Современные информационные технологии/ 1.Компьютерная
инженерия
Bulatova M.B.
Kostanay
State University named after A. Baitursynov, Kazakhstan
Modern wireless network technology.
This article reviews the latest standards in wireless
networking technologies. This article describes all the positive and negative
qualities of this option meet the challenges of packet data transmission over a
distance. Also find out the group of advanced wireless networking technologies
and identify the best standards in the group best suited for packet data
transmission on the "air" of the path.
Wireless network
technology
Choosing a wireless networking technology depends on
the needs of your company, its budget and plans for the future. Assume direct
connection objects in your enterprise copper or fiber- optic cable is not
possible (for example, due to lack of permission), or too expensive, or the
load on your network has increased to such an extent that its use of bandwidth
has reached a critical level, or manager marketing offers a central office
network to connect to networks spread over a large area shops. No matter how
difficult the situation was with communication in your company, wireless networking
technology will help you find the right solution.
Wireless network technologies can be divided into
three basic types: mobile communication, wireless communication link between
the buildings and inside them. We analyze the advantages and disadvantages of
each type, give information about the prices of adequate communication
equipment and consider the possible applications of wireless communication.
Mobile telephony
Wireless network technology for mobile users
widespread and inexpensive to implement. Examples of such technologies are
packet radio, packet digital data transmission over the cellular network
(Cellular Digital Packet Data - CDPD) and cellular -switched network. Although
these technologies provide the lowest data rate (compared to other wireless
networking technologies) but implement them operate on the system throughout
the world. Other technologies, such as enhanced specialized mobile radio
(Enhanced Specialized Mobile Radio - ESMR), personal communications service
(Personal Communications Services - PCS) and two-way satellite communications,
just begin to appear on the market.
Cellular
communication circuit switched
As CDPD, cellular-switched networks using the existing
analog cellular network. The difference is that in this case, instead of switching
the data packets using a conventional channel switching network. For data
transmission the user connects the cellular modem to the personal computer and
the cell phone supporting data transmission, and establishes switched
connection in the same way, as during the work with the old kind analog modem.
If you want to pass long files, the best choice -
cellular -switched networks; packet radio and CDPD are more suitable for
sending short messages. Cellular communication circuit switched - rather slow
form of communication. The data is transmitted at speeds of up to 14.4 kbit /
s, and only in certain areas to increase the service rate of 20 kbit / s. In
big cities and the distance from the base station transmission speed may be
reduced. Considered technology — the most available, after all more than 95% of
the territory of the USA are captured by cellular networks.
Wireless
communication between buildings.
For communications on small distances the network
administrator can sometimes consider systems of a wireless communication as
alternative to direct cable connections or leased lines. This alternative is
attractive for several reasons: such systems provide quite high speed of data
transmission, have good expansibility cheaper in operation. Technologies
wireless communication - such as the infrared laser, a narrow-band microwave
(MW) and broadband (using spread spectrum modulation) - provide data
transmission at speeds up to 155 Mbit / s. Costs of equipment for wireless
links are usually lower costs associated with the use of leased lines and much
less expensive than fiber- optic or coaxial cable.
Classification of
technologies
We will divide standards of wireless network
technologies conditionally into 2 groups:
• technologies of mobile communication;
• technologies of a wireless communication between
objects and within them.
Mobile communication technology.
This technology, which are widely used in cellular and
other mobile communications.
3G - Digital Packet technology that is used to
describe third-generation mobile telephony services providing access to video
content and broadband Internet for mobile devices. The first generation was
introduced analog cellular phones, second - digital cellular networks.
Uses standard W-CDMA (UMTS), CDMA2000,
TD-CDMA/TD-SCDMA, DECT, UWC-136.
Bluetooth - mobile communication technology, operating
on frequencies 2400-2483.5 MHz. These frequencies are not chosen randomly, they
are open and free of any licensing in most countries of the world. Used frequencies determine the possibilities
of Bluetooth data transmission. Channel width for Bluetooth devices is 723.2 kb
/ s in asynchronous mode (though even in this mode still remains to 57.6 kb / s
for simultaneous transmission in the opposite direction), or 433.9 kb / s in
fully synchronous mode.
Distance by which can be established Bluetooth
connection is small and ranges from 10 to 30 meters. Now work is underway to increase this distance, at least 100
meters.
The main feature
of Bluetooth is that different Bluetooth devices connect to each other
automatically, once they come within reach. The user has a headache on cables ,
drivers, or anything else , all he has to do is take care of what would
Bluetooth devices were close enough to each other, everything else should take
care of themselves Bluetooth devices and software .
Wireless
technology between objects and within them.
This technology, which are widely used for
communication between different buildings as well as within them.
Wi-Fi - a system of shorter-acting, usually
covering several hundred meters, that uses unlicensed frequency bands to
provide access to the network. Typically Wi-Fi is used by users to access their
own network, which may not be connected to the Internet. If WiMAX can be
compared to mobile communications , the Wi-Fi is more like a landline cordless
phone .
In Wi-Fi networks all user stations that want to
transmit information through an access point ( AP) are competing for the "
attention" of the latter. Such an approach may lead to a situation in
which the bond to the more remote stations will constantly end up in favor of
closer stations. This situation makes it difficult to use services such as
Voice over IP (VoIP), which are very dependent on a continuous connection.
Wi-Fi uses 802.11 families of specifications developed by the EEE for WLANs
(wireless LAN). There are exist a variety of specifications:
Conclusion.
This article was considering variety of advanced
wireless network technology. Was given a description, consider the
characteristics, especially the work as well as the usage environment.
Summarizing this article, we can say that today's time wireless networking
technologies have very good potential for development and are glad of superiority
over other network technologies. Note that due to the rapid development of
electronic technology wireless technology may soon become the best quality and
most importantly effective solution in networking.
Literature
1. http://www.ccc.ru
2 . http://www.3dnews.ru
3 . http://www.wimaxinfo.ru