All over the world, cellular communication services have witnessed a phenomenal growth over the last few decades. The evolution of mobile cellular technology has been categorized into various generations. During the past few decades, cellular
networks have witnessed 4 or 5 generations of technology evolution, namely, from 1G to 4G.
The era of cellular network communications may be considered to have begun way back in the early 1980s through the deployment of the first generation (1G) system invented by AT&T’s Bell labs about a decade earlier. 1G technology which used analogue transmission for speech services came in three principal verities, namely,Nordic Mobile Telephones (NMT),Total Access Communication Systems (TACS)andAdvanced Mobile Phone Service (AMPS).NMT was deployed in the northern European region. TACS was mainly deployed in England, Ireland and Japan. In the United States, the first commercial deployment of cellular telephony was based on AMPS and done in late 1983 by Ameritech. It may be noted that the different systems could not communicate among each other at that time. Only 20 million people worldwide, which was less than 1% of the global population, ever used the first generation system.
Second generation (2G) mobile phone systems emerged in the 1990’s. There were four different 2G systems worldwide, namely,Global System for Mobile com- munication (GSM), Code Division Multiple Access (CDMA), US-CDMA, Per- sonal Digital Cellular (PDC). These2G systems differed from the previous gen- eration in their use of digital transmission instead of analogue transmission. 2G systems offered higher spectrum efficiency, better data services, and more ad- vanced roaming facility. In addition to providing improved voice quality, capacity and security, 2G cellular systems also enabled a few new applications, the most popular among which was the Short Message Service (SMS), first deployed in Europe in 1991. The SMS application proved to be incredibly successful from a commercial standpoint, so much so that in some networks SMSs constituted a major part of the total traffic. In order to enable data transmission on the air-interface, GSM Packet Radio Systems (GPRS) (also known as 2.5G) was in- troduced and this proved to be an evolutionary step for GSM towards high data rates. GPRS and GSM shared the same frequency bands, time slots, and signal- ing links. GPRS supported flexible data transmission rates as well as continuous
2.1 Evolution of Cellular Networks
connection to the network. Typical implementations of GPRS provided user data rates of 20-40kbps. GPRS may be considered to be the most significant step towards third generation (3G). The GSM standard got a further boost in its data handling capabilities with the introduction of Enhanced Data Rate for GSM Evolution (EDGE), in the early part of 1997. It allowed the clear and fast transmission of data and information up to 384kbps speed.
In the beginning of the new millennium, people began to use mobile phones in their daily lives and therefore, service providers experienced exponential growth in the use of 2G phones. In order to meet such demands, the researchers and industry started to work on the next generation of technology, known as 3G. The design objectives of 3G systems were to deliver much higher data rates, provide significant increment in voice capacity, and support advanced services and ap- plications, including multimedia. The International Telecommunication Union (ITU) formalized the objectives for 3G mobile networks with the IMT-2000 stan- dard. 3rd Generation Partnership Project (3GPP), a mobile communications industry collaboration, has continued that work by defining a mobile system that fulfills the IMT-2000 standard. In Europe it was calledUMTS (Universal Terres- trial Mobile System), which is European Telecommunications Standards Institute (ETSI) driven. 3G networks enabled service providers to offer services which include voice telephony, video calls, and broadband wireless data, all in a mobile environment. In the mid 2000’s, first implementations of an evolution of the 3G technology called High Speed Downlink Packet Access (HSDPA) was begun. It is an enhanced 3G mobile telephony communications protocol in the High-Speed Packet Access (HSPA) family, also named as 3.5G, 3G+ or turbo 3G, which al- lows networks based onUMTS to have higher data transfer speeds and capacity.
Initially, HSDPA deployments supported downlink speeds of 1.8, 3.6, 7.2 and 14.0 Mbps. Further speed enhancements were available with HSPA+, which pro- vided speeds of up to 42 Mbps (and up to 84 Mbps with Release 9 of the 3GPP standard).
The ever increasing demands of QoS sensitive multimedia applications and
emergence of new technology in the mobile communication system triggered the researcher community and industry to come up with data-optimized forth genera- tion (4G) technologies. One of the major technological enhancement in 4G is the shift from circuit-switched networks (3G) to an all-IP network. An all IP-based 4G wireless network has intrinsic advantages over its predecessors. The design goal of 4G technology was to deliver a new level of experience to the users in which they have freedom to select any services with desired QoSlevels at afford- able prices, anywhere, anytime. Wimax andLTEwere the first two commercially available 4G technologies deployed in Scandinavia by TeliaSonera. Peak down- load and upload data transfer speeds of 4G LTE can reach up to 100Mbps and 50Mbps, respectively. On the other hand, WiMAX offers peak data rates of 128 Mbps in the downlink and 56 Mbps in the uplink.