coordinator is considered unlimited. In a real WBAN, the buffer size should be configurable based on the application requirements. For energy calculation, we use the existing energy model defined in NS-2. The simulation area is 33 meter and each node generates constant bit rate (CBR) traffic. The CBR traffic is an ideal model for some of the medical applications, where the nodes send data based on pre-defined traffic patterns. However, most of the nodes in a WBAN have heterogeneous traffic characteristics and they generate periodic and aperiodic traffic. In this case, they will have many traffic models operating at the same time, ranging from CBR to variable bit rate (VBR). 3(b) shows the throughput of the IEEE 802.15.4, PB-TDMA, and S-MAC protocols. The performance of the IEEE 802.15.4, when cond in a beacon-enabled mode, outperforms PB-TDMA and S-MAC protocols. The efficiency of a MAC protocol depends on the traffic pattern. In this case, S-MAC protocol results poor performance because the traffic scenario that we generated is not an ideal scenario for the S-MAC. 3(c) shows the residual energy at various nodes during simulation time. When nodes finish their transmission, they go into sleep mode, as indicated by the horizontal line. The coordinator has a considerable energy loss because it always listens to the other nodes. However, the energy consumption of the coordinator is not a critical issue in a WBAN. We further analyze the residual energy at the ECG node for different transmission powers. There is a minor change in energy loss for three different transmission powers as given in 3(d). This concludes that reducing the transmission power only d oes not save energy unless supported by an efficient power management scheme. The IEEE 802.15.4 can be considered for certain on-body medical applications, but it does not achieve the level of power required for in-body nodes. It is not sufficient for high data rate medical and non-medical applications due to its limitations to 250 kbps. Furthermore, it uses slotted or unslotted CSMA/CA where the nodes are required to sense the channel before transmission. However, the channel sensing is not guaranteed in MICS band because the path loss inside the human body due to tissue heating is much higher than in free space. Bin et.al studied the clear channel assessment (CCA) range of in-body nodes which is only 0.5 meters [20]. This unreliability in CCA indicates that CSMA/CA is not an ideal technique for the in-body communication system. An alternative approach is to use a TDMA-based protocol that contains a beacon, a configurable contention access period (CCAP), and a contention free period (CFP) [21]. Unlike the IEEE 802.15.4, this protocol is required to use a slot ted-ALOHA protocol in the CCAP instead of CSMA/CA. The CCAP period should contain few slots (3 or 4) of equal duration and can be used for short data transmission and a guaranteed time slot (GTS) allocation. To enable a logical connection between the in-body and the on-body communication systems, a method called bridging function can be used as discussed in [21]. The bridging function can integrate in-body and on-body nodes into a WBAN, thus satisfying the MAC transparency requirement. Further details about bridging function are given in [22]. 3.4. Discussion Since the CSMA/CA is not suitable due to unreliable CCA and heavy collision problems, it can be seen that the most reliable power-efficient protocol is a TDMA-based protocol. Many protocols have been proposed for a WBAN and most of them are based on a TDMA-based mechanism. However, all of them have pros and cons for a real WBAN system that should operate on Multi-PHYs (MICS, ISM, and UWB) simultaneously. The MAC transparency has been a hot topic for the MAC designers since different bands have different characteristics in terms of data rate, number of channels in a particular frequency band, and data prioritization. A good MAC protocol should enable reliable operation on MICS, ISM, and UWB etc bands simultaneously. The main problems are related to MICS band due to FCC restrictions [23]. According to FCC, â€Å"Within 5 seconds prior to initiating a communications session, circuitry associated with a medical implant programmer/control transmitter must monitor the channel or channels the MICS system devices intend to occupy for a minimum of 10 milliseconds per channel.† In other words, the coordinator must perform Listen-before-talking (LBT) criteria prior to a MICS communication sessions. The implants are not allowed to On the Implant Communication and MAC Protocols for a WBAN On the Implant Communication and MAC Protocols for a WBAN Abstract Recent advances in micro-electro-mechanical systems (MEMS), wireless communication, low-power intelligent sensors, and semiconductor technologies have allowed the realization of a wireless body area network (WBAN). A WBAN provides unobtrusive health monitoring for a long period of time with real-time updates to the physician. It is widely used for ubiquitous healthcare, entertainment, and military applications. The implantable and wearable medical devices have several critical requirements such as power consumption, data rate, size, and low-power medium access control (MAC) protocols. This article consists of two parts: body implant communication, which is concerned with the communication to and from a human body using RF technology, and WBAN MAC protocols, which presents several low-power MAC protocols for a WBAN with useful guidelines. In body implant communication, the in-body radio frequency (RF) performance is affected considerably by the implants depth inside the human body as well as by the muscle and fat. We observe best performance at a depth of 3cm and not close to the human skin. Furthermore, the study of low-power MAC protocols highlights the most important aspects of developing a single, a low-power, and a reliable MAC protocol for a WBAN. Keywords: In-body, on-body, RF communication, Implant, WBAN 1. Introduction Cardiovascular diseases are the foremost cause of deaths in the United States and Europe since 1900. More than ten million people are affected in Europe, one million in the US, and twenty two million people in the world [1]. The number is projected to be triple by 2020, resulting in an expenditure of around 20% of the gross domestic product (GDP). The ratio is 17% in South Korea and 39% in the UK [2]. The healthcare expenditure in the US is expected to be increased from $2.9 trillion in 2009 to $4 trillion US dollars in 2015 [3]. The impending health crisis attracts researchers, industrialists, and economists towards optimal and quick health solutions. The non-intrusive and ambulatory health monitoring of patients vital signs with real time updates of medical records via internet provide economical solutions to the health care systems. A wireless body area network (WBAN) is becoming increasingly important for healthcare systems, sporting activities, and members of emergency as well as military services. WBAN is an integration of in-body (implants) and on-body (wearable) sensors that allow inexpensive, unobtrusive, and long-term health monitoring of a patient during normal daily activities for prolonged periods of time. In-body radio frequency (RF) communications have the potential to dramatically change the future of healthcare. For example, they allow an implanted pacemaker to regularly transmit performance data and the patients health status to the physician. However, the human body poses many wireless transmission challenges. This is partially conductive and consists of materials having different dielectric constants and characteristics impedance. The interface of muscles and fats may reflect the RF wave rather than transmitting it. The key elements of an RF-linked implant are the in-body antenna and the communi cation link performance. Also, in the case of many implants and wearable sensors, a low-power MAC protocol is required to accommodate the heterogeneous traffic in a power-efficient manner. This article is divided into two parts: body implant communication and WBAN MAC protocols. In the body implant communication part, we look at the RF communication link performance at various depths inside a human (artificial) body. In the MAC part, we review the existing low-power MAC protocols and discuss their pros and cons in the context of a WBAN. We further provide alternative MAC solutions for in-body and on-body communication systems. The rest of the article is divided into three sections. In section 2, we present a discussion on body implant communication including in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. Section 3 discusses several low-power MAC protocols and realizes a need for a new, a low-power, and a reliable MAC protocol for a WBAN. The final section concludes our work. 2. Body Implant Communication There are several ways to communicate with an implant that includes the use of electromagnetic induction and RF technology. Both are wireless and their use depends on the application requirements. Further, the key elements of an RF-linked implant are the in-body antenna and the communication link performance. The following part discusses in-body electromagnetic induction, RF communication, antenna design, and the communication link performance. 2.1. In-body Electromagnetic Induction Several applications still use electromagnetic coupling to provide a communication link to an implant device. In this scheme, an external coil is held very close to the body that couples to a coil implanted just below the skin surface. The implant is powered by the coupled magnetic field and requires no battery for communication. Data is transferred from the implant by altering the impedance of the implanted loop that is detected by the external coil and electronics. This type of communication is commonly used to identify animals that have been injected with an electronic tag. Electromagnetic induction is used when continuous, long-term communication is required. The base band for electromagnetic communication is typically 13.56 MHz or 28 MHz, with other frequencies also available. The choice of a particular band is subject to regulation for maximum specific absorption rate (SAR). The inductive coupling achieves best power transfer efficiency when uses large transmit and receive coil s. It, however, becomes less efficient when the space is an issue of the device is implanted deep inside the human body. Furthermore, inductive coupling technique does not support a very high data rate and cannot initiate a communication session from inside of the body. 2.2. In-body RF Communication Compared with the electromagnetic induction, RF communication dramatically increases bandwidth and supports a two-way data communication. The band designated for the in-body RF communication is medical implant communication service (MICS) band and is around 403 to 405 MHz. This band has a power limit of 25  µW in the air and is usually split into ten channels of 300 kHz bandwidth each. The human body is a medium that poses numerous wireless transmission challenges. It consists of various components that are not predictable and will change as the patient ages, gains or losses weight, or even changes posture. Values of dielectric constant (ÃŽ µr), conductivity (ÏÆ') and characteristic impedance (Zo) for some body tissue are given in table 1 [4]. This demonstrates that these two tissue types are very different. Also, the dielectric constant affects the wavelength of a signal. At 403 MHz, the wavelength in the air is 744mm, but in muscle with ÃŽ µr = 50 the wavelength reduces to 105mm, which helps in designing implanted antennas. 2.3. In-body Antenna Design A modern in-body antenna should be tuneable by using an intelligent transceiver and software routine. This enables the antenna coupling circuit to be optimised. Due to the frequency, and available volume, a non-resonant antenna is commonly used. It has a lower gain than a resonant antenna. This makes design of the antenna coupling circuit very important. Antenna options are dictated by the location of the implant. A patch antenna can be used when the implant is flat. Patch antennas are comprised of a flat insulating substrate coated on both sides with a conductor. The substrate is a body compatible material with a platinum or a platinum/iridium conductor. The upper surface is the active face and is connected to the transceiver. The connection to the transceiver needs to pass through the case where the hermetic seal is maintained, requiring a feed-through. The feed-through must have no filter capacitors present; these are common on other devices. An implanted patch antenna is electrically larger than its physical size because it is immersed in a high (ÃŽ µr) medium. It can be much larger electrically if the substrate is of higher (ÃŽ µr), such as titania or zirconia. A loop antenna can also be attached to the implant. This antenna operates mostly by the magnetic field, whereas the patch operates mostly by the electric field. The loop antenna delivers performance comparable to that of a dipole, but with a considerably smaller size. In addition, the magnetic permeability of muscle or fat is very similar to that of an air, unlike the dielectric constant that varies considerably. This property enables an antenna to be built and used with much less need for retuning. A loop antenna can be mounted on the case in a biocompatible structure. 2.4. In-body Link Performance The demonstration system consists of a base-station, an implant, antennas, and a controlling laptop. The base-station contains a printed circuit board (PCB) with a wakeup RF circuit, a Zarlink ZL70101 IC, and a micro-controller. It sends a wakeup signal on industrial, scientific, and medical (ISM) 2.4 GHz band to power up the implant to communicate. It also supports communication within the MICS band. The implant contains a Zarlink ZL70101 IC, a micro-controller, and a battery. The power limits of the wakeup signal for ISM and MICS bands transmitters are 100mW and 25  µW respectively. Experiments that measure the performance of an implant inside a living body are difficult to arrange. The alternative is to use 3D simulation software or a body phantom defined in [5]. The use of 3D simulation software is time consuming and hence practically not valuable. Therefore, measurements are generally performed using the body phantom and immersing a battery-powered implant into it [6]. Since no additional cables are attached to the test implant, the interference errors in the measurements are minimal. The body phantom is filled with a liquid that mimics the electrical properties of the human body tissues. The test environment is an anechoic chamber that includes a screened room. The interior walls of the room have sound-absorbent cones to minimize any reflections from walls or the floor that could distort the results. In real life, however, the results will be affected by the reflections from walls, desks, and other equipment and hardware. The body phantom is mounted on a woo den stand (non-conductive). The distance from the body phantom to the base-station is 3m. The MICS base-station dipole antenna is mounted on a stand. 1(a) shows the anechoic chamber with a body phantom (on the wooden stand), a log periodic test antenna (foreground), and a base-station dipole (right). The log periodic antenna is used to calculate the power radiated from the body phantom. A depth is defined as the horizontal distance between the outer skin of the phantom and the test implant. Vertical polarization of the implant is the case when the long side of the box and the patch antenna is vertical. The link performance is measured once the communication link is established. The measurements include the effective radiated power (ERP) from the implant, the received signal at the implant from the base-station, and the link quality. Measurements are made over a set distance with all the combinations of implant and test antenna polarisations, i.e., vertical-vertical (V-V), horizontal-vertical (H-V), vertical-horizontal (V-H), and horizontal-horizontal (H-H) polarisations. Typical results are shown in 1(b) where the ERP is calculated from the received signal power and the antenna characteristics. The measurement of the signal levels is done with the log periodic antenna and the spectrum analyzer. It can be seen in the that there is a significant difference in signal levels with polarisation combinations and depths. For a V-V polarisation, the ERP increases from a 1cm depth to a maximum between 2 and 7 cm, and then it decreases. The gradual increase is due to the simulated body acti ng as a parasitic antenna. The also shows how the signal level is affected by the depth with different polarisation. Such a test needs to be done with the antenna that is to be used in the final product. To measure the received signal at the implant, the Zarlink ZL70101 has an inbuilt receive signal strength indication (RSSI) function that gives a measure of the signal level detected. RSSI is a relative measurement with no calibration. The implant receives and measures a continuous wave signal transmitted by the base-station. In this case, the implant and the base-station antennas are vertically polarised. 1(c) shows an increase in the signal level at a depth between 3 and 4cm for a 15dec power. The power settings refer to the base-station and are cond to set the ERP to 25  µW. Signal levels are not valuable unless they are related to data transmission. One way to maintain the link quality is to measure the number of times the error correction is invoked during the transmission of 100 blocks of data. Two types of error correction codes, i.e., error correction code (ECC) and cyclic redundancy code (CRC) are invoked to maintain data integrity and reliability. The fewer ECC and CRC invocations result in better link quality. In 1(d), the error correction is lowest at a depth between 3 and 5 cm. A sample of ECC data collected at a 3cm implant depth is given in Table 2. The Count indicates the number of data blocks, the Time (ms) indicates the block transmission time, and the ECC indicates the number of times it is invoked. During the transmission of 100 blocks of data at a 3cm depth, the ECC is invoked 368 times, which is further equivalent to an average 3.68 times (as given in 1(d)). 2.5. Discussion The ERP, RSSI, as well as the ECC and CRC plots show that the implant demonstrates the best performance at a depth between 3 and 5 cm. The depth and position of an implant is not chosen for engineering performance but for the best clinical reasons. The implant designer must be aware of the possible losses through the human body. The attenuation and the parasitic antenna effects vary from patient to patient, with the position of the implant and with the time as the patient gains, or looses weight. Therefore, these factors need to be built into the link budget. 3. WBAN MAC Protocols Some of the common objectives in a WBAN are to achieve maximum throughput, minimum delay, and to maximize the network lifetime by controlling the main sources of energy waste, i.e., collision, idle listening, overhearing, and control packet overhead. A collision occurs when more than one packet transmits data at the same time. The collided packets have to be retransmitted, which consumes extra energy. The second source of energy waste is idle listening, meaning that a node listens to an idle channel to receive data. The third source is overhearing, i.e., to receive packets that are destined to other nodes. The last source is control packet overhead, meaning that control information area added to the payload. Minimal number of control packets should be used for data transmission. Generally MAC protocols are grouped into contention-based and schedule-based MAC protocols. In contention-based MAC protocols such as carrier sense multiple access/collision avoidance (CSMA/CA) protocols, nodes contend for the channel to transmit data. If the channel is busy, the node defers its transmission until it becomes idle. These protocols are scalable with no strict time synchronization constraint. However, they incur significant protocol overhead. In schedule-based protocols such as time division multiple access (TDMA) protocols, the channel is divided into time slots of fixed or variable duration. These slots are assigned to nodes and each node transmits during its slot period. These protocols are energy conserving protocols. Since the duty cycle of radio is reduced, there is no contention, idle listening and overhearing problems. But these protocols require frequent synchronization. Table 3 compares CSMA/CA and TDMA protocols. 3.1. WBAN MAC Requirements The most important attribute of a good MAC protocol for a WBAN is energy efficiency. In some applications, the device should support a battery life of months or years without interventions, while others may require a battery life of tens of hours due to the nature of the applications. For example, cardiac defibrillators and pacemakers should have a lifetime of more than 5 years, while swallowable camera pills have a lifetime of 12 hours. Power-efficient and flexible duty cycling techniques are required to minimize the idle listening, overhearing, packet collisions and control packet overhead. Furthermore, low duty cycle nodes should not receive frequent synchronization and control information (beacon frames) if they have no data to send or receive. The WBAN MAC should also support simultaneous operation on in-body (MICS) and on-body channels (ISM or UWB) at the same time. In other words, it should support multiple physical layer (Multi-PHYs) communication or MAC transparency. Other important factors are scalability and adaptability to changes in the network, delay, throughput, and bandwidth utilization. Changes in the network topology, the position of the human body, and the node density should be handled rapidly and successfully. The MAC protocol for a WBAN should consider the electrical properties of the human body and the diverse traffic nature of in-body and on-body nodes. For example, the data rate of in-body nodes varies, ranging from few kbps in pacemaker to several Mbps in capsular endoscope. In the following sections, we discuss proposed MAC protocols for a WBAN with useful guidelines. We also present a case study of IEEE 802.15.4, PB-TDMA, and S-MAC protocols for a WBAN using NS2 simulator. 3.2. Proposed MAC Protocols for a WBAN In this section, we study proposed MAC protocols for a WBAN followed by useful suggestions/comments. Many of the proposed MAC protocols are the extension of existing MAC protocols originally proposed for wireless sensor networks (WSNs). 3.2.1. IEEE 802.15.4 IEEE 802.15.4 has remained the main focus of many researchers during the past few years. Some of the main reasons of selecting IEEE 802.15.4 for a WBAN were low-power communication and support of low data rate WBAN applications. Nicolas et.al investigated the performance of a non-beacon IEEE 802.15.4 in [7], where low upload/download rates (mostly per hour) are considered. They concluded that the non-beacon IEEE 802.15.4 results in 10 to 15 years sensor lifetime for low data rate and asymmetric WBAN traffic. However, their work considers data transmission on the basis of periodic intervals which is not a perfect scenario in a real WBAN. Furthermore, the data rate of in-body and on-body nodes are not always low, i.e., it ranges from 10 Kbps to 10 Mbps, and hence reduces the lifetime of the sensor nodes. Li et.al studied the behavior of slotted and unslotted CSMA/CA mechanisms and concluded that the unslotted mechanism performs better than the slotted one in terms of throughput and lat ency but with high cost of power consumption [8]. Intel Corporation conducted a series of experiments to analyze the performance of IEEE 802.15.4 for a WBAN [9]. They deployed a number of Intel Mote 2 [10] nodes on chest, waist, and the right ankle. Table 4 shows the throughput at a 0dBm transmit power when a person is standing and sitting on a chair. The connection between ankle and waist cannot be established, even for a short distance of 1.5m. All other connections show favourable performance. Dave et al. studied the energy efficiency and QoS performance of IEEE 802.15.4 and IEEE 802.11e [11] MAC protocols under two generic applications: a wave-form real time stream and a real-time parameter measurement stream [12]. Table 5 shows the throughput and the Power (in mW) for both applications. The AC_BE and AC_VO represent the access categories voice and best-effort in the IEEE 802.11e. Since the IEEE 802.15.4 operates in the 2.4 GHz unlicensed band, the possibilities of interference from other devices such as IEEE 802.11 and microwave are inevitable. A series of experiments to evaluate the impact of IEEE 802.11 and microwave ovens on the IEEE 802.15.4 transmission are carried out in [13]. The authors considered XBee 802.15.4 development kit that has two XBee modules. Table 6 shows the affects of microwave oven on the XBee remote module. When the microwave oven is ON, the packet success rate and the standard deviation is degraded to 96.85% and 3.22% respectively. However, there is no loss when the XBee modules are taken 2 meters away from the microwave oven. 3.2.2. Heartbeat Driven MAC Protocol (H-MAC) A Heartbeat Driven MAC protocol (H-MAC) [14] is a TDMA-based protocol originally proposed for a star topology WBAN. The energy efficiency is improved by exploiting heartbeat rhythm information in order to synchronize the nodes. The nodes do not need to receive periodic information to perform synchronization. The heartbeat rhythm can be extracted from the sensory data and hence all the rhythms represented by peak sequences are naturally synchronized. The H-MAC protocol assigns dedicated time slots to each node to guarantee collision-free transmission. In addition, this protocol is supported by an active synchronization recovery scheme where two resynchronization schemes are implemented. Although H-MAC protocol reduces the extra energy cost required for synchronization, it does not support sporadic events. Since the TDMA slots are dedicated and not traffic adaptive, H-MAC protocol encounters low spectral/bandwidth efficiency in case of a low traffic. For example, a blood pressure node may not need a dedicated time slot while an endoscope pill may require a number of dedicated time slots when deployed in a WBAN. But the slots should be released when the endoscope pill is expelled. The heartbeat rhythm information varies depending on the patient condition. It may not reveal valid information for synchronization all the time. One of the solutions is to assign the time slots based on the nodes traffic information and to receive synchronization packets when required, i.e., when a node has data to transmit/receive. 3.2.3. Reservation-based Dynamic TDMA Protocol (DTDMA) A Reservation-based Dynamic TDMA Protocol (DTDMA) [15] is originally proposed for a normal (periodic) WBAN traffic where slots are allocated to the nodes which have buffered packets and are released to other nodes when the data transmission/reception is completed. The channel is bounded by superframe structures. Each superframe consists of a beacon used to carry control information including slot allocation information, a CFP period a configurable period used for data transmission, a CAP period a fixed period used for short command packets using slotted aloha protocol, and a configurable inactive period used to save energy. Unlike a beacon-enabled IEEE 802.15.4 superframe structure where the CAP duration is followed by CFP duration, in DTDMA protocol the CFP duration is followed by CAP duration in order to enable the nodes to send CFP traffic earlier than CAP traffic. In addition, the duration of inactive period is configurable based on the CFP slot duration. If there is no CFP t raffic, the inactive period will be increased. The DTDMA superframe structure is given in 2(a). It has been shown that for a normal (periodic) traffic, the DTDMA protocol provides more dependability in terms of low packet dropping rate and low energy consumption when compared with IEEE 802.15.4. However, it does not support emergency and on-demand traffic. Although the slot allocation based on the traffic information is a good approach, the DTDMA protocol has several limitations when considered for the MICS band. The MICS band has ten channels where each channel has 300 Kbps bandwidth. The DTDMA protocol is valid only for one channel and cannot operate on ten channels simultaneously. In addition, the DTDMA protocol does not support the channel allocation mechanism in the MICS band. This protocol can be further investigated for the MICS band by integrating the channel information in the beacon frame. The new concept may be called Frequency-based DTDMA (F-DTDMA), i.e., the coordinator first selects one of the channels in the MICS band and then divides the selected channel in TDMA superframe (s) according to the DTDMA protocol. However the FCC has imposed several restrictions on the channel selection/allocation mechanism in the MICS band, which further creates problems for the MAC designers. 3.2.4. BodyMAC Protocol A BodyMAC protocol is a TDMA-based protocol where the channel is bounded by TDMA superframe structures with downlink and uplink subframes as given in 2(b) [16]. The downlink frame is used to accommodate the on-demand traffic and the uplink frame is used to accommodate the normal traffic. There is no proper mechanism to handle the emergency traffic. The uplink frame is further divided into CAP and CFP periods. The CAP period is used to transmit small size MAC packets. The CFP period is used to transmit the normal data in a TDMA slot. The duration of the downlink and uplink superframes are defined by the coordinator. The advantage of the BodyMAC protocol is that it accommodates the on-demand traffic using the downlink subframe. However, in case of low-power implants (which should not receive beacons periodically), the coordinator has to wake up the implant first and then send synchronization packets. After synchronization, the coordinator can request/send data in the downlink subframe. The wake up procedure for low-power implants is not defined in the BodyMAC protocol. One of the solutions is to use a wakeup radio in order to wake up low-power implants before using the downlink subframe. In addition the wakeup packets can be used to carry control information such as channel (MICS band) and slot allocation information from the coordinator to the nodes. Finally, the BodyMAC protocol uses the CSMA/CA protocol in the CAP period which is not reliable for a WBAN. This should be replaced by slotted-ALOHA as done in DTDMA. Further details on low-power MAC protocols (originally proposed for WSNs) for a WBAN are given in Appendix I. 3.3. Case Study: IEEE 802.15.4, PB-TDMA, and SMAC Protocols for a WBAN In this section, we investigate the performance of a beacon-enabled IEEE 802.15.4, preamble-based TDMA [17], and SMAC protocols for an on-body communication system. Our analysis is verified by extensive simulations using NS-2. The wireless physical parameters are considered according to a low-power Nordic nRF2401 transceiver (Chipcon CC2420 radio [18] is considered in case of IEEE 802.15.4) [19]. This radio transceiver operates in the 2.4-2.5 GHz band with an optimum transmission power of -5dBm. We use the shadowing propagation model throughout the simulations. We consider a total of 7 nodes firmly placed on a human body. The nodes are connected to the coordinator in a star topology. The distribution of the nodes and the coordinator is given in 3(a). The initial nodes energy is 5 Joules. The packet size is 120 bytes. The average data transmission rate of ECG, EEG, and EMG is 10, 70, and 100 kbps. The transport agent is a user datagram protocol (UDP). Since the traffic is an uplink t raffic, the buffer size at the coordinator is considered unlimited. In a real WBAN, the buffer size should be configurable based on the application requirements. For energy calculation, we use the existing energy model defined in NS-2. The simulation area is 33 meter and each node generates constant bit rate (CBR) traffic. The CBR traffic is an ideal model for some of the medical applications, where the nodes send data based on pre-defined traffic patterns. However, most of the nodes in a WBAN have heterogeneous traffic characteristics and they generate periodic and aperiodic traffic. In this case, they will have many traffic models operating at the same time, ranging from CBR to variable bit rate (VBR). 3(b) shows the throughput of the IEEE 802.15.4, PB-TDMA, and S-MAC protocols. The performance of the IEEE 802.15.4, when cond in a beacon-enabled mode, outperforms PB-TDMA and S-MAC protocols. The efficiency of a MAC protocol depends on the traffic pattern. In this case, S-MAC protocol results poor performance because the traffic scenario that we generated is not an ideal scenario for the S-MAC. 3(c) shows the residual energy at various nodes during simulation time. When nodes finish their transmission, they go into sleep mode, as indicated by the horizontal line. The coordinator has a considerable energy loss because it always listens to the other nodes. However, the energy consumption of the coordinator is not a critical issue in a WBAN. We further analyze the residual energy at the ECG node for different transmission powers. There is a minor change in energy loss for three different transmission powers as given in 3(d). This concludes that reducing the transmission power only d oes not save energy unless supported by an efficient power management scheme. The IEEE 802.15.4 can be considered for certain on-body medical applications, but it does not achieve the level of power required for in-body nodes. It is not sufficient for high data rate medical and non-medical applications due to its limitations to 250 kbps. Furthermore, it uses slotted or unslotted CSMA/CA where the nodes are required to sense the channel before transmission. However, the channel sensing is not guaranteed in MICS band because the path loss inside the human body due to tissue heating is much higher than in free space. Bin et.al studied the clear channel assessment (CCA) range of in-body nodes which is only 0.5 meters [20]. This unreliability in CCA indicates that CSMA/CA is not an ideal technique for the in-body communication system. An alternative approach is to use a TDMA-based protocol that contains a beacon, a configurable contention access period (CCAP), and a contention free period (CFP) [21]. Unlike the IEEE 802.15.4, this protocol is required to use a slot ted-ALOHA protocol in the CCAP instead of CSMA/CA. The CCAP period should contain few slots (3 or 4) of equal duration and can be used for short data transmission and a guaranteed time slot (GTS) allocation. To enable a logical connection between the in-body and the on-body communication systems, a method called bridging function can be used as discussed in [21]. The bridging function can integrate in-body and on-body nodes into a WBAN, thus satisfying the MAC transparency requirement. Further details about bridging function are given in [22]. 3.4. Discussion Since the CSMA/CA is not suitable due to unreliable CCA and heavy collision problems, it can be seen that the most reliable power-efficient protocol is a TDMA-based protocol. Many protocols have been proposed for a WBAN and most of them are based on a TDMA-based mechanism. However, all of them have pros and cons for a real WBAN system that should operate on Multi-PHYs (MICS, ISM, and UWB) simultaneously. The MAC transparency has been a hot topic for the MAC designers since different bands have different characteristics in terms of data rate, number of channels in a particular frequency band, and data prioritization. A good MAC protocol should enable reliable operation on MICS, ISM, and UWB etc bands simultaneously. The main problems are related to MICS band due to FCC restrictions [23]. According to FCC, â€Å"Within 5 seconds prior to initiating a communications session, circuitry associated with a medical implant programmer/control transmitter must monitor the channel or channels the MICS system devices intend to occupy for a minimum of 10 milliseconds per channel.† In other words, the coordinator must perform Listen-before-talking (LBT) criteria prior to a MICS communication sessions. The implants are not allowed to

Mycosis Fungoides Essay -- Biology, T Cells

Mycosis fungoides is a main subtype of a cutaneous T cell lymphoma (CTCL), in which a heterogeneous collection of lymphomas develop into malignant cancer cells, primarily affecting the skin. This disease can be distinguished from other cutaneous T cell lymphomas by its unique clinical and histologic features (Armitage et al., 2010). Mycosis fungoides can be treated several different ways and is dependent on several factors such as the stage of the cancer, health of the patient, presenting symptoms and patient-specific issues (Parker & Bradley, 2006). Traditional therapies for mycosis fungoides involved radiation therapy, oral psoralen with UVA light therapy and narrow- and broadband UVB light therapy. Recently, novel therapies have been established to treat CTCL and several of them are starting to become routine therapies for the erythrodermic subgroup of mycosis fungoides. This paper will discuss the historical background of the disease as well as the new techniques that have been u sed within the past few years and the traditional methods of treatment. T cells are genetically prepared to protect and survey the human body from any environmental stressors, foreign agents and malignancy. Some of these T cells are programmed to protect the skin. Once the body is infected with T lymphocytes, the T cells infiltrate the skin, work together to eradicate the allergen and eventually they undergo the process of natural cell death. However, when specific skin-homing T lymphocytes infect the skin, they then clonally expand and are sometimes unable to exit the skin compartment. Once the lymphocytes accumulate within the skin, the reaction is then known as a rash. This proliferation of abnormal cloning of T cells within the skin distinguishes ... ...ter researching mycosis fungoides, I have learned that the cause of this disease is unknown and unless detected at an early stage, it is most likely not curable. What are fortunate for patients with mycosis fungoides are the numerous therapeutic options which I find to be remarkable. Since the treatment options are mainly palliative, I have realized the goals of therapy for this disease are symptom relief and consideration for their quality of life. Although most techniques are chosen based upon clinical stage of the disease, what I find most promising is total skin electron beam radiation therapy. With this type of technology being around for several years, and continuously updating to modern techniques, I find it most beneficial to patients. However, there are several options available for patients and being able to combine different therapies is in their favor.

Family Day Essay -- essays research papers

  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   Family Day When I was around 6, I had gotten out of church wearing my nice church clothes with a tie, shoes, dressy pants, and a blazer. I was with my mom, dad, brother, and sister, who all had on church clothes too. My sister had the same things my mom had on, a black long skirt with an expensive white shirt. My brother and dad had on the same thing too: black shoes, navy blue pants, black bowtie and white shirt. I was the only one with a blazer on. My siblings and I were really happy we all went to church together, so I guess my dad was happy because of that, but he had a tired look on his face too.   Ã‚  Ã‚  Ã‚  Ã‚  After church, my parents decided we should go to the botanical gardens and spend the rest of the day there. My dad had an old Chevy that sounded pretty good; it got us where we needed to go. It had some rust on the edges here and there, but all and all it was a good running car. The inside smelled like pine because my dad washed the car that mourning and he always bought a freshener to make it smell like that. I never knew why he liked that smell because I hated it; it always got me sick in that car, but today I didn’t mind because we were going to have a fun time in the Botanical Gardens.   Ã‚  Ã‚  Ã‚  Ã‚  The Botanical Gardens had a parking lot in front but you had to pay to get in. My dad was too cheap to pay, so he just parked it outside th...