The Cinematic Spectator

The Cinematic attestatorThe cinematic spectatorBoth Hugo Munsterberg and Rudolf Arnheim took particular interest in the cinematic spectator and how the moving pictures on the screen affected them. Through close psychological analysis and the formulation of processes, each had their own get on the spectators intricacy in the cinematic view. Through close analysis we can get an acuteness and cle arer understanding of why people are drawn to motion pictures and what happens to them when they arrive.Munsterberg describes viewing as an aesthetic take in while Arnheim deems it an unreal experience. This aesthetic experience Munsterberg acknowledges is where the film is a detachment or isolation from our passing(a) routine and real time and public are left behind, an experience that is entirely self contained (Andrew, 26). This experience begins when the picture does as slowly the spectator is dis followd from their reality and engaging with the reality on the screen. They are c loy in perceiving everything during that moment, isolated from all outer surroundings. This experience, check to Munsterberg, is attained through ones mind and this was the foundation for his conclusions. found in Gestalt psychology, Munsterberg saw the mind composed as several levels where the higher were dependent on the operating theatre and functionality of the lower. When each level was engaged, the spectator could fully engage with the picture by resolving what Munsterberg referred to as undistinguished stimuli, subconscious renderings that are summoned while viewing the work, creating a world which one could relate emotionally to the events and objects. The spectators mind, according to Munsterberg, then creates an internal object through a phi-phenomenon where emphasis is placed on the active powers of the spectator giving the film fluidity by bringing the mind to a state of full engagement and contentment, mentally held in a state of rapt attention. Munsterberg writes we do non see objective reality but a product of our own mind which binds the pictures together (The Means of the Photoplay, 411-412) which is accomplished through the convey of what Munsterberg deemed photoplay. Photoplay tells the story of the outside world through the manipulation of events to the forms of the world on the screen. This is accomplished by winning the outer space, time, and causality and adjusting the inners attention, memory, imagination and emotion. He sees the spectator as one who undergoes a psychological connectedness with the moving foresees presented on the screen and draws rational relations to them through their own personal experiences. Rudolph Arnheim sees the spectator as an active watchman who pays attention to the films form. He feels the meaning is a pattern rather than individual stimuli and shifts the pore a management from the psychological side, Munsterbergs main basis, and shifts the focus to the material itself, the happenings of the film . This material Arnheim claims must be all factors which have got it a less than perfect illusion of reality (Andrew, 28). This unreality takes on all aspects of the culture medium by manipulating the film elements such as projection, reduction, lighting, color, framing and editing. The artist controls and manipulates these elements for their own expression in trying to tell the story and to keep the viewer interested in what is presented on the screen. These aspects also mend up the model of what Arnheim deemed film art. Arnheim says film art is based on the manipulation of the technically visible, not the humanly ocular (Andrew, 29) meaning the elements and technical aspects used to create the medium must be manipulated in a way which tap into human emotions, experiences and surroundings. Trying to present these elements, however, did not come without limitations, which challenged the artists and their limits of expression. When all of the elements were presented in cohesion, Arnheim say the viewer underwent a transformation. This is shown clearly in Charlie Chaplins 1936 film Modern Times where the viewer is able to fully engage with the main character as he gracefully fumbles through his work day around the factory. We are transformed from our everyday lives into this comedic wonderland and are left wanting more.During the 1920s and 30s, spectators along with the artists were still adapting to this developing medium. line drawing and projecting posed a challenge for the filmmakers as to how they were going to take a 3D image to 2 dimensional and still be able to express themselves artistically. Arnheims take was art begins where mechanical procreation leaves off, where the conditions of reproductions serve in some way to mold the object. And the spectator shows himself to be lacking in straight-laced aesthetic appreciation when he is satisfied to see the picture as purely objective (PP, 1933 edition, 68-69). Since the images forever and a day movi ng and portraying body language, facial expressions and interacting with other things, the viewer must be active and engaged, not just observing the film for its images. Our eyes work with our other senses which allow us to experience the medium itself while we become lost in the illusion on the screen. These are the means by which Arnheim said the spectator can treat the film as such rather than reality. There are more reasons people were and still are drawn to motion pictures. We are mesmerized by the stories, images and meanings. The cinematic experience is of both mind and body. We draw from our life experiences, memories and knowledge and are transcended into another world. The experience heightens the senses it can make you laugh or cry, leave you happy or sad. The images and thoughts from our own minds are activated and we relate to them sack on the screen. We live vicariously through the character(s) for that moment in time, we are detached from reality, emotionally attach ed, transcended from our daily routines.

Article Analysis on the Global Economic Crisis

Article Analysis on the demesnewide Economic CrisisTable of ContentsINTRODUCTIONGLOBAL BANKS A WORLD OF PAINCitigroup Citi never reapsGreece rescue Running on EmptyCONCLUSIONBibliographyINTRODUCTIONThis paper is about the discussion on the upstart the economist article based on orbiculate depository financial institutions a world of pain, Citi group Citi never reaps and Greece frugality running on empty.GLOBAL BANKS A WORLD OF PAING1Bail-out big banksIn my opinion, the bailout happens, when the bills of the bank is in the struggling entity to prevent its complete collapse. The world largest banks are connected through a mesh of briefly term loans which provide credit guarantee and financial contracts of others. This connection is a risky one that toilette also be a cause for a big bank to bail out. The economic crisis whitethorn also happen because of the doubts aroused in the ability of a single financial fuddled to reserve its prescribed responsibility and to re salar y their loan. The bank regulation can improve in requiring some appropriate ratio during the thriving ages. Another way is to limit the percentage funding which come from the short time money interbreedinget. (Pettinger 2009)Giant Firms proved hard to manage subsidiaries and struggled to be built common systemIn my opinion, the giant firm may fail to build a common system may be because of the disappointed employees of the firm which may be because of the rules. The big firm wont be having replete time to check whether the highly talented employee is working for the good on-going project and to know whether he is snug with that or not. I also feel that good discussion is a well tell deterrent example for the consistent growth of the firm. So these giant firms might have not followed the discussion process properly. antecedency should also be given for the talented employees to work for the wellness of the firm. The mission and vision should be intelligibly set and the execu tion of the process for it should be done accordingly to make their work more lightsome and it go forth also pave way for building common system.Basel 3 and complicated regulation and enlarge the costIn my opinion, the global and the liquidity rule (Basel 3) can be focussed better than they do now. all(a) the banks bequeath face a strict regulation because of the late liquidity standard, the risk coverage, and the new leverage ratio. Because of the bank bully will also decrease along with the increase in capital ratio for the upcoming years. This will cause problem for some banks. I feel that bank will experience the pressure on Return of Equity (ROE) because of the increase in the capital and the liquidity cost. For this bank have to work in a number of areas and have to work on Basel 3 issues and they have to set priority for the close, mid and for the longer term.Citigroup Citi never reapsG2G3In my opinion, I agree that the Citi bank had money but they are still in a questi on of knowing how the straggling financial firm turn out to be. It had a good growth. According to George Moore the chairman of new look committee said that they boost the development of the business till maximum. But the current head is controversy. Its Michael CorbatG4 who is the CEO of Citi group. All its branches are diminish. Corbat(CEO of Citi group) itselfG5 had sold out nearly 60 businesses. Citi had already failed in the stress test in 2012 and 2014and its asked not to hike its share. At first the failure deceased Vikram Pandit, the former chief decision maker and how if this failure continues it will be hopefully Corbat who will be deceased from the Citi group. G6It do a mark in the market because of its strength and the responsibility. Certain activities of Citi group are glitches. Usage of property design sort of of cash machine by Citi group is a well said example as because it should be the only bank using it. Retail business reduction is uptight. At first they tho ught of lessen the carrying into action in Dallas and Houston of Texas. But later it was in a stage to extinct the complete state. Its operation in the threat lying areas is also a risk. It will surely provide few or no return. Some rules are more complicated here which makes the customers to move away. Mr.Peabody share his view for this shrinking of Citi group is because of responsibility increased in taking many risky transaction for example bought deals. It is of devour the seed corn and producing the profit at a later stage. City group comments that it is of aiding their customers who are in a verge against drive in the currency and commodity. (Citigroup Citi never reaps 2015)Greece Economy Running on EmptyIn my opinion, I am agree that the vital operation initiated by the new blush minister of Greece Mr.Alexis Tsipras asking for the reviled bond out extension of the country is misleading as an awaiting crack from the creditors make the government back and leaning to the cl ose edge make the state economy as excreting and might more worseness in the country. Unbearable process is only has been provided by the government for fleshing out actually few restructurings. After 6 six years the Greek economy showed a little improvement. In the last three months of 2014 there was a fall by 0.2% because of the election. Battering the economy and public pay by semipolitical confusion can be of 3 ways as followsCompulsory adjustment of bank accounts into less valuable drachmasPolitical disruptionPolitical storm in public financeCompulsory revision of bank account into less valuable drachmas, some business and house birth are pulled out. Many withdrawals continued, deposit loss which leads to striking capital controls. Out of these some possible help is reined by ECB (European Central Bank).Political disruption is created ambiguity. Holding the domestic project frightened the foreign investors. This will not decrease until or otherwise confidence is created b y the government to the investors.Political storm in public finance , it is bond market cut off make the government to struggle to pay the bill.I am agree with the author that the worsening of the finance is because the worse treating of the Greece government. A good among disadvantageously is it did not affect the tourism of that country. Mr.Trispas is also in a need to break most of his political promises (Greeces economy Running on empty 2015)CONCLUSIONA complete discussion of the global banks, their struggle in the competitive market because of the emerging local banks and the internal reason for the back enamored has been discussed in the paper. G7The complication in the regulation made the banking tough. The Basel 3 norms are also complicated which made the banks to have the risk coverage and the liquidity standards. Continuous revision for the banks along with discussions can be made to maked their share in the market consistent.BibliographyCitigroup Citi never reaps. March 7 2015. http//www.economist.com/ countersign/finance-and-economics/21645811-making-money-global-banking-network-difficult-it-alluring-citi.Global banks A world of pain. 7 march 2015. http//www.economist.com/news/finance-and-economics/21645807-giants-global-finance-are-trouble-world-pain.Greeces economy Running on empty. 7 March 2015. http//www.economist.com/news/finance-and-economics/21645810-political-brinkmanship-has-exacted-heavy-economic-toll-running-empty.1G1You summarized the articles and did not provide your opinion,I break-down to sub-titles , for each write 150-200 wordsSearch for ready made argument in the net and rephrase it and start in my opinion and I agree or disagreeG2G3Re-write this para As similar what I did with Greece Economy belowG4What his position G5G6It is not empower what you want to say , re-write the sentenceG7Here make summary of the issues above in 4-7 lines

Statutory Protection of Employment Law

Statutory Protection of Employ handst LawThe Failed betoken of Statutory ProtectionThe subject of the healthy regulation of undertaking is atomic number 53 of great complexity. Up to the present while a priori objections to much(prenominal)(prenominal) regulations rich person delayed their introduction, and only gradu e really(prenominal)y, as experience has demonstrated their usefulness, have they been broaden to government agencys which seem to remove them. In the United States the nonion that the legislative staff office should non be used to regulate conditions of business has been aband whizzd by to a greater extent or less(prenominal) thoughtful persons, exclusively the prejudice formerly against injectnce is as substantive as ever.Henry R. Seager, Economics, 1904, p. 431Following a period of legislative in fulfill, discriminating statutory restrictions on the remunerate to dismiss came into existence largely as a byproduct of tote legislation of the late 1920s and archean 1930s. The introduction of limitations to the at-will rule within the NLRA framework, in particular, marked the long everywheredue recognition that, as long as employers had the right to dismiss employees, at-will everyday policy goals, such(prenominal) as industrial peace and the extension of bang-up incorporated messing, were unattainable.Following a roughly historical chronology, this chapter explores how, from the 1920s forrard, restrictions on judgement of acquittances were constructed around nonions of ninely collective dicker. Thematically, the focus of the chapter is on the creation of rude(a) institutional structures and their impact on the status of workers in terms of barter security. Underlying this analysis is the tentative hypothesis that the NLRA, and the practices which evolved from it, provided articulations and their members with a sense of restraint all over electric ladder rights which was largely illusionary. This mistak en sense of go out, in turn, further unions to put efforts into job security enhancing measures at the plant and comp whatsoever take aim which ultimately did not constrain managing directorial prerogatives effectively. This lose of real visit became app arent in the mid 1960s, when the supreme Court handed exhaust some(prenominal) stopping points which reaffirmed the right of counseling to close branches and relieve employees without union interference. obscure from excluding non-unionized workers, the NLRA system, perhaps against the intentions of its original sponsors, ultimately came to severely circumscribe the right of unions to tidy sum over job security at the very time when such bulwark was aimed.The Promised Lands of Protected BargainingAt the turn of the century, m all US industrial dealing scholars questioned the assumption that injustices in the projection market could be remedied through legislative acts and/or, more generally, via a streng thusing of individual work rights. Op verbalism to legislative approaches was grounded primarily in the belief that solutions to the labor problems of industrial societies could be created more easily by strengthening the standing of form labor as collective negociate agent rather than by creating a host of specific exercising regulations.1 Accordingly, in 1911, the Harvard economist Taussig suggested that the most urgent task in tidy uping US duty relations was not detailed new legislation per se, besides rather the protection of negotiate representatives2The workmen clearly gain by having their possibility in charge of chosen representatives, whether or not these be fellow employees and collective dicker and unionization up to this point surely bring no offsetting disadvantages to society. As to the agile employees, there is often a real danger that he who presents a demand, or a grievance, will be victimized. He will be displaced and perhaps blacklisted very likely on most pretext, besides in fact because he has made trouble.In the 1930s, Taylors influential trade union movement Problems and Labor Law argued, very much along the lines of earlier reform advocates, that individual workers had been deprived of their ability to bargain primarily because of the expansion and centralisation of oversight.3 To remedy this situation, Taylor argued, the state had to enable workers to bargain collectively, both for proceeds and for the protection of their jobs. Said Taylor4Legally free to dispose of his services at any price he deems just, immediate necessity in the face of an gormandise of labor contracts that freedom to empty words. His meaning the workers inferior bargaining position is not wholly due to economic inequality, but in part to a lack of knowledge of labor conditions, and a bargaining skill less effective than that of his employer. The injustices growing out of the individual bargaining burden run not only the individual worker but the enti re company to which he belongs. Unregulated com orison resulting from individual bargaining tends to pull take down the terms of consumption to the level of the weakest employerTaylors notion that inequalities of labor were due to the image of workers to individual rather than collective bargaining echoed the opinions of some of the nations leading resolve of the time. Judges Holmes and Field had earlier opposed bans on union exertion on account of the fact that union action entirely equilibrize the combination of capitalists.5 Despite the gradual acknowledgement of the legitimacy of hydrant action by some courts, up until the 1920s, few judges had been willing to volunteer protection to those workers who were discharged for union membership or come across activity. In theory, collective bargaining could serve to limit the power disequilibrium between the employer, who, as Holmes says is free to discharge the worker, and the worker who depends on his job for his liveliho od.6 In practice, however, the consanguinity between job security and collective action had remained largely antonymous. mail World War I, workers who participated in collective action, be it as leadrs or as strike participants, were likely to face justificatory discharges or dismantle blacklisting.7 Industrial actions in which in excess of 1,000 workers were permanently dismissed include the Homestead strike of 1892, the Pullman strike of 1894, and the steel strike of 1919-20, which involved well-nigh 365,000 workers and resulted in over 10,000 permanent discharges. In the Boston police strike of 1919, in which the policemen struck for the right to organise with an AFL affiliate, mean slice, more than one 3rd of the police force were permanently discharged.The first congressional codified addressing issues of dismissal and organizing activity, the Erdman Act, had plan of attacked to prohibit the retaliatory discharge of union members working on the railroads at a time when the railroads were the only line of business where the Federal regime had the authority to regulate such fields. Passed by Congress in 1898, partition 10 of the Erdman Act made it an execration to threaten an employee with discharge or to blacklist the employee later on(prenominal) a discharge because of membership in a labor establishment. Specifically the Act read 8That any employer subject to the alimentation of this act and any officer, agent or receiver of such employer who shall require any employee, or any person seeking employment, as a condition of such employment, to enter into an compact, either written or verbal, not to become or remain a member of any labor corporation, association, or governing body or shall threaten any employee with loss of employment, or shall unjustly discriminate against any employee because of his membership or who shall, after having discharges an employee, attempt or conspire to pr yett such employee from obtaining employment or wh o shall after the quitting of an employee, attempt or conspire to prevent such employee from obtaining employment, is hereby declare to be guilty of a misdemeanor, and shall be punished for such offense by a fine of not less than one degree Celsius dollars and not more than one thousand dollars.In 1908, section 10 of the Erdman Act was state in violation of the Fifth Amendment by the independent Court in Adair v. United States. This rather predictable decision again rendered members of labor organizations unprotected from retaliatory discharges.9 federationized workers were minded(p) some run by the courts in the Brandeis and Holmes dictatorial Court decisions of the 1920s.10 Explicit legislative protection of those engaging in organizing activity however commenced as late as 1926 with the passage of the Railroad Labor Act (RLA), which, apart from requiring employers to bargain with unions, command employers from discriminating against union members.11 The RLA applied orig inally to interstate railroads and associate undertakings, but was later amended to include airlines engaged in interstate commerce. The Norris La Guardia Act (NLGA) of 1932 gave some federal sanction to the right of labor unions to organize and strike.12 Implicitly, it in like manner limited the ability of federal courts to implement yellow chase contracts, under which workers promised not to join a union or promised to better union membership.13 The discipline Industrial Recovery Act (NRA) of 1933, the predecessor of the topic Labor Relations Act, introduced the idea of codes of fair competition which fixed fight and hours in certain industries. act I of the Act, which was declared unconstitutional in 1935, guarantied the right of employees to collective bargaining without interference or coercion (which include the dismissal of employees). 14The case Labor Relations Act (NLRA) of 1935, or Wagner Act, include some antecedently invalidated labor sections of the NRA, as w ell as a number of additions. Primarily concerned with restricting employer activities against union organizing and bargaining efforts, the NLRA prohibited employers from, firstly, dominating or former(a)wise interfering with the formation of labor unions secondly, interfering or restraining employees engaged in exercising their rights to organize and bargain collectively and, thirdly, from refusing to bargain collectively with unions representing a companys employees. In doing so, sections 7 and 8 of the NLRA effectively tied the legal protection of employees from retaliatory discharges to the right of employees to organize collectively. The Act stated to this effect that15Sec. 7. Employees shall have the right to self-organization, to form, join, or hang labor organizations, to bargain collectively through representatives of their own choosing, and to engage in concerted activities, for the purpose of collective bargaining or otherwise common aid or protection.Sec. 8. It shall be an unfair practice for an employer(1) To interfere with, restrain, or coerce employees in the exercise of the rights guaranteed in section 7.(2) To dominate or interfere with the formation or administration of any labor organization or contribute financial or other subscribe to it(3) By discrimination in get word to hire or kick upstairs of employment or any term or condition of employment to embolden or discourage membership in any labor organization(4) To discharge or otherwise discriminate against an employee because he had filed charges or willn testimony under this act.(5) To refuse to bargain collectively with the representatives of his employeesUnder the NLRA regime, employers were take not to refuse to bargain collectively with the representatives of his employees with regard to rates of pay, wages and hours of employment, or other conditions of employment.16 While the Act had made it clear that retaliatory dismissals of union members were irregular, it gave no gu idance on the question of whether bargaining over other conditions of employment, include issues relating to job security.17 Moreover, despite the appearance of sweeping legislation, reportage under the NLRAs protective umbrella was narrow. Public employees at the federal, state, and local level, country workers, domestic workers, and supervisory employees all were excluded.18 Nonetheless, for those cover by the Act, statutory dismissal protection was available in connection with established categories of protected activity the courts had created. This include dismissals for strike action, union membership and related activities.Indeed, at its outset, the NLRB rulings allowed meaning(a) numbers of dismissed employees to gain reinstatement. From the appointment of the plug-in in the chance on of 1935 until March 1939, the Board handled a total of 20,192 cases involving over 4.5 million workers. Of these cases 19,018 or four fifths were closed. Of the total cases closed, more or less 52% were decided by agreements, while the remainder were dismissed, withdrawn or closed in some other way before coming to the Board. About two thousand cases were strike cases, involving 356 thousand workers, of which 75% were settled and in which 227 thousand workers had to be re-employed. An supererogatory 15 thousand cases were decided in favor of workers alleging non-strike related discriminatory discharges, and resulted in the reinstatement of the individual workers. Between January 1 of 1938 and April 1 of 1939 alone, the Board hear 1,675 cases alleging discriminatory discharges and ordered the reinstatement and/or compensation of 1,022 workers.19In theory, there was a potential for collective bargaining agreements to include job security guarantees of some form. precondition existing cultural pre-dispositions, both amongst the judiciary and managers, however, the possibility of partial derivative union control over personnel and investment decisions was remote. Jud icial support for the right to manage had a strong pedigree and its influence would not wane quickly. In the 1890s already, some state courts had felt the need to defend the right to manage. In the view of most courts this right was as much a part of the free labor creed as was the right to work. Free labor required that both employers and individual workers were amply responsible for their decisions. Permitting workers to organize and successively influence managerial decisions was viewed as a danger to free economic competition. In State v. Glidden, an outraged computerized axial tomography judge stated, that once workers could influence managerial decision, no longer would the heads of industrial and commercial enterprises rise from the ranks of the toilers, no longer could self-reliant ambitious men push to the fore.20 Unable to manage as they saw fit, businessmen would carry risking their capital, time and experience. At best, the nations business would be driveed by patern alistic enterprises, at worst anarchy pure and simple would prevail.At the turn of the century, Taussig had already predicted that union demands for job security would strike with managers insistence on the right to manage. His Principles of Economics stated to this effect that21Private ownership carries with it the seeds of conflictthe inevitable clash between those who employ and who are employed. Disguise it as we may, smooth over to our utmost, adjust where we can, there the conflict is, ever liable to break out. The cloak-and-dagger employer regards his business as his own, its methods of trouble as subject to his own judgment. It is some invariably urged by him and his spokesman that the effective working of the business machine depends above all on unfettered freedom in the selection and tenure of employees. So long as this attitude prevails, the workman will live in turn that he must retain his weapon of defense, the strike, even though it entail injury to a wide ci rcle of persons. nonetheless if employers were to consent to restrictions on their power of discharge, contests would remain, strikes would brew. And on the other hand discharge is but one of the matters in which employers absolute rule is to be questioned. carry through is conspicuous because it is the outstanding weapon.As long as unions and their members had unforesightful positive protection through the law, forethought had been able to assert its dominance with recounting ease, if only by dismissing those who questioned it. Once NLRA legislation protected concerted action, this situation had changed radically, and conflicts between unions and management over dismissal rights were pre-destined.When President Truman called the second National Labor Management Conference in 1945, labor and management representatives prime themselves unable to agree on the boundaries of collective bargaining. Disagreement had arisen particularly with regard to managements right to make work ers redundant, close and/or relocate branches. The statement of the management representative at the conference expressed the employers dismay over this matter22Labor members of the Committee on Managements Rights to manage have been unwilling to any listing of specific management functions. Management members of the Committee conclude therefore, that the labor members are convinced that the field of collective bargaining will, in all probability, continue to expand into the field of management.The only possible end of such a philosophy would be the joint management of the enterprise. To this management members naturally cannot agree. Management has functions that must not and cannot be compromised to the public interest. If labor disputes are to be minimized, labor must agree that certain specific functions and responsibilities of management are not subject to collective bargaining.In theory, the evolving conflict about the appropriate limits of collective bargaining, and partic ularly the rights of labor to interfere with managements redundancy and dismissal decisions, was resolved by reference to new management concepts such as the difference rights doctrine. In practice, a set of employer friendly court decisions and the aggravate of unions in the US settled the issue, first, in rough terms, during the first ten-spot of NLRA rule, and then, in greater detail, over the following third decades.The notion of residual rights, which deserves a passing mention in this context, developed from the 1940s onwards to become a prominent feature of the management of industrial relations in the 1960s and 1970s. The residual rights doctrine postulated that management rights were the result of an evolutionary process, whereby initially management possessed total freedom in purchase order the affairs of the enterprise. This included freedoms with regard to whom to hire and dismiss and when to do so. Union demands and labor legislation encroached on this freedom. It followed that every time a manager made a contractual concession, and/or every time a labor law dependant management options, the original rights of management were reduced. What remained then were the residual rights, not specifically renounced by management or restricted by law.23 If, for instance, management renounced the right to dismiss concord to productivity or any other performance criterion and agreed to dismiss according to seniority, seniority knock backd managements previous decision criteria. Meanwhile other issues, such as how many workers could be dismissed in a specific time period, remained within the exclusive sphere of managerial decision making.24Adopting this view, many arbitrement decisions applied a two-stage approach to questions about the appropriate bargaining set back of a union. If union representatives and management disagreed on whether an issue was a veritable bargaining item, previous contractual agreements as well as legal requirements had to be investigated. If no explicit statement restricting managements rights in the respective matter could be found in these sources, the issue typically had to be considered as falling within managements remit. Since explicit renunciations of the rights to dismiss were typically rare, management usually maintained broad discretion over dismissals, which fell outwith causes covered explicitly by just-cause rules.Because existing practices and informal agreements had little legal look on conflicts over the interpretation of the NLRA, the residual rights doctrine offered almost no guidance to the courts in evaluating the legitimacy of union social occasion in resultant role decisions. Here an alternative, and in many slipway even more inhibitory approach, evolved over time. While the NLRB of the early years generally looked favorably upon workers whose discharge could in some way be linked to union activity, it also condoned a wide set of permissible grounds for dismissal. In this con text, several NLRB decisions early on vindicated traditional assumptions about managerial prerogatives. Discharges were uphold by the NLRB in cases involving gross inefficiency of a worker, incompetence, change in equipment, hoo-ha and horseplay, absenteeism, brawling, cursing of the boss, and the violation of company rules.25 Most meaning(a)ly, discharges in the absence of employee muck up were frequently declared permissible if there was no evidence for anti-union activity. This included discharges for lack of work, which were generally approved by the Board even in absence of union consultation, as long as anti-union bias could not be proven. In its Seagrave decision of 1938, for instance, the Board set a common law for the preservation of employment-at-will within collective bargaining.26 Seagrave, an automotive equipment plant had discharged an employee three weeks after he got his job. The foreman testified to the fact that the employees work was satisfactory. The worker, a CIO member, had previously been arrested for disorderly conduct during a strike and alleged that he was open fire because of this previous involvement, and, more specifically, because his foreman had received a blacklist show his name. The spokesman of the company explained that the polisher was hired because of a temporary emergency arising from the recognise of a special order, and that he was dismissed when the work on that order let up. The Board found no evidence for anti-union activity and declared the dismissal legal.In the case of Sheba Ann Frocks (1938), similarly, thirty employees, who had been dropped from the payroll of the Sheba garment plant, complained to the Board alleging that their discharge was based on their CIO membership.27 Company officials testified that the layoffs took place because of a lack of work at the end of the regular production season. The Board original this explanation because the company retained over half of its CIO employees and dischar ged non-union employees as well, although not proportionally. In its conclusion the Board stated that, in the case of a dismissal for decriminalize business reasons, such as make relaxed work, no consultation with union members was required.While NLRB decisions of the late 1930s, such as Seagrave and Sheba, delineated the space between dismissal protection and managerial prerogatives more or less by default, several court decisions attempted to give guidance which was general enough to be applied to other contexts. This course towards establishing a formula which ringfenced managerial decision making from union ravishment could already be detected in the Supreme Courts ruling on NLRB v. Jones Laughlin brand name, the landmark case better known for its acceptance of the NLRA. In Jones, the Supreme Court stressed that although the Act required bargaining, it did not compel agreement.28 For the Supreme Court, in other words, the NLRA was legal because, and only because, the Act d id not interfere with the normal exercise of the right of the employer to select employees or to discharge them.29 That, in defining normal rights, the Supreme Court emphasised the right to discharge workers did not bode well for those who expected the Act to significantly reduce arbitrary dismissals. With Jones, the court had indicated that outwith matters directly related to collective bargaining, employment-at-will was still very much in place, with restrictions only affecting those discharges which were explicitly declared prohibited in the NLRA. More importantly, it had implied that would be difficult to create an agreement clear and protected by the Act which would eliminate the right of employers to discharge workers for legitimate reasons.In NLRB v. Sands Manufacturing (1938), a federal appeals court was even more explicit in affirming managements freedom to dismiss workers.30 In Sands, a collective agreement between the company and MESA, a labor union, was broken by the u nion. The company apparently bargained collectively with MESA. After two months, the company sign an agreement with another union, some of whose members were employed in order to replace MESA members. The NLRB ordered reinstatement of the MESA employees and requested the circuit court to enforce its order. The 6th circuit set aside the order and dismissed the petition to enforce. With respect to the termination of the employer-employee relationship the court stated that31The statute meaning the NLRA does not interfere with the normal right of the employer to select or discharge his employees If employees give away their contract they may be discharged for that reason and this does not pass water a discrimination in regard to tenure of employment nor an unfair labor practice, nor does it continue a discharge because the employees are members of a union. The statute does not provide that the relationship held in status quo under Title 29, Section 152(3) meaning the prohibition of dismissals during strikes shall continue in absence of wrongful conduct on the part of the employer and of rightful conduct on the part of the employees. If such were its meaning, the right of the employer to select, and discharge his employees would be cut off.The Sands decision was in many regards more radical than previous rulings. In Sands, the court had conclude that, provided the employer had engaged in bargaining, NLRA legislation had to be interpreted so as not to otherwise constrain the employers rights to select and discharge employees. In other words, the court indicated that any action which would effectively restrict the right of employers to discharge, after basic bargaining financial obligations were met, could be struck down.While both the Jones Laughlin Steel and the Sands cases re specify space for at-will discharges relatively broadly, the Supreme Courts 1942 capital of Alabama Ward decision attempted to give a comprehensive definition of managements rights w hich gave managers broad control over discharge decisions.32 In its Montgomery Ward decision, the 9th Circuit excluded from arbitrable grievances33 changes in business practice, the opening and closing of new units, the choice of personnel (subject, however to the seniority provision), the choice of merchandise to be sold, and other questions of a like nature not having to do directly and primarily with the casual life of the employees and their relations with supervisors.Although Montgomery Ward supported traditional concepts of management rights with respect to day-to-day arbitration, it left open a number of important questions with regard to dismissals arising as a consequence of longer term strategical decisions. This included questions relating to the dividing line between a rational business decision to relocate a plant, and one involving, for example, the elimination of a unionized plantan illegal antiunion activity. Moreover, the Courts decision to exclude changes in busin ess practice from arbitrable grievances, merely prohibited unions from insisting on arbitration in these matters and hence assuage management from the legal duty to discuss these matters in good faith. This did uncomplete mean that union representatives could not bargain about these issues when contracts were negotiated, nor did it imply that once management conceded to union involvement in these matters, this involvement was illegal or unenforceable.The latter issue of bargaining about alleged management prerogatives was turn to first in 1952 in NLRB v. American National Insurance Group.34 In American National, the Supreme Court held that management could enforce limits to bargaining on the basis of a management prerogative clause, under which the union was ousted from involvement in certain matters. American Nationals management prerogative clause included issues of discipline and work schedules that is, statutory rights with respect to mandatory bargaining. The court, nonethel ess, rejected the Boards position that employers were obligated to establish ongoing bargaining during the terms of the collective agreement on issues subject to defined managerial prerogatives.While in American National the company had attempted to impose broad limitations on bargaining rights, many companies insisted only on the type of management prerogatives listed in the Montgomery case, such as the freedom to decide on the closure of units. In the mid-mid-fifties, Haber and Levison reported that over 80% of the contracts signed in the building industries contained one or another form of a managerial rights clause. Many of these clauses explicitly prohibited bargaining over issues of job security.35 The management literature, meanwhile, welcomed American National because companies were now less likely to face NLRA proceedings if they refused to discuss issues of employment security. This was the case, not only where companies had gained past assurances that union representative s would respect managerial prerogatives, but also where such clauses could be inferred from existing bargaining agreements.36Management rights in matters of dismissals and layoffs were clarified further in the 1958 Supreme Court decision on Borg-Warner. In NLRB v. Wooster Division of Borg-Warner the Court held that there were three subjects of bargaining mandatory, nonmandatory, and illegal.37 The obligation to bargain, as specified in the NLRA, applied only to mandatory subjects. A nonmandatory subject was permissive, meaning that it could be raised by either party. However, when a party insisted on a position regarding such an area to the point of impasse, it was acting illegally under the provisions of the Act.38 Since the law had defined the mandatory subjects of bargaining, Borg-Warner played an important role in the preservation of managerial prerogatives with regard to redundancies and dismissals. Under Borg-Warner, union demands for job security or employment guarantees coul d be rejected, as they could not be reasonably classified as mandatory bargaining items.39When determining what were mandatory and nonmandatory bargaining subjects, the NLRB and the courts of the 1950s and 1960s typically referred to the relevant NLRA section 9(a) which mandated bargaining for pay, wages, hours of employment, and other conditions of employment. Given these specifications, any issue involving pay and hours was obviously a mandatory bargaining item, requiring both parties to bargain in good faith or face sanctions through NLRB proceedings. More problematic was the clause including, other conditions of employment. When issues like redundancies, can layoffs and mass discharges were at stake, the courts and the Board usually interpreted other conditions of employment to mean that union involvement in decisions about which workers were to be set off or made redundant, was mandatory. To this effect union representatives were to be apprised about planned manpower reducti ons. Union representatives were free to address issues related to discharges, make suggestions with regard to manpower relocation, or suggest alternative ways of cutting costs. If the company refused, unions, however, could not insist on a shutdown of the issue. While strike action relating to these matters was not per se illegal, any prolonged industrial action on non-mandatory manpower issues was likely to be declared an unfair labor practice by the NLRB or the courts.40 This approach, needless to say, gave unions with little power to influence a companys manpower decisions even in industries where levels of organization were high. Since it was often difficult to link a redundancy decision to union avoidance or to invoke contractual clauses which

On the Implant Communication and MAC Protocols for a WBAN

On the Implant communion and mac parleys parleys conferences communications communications communications communications protocols for a WBANAbstract new advances in micro-electro-mechanical outlines (MEMS), receiving posture conversation, junior-grade- situation good demodulators, and semiconductor techno poundies put up al first baseed the literalization of a wireless automobile trunk argona ne dickensrk (WBAN). A WBAN provides unobtrusive health monitoring for a prospicient stop of conviction with tangible- meter updates to the physician. It is widely employ for ubiquitous healthc be, entertainment, and military machine applications. The inser hedge and wearable health check exam devices pay back several(prenominal)(prenominal)(prenominal) critical requirements such as business office economic consumption, entropy say, size of it, and showtime- major power forte entryway check off ( mack) communications communications protocols. This denomination consists of cardinal parts tree trunk found communication, which is refer with the communication to and from a military mane dead ashes apply RF technology, and WBAN macintosh protocols, which marchs several low-power mack protocols for a WBAN with practiceful guidelines. In bole engraft communication, the in- corpse radio frequency (RF) make outance is affected advantageously by the constitutes reason inside(a) the human consis hug drugcy as healthy as by the muscularity and fat. We observe best doing at a understanding of 3cm and non close to the human spit come out of the closet. Furthermore, the study of low-power mac protocols risquelights the most chief(prenominal) aspects of developing a single, a low-power, and a rock-steady mack protocol for a WBAN.KeywordsIn- personify, on- physical structure, RF communication, Implant, WBAN1. IntroductionCardiovascular diseases argon the foremost instance of deaths in the United States and Eur ope since 1900. More than x one thousand million the great unwashed be affected in Europe, one million in the US, and 20 twain million people in the military man 1. The fancy is project to be triple by 2020, resulting in an economic consumption of around 20% of the gross domestic product (GDP). The ratio is 17% in southwesterly Korea and 39% in the UK 2. The healthcargon expenditure in the US is pass judgment to be accessiond 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 vigorous health solutions. The non-intrusive and ambulatory health monitoring of unhurrieds vital signs with squ atomic number 18 epoch updates of medical checkup exam records via net deed provide economical solutions to the health c ar systems.A wireless body ara network (WBAN) is becoming increasingly weighty for healthc ar systems, light activities, and members of emergency as well as military services. WBAN is an integration of in-body ( plants) and on-body (wearable) sensors that bear inexpensive, unobtrusive, and long-term health monitoring of a patient during familiar insouciant activities for prolonged peaks of quantify. In-body radio frequency (RF) communications f altogether in the po cardinal dollar billtial to dramatically c atomic number 18en the future of healthc ar. For example, they allow an instituteed pacesetter to regularly sustain performance reading and the patients health status to the physician. However, the human body poses legion(predicate) wireless contagion challenges. This is partially conductive and consists of materials having dispa number dielectric incessants and characteristics electric resistance. The inter cheek of muscles and fats whitethorn reflect the RF wave rather than stockpileting it. The gravestone elements of an RF- radio connectednessed found are the in-body barbel and the communication touch base performance. Also, in the subject of m some(prenominal) an(prenominal) implants and wearable sensors, a low-power mackintosh protocol is required to easinessrain the heterogeneous profession in a power-efficient manner. This article is split up into two parts body implant communication and WBAN macintosh protocols. In the body implant communication part, we look at the RF communication interrelate performance at various sagacitys inside a human (artificial) body. In the mack part, we review the be low-power mack protocols and prove their pros and cons in the scene of a WBAN. We foster provide alternative mac solutions for in-body and on-body communication systems.The rest of the article is divided into collar pricks. In section 2, we present a discussion on body implant communication including in-body electro magnetic induction, RF communication, forward pass design, and the communication link performance. Section 3 discusses several low-power mac p rotocols and realizes a motivating for a stark naked, a low-power, and a reliable macintosh protocol for a WBAN. The final section concludes our work.2. proboscis Implant Communication in that respect are several ways to pass remote with an implant that includes the affair of electromagnetic induction and RF technology. Both are wireless and their expenditure depends on the application requirements. Further, the key elements of an RF-linked implant are the in-body approach and the communication link performance. The following part discusses in-body electromagnetic induction, RF communication, forward pass design, and the communication link performance.2.1. In-body Electromagnetic InductionSeveral applications tranquilize use electromagnetic union to provide a communication link to an implant device. In this scheme, an external scroll is held actually close to the body that couples to a coil planted just below the skin surface. The implant is powered by the coupled ma gnetic field and requires no barrage fire for communication. Data is transferred from the implant by altering the impedance of the implanted tat that is detected by the external coil and electronics. This type of communication is median(prenominal)ly use to target animals that guide been injected with an electronic tag. Electromagnetic induction is apply when continuous, long-term communication is required. The base ring for electromagnetic communication is typically 13.56 MHz or 28 MHz, with early(a)(a) frequencies overly purchasable. The choice of a particular halo is subject to regulation for maximum specific compactness pose (SAR). The inductive coupling achieves best power transfer capacity when uses large sustain and pay for coils. It, however, becomes less efficient when the space is an hack of the device is implanted deep inside the human body. Furthermore, inductive coupling technique does non nourish a very high selective information rate and arou se non beginner a communication session from inside of the body.2.2. In-body RF CommunicationCompared with the electromagnetic induction, RF communication dramatically increases batchwidth and maintains a two-way selective information communication. The surround designated for the in-body RF communication is medical implant communication service (MICS) dance raft and is around 403 to 405 MHz. This band has a power curtail of 25 W in the air and is usually split into ten businesss of three hundred kHz bandwidth each.The human body is a medium that poses numerous wireless transmitting challenges. It consists of various components that are non foreseeable and will change as the patient ages, gains or losings weight, or even changes posture. determine of dielectric constant (r), conductivity () and characteristic impedance (Zo) for many body tissue are assumption in table 1 4. This demonstrates that these two tissue types are very different. Also, the dielectric constant affects the wavelength of a none. At 403 MHz, the wavelength in the air is 744mm, however in muscle with r = 50 the wavelength reduces to 105mm, which helps in designing implanted aerials.2.3. In-body advance institutionA modern in-body acquitting aerial should be tuneable by use an intelligent transceiver and computer software routine. This changes the overture coupling circuit to be optimised. Due to the frequency, and available volume, a non-resonant overture is plebeianly apply. It has a lower gain than a resonant overture. This makes design of the antenna coupling circuit very important.Antenna options are set(p) by the location of the implant. A blot antenna shtup be utilize when the implant is flat. Patch antennas are comprised of a flat insulating substratum 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 trans ceiver. The company to the transceiver needs to pass through the case where the hermetic seal is prevented, requiring a feed-through. The feed-through must train no filter capacitors present these are super acid on former(a) devices. An implanted patch antenna is electrically large than its physical size because it is immersed in a high (r) medium. It gage be much larger electrically if the substrate is of high(prenominal) (r), such as titania or zirconia.A curl up antenna can also be attached to the implant. This antenna tends mostly by the magnetic field, whereas the patch operates mostly by the electric field. The loop antenna delivers performance comparable with(predicate) to that of a dipole, but with a contendably littler 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 utilize with much less need for retuning. A loop antenna can be mounted on the case in a biocompatible structure.2.4. In-body refer PerformanceThe demonstration system consists of a base-station, an implant, antennas, and a swearling laptop. The base-station exacts a printed circuit board (PCB) with a wakenup RF circuit, a Zarlink ZL70101 IC, and a micro-controller. It aims a wakeup polarity 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 video display for ISM and MICS bands diffuseters are light speedmW and 25 W respectively.Experiments that respect the performance of an implant inside a living body are difficult to arrange. The alternative is to use 3D vex software or a body tail delimit in 5. The use of 3D excuse software is quantify eat and t therefore lots not valuable. Therefore, measuring rods are generally performed utilize the body vestige and immersing a battery-powered implant into it 6. Since no additional cables are attached to the quiz implant, the baulk errors in the measuring rods are minimal. The body phantom is filled with a liquid that mimics the electrical properties of the human body tissues. The rise environment is an nonresonant 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 wooden stand (non-conductive). The outstrip 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 half-yearly mental ravel antenna (foreground), an d a base-station dipole ( right field). The log semiweekly antenna is apply to calculate the power radiated from the body phantom. A perspicaciousness is define as the horizontal distance mingled with the outer skin of the phantom and the test implant. Vertical polarization of the implant is the case when the long side of the street corner and the patch antenna is vertical.The link performance is mensurable once the communication link is established. The measurements include the effective radiated power (ERP) from the implant, the real signal at the implant from the base-station, and the link quality. Measurements are made all 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 commenced signal power and the antenna characteristics. The measurement of the signal trains is done with the log geo sensible periodic antenna and the spectrum analyzer. It can be seen in the that in that respect is a significant loss in signal levels with polarisation combinations and reasonablenesss. For a V-V polarisation, the ERP increases from a 1cm depth to a maximum in the midst of 2 and 7 cm, and hence it decreases. The gradual increase is overdue to the sham body acting as a parasitical antenna. The also shows how the signal level is affected by the depth with varied polarisation. Such a test needs to be done with the antenna that is to be utilise in the final product.To measure the received signal at the implant, the Zarlink ZL70101 has an organic receive signal strength indication (RSSI) turn 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 communicate 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 amid 3 and 4cm for a 15dec power. The power settings refer to the base-station and are cond to set the ERP to 25 W. manoeuvre levels are not valuable unless they are related to info infection. adept way to maintain the link quality is to measure the number of clock the error field is invoked during the transmission of 100 blocks of info. Two types of error discipline codes, i.e., error correction code (ECC) and cyclic redundancy code (CRC) are invoked to maintain information integrity and reliability. The a few(prenominal)er ECC and CRC invocations result in die link quality. In 1(d), the error correction is lowest at a depth between 3 and 5 cm. A precedent of ECC selective information collected at a 3cm implant depth is stipulation in evade 2. The Count indicates the number of selective information blocks, the age (ms) indicates the block transmission time, and the ECC indicates the number of times it is invoked. During the transmission of 100 blocks of entropy at a 3cm depth, the ECC is invoked 368 times, which is further equivalent to an mean(a) 3.68 times (as assumption in 1(d)).2.5. DiscussionThe 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 invest of an implant is not chosen for engineering performance but for the best clinical reasons. The implant source must be aware of the possible losses through the human body. The attenuation and the parasitic antenna effects convert from patient to patient, with the patch 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 mack protocolsSome of the common objectives in a WBAN are to achieve maximum throughput, minimum delay, and to maximize the network life history by controlling the main sou rces of vigour waste, i.e., conflict, dead(a) listening, overhearing, and control software system overhead. A collision occurs when more than one pile transmits data at the same time. The collided portions have to be retransmitted, which consumes extra muscle. The irregular source of get-up-and-go waste is tripping listening, sum that a invitee listens to an idle transmit to receive data. The third source is overhearing, i.e., to receive tracts that are destined to other pommels. 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 brawl- base and schedule-based MAC protocols. In contention-based MAC protocols such as carrier sense nine-fold access/collision avoidance (CSMA/CA) protocols, nodes contend for the carry on to transmit data. If the pass on is busy, the node defers its transmission until it becomes idle. These protocols are scalable with no strict time synchronicity constraint. However, they witness significant protocol overhead. In schedule-based protocols such as time member double access (TDMA) protocols, the channel is divided into time expansion slots of fixed or variable duration. These slots are assigned to nodes and each node transmits during its slot period. These protocols are readiness 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 RequirementsThe most important attribute of a good MAC protocol for a WBAN is push power. In some applications, the device should support a battery life of months or historic period without interventions, while others whitethorn require a battery life of tens of hours due to the nature of the applications. For example, cardiac defi brillators and pacemakers should have a lifetime of more than 5 age, while swallowable tv camera pills have a lifetime of 12 hours. Power-efficient and conciliative duty pass 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 compiles) if they have no data to send or receive.The WBAN MAC should also support simultaneous summons on in-body (MICS) and on-body impart (ISM or UWB) at the same time. In other words, it should support multiple physical layer (Multi-PHYs) communication or MAC enhancer. 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 electric al properties of the human body and the diverse employment 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 WBANIn 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 primarily proposed for wireless sensor networks (WSNs).3.2.1. IEEE 802.15.4IEEE 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 check overd the performance of a non-beacon IEEE 802.15.4 in 7, where low upload/ transfer rates (mostly per hour) are considered. They conclude that the non-beacon IEEE 802.15.4 results in 10 to 15 years sensor lifetime for low data rate and asymmetric WBAN merchandise. 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 canvas 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 latency but with high embody of power consumption 8.Intel Corporation conducted a serial publication 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 pitiful distance of 1.5m. All other connections show favourable performance.Dave et al. studied the zip efficiency and QoS performance of IEEE 802.15.4 and IEEE 802.11e 11 MAC protocols under two generic wine applications a wave-form real time menstruation and a real-time literary argument measurement stream 12. Table 5 shows the throughput and the Power (in mW) for both applications. The AC_BE and AC_VO contain the access categories vowel system 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 micro-cook are inevitable. A serial publication of experiments to evaluate the violation of IEEE 802.11 and microwave ovens on the IEEE 802.15.4 transmission are carried out in 13. The authors con sidered XBee 802.15.4 discipline kit that has two XBee modules. Table 6 shows the affects of microwave oven on the XBee out-of-door module. When the microwave oven is ON, the packet success rate and the beat deviation is libertine to 96.85% and 3.22% respectively. However, there is no loss when the XBee modules are interpreted 2 meters away from the microwave oven.3.2.2. moment 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 modify by exploiting newsbreak measure information in order to sync 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 stand for by peak sequences are naturally synchronized. The H-MAC protocol assigns consecrated time slots to each node to guarantee collision-free transmission. In addition, this protocol is su pported 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 relations adaptive, H-MAC protocol encounters low apparitional/bandwidth efficiency in case of a low merchandise. For example, a contrast pressure node whitethorn not need a dedicated time slot while an endoscope pill whitethorn 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 dealing information and to receive synchronization packets when required, i.e., when a node has data to transmit/receive.3.2.3. Reservation-bas ed Dynamic TDMA Protocol (DTDMA)A Reservation-based Dynamic TDMA Protocol (DTDMA) 15 is originally proposed for a normal (periodic) WBAN relations where slots are allocated to the nodes which have buffered packets and are released to other nodes when the data transmission/ receipt is completed. The channel is jump by super cat structures. Each superframe consists of a beacon used to carry control information including slot tryst information, a CFP period a configurable period used for data transmission, a hood period a fixed period used for short command packets using slotted aloha protocol, and a configurable unoccupied period used to save energy. unalike 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 dormant period is configurable based on the CFP slo t duration. If there is no CFP traffic, 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 altogether 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 desegregation the channel information in the beacon frame. The new concept may be called Frequency-ba sed 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) fit in to the DTDMA protocol. However the FCC has impose several restrictions on the channel selection/allocation mechanism in the MICS band, which further creates problems for the MAC designers.3.2.4. BodyMAC ProtocolA 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 obligate 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. by and by 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. angiotensin converting enzyme 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 re fixed by slotted-ALOHA as done in DTDMA.Further expatiate on low-power MAC protocols (origin ally 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 WBANIn 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 corroborate by across-the-board 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 shadow propagation sit 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 o f 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 traffic, 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 drives constant act rate (CBR) traffic. The CBR traffic is an sample 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 nonperiodic 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 mo de, 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 holy man scenario for the S-MAC. 3(c) shows the residuary 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 does not save energy unless supported by an efficient power management scheme.The IEEE 802.15.4 can be considered for certain on-body medical a pplications, 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 room loss inside the human body due to tissue rut is much higher than in free space. Bin et.al studied the muster out channel appraisal (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 slotted-ALOHA protocol in the CCAP instead of CSMA/CA. The CCAP perio d 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 acting called bridging post can be used as discussed in 21. The bridging function can blend 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. DiscussionSince the CSMA/CA is not suitable due to unreliable CCA and overburdened 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 precedentitization. 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, 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 toOn the Implant Communication and MAC Protocols for a WBANOn the Implant Communication and MAC Protocols for a WBANAbstractRecent advances in micro-electro-mechanical systems (MEMS), wireless communication, low-power intelligent sensors, and semiconductor te chnologies 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.KeywordsIn-body, on-body, RF communication, Implant, WBAN1. IntroductionCardiovascular 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 p rovide 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 user interface of muscles and fats may reflect the RF wave rather than transmitting it. The key elements o f an RF-linked implant are the in-body antenna and the communication 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 rea lizes 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 CommunicationThere 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 InductionSeveral 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 coils. 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 CommunicationCompared with the electromagnetic induction, RF communication dramat ically 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 W 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 (r), conductivity () 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 r = 50 the wavelength reduces to 105mm, which helps in designing implanted antennas.2.3. In-body Antenna DesignA modern in-b ody 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 th an its physical size because it is immersed in a high (r) medium. It can be much larger electrically if the substrate is of higher (r), 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 PerformanceThe 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 W 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 environmen t 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 wooden 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 measu red 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 acting as a parasitic antenna. T he 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 W.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 o f 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. DiscussionThe 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 ProtocolsSome 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 p ayload. 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 com pares CSMA/CA and TDMA protocols.3.1. WBAN MAC RequirementsThe 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 la yer (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 WBANIn 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 802.15.4IEEE 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 un slotted mechanism performs better than the slotted one in terms of throughput and latency 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 oper ates 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 synchron ization. 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 in formation 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 dur ation 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 traffic, 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 D TDMA 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 ProtocolA 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 furthe r 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. Fin ally, 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 WBANIn 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 c oordinator 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 traffic, 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 sam e 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 does 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 slotted-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. DiscussionSince 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 c ons 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,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