PowerLineCommunication.doc

power line communication:coming to an outlet near youby pam bosanacdr. chuck westbma 373 section 1february 18, 2002plugging in a personal computer to an electrical socket and obtaining internet access may seem absurd to some. however, just as easily as plugging in a toaster, consumers will soon be able to connect to the internet. although the concept of power line communication (plc) seems to be a fairly new one, it has actually existed for quite a while. since 1899, when the first patent on the idea was issued, the technology has experienced a variety of improvements and standards testing (nunn 1). recently it has begun to catch on in the united states. a team of five germans patented the idea back in 1997 (flin 1) and standards from homeplug powerline alliance debuted only in june of 2001 (mainelli power 1). nevertheless, utility companies put plc into effect a long time ago, by using electrical lines to activate streetlights (stevenson). as technology advances, homeowners will soon see this same technology in individual homes and businesses.with power line communication, receiving internet access can be as easy as plugging in a small electrical appliance. this type of communication uses existing wires, cables, and electrical outlets in order to design a small home network (mainelli power 1). many people who do not have access to phone lines may connect to the internet by using power lines already on hand. not only are power lines more accessible to people, but power does not even have to be running through the wires in order to remain connected (kenyon 2). the process starts at power substations that are connected to the internet with fiber optic cables and routers. from here, digital information is transformed into analog radio frequencies that run through the power lines. once these signals reach the transformers near homes, information is converted back into digital form that runs through a special modem plugged into an electrical outlet in order to be downloaded to the individual pc (stevenson). the speeds in which this process can occur vary depending on which standards are used and how many homes are connected to the transformer. most speeds will vary between two to ten megabits per second. with speeds comparable to ethernet devices and the opportunity for almost anyone to connect to the internet, power line communication is progressively becoming more available. as connections increase in number, more opportunities and uses for power line communication become available. the main use of power line communication is likely to be a home network. much like a local-area network, plc offers the opportunity for homeowners to allow simultaneous connections from various pcs in the home, as well as being connected to peripherals such as printers. along these same lines, users will be able to download digital media and use the power lines to listen to music on home stereos or watch movies on dvd players that are all connected to the same network (dow 1). while home networks provide a common use for power line communication, for a variety of reasons, home automation is also becoming quite common. without requiring installation of special wires, users are able to control lights, heating, and other appliances using the internet (dow 1). another home automation service includes alarm monitoring (kenyon 2). by combining the use of power line communication and wireless technologies, a user would be able to turn on or off an alarm system, regulate the temperature, and even record a television program from the office or on vacation using a notebook computer or personal digital assistant. also offered by plc would be the opportunity to use multi-utility monitoring (nunn 1). instead of receiving three separate bills for water, electric, and gas, customers will only receive one bill. this could improve billing procedures not only for customers, but also for the companies involved. individual home users are not the only ones that benefit from power line communications. this technology has proved also useful in hospital patient-data-management systems, point-of-sale terminals, and even vending machines (strassberg 3). adaptive networks incorporated already manufactures equipment that is used in connecting many cash registers in department stores in various regions throughout the united states. the company also uses its technology to network display signs on commuter trains, regulate controllers for refrigeration units, and voice communications in mines (kenyon 1). the opportunities for power line communication continue to expand every day as technology progresses, while the advantages become more apparent.the opportunity to connect anywhere that possesses power lines lends itself to the most beneficial advantage: ubiquity. because power lines exist almost everywhere, even in places that are too poor to afford telephone lines, the advantage of power line communications is self-explanatory. for example, in brazil, 93% of households are connected to an electrical system whereas only 17% have access to a telephone connection (dow 2). there are electrical outlets in every room of a house, office, and in schools, which can provide the connectivity that users desire. along with being able to connect from almost anywhere, plc offers a permanent online connection (nunn 4). as with any new networking technology, speed is always an issue. speeds for plc range from two to ten megabits per second. however, some standards from homeplug alliance allow speeds up to 14 megabits per second. according to michael propp, president and certified executive officer of adaptive networks incorporated, as technology improves, it is possible to see throughput rates upwards of 40 to 50 megabits per second (kenyon 2). just as speed is an issue, cost of the new technology is sometimes an even greater issue. because most of the infrastructure is already in place, the cost of power line communication is much lower than other technology, such as fiber optic cables. if someone were to rewire a home with fiber optic lines, it could cost anywhere between $20,000 and $200,000 (kenyon 2). however, because power line communication uses the already existing wiring, a user needs to buy a bridge product for around $150 and a router for less than $200, according to homeplug powerline alliances pricing (mainelli ces 1). not only are the costs for customers lower than expected, markets available for companies involved far exceed what was originally expected. amperion, a power line communications equipment producer, estimates the market for this product to be over $100 billion (stevenson). with a market this large, it is no surprise to anyone that this technology is beginning to catch on and grow steadily.because of the availability of power lines and the low cost of installation, power line communication provides an excellent solution for the “last-mile.” for many older buildings, it is much too costly to install any new wiring, thus, using ac power lines to connect to the internet and form a network serves as the perfect solution (kenyon 2). this opens doors for businesses and homes that would not otherwise be able to afford to rewire the premises. plc also provides a usability advantage. this technology has an advantage to be a user-friendly system. all of the data can be routed to a transformer near a home, in which the electrical wiring becomes a local-area network. therefore, all the user needs to do is simply plug in the modem to the electrical outlet (bryce 2). the simplicity of the connection is a great benefit to those who are not as technologically advanced but still would like the advantages of a home network. the ubiquitous presence of power lines, the inexpensive installation, the speed, and the easy “plug and play” connection gives power line communication the advantage over other forms of data communication.while power line communications have come a long way since first introduced and appear advantageous, various drawbacks remain. unlike in europe, the technology continues to spread slowly in the united states, partially because of the difference in power grids between the two areas (bryce 1). in europe, where the standard voltage is 220 volts, a transformer can provide plc service to anywhere between 200 and 300 homes. however, in the united states, because of its lower voltage standard, a single transformer can only provide service to between four and twelve homes (dow 2). although technology is being developed that can overcome this difficulty, plc still struggles to catch on in the u.s. the main downfall of plc is the high amount of interference caused by any other electrical appliance or lightning strikes. a surge in voltage can easily cause interference in data transfer (strassberg 1). even though power does not have to be running through the line in order to remain connected, a power fluctuation has the potential to generate a large amount of noise or possibly cause minor malfunctions in certain devices (kenyon 3). consequently, there may be times where data is not transferred correctly between sender and receiver. not only do small appliances cause interference, but radio frequencies can also cause interference from radio signals to power lines and vice versa. interference can stem from other networks as well as radio frequencies and power fluctuations (flin 4). because of a large variance in electrical impedance, a high level of signal attenuation can occur. in order to combat this problem, the goal is to sustain a high signal to noise ratio (nunn 3). these problems may seem to be a permanent negative aspect of power line communications, but solutions are being developed. solutions could include setting specific limits for radiation from power lines or using filters to protect networks from unwanted signals (flin 4). as technology increases and more research is done on power line communications, users should see an increase in the quality of data transfers.unfortunately, interference is not the only downfall of the plc technology. several other pitfalls exist. for example, a high-quality solution has not yet been found to translate the technology into devices that work. additionally, plc has yet to allow for converting this solution into increasing speeds for commercial and industrial applications (kenyon 3). also, plc technology has not been developed enough to keep up with the multimedia uses. consumers continue to change towards the direction of using technology for audio visual purposes, making it crucial for the quality of data transfer to exceed normal levels (kenyon 3). other disadvantages that exist include the need for a unique topology and security issues. special techniques are required when it comes to building a plc network because it is necessary to ensure that there is always a possible communications signal path. because of this, the topology is extremely complex and variable (nunn 3). another issue that faces the concept of power line communications is security. the concern of many users is that by using a regular power line, others would easily be able to tap into the same line and gain access to alarm systems, e-mail, and other personal documents. these disadvantages may seem extremely critical, but the benefits of using power line communications seem to lessen the severity.power line communication has quickly gone from a far-fetched concept to a reality. in the past few years, the communications industry has seen the emergence of this technology from its initial stages of standards development to testing in normal households. plc is slowly catching on in the united states, but has spread rapidly throughout europe. it offers a wide range of functions for any type of user for a fraction of the cost that it would take to rewire a house or a small business. despite the difficulties power line communication faces, the concept of plugging a pc into an electrical socket and automatically connecting to the internet, appeals to many people. because of its ubiquity, this technology could soon be the major wave of the future. works citedbryce, robert. “division of power: powerline access surges abroad, shorts out in u.s.” interactive week. 23 apr. 2001. vol. 8 issue 16, pg. 39. 31 jan. 2002. .dow, anna. “high-powered bandwidth.” cisco iq. 31 jan. 2002. /app/tree.taf?asset_id-55686.flin, david. “dune plugging into the telecommunication revolution.” modern power systems. aug. 1999. vol. 19 issue 6, pg. 46. 31 jan. 2002. .kenyon, henry s. “plug in, turn on, surf away.” 1 sept. 2001. 1 feb. 2002. .mainelli, tom. “ces shows something shocking: powerline networks that work.” pcw. 8 jan. 2002. 31 jan. 2002. /news/article/0,aid,78724,00.asp.mainelli, tom. “power line network standard debuts.” pcw. 26 june 2001. 31 jan. 2002. /news/article/0,aid,53683,00.asp.nunn, clive. “data pipeline, or data pipedream?” modern power systems. nov. 1998. vol. 18 issue 11, pg. 21. 1 feb. 2002. .stevenson, david. “accessing the net through electrical outlets.” techtv. 24 jan. 2002. 31 jan. 2002. /news/internet/story/0,24195,3369550,00.html.strassberg, dan. “powerline communication: wireless technology.” edn access. 6 june 1996. 13 feb. 2002. /archives/ednmag/reg/1996/060696/12dfl.htm我的大学爱情观1、什么是大学爱情：大学是一个相对宽松，时间自由，自己支配的环境，也正因为这样，培植爱情之花最肥沃的土地。大学生恋爱一直是大学校园的热门话题，恋爱和学业也就自然成为了大学生在校期间面对的两个主要问题。恋爱关系处理得好、正确，健康，可以成为学习和事业的催化剂，使人学习努力、成绩上升；恋爱关系处理的不当，不健康，可能分散精力、浪费时间、情绪波动、成绩下降。因此，大学生的恋爱观必须树立在健康之上，并且树立正确的恋爱观是十分有必要的。因此我从下面几方面谈谈自己的对大学爱情观。2、什么是健康的爱情：1) 尊重对方，不显示对爱情的占有欲，不把爱情放第一位，不痴情过分；2) 理解对方，互相关心，互相支持，互相鼓励，并以对方的幸福为自己的满足; 3) 是彼此独立的前提下结合；3、什么是不健康的爱情：1)盲目的约会，忽视了学业;2)过于痴情，一味地要求对方表露爱的情怀，这种爱情常有病态的夸张;3)缺乏体贴怜爱之心，只表现自己强烈的占有欲;4)偏重于外表的追求;4、大学生处理两人的在爱情观需要三