The article discusses 4th generation wireless basics. 4G mobile communication system,aims to provide an effective solution for the next generation mobile services. It introduced the advancements through 3G.
“If you can dream it, you can do it”, according to this we can leap 3G to 4G along its features and future trends in mobile technology. In wireless communication, mobile technology is advanced and in this system 4G is the latest at present.
Progressing from previous three generations, 4G mobile systems have been significantly improving in terms of interactive multimedia services. In this article, we have tried to cover technologies, architecture requirements, service requirements with advantages and additional application along with its future trends in 4G wireless system.
Introduction - Evolution of the Mobile Technology
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.
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. Amps ( Advance mobile phone system ) was first launched by US which is 1G mobile system. It is best on FDMA technology which allows users to make voice calls within one country.
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. GSM (Global system for mobile communication) was the first commercially operated digital cellular system which is based on TDMA.
Third generation –
3G systems promise faster communications services, including voice, fax and Internet, anytime and anywhere with seamless global roaming. ITU’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. 3G technology supports 144 Kbps bandwidth, with high speed movement (e.g.vehicles), 384 Kbps (e.g.on campus) & 2 Mbps for stationary (e.g.inbuilding )
Fourth generation –
At present the download speed for imode data is limited to 9.6 kbit/sec which is about 6 times slower than an ISDN (Integrated services digital network) fixed line connection. Recently, with 504i handsets the download data rate was increased 3-fold to 28.8kbps. However, in actual use the data rates are usually slower, especially in crowded areas, or when the network is "congested". For third generation mobile (3G, FOMA) data rates are 384 kbps (download) maximum, typically around 200kbps, and 64kbps upload since spring 2001. Fourth generation (4G) mobile communications will have higher data transmission rates than 3G. 4G mobile data transmission rates are planned to be up to 20 megabits per second.
Theory
Before understanding 4G, we must know what is 3G ? 3G iinitiative came from device manufactures, not from operators. In 1996 the development was initiated by Nippon Telephone & Telegraph (NTT) and Ericsson; in 1997 the Telecommunications Industry Association (TIA) in the USA chose CDMA as a technology for 3G; in 1998 the European Telecommunications Standards Institute (ETSI) did the same thing; and finally, in 1998 wideband CDMA (W-CDMA) and cdma2000 were adopeted for the Universal Mobile Telecommunications System (UMTS).
W-CDMA and cdma 2000 are two major proposals for 3G. In this CDMA the information bearing signal is multiplied with another fasterate, wider bandwidth digital signal that may carry a unique orthogonal code. W-CDMA uses dedicated time division multiplexing (TDM) whereby channel estimation information is collected from another signal stream. cdma2000 uses common code division multiplexing (CDM) whereby channel estimation information can be collected with the signal stream.
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.
Beyond 3G -
In the field of mobile communication services, the 4G mobile services are the advanced version of the 3G mobile communication services. The 4G mobile communication services are expected to provide broadband, large capacity, high speed data transmission, providing users with high quality color video images, 3D graphic animation games, audio services in 5.1 channels. We have been researching the vision of 4G mobile communication systems, services, and architectures. We also have been developing the terminal protocol technology for high capacity, high speed packet services, public software platform technology that enables downloading application programs, multimode radio access platform technology, and high quality media coding technology over mobile networks.
Reasons To Have 4G -
Support interactive multimedia services: teleconferencing, wireless Internet, etc.
- Wider bandwidths, higher bit rates.
- Global mobility and service portability.
- Low cost.
- Scalability of mobile networks.
As radio spectrum is the primary resource for wireless technologies, the main thrust of 4G research worldwide is directed towards spectrally efficient systems. New, powerful technology that emerged recently promise a tenfold improvement in spectral efficiency over existing solutions. These potential 4G tools and techniques include:
Advanced antenna technologies - Antenna arrays can add value to even 2G systems, where they are employed typically to solve capacity problems. However, major cost benefits can be obtained if they are designed into the system.
MIMO techniques - The benefit of array or multiple antennas for spatial diversity has long been realised. Yet only recently were they combined with advanced coding techniques to form extremely efficient MIMO (Multiple Input Multiple Output ) systems.
Adaptive and reconfigurable systems, software defined radio - These aim to approach the shannon capacity limit by optimising the modulation, coding power control etc to the varying transmission, include high orcer modulation, turbo coding or recently reported woven and low-density parity –check codes that match turbo codes for performance while being more easily implemented.
Wireless access technologies – OFDMA(Orthogonal Frequency-Division Multiple Access) and MC CDMA (Multiple carrier Code –Division Multiple Access) are the main contenders for future systems. Another, more radical access scheme for the downlink is a single queue packet-based system. Broadcast and cellular network convergence - Harnessing broadcast technology to carry high bandwidth downlink multicast data leads to improved spectral efficiency and creation of new business models for operators.
System architecture requirements -
Non-homogeneous infrastructure –
The infrastructure architecture is non-homogeneous, consisting of several switching fabrics and a multitude of physical media. All elements of significance are digital. The fixed backbone structure is dominated by connection-less packet switching (IP-style). Also the new air interfaces in wireless systems use packet switching technology. The wireless infrastructure consists uses a multitude of air interfaces, inherited from the wireless systems of the late 90’s and early year of the new millennium. Among the newer, packet oriented wireless systems for the high data rates in the 5 and 60 GHz system have emerged with data rates up to 100 Mbit/s for hand-portable use. An overlaid architecture will provide seamless, transparent internetworking using all kinds of air interfaces.
Public & private mixed -
Public Wireless access quality and bandwidth varies, where higher data rates 20 Mbit/s are confined to dense urban areas, office environments (private/public systems) and homes (private systems). Operators/service providers provide partial coverage for non-real-time wideband (10 Mbit/s) information access in most public places ("info-kiosk", infostations), in public transportation. Rural area information access bandwidth is limited to 1 Mbit/s but provides reasonable coverage along all main highways and villages of more than 100 inhabitants. Seamless transition from private networks to publicly operated systems is possible.
Ad-hoc, unlicenced operation domimates -
Many actors will provide parts of the infrastructure. Ad-hoc networking (spontaneous deployment, self planning) in unlicensed bands (the 5 and 60 GHz bands) will play an important role (the dominant role in the "pocket computing" and the "anything goes" scenarios) and compete fiercely with the existing traditional public operator which experience dwindling market shares. Techniques for efficient multi-operator (private/public) sharing of unlicensed spectrum have been developed. Ad-hoc structures, where the equipment of the users (companies or even individuals) provide part of the infrastructure, are adaptive to possible new communication patterns. Control of the new emerging ad-hoc networks (incl. routing, mobility etc.) is fully distributed and highly reliable.
Multimode access ports -
Access ports (base stations) in public systems are multi-mode with multiple access air interfaces to accommodate a wide range of terminals. Large operator systems use advanced access ports with adaptive antennas that self-configure with non-critical installation procedures (self-configuration) to reduce cost. The cost of base station equipment is negligible in comparison with the cost of planning and physical installation. Access ports (wireless gateways) in ad-hoc access systems are simple single mode/single air interface devices. 60GHz systems use adaptive antennas. The cost of access port hardware in these systems is negligible.
Service requirements -
Tele-presence -
The services provide 2010 range from mobile/untheatered "tele-presence" in office/dense urban environments to wide area interactive information services requiring large bandwidth, but not necessarily in real time. "Tele-presence" is used to create virtual meetings between individuals and provides full stimulation of all sense required to provide the illusion of actually being somewhere else - an illusion that cannot be distinguished from the "real thing". The bandwidth required for tele-presence is, with efficient data compression and fast sensory feedback, less than 100 Mbit/s. The data stream is mostly dominated by 180 degree stereo, hi-resolution, and full motion video). Meeting processes will be mainly real-time. Real-time communication is essential for the meeting processes and multicast is required for group communication. Multiple party meeting processes is one of the major communication patterns foreseen for this application.
Information anywhere, anytime -
Virtually seamless connection to a wide range of information services, anywhere, anytime is a key feature of the information infrastructure. Information access of large volumes of data, pictures, video etc is nearly instantaneous in small portable terminals. Compared to real-time meeting process, this application is less delay sensitive. Users can tolerate longer delay for the information that is not real time critical. Possibly high data rate are required for high volume data transfer applications such as video retrieval. Bulk data transmission requires a very high data rate. The traffic pattern is highly asymmetric with 50/1 ratios or more favoring the system-to-terminal links. Seamless virtual connections (creating the feeling of always being connected) is important for the users. Information provisioning is dominated by educational/recreational material.
Inter-machine communication -
Inter-machine communication is an important application/service, ranging from simple maintenance routines (e.g. refrigerator telling repair shop that it’s broken) to sophisticated massive data exchange (e.g. camera and PC/TV exchanging video/picture information). All cars, household and office equipment down to less than 20 US$ have wireless interface as standard feature.
Security of vital importance -
Security is an indispensable feature of the infrastructure. Data integrity and protection against unauthorized access are key features providing reliable services for banking, electronic payment and handling of personal information. Schemes that reliably prevent unauthorized tracking of users and other intrusions in the private sphere are in operation.
One-stop-shopping -
Services are provided in a one-stop fashion ("turn-key") directly to the consumer at the point of sales. Services are immediately available when leaving the store. The store (information provider) takes full responsibility for the service
New in 4G -
- Entirely packet-switched networks.
- All network elements are digital.
- Higher bandwidths to provide multimedia services at lower cost (up to 100Mbps).
- Tight network security.
- Adaptive array technology
- Ultra wide band technology
- Simulation and analysis of advanced adaptive modulations/coding schemes.
- Reconfigurable radio systems.
- Self- organising networks, end –to-end mobile IP and adaptive QoS. (Quality of Service)
- Simulation and analysis of MIMO techniques with multi-element array antennas at both ends of the link.
Conclusion –
4G the new technology will increase data transmission rates (up to 200 times faster than 2G at 20 Mbit/sec). 3G data rates are currently 2 Mbit/sec, which is very fast compared to 2G’s 9.6 Kbit/sec. 4G builds on the 3G standard, although it integrates and unifies the different interfaces (W-CDMA, cdma 2000, etc.)
As the advanced 4G infrastructure will be available and the inexpensive and attractive wireless,hand held devices will become popular, subscribers will begin enjoying instant wireless internet access.
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