Understand 3G technology

What is 3G ?___________________________________________________________________________________

3G (or 3-G ) is short for third-generation technology . It is used in the context of mobile phone standards. The services associated with 3G provide the ability to transfer simultaneously both voice data (a telephone call) and non-voice data (such as downloading information , exchanging email , and instant messaging ).

3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union.Application services include wide-area wireless voice telephone, mobile Internet access, video calls and mobile TV, all in a mobile environment.

 Several telecommunications companies market wireless mobile Internet services as 3G, indicating that the advertised service is provided over a 3G wireless network. Services advertised as 3G are required to meet IMT-2000 technical standards, including standards for reliability and speed (data transfer rates). To meet the IMT-2000 standards, a system is required to provide peak data rates of at least 200 kbit/s (about 0.2 Mbit/s). However, many services advertised as 3G provide higher speed than the minimum technical requirements for a 3G service. Recent 3G releases, often denoted 3.5Gand 3.75G, also provide mobile broadband access of several Mbit/s to smart phones and mobile modems in laptop computers.

How 3G services work?

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3G technology services is the latest in mobile communication services. 3G here is a term that denotes "third generation". The 3G service is the third innovation, the analog cellular technology generation is the first generation innovation, digital mobile is the second generation, 

The 3G mobile service is the best technology for the true multimedia cell phone that are typically known as smart phones. These phones feature an increased bandwidth and wonderful transfer rates. The phone is also able to play various web-based applications and the various audio and video files designed to be played on a phone.

The 3G services comprise of several cellular access technologies. The three most common cellular technologies are the CDMA2000, which is based on 2G Code Division Multiple Access, the WCDMA or the Wideband Code Division Multiple Access and the TD-SCDMA – the Time-division Synchronous Code-division Multiple Access 

The 3G service networks have an amazing data transfer speed. In fact it can transfer data for up to 3 Mbps that means that it would take almost 15 seconds to download a 3-minute long MP3 song. In comparison, the fastest 2G phones can only achieve up to 144Kbps which means that using them it would take about 8 minutes to download a 3-minute long Mp3 song. 

The 3G service has high data rates that are ideal for downloading any type of information from the Internet. The data rate is amazing to send and receive a large multimedia file. The 3G service enabled phones are like the mini-laptops and they can actually accommodate various complex broadband applications like the video conferencing application, web streaming video applications, sending and receiving faxes and instantly downloading e-mail messages with attachments.

The fact is that the 3G service has truly changed the way telecommunication is done in today’s world.

Features

Data rates

ITU has not provided a clear definition of the data rate users can expect from 3G equipment or providers. Thus users sold 3G service may not be able to point to a standard and say that the rates it specifies are not being met. While stating in commentary that "it is expected that IMT-2000 will provide higher transmission rates: a minimum data rate of 2 Mbit/s for stationary or walking users, and 384 kbit/s in a moving vehicle," the ITU does not actually clearly specify minimum or average rates or what modes of the interfaces qualify as 3G, so various rates are sold as 3G intended to meet customers’ expectations of broadband data.

Security

3G networks offer greater security than their 2G predecessors. By allowing the UE (User Equipment) to authenticate the network it is attaching to, the user can be sure the network is the intended one and not an impersonator. 3G networks use the KASUMI block crypto instead of the older A5/1 stream cipher. However, a number of serious weaknesses in the KASUMI cipher have been identified.

In addition to the 3G network infrastructure security, end-to-end security is offered when application frameworks such as IMS are accessed, although this is not strictly a 3G property.

Applications of 3G

The bandwidth and location information available to 3G devices gives rise to applications not previously available to mobile phone users. Some of the applications are:

§  Mobile TV

§  Video on demand

§  Videoconferencing

§  Telemedicine

§  Location-based services

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Transparent Conductors

Transparent conducting oxides (TCOs) are ubiquitous and are found in a wide range of devices including flat panel displays, touch-sensitive screens, and solar cells. For instance, indium tin oxide (ITO) is one of the most widely used TCOs because it combines a very low resistivity (1x10^-4 ohm cm) with a high transparency of 80-90% for visible light. In most conventional devices, the TCO is used in the form of a thin film on a flat glass plate and consequently conventional thin film coating methods using line-of-sight deposition techniques are adequate. However, for advanced photovoltaics, especially those employing non-planar geometries or nanostructuring, alternative deposition techniques are required for preparing the TCO layers. Atomic layer deposition (ALD) is a synthesis technique that uses alternating, self-limiting chemical reactions to deposit materials in an atomic layer-by-layer fashion and is uniquely suited for coating porous materials. Argonne researchers are developing new techniques for preparing transparent conducting oxide thin films by ALD. In particular, they are developing new ALD chemistries capable of preparing precise, ultrathin films inside of nanoporous templates for fabricating next-generation solar cells. Another focus of their research is to scale up the ALD synthesis of transparent conducting thin films to accelerate the transition of this technology to industry. 

Concentric nanotubes of TiO2 and transparent conducting ITO provide rapid charge flow to improve the efficiency of nanostructured solar cells.

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Next-Generation Photovoltaic Technologies

A new understanding of organic semiconductor junctions

The foundation of almost all conventional inorganic semiconductor devices is the p-njunction, defined by the interface between an electron rich (n-type) and an electron poor (p-type) semiconductor.  First developed in 1949, the Shockley ideal diode equation comprehensively describes the current-voltage characteristics of inorganic semiconductor p-n junctions, providing both physical insight and a quantitative analytical tool that has aided our understanding of the most fundamental properties of semiconductor devices, and in particular, solar cells, over the past six decades.

Organic, or ‘plastic’ electronics, are a relatively new technology that holds the prospect of providing ultra-cheap, lightweight, and flexible electronic applications. Indeed, organic solar cells (OSCs) provide a particularly useful and compelling application of organic electronics.  These devices operate on the basis of a heterojunction formed between ‘donor’ and ‘acceptor’ organic semiconductors, often viewed as analogs to p and n-type inorganic semiconductors, respectively.  As a result, the Shockley Equation has often been applied to analyze OSCs since their inception, but the inherently different physics of organic semiconductors has limited its ability to make useful predictions and direct improvements for both materials and device architectures.  In particular, organic semiconductors are characterized by hopping transport on the nanoscale and tightly bound, localized exciton states that require significant energy to dissociate into free charge carriers as opposed to the delocalized nature of charge carriers in inorganic semiconductors.

Recently, scientists at the Center for Nanoscale Materials collaborated with scientists from the University of Michigan and Northwestern University to develop and test an ideal diode equation for organic semiconductor junctions.  The work focuses on the dynamics of bound charge carrier pairs at the heterojunction and results in an equation that is analogous to the Shockley Equation (see figure, below).  It predicts the temperature and light intensity dependence of solar cell parameters such as the dark current, open circuit voltage (V_oc) and short-circuit current (J_sc), particularly in situations where Shockley-based models break down.  Furthermore, the analysis predicts the maximumV_oc attainable for a given heterojunction material pair, in agreement with the empirically-based conclusions of experimental studies. 

Schematic illustrating the current-voltage characteristics and energetics of Coulombically bound charge carrier pairs at the heterojunction in organic semiconductor junctions.

The model is successfully applied to two archetype, planar heterojunction organic photovoltaic cells composed of co.

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