First generation cellular mobile communication system
In the late 1970s, the first generation cellular mobile communication system
characterized by frequency division multiple access (FDMA) and analog frequency
module (FM) came into being, pioneering the commercialization of cellular mobile
communication systems. The major modes in this phase include TACS of the UK,
AMPS of the US and NMT of north Europe. This phase featured defects such as low
frequency utilization, small system capacity, no united international standard, very
complicated equipment, high cost, requirement of certain protection bands, no effective
anti-interference and anti-attenuation measures, poor voice quality, low security etc., as
well as limited number of subscribers and incapability of non-voice services and digital
communication services. With the development of services, the firs generation cellular
mobile communication system became unable to satisfy the market requirement. Further
more, in the transmission system, the voice transmission was implemented in the analog
mode, while signaling gateways adopted the digital mode, resulting in ineffective control
of network management.
Second generation cellular mobile communication system
In mid 1980s, the second-generation cellular mobile communication system featuring
TDMA, CDMA and digital modulation (QPSK, p/4-QPSK and GMSK) appeared. The
major modes in this phase include GSM of Europe, DAMPS of the US and the CDMA
system put forward by Qualcomm of the US. At that time, since some critical techniques
in the CDMA system were not properly solved, the development of the CDMA
technology was relatively slow. However, since the GSM system adopted the TDMA
technology, which was mature at that time, the utilization of frequency spectrum was
increased, and the shortcomings of the analog system were well solved. Therefore it
gained wide support from telecom operators and equipment manufacturers of the world,
and the globally united GSM system standard was made up. However, for the very
reason that this kind system used the TDMA mode, the anti-interference and antiattenuation
capability of this kind of system was still unsatisfactory, certain protection
time slots were required, and the system capacity was unable to meet the growing
requirements of the users. Besides, the design of this kind of system is very complicated,the frequency utilization was not high, and the hard handoff mode was adopted for intercell
handoff, which tended to cause call drops, and was unable to satisfy the users’
growing fast data transmission and broadband video multimedia service
requirements.
Third generation cellular mobile communication system
The third generation cellular mobile communication system (3G) is also called IMT-
2000, implying that the system’s working frequency band is 2000MHz, and its
maximum service rate can be as high as 2 Mbit/s. Its technical basis is broadband WCDMA,
characterized mainly by multimedia and intelligent features. It can improve the
multi-element transmission rate, and realize the general integration of ground cellular
system, cordless system, cellular mobile communication system and satellite system -
the real global services. It provides a unified platform for the combination and
distribution of various services. Although the third generation cellular mobile
communication system still has room for perfection, the general framework has been
defined. It has the following tree major features:
Seamless global roaming.
High-speed transmission. High-speed mobile environment: 144kbit/s; walking lowspeed
mobile environment: 384kbit/s; Indoor static environment: 2Mbit/s;
Seamless service transfer. That is, interworking is available in fixed networks, mobile
networks and satellite services.
The technology of 3G is the multimedia communication system that uses the IP
technology as bearer to realize end-to-end IP and provide multiple serviced. Although
the development of 3G and the formulation of its standard have been held up due to
different technical, political and commercial interests, and there are as many as ten
commercial standards for 3G have been put forward up to now, yet the basis for the
transmission mode of all these standards is CDMA.
