Know About 4G Mobiles
4G refers to the fourth generation of cellular wireless standards. It is a successor to 3G and 2G standards, with the aim to provide a wide range of data rates up to ultra-broadband (gigabit-speed) Internet access to mobile as well as stationary users.
A 4G cellular system must have target peak data rates of up to approximately 100 Mbits/s for high mobility such as mobile access and up to approximately 1 Gbits/s for low mobility such as nomadic/local wireless access, according to ITU requirements. Scalable bandwidths up to at least 40 MHz should be provided. A 4G system is expected to provide a comprehensive and secure all-IP based solution where facilities such as IP telephony, ultra-broadband Internet access, gaming services and HDYV streamed multimedia may be provided to users.
The pre-4G technology3GPP Long Term Evaluation (LTE) is often branded “4G”, but the first LTE release does not fully comply with the IMT-Advanced requirements. LTE has a theoretical net bitrate capacity of up to 100 Mbits/s in the downlink and 50 Mbits/s in the uplink if a 20MHz channel is used – and more if Multiple-input multiple-output (MIMO), i.e. antenna arrays, are used. Most major mobile carriers in the United States and several worldwide carriers have announced plans to convert their networks to LTE-service was opened in the two Scandinavian capitals Stockholm and Oslo on 14th December 2009, and branded 4G. The physical radio interface was at an early stage named High Speed OFDM Packet Access (HSOPA), now named Evolved UMTS Terrestrial Radio Access (E-UTRA).
4G Features
According to the members of the 4G working group, the infrastructure and the terminals of 4G will have almost all the standards from 2G to 4G implemented. Although legacy systems are in place to adopt existing users, the infrastructure for 4G will be only packet-based (all-IP). So,e proposals suggest having an open Internet platform. Technologies considered to be early 4G include : Flash-OFDM, the 802.16e mobile version of WiMax (also known as WiBro in South Korea), and HC-SDMA.
Access Schemes
Recently, new access schemes like Orthogonal FDMA (OFDMA), Single Carrier FDMA (SC-FDMA), Interleaved FDMA and Multi-Carrier CDMA (MC-CDMA) are gaining more importance for for the next generation systems. These are based on efficient FFT algorithm and frequency domain equalization, resulting lower number of multiplications per second. They also make it possible to control the bandwidth and form the spectrum in a flexible way. However, they require advanced dynamic channel allocation and traffic adaptive scheduling.
WiMax is using OFDMA in the downlink and in the uplink. For the next generation UMTS, OFDMA is used for the downlink.
These access schemes offer the same efficiencies as older technologies like CDMA. Apart from this, scalability and higher data rates can be achieved.