Recent Trends in Mobile Technology.doc
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This article is presented by:K.S.S.KASYAP
Recent Trends in Mobile Technology
Introduction to wireless technology
Mobile Technology is exactly the word which implies- the technology which is portable.
• In 1887 the scientist named Henrich Heartz, concluded that we can propogate an EM wave in space with velocity equal to light (300M m/sec).
• Later in 1889, the above theory was developed by scientist named Marconio by transmitting the EM wave around 5km.This was how the wireless technology emerged.
• During the early 1940s, Motorola developed a two-way radio, named Walkie-Talkie.
• Hereby, the first generation (1G) of mobile communications was developed in the late 1970s. It was primarily used for voice transfer.
• In the early 1990s, second generation (2G) systems came into existence and was further developed to 2.5G, which includes GSM, TDMA and CDMA and now we are in (3G)the third generation.
Second Generation (2G):
Types of technologies:
FDMA Frequency Division Multiple Accesses:
Frequency division is the original multiple access technique. Currently,
most legacies. Public safety wireless networks use FDMA to improve spectrum efficiency.
FDMA is used Through out the commercial wireless industry. Legacy commercial
Telecommunication networks.(Analog networks based on Advanced Mobile Phone Service
[AMPS] and Total Access Communications System [TACS] standards) are built on a backbone
of cellular base stations, Using the FDMA technology.
How it Works:
FDMA systems separate a client's large frequency band into several smaller individual
Bands/channels. Each channel has the ability to support a user. Guard bands are used to separate
Channels to prevent interference. They are used to isolate channels from adjacent-channel
Interference. : FDMA permits only one user per channel because it allows the user to use the channel
100 percent of the time. Therefore, only the frequency “dimension” is used to define channels.
When the FDMA technique is employed, each user is assigned a discrete slice of the
radio frequency (RF) spectrum, a “channel” of spectrum space that will vary in size depending
on the type of signal being transmitted. In a given amount of spectrum space, the user is granted
access to a small sliver of the overall allocation. As long as the user is engaged in
“conversation,” no other user can access the same spectrum space. An example of this type of
access is use of the spectrum by commercial radio broadcasters. In the commercial radio
broadcast bands, 535–1705 kHz for amplitude modulation (AM) and 88–108 megahertz (MHz)
for frequency modulation (FM), each local broadcast station (user) is assigned a specific slice of
spectrum within the frequency band allocated for that purpose. As long as the station broadcasts,
no other radio station in the same area can use that radio frequency bandwidth to send a signal.
Another broadcast station can use that same bandwidth only when the distance between the
Stations is sufficient to reduce the risk of interference.