3g Technology

 3G refers to the next generation of wireless communications technology; it is a ‘catch all’ name which encompasses everything from the technology to the branding of mobile communication devices.  The aim of 3G (third generation) is to deliver the capability of much higher data rates to mobile communications devices over a large geographical area. Data rates of up to 2megabits per second will be capable in some areas.It is also the aim of 3G to unify the wireless devices the world over, so a user from the UK, can travel Europe, and the US, and use the same, highspeed data links, seamlessly as they travel the globe.  3G is a packet switched suite of protocols, a technology which was originally developed for the internet, it also uses techniques such as Code Division Multiple Access (originally developed by the military) to allow efficient, fast, and secure communications over the wireless medium. To the end user, 3G means fast World Wide Web browsing, file transfers, emailing, even video phoning and video conferencing from their mobile phone, PDA, or laptop. With coverage over all of Europe, the USA, China, Japan, and the rest of the world, with seamless integration between all of these countries and more. Although 3G is relatively an infant, the technology is growing fast, with more and more wireless technology companies developing devices with 3G capabilities, such as Nokia, Siemens and Sony Ericsson.On the horizon is 4G, a technology which will truly integrate the internet, and mobile telecommunications.

Evolution towards 3G

                                  Being called 3G, or third generation, there is, inevitably, a first and second generation.

                                  1G refers to the original analogue mobile phones, which resembled a brick. They were large, and very heavy, due to the weight of the battery, they were also very expensive. However, they paved the way for something that was soon to become a revolution in the technological world, phones would soon start to be smaller, lighter, cheaper, and better. Operating time increased while battery weight dropped, this was due to advancements in battery technology, as well as circuit design which allowed for much lower power consumption.

                                          2G saw the birth of the digital mobile phone, and a standard which is the greatest success story in the history of the mobile phone to date. The Global System for Mobile Communications (GSM) is a standard that unified Europe’s mobile phone technologies, it allows one phone to be used throughout Western Europe. Using TDMA (Time division multiple access), the GSM standard allowed millions of users throughout Europe to travel freely and still be able to use there phone. Although Europe enjoyed a unified standard, in America, three standards still exist, from three different companies. Because of this mobile communications haven’t become nearly as popular in the States, as they have done in Europe.2G worked well for voice communications, it provided data rates of up to 9.6Kbps, good enough for voice, but no where near enough for bandwidth demanding modern day media, such as Video and file transfers. Something which the world was screaming out for, and to provide this, 3G was developed.

                                          Due to the nature of 3G, and its incredible complexity and expensive, the move from 2G to 3G wasn’t going to happen over night, so the 2.5G standard was developed.

                                       The 2.5G standard had a major technically different feature compared to its predecessor, it used Packet Switching technology to transmit data. The General Packet Radio Service (GPRS) replaced GSM as the 2.5G standard. GPRS actually overlays a packet switched technology onto the original GSM circuit switched network. Data rates of 2.5G can reach 50kbps, some may think this is a waste of time, and service provides should have gone straight to the goal and implemented 3G, however, the 2.5G standard is a much needed step, as it gives service providers experience of running packet switched networks, and charging on a data bases, rather than a time basis.

                           Other than GPRS, another standard called EDGE is another upgrade option from GSM, and is three times faster with a maximum transfer rate of 150Kbps as opposed to GPRS’s 50Kbps. EDGE also can be an upgrade from TDMA networks, so some American operators may go this route.

How does 3G work?

                      3G is a packet switched technology, much like the internet. There are some basic principles of Radio Transmission Technologies (RTT’s) we need to understand before we can understand how 3G works, these are:

Simplex & Duplex, TDD & FDD, Symmetric & Asymmetric transmission, TDMA & FDMA, Circuit switching & packet switching and 3G geographical cells.

Simplex and Duplex

                        In a simplex transmission, information can only flow one way at one time, this is because there is only one frequency being used to communicate on. The easiest way of explaining this is to use walkie-talkies as an example. With a set of walkie-talkies, only one person can talk to the other at any given time, for the other person to transmit, they must wait until the other person has stopped.

                        In a duplex transmission, two data transmissions can be sent at any one time, this is how mobile phones work, it allows both people to speak at the same time, without any delay. If more than two data transmissions can happen at any one time, this is called multiplex.

TDD and FDD

                        Up until the recent developments of mobile phones, FDD (frequency division duplex) was used, this is where several frequencies are used, one for the upstream (signals going from the phone to the base station), and one for the downstream (the opposite, from the base station to the phone). A “guard band” is also needed, which sits in between the frequencies to separate them and provide isolation.

                        Although FDD works, it is very wasteful, as it uses several frequencies in total, and not to there full potential. This is why TDD was developed.

                        TDD means Time Division Duplex, and as the name suggests, this uses time, rather than frequency to do the duplexing, hence saving valuable frequencies. It works by switching the signals very rapidly. First the upstream transmits, then the downstream transmits and this continues to cycle, this happens so quick, it seems like the upstream and downstream are permanently connected. This gives the same end product as FDD, but uses much less frequencies. As with FDD, this also requires some sort of guard, but as we are duplexing in the time domain, it uses a guard time, rather than a guard frequency.

Symmetric and Asymmetric Transmission

                         A symmetric transmission is where the upstream, and downstream are the same speed, or data rate. Things such as voice on mobile phones use symmetric transmission, as the data rate needed to transmits your voice is the same as receiving another persons.

                         For things like video broadcasts, internet surfing etc, a lot more downstream bandwidth is required, as you will mostly be receiving data. Typically the only things being sent upstream in that case is requests (for instance, you clicking on a link in your wap/internet browser), or packet acknowledgments. A typical example of an Asymmetric connection is ADSL broadband, the A, which coincidently enough stands for Asymmetric, usually has 256Kbps of upstream, and 512+kbps on the downstream bandwidth.

 TDMA vs. CDMA

                        We have considered how a mobile phone can send and receive calls at the same time (via an uplink and a downlink). Now we will examine how many users can be multiplexed into the same channel (i.e., share the channel) without getting interference from other users, a capability called multiple access. For 3G technology, there are basically two competing technologies to achieve multiple access: TDMA and CDMA.

TDMA is Time Division Multiple Access. It works by dividing a single radio frequency into many small time slots. Each caller is assigned a specific time slot for transmission. Again, because of the rapid switching, each caller has the impression of having exclusive use of the channel.

CDMA is Code Division Multiple Access. CDMA works by giving each user a unique code. The signals from all the users can then be spread over a wide frequency band. The transmitting frequency for any one user is not fixed but is allowed to vary within the limits of the band. The receiver has knowledge of the sender's unique code, and is therefore able to extract the correct signal no matter what the frequency.

                        This technique of spreading a signal over a wide frequency band is known as spread spectrum. The advantage of spread spectrum is that it is resistant to interference - if a source of interference blocks one frequency, the signal can still get through on another frequency. Spread spectrum signals are therefore difficult to jam, and it is not surprising that this technology was developed for military uses.

                        Finally, let's consider another robust technology originally developed by the military which is finding application with 3G: packet switching.

Circuit Switching vs. Packet Switching

                        Traditional connections for voice communications require a physical path connecting the users at the two ends of the line, and that path stays open until the conversation ends. This method of connecting a transmitter and receiver by giving them exclusive access to a direct connection is called circuit switching.

                        Most modern networking technology is radically different from this traditional model because it uses packet data. Packet data is information which is:

o chopped into pieces (packets),

o given a destination address,

o mixed with other data from other sources,

o transmitted over a line with all the other data,

o reconstituted at the other end.

Packet-switched networks chop the telephone conversation into discrete "packets" of data like pieces in a jigsaw puzzle, and those pieces are reassembled to recreate the original conversation. Packet data was originally developed as the technology behind the Internet.

A data packet.

The major part of a packet's contents is reserved for the data to be transmitted. This part is called the payload. In general, the data to be transmitted is arbitrarily chopped-up into payloads of the same size. At the start of the packet is a smaller area called a header. The header is vital because the header contains the address of the packet's intended recipient. This means that packets from many different phone users can be mixed into the same transmission channel, and correctly sorted at the other end. There is no longer a need for a constant, exclusive, direct channel between the sender and the receiver.

                   Packet data is added to the channel only when there is something to send, and the user is only charged for the amount of data sent. For example, when reading a small article, the user will only pay for what's been sent or received. However, both the sender and the receiver get the impression of a communications channel which is "always on".

On the downside, packets can only be added to the channel where there is an empty slot in the channel, leading to the fact that a guaranteed speed cannot be given. The resultant delays pose a problem for voice transmission over packet networks, and is the reason why internet pages can be slow to load.

3G geographical cells

              The 3G network has a hierarchal network of different sized cells. These are:

                        

Ø  A Macro cell this is the biggest of the three areas, coverage is normally around the size of a city.

Ø  A Micro cell this cell has the coverage, of about the size of city centre.

Ø  A Pico cell The smallest coverage, perhaps a office complex, hotel, or airport. A Pico cell is often known as a “hot spot”.

                        The reason for the above division of regions is simple, shorter range communications are faster, and allow for a higher amount of users. This is why a Pico cell, or hot spot., is located to a small geographical area which is a very busy area, such as an airport.

                        TDD isn’t good in transmitting long distances, this is because of the delay. If you think, TDD uses time to duplex signals onto the same frequency. The further the mobile phone is away from the base station, the longer it takes a signal to travel, because it takes longer, there is more of a delay, so because of this the switching between time slots cannot happen so quick, so the useable bandwidth decreases.

2G Standards

                        The existing mobile phone market is referred to as the "second generation" of digital mobile communications, or "2G" (analogue mobile phones were "1G"). The European market is controlled by the Global System for Mobile communications (GSM) digital wireless standard. This uses TDMA as its radio transmission technology (RTT). GSM has proven to be the great success story of mobile standards as it has become the unifying standard in Europe - it is possible to use one phone throughout Western Europe. Because of the number of wireless users are in Europe this has greatly strengthened GSM's position as the basis for a potential global standard. The hegemony of GSM has resulted in Finland's Nokia and the UK's Vodafone becoming the powerhouses of the wireless economy.

                              In North America the situation is not nearly so unified. The situation is divided three-ways between GSM, a TDMA-based system from AT&T Wireless (IS-136), and a CDMA system called CDMAone (IS-95A) from Sprint and Verizon. This confusion of standards has resulted in the reduced popularity of cellphones in the US. CDMAone has perhaps the strongest grip on the American market, as well as being popular in Asia.

2G data transmission rates do not exceed 9.6Kbps (kilobits per second). This is not nearly fast enough to achieve complex 3G functionality.

2.5G Standards

                        The transition from 2G to 3G is technically extremely challenging (requiring the development of radically new transmission technologies), and highly expensive (requiring vast capital outlay on new infrastructure). For both of these reasons it makes sense to move to 3G via intermediate 2.5G standards.

                        2.5G radio transmission technology is radically different from 2G technology because it uses packet switching. GPRS (General Packet Radio Service) is the European 2.5G standard, the upgrade from GSM. GPRS overlays a packet-switched architecture onto the GSM circuit-switched architecture. It is a useful evolutionary step on the road to 3G because it gives telecoms operators experience of operating packet networks, and charging for packet data. Data transfer rates will reach 50Kbps.

                        EDGE (Enhanced Data for Global Evolution) is another 2.5G upgrade path from GSM. EDGE is attractive for American operators as it is possible to upgrade to EDGE from both TDMA (IS-136) networks as well as from GSM. You might see the full EGDE standard referred to as UWC-136.

                        EDGE data rates are three times faster than GPRS. Realistically, the maximum rate that EDGE will be able to achieve will be 150Kbps. Even so, EDGE might be used for some pseudo-3G networks (the minimum cut-off data rate for 3G systems is 144Kbps) though this is not generally regarded as a bona fide 3G solution.

                        As EDGE would be cheaper than a full-blown 3G solution, this makes it attractive, especially for operators which cannot afford a licence for the full 3G radio spectrum. Most notably, AT&T has announced it is to use EDGE. AT&T has claimed a maximum data rate of 384Kbps for EDGE, although experts point out that "this is based on the ideal scenario of one person using the network standing next to a base station". AT&T's wireless division, after receiving a $9.8 billion stake from Japan's NTT DoCoMo i-mode service, plans to overlay the 3G standard, W-CDMA, onto their EDGE networks in the American market.

                        Deploying EDGE might prove surprisingly complex - it's more than just a software upgrade. It may require additions to the hardware subsystems of base stations, changes to base station antennas, and possibly require the construction of new base stations. For these reasons, some GSM operators might not adopt EDGE but might migrate from GSM or GPRS directly to the 3G standard (W-CDMA).

                        The 2.5G upgrade from CDMAone (IS-95A) is to CDMAone (IS-95B) which adds packet-switched capability. It offers data rates up to 115Kbps.

3G Standards

                        The 3G standard was created by the International Telecommunication Union (ITU) and is called IMT-2000. The aim of IMT-2000 is to harmonize worldwide 3G systems to provide global roaming. However, as was explained in the introduction to this section, harmonizing so many different standards proved extremely difficult. As a result, what we have been left with is five different standards grouped together under the IMT-2000 label:

W-CDMA

CDMA2000

TD-CDMA/TD-SCDMA

DECT

UWC-136

At this point, the definition of what is and what isn't "3G" becomes somewhat murky. Of these five standards, only three allow full network coverage over macro cells, micro cells and pico cells and can thus be considered as full 3G solutions: W-CDMA, CDMA2000, and TD-SCDMA. Of the remainder, DECT is used for those cordless phones you have in the house, and could be used for 3G short-range "hot-spots" (hence, it could be considered as being "part of a 3G network"), but it does not allow full network coverage so is not considered further here. And UWC-136 is another name for EDGE which is generally considered to be a 2.5G solution and was considered in the previous section.

So that leaves W-CDMA, CDMA2000, and TD-SCDMA - the bona fide 3G solutions.

W-CDMA

                        The 3G standard that has been agreed for Europe and Japan (very important markets) is known as UMTS. UMTS is an upgrade from GSM via GPRS or EDGE. UMTS is the European vision of 3G, and has been sold as the successor to the ultra-successful GSM.

                        The terrestrial part of UMTS (i.e., non-satellite) is known as UTRA (UMTS Terrestrial Radio Access). The FDD component of UTRA is based on the W-CDMA standard  (UTRA FDD). This offers very high (theoretical!) data rates up to 2Mbit/sec.The TDD component of UTRA is called TD-CDMA (or UTRA TDD) and will be considered later.

                         The standardisation work for UMTS is being carried-out under the supervision of the Third Generation Partnership Project (3GPP).W-CDMA has recently been renamed 3GSM.

CDMA 2000

                       The chief competitor to Europe's UMTS standard is San Diego-based Qualcomm's CDMA2000.The standardisation work for CDMA2000 is being carried-out under the supervision of the Third Generation Partnership Project 2, (3GPP2). The CDMA Development Group offers advice to 3GPP2.

                        Even though "W-CDMA" and "CDMA2000" both have "CDMA" in their names, they are completely different systems using different technologies. However, it is hoped that mobile devices using the two systems will be able to talk to each other.

                        CDMA2000 has two phases: phase one is 1XRTT (144 Kbps) (also known as 1X). The next evolutionary step is to the two CDMA2000 1X EV ("EV" = "Evolution") standards. CDMA2000 1X EV-DO ("Data Only") will use separate frequencies for data and voice. The following step is to CDMA2000 1X EV-DV ("Data and Voice") which will integrate voice and data on the same frequency band.

                        South Korea's SK Telecom launched the world's first 3G system in October 2000. Their system is based on CDMA2000 1X. They were followed by LG Telecom and KT Freetel (both Korean). Operational 3G systems based on CDMA2000 1X are now appearing around the world.

                        In the USA, Sprint has launched its nationwide CDMA2000 1X service called “Sprint Power Vision”. With Sprint PCS Vision Multimedia Services, customers get streaming audio and video content from familiar sources, including ABC News Now, NFL Network, Fox Sports, ESPN, NBC Discovery Channel, and many more. Sprint offer a range of multimedia phones including the Fusic.

TD-CDMA/TD-SCDMA

                        The UMTS standard also contains another radio transmission standard which is rarely mentioned: TD-CDMA (TDD UTRA because it is the TDD component of UTRA). TD-CDMA was developed by Siemens. While W-CDMA is an FDD technology (requiring paired spectrum), TD-CDMA is a TDD technology and thus can use unpaired spectrum. TDD is well-suited to the transmission of internet data.

                        China has more mobile phone users than any other country in the world, so anything China does in 3G cannot be ignored. The Chinese national 3G standard is a TDD standard similar to TD-CDMA: TD-SCDMA. TD-SCDMA was developed by the China Academy of Telecommunications Technology (CATT) in collaboration with Siemens. TD-SCDMA eliminates the uplink/downlink interference which affects other TDD methods by applying "terminal synchonisation" techniques (the "S" in TD-SCDMA stands for "synchronisation"). Because of this, TD-SCDMA allows full network coverage over macro cells, micro cells, and pico cells. Hence, TD-SCDMA stands alongside W-CDMA and CDMA2000 as a fully-fledged 3G standard. The 3GPP have extended the TD-CDMA standard to include TD-SCDMA as an official IMT-2000 standard.

                        Unfortunately, TD-SCDMA has performed poorly in trials, and Chinese network operators may prefer W-CDMA over TD-SCDMA.

3G Applications:

Ø Wireless Internet

Ø Audio on demand

Ø Electronic postcards

Ø Video conferencing

Ø Secure mobile commerce transactions

Ø Traffic and traveling information - location specific

Ø Information services:

o Games

o E-mail

o Sports

o News Public transport

o Entertainment/gambling

o Job adverts

Ø Video telephony: Point-to-point video services

Ø On-line game:

o Download

o Rentals

o Review and tips/cheats

Ø Live & archive video:

o Short clips

o Information

o Entertainment

The 3G Performance Advantage :

      Time to download a 1 MB file:

• Fixed line modem: 3 minutes
• GSM cell phone: 15 minutes
• Enhanced GSM phone: 1-5 minutes
• 3G phone (outdoor): 21 seconds
• 3G phone (indoor): 4 seconds
  

Bandwidth and speed:

                        3G promises increased bandwidth, up to 384 Kbps when a device is stationary or moving at pedestrian speed, 128 Kbps in a car, and 2 Mbps in fixed applications. It is expected that IMT-2000 will provide higher transmission rates: a minimum speed of 2Mbit/s and maximum of 14.4Mbit/s for stationary users, and 348 kbit/s in a moving vehicle

The Future of 3G:

                        There’s no doubt what is wanted for the future of 3G, and that’s convergence. Leading 3G figureheads around the world want a convergence of the phone networks, to unite the world as a whole with a wireless technology that is compatible across the globe.

                        There’s a good chance this will happen, as it has already begun to. And it possible won’t be far off that we see perhaps a sub-standard introduced that converges the different 3G standards into one global roaming capable standard.

                        On the horizon is 4G, which promises to bring true convergence of internet’s IP protocol technology to mobiles. By the time 4G is distributed, IPv6 will be well on its way, and the possibilities will be endless. Ever thought about texting your boiler to tell it to get the heating on just as you leave work?

3G Summary :

                        3G mobile is a major opportunity for business, commerce and consumers.Brings together the two fastest growing market sectors - Mobile and Internet Market.Services and standards evolving from 2G to 3G Significant opportunities for value added content and service providers.