4G is the Short Term for Fourth

8/14/2019 4G is the Short Term for Fourth

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4G is the short term for fourth-generation wireless, the stage of broadband mobilecommunications that will supercede the third generation ( 3G). While neither standards

bodies nor carriers have concretely defined or agreed upon what exactly 4G will be, it isexpected that end-to-end IP and high-quality streaming video will be among 4G'sdistinguishing features. Fourth generation networks are likely to use a combination of

WiMAX and WiFi .

Technologies employed by 4G may include SDR (Software-defined radio) receivers,OFDM (Orthogonal Frequency Division Multiplexing), OFDMA (Orthogonal FrequencyDivision Multiple Access), MIMO (multiple input/multiple output) technologies, UMTSand TD-SCDMA . All of these delivery methods are typified by high rates of datatransmission and packet-switched transmision protocols. 3G technologies, by contrast,are a mix of packet and circuit-switched networks.

When fully implemented, 4G is expected to enable pervasive computing , in whichsimultaneous connections to multiple high-speed networks provide seamless handoff s

throughout a geographical area. Network operators may employ technologies such ascognitive radio and wireless mesh network s to ensure connectivity and efficientlydistribute both network traffic and spectrum.

The high speeds offered by 4G will create new markets and opportunities for bothtraditional and startup telecommunications companies. 4G networks, when coupled withcellular phone s equipped with higher quality digital camera s and even HD capabilities,will enable vlog s to go mobile, as has already occurred with text-based moblog s. Newmodels for collaborative citizen journalism are likely to emerge as well in areas with 4Gconnectivity.

A Japanese company, NTT DoCoMo, is testing 4G communication at 100 Mbps for mobile users and up to 1 Gbps while stationary. NTT DoCoMo plans on releasing their first commercial network in 2010. Other telecommunications companies, however, aremoving into the area even faster. In August of 2006, Sprint Nextel announced plans todevelop and deploy a 4G broadband mobile network nationwide in the United Statesusing WiMAX. The United Kingdom's chancellor of the exchequer announced a plan toauction 4G frequencies in fall of 2006.

4G technologies are sometimes referred to by the acronym "MAGIC," which stands for Mobile multimedia, Anytime/any-where, Global mobility support, Integrated wirelessand Customized personal service.
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SDR

Software-defined radio (SDR), sometimes shortened to software radio (SR), refers to

wireless communication in which the transmitter modulation is generated or defined by acomputer, and the receiver uses a computer to recover the signal intelligence.? To selectthe desired modulation type, the proper programs must be run by microcomputers thatcontrol the transmitter and receiver.

A typical voice SDR transmitter, such as might be used in mobile two-way radio or cellular telephone communication, consists of the following stages.? Items with asterisksrepresent computer-controlled circuits whose parameters are determined by the

programming (software).

Microphone

Audio amplifier Analog-to-digital converter ( ADC ) that converts the voice audio to ASCII data * Modulator that impresses the ASCII intelligence onto a radio-frequency ( RF)

carrier * Series of amplifiers that boosts the RF carrier to the power level necessary for

transmission Transmitting antenna

A typical receiver designed to intercept the above-described voice SDR signal wouldemploy the following stages, essentially reversing the transmitter's action.? Again, itemsfollowed by asterisks represent programmable circuits.

Receiving antenna superheterodyne system that boosts incoming RF signal strength and converts it to

a constant frequency Demodulator that separates the ASCII intelligence from the RF carrier * Digital-to-analog converter ( DAC ) that generates a voice waveform from the

ASCII data * Audio amplifier Speaker, earphone, or headset

The most significant asset of SDR is versatility.? Wireless systems employ protocols thatvary from one service to another.? Even in the same type of service, for example wirelessfax, the protocol often differs from country to country. ? A single SDR set with an all-inclusive software repertoire can be used in any mode, anywhere in the world.? Changingthe service type, the mode, and/or the modulation protocol involves simply selecting andlaunching the requisite computer program, and making sure the batteries are adequatelycharged if portable operation is contemplated.
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The ultimate goal of SDR engineers is to provide a single radio transceiver capable of playing the roles of cordless telephone, cell phone, wireless fax, wireless e-mail system, pager, wireless videoconferencing unit, wireless Web browser, Global PositioningSystem ( GPS ) unit, and other functions still in the realm of science fiction, operable fromany location on the surface of the earth, and perhaps in space as well.

Orthogonal frequency-division multiplexing (OFDM) is a method of digital modulation in which a signal is split into several narrowband channel s at different frequencies. Thetechnology was first conceived in the 1960s and 1970s during research into minimizinginterference among channels near each other in frequency.

In some respects, OFDM is similar to conventional frequency-division multiplexing(FDM ). The difference lies in the way in which the signals are modulated anddemodulated. Priority is given to minimizing the interference, or crosstalk , among thechannels and symbols comprising the data stream. Less importance is placed on

perfecting individual channels.

OFDM is used in European digital audio broadcast services. The technology lends itself to digital television , and is being considered as a method of obtaining high-speed digitaldata transmission over conventional telephone lines. It is also used in wireless local areanetworks.

Also see frequency-division multiplexing ( FDM ), time-division multiplexing ( TDM ), andmulti-carrier modulation ( MCM ).
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MIMO (multiple input, multiple output) is an antenna technology for wirelesscommunications in which multiple antennas are used at both the source (transmitter) andthe destination (receiver). The antennas at each end of the communications circuit arecombined to minimize errors and optimize data speed. MIMO is one of several forms of

smart antenna technology, the others being MISO (multiple input, single output) andSIMO (single input, multiple output).

In conventional wireless communications, a single antenna is used at the source, andanother single antenna is used at the destination. In some cases, this gives rise to

problems with multipath effects. When an electromagnetic field ( EM field ) is met withobstructions such as hills, canyons, buildings, and utility wires, the wavefronts arescattered, and thus they take many paths to reach the destination. The late arrival of scattered portions of the signal causes problems such as fading, cut-out (cliff effect), andintermittent reception (picket fencing). In digital communications systems such aswireless Internet, it can cause a reduction in data speed and an increase in the number of

errors. The use of two or more antennas, along with the transmission of multiple signals(one for each antenna) at the source and the destination, eliminates the trouble caused bymultipath wave propagation, and can even take advantage of this effect.

MIMO technology has aroused interest because of its possible applications in digitaltelevision ( DTV ), wireless local area networks ( WLAN s), metropolitan area networks(MAN s), and mobile communications.
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UMTS (Universal Mobile Telecommunications Service) is a third-generation ( 3G) broadband , packet -based transmission of text, digitized voice, video, and multimedia atdata rates up to 2 megabits per second ( Mbps ). UMTS offers a consistent set of servicesto mobile computer and phone users, no matter where they are located in the world.

UMTS is based on the Global System for Mobile ( GSM ) communication standard. It isalso endorsed by major standards bodies and manufacturers as the planned standard for mobile users around the world. Once UMTS is fully available, computer and phone userscan be constantly attached to the Internet wherever they travel and, as they roam , willhave the same set of capabilities. Users will have access through a combination of terrestrial wireless and satellite transmissions. Until UMTS is fully implemented, userscan use multi-mode devices that switch to the currently available technology (such asGSM 900 and 1800) where UMTS is not yet available.

Previous cellular telephone systems were mainly circuit-switched , meaning connectionswere always dependent on circuit availability. A packet-switched connection uses the

Internet Protocol ( IP), meaning that a virtual connection is always available to any other end point in the network. UMTS also makes it possible to provide new services likealternative billing methods or calling plans. For instance, users can choose to pay-per-bit,

pay-per-session, flat rate, or asymmetric bandwidth options. The higher bandwidth of UMTS also enables other new services like video conferencing or IPTV . UMTS mayallow the Virtual Home Environment ( VHE ) to fully develop, where a roaming user canhave the same services to either at home, in the office or in the field through acombination of transparent terrestrial and satellite connections.

The electromagnetic radiation spectrum for UMTS has been identified as frequency bands 1885-2025 MHz for future IMT-2000 systems, and 1980-2010 MHz and 2170-

2200 MHz for the satellite portion of UMTS systems.

LAST UPDATED:20 Jun 2006
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TD-SCDMA (time division synchronous code division multiple access) is a mobiletelephone standard for wireless network operators who want to move from a secondgeneration (2G) wireless network to a third-generation ( 3G) one. Supporting datatransmission at speeds up to 2 Mbps , TD-SCDMA combines support for both circuit-

switched data, such as speech or video, and also packet-switched data from the Internet.The standard combines time division multiple access ( TDMA ) with an adaptive,synchronous-mode code division multiple access ( CDMA ) component.

TD-SCDMA was developed by the China Academy of Telecommunications Technology(CATT) in collaboration with Datang and Siemens.
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4G is the Short Term for Fourth