Computer Networks And Wireless Transmissions

Computer Networks And Wireless Transmissions In telecommunications, wireless communication may be used to transfer information over short distances or long distance. The term is often shortened to wireless. it encompasses various types of fixed , mobile, cellular telephones etc. now -a days people who need to be online all the time. For these mobile users, twisted pair, coax, and fiber optics are of no use. They need to get their hits of data for their laptop, notebooks, shirt pocket or wrist watch computers without being tethered to the terrestrial communication infrastructure. For these users, wireless communication is the answer. THE ELECTROMAGNETIC SPECTRUM Wireless transmission can provide special services and conveniences to people, such as connection to the internet or other networks without connecting to wire directly. It can also facilitate the creation of networks in special situations, such as terrain that is unfriendly to ground cables. Wireless communication began, in fact, in the Hawaiian island precisely the problem of terrain separated by large stretched of ocean. Political organizations determine which sections of the spectrum of light are all to which wireless transmission purpose. Because the existing organizations are always in agreement with current practice or with each other, some products manufactured for one country may not work in another. RADIO TRANSMISSION Radio waves are easy to generate and are omnidirectional, but have low transmission rates. Also, depending on their frequency, radio waves either cannot travel very far, or are absorbed by the earth. In some cases, though, high frequency waves are reflected back to earth by the ionosphere. Ionosphere is a layer of the atmosphere. MICROWAVE TRANSMISSION Microwave transmission is popular for its ability to travel in straight lines. A source can be directly focused on its destination without interfering with neighboring transmissions. Because they travel in straight lines, though, the curvature of the earth can interfere with the microwave transmitters. The solution to this is the addition of repeaters in between the source and destination to redirect the data path. Microwaves are used for long distance communication like cellular phones, garage door openers and so on.. INFRARED AND MILLIMETER WAVES Infrared light is used for close- range communication, such as remote controls, because if does not pass through objects well. This is also a plus because infrared communications in one room de not interfere with the infrared communications in another room. Infrared communication is more secure than other option, such as radio, but it cannot be used outside due to interference by the sun. LIGHTWAVE TRANSMISSION Lasers can be used for wireless communication. It is a relatively low cost way to connect two buildings LAN, but it has drawbacks. The laser is difficult to target on the destinations receiver because the beam is so small. Laser light also diffuses easily in poor atmospheric conditions like rain, fog and so on. TERMS OF WIRELESS TRANSMISSION The theoretical basis for data communication Transmission media Wireless transmission The telephone system Narrowband ISDN Broadband ISDN and ATM THE THEORETICAL BASIS FOR DATA COMMUNICATION Harmonics An infinite series, such as a Fourier series, is just the addition of an infinite number of terms. Each term is called a harmonic. Baud Signals are used to send data over a write. If we want to indicate a data change, there is a corresponding signal change on the wire. The maximum possible number of signal changes per second is called the baud. Fourier Series A periodic function is one that repeats itself over time. Sine and cosine are periodic functions. Fourier proved that any reasonably behaved periodic function could be written as a sum of sine and cosine functions. This is important because sine and cosine are easily represented and recreated. The Fourier series allows periodic signals to be sent over a wire. Voice-Grade Line A voice-grade line has certain restrictions that limits the maximum number of signal changes per second. Signal-To-Noise Ratio Decibels A way to measure to measure the thermal noise that is present on a wire. TRANSMISSION MEDIA Here more than ten terms are there so I am going to explain five terms: Magnetic Media Material on which to store data. It is used in diskettes and magnetic tape. Magnetic media is a common way to transport data quickly. Twisted Pair The oldest and still most common transmission medium. Two insulated copper wires. Twisting the wires reduces electrical interferences from nearby wires. It also counters the antenna effect caused by parallel wires. Head-End In a dual cable system, there are two cables which only transmit data in one direction each. At one end of the network, data is collection from one line for re-transmission on the line going the opposite direction. The end of the network responsible for the data collection and retransmission is called the head-end. Subsplit When two cables are not used, but there is need for simulation of dual cable system, bandwidth on a single cable can be split up, with one portion representing one cable, and the other portion representing the second cable. Splitting the frequencies so that the lower frequencies are used for one purpose and the higher for another is called a subsplit system. Mode Characteristic of a light wave associated with the reflection of the wave through the silica fiber. WIRELESS TRANSMISSION Frequency (F) Light and electricity travel in the form of waves. Waves are periodic in that they repeat themselves, so the frequency of a wave is just the number of times the wave repeats itself in one second. Hertz (Hz) The unit of measure of frequency. The name comes from the german physicist who first produced electromagnetic waves. Wavelength (Lambda) Wavelength is the measure of the length of a wave that is it is used ti find the distance between two consecutive maxima or minima. Speed Of Light (C) The speed that electromagnetic waves travel in a vacuum approximately 3*108 m/sec. electromagnetic waves do not travel as fast through a medium as they do through a vacuum. Spread Spectrum A pattern for EM transmission which is popular in the military for its ability to avoid jamming. The transmitter hops from frequency to frequency across a wide frequency band. THE TELEPHONE SYSTEM In this there are more than ten terms so here I am going to explain six terms Public Switched Telephone Network The currently existing network used for telephone communication. It was designed specifically for voice, and is not well suited for use by computers for transmitting data to one another. End Office The place to which your telephones lines connect to receive the telephone service. The distance from the telephone to the end office is usually small around 1 to 10km). Toll Offices Switching centers that connect several end offices. Tandem Offices Similar to the toll office, except it connects the end offices that are within the same local area. Toll Connecting Trunks The hardware which connects the end office to the toll of offices. NARROWBAND ISDN Integrated Services Digital Network Fully digital, circuit switched telephone system that is designed to accommodate both voice and data services. Digital Bit Pipe A bi-directional logical pipe which will pass bits on from source to destination without concern about whether they are voice. NT1 Device placed between the user and the nearest end office allows ISDN connection. Plain Old Telephone Exchange or NT2 Device placed between the end user which can provide a variety of ISDN services. Narrowband ISDN ISDN services on 64-kbps channels. BROADBAND ISDN AND ATM Broadband ISDN It is more recent design for a digital network on which data can travel rates of 155Mbps. It is based on ATM technology. Permanent Virtual Circuits Virtual circuits that remains in place for extended periods of time. Switched Virtual Circuits Virtual circuits that remains in place for short periods of time, typically related to the session time. Head-Of-Line Blocking If a questionable cell tries to come into ATM switch, it will be stalled, effectively stalling the cells behind it unfairly. This is called head-of -line blocking. Knockout Switch To solve the head-of-line blocking problem, queuing on the output side has been proposed. The knockout switch does just this, by stimulating a single output queue by having several output queues that are activated on a round- robin type basis. FORMULAE THE THEORETICAL BASIS FOR DATA COMMUNICATION Baud Rate The baud rate is NOT the same as the data rate. Baud tells how many signals are sent per second, but there are ways of encoding more than one bit per signal change. AVOID getting this confused. Baud= number of signal changes/second Maximum Data Rate Of A Channel (Nyquists Theorem) Max data rate=2 Hlog2 V H=bandwidth in HZ V=discrete levels This formula shows the maximum number of bits that can be sent per second on a data line with a bandwidth of H, is V bits are sent per signal. The max data rate should be in bits per second. Signal-To-Noise Ratio 10log10(S/N) S=signal power N=noise power This formula is used to quantify the quality of a line. It is not usually presented as a ratio, but instead it is given in the units decibels. Maximum Number of Bits Per Second (Shannons Result) Max number of bits per second=H log2 (1+(S/N)) This formula shows the maximum achievable data rate on a noisy line. The difference between shannons result and Nyquists theorem is that Shannons result takes the noise on a line into consideration. The noise can drastically reduce a lines capacity to send data. It is measured in bits per second. TRANSMISSION MEDIA Attenuation 10 log10 (transmitted power/ received power) Attenuation is a way to measure the amount of power lost in a signals strength from when it was sent to when it was received. Attenuation is measured in decibels. WIRELESS TRANSMISSION This formula is used to find the relationship between frequency, wavelength, and the speed of light. Lambda f=c Lambda=wavelength F=frequency C=speed of light THE TELEPHONE SYSTEM This formula is used to fine the bits per second. Bits per second= number of bits per signal change*baud. BIBILIOGRPHY Google.com Wikipedia.com

What reading you enjoy the most

Question 3 what reading have you enjoyed most in the past year and why? The reading I have enjoyed the most In the past year Is To kill a mocking bird' by Harper Lee The Storrs main theme is about racial discrimination and gender Inequality. It used a child's point of view to tell the story so I can throw myself Into the main character Scout. Thanks to her naivety, the injustice and the hypocrisy of Maycomb folks are enhanced. The most excltlng part of the story Is the tight In the court. Scout's father is a lawyer and he is trying to fight for a black man.Although I expect there will be a courageous character to stand up and correct the bias but it comes out as a bad ending, which prejudice Is Imposed. However I can still sense that the author is trying to tell us what is wrong and what is right If I have to use a word to describe the story, the word would probably be: Amazing. My emotion flows with the story, and every detail is mentioned clearly, Harper's writing is really coheren t as well. I was reminded that â€Å"Your never really understand a person until you consider things from his point of view†¦ til you climb inside of skin and walk around in It. † This is an absolute delight reading and I highly recommend others to read. The reading I have enjoyed the most In the past year Is ‘To kill a mocking bird' by Harper Lee. The storys main theme is about racial discrimination and gender inequality. It used a child's point of view to tell the story so I can throw myselt into the Maycomb folks are enhanced. The most exciting part of the story is the fight in the court. Scouts father is a lawyer and he Is trying to fight for d black man.Although I comes out as a bad ending, which prejudice Is Imposed. However I can sull sense that the author is trying to tell us what is wrong and what is right. If I have to use a word to describe the story, the word would probably be: Amazing. My emotion tlovw with the story, and every detail is mentioned clea rly, Harpers writing is really you consider things from his point of view†¦ untll you climb Inside of skin and walk around in it. † This is an absolute delight reading and I highly recommend others to read.The reading I have enjoyed the most In the pastyear Is ‘To kill a mocking bird' by Harper Lee. The storys main theme is about racial discrimination and gender inequality. It used a child's point otviewto tell the story so I can throw myselt into the court. Scouts father is d lawyer and he Is trying to fight for d black man. Although I 1 Of3 coherent as well. I was reminded that mfour never really understand a person until you consider things from his point of view†¦ Until you climb inside of skin and walk read.The reading I have enjoyed the most in the past year is ‘To kill a mocking bird' inequality. It used a child's point of view to tell the story so I can throw myself into the court. Scout's father is a lawyer and he is trying to fght for a black ma n. Although I comes out as a bad ending, which prejudice is imposed. However I can still sense by Harper Lee. The story's main theme is about racial discrimination and gender Maycomb folks are enhanced. The most exciting part of the story is the fght in the coherent as well. I was reminded that miour never really understand a person until

The Effects Of Global Warming On Our Economy - 1090 Words

Global warming is â€Å"The increase in Earth’s average surface temperature due to rising levels of greenhouse gases† (NASA). This issue is not a myth anymore, is affecting our economy, health and our future aggressively. The need to reduce pollutant emissions is now something urgent and an important commitment for all the nations. Natural disasters, virus and diseases are consequences of changes of temperature, the emissions of carbon gases weaken the ozone layer, water and food pollution. According to the World Health Organization, environmental pollution produces more than seven million of deaths every year. The global warming has been causing damage in this country, the last year (2014) has been considered the hottest year in United†¦show more content†¦Other argument for withdraw, was that the implementation of the treaty was inefficient and unfair involving just the developed countries and excluding from restrictions some of the biggest emitters of gases like China and India, because they are considered developing countries. Before the Federal Government began to focus in this problem, the private sector was trying to create programs for the reduction of pollution, but without the political and financial support of the government, all these efforts were insufficient. There are some federal laws to protect our environment and health. The Clean Water Act which prohibits sending pollutants into waters by requiring specific sites that discharge materials. The Clean Air Act has been improving the air quality since 1960. Some of the most recent energy legislation include the Energy Policy Act (2005), the Energy Independence and Security Act (2007), and the Energy Improvement and Extension Act (2008). With the Energy Policy Act, the tax incentives have been reduce the costs of develop and adoption of new technologies (Matzner). Today, as a new political commitment to save the planet, the president Barack Obama has created The Clean Power Plan, its principal objective is a thirty percent reduction of carbon pollution from the power sector by 2030. Coal plants are the largest generators of gases and the principal

American Criminal Justice System Change - 990 Words

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