Generations of mobile communication system
16:05:00
Generations of mobile
communication system
learn the history of mobile communication
(a)
First Generation
(IG) System: These are voice oriented analog cellular and cordless
telephones. These systems use two separate frequency bands for forward (from
base station to mobile) and reverse (from mobile to base station) links. Such a
system is referred to as frequency division duplex (FDD) scheme. The typical
allocated overall band in each direction was25 KHz. The dominant spectra of
operation for these systems were the 800 and 900 MHz bands. All the first
generation (IG) system use analog frequency modulation
for which the transmission power requirement depends on the transmission
bandwidth.
In these systems, the vision of universal operation was not
envisaged. As a result, most of the systems were localized as most countries
developed their own standards. Also the first generation system did not cater
for the needs of all four kinds of information i.e. voice, picture, data and
text.
The
first generation system developed in different countries includes the
following:
(i)
Advanced mobile phone system (AMPS) in USA
(ii)
Total access communication system (TACS) in Europe.
(iii)
Nippon telephone and telegraphs (NTT) in Japan
(iv) Radicom in France.
(iv)
Nordic mobile telephone (NMT) in Europe
(v)
Extended total access communication systems (ETACS) in
UK. etc
(B) Second
Generation (2G) Systems: These are voice and data oriented digital systems.
The early ones use time division multiple access (TDMA) technology while some
recent standard use the code division multiple access (CDMA). Like the first
generation analog system, the 2G systems are all FDD and operate in the
800-900MHz band. There are four major standards in 2G. These include the
following
(i)
The GSM
(ii)
The North America Interim Standard
(iii)
The Japanese Digital Cellular (JDC)
(iv)
The North America Interim standard 95 (IS-95)
The
carrier spacing of the IS-54 and JDC is the same as the first generation (IG)
that is 25 KHz. The GSM use a separation of 200 kHz while the IS-95 uses 1,250
KHz. The GSM has a channel bit rate of 270Kbp compared to 1,228.8kbps for the IS-95
and 2Mbps for CDMA-2000 systems. The 2G system uses digital modulation. Like
the first generation, the second generation did not cater for international
standard.
(B) Third
Generation (3G) System: The migration to the third generation was
necessitated by the need to develop an international standard that combines and
gradually replaces the 2G systems.
At
the same time, 3G systems were expected to increase the quality of voice,
capacity of the network and the data of mobile data services.
The
dominant technology for the 3G is the W-CDMA.
Here
technologies like ATM, etc were adopted in a larger scale.
Wireless
multimedia networking including audio, video, text and data information were
incorporated.
(D) Fourth
Generation (4G) systems: Research on the next generation of
mobile communication i.e. 4G is underway. The concepts of 4G system would be
user driven, user controlled service and context aware applications.
The
reconfigurable technology would be another feature of 4G systems. This refers to
the software redefinition and adaptation of every element with each lager of
the communication chain. In user controlled services, the user will have the
freedom and flexibility to select any desired service. The user can also select
the devices for context aware applications. Such application means that the
behavior of application adapts itself to user context damage like user profile
environment, network capabilities, etc.
The
key items of 4G are: (i) High frequency reuse (ii) Digital to analog conversion
at higher data rates (iii) Multiuser detection (iv) Voice over multiloop
networks (v) security (vi) seamless roaming and seamless transfer of services.
Possible
application include: (i) Full motion, Video and home entertainment system (ii) Advance
location finding systems (iii) Broadband wireless to support data rate up to
100Mbps.
The
under-laying technology of 4G is the new radio technology consisting of (i)
Orthogonal FDM with multimedia streaming application to handle multipart fading
well. (ii) Frequency hopps WCDMN technology for scalable networks and better
scheduling call admission control.
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