Overview
4G is the fourth generation of wireless technologies for the mobile telecommunications and mobile phone services. It is a successor of previous wireless technologies 2.5G and 3G. A 4G network can cover a whole city or country. A 4G system is expected to provide secure and complete IP-based solutions where services like ultra-broadband Internet access, Voice over IP telephony, streamed multimedia and online gaming may be provided to the users.
4G offers connectivity to devices over a wide area i.e. 4G standards are WAN standards.
The 4G technology is becoming the rising solution to drive new development of the industry, and further help transformational business models, novel partnership arrangements or foster state-of-the-art technology. ITU-R (ITU Radiocommunication Center) defined 4G as IMT-Advanced (International Mobile Telecommunication Advanced). The 4G technology will cover all the systems from various networks from public to private like ad hoc networks and operator-driven broadband networks to personal areas. The 4G systems will interoperate with previous wireless technologies 2G and 3G, as well as with broadband (digital) broadcasting systems. Additionally, 4G technologies will be entirely IP-based wireless network.
Objective
4G technology is developed to accommodate rate requirements and the quality of service (QoS) by further development of third generation applications like MMS (Multimedia Messaging Service), HDTV, mobile TV, mobile broadband access, video chats, etc. The 4G communication standards defined by the 4G working group are –
• The data transfer rate of 1 Gbps (Gigabits per second) while station and client are in fixed position, and 100 Mbps (Megabits per second) while the client moves at high speed relative to the station as defined by ITU-R.
• Providing the peak link spectral efficiency (the net bit rate divided by the bandwidth of a communication in hertz) of 6.75 bits/Hz in the uplink and 15 bits/Hz in the downlink.
• Smooth handoff (handoff in mobile telecommunications referred as the process of transferring the ongoing calls from one channel to another) in a heterogeneous network.
• Global roaming and seamless connectivity across multiple networks.
• Providing the flexible channel bandwidth between 5 MHz to 20 MHz.
• Providing wide range of information and services like video, data, pictures etc.
• It also supports IPv6, a version of Internet Protocol that is intended to succeed IPv4.
Access Schemes
• Frequency Division Multiple Access (FDMA) –It is a method where the frequency band (spectrum) is divided into sub-band or channels and then this sub-band is given to the users. FDMA uses more bandwidth for guard to avoid inter carrier interference. It allows only one user on the channel at any given time.
• Time Division Multiple Access (TDMA) – It makes use of the entire available frequency band, unlike FDMA. Rather than dividing the slots by frequency, it divides them by time. Each user is given a time slot; therefore, many users have different time slots and can use one frequency. TDMA is used for 2G and 3G networks, but it proved to be less efficient in handling the high data rate channels.
• Code Division Multiple Access (CDMA) - It uses the spread spectrum method whereby electromagnetic energy is spread to allow for a signal with a wider bandwidth. It was developed and used by the military. Contrasting FDMA, CDMA allows the users to use the full available spectrum at the same time.
• Orthogonal FDMA (OFDMA) – It also uses spread spectrum technique, which spreads the data over a lot of carriers that are distant from particular frequencies. This spacing prevents the demodulators or receivers from seeing frequencies other than their own particular one.
4G technology will be available from 2010, getting it right first time will make it a general winner with the one billion mobile users around the world. The end user can expect speed and reliability as well as low cost per data bit, something, which is very much required. It is not just the mobile networks that need to develop, the increased data traffic load on the IP network as a whole will need to expand, with faster backbones and oceanic links requiring major upgrade.