From Wikipedia, the free encyclopedia.
DEFINITION:
Wi-Fi, short for Wireless Fidelity, is a term for devices that can connect to wireless local area network (WLAN) based on IEEE 802.11. A device, even if it conforms to these specifications can not use the official logo Wi-Fi if it has not passed the certification procedures established. The presence of Wi-Fi logo on a device should therefore ensure interoperability with other certified devices.
Specifications:
-Nets Wi-Fi infrastructure are relatively inexpensive and fast activation and allow the creation of flexible systems for the transmission of data.
The source of broadband connectivity can be wired (ADSL or HDSL), or via satellite. The disadvantage of satellite is the waiting time before it starts sending packets, much larger when compared to the few hundredths of a second needed for a DSL connection.
Since the source of bandwidth, you can expand your network through Wi-Fi.
The installation of satellite dishes is simple. These small dishes.
type of coverage covers of such masts are basically of two types:
1) Omnidirectional: typically used in private areas and relatively small. Or with larger radii, we can cover public areas (such as airports, shopping centers etc.).
2) Directions: Use
to cover distances in terms of kilometers, and are useful just to bring broadband in areas uncovered by the wired network.
In the absence of barriers in the crow flies, the access point's signal covers much greater distances.
with an access point with broadband, you can cover up to a theoretical range of 300 meters (domestic).
In the presence of walls, trees or other barriers to the signal decays to 150 meters. However, directional antennas with 2-3 from the cost still lower than the coverage of the access point goes up to 1 km. The signal of directional antennas, as opposed to the access point, it is powerful enough to maintain the same coverage radius of 1 km, also unchanged in the presence of barriers in the air. A good network is extensive (many access points, antennas that repeat the signal) and is standardized.
Protocols
Most software uses open-source, public or its set-up configuration under open source license.
Protocol HiperLan works at frequencies of 2.4 GHz and 5.4 GHz (in the case of HiperLan 2), using other software such as protocol and covers a radius of 2-3 km from the antenna with transmitter power of ' order of tenths of a watt (such as those antenna of a mobile phone). In a subsequent series of raises that put in a set number of antennas HiperLan are covered up to 20 km and 11 actual theorists.
Location of Access Points: Access
wi-fi is available in airports, railway stations, internet cafes around the world. In Europe there is a widespread network of "Totem Freestation.
There are also cities, groups or individuals who have built Wi-Fi networks by adopting common rules to ensure interoperability .
the wireless community network is a worldwide list of available wi-fi networks.
Finally, in the process of rapidly expanding the initiative FON, which is a great community wi-fi world that allows access to the internet and the members of that community (traveling), than to casual users (minimum payment)
The Wi-Fi networks and civic
Recently, some Italian provinces and public administrations have launched projects to create civic networks with Wi-Fi. goals scored are in public ownership, while managing assigned to dealer change.A private networks linking the government of the local area and provide widespread access to broadband in those areas where national operators do not want to invest because of high costs ( es. mountain areas).
forward:
For the lowest cost technology, wi-fi is the leading solution for the digital divide, which excludes many people from access to broadband.
Wi-fi has been used for years all over the world to bring fast connectivity in remote areas and small towns. In the U.S., has also proven integration with mobile phones where the wi-fi should replace the old antenna GSM / GPRS / UMTS, with a new network that can give hope to the speed and video telephony services.
There is no prospect of integrating fixed and mobile telephony in a single device that functions with the same number of fixed / mobile within 300 meters from home and more like a normal phone.
In many argue that the devices will replace Wi-Fi phones and GSM networks.
are obstacles to this:
• The inability of the roaming and authentication options
• the limited frequency spectrum available and the range of a Wi-Fi.
Many operators are starting to sell mobile devices to access the Internet, wireless cards that connect mobile phones and wi-fi handsets to benefit from both systems. It is expected that future wireless systems are operating normally between a plurality of radio systems.
Pros / Cons of wi-fi
PRO
1. Many networks can provide data encryption and roaming being able to move from the coverage of an access point to another without a loss of Internet connection, outside the range that defines a hot spot.
2. Unlike the phone, the existence of a standard certificate guarantees INTEROPERABILITY 'between network equipment and even abroad, without the cost of wiring for a quick and easy installation and subsequent expansion of the network.
3. The presence of several manufacturers have created a very significant competition LOWERING initial price of this technology.
v 1. The long latency of Wi-fi is slightly higher than those based on cable
2. SERVICE to the home of noise on the signal may be discontinuous.
3. According to recent studies, established scientists say that radiation is harmful Wi-Fi our body.
Privacy
Most wi-fi does not offer protection from unauthorized use. This has led to the proliferation in urban areas of a large number of private networks freely accessible. This
cause safety problems in case of any sensitive or personal data transmitted (credit card numbers, telephone numbers, bank details).
But you can use the systems developed was WEP, Wired Equivalent Protocol but suffers from intrinsic problems that make it useless. To overcome the problems of WEP were invented WPA and WPA2 security levels that offer more.
Obviously the best method of protection is to contain the propagation of radio waves which are not necessary. This can be implemented via software by limiting the transmission power or by using antennas with a radiation lobe directed only to areas where connectivity is required. Alleged damage to health
There are investigations, including the BBC's Panorama, which investigates allegations of some scientists that electromagnetic smog which could give rise to long-term damage to health. In particular it should be noted that the frequencies of the Wi-Fi are the same (though with much less power) used by microwave ovens and allow the cooking of food (2450 MHz). In addition to this thermal effect, the engineers point to the possibility of further biological effect is not related to the temperature increase but still significant.
According to some, during this investigation were not provided precise figures and technical details. The majority of respondents would be deployed only technical side of the alarm and the only one who instead gave a version would have been reassuring regarding accused of conniving with the industry (as in fact he has worked for some of them ).
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