4G (Fourth Generation Networks)

4G or Fourth Generation is technology for mobile and wireless comunications. It will be the successor for the 3Rd Generation (3G) network technology. Currently 3G networks are under deployement. Approximatly 4G deployments are expected to be seen around 2010 to 2015.

The basic voice was the driver for second-generation mobile and has been a considerable success. Currently , video and TV services are driving forward third generation (3G) deployment. And in the future, low cost, high speed data will drive forward the fourth generation (4G) as short-range communication emerges. Service and application ubiquity, with a high degree of personalization and synchronization between various user appliances, will be another driver. At the same time, it is probable that the radio access network will evolve from a centralized architecture to a distributed one.

The evolution from 3G to 4G will be driven by services that offer better quality (e.g. multimedia, video and sound) thanks to greater bandwidth, more sophistication in the association of a large quantity of information, and improved personalization. Convergence with other network (enterprise, fixed) services will come about through the high session data rate. It will require an always-on connection and a revenue model based on a fixed monthly fee. The impact on network capacity is expected to be significant. Machine-to-machine transmission will involve two basic equipment types: sensors (which measure parameters) and tags (which are generally read/write equipment).

It is expected that users will require high data rates, similar to those on fixed networks, for data and streaming applications. Mobile terminal usage (laptops, Personal digital assistants, handhelds) is expected to grow rapidly as they become more user friendly. Fluid high quality video and network reactivity are important user requirements. Key infrastructure design requirements include: fast response, high session rate, high capacity, low user charges, rapid return on investment for operators, investment that is in line with the growth in demand, and simple autonomous terminals. The infrastructure will be much more distributed than in current deployments, facilitating the introduction of a new source of local traffic: machine-to-machine.


Technologies used in 4G:

1-Orthogonal Frequency Division Multiplexing (OFDM)

2-Software Defined Radio (SDR)

3-Multiple-input multiple-output ( MIMO )



Initially DoCoMo planned to introduce 4G services around 2010. Recently DoCoMo announced plans to introduce 4G services from 2006, i.e. four years earlier than previously planned. NTT DoCoMo, Inc. announced that high-speed packet transmission with 1 Gbps data rate in the downlink was achieved successfully in a laboratory experiment using fourth-generation (4G) mobile communication radio access equipments.



The key enablers for the 4G are:

1-Sufficient spectrum, with associated sharing mechanisms.

2-Coverage with two technologies: parent (2G, 3G, WiMAX) for real-time delivery, and discontinuous pico cell for high data rate delivery.

3-Caching technology in the network and terminals.

4-OFDM and MIMO.

5-IP mobility.

6-Multi-technology distributed architecture.

7-Fixed-mobile convergence (for indoor service).

8-Network selection mechanisms.

CDMA technology

CDMA (Code-Division Multiple Access) refers to any of several protocols used in so-called second-generation (2G) and third-generation (3G) wireless communications. As the term implies, CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands.

CDMA employs analog-to-digital conversion (ADC) in combination with spread spectrum technology. Audio input is first digitized into binary elements. The frequency of the transmitted signal is then made to vary according to a defined pattern (code), so it can be intercepted only by a receiver whose frequency response is programmed with the same code, so it follows exactly along with the transmitter frequency. There are trillions of possible frequency-sequencing codes, which enhances privacy and makes cloning difficult.

The CDMA channel is nominally 1.23 MHz wide. CDMA networks use a scheme called soft handoff, which minimizes signal breakup as a handset passes from one cell to another. The combination of digital and spread-spectrum modes supports several times as many signals per unit bandwidth as analog modes. CDMA is compatible with other cellular technologies; this allows for nationwide roaming.

The original CDMA standard, also known as CDMA One and still common in cellular telephones in the U.S., offers a transmission speed of only up to 14.4 Kbps in its single channel form and up to 115 Kbps in an eight-channel form. CDMA2000 and wideband CDMA deliver data many times faster