Third generation is the generic term used for the next generation of mobile communications systems. 3G will provide enhanced services to those - such as voice, text and data - predominantly available today.
Video on demand, high speed multimedia and mobile Internet access are just a few of the possibilities for users in the future. 3G Services will expand the possibilities of information and communication.
UMTS is a part of the International Telecommunications Union's (ITU's) 'IMT-2000' vision of a global family of third-generation mobile communications systems.
The technology concepts for third generation systems and 3G services are currently under development industry wide. The global 3G Partnership Project (3GPP), a collaboration of organisations which includes the GSM Association, are committed to bringing us the 3rd Generation mobile systems.
The GSM Association's vision of 3G is based on today's GSM standard, but evolved, extended and enhanced to include an additional radio air interface, better suited for high speed and multimedia data services. This system will enable users of current second generation GSM wireless networks to migrate easily to the new third generation services, with minimal disruption. This new evolved phase of GSM will in addition be an important and integral part of the ITU's IMT-2000 family.
Introduction - Evolution of the Mobile Market
The first radiotelephone service was introduced in the US at the end of the 1940s, and was meant to connect mobile users in cars to the public fixed network. In the 1960s, a new system launched by Bell Systems, called Improved Mobile Telephone Service (IMTS), brought many improvements like direct dialing and higher bandwidth. The first analog cellular systems were based on IMTS and developed in the late 1960s and early 1970s. The systems were cellular because coverage areas were split into smaller areas or cells, each of which is served by a low power transmitter and receiver.
This first generation (1G) analog system for mobile communications saw two key improvements during the 1970s: the invention of the microprocessor and the digitization of the control link between the mobilephone and the cell site.
Second generation (2G) digital cellular systems were first developed at the end of the 1980s. These systems digitized not only the control link but also the voice signal. The new system provided better quality and higher capacity at lower cost to consumers.
Third generation (3G) systems promise faster communications services, including voice, fax and Internet, anytime and anywhere with seamless global roaming. ITUâ„¢s IMT-2000 global standard for 3G has opened the way to enabling innovative applications and services (e.g. multimedia entertainment, infotainment and location-based services, among others). The first 3G network was deployed in Japan in 2001. 2.5G networks, such as GPRS (Global Packet Radio Service) are already available in some parts of Europe.
Work has already begun on the development of fourth generation (4G) technologies in Japan. It is to be noted that analog and digital systems, 1G and 2G, still co-exist in many areas.
The Basics of Cellular Technology and the Use of the Radio Spectrum
Mobile operators use radio spectrum to provide their services. Spectrum is generally considered a scarce resource, and has been allocated as such. It has traditionally been shared by a number of industries, including broadcasting, mobile communications and the military. At the World Radio Conference (WRC) in 1993, spectrum allocations for 2G mobile were agreed based on expected demand growth at the time. At WRC 2000, the resolutions of the WRC expanded significantly the spectrum capacity to be used for 3G, by allowing the use of current 2G spectrum blocks for 3G technology and allocating 3G spectrum to an upper limit of 3GHz.
Before the advent of cellular technology, capacity was enhanced through a division of frequencies, and the resulting addition of available channels. However, this reduced the total bandwidth available to each user, affecting the quality of service. Cellular technology allowed for the division of geographical areas, rather than frequencies, leading to a more efficient use of the radio spectrum. This geographical re-use of radio channels is knows as frequency reuse.
In a cellular network, cells are generally organized in groups of seven to form a cluster. There is a cell site or base station at the centre of each cell, which houses the transmitter/receiver antennae and switching equipment. The size of a cell depends on the density of subscribers in an area: for instance, in a densely populated area, the capacity of the network can be improved by reducing the size of a cell or by adding more overlapping cells. This increases the number of channels available without increasing the actual number of frequencies being used. All base stations of each cell are connected to a central point, called the Mobile Switching Office (MSO), either by fixed lines or microwave. The MSO is generally connected to the PSTN (Public
Switched Telephone Network):
Cellular technology allows the hand-off of subscribers from one cell to another as they travel around. This is the key feature which allows the mobility of users. A computer constantly tracks mobile subscribers of units within a cell, and when a user reaches the border of a call, the computer automatically hands-off the call and the call is assigned a new channel in a different cell.
International roaming arrangements govern the subscriberâ„¢s ability to make and receive calls the home networkâ„¢s coverage area.
Access Technologies (FDMA, TDMA, CDMA)
FDMA: Frequency Division Multiple Access (FDMA) is the most common analog system. It is a technique whereby spectrum is divided up into frequencies and then assigned to users. With FDMA, only one subscriber at any given time is assigned to a channel. The channel therefore is closed to other conversations until the initial call is finished, or until it is handed-off to a different channel. A full-duplex FDMA transmission requires two channels, one for transmitting and the other for receiving. FDMA has been used for first generation analog systems.
TDMA: Time Division Multiple Access (TDMA) improves spectrum capacity by splitting each frequency into time slots. TDMA allows each user to access the entire radio frequency channel for the short period of a call. Other users share this same frequency channel at different time slots. The base station continually switches from user to user on the channel. TDMA is the dominant technology for the second generation mobile cellular networks.
CDMA: Code Division Multiple Access is based on spread spectrum technology. Since it is suitable for encrypted transmissions, it has long been used for military purposes. CDMA increases spectrum capacity by allowing all users to occupy all channels at the same time. Transmissions are spread over the whole radio band, and each voice or data call are assigned a unique code to differentiate from the other calls carried over the same spectrum. CDMA allows for a soft hand-off , which means that terminals can communicate with several base stations at the same time. The dominant radio interface for third-generation mobile, or IMT-2000, will be a wideband version of CDMA with three modes (IMT-DS, IMT-MC and IMT-TC).
What is 3G?
"3G" stands for the "third generation" of mobile phones. Basically, a 3G device will provide a huge range of new functionality to your mobile. Up until now, your mobile phone has mainly been used only to carry voice messages, with maybe a bit of SMS text as well. 3G will allow simultaneous transfer of speech, data, text, pictures, audio and video.
A 3G device will blur traditional boundaries of technology - computing, communications, and consumer devices. Your 3G device will be your PC, your phone, and your PDA all in one. It would not be too much of an exaggeration to say that people will live their lives around their 3G devices. You'll have the world at your fingertips: anything, anytime, anywhere (hence, 3G has been called Martini-flavoured!).
3G will provide:
Â¢ High-speed, mobile access to the Internet.
Â¢ Your choice of entertainment on demand. This will include movies (on the device's high-resolution screen) and music (on the device's in-built MP3 player).
Â¢ Video-conferencing (using the device's in-built micro video camera).
Â¢ Mobile shopping (m-commerce). Browse available items and pay using electronic cash.
Â¢ Travel information: congested roads, flight departures. And if you get lost, find your current location. Also get location services, e.g., suggesting nearby restaurants. In the U.S., when an emergency call (911) is made from a cellular phone the user's location can now be traced (so-called Enhanced 911, or E-911).
Â¢ You could always use it as a phone
3G brings together two powerful forces: wideband radio communications and IP-based services. Together, these lay the groundwork for advanced Mobile Internet services, including personalized portals, "infotainment", mobile commerce and unified messaging -encompassing high-speed data, superior quality voice and video and location-based services.
3G wireless networks are capable of transferring data at speeds of up to 384Kbps. Average speeds for 3G networks will range between 64Kbps and 384Kbps, quite a jump when compared to common wireless data speeds in the U.S. that are often slower than a 14.4Kb modem. 3G is considered high-speed or broadband mobile Internet access, and in the future 3G networks are expected to reach speeds of more than 2Mbps. The immediate goal is to raise transmission speeds from 9.5K to 2M bit/sec.
3G technologies are turning phones and other devices into multmedia players, making it possible to download music and video clips. The new service is called the freedom of mobile multimedia access (FOMA), and it uses wideband code division multiple access (W-CDMA) technology to transfer data over its networks. W-CDMA sends data in a digital format over a range of frequencies, which makes the data move faster, but also uses more bandwidth than digital voice services. W-CDMA is not the only 3G technology; competing technologies include CDMAOne, which differs technically, but should provide similar services. FOMA services are available in a 20-mile radius around the center of Tokyo, the company plans to introduce it to other Japanese cities by the end of the year. But services and phones are expensive and uptake of this market is expected to be slow
Here is a simple introduction to some aspects of 3G radio transmission technologies (RTTs). The subjects covered in this section will be useful when we come to the more detailed discussions in the later sections on 3G Standards and 3G Spectrum.
Simplex vs. Duplex
When people use walkie-talkie radios to communicate, only one person can talk at a time (the person doing the talking has to press a button). This is because walkie-talkie radios only use one communication frequency - a form of communication known as simplex:
Of course, this is not how mobile phones work. Mobile phones allow simultaneous two-way transfer of data - a situation known as duplex (if more than two data streams can be transmitted, it is called multiplex):
Duplex: Allows simultaneous two-way data transfers.
The communication channel from the base station to the mobile device is called the downlink, and the communication from the mobile device back to the base station is called the uplink. How can duplex communication be achieved? Well, there are two possible methods which we will now consider: TDD and FDD.
TDD vs. FDD
Wireless duplexing has been traditionally implemented by dedicating two separate frequency bands: one band for the uplink and one band for the downlink (this arrangement of frequency bands is called paired spectrum). This technique is called Frequency Division Duplex, or FDD. The two bands are separated by a "guard band" which provides isolation of the two signals:
FDD: Uses paired spectrum - one frequency band for the uplink, one frequency band for the downlink.
Duplex communications can also be achieved in time rather than by frequency. In this approach, the uplink and the downlink operate on the same frequency, but they are switched very rapidly: one moment the channel is sending the uplink signal, the next moment the channel is sending the downlink signal. Because this switching is performed very rapidly, it does appear that one channel is acting as both an uplink and a downlink at the same time. This is called Time Division Duplex, or TDD. TDD requires a guard time instead of a guard band between transmit and receive streams.
Symmetric Transmission vs. Asymmetric Transmission
Data transmission is symmetric if the data in the downlink and the data in the uplink is transmitted at the same data rate. This will probably be the case for voice transmission - the same amount of data is sent both ways. However, for internet connections or broadcast data (e.g., streaming video), it is likely that more data will be sent from the server to the mobile device (the downlink).
FDD transmission is not so well suited for asymmetric applications as it uses equal frequency bands for the uplink and the downlink (a waste of valuable spectrum). On the other hand, TDD does not have this fixed structure, and its flexible bandwidth allocation is well-suited to asymmetric applications, e.g., the internet. For example, TDD can be configured to provide 384kbps for the downlink (the direction of the major data transfer), and 64kbps for the uplink (where the traffic largely comprises requests for information and acknowledgements).
Macro Cells, Micro Cells, and Pico Cells
The 3G network might be divided up in hierarchical fashion:
Â¢ Macro cell - the area of largest coverage, e.g., an entire city.
Â¢ Micro cell - the area of intermediate coverage, e.g., a city centre.
Â¢ Pico cell - the area of smallest coverage, e.g., a "hot spot" in a hotel or airport.
Why is there this sub-division of regions? It is because smaller regions (shorter ranges) allow higher user density and faster transmission rates. This is why they are called "hot spots".
TDD mode does not allow long range transmission (the delays incurred would cause interference between the uplink and the downlink). For this reason, TDD mode can only be used in environments where the propagation delay is small (pico cells). As was explained in the previous section on symmetric transmission vs. asymmetric transmission, TDD mode is highly efficient for transmission of internet data in pico cells.
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:
1. chopped into pieces (packets),
2. given a destination address,
3. mixed with other data from other sources,
4. transmitted over a line with all the other data,
5. 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.
Cellular Standards for 1G and 2G
Each generation of mobile communications has been based on a dominant technology, which has significantly improved spectrum capacity. Until the advent of IMT-2000, cellular networks had been developed under a number of proprietary, regional and national standards, creating a fragmented market.
1) Advanced Mobile Phone System (AMPS) was first launched in the US. It is an analog system based on FDMA (Frequency Division Multiple Access) technology. Today, it is the most used analog system and the second largest worldwide.
2) Nordic Mobile Telephone (NMT) was mainly developed in the Nordic countries. (4.5 million in 1998 in some 40 countries including Nordic countries, Asia, Russia, and other Eastern European Countries)
3) Total Access Communications System (TACS) was first used in the UK in 1985. It was based on the AMPS technology.
There were also a number of other proprietary systems, rarely sold outside the home country
1) Global System for Mobile Communications (GSM) was the first commercially operated digital cellular system. It was first developed in the 1980s through a pan-European initiative, involving the Eureopean Commission, telecommunications operators and equipment manufacturers. The European Telecommunications Standards Institute was responsible for GSM standardization. GSM uses TDMA (Time Division Multiple Access) technology. It is being used by all European countries, and has been adopeted in other continents. It is the dominant cellular standard today, with over (45%) of the worldâ„¢s subscribers at April 1999.
2) TDMA IS-136 is the digital enhancement of the analog AMPS technology. It was called D-AMPS when it was fist introduced in late 1991 and its main objective was to protect the substantial investment that service providers had bmade in AMPS technology. Digital AMPS sevices have been launched in some 70 countries worldwide (by March 1999, there were almost 22 million TDMA handsets in circulation, the dominant markets being the Americas, and parts of Asia)
3) CDMA IS-95 increases capacity by using the entire radio band with each using a unique code (CDMA or Code Division Multiple Access) . It is a family of digital communication techniques and South Korea is the largest single CDMA IS-95 market in the world.
4) Personal Digital Cellular (PDC) is the second largest digital mobile standard although it is exclusively used in Japan where it was introduced in 1994. Like GSM, it is based on the TDMA access technology. In November 2001, there were some 66.39 million PDC users in Japan.
5) Personal Handyphone System (PHS) is a digital system used in Japan, first launched in 1995 as a cheaper alternative to cellular systems. It is somewhere in between a cellular and a cordless technology. It has inferior coverage area and limited usage in moving vehicles. In November 2001, Japan had 5.68 million PHS subscribers.
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 (see the previous section on 3G Technology for an explanation of 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 (see here).
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"(!) (see here). 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 (see here)
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, considered later).
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.
Cellular Standards for the Third Generation: The ITU's IMT-2000 family
It is in the mid-1980s that the concept for IMT-2000, International Mobile Telecommunications, was born at the ITU as the third generation system for mobile communications. After over ten years of hard work under the leadership of the ITU, a historic decision was taken in the year 2000 : unanimous approval of the technical specifications for third generation systems under the brand IMT-2000. The spectrum between 400 MHz and 3 GHz is technically suitable for the third generation. The entire telecommunication industry, including both industry and national and regional standards-setting bodies gave a concerted effort to avoiding the fragmentation that had thus far characterized the mobile market. This approval meant that for the first time, full interoperability and interworking of mobile systems could be achieved. IMT-2000 is the result of collaboration of many entities, inside the ITU (ITU-R and ITU-T), and outside the ITU (3GPP, 3GPP2, UWCC and so on)
IMT-2000 offers the capability of providing value-added services and applications on the basis of a single standard. The system envisages a platform for distributing converged fixed, mobile, voice, data, Internet and multimedia services. One of its key visions is to provide seamless global roaming, enabling users to move across borders while using the same number and handset. IMT-2000 also aims to provide seamless delivery of services, over a number of media (satellite, fixed, etcÂ¦). It is expected that IMT-2000 will provide higher transmission rates: a minimum speed of 2Mbit/s for stationary or walking users, and 348 kbit/s in a moving vehicle. Second-generation systems only provide speeds ranging from 9.6 kbit/s to 28.8 kbit/s.
In addition, IMT-2000 has the following key characteristics:
With the large number of mergers and consolidations occurring in the mobile industry, and the move into foreign markets, operators wanted to avoid having to support a wide range of different interfaces and technologies. This would surely have hindered the growth of 3G worldwide. The IMT-2000 standard addresses this problem, by providing a highly flexible system, capable of supporting a wide range of services and applications. The IMT-2000 standard accommodates five possible radio interfaces based on three different access technologies (FDMA, TDMA and CDMA):
There was agreement among industry that 3G systems had to be affordable, in order to encourage their adoption by consumers and operators.
3. Compatibility with existing systems
IMT-2000 services have to be compatible with existing systems. 2G systems, such as the GSM standard (prevalent in Europe and parts of Asia and Africa) will continue to exist for some time and compatibility with these systems must be assured through effective and seamless migration paths.
4. Modular Design
The vision for IMT-2000 systems is that they must be easily expandable in order to allow for growth in users, coverage areas, and new services, with minimum initial investment
The 3G standard created by the International Telecommunication Union (ITU) 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:
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 - which will now be covered in more detail:
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. For a paper on the technical aspects of UMTS,
The terrestrial part of UMTS (i.e., non-satellite) is known as UTRA (UMTS Terrestrial Radio Access - don'tcha just love acronyms made from other acronyms!). The FDD component of UTRA is based on the W-CDMA standard (a.k.a. UTRA FDD). This offers very high (theoretical!) data rates up to 2Mbit/sec (the rumour is that the achievable rate is far lower: W-CDMA systems have been plagued with technical difficulties). 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).
"3" from Hutchison 3G
In the UK, Hutchison 3G have just launched their UMTS-based service called, simply, 3 (see their snazzy logo above). At first, they say this will cover around 40 percent of the UK population (i.e., Greater London ... cynical ed.).
They are pushing video calls as their "killer app", with person-to-person calls possible possible from day one. A "walled garden" approach has been taken to content downloadable from the Internet - you can only get content from 3's partners. You can't just browse the Internet and download what you want. 3 say they are doing this to ensure the content (e.g., video) is optimised for the handset. 3's content partners include the FA Premier League (you can download 30-second clips of Premiership goals), Reuters, and the people who made Wallace and Gromit.
The first 3G phones in Britain will be the e606 and e808 from NEC, and the A830 from Motorola. Read Funkyberry's trip to the 3 shop in Oxford Street.
NTT DoCoMo has gone live with 3G in Tokyo. Its service is called FOMA. This is the world's first IMT-2000 W-CDMA service (there are small but significant differences between the Japanese and European versions of W-CDMA - nothing is ever simple in 3G).
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), and this can be upgraded to phase two, 3XRTT (2Mbps) (also known as 3X).
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. Verizon has launched CDMA2000 1X in major east and west coast markets in the US (their so-called Wireless Express), and are starting trials of 1X EV-DO in the Washington, D.C. area.
Sprint have just launched the first nationwide CDMA2000 1X service called PCS Vision. This service allows the user to play games, transmit digital photos, and surf the web on a wide range of funky devices.
The UMTS standard also contains another radio transmission standard which is rarely mentioned: TD-CDMA (a.k.a. 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 (see the previous section on 3G Technology for an explanation of TDD and FDD). 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 elimates 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.
TD-SCDMA will not have it all its own way in China: it may find it difficult to compete with W-CDMA and CDMA2000, unless Chinese politics plays a part.
Imagine you are out doing some errands on a weekend evening and want to get together with some friends for a movie and dinner. If it's a Saturday night, the chances are once you get to the theater there will be long lines, sold out shows for the movie you want to see, and a bunch of other movies playing of which you've never heard.
But you have an advantage over others. You pull out your new cell phone with its enhanced screen, which happens to double as your personal digital device. Using the snazzy wireless device, you not only can check the listing of all the movies at the theater, you can view clips from the movies as well. Using this same device, you select the movie you want to see, buy the tickets online, and then use the instant messaging function to let your friends who are meeting you know which movie you have selected.
Also, since you know that the restaurant across the street is going to be busy after the movie, you make reservations for you and your friends. After the show, once you and your friends get to the restaurant, you call up on your wireless phone the restaurant's discount coupon and pay for dinner - avoiding using cash or a credit card. Welcome to the world of Third Generation wireless (3G) - where high-speed, broadband mobility meets the Internet.
Currently, it's difficult to even imagine the implications for electronic commerce in economies that develop broadband mobile access to the Internet and data services that make the above scenario possible. With 3G, the possibilities for wireless applications are numerous. For instance, imagine calling up a map in your car, conducting a video conference over wireless phones, checking e-mails, and browsing the web - all without wires.
The availability of 3G services is going to have a profound affect on electronic commerce. In terms of international competitiveness, the 3G race has gotten off to a staggering start. The U.S. is in one lane continuing to analyze the need for additional spectrum to complement our current cellular and PCS spectrum usages. Japan is in another lane and is expected to rollout its 3G services in May 2001. And several other Asian and European countries are well on their way toward implementing 3G as they have already issued licenses and will be rolling out 3G services throughout the coming year.
Mobile broadband wireless Internet access has become a key economic component for Asian and European countries and many of those nations are on the cusp of driving the next wave of the Internet revolution: mobile commerce ("m-commerce"). The advent of mobile broadband communications is not only going to change dramatically the number of people who are accessing and using the Internet, but will change the content of the Internet.
3G operators are planning to make their money with mobile applications even when there might never be a single killer application. According to the Report 9 from UMTS Forum near-term 3G data services are subdivided into content connectivity and mobility, then further subdivided to create the following six services:
Â¢ Customized Infotainment
Â¢ Multimedia Messaging Service
Â¢ Mobile Intranet/Extranet Access
Â¢ Mobile Internet Access
Â¢ Location-based Services
Â¢ Rich Voice
According to a whitepaper form Nokia, 3G applications can be divided into:
Â¢ Wireless Advertising
Â¢ Mobile Information
Â¢ Business Solutions
Â¢ Mobile Transactions
Â¢ Mobile Entertainment
Â¢ Person-to-Person Communications
Â¢ Bearer Entrance and Periodics
Basically, 3G opens the door to anything you can imagine. You will be able to do a multitude of things while going through your daily schedule, whether at work or at leisure. The scenarios below demonstrate just a few applications for 3G and only hint at what will be on offer in the future.
3G - At home
3G is going to affect our home and social lives in many ways. The services that 3G enables will help us to manage our personal information, simplify tasks such as grocery shopping, make better use of our time and offer services that are just fun to use. Operators will be able to develop myriad new service opportunities to attract and retain new customers. Here are some examples:
Â¢ You're sitting on a train and use this "dead" time to log on to your bank account, check your balance and pay a few bills - all through your 3G device. You save time and can be smarter about managing your finances.
Â¢ On a touring vacation, you arrive in a new city. You haven't made any reservations in advance, because you can do this when you get there, by using your 3G handset to obtain up-to-date information, including hotel vacancies. Having booked a room, you can use your mobile to view video clips of local tourist attractions and talk to someone from the local tourist information bureau at the same time.
3G - At work
3G will not just support the needs of businesspeople who travel a lot, but will also help new, flexible working practices, such as home-working and remote access to corporate networks outside traditional working hours. Businesspeople are often high-volume airtime users, so they represent a big opportunity for mobile operators. Here are some examples:
Â¢ At work you receive a message from your "smart" refrigerator at home. The message tells you that certain items need restocking and an order has already been prepared for the local grocery store, which you can approve, so that your groceries are ready to collect on the way home.
Â¢ You are on the road, and urgently need to discuss a draft presentation with a number of colleagues back in the office. Pulling into a service station, you use your 3G device to hold a telemeeting with your colleagues and, at the same time, you can all view the draft presentation and make changes on line.
Â¢ A maintenance engineer is repairing some equipment on a client's premises and hits a problem. Using his 3G device, he contacts his department and downloads a demonstration video that guides him through the repair process
We're likely to see 3G services enter our day -to-day lives in all sorts of new ways: for example, in shopping, especially Internet "mail order" (e-commerce), banking, or playing interactive computer games over the Net.
Evolution to 3G Wireless Technology
Initially, 3G wireless technology will be deployed as "islands" in business areas where more capacity and advanced services are demanded. A complete evolution to 3G wireless technology is mandated by the end of 2000 in Japan (mostly due to capacity requirements) and by the end of 2001 in Europe. NTT DoCoMo is deploying 3G wireless services in Japan in the third quarter of 2000. In contrast, there is no similar mandate in North America and it is more likely that competition will drive the deployment of 3G wireless technology in that region. For example, Nextel Communications has announced that it will be deploying 3G wireless services in North America during the fourth quarter of 2000. The implementation of 3G wireless systems raises several critical issues, such as the successful backward compatibility to air interfaces as well as to deployed infrastructures.
Interworking with 2G and 2G+ Wireless Networks
The existence of legacy networks in most regions of the world highlights the challenge that communications equipment manufacturers face when implementing next-generation wireless technology. Compatibility and interworking between the new 3G wireless systems and the old legacy networks must be achieved in order to ensure the acceptance of new 3G wireless technology by service providers and end-users.
The existing core technology used in mobile networks is based on traditional circuit- witched technology for delivery of voice services. However, this traditional technology is inefficient for the delivery of multimedia services. The core switches for next-generation of mobile networks will be based on packet-switched technology which is better suited for data and multimedia services. Second generation GSM networks consist of BTS, BSC, MSC/VLR and HLR/AuC/EIR network elements. The interfaces between BTS, BSC and MSC/VLR elements are circuit-switched PCM. GPRS technology adds a parallel packet-switched core network. The 2G+ network consists of BSC with packet interfaces to SGSN, GGSN, HLR/AuC/EIR. The interfaces between BSC and SGSN network elements are either Frame Relay and/or ATM so as to provide reliable transport with Quality of Service (QoS).
3G wireless technology introduces new Radio Access Network (RAN) consisting of Node B and RNC network elements. The 3G Core Network consists of the same entities as GSM and GPRS: 3G MSC/VLR, GMSC, HLR/AuC/EIR, 3G-SGSN, and GGSN. IP technology is used end-to-end for multimedia applications and ATM technology is used to provide reliable transport with QoS. 3G wireless solutions allow for the possibility of having an integrated network for circuit-switched and packet-switched services by utilizing ATM technology. The BSC may evolve into an RNC by using add-on cards or additional hardware that is co-located. The carrier frequency (5Mhz) and the bands (2.5 to 5Ghz) are different for 3G wireless technology compared to 2G/2G+ wireless technology. Evolution of BSC to RNC requires support for new protocols such as PDCP, RRC, RANAP, RNSAP and NBAP. Therefore, BTS' evolution into Node B may prove to be difficult and may represent significant capital expenditure on the part of network operators. MSC evolution depends on the selection of a fixed network to carry the requested services. If an ATM network is chosen, then ATM protocols will have to be supported in 3G MSC along with interworking between ATM and existing PSTN/ISDN networks. The evolution of SGSN and GGSN to 3G nodes is relatively easier. Enhancements to GTP protocol and support for new RANAP protocol are necessary to support 3G wireless systems. ATM protocols need to be incorporated to transport the services. The HLR databases evolve into 3G-HLR by adding 3G wireless user profiles. The VLR database must also be updated accordingly. The EIR database needs to change to accommodate new equipment that will be deployed for 3G wireless systems. Finally, global roaming requires compatibility to existing deployment and graceful fallback to an available level when requested services are not available in the region. Towards this end, the Operator Harmonization Group (OHG) is working closely with 3G Partnership Projects (3GPP and 3GPP2) to come up with global standards for 3G wireless protocols.
3G services work together with existing ones
Today's mobile networks were originally optimized for voice traffic. To carry large amounts of data traffic quickly and cost-effectively improved radio interfaces will be needed, capable of providing higher-bandwidth connections to more users simulateously Wideband radio technology has been optimized for multimedia services and high-speed Internet access. It will also be very spectrum-efficient, helping make the most of available spectrum. Radio access for 3G will be provided in two ways: the addition of new wideband radio technology to make use of newly available radio spectrum; and the evolution of current radio technology to provide higher-speed capabilities. The International Telecommunications Union (ITU) recommendations for the IMT2000 standard for next-generation services, a data rate of 2Mbit/s indoors is envisaged. In the wide-area environment - on suburban streets, on the train or in the car, for example - IMT-2000 envisages a data rate of up to 384kbit/s.
Multi-band, multi-mode phones have already shown how innovative terminal design can make the frequency of the radio access an irrelevance for users of mobile setvices. In the same way, "2G/3G-capable" dual-mode phones will provide transparent access to services delivered over different radio networks. 3G coverage can be built out in line with market demand - as an overlay network, for example.
What is the effect of 3G?
Implementing 3G does not just mean standardizing a new radio interface. New techniques and evolution strategies for delivering 3G are needed for all levels of the network.
When the current mobile standards were developed, they were generally applied right across the network. A GSM network is GSM at the handset, radio communications and core network levels. Much the same goes for TDMA (ANSI-136 digital mobile standard) and cdmaOne (ANSI-95, a CDMA-based digital mobile standard). In the case of 3G, a different approach is being taken. There is one standardization process for the radio network and another for the core network. That is why, when the industry talks about 3G wideband Radio Transmission Technologies (RTTs), it is only the radio communications part of the network that is being discussed. The core network is being developed and standardized in parallel, and in many cases will be an evolution of today's core networks. There will be a core network that has transport "pipes" for information flow, nodes that route the traffic, and nodes where the services are located. The core network will also have connections to other wired and mobile networks, to provide interconnectivity with the global telecoms networks. Connected to this core network will be the mobile radio network, providing the wideband interface for users.
Strategies for migration to these 3G capabilities from today's GSM, cdmaOne and TDMA networks envisage that evolved and new wideband radio networks will be able to share a common core network. History and commercial reality dictate that 3G will need to be provided across a wide range of radio frequencies and techniques, switching platforms and transmission technologies. Once standards have been agreed, the focus will be on the services and applications rather than the technologies used to deliver them.
How will 3G standards look?
There will be a "family of standards" for 3G, covering new Radio Transmission Technology (RU).A number of proposals for the IMT-2000 3G standard were submitted to the ITU during 1998. Since this time, the industry and standards bodies have coordinated their efforts to harmonize the IMT-2000 candidates and arrive at a smaller set of standards. The Operators Harmonization Group (OHG) - a group of major operators from all parts of the world - has played a key role in this process, and agreed on a set of standards in May 1999.
Where is the new radio spectrum?
International standards and regulatory bodies have set aside radio frequency in the 2GHz band.In 1992, the World Administrative Radio Conference (WARC) allocated 230MHZ of new radio spectrum to terrestrial and satellite services. Of this, the ITU has set aside 155MHZ in the 2GHZ band for terrestrial 3G services, as shown in the chart. Spectrum has been allocated in Europe and Japan in two 2GHZ bands, close to those recommended by the ITU, to meet these requirements. In the USA, much of the lower 2GHZ band allocated for IMT-2000 at WARC has been consumed by PCS spectrum allocations.
Radio spectrum this means a range of radio frequencies. The bandwidth of a radio signal is defined as being the difference between the upper and lower frequencies of the signal. For example, in the case of a voice signal having a minimum frequency of 300 hertz (Hz) and a maximum frequency of 3,300 Hz, the bandwidth is 3,000 Hz (3 KHz).
The amount of bandwidth needed for 3G services could be as much as 15-20 MHz. Compare this with the bandwidth of 30-200 KHz used for current 2G communication and you can see that there is as much as a 500-fold increase in the amount of bandwidth required. Now you can appreciate why radio spectrum has become such a precious and scarce resource in the information age - everybody from television broadcasters to the military wants spectrum, and it is in short supply. Michael Powell, the chairman of the U.S. Federal Communications Commission (FCC), has suggested that spectrum demand "is going to forever outstrip supply". The telecoms operators have had to buy 3G spectrum from governments around the world, and those governments - realising that they own a precious, valuable resource - have sought to sell that spectrum at the highest possible price.
Radio spectrum is often organised (and sold) as paired spectrum - a bit of spectrum in a lower frequency band, and a bit of spectrum in an upper frequency band (see the earlier section on 3G Technology for an explanation of paired spectrum). Paired spectrum is often specified in a form like "2x15MHz" meaning 15MHz in a lower band and 15MHz in an upper band. This technique of two users talking to each other on two separate frequencies is called Frequency Division Duplex, or FDD (see the earlier section on 3G Technology for an explanation of FDD). W-CDMA is an FDD technique (i.e., it requires paired spectrum) whereas TD-CDMA is a TDD technique (i.e., it can use unpaired spectrum).
CDMA2000 1X is very flexible in its spectrum requirements being designed to operate on all existing allocated spectrum for wireless communications. Unfortunately, the same cannot be said for UMTS which is quite specific about its spectrum requirements (this has resulted in the recent European bidding wars for UMTS spectrum). It has been suggested that choosing the rigid spectrum requirement for UMTS was a political move, aimed at creating a new export engine for Europe. CDMA2000's spectrum flexibility is one reason why the operational 3G systems have so far used CDMA2000 1X (also because CDMA2000 systems are being implemented on existing CDMA (CDMAone) networks).
UMTS specifies the bands 1900-2025 MHz and 2110-2200 MHz for 3G transmission. The satellite service uses the bands 1980-2010 MHz (uplink), and 2170-2200 MHz (downlink). This leaves the 1900-1980 MHz, 2010-2025 MHz, and 2110-2170 MHz bands for terrestrial UMTS (see the diagram below):
Diagram based on UK Official Licence Auction Site: Information Memorandum (3G Mobile Appendix)
As can be seen from the diagram, UMTS FDD is designed to operate in paired frequency bands, with uplink in the 1920-1980 MHz band, and downlink in the 2110-2170 MHz band. UMTS TDD is left with the unpaired frequency bands 1900-1920 MHz, and 2010-
As has just been explained, in Europe and Asia the choice of frequency band for implementing UMTS was clear. However, these frequency bands were not available in the U.S., so at the World Radio Conference (WRC-2000) in Instanbul, Turkey in May 2000, three frequency bands were suggested for implementing UMTS in the United States. The bands suggested were:
Â¢ the 806-890 MHz band (now being used for cellular and other mobile services),
Â¢ the 1710-1885 MHz band (largely used by the U.S. Department of Defense),
Â¢ the 2500-2690 MHz band (used by commercial users for instructional TV and wireless data providers).
As you can see, the problem for the U.S. was that all of the suggested bands were currently being used for other purposes. This was a worry for the U.S. - would this prove to be a major hindrance for the adoption of 3G in the U.S., thus allowing Europe and Asia to take the lead? As a result, on October 13th, 2000, President Clinton issued a Presidential Memorandum which initiated a study into the availability of extra spectrum in the USA.
On March 30th, 2001, the FCC produced their final report into the possibility of using the 2500-2690 MHz band for 3G transmission Basically, they thought that the TV industry was very heavily entrenched in this band and it would take between $10.2 billion and $30.4 billion to relocate the incumbent users.
The NTIA (National Communications and Information Administration) was given the task of evaluating the 1755-1850 MHz band for possible 3G transmission .A new plan, known as the "3G Viability Assessment", was proposed to consider the availability of the 1710-1770 MHz band, and the 2110-2170 MHz band. The result of that assessment is that 45MHz of space in the 1710-1755 MHz band and 45 Mhz of space in the 2110-2170 band is to be made available for 3G services.
The Radio Frequency Spectrum
300MHz - 600MHz NMT 450 Nordic Mobile Telephone System
TV Terrestrial Television, analog and didital
600MHz - 1.5GHz GSM900 Global System for Mobile Communications
GRRS General Packet Radio Service
CT-1 Cordless Telephone
GPS Global Positioning System
1.5GHz - 3GHz GSM1800 Global System for Mobile Communications
DECT Digital Enhanced Cordless Telephone System
3G UMTS Univeral Mobile Telecommunications System
WLAN Wireless Local Area Network
3GHz - 6GHz Hiperlan High Performance Local Area Network
FWA Fixed Wireless Access
Comparison of 2G, 2.5G and 3G Mobile Networks
The technology of most current digital mobile phones
- Phone calls
- Voice mail
- Receive simple email messages
Time to download a 3min MP3 song:
The best technology now widely available
- Phone calls/fax
- Voice mail
-Send/receive large email messages
- Web browsings
- New updates
Time to download a 3min MP3 song:
Combines a mobile phone, laptop PC and TV
- Phone calls/fax
- Global roaming
- Send/receive large email messages
- High-speed Web
- TV streaming
- Electronic agenda meeting reminder.
Time to download a 3min MP3 song:
3G System Capabilities
Capability to support circuit and packet data at high bit rates:
- 144 kilobits/second or higher in high mobility (vehicular) traffic
- 384 kilobits/second for pedestrian traffic
- 2 Megabits/second or higher for indoor traffic
Interoperability and roaming
Common billing/user profiles:
- Sharing of usage/rate information between service providers
- Standardized call detail recording
- Standardized user profiles
Capability to determine geographic position of mobiles and report it to both the network and the mobile terminal
Support of multimedia services/capabilities:
- Fixed and variable rate bit traffic Bandwidth on demand
- Asymmetric data rates in the forward and reverse links
- Multimedia mail store and forward
- Broadband access up to 2 Megabits/second
Key features of 3G systems are a high degree of commonality of design worldwide, compatibility of services, use of small pocket terminals with worldwide roaming capability, Internet and other multimedia applications, and a wide range of services and terminals.
How do 3G phones work?
As technology develops it gets harder and harder to work out what has changed when a new gadget or widget goes on sale.
This is especially true of mobile phones. The first mobile phones were as bulky portable and attractive as a breeze block.
Now they are all slinky, shiny and interchangeable. The improvements made to each one only become clear when you start to use them.
Third-generation, or 3G, networks are going to continue this trend. The phones will look the same as ever but the uses to which they can be put will simply explode.
In the old days, when all phones were fixed rather than mobile, making a call involved establishing a direct electrical connection between your handset and the one you were calling.
The same happens with GSM mobiles, but instead of setting up a dedicated circuit, a small portion of the airwaves are reserved for your call.
This is a really bad way of dividing up the available airwaves because it means that the spaces and pauses in speech get the same priority as the words.
3G networks change all this. Instead of reserving airspace each conversation is chopped up into packets, each one of which is labelled with a code denoting which dialogue it is from.
Using packets of information to carry voice and data also means that your phone is effectively always connected to the network. This means that SMS messages, e-mails, video clips, or whatever can be delivered any time, you don't have to dial-up to check mail.
This will mean a huge change in the way that you pay for your phone. Mobile operators will have to stop charging on the basis of talk time and move to a model based on the packets you download or a single charge per month covering anything and everything you do.
The move to 3G networks means you will be able to do many more things with your mobile phone. It could become a wallet holding train or cinema tickets, discount vouchers for shops or even a key to unlock your house.
All these extra tasks will put something of a burden on the handset. At the moment screens on phones are small, they are difficult to type or get data into and they typically only work with one mobile phone technology.
Third-generation networks might require bigger screens, especially if you download video clips, better ways to move data in and out of them, and bigger memories if you want to carry your MP3 files with you.
The handsets themselves are likely to get slightly bigger to hold batteries to support these new uses and to include chipsets for existing mobile networks as well as the new ones.
Until UMTS is ubiquitous you'll be forced to use the best network available in your location. Because the cells that make up 3G networks are much smaller than those of existing network technologies you could be stuck with your 2G phone outside the big cities.
The day of 3G may be dawning but it will be a long time before the sun sets on our existing mobile phones.
What You Can Do With 3G Phones
You can download video footage, save and view it over and over again. This could be a football goal or pop video. You can also see and hear your friends if they have a 3G phone too.
You can take and send pictures to your friends and colleagues faster than ever before. A 3G phone is 30 times quicker than a GPRS phone.
You can play even faster and better ganes with a 3G phone. A 3G phone is 30 times quicker than a GPRS phone.
You have access to location based services which can show you where you are, how to find a recommended service or place e.g. a cinema.
Watch TV On Your 3G Phone
Already in Korea users have access to TV channels via their 3G phones.
The 3rd Generation Partnership Project (3GPP) is a collaboration agreement that was established in December 1998. The collaboration agreement brings together a number of telecommunications standards bodies which are known as Organizational Partners. The current Organizational Partners are ARIB, CCSA, ETSI, T1, TTA, and TTC.
The establishment of 3GPP was formalized in December 1998 by the signing of the The 3rd Generation Partnership Project Agreement.
The original scope of 3GPP was to produce globally applicable Technical Specifications and Technical Reports for a 3rd Generation Mobile System based on evolved GSM core networks and the radio access technologies that they support (i.e., Universal Terrestrial Radio Access (UTRA) both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes). The scope was subsequently amended to include the maintenance and development of the Global System for Mobile communication (GSM) Technical Specifications and Technical Reports including evolved radio access technologies (e.g. General Packet Radio Service (GPRS) and Enhanced Data rates for GSM Evolution (EDGE)).
The discussions that led to the signing of the 3GPP Agreement were recorded in a series of slides called the Partnership Project Description that describes the basic principles and ideas on which the project is based. The Partnership Project Description has not been maintained since itâ„¢s first creation but the principles of operation of the project still remain valid.
In order to obtain a consolidated view of market requirements a second category of partnership was created within the project called Market Representation Partners.
Observer status is also possible within 3GPP for those telecommunication standards bodies which have the potential to become Organizational Partners but which, for various reasons, have not yet done so.
A permanent project support group called the Mobile Competence Centre (MCC) has been established to ensure the efficient day to day running of 3GPP. The MCC is based at the ETSI headquarters in Sophia Antipolis, France.
How do 3G phones work?
3G.IP was a group of Operators and Vendors that shared a common 3G Network architecture strategy 3G.IP was an Operator-lead initiative 3GPP contributions from 3G.IP members resulted in successful completion of Release 5 of Internet Multimedia Subsystem (IMS) in 3GPP, in 2002.
This article offers an introduction to 3G radio transmission technologies and various functionalities of 3G device. A qualitative comparison of mobile wireless technologies that could be viewed simultaneously as substitute and/or complementary paths for evolving to broadband wireless access. The goal of the analysis is to explore the future of wireless access and to speculate on the likely success and possible interactions between the mobile technologies in the future. Successful implementation, adoption, and overall acceptance of the 3G wireless networks depends largely on the ability of these new mobile networks to interface and inter-work with the existing 2G and legacy networks currently deployed worldwide.3G is a class apart from other older generations. It would blur the traditional boundaries of technologies- computing, communication and consumer devices. Letâ„¢s hope that 3G technology will come up world wide, providing users with global roaming
Â¢ Encarta Encyclopedia
Â¢ Britannica Encyclopedia