通信专业英语自选课文.doc

Lesson 1 Internet of ThingsIn computing, the Internet of Things refers to a network of objects, such as household appliances. It is often a self-configuring wireless network. The concept of the internet of things is attributed to the original Auto-ID Center, founded in 1999 and based at the time in MIT1.The idea is as simple as its application is difficult. If all cans, books, shoes or parts of cars are equipped with minuscule identifying devices, daily life on our planet will undergo a transformation. Things like running out of stock or wasted products will no longer exist as we will know exactly what is being consumed on the other side of the globe. Theft will be a thing of the past as we will know where a product is at all times. The same applies to parcels lost in the post.If all objects of daily life, from yogurt to an airplane, are equipped with radio tags, they can be identified and managed by computers in the same way humans can.2 The next generation of Internet applications (IPv6 protocol) would be able to identify more objects than IPv4, which is currently in use. This system would therefore be able to instantaneously identify any kind of object.3The Internet of objects should encode 50 to 100,000 billion objects and follow the movement of those objects. Every human being is surrounded by 1,000 to 5,000 objects.4Alcatel-Lucent touchatag 5 service and Violets Mirror gadget provide a pragmatic consumer oriented approach to the Internet of Things by which anyone can easily link real world items to the online world using RFID tags (and QR Codes in case of touchatag).Universal addressability of dumb thingsAn alternative view, from the world of the Semantic Web 6 focuses instead on making all things (not just those electronic, smart, or RFID-enabled) addressable by the existing naming protocols, such as URI. The objects themselves do not converse, but they may now be referred to by other agents, such as powerful centralised servers acting for their human owners.Obviously these two approaches converge as more objects become progressively addressable and more intelligent. This is unlikely to happen in any situation short of spime, and the two views have significantly different implications in the interim. In particular, the universal addressability approach rapidly includes things that cannot have communication behaviors of their own, such as abstract data documents.Trends, CharacteristicsThe Internet of Things will likely be a non deterministic and open network (cyberspace?) in which auto-organized or intelligent entities (Web services, SOA components), virtual objects (avatars) will be interoperable and able to act independently (pursuing their own objectives or shared ones) depending on the context, circumstances or environments. It will host Ambient intelligence (built upon Ubiquitous computing).Real life VS Model-driven architectureIt will also likely be event driven7, bottom-up made (based on the context of processes and operations, in real-time) and will consider any subsidiary level (see also: Event-driven architecture). Therefore, model driven and functional approaches will coexist with new ones able to treat exceptions and unusual evolution of processes (Multi-agent systems, B-ADSc, etc.). Actually, in this internet, the meaning of an event will not necessary be based on, either a deterministic or syntactic model but will be based on the context of the event itself: this will also be a Semantic Web. Consequently, it will not necessarily need common standards that would not be able to address every context or use: some actors (services, components, avatars) will accordingly be self-referenced and, if ever needed, adaptive to existing common standards (predicting everything would be no more than defining a global finality for everything that is just not possible with any of the current top-down approaches and standardizations).Chaotic or complex system?In semi-open or closed loops (i.e. value chains, whenever a global finality can be settled) it will therefore be considered and studied as a Complex system due to the huge amount of different and various links, interactions, between various, autonomous and different actors and due to its capacity to integrate new actors. At the overall stage (full open loop) it will likely be seen as a chaotic environment (since systems have always finality).Time considerationsIn this Internet of Things, made of billions of parallel and simultaneous events, time will no more be used as a common and linear dimension8 but will depend on each entity (object, process, information system, etc.). This Internet of Things will be accordingly based on massive parallel IT systems (Parallel computing).Notes1.Dodson 2003. The Auto-ID Center was replaced by the Auto-ID Labs in October 2003. More precisely, EPCglobal was formed as the successor organization to the Auto-ID Center, while its sister organization Auto-ID Labs manages and funds research on the EPC technology. 2. Commission of the European Communities (2009-06-18). Internet of Things An action plan for Europe (pdf). http:/ec.europa.eu/information_society/policy/rfid/documents/commiot2009.pdf. 3. Waldner 2008. 4. Waldner 2007 5. 6. Dan Brickley et al., c. 2001 7. Philippe GAUTIER, RFID et acquisition de donnes vnementielles: retours dexprience chez Bndicta, pages 94 96, Systmes dInformation et Management - revue trimestrielle N2 Vol. 12, 2007, ISSN 1260-4984 / ISBN 9782747212908, ditions ESKA. 1 8. Janusz Bucki, Lorganisation et le temps (in French) Lesson 2 Wireless NetworkWireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between nodes is implemented without the use of wires.1 Wireless telecommunications networks are generally implemented with some type of remote information transmission system that uses electromagnetic waves, such as radio waves, for the carrier and this implementation usually takes place at the physical level or layer of the network.2TypesWireless PANWireless Personal Area Networks (WPANs) interconnect devices within a relatively small area, generally within reach of a person. For example, Bluetooth provides a WPAN for interconnecting a headset to a laptop. ZigBee also supports WPAN applications.3 Wi-Fi: Wi-Fi is increasingly used as a synonym for 802.11 WLANs, although it is technically a certification of interoperability between 802.11 devices. Fixed Wireless Data: This implements point to point links between computers or networks at two locations, often using dedicated microwave or laser beams over line of sight paths. It is often used in cities to connect networks in two or more buildings without physically wiring the buildings together. Wireless MANWireless Metropolitan area networks are a type of wireless network that connects several Wireless LANs. WiMAX is the term used to refer to wireless MANs and is covered in IEEE 802.16d/802.16e. Wireless WANWireless Wide Area Networks are wireless networks that typically cover large outdoor areas. These networks can be used to connect branch offices of business or as a public internet access system. They are usually deployed on the 2.4GHz band. A typical system is as per the one deployed by Gaiacom Wireless Networks contains base station gateways, access points and wireless bridging relays. Other configurations are mesh systems where each access point acts as a relay also. When combined with renewable energy systems such as photo-voltaic solar panels or wind systems they can be stand alone systems.Mobile devices networksWith the development of smart phones, cellular telephone networks routinely carry data in addition to telephone conversations: Global System for Mobile Communications (GSM): The GSM network is divided into three major systems: the switching system, the base station system, and the operation and support system. The cell phone connects to the base system station which then connects to the operation and support station; it then connects to the switching station where the call is transferred to where it needs to go. GSM is the most common standard and is used for a majority of cell phones.4 Personal Communications Service (PCS): PCS is a radio band that can be used by mobile phones in North America and South Asia. Sprint happened to be the first service to set up a PCS. D-AMPS: Digital Advanced Mobile Phone Service, an upgraded version of AMPS, is being phased out due to advancement in technology. The newer GSM networks are replacing the older system. See also mobile telecommunications.UsesWireless networks have had a significant impact on the world as far back as World War II. Through the use of wireless networks, information could be sent overseas or behind enemy lines easily, efficiently and more reliably. Since then, wireless networks have continued to develop and their uses have grown significantly. Cellular phones are part of huge wireless network systems. People use these phones daily to communicate with one another. Sending information overseas is possible through wireless network systems using satellites and other signals to communicate across the world. Emergency services such as the police department utilize wireless networks to communicate important information quickly. People and businesses use wireless networks to send and share data quickly whether it be in a small office building or across the world.5Another important use for wireless networks is as an inexpensive and rapid way to be connected to the Internet in countries and regions where the telecom infrastructure is poor or there is a lack of resources, as in most developing countries.Compatibility issues also arise when dealing with wireless networks. Different components not made by the same company may not work together, or might require extra work to fix these issues. Wireless networks are typically slower than those that are directly connected through an Ethernet cable.A wireless network is more vulnerable, because anyone can try to break into a network broadcasting a signal. Many networks offer WEP - Wired Equivalent Privacy - security systems which have been found to be vulnerable to intrusion. Though WEP does block some intruders, the security problems have caused some businesses to stick with wired networks until security can be improved. Another type of security for wireless networks is WPA - Wi-Fi Protected Access. WPA provides more security to wireless networks than a WEP security set up. The use of firewalls will help with security breaches which can help to fix security problems in some wireless networks that are more vulnerable.Environmental concerns and health hazardIn recent times, there have been increased concerns about the safety of wireless communications, despite little evidence of health risks so far.6 The president of Lakehead University refused to agree to installation of a wireless network citing a California Public Utilities Commission study which said that the possible risk of tumors and other diseases due to exposure to electromagnetic fields (EMFs) needs to be further investigated.7References1. Overview of Wireless Communications. . /us/catalogue/catalogue.asp?isbn=0521837162&ss=exc. Retrieved 2008-02-08. 2. Getting to Know Wireless Networks and Technology. . /articles/printerfriendly.aspx?p=98132. Retrieved 2008-02-08. 3. Wireless Network Industry Report. /resources/downloads/wireless_industry_report_2007.html. Retrieved 2008-07-08. 4. Global System for Mobile Communication (GSM). . /online/tutorials/gsm/topic03.html. Retrieved 2008-02-08. 5. History of Wireless. . /wireless/history.html. Retrieved 2008-02-08. 6. Wi-Fi: Children at risk from electronic smog. news.independent.co.uk. http:/news.independent.co.uk/uk/health_medical/article2472133.ece. Retrieved 2008-02-08. 7. Canadian university says no to WiFi over health concerns. . /news.ars/post/20060222-6235.html. Retrieved 2008-02-08. Lesson 3 Wi-FiWi-Fi (pronounced /wafa/) is a trademark of the Wi-Fi Alliance that may be used with certified products that belong to a class of wireless local area network (WLAN) devices based on the IEEE 802.11 standards. Because of the close relationship with its underlying standard, the term Wi-Fi is often used as a synonym for IEEE 802.11 technology.12The Wi-Fi Alliance is a global, non-profit association of companies that promotes WLAN technology and certifies products if they conform to certain standards of interoperability. Not every IEEE 802.11-compliant device is submitted for certification to the Wi-Fi Alliance, sometimes because of costs associated with the certification process and the lack of the Wi-Fi logo does not imply a device is incompatible with Wi-Fi devices.Today, an IEEE 802.11 device is installed in many personal computers, video game consoles, smartphones, printers, and other peripherals, and virtually all laptop or palm-sized computers.UsesInternet accessA Wi-Fi enabled device such as a personal computer, video game console, mobile phone, MP3 player or personal digital assistant can connect to the Internet when within range of a wireless network connected to the Internet. The coverage of one or more interconnected access points called a hotspot can comprise an area as small as a few rooms or as large as many square miles covered by a group of access points with overlapping coverage. Wi-Fi technology has been used in wireless mesh networks, for example, in London.3In addition to private use in homes and offices, Wi-Fi can provide public access at Wi-Fi hotspots provided either free of charge or to subscribers to various commercial services. Organizations and businesses such as airports, hotels and restaurants often provide free hotspots to attract or assist clients. Enthusiasts or authorities who wish to provide services or even to promote business in selected areas sometimes provide free Wi-Fi access. As of 2008update there are more than 300 metropolitan-wide Wi-Fi (Muni-Fi) projects in progress.4 There were 879 Wi-Fi based Wireless Internet service providers in the Czech Republic as of May 2008.56Routers that incorporate a digital subscriber line modem or a cable modem and a Wi-Fi access point, often set up in homes and other premises, provide Internet-access and internetworking to all devices connected (wirelessly or by cable) to them. One can also connect Wi-Fi devices in ad hoc mode for client-to-client connections without a router. Wi-Fi also enables places that would traditionally not have network to be connected, for example bathrooms, kitchens and garden sheds.Airport Wi-FiIn September of 2003, Pittsburgh International Airport became the first airport to allow and offer free Wi-Fi throughout its terminal.7 It is now commonplace.City-wide Wi-FiIn the early 2000s, many cities around the world announced plans for a city wide Wi-Fi network. This proved to be much more difficult than their promoters initially envisioned with the result that most of these projects were either canceled or placed on indefinite hold. A few were successful, for example in 2005, Sunnyvale, California became the first city in the United States to offer city wide free Wi-Fi.8 Few of the Municipal Wi-Fi firms have now entered into the field of Smart grid networks.9Campus-wide Wi-FiCarnegie Mellon University built the first wireless Internet network in the world at their Pittsburgh campus in 1994, long before the Wi-Fi standard was adopted.10Direct computer-to-computer communicationsWi-Fi also allows communications directly from one computer to another without the involvement of an access point. This is called the ad-hoc mode of Wi-Fi transmission. This wireless ad-hoc network mode has proven popular with multiplayer handheld game consoles, such as the Nintendo DS, digital cameras, and other consumer electronics devices. A similar method is a new specification called Wi-Fi Direct which is promoted by the Wi-Fi Alliance for file transfers and media sharing through a new discovery and security methodology.11Future directionsAs of 2010update Wi-Fi technology had spread widely within business and industrial sites. In business environments, just like other environments, increasing the number of Wi-Fi access-points provides redundancy, support for fast roaming and increased overall network-capacity by using more channels or by defining smaller cells. Wi-Fi enables wireless voice-applications (VoWLAN or WVOIP). Over the years, Wi-Fi implementations have moved toward thin access-points, with more of the network intelligence housed in a centralized network appliance, relegating individual access-points to the role of mere dumb radios. Outdoor applications may utilize true mesh topologies. As of 2007 Wi-Fi installations can provide a secure computer networking gateway, firewall, DHCP server, intrusion detection system, and other functions.HistoryWi-Fi uses both single-carrier direct-sequence spread spectrum radio technology (part of the larger family of spread spectrum systems) and multi-carrier orthogonal frequency-division multiplexing (OFDM) radio technology. The deregulation of certain radio-frequencies for unlicensed spread spectrum deployment enabled the development of Wi-Fi products, its onetime competitor HomeRF, Bluetooth, and many other products such as some types of cordless telephones.Unlicensed spread spectrum was first made available in the US by the FCC in rules adopted on May 9, 198512