4G, short for fourth generation, is the fourth generation of mobile telecommunications technology, succeeding 3G. A 4G system, in addition to the usual voice and other services of 3G, provides mobile ultra-broadband Internet access, for example to laptops with USB wireless modems, to smartphones, and to other mobile devices. Even though 4G is a successor technology of 3G, there can be signification issues on 3G network to upgrade to 4G as many of them were not built on forward compatibility. Conceivable applications include amended mobile web access, IP telephony, gaming services, high-definition mobile TV, video conferencing, 3D television, and cloud computing
Wireless technology has transformed our lives in many ways. Until very recently, we needed a computer wired to a port, to get online. Even wired telephones are becoming a thing of past. Nowadays, we use our mobile phones for banking, to check ticket availability at a Cinema Hall, and many more. Wireless communication is the transfer of information over a distance without the use of enhanced electrical conductors or "wires”. And, Wireless networking refers to any kind of networking that does not involve cables. It helps in saving the cost of cables for networking in addition to providing the mobility.
The nomenclature of the generations generally refers to a change in the fundamental nature of the service, non-backwards-compatible transmission technology, higher peak bit rates, new frequency bands, wider channel frequency bandwidth in Hertz, and higher capacity for many simultaneous data transfers (higher system spectral efficiency in bit/second/Hertz/site).
New mobile generations have appeared about every ten years since the first move from 1981 analog (1G) to digital (2G) transmission in 1992. This was followed, in 2001, by 3G multi-media support, spread spectrum transmission and at least 200 kbit/s peak bit rate, in 2011/2012 expected to be followed by "real" 4G, which refers to all-Internet Protocol (IP) packet-switched networks giving mobile ultra-broadband (gigabit speed) access.
Evolution of Mobile Technologies
Zero Generation Technology (0G)
0G refers to pre-cell phone mobile telephony. Being the predecessors of the first generation of cellular telephones, these systems are called 0G (zero generation) systems. Usually vehicle mounted, they had the transceivers mounted in the vehicle trunk and dials & display mounted near the driver seat.
Technologies used in 0G systems included PTT (Push to Talk), MTS (Mobile Telephone System), IMTS (Improved Mobile Telephone Service), and AMTS (Advanced Mobile Telephone System).
First Generation Technology (1G)
1G refers to the first generation of wireless telecommunication technology, more popularly known as cell phones. In 1G, Narrow band analogue wireless network is used; with this we can have the voice calls. These services are provided with circuit switching. Through 1G, a voice call gets modulated to a higher frequency of about 150MHz and up as it is transmitted between radio towers using a technique called Frequency-Division Multiple Access (FDMA).
Different 1G standards prevalent were AMPS (Advanced Mobile Phone System) in the United States, TACS (Total Access Communications System) in the United Kingdom, NMT (Nordic Mobile Telephone), used in Nordic countries, Eastern Europe and Russia, etc.
Second Generation Technology
2G - 2G first appeared around late 1980’s; 2G system digitized the voice signal, as well as the control link. It provided the facility of short message service (SMS) unlike 1G that had its prime focus on verbal communication. Depending on the type of multiplexing used 2G technologies can be divided into Time Division Multiple Access (TDMA) based and Code Division Multiple Access (CDMA). 2G system offered better quality and much more capacity. 2G cellphone units were generally smaller than 1G units, since they emitted less radio power.
Based on TDMA, Global System for Mobile communications (GSM) is the first European standard & the first commercial network for use by the public for 2nd generation mobile (2G) telephony. A typical 2G G.S.M network service uses 800/900MHz or 1800/1900 frequency spectrum. Typical average data rate of GSM is 9.6 kbps. 2G CDMA (IS-95A) uses BPSK and offers data rate upto 14.4 kbps. The bandwidth of 2G is 30-200 KHz.
2.5G – GPRS (General Packet Radio Service) - 2.5G, which stands for "second and a half generation," is a cellular wireless technology developed in between its predecessor, 2G, and its successor, 3G. The term "second and a half generation" is used to describe 2G-systems that have implemented a packet switched domain in addition to the circuit switched domain.
‘2.5G’ is an informal term, invented solely for marketing purposes, unlike "2G" or "3G" which are officially defined standards based on those defined by the International Telecommunication (ITU).
GPRS (CS1 to CS4) uses GMSK modulation with symbol rate (& modulation rate) of 270 ksym/s. Typical data rate ¬-of GPRS is ~115 kbps. It can be used for services such as Wireless Application Protocol (WAP) access, Multimedia Messaging Service (MMS) and for accessing internet.
IS-95B or cdmaOne is the evolved version of IS-95A and is also designated as 2.5G with theoretical data rates of upto 115 kbps, with generally experienced rates of 64 kbps.
2.75 – EDGE (Enhanced Data rates for GSM Evolution) - EDGE (EGPRS) is an abbreviation for Enhanced Data rates for GSM Evolution, is a digital mobile phone technology, invented by AT&T. EDGE technology is an extended version of GSM & works in GSM networks. EDGE is add-on to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrades. It allows the clear and fast transmission of data. One need not install any additional hardware and software in order to make use of EDGE Technology. Also, there are no additional charges for utilizing this technology.
Uses 9 Modulation coding schemes (MCS1-9). MCS (1-4) uses GMSK, while MCS (5-9) uses 8PSK modulation. 8PSK Increases throughput by 3x (8-PSK – 3 bits/symbol vs GMSK 1 bit/symbol). Modulation bit rate is 810 kbps. It offers data rates of 384kbps, theoretically up to 473.6kbps.
Third Generation Technology
3G, short for third Generation, is the third generation of mobile telecommunications technology.
 This is based on a set of standards used for mobile devices and mobile telecommunication use services and networks that comply with the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union.
 3G finds application in wireless voice telephony, mobile Internet access, fixed wireless Internet access, video callsand mobile TV.
3G telecommunication networks support services that provide an information transfer rate of at least 200 kbit/s. Later 3G releases, often denoted 3.5G and 3.75G, also provide mobile broadband access of several Mbit/s to smartphones and mobile modems in laptop computers. This ensures it can be applied to wireless voicetelephony, mobile Internet access, fixed wireless Internet access, video calls and mobile TV technologies.
Indian Scenario in 4G
India’s first 4G service provider Bharti Airtel is all set to launch its 4G LTE service for mobile customers wherein is 4G users can enjoy fourth generation mobile service over LTE enabled smart-phones.
Initially Airtel will provide 4G Data and Mobile service over recently announced Huawei Ascend P1 LTE smartphone. The Ascend P1 LTE uses Circuit Switched Voice Fall Back technology to support voice calls over 3G and 4G.
Airtel is also testing 4G LTE smartphones from Samsung, ZTE and other Indian smartphone vendors such as Micromax on its 4G LTE network.
Airtel has already launched its 4G network in a handful of cities. Indian telecom operators have received official license to operate 4G LTE networks (TD-LTE) over 2300 MHz band. You have to specifically look for a mobile phone or tablet which mentions 2300 MHz compatibility under its list of technical specifications.
Although, government of India has awarded 4G LTE license over 1800 MHz as well, operators haven’t started offering 4G LTE connection over 1800 MHz as of now. All the major flagship smartphones such as iPhone 5S, HTC One M8 and Sony Xperia Z2 are equipped with Qualcomm baseband solutions. Although the Sony Xperia Z2 and HTC One M8 are currently incompatible with 4G LTE in India (2300 MHz band). Apple iPhone 5S uses Qualcomm MDM9x15 baseband solution to support 2300 MHz 4G LTE spectrum in India and China.
Right now, there are only 4 mobile phones in the Indian market which support the existing 2300 MHz 4G LTE infrastructure and all of them are powered by Qualcomm’s 4G LTE solution.
1.Apple iPhone 5S2.Apple iPhone 5C
3.LG G2 4G LTE4.Xolo LT900
At least the HTC One M8 and Sony Xperia Z2 would be compatible with 4G LTE bands once Indian telecom operators start offering 4G LTE over the 1800 MHz bandwidth. But the Samsung Galaxy S5 wouldn’t be compatible with that as well. Although, Samsung might launch a specialised 4G LTE variant of Galaxy S5 once the widespread adoption of 4G LTE starts in India.
Once operators start releasing 4G LTE in other cities, we might see a huge increase in launch of 4G LTE compatible mobile phones such as the upcoming Micromax Phoenix which is based on Nvidia Tegra 4i SoC. Even MediaTek will be releasing MT6595 SoC which will come with an integrated FDD/TD-LTE radio.
Airtel has launched its 4G LTE services in Kolkata, Bengaluru, Pune, Chandigarh, Panchkula and Mohali and is currently working towards rolling out networks in remaining licence circles. It launched its services in Ludhiana on 19 May 2014. It had also acquired Qualcomm's WBSPL, which had 4G spectrum in New Delhi, Mumbai, Haryana and Kerala.
Vodafone India, a 2G and 3G operator, has indicated that it could launch 4G LTE services in 5 telecom circles such as Mumbai, Delhi, Kolkata, Karnataka and Kerala – where it acquired 5 blocks of spectrum in the 1800 MHz band.
Reliance Jio also has very ambitious 4G rollout plans and will offer voice and 4G services to consumers through the 1800MHz band while enterprise customers will receive these services through the 2300 MHz band.
However Reliance Jio’s spectrum allotment has been challenged in the Supreme Court on 09 May 2014. The Court has sought response of the Centre and the Telecom Regulatory Authority of India (TRAI) on a PIL filed by an NGO challenging grant of 4G licences to Mukesh Ambani's Reliance Jio Infocomm Ltd (RJIL).
A bench of Justices H L Dattu and S A Bobde issued a notice to the Centre, telecom regulator TRAI and RJIL on the petition of the NGO - Centre for Public Interest Litigation (CPIL), which challenged the government's decision to allow Mukesh Ambani's company to offer voice services on its 4G spectrum.
Notwithstanding the court case, Reliance Jio has great plans for its 4G service. Company has recently acquired Network18 Media and Investments, including its unit TV18 Broadcast, spending about Rs 4,000 crore. It may offer free content from the bouquet of television channels under the Network18 group to those who sign up for its data service. While announcing the Network 18 transaction,Reliance Industries said the acquisition would "differentiate Reliance's 4G business by providing a unique amalgamation at the intersect of telecom, Web and digital commerce via a suite of premier digital properties".
Vodafone has retained its existing spectrum in the three metros and significantly enhanced its data capabilities by buying 4G spectrum for the next generation of mobile services in Mumbai, Delhi, Kolkata, Karnataka and Kerala. The telecom operator did not specify time lines for the 4G launch. Vodafone will compete with the Mukesh Ambani-promoted Reliance Jio Infocomm which will have TD-LTE presence in 22 telecom circles.
Vodafone Mumbai is the only operator in India to have data capabilities on all the commercial spectrum bands: 3G on 900MHz and 2100MHz and 4G on 1800MHz.
The government has received bids worth over Rs 60,000 crore from the telecom spectrum auction which ended on 13 February 2014. The auction for 900 MHz and 1800 MHz bands saw strong contest for the radiowaves among eight telecom companies, with the bidding stretching to 68 rounds.
The bid value of the spectrum in the two bands, used for offering 2G services, has reached around 90 per cent of the money that the government had received in the3G spectrum auction in 2010, which fetched Rs 67,718.95 crore.
There is a wide scope for 4G in India but technologists are already thinking of 5G which of course may take a long time to come in our country. Future of 4G is good as this will also enable fast reach of high speed broadband in rural areas where the broadband penetration is very low.