Evolution of Mobile Networks:
The First Generation (1G):
·         In the United States, and analog cellular mobile communication service called advanced mobile phone service (AMPS) was started in October, 1983.
·         In Europe, several cellular mobile communication services were started. In Norway, Nordic Mobile Telephones (NMT) succeeded in the development of an analog cellular mobile communication system: NMT - 450 [7].
·         In the United Kingdom, Motorola developed an analog cellular mobile communication system called the total access communication system (TACS) based on AMPS in the 1984-1985 periods. In 1983; NMT started a modified NMT - 450 called, NMT - 900 Moreover C-450, RTMS and Radio com - 2000 were respectively introduced in Germany, Italy, and France.
·         Meanwhile, in Japan Nippon Telephone Telegraph (NTT) developed a cellular mobile communication system in the 800 MHz frequency band and started a service at Tokyo in December, 1979. Furthermore, a modified TACS was called ITACS was also introduced in July 1989. Subsequently, narrow band TAC (NTACS), which reduced the required frequency band in half started service in October.
The Second Generation (2G):
The incompatibility of the various system precluded roaming. This meant that the user had to change their mobile terminals when they moved to another Country, Also, 1G was unable to ensure sufficient capacity for increasing users and the speech quality was not good.
Then the introduction to the use of digital cellular radio systems took place. These second generation techniques rely on TDMA/FDD and CDMA/FDD multiple access techniques.
The most popular second generation standards include three TDMA standards and on CDMA standard.
(a)               Global System Mobile (GSM): GSM supports eight time slotted users for each 200 KHz radio channel and has been deployed widely by service providers in Europe, Asia, Australia, South-America and some parts of US. It rely on TDMA/FDD.
(b)               Interim Standard + 36 (IS - 136) : Also known as North-American Digital cellular which supports three times slotted users for each 30 KHz radio channel and is popular choice for carriers in North America, South America and Australia.
(c)                Pacific Digital Cellular  : A Japanese TDMA standard that is similar to IS-136 with more than 50 million users.
(d)               The popular 2G CDMA standard. Interim Standard 95 : Code division multiple access, also known as CDMA-one which supports upto 64 users that are orthogonally coded and simultaneously transmitted on each 1.25 MHz channels CDMA is widely deployed by carriers in North America as well as Korea, Japan, South America and Australia.
Evolution to 2.5G Mobile Radio Networks :
In 2G various standards were designed technologies use circuit-switched data modems that limit data users to a single circuit switched voice channel. with 9.6 Kbps data speed many applications were slower to use through mobile 2.5G allows existing 2G equipment to be modified and supplemented with new base station add-ons and subscriber unit software upgrades to support higher data rate transmissions for web-browsing, email traffic, mobile commerce and location-based mobile services. Wireless Application protocol used for mobile internet services.
The three TDMA upgrade options include :-
(a)        High Speed Circuit Switches Data (HSGSD)
(b)        General Packet Radio Services (GPRS)
(c)        Enhanced Data Rates for GSM Evolution
HSCSD for 2.5 GSM : High speed circuit switched Data is a circuit switched technique that allows a single mobile subscriber to use consecutive user time slots in the GSM standard. HSCSD allows individual data users to communication consecutive time slots in order to obtain higher speed data rate to 57.6 Kbps in GSM network.
GPRS for 2.5 GSM and 1S-136 : General Packet Radio Service is a packet based data network, which is well suited for non-real time internet usage, including the retrieval of email, faxes and asymmetric web browsing, where the user downloads much more data than it uploads on the Internet. It supports multi-user network sharing of individual radio channels and time stops. It offers 171.2 Kpbs data rate transmission.
EDGE for 2.5G GSM and IS-136 : Enhanced Data rates for GSM evolution is a more advanced upgrade to GSM standard and requires the addition of new hardware and software at existing base status EDGE introduces a new digital modulation format 8 PSK. It allows for nine different air interface format. It has best incremental redundancy. It gives 384 Kpbs.
IS-95B for 2.5G CDMA: IS-95 B provides high speed packet and circuit switched data access on a common CDMA radio channel by dedicating multiple orthogonal user channels for specific user and specific purposes IS-95B is more efficient for multiple channel systems now being used in today's more congested CDMA markets.
The Third Generation (3G):
3G systems promise unparallel wireless access in ways that have never been possible before. Multi-megabit internet access, communication using voice over internet protocol (VOIP), voice-activated calls, unparallel network capacity and "always on" access are advantages of 3G.
The eventual 3G evolution for CDMA systems leads to CDMA-2000 are currently based on fundamentals of IS-95B technologies. The 3G evolution for GSM, IS-136 and PDC leads to wide band CDMA also called (Universal Mobile Telecommunication Server) UMTS, W-CDMA is based on the network fundamentals of GSM as well as merged versions of GSM and IS-136 through edge. Thus 3G has two categories, CDMA-2000 and WCDMA.
(A)                3G W-CDMA
The universal mobile telecommunication system is a visionary air interface standard that has evolved since late 1996 under the auspicious of European telecommunication standards institute. UNTS was submitted by ETSI to IMT-2000 body in 1998 for consideration as a world standard. UMTS was known as UMTS terrestrial radio access path and was designed to provide a high capacity upgrade path for GSM. Around the turn, W-CDMA was approved.

(B)                 3G CDMA2000
The cdma2000vision provides a seamless and evolutionary high data rates upgrade path for current users of 2G and 2.5G CDMA technology, using a building block approach that centers on the original 2G CDMA channel bandwidth of 1.25 MHz per radio channel. The current CDMA operates may seamlessly and selectively introduce 3G capabilities at each cell without having to change our entire base stations or reallocate spectrum.

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