History of Mobile Telecommunication Systems

1.2.1 From 1G to 3G
Mobile telecommunication systems were first introduced in the early 1980s. The first
generation (1G) systems used analogue communication techniques, which were similar
to those used by a traditional analogue radio. The individual cells were large and the
systems did not use the available radio spectrum efficiently, so their capacity was by
today’s standards very small. The mobile devices were large and expensive and were
marketed almost exclusively at business users.
Mobile telecommunications took off as a consumer product with the introduction of
second generation (2G) systems in the early 1990s. These systems were the first to use
digital technology, which permitted a more efficient use of the radio spectrum and the
introduction of smaller, cheaper devices. They were originally designed just for voice,
but were later enhanced to support instant messaging through the Short Message Service
(SMS). The most popular 2G system was the Global System for Mobile Communications
(GSM), which was originally designed as a pan-European technology, but which later became popular throughout the world. Also notable was IS-95 , otherwise known
as cdmaOne, which was designed by Qualcomm, and which became the dominant 2G
system in the USA.
The success of 2G communication systems came at the same time as the early growth
of the internet. It was natural for network operators to bring the two concepts together, by
allowing users to download data onto mobile devices. To do this, so-called 2.5G systems
built on the original ideas from 2G, by introducing the core network’s packet switched
domain and by modifying the air interface so that it could handle data as well as voice.
The General Packet Radio Service (GPRS) incorporated these techniques into GSM, while
IS-95 was developed into a system known as IS-95B.
At the same time, the data rates available over the internet were progressively increasing.
To mirror this, designers first improved the performance of 2G systems using techniques such
as Enhanced Data Rates for GSM Evolution (EDGE) and then introduced more powerful
third generation (3G) systems in the years after 2000. 3G systems use different techniques
for radio transmission and reception from their 2G predecessors, which increases the peak
data rates that they can handle and which makes still more efficient use of the available
radio spectrum.
Unfortunately, early 3G systems were excessively hyped and their performance did
not at first live up to expectations. Because of this, 3G only took off properly after the
introduction of 3.5G systems around 2005. In these systems, the air interface includes
extra optimizations that are targeted at data applications, which increase the average rate
at which a user can upload or download information, at the expense of introducing greater
variability into the data rate and the arrival time.

1.2.2 Third Generation Systems
The world’s dominant 3G system is the Universal Mobile Telecommunication System
(UMTS). UMTS was developed from GSM by completely changing the technology used
on the air interface, while keeping the core network almost unchanged. The system was
later enhanced for data applications, by introducing the 3.5G technologies of high speed
downlink packet access (HSDPA) and high speed uplink packet access (HSUPA), which
are collectively known as high speed packet access (HSPA).
The UMTS air interface has two slightly different implementations. Wideband code
division multiple access (WCDMA) is the version that was originally specified, and the
one that is currently used through most of the world. Time division synchronous code
division multiple access (TD-SCDMA) is a derivative of WCDMA, which is also known
as the low chip rate option of UMTS TDD mode. TD-SCDMA was developed in China,
to minimize the country’s dependence on Western technology and on royalty payments to
Western companies. It is deployed by one of China’s three 3G operators, China Mobile.
There are two main technical differences between these implementations. Firstly,
WCDMA usually segregates the base stations’ and mobiles’ transmissions by means
of frequency division duplex, while TD-SCDMA uses time division duplex. Secondly,
WCDMA uses a wide bandwidth of 5MHz, while TD-SCDMA uses a smaller value of
1.6 MHz.
cdma2000 was developed from IS-95 and is mainly used in North America. The original
3G technology was known as cdma2000 1x radio transmission technology (1xRTT). It was subsequently enhanced to a 3.5G system with two alternative names, cdma2000 high rate
packet data (HRPD) or evolution data optimized (EV-DO), which uses similar techniques
to high speed packet access. The specifications for IS-95 and cdma2000 are produced by
a similar collaboration to 3GPP, which is known as the Third Generation Partnership
Project 2 (3GPP2) .
There are three main technical differences between the air interfaces of cdma2000
and UMTS. Firstly, cdma2000 uses a bandwidth of 1.25 MHz. Secondly, cdma2000 is
backwards compatible with IS-95, in the sense that IS-95 mobiles can communicate with
cdma2000 base stations and vice versa, whereas UMTS is not backwards compatible
with GSM. Thirdly, cdma2000 segregates voice and optimized data onto different carrier
frequencies, whereas UMTS allows them to share the same one. The first two issues
hindered the penetration of WCDMA into the North American market, where there were
few allocations of bandwidths as wide as 5MHz and there were a large number of legacy
IS-95 devices.
The final 3G technology is Worldwide Interoperability for Microwave Access (WiMAX).
This was developed by the Institute of Electrical and Electronics Engineers under IEEE
standard 802.16 and has a very different history from other 3G systems. The original
specification (IEEE 802.16–2001) was for a system that delivered data over point-topoint
microwave links instead of fixed cables. A later revision, known as fixed WiMAX
(IEEE 802.16–2004), supported point-to-multipoint communications between an omnidirectional
base station and a number of fixed devices. A further amendment, known
as mobile WiMAX (IEEE 802.16e), allowed the devices to move and to hand over their
communications from one base station to another. Once these capabilities were all in
place, WiMAX started to look like any other 3G communication system, albeit one that
had been optimized for data from the very beginning.