2G , 3G & 4G Wireless Communication

2G

2G (or 2-G) is short for second-generation wireless telephone technology.

Second generation 2G cellular telecom networks were commercially launched on the GSM standard in Finland by in 1991.

Three primary benefits of 2G networks over their predecessors were that
1] Phone conversations were digitally encrypted,
2] 2G systems were significantly more efficient on the spectrum allowing for far greater mobile phone penetration levels;
3] And 2G introduced data services for mobile, starting with SMS text messages.

After 2G was launched, the previous mobile telephone systems were retrospectively dubbed 1G. While radio signals on 1G networks are analog, and on 2G networks are digital, both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system.

2G technologies can be divided into TDMA-based and CDMA-based standards depending on the type of multiplexing used. The main 2G standards are:

* GSM (TDMA-based), originally from Europe but used in almost all countries on all six inhabited continents. Today accounts for over 80% of all subscribers around the world.
* IS-95 aka cdmaOne, (CDMA-based, commonly referred as simply CDMA in the US), used in the Americas and parts of Asia. Today accounts for about 17% of all subscribers globally.
* PDC (TDMA-based), used exclusively in Japan
* iDEN (TDMA-based), proprietary network used by Nextel in the US and Telus Mobility in Canada
* IS-136 aka D-AMPS, TDMA-based, commonly referred as simply TDMA in the US

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Advantages

Digital systems were embraced by consumers for several reasons.

* The lower powered radio signals require less battery power, so phones last much longer between charges, and batteries can be smaller.
* The digital voice encoding allowed digital error checking which could increase sound quality by increasing dynamic range and lowering the noise floor.
* The lower power emissions helped address health concerns.
* Going all-digital allowed for the introduction of digital data services, such as SMS and email.
* Greatly reduced fraud. With analog systems it was possible to have two or more "cloned" handsets that had the same phone number.
* Enhanced privacy. A key digital advantage not often mentioned is that digital cellular calls are much harder to eavesdrop on by use of radio scanners.
* Digital voice data can be compressed and multiplexed much more effectively than analog voice encodings through the use of various codecs, allowing more calls to be packed into the same amount of radio bandwidth.
* Equipments were less expensive & small in size

Disadvantages

The downsides of 2G systems, not often well publicized, are:

* In less populous areas, the weaker digital signal may not be sufficient to reach a cell tower.
* Analog has a smooth decay curve, digital a jagged steppy one. Under slightly worse conditions, digital will start to completely fail, by dropping calls or being unintelligible, while analog slowly gets worse, generally holding a call longer and allowing at least a few words to get through.
* While digital calls tend to be free of static and background noise, the lossy compression used by the codecs takes a toll; the range of sound that they convey is reduced.



3G :

International Mobile Telecommunications-2000 (IMT-2000), better known as 3G or 3rd Generation, is a family of standards for wireless communications defined by the International Telecommunication Union.

Services include wide-area wireless voice telephone, video calls, and wireless data, all in a mobile environment.

3G allows simultaneous use of speech and data services and higher data rates (up to 14.4 Mbit/s on the downlink and 5.8 Mbit/s on the uplink).
here are evolutionary standards that are backwards-compatible extensions to pre-existing 2G networks as well as revolutionary standards that require all-new networks and frequency allocations.
The first pre-commercial 3G network was launched by NTT DoCoMo in Japan branded FOMA, in May 2001 on a pre-release of W-CDMA technology.

3G comprises several cellular access technologies. The three most common ones as of 2005 are:

* CDMA2000 - based on 2G Code Division Multiple Access (see Cellular Access Technologies)
* WCDMA (UMTS) - Wideband Code Division Multiple Access
* TD-SCDMA - Time-division Synchronous Code-division Multiple Access

Although 3G was successfully introduced to users across the world, some issues are debated by 3G providers and users:

* Expensive input fees for the 3G service licenses in some jurisdictions
* Differences in licensing terms between states
* Level of debt incurred by some telecommunication companies, which makes investment in 3G difficult
* Lack of state support for financially troubled operators
* Cost of 3G phones
* Lack of coverage in some areas
* High prices for 3G in some countries
* Demand for high speed services in a hand-held device
* Battery life of 3G phones


4G :

International Mobile Telecommunications-Advanced (IMT Advanced), better known as 4G, 4th Generation or Beyond 3G, is the next technological strategy in the field of wireless communications.

A 4G system will upgrade existing communication networks and is expected to provide a comprehensive and secure IP based solution where facilities such as voice, data and streamed multimedia will be provided to users on an "Anytime, Anywhere" basis and at much higher data rates compared to previous generations.

The 4G working group has defined the following as objectives of the 4G wireless communication standard:

* A spectrally efficient system (in bits/s/Hz and bits/s/Hz/site),[1]
* High network capacity: more simultaneous users per cell,[2]
* A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R,[3]
* A data rate of at least 100 Mbit/s between any two points in the world,[3]
* Smooth handoff across heterogeneous networks,[4]
* Seamless connectivity and global roaming across multiple networks,[5]
* High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, etc)[5]
* Interoperability with existing wireless standards,[6] and
* An all IP, packet switched network.[5]

Principal technologies

* Baseband techniques[9]
o OFDM: To exploit the frequency selective channel property
o MIMO: To attain ultra high spectral efficiency
o Turbo principle: To minimize the required SNR at the reception side
* Adaptive radio interface
* Modulation, spatial processing including multi-antenna and multi-user MIMO
* Relaying, including fixed relay networks (FRNs), and the cooperative relaying concept, known as multi-mode protocol

Components :

Access schemes :Recently, new access schemes like Orthogonal FDMA (OFDMA), Single Carrier FDMA (SC-FDMA), Interleaved FDMA and Multi-carrier code division multiple access (MC-CDMA) are gaining more importance for the next generation systems.

IPv6 support: By the time that 4G is deployed, the process of IPv4 address exhaustion is expected to be in its final stages. Therefore, in the context of 4G, IPv6 support is essential in order to support a large number of wireless-enabled devices.

Advanced Antenna Systems: One technology, spatial multiplexing, gained importance for its bandwidth conservation and power efficiency. Spatial multiplexing involves deploying multiple antennae at the transmitter and at the receiver.This is called MIMO (as a branch of intelligent antenna).

Software-Defined Radio (SDR)

SDR is one form of open wireless architecture (OWA). Since 4G is a collection of wireless standards, the final form of a 4G device will constitute various standards.

However 4G is still under developments & will take time till a application is seen.