Wireless Network Engineering Digital and Analog

Question: Describe about the Wireless Network Engineering for Digital and Analog. Answer: 1: Comparison Between analog signals and digital signals: Particulars Analog signals Digital signals Signal It is a continuous signal which represent physical measurement It is a discrete signals which represent digital modulation Waves Sine waves representation Square waves representation Representation Continuous range of values Discontinuous range of values Technology Record waveforms Limited number of records Transmission of data Noise can occur deterioration in the completion of read and write cycle Noise can occur without deterioration in the completion of read and write cycle Response given to noise Reduce the accuracy Analog response are generated Flexible Implementation of hardware is not flexible Implementation of hardware is flexible Uses It is best suitable for analog devices It is suitable for devices of digital electronics Bandwidth It consumes less bandwidth It consumes more bandwidth Transmission of radio waves using antenna: The radio waves are usually used for the transmission of sounds and pictures. The modulated carrier wave is generated by the oscillator circuit transformer which is then applied to the antenna for converting the electrical signals to electromagnetic waves. This transmission takes place at the speed of light (Dan, 2008). The receiving antennas at receiver site receive the modulated signals in the electromagnetic wave and then transform it into electrical waves. 2: The multiplexing methods are described below: FDMA: FDMA stands for frequency division multiplexing access which makes use of fundamental technique of dividing bandwidth or single channel into multiple channels. Each individual channels have single spectra for the transmission of data. In the transmission of the data, the linear mixing of the subcarrier takes place. TDMA: TDMA stands for time division multiplexing access which is used for dividing the single channel into number of time slots or bands. Every time slot is capable of transmitting of one byte of data (Shacklett, 2012). The transmission of digital segment takes place in sequential order. This is the best method used for signals having slow voice data, compressed video, and the data which requires high speed transmission. The global system of mobile communication technology is based on the time division multiplexing access. CDMA: CDMA stands for code division multiplexing. It is based on the technique of digitization. It make use of direct sequence spread spectrum which can be accomplished by digitizing the analog signal and transmit it by using wider bandwidth. The chipping codes of 5MHz allow the multiple users to share the data at the same time having common bandwidth. The technology uses XOR circuit for chipping the signal at higher frequency. The XOR circuit is also used for sending digitized and compressed signals in serial order. CDMA employed the technique of Spread spectrum. Future Technology: CDMA is the dominant technology in the future of wireless technology because it sends the compressed voice at 3.84 Mbit / sec. The chipping codes of 5MHz allow the multiple users to share the data at the same time having common bandwidth. 3: The sensitivity of receiver and sender predicts the quality of wireless transmission. The quality of the transmitted signal can be improved by improving the sensitivity of the receiver. By improving the characteristics of antenna like frequency, impedance, ability of transmitting and receiving signals, polarization of the antenna, pattern of the antenna radiation, short distance reception should be used, and installation of the antenna should be simplified by dividing the receiving end. For the installation of the antenna, it is required to use minimum cable length and the connection point used between two antennae (Mohammed, 2014). The size of the antenna can depends on the factors like distance between the sites, the Fresnel zone, and objects placed in the path. Distance of Wireless Link Approximate value of Fresnel zone Approximate value of earth curvature Size of the antenna 1 2 3 4 3 23 4 27 5 30 5 35 8 40 8 48 10 44 13 57 15 55 23 83 20 65 50 115 25 72 78 150 4: ZigBee makes use of IEEE standard of 802.15.4specification for the implementation of physical layer and MAC layer. Star Topology: It is the combination of coordinator and end devices. The communication between the end devices and coordinator takes place by doing exchange of the data packets. Advantage: The nodes can easily be connected to one another Disadvantage: The operation of the topology depends on the working structure of the coordinator. No availability of alternative path Tree topology: In this, the central node is called as root by which the coordination of other end devices takes place. The end nodes are called as children. In the complete formation of the structure only router and coordinator can have children. Advantages: It offers expandability of the network Disadvantages: The disabling of one parent results into breakage of communication with other devices (Thomsons, 2012). The two nodes which are in close relationship cannot communicate with one another. Mesh Topology: It is the combination of coordinator, many routers, and end devices. It is a multi-hop network which passes packet through multi-hop. Advantages: It helps in eliminating the dead zone (Vallabh, 2014). The communication can takes place with any destination node. Disadvantages: It results into greater overhead. It uses complex routing protocol. 5: Protocol Layer implementation for Wireless HD: The layering model for wireless HD is divided into four functional layer which are named as PHY layer, Mac sub-layer, Adaptation sub-layer, and station management entity. The AVC protocol and A/V packetizer are used in the adaptation sub-layer. The four function entities of the layered model provides services like transmission of high rate data, services related to low data rate, and lastly, the service of management (Marco, 2015). The HR protocol data unit consist of information like identification of beam tracking, use of UEP mode for coding, scrambler initialization, and spatial stream for transmission of packet. The LRP works in the same bandwidth of HRP. The WVAN is the super-frame which is used for Mac layer for the transmission of time slot. A random access time block is used for transmitting data packets. The layered model for wireless HD is shown below: References: Marco, P. (2015). Protocol design and implementation of wireless sensor network(1st ed.). Retrieved from https://www.divaportal.org/smash/get/diva2:572787/FULLTEXT01.pdf Mohammed, D. (2014).WiFi Antenna installation best practices design guide(1st ed.). Retrieved from https://www.lcom.com/content/WiFi%20Antenna%20Installation%20Best%20Practices.pdf Shacklett, M. (2012).Multiple Access Technique(1st ed.). Retrieved from https://www.iitg.ernet.in/scifac/qip/public_html/cd_cell/chapters/a_mitra_mobile_communication/chapter8.pdf Thomson, K. (2010).Zigbee wireless sensor network and their application(1st ed.). Retrieved from https://people.cs.nctu.edu.tw/~yctseng/papers.pub/book-zigbee.pdf Vallabh, V. (2014).IEEE 802.15.4 and ZigBee: A conceptual study(1st ed.). Retrieved from https://www.ijarcce.com/upload/september/2_IEEE%20802.15,4%20AND%20ZIGBEE.pdf Dan, L. (2008). Cooperative Analog digital signal processing(1st ed.). Retrieved from https://www2.ece.gatech.edu/research/labs/cadsp/Publications/paper15.pdf

Wutherin Heights Essays - British Films, English-language Films

Wutherin Heights Through the duration of Heathcliff's life, he encounters many tumultuous events that affects him as a person and transforms his rage deeper into his soul, for which he is unable to escape his nature. From the beginning of the novel and most likely from the beginning of Heathcliff's life, he has suffered pain and rejection. When Mr. Earnshaw brings him to Wuthering Heights, he is viewed as a thing rather than a child. Mrs. Earnshaw was ready to fling it out the doors, while Nelly put it on the landing of the stairs hoping that it would be gone the next day. Without having done anything to deserve rejection, Heathcliff is made to feel like an outsider. Following the death of Mr. Earnshaw, Heathcliff suffers cruel mistreatment at the hands of Hindley. In these tender years, he is deprived of love, friendship, and education, while the treatment from jealous Hindley is barbaric and disrupts his mental balance. He is separated from the family, reduced to the status of a servant, undergoes regular beatings and forcibly separated from his soul mate, Catherine. The personality that Heathcliff develops in his adulthood has been formed in response to these hardships of his childhood. The final sense of alienation and the most implicating occurs with Catherine's marriage to Edgar, Heathcliff considers this a betrayal of his love for her, since she wants the social status and existence at the Grange. Heathcliff is however proud and determined and does not cower when opposed by those consider themselves to be superiors. Finally, when he realizes that Catherine has chosen status, wealth and position over him, he disappears for three years and returns in the manner of a gentleman. As he returns to Wuthering Heights, he is engulfed with this passion to revenge himself on all those who have abused him as a child. He ruins Hindley by encouraging his excessive drinking and gambling. His revenge is also directed towards Edgar Linton, whom he sees as having stolen Catherine from him. His sullen, vengeful, cruel and impatient characteristics still exist, which have been present since childhood, but have grown deeper. He is, in reality, a man torn between love and hate. Since his depths of his passions, he hates as deeply as he loves. As Heathcliff approaches death and a reunion of Catherine, he no longer has an interest for revenge. He falls deeply into a spiritual torment. Heathcliff is a many faced character, in his early years he is characterizes by his hot temper, his irritability, his fierce attachment to Catherine and his limit for hatred. The adult Heathcliff, who returns to Wuthering Heights after a three year absence, is a powerful villain driven by revenge, distorted by the sense of the wrongs done to him and made emotionally unstable by Catherine's marriage. This later Heathcliff is characterized by coldness by an incapacity to love and ultimately by consuming passion for revenge against those who have abused him and for connection with his beloved Catherine. Just as he begins life, he ends life as an unloved, lonely outsider.

economy of jamaica essays

economy of jamaica essays The Jamaican economy is an ailing economy and a prime example of an impoverished nation with an inadequate manufacturing infrastructure, limited nation and agricultural assets and declining foreign investments. With a decline in foreign investments Lee Bailey, President of Cruise Shipping Association who was a guest on the television program, A Nation In Crisis on November 2nd, 2000 at 8:30 pm live on T.V. J stated that with no water, no roads no infrastructure why would foreigners want invest? Why would they want to build a home with these conditions? Mark Kerr Jarrett, President of Montego Bay Camber of Commerce, another guest on A Nation In Crisis stated that law and order must be returned to the streets in order to sell the nation to foreign and local investors. He also said people must reinvest to increase the income of the nation. Jamaica has experience a deteriorating economy along with falling living standards for over 15 years as a result of a heavy debt, a devalued currency and societal malaise. The government is still repaying monies they have borrowed from international leading agencies such as the international Monetary Fund (IMF) and the World Bank. Payment of 3.6 billion in foreign debt alone consumes 49% of the total budget. A series of floods and hurricanes that ravaged the country exposed the governments poor emergency relief preparation forcing authorities to solicit extensive loans from abroad. These debt burdens are an amount of money borrowed together with repayments of interest. Listed below are reasons for an ailing economy: d.) Government measures, stop-go policies related to change in government ...

Analysis of Pricing and Distribution Strategy at British Airways The WritePass Journal

Analysis of Pricing and Distribution Strategy at British Airways Introduction Analysis of Pricing and Distribution Strategy at British Airways Introduction Company’s outlookPricing Strategy Distribution Strategy Evaluation Conclusion and Recommendations  ReferencesRelated Introduction British Airways is the flagship airline carrier for United Kingdom, formed in 1974. With significant presence at Heathrow, Gatwick and London City with over 20 million people living within commuting distance. BA has a fleet of more than 238 aircrafts in service as of March 2010 and flies to 41 different destinations in America, 9 in the UK, 67 in Europe, 16 in the Middle-East and South-Asia and 7 in the Asia Pacific region, carrying around 32 million passengers between 2009 and 2010 as well as operating a large air cargo business alongside. BA, American Airlines, Cathay Pacific and Qantas form the Oneworld airline alliance which is now the third largest airline alliance group. In 2011 BA merged with Iberia forming IAG with 408 aircrafts flying to 200 destinations and carrying 55 million passengers and allowing the two companies to enhance their presence in the market whilst retaining their own brands and allowing their customers to benefit from a larger network of travel (iairgroup.com/ 2011). Company’s outlook British Airways sees itself as a vital link for trade and investment, specialising in short to medium length international journeys which has seen revenue of  £8 billion in 2009/10. This figure is down 11% on the previous year due mainly to price of fuel and the recession. BA’s main activity revolves around passenger travel which accounts for 87% of 2009/10 revenue, supposed to 7% from cargo and 6% from other means. The acquisition of Iberia in 2011 has allowed BA to increase its capabilities in the cargo market and diversify their operations. Both companies float on the Spanish and UK stock markets as one under IAG, which floated in late January 2011 at 282p a share; this has dropped to a price of 224.3p per share as of 4th April 2011. The future for British Airways and IAG will be largely affected by its ability to weather the downturn, but with its promise of drastic expansion and a strong market share within the European market (3rd biggest by revenue) (www.bbc.co.uk/new s 2011) Pricing Strategy British Airways prices its products in a way that allows consumers to decide the level of services they want. For example return flight to New York, purchased online is  £376 in economy yet consumers pay a huge increase to  £2728 for the same flight, (www.britishairways.com 2011) but in first class. BA’s premium and medium strategies offers superior quality for greater price allowing the airline to compete with other quality airlines such as Virgin and American Airlines, and base price on customer valuations The price â€Å"is set higher than others to reflect better product quality and exclusivity.† (Brassington and Petitt, 2003: 1106). However in recent years the arrival of low cost carriers and economic turmoil forced BA into providing a low cost formula to remain competitive. The first step towards this was in generating ancillary revenues by introducing a fee per one way flight for passengers booking a seat in advance for all seats except first class. (GMID 2011) Even in the low cost formula, BA are still upholding their image of quality and good customer service as unlike the low cost carriers, where ancillary revenues are the money makers with food, drink and priority boarding all costing extra, BA still provide some level of on board service in the cost of their product. Despite the introduction of a low cost formula, British Airways generally bases prices on perceived value of its brand, and aims to deliver product quality leadership strategy. (www.britishairways.com 2011) The executive club encourages loyalty to the airline and rewards consumers with double airmiles, priority boarding, additional baggage allowance and access to the BA lounge as well as giving the appearance of high quality and good value. However BA recently lowered the price of their business class ticket due to the recession. It has been recognised the company has had to reduce the price of its business class tickets, to remain competitive alongside such competition as Virgin, who have helped battle down the price, along with it’s cliental that have become less willing to pay higher prices during economic hardship. This has help attract more customers, smaller businesses in particular, who are able to do deals and meet contacts around the world. (Times Online 2011). An excellent strategy that has allowed BA to get away from just large organisations and into the smaller/medium sized business market (GMID 2011) is their Face to Face campaign which, on submittance of a business plan, small/medium sized businesses can apply for free business travel. The marginal cost of one more passenger is relatively small, as the majority of costs are largely in fixed costs of running the flight (cost of aircraft, fuel, airport duties etc.). According to Chris Tarry, transport analyst for Commerzbank Securities, BA’s selling cost per passenger in March 2002 was just 10.9% of its average ticket price (insights.org.uk 2011). This allows BA to sell tickets at lower rates when demand is less and higher rates during peak season. For example an economy class ticket to New York would normally be  £376 return but almost doubles over the peak bank holiday period of the Royal Wedding at  £616 (www.britishairways.com 2011). The airline aims to get as many people on the plane as possible, even at a lower price, and make some profit, than the plane taking of near empty and making a loss. Distribution Strategy British Airways tickets are available to purchase from travel agents physical locations and online via their websites, and through BA’s dedicated website, travel shops and reservations staff. With e-commerce radically changing distribution strategies (Solomon et al, 2009), BA and various other airlines are trying to reduce costs to ensure they continue to effectively compete against other players within the airline industry and still provide each customer with their superior service by eliminating their use of various ‘traditional intermediaries’ (Solomon et al, 2009) within their distribution channels. Globally 20% of British Airways tickets are now sold via ba.com, with 54% of these online bookings accounting for their total short haul sales stated by docstoc (2010). It’s recognised from these statistics that the convenience of purchasing airline tickets online is attractive, due to the ability to securely acquire a flight ticket without leaving the comforts of your own home, as well as that purchasing tickets direct from BA.com is significantly cheaper than leading travel agents, for example an economy class ticket flying from London to New York can be purchased for  £368 straight from BA where as Expedia offer the same flight for a staggering  £432.10. However, there is still an area of the market who enjoy purchasing their airline tickets from travel agents physical locations, this is due to travel agencies providing the customer with the same options as to the airline website itself, in such areas as seat preferences, along with the additional personalised service w hich the customer is able to discuss the range of options available to them when booking all areas of their holiday, be their hotel or hire car. An attempt to create a more direct distribution channel process, BA also provides the recognised ‘travel agent’ service options to its customers, through offering a range of hotels, car rental and various other holiday package choices. The various options available to consumers when purchasing BA airline tickets are either through travel agents, or alternatively buy their ticket straight from the BA website, travel shops and reservations staff. It’s seen that prices do vary depending on where tickets are purchased, for instance if a consumer were to purchase their ticket directly from BA’s website, they would commonly pay a lower price, due to the direct business to customer distribution channel, eliminating the need for BA to pay commission to travel agents which is ‘traditionally between 8% and 10% of the ticket price’ (tourism insights, 2002) and for the use of Global Distribution Systems (GDS). GDS is used by airlines to sell flights, through connecting both the airline and the travel agents to sell the tickets. Airlines pay GDS to connect them to travel websites and travel agents to enable their flights to be sold via these organisations, GDS segment fees average at around ‘$10 to $12 per booking’ (tourism insights, 2002). With BA’s distribution costs accounting for 16%-17% of the cost of selling each ticket, no wonder they want to reduce distribution channels to help become more competitive in the growing low fare airline industry, especially due to the ‘travel and tourism industry fast becoming the biggest growth industry in e-commerce payments,’ (docstoc, 2010). Evaluation Overall it is clear that British Airways are aiming for a much more direct distribution channel. They are investing huge amounts of money in improving their online services to try to encourage people to buy online rather than at the extra cost of the middle man travel agent. This also allows the airline to gain vital information about their consumers and their wants and needs, allowing the company to differentiate and target their services appropriately. This will ensure they enhance their competitive market position, through enabling them to provide special offers to different customers, for example in the form of special discounts, special seats with more leg room and passes for their lounges, allowing them to build better relationships with their customers.   The high growth in e-commerce selling in the travel and tourism market is further proof of how important it is for BA to perfect this particular method of distribution. The lower costs from eliminating a middle man, includi ng both online and shop based agents will also allow the firm to appear more competitive in comparison to low cost carriers (LCCs). The introduction of ancillary products and reduction in price of business class tickets has been key in promoting the price competitiveness of the airline alongside the strong brand image of quality and reliability. The low marginal cost of an extra passenger also gives the airline the ability to lower costs depending on the demand for their product at the time of year; this means that BA can offer their business clients lower prices when it is not peak season such as school holidays. Conclusion and Recommendations By providing more ancillary goods and a reduced cost of the seat, BA will give consumers the options of what they want and become more competitive with the LCC’s, who are extremely popular for short haul flights. For example providing the option to charge extra for food and drink or extra baggage on short haul flights as well as an all inclusive option. Many of the LCC’s only distribute tickets online. To uphold BA’s strong brand image it’s important for them to stay accessible through other distribution systems as many of their more wealthier cliental who spend the most via business and first class tickets, may desire a travel agent. By marketing their online travel agent services they may be able to increase their current 20% online distribution. This will provide a more direct channel to their customers allowing them to market events such as the BA January sale, flights to cheaper destinations and cheaper times to fly that consumers may otherwise be unaware of. Marketing the executive club more effectively to new customers and ensuring that by being a member, consumers actually receive some benefits, they’re likely to remain loyal and recommend the airline. BA could also improve their services by providing questionnaires to passengers. For example, on long haul flights when consumers are more likely to fill them in, and providing a reward – such as a draw for a bottle of champagne. By doing this the company will be able to find out if consumers choose them for their prices, customer service, quality or the routes that they operate under and use this to market the company accordingly. It is clearly important for BA to remain competitive with the LCCs by providing an alternative to the high quality and high price product they currently provide but still keeping their high quality image and providing a service that current, loyal customers expect. Effective online distribution and optional ancillary products are key in achieving this alongside accurate customer research from current and potential consumers. The airline should continue to use their low marginal costs to their advantage when promoting the airline to businesses and off peak travellers.   References Balmer, J.M.T, Stuart, H Greyser, A.S (2009) Aligning Identity and Strategy: Corporate Branding at British Airways in the Late 20th Century, CALIFORNIA MANAGEMENT REVIEW VOL. 51, NO. 3 BBC News: bbc.co.uk/news/business-12265332 [Accessed 4th April 2011] Brassington, F, Pettitt, S (2000), (2nd Edition) Principles of Marketing Harlow, Prentice Hall British Airways (2011) www.britishairways.com [accessed 19th March 2011] British Airways (2011) Buy Travel [Online] britishairways.com/travel/fx/public/en_gb?eId=111011timestamp=0315023921 [Accessed 15th March 2011] Docstoc (2010) Visa Case study: British Airways come buy with me –worldwide airline offers worldwide online protection [Online] docstoc.com/docs/26949398/britishairways [Accessed: 6th March 2011] Expedia (2011) Flights [Online] expedia.co.uk/pub/agent.dll [Accessed 15th March 2011] GMID portal.euromonitor.com.chain.kent.ac.uk/Portal/ResultsList.aspx [Accessed 7th March 2011] Insights (2011) insights.org.uk/articleitem.aspx?title=The+Changing+Face+of+Airline+Distribution [Accessed 20th March 2011] International Airlines Group (2010) iairgroup.com/   [Accessed 4th April 2011] Solomon, Marshall, Stuart, Barnes Mitchell (2009) Marketing: Real People, Real Decisions. Essex, Pearson Education Limited. Times Online (2011) http://business.timesonline.co.uk/tol/business/industry_sectors/transport/article5477962.ece [Accessed 17th March 2011] Tourism insights (2002) The Changing Face of Airline Distribution [Online] insights.org.uk/articleitem.aspx?title=The+Changing+Face+of+Airline+Distribution [Accessed: 6th March 2011]

Marketing Plan Research Paper Example | Topics and Well Written Essays - 2250 words

Marketing Plan - Research Paper Example Satellite television has premium charges and many people cannot afford its charges. The Beat Broadcasting Network realized this and decided to proceed with the cable television. In so doing it came up with a product service called biTV: which is internet Television and has drawn up a marketing plan to facilitate the implementation of the service to many of its subscribers. Executive Summary of Marketing Plan The Beat Broadcasting Network is an international media company based in America that specializes in cable-based television broadcasting. Through a comprehensive market research the company has realized the importance of cable television especially to the upcoming markets in other continents such as Africa. The company has decided to launch a new television service in the market called the biTV service. This is internet television that is aimed at providing flexible content and affordable prices to the company’s subscribers. Viewers will subscribe to the service and depend ing on the duration of their subscription will access various contents and channels that will be streamed directly to their home Television or PC as long as they are connected to the internet. The purpose of this service is to maximize on sales and profits and to penetrate other continents that the company is yet to make a huge impact. The pricing will be low and this is aimed at getting more people to identify with the company and secondly because the target population is the young generation that are still unstable financially. This service aims at changing the state of the internet television in the market by providing flexible coverage and content to everyone at affordable prices. Company Overview Beat TV was launched in in 1996 as the fifth cable television provider. The company was established from a sister company named The Beat News Network that has a global coverage. This company is owned by two American brothers and renowned journalists who began it to provide entertainmen t and maximize on advertisements in the industry. The Beat Television network has many affiliates and these operate many entertainment channels internationally, broadcasting programs in the US and in local countries. The company was rated as one of the best cable TV in a survey covering people aged between 16 and 49 coming second to Fox TV. It became popular because of its programs that majorly target the young generation producing content that the youths easily identify with and a wide range of other programs that cover a majority of the age groups unlike other cable television networks. The company is fifteen years old and enjoys coverage globally targeting the young and the middle age group in America and the rest of the world. Company has no partnerships but enjoys the coverage of the parent company, The Beat Broadcasting Network that has always supported its marketing activities, though not all activities that are aired by the beat Network are aired by the Beat Television. Rece nt successes in entering the African market have given it a big boost keeping in mind that most American Television networks operate in Europe and Asia. It has partnered with local television networks to air content both local and foreign especially movies and series. The company’s total revenue increased from 1.5 billion in 2009 to 1.8 billion in 2010 representing a 16 percent increase in revenue. This was attributed to the expansion in the African markets and the

Jehovah Witnessess feelings about receiving blood and how it should be Research Paper

Jehovah Witnessess feelings about receiving blood and how it should be handled with a minor child in a life or death situation - Research Paper Example The insistence of Jehovahs Witness parents in refusing blood transfusions for their children can be viewed in the larger context of alternative religious beliefs and their effect on medical treatment. Many people in contemporary society are guided by religious beliefs which prohibit them from accessing medical care in favor of spiritual healing (Catalano, 2010, p. 157). Whilst adults have the right to refuse medical treatment, their behavior becomes controversial when they refuse medical treatment for their ill children (Catalano, 2010, p. 157). The decision to refuse medical treatment to children may necessitate intervention by the State in cases when children suffer from serious illnesses (Catalano, 2010, p. 157). Many Constitutional issues are raised by this situation, such as religious freedom, the right to privacy, and fundamental liberty issues related to parenting (Catalano, 2010, p. 157). In such cases the Courts are forced to decide between the religious liberty of the paren ts and the States interest in protecting the lives of minors (Catalano, 2010, p. 158). This matter if particularly controversial because no matter what the outcome of, somebodys rights are infringed (Catalano, 2010, p. 158). In some cases government intervention is secured too late and the childs life is lost (Catalano, 2010, p. 158). Between 1975 and 1995, 172 children died because they were denied medical care for religious reasons (Catalano, 2010, p. 158). The State must balance the interests of religious parents and their innocent children, respecting the welfare and autonomy of both parties. A fundamental concern of the state is the protection of the welfare of children, one for which it may intervene when it is absolutely necessary (Catalano, 2010, p. 159). Despite this fundamental concern, the United States gives parents ample autonomy to raise their children in the

Mac Os X Essay Example for Free

Mac Os X Essay The Mac OS X Panther operation system has met with both technical and commercial success. Since the debut of Mac OS X in 2001, its features have continued to improve. The initial system Mac OS X 10. 1 was originally shipped in September 2001 and was referred to as Puma; Jaguar, version 10. 2, was shipped in August 2002, and Panther, the current version, was shipped in October 2003. The focus of this paper is on the key technologies that have made Mac OS X Panther a technical success such as CPU scheduling, symmetric multiprocessing, memory protection, and virtual memory; we begin with an overview of the MAC OS X operating system. Overview of Mac OS X Panther Mac OS, from Apple Computer, can be considered two families of operating systems: the older and now unsupported classic Mac OS (the system that shipped with the first Mac in 1984 and its descendants, culminating with Mac OS 9), and the newer Mac OS X. Mac OS X Panther is a UNIX-based Operating System with the intuitive user interface called Aqua. The modern core UNIX-based Operating System brings benefits such as protected memory and preemptive multitasking to Macintosh computing. Mac OS X Panther also has a sparkling user interface capable of visual effects such as translucence and drop shadows. The central characteristic of the Mac OS X architecture is the layering of system software, with one layer having dependencies on, and interfaces with, the layer beneath it (see Figure 1-1). Mac OS X has four distinct layers of system software (in order of dependency): Application Environments consists of the frameworks, libraries, and services necessary for the runtime execution of programs developed with those API. Mac OS X currently provides five application (or execution) environments: Carbon, Cocoa, Java, Classic, and BSD Commands. Application Services incorporates the system services available to all application environments that have some impact on the graphical user interface. It includes Quartz, QuickDraw, and OpenGL as well as essential system managers. Core Services incorporates those system services that have no effect on the graphical user interface. It includes Core Foundation, Open Transport, and certain core portions of Carbon. Kernel Environment provides the foundation layer of Mac OS X. Its primary components are Mach 3. 0 and FreeBSD, but it also includes networking protocol stacks and services, file systems, and device drivers. The kernel environment offers facilities for developing device drivers (the I/O Kit) and loadable kernel extensions, including Network Kernel Extensions (NKEs). This integrated kernel environment is called Darwin and it is an Open Source technology available from www. apple. com/darwin. The following is the components that Mach 3. 0 and FreeBSD provide: Mach †¢ support for SMP †¢ untyped IPC and RPC memory management †¢ support for real-time services †¢ external pager †¢ modular architecture †¢ improved performance BSD †¢ file systems †¢ networking †¢ basic security policies such as user IDs and permissions †¢ the system framework a mechanism for exporting APIs to the application layers †¢ the BSD process model, including process IDs and signals †¢ FreeBSD kernel APIs †¢ Pthre ads (POSIX threads implementation) [pic] Figure 1-1 System Layer CPU Scheduling The kernel environment of Mac OS X, specifically Mach, provides the fundamental thread support. Mach maintains the register state of its threads and schedules them preemptively in relation to one another. In general, multitasking may be either cooperative or preemptive. Classic Mac OS implements cooperative multitasking which was not very intelligent. In cooperative CPU scheduling the OS requires that each task voluntarily give up control so that other tasks can execute, so unimportant but CPU-intensive background events might take up so much for a processor’s time that more important activities in the foreground would become sluggish and unresponsive. On the other hand, preemptive multitasking allows an external authority to delegate execution time to the available tasks. Mac OS X’s Mach supports preemptive multitasking in which it processes several different tasks simultaneously. To affect the structure of the address space, or to reference any resource other than the address space, the thread must execute a special trap instruction which causes the kernel to perform operations on behalf of the thread, or to send a message to some agent on behalf of the thread. In general, these traps manipulate resources associated with the task containing the thread. Mach provides a flexible framework for thread scheduling policies. Mac OS X supports both the multilevel feedback queue scheduling and round-robin (RR) scheduling algorithm. The multilevel feedback queue scheduling algorithm partitions the ready queue into several separate queues and allows a process to move between queues. In the multilevel feedback queue scheduling algorithm, each run queue has various priorities that are handled in different ways. A multilevel feedback queue scheduling thread’s priority is raised and lowered to balance its resource consumption against other threads. Round-robin threads execute for a certain time quantum (time slice), and then are put at the end of the queue of threads of equal priority. Setting a round robin thread’s quantum to infinity effectively makes the thread run-till-block within its priority. Mac OS X internally has 128 priority levels, ranging from 0 (lowest priority) to 127 (highest priority).