History of Mobile / Cell Phone
an overview information or tutorial about the history of the mobile phone
or cell phone and the associated cellular telecommunications systems.
The development and history of the mobile phone has seen a
tremendous number of changes since the first cell phones were introduced. It was
only at the beginning of the 1980s when mobile phone technology started to be
deployed commercially. Since then there have been many new cell phone or mobile
phone systems introduced, and many improvements have been made in this form of
radio communications technology. The mobile phones themselves as well as the
associated equipment including base stations and the other network equipment and
cellular technology has become much cheaper and far smaller.
One of the major changes is the level of market penetration
that has been achieved. Cellular technology has enabled many people to have
phones where it would not otherwise be possible. In many countries there are
more mobile phone accounts than people, i.e. many people have more than one
account, possibly one for private use and one for work. In this way cellular
technology has enabled market penetration to become more than 100%.
With the development of cellular technology, mobile phones
now have many more facilities and capabilities than the first ones to be sold.
Mobile phone history will show a steady increase in the capabilities of these
phones.
Mobile phone history overview
The phones themselves have undergone many changes during
their history. Cellular technology that has been used has improved dramatically.
The first systems to be launched were based on analogue technology. The early
phones were very large and could certainly not be placed in a pocket like the
phones of today.
The first generation (1G) phone systems as they are now known
were overtaken in the early 1990s by the first digital systems.
The high levels of use and limited frequency allocation meant
that greater spectrum use efficiency was needed. Accordingly the next or
second-generation (2G) phone systems were introduced to meet this need.
As the usage of phones increased and people became more
mobile, new possibilities emerged for using the phones for data transfer. They
could be used to download information from the Internet, or to send video. The
first stage in this migration was to provide a medium speed data transfer
capability. These systems were accordingly known as 2.5G.
However the ultimate aim was to provide a relatively
high-speed data transfer capability. These full third generation (3G) systems
took longer to develop and roll-out than had been originally anticipated as a
result of higher development costs and a downturn in the global economy. However
they are able to provide a significant improvement in capability over the 2.5 G
systems
Analogue Systems
There was an enormous variety of first generation systems
that were introduced. Much of the early development of cellular systems had been
undertaken in the USA, but the first fully commercial system to be launched was
the Nordic Mobile Telephone (NMT) system. Shortly after this a system known as
the Advanced Mobile Phone System (AMPS) was launched commercially. This was
developed primarily by Bell and was introduced in the USA although many other
countries used this system later. A further system known as Total Access
Communication System (TACS) developed by Motorola was introduced in the UK and
many other countries.
These were the main systems that were developed, although
around the globe many variants were developed to suit the needs of the
individual countries.
Although there were differences in the specifications of the
systems, they were all very similar in concept. The voice information was
carried on a frequency-modulated carrier. A control channel was also used to
enable the mobile to be routed to a suitable vacant channel. The channel spacing
for each system was different. NMT used a 12.5 kHz channel spacing, AMPS, a 30
kHz spacing and TACS a 25 kHz spacing. A later development of AMPS called NAMPS
or narrowband AMPS used a 10 kHz channel spacing to conserve spectrum.
Digital Systems
The analogue systems were very successful, but their very
success started to show some of their shortcomings. The main one was the
inefficient way in which they sued the spectrum. With the growth rates that were
being seen, there was insufficient spectrum to support the quality of service
that was required. By converting to a digital system, considerable savings could
be made. A number of systems arose from this initiative. These second-generation
systems as they were termed, started to be deployed in the early 1990s and their
history is just as remarkable.
The system that was developed in Europe was the result of 26
telecommunications companies working together. Work actually started in 1982,
and the roll-out commenced in 1991. The system known by the letters GSM was
originally called Groupe Speciale Mobile but this was later changed to Global
System for Mobile communications in view of the wide involvement in its
development. It used time division multiple access (TDMA) to allow up to eight
users to use each of the channels that are spaced 200 kHz apart. The basic
system used frequencies in the 900 MHz band, but other bands in the 1800 and
1900 MHz (USA) bands were added. New bands in the 850 MHz region were also
added.
In the USA a system specially designed to operate alongside
their AMPS system was devised. The system was known under a variety of names
including Digital AMPS or DAMPS, and US Digital Cellular (USDC), although it is
normally known just as TDMA today as it relies on TDMA technology. The system
was originally defined under standard number IS-54, although this was later
updated to IS-136 and it uses a 30 kHz channel spacing to make it compatible
with the existing AMPS systems in operation.
Another development in the USA from Qualcomm took a major
leap in technology. It introduced a totally new concept for multiple access.
Based on direct sequence spread spectrum (DSSS) that had previously been used
for military transmissions, it used a multiple access system known as code
division multiple access (CDMA). The new system offered far greater levels of
spectrum efficiency although it required more complicated circuitry in the
handsets. The system was defined under standard IS-95 and each carrier had a
bandwidth of 1.25 MHz, although many users could use the same channel. The
specification was updated from IS-95A to IS-95B. It was this later standard that
went under the trade name cdmaOne.
2.5G
Once the second-generation systems became established it soon
became apparent that the limited data capabilities of some of the 2G systems
were a significant disadvantage. Many applications for data transfer with the
increased use of the Internet and laptop computers were seen. Even though the
third generation systems were on the horizon, developments were needed to
provide a service before they entered the market. One of the first was the
General Packet Radio Service (GPRS) development for the GSM system. Its approach
centred on the use of packet data. Up until this time all circuits had been
dedicated to a given user in an approach known as circuit switched, i.e. where a
complete circuit is switched for a given user. This was inefficient when a
channel was only carrying data for a small percentage of the time. The new
packet switched approach routed individual packets of data from the transmitter
to the receiver allowing the same circuit to be used by different users. This
enabled circuits to be used more efficiently and charges to be metered according
to the data transferred.
Further data rate improvements were made using a system known
as EDGE (Enhanced data Rates for GSM Evolution). This basically took the GPRS
system and added a new modulation scheme, 8PSK, to enable a much higher data
rate to be achieved. Whilst the symbol rate remained the same at 270.833 samples
per second, each symbol carried three bits instead of one.
Whilst GPRS and EDGE were applied to GSM networks,
enhancements were also applied to the CDMA system that originated in the USA.
Here an evolutionary path from 2G through 2.5G to 3G was created. The
intermediate stage was development of cdmaOne was CDMA2000 1X. This scheme
retained the 1.25 MHz bandwidth of IS95 / cdmaOne, but by adding further
channels enabled data transfer rates of 307 kbps to be achieved, thereby
doubling the capacity of IS95B.
Third Generation
Although technologies such as GPRS, EDGE and CDMA2000 1X were
able to deliver significantly higher data rates than their predecessors, the
final migration was to the full 3G service. There were three main technologies.
From Europe there was the UMTS (Universal Mobile
Telecommunications System) using wideband CDMA (W-CDMA). This system used a 5
MHz channel spacing and provided data rates of up to 2 Mbps.
Then there were the CDMA2000 evolutions. The first to be
launched was CDMA2000 1xEV-DO. Here the letters EV-DO stood for Evolution Data
Only. The idea for this system was that many of the applications would only need
a data connection, as in the case of a data card for use in a PC to provide a
wireless Internet capability over a mobile phone system. For any applications
needing both data and voice a standard 1X channel would be required in addition.
Although using CDMA technology, the EV-DO system also used TDMA technology as
well to provide the throughput whilst still maintaining backward compatibility
with IS95 (cdmaOne) and CDMA2000 1X.
The next evolution of the CDMA2000 family was CDMA2000
1xEV-DV. This was an evolution of the 1X system, and totally distinct from
1xEV-DO and it provided a full data and voice capability. Again this system was
able to provide backward compatibility with IS95 (cdmaOne) and CDMA2000 1X
whilst still being able to provide a data capability of 3.1 Mbps in the forward
direction.
These major two players in the 3G scene both used what is
called frequency division duplex (FDD) where the forward and reverse links used
different frequencies. Within UMTS there is a specification covering a time
division duplex (TDD) system where the forward and reverse links used the same
frequency but use different timeslots. However the TDD version is not being
deployed for some time.
A third 3G system that originated in China uses TDD. Known as
time division synchronous CDMA (TD-SCDMA) this system used a 1.6 MHz channel
spacing and was thought to be likely to take a significant portion of the
Chinese market along with those in neighbouring countries
Summary
The history of the mobile phone has taken place over a
comparatively short time, but cellular technology has been seen to develop at a
tremendous rate. As a form of two way radio communications, cellular technology
has outstripped every other form of radio communications technology. It took
just over 20 years to migrate from the first analogue systems to the 3G systems
capable of high data rate transfers. Now development of cellular technology is
looking at 4G standards capable of data rates of over 100 Mbps. With many
developments still taking place, the outlook for cellular technology looks as if
it will be particularly interesting.
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