4G TECHONOLOGY

4G TECHONOLOGY

Abstract:
Mobile devices are getting smaller, lighter, and more powerful; they have bigger screens and longer battery life, more features and more capabilities. Things like watching the football game on your mobile device, watching movies, videoconferencing, paying your bills and downloading music to the palm of your hand will become second nature in the near future.

Bandwidth will always be the limiting factor in the development of applications and devices, be it wired, or wireless. At the moment the wireless world doesn’t have a large-cell, high bandwidth standard, that is capable of delivering the much needed speeds to a mobile device. The short fall of 3G networks is clear, it’s just not fast enough, offering 384kbps doesn’t meet the requirements of what the end user has come to expect these days. Some people see 3G as a stop-gap, until a fully integrated IP network is created; some countries have even chosen to bypass 3G and head straight to 4G, a method which has its advantages, and its disadvantages.
A handful of wireless technologies are set to join existing 2.5G and 3G standards, , as 4G and NGN vendors find a foothold in the mobile market. “The current race is ultimately to wrestle control from the UMTS and CDMA2000 platforms,” Fuertes said. “Siemens carrying Flarion’s Flash-OFDM as announced last week is a large step forward for IP-based mobile wireless.”

Service Providers are considering new protocols in search of a migration to an all IP network, a move expected to lower high-speed data costs and enable new services. Some of these solutions are considered 3.5G or even 4G.

NEED FOR 4G:
4G is being developed to accommodate the QoS and rate requirements set by further development of existing 3G applications like wireless broadband access, Multimedia Messaging Service (MMS), video chat, mobile TV, but also new services like HDTV content, minimal services like voice and data, and other services that utilize bandwidth. It may be allowed roaming with wireless local area networks, and be combined with digital video broadcasting systems.

OBJECTIVES:
The 4G working group has defined the following as objectives of the 4G wireless communication standard:
• Flexible channel bandwidth, between 5 and 20 MHz, optionally up to 40 MHz.
• A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R,
• A data rate of at least 100 Mbit/s between any two points in the world,
• Peak link spectral efficiency of 15 bit/s/Hz in the downlink, and 6.75 bit/s/Hz in the uplink (meaning that 1000 Mbit/s in the downlink should be possible over less than 67 MHz bandwidth)
• System spectral efficiency of up to 3 bit/s/Hz/cell in the downlink and 2.25 bit/s/Hz/cell for indoor usage.
• Smooth handoff across heterogeneous networks,
• Seamless connectivity and global roaming across multiple networks,
• High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, etc)
• Interoperability with existing wireless standards, and
• An all IP, packet switched network.
Principal technologies
Physical layer transmission techniques
• No CDMA.
• MIMO: To attain ultra high spectral efficiency by means of spatial processing including multi-antenna and multi-user MIMO
• Frequency-domain-equalization, for example Multi-carrier modulation (OFDM) or single-carrier frequency-domain-equalization (SC-FDE) in the downlink: To exploit the frequency selective channel property without complex equalization.
• Frequency-domain statistical multiplexing, for example (OFDMA) or (Single-carrier FDMA) in the uplink: Variable bit rate by assigning different sub-channels to different users based on the channel conditions
• Turbo principle error-correcting codes: To minimize the required SNR at the reception side
• Channel-dependent scheduling: To utilize the time-varying channel.
• Link adaption: Adaptive modulation and error-correcting codes
• Relaying, including fixed relay networks (FRNs), and the cooperative relaying concept, known as multi-mode protocol
Components:
Access schemes:
Till now....:
As the wireless standards evolved, the access techniques used also exhibited increase in efficiency, capacity and scalability. The first generation wireless standards used plain TDMA and FDMA. In the wireless channels, TDMA proved to be less efficient in handling the high data rate channels as it requires large guard periods to alleviate the multipath impact. Similarly, FDMA consumed more bandwidth for guard to avoid inter carrier interference. So in second generation systems, one set of standard used the combination of FDMA and TDMA and the other set introduced an access scheme called CDMA. Usage of CDMA increased the system capacity, but as a drawback placed a soft limit on it rather than the hard limit (i.e. a CDMA network will not reject new clients when it approaches its limits, resulting in a denial of service to all clients when the network overloads). Data rate is also increased as this access scheme (providing the network is not reaching its capacity) is efficient enough to handle the multipath channel. This enabled the third generation systems, such as IS-2000, UMTS, HSXPA, 1xEV-DO, TD-CDMA and TD-SCDMA, to use CDMA as the access scheme. However, the issue with CDMA is that it suffers from poor spectral flexibility and computationally intensive time-domain equalization (high number of multiplications per second) for wideband channels.
Tomorrow....:
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 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. By contrast, IFDMA is being considered for the uplink since OFDMA contributes more to the PAPR related issues and results in nonlinear operation of amplifiers. IFDMA provides less power fluctuation and thus avoids amplifier issues. Similarly, MC-CDMA is in the proposal for the IEEE 802.20 standard. These access schemes offer the same efficiencies as older technologies like CDMA. Apart from this, scalability and higher data rates can be achieved.
The other important advantage of the above mentioned access techniques is that they require less complexity for equalization at the receiver. This is an added advantage especially in the MIMO environments since the spatial multiplexing transmission of MIMO systems inherently requires high complexity equalization at the receiver.In addition to improvements in these multiplexing systems, improved modulation techniques are being used. Whereas earlier standards largely used Phase-shift keying, more efficient systems such as 64QAM are being proposed for use with the 3GPP Long Term Evolution standards.
How OFDM works
First of all the FDM part - Frequency division multiplexing is a technology that transmits several signals at the same time over a single transmission path, in a medium such as a cable or wireless system. Each signal is transmitted inside its own unique frequency range (the carrier frequency), which is then modulated by the data that is needing to be transmitted.

Orthogonal FDM's spread spectrum technique spreads the data over a lot of carriers that are spaced apart at precise frequencies. This spacing provides the "orthogonality" in this method which prevents the receivers/demodulators from seeing frequencies other than their own specific one. The main benefit of OFDM is high spectral efficiency, but with OFDM you also get; high resiliency to RF interference and the multi-path distortion is lower.
When OFDM was first implemented, it was by using banks of sinusoidal generators, e.g. just placing up a whole lot of single carriers in parallel. The use of the discrete Fourier transform (DFT) was originally proposed in 1971 by Weinstein and Ebert, which greatly reduces the implementation complexity of OFDM systems. This was further reduced by the development of the fast Fourier transform (FFT). Shortly after an equalization algorithm was implemented in order to help suppress both ISI and intersubcarrier interference, which is caused by the channel impulse response and timing and frequency errors.

In OFDM the sub carrier pulse which is used for transmission is rectangular. This is why the capability of pulse forming and modulation can be performed by an IDFT, which can be generated very efficiently as an IFFT. Because of this, the receiver only needs a FFT to reverse this process. Taking into account the theories of the Fourier Transform the rectangular pulse shape will end up as a sin(x)/x style of spectrum of the subcarriers. In traditional FDM the sub-channels aren’t orthogonal therefore need to be separated by guard bands which obviously wastes much needed spectrum.
Because an IIFT is used for modulation in OFDM, this spacing of the sub carriers is done in such a way the frequency where we evaluate the received signal all other signals are zero thus allowing the sub channels to overlap. But because of this, for an OFDM system to work using this method, the receiver and the transmitter must be in perfect synch, and there can’t be any multipath fading, which is unusual since finding a fix to this is one of the main goals of OFDM.

Luckily there is an easy way to solve this problem. If a guard interval is used, which is larger than the expected delay spread, which is done by artificially extending the symbol time and then removing this extension at the receiver, the problem is solved but with only a minimal loss in bandwidth.
IPv6 support
Unlike 3G, which is based on two parallel infrastructures consisting of circuit switched and packet switched network nodes respectively, 4G will be based on packet switching only. This will require low-latency data transmission.By the time that 4G is deployed, the process of IPv4 address exhaustion is expected to be in its final stages. Therefore, in the context of 4G, IPv6 support is essential in order to support a large number of wireless-enabled devices. By increasing the number of IP addresses, IPv6 removes the need for Network Address Translation (NAT), a method of sharing a limited number of addresses among a larger group of devices, although NAT will still be required to communicate with devices that are on existing IPv4 networks.As of June 2009, Verizon has posted specifications that require any 4G devices on its network to support IPv6.
Advanced Antenna Systems:
MIMO and MU-MIMO
The performance of radio communications depends on an antenna system, refer to smart or intelligent antenna. Recently, multiple antenna technologies are emerging to achieve the goal of 4G systems such as high rate, high reliability, and long range communications. In the early 90s, to cater the growing data rate needs of data communication, many transmission schemes were proposed. One technology, spatial multiplexing, gained importance for its bandwidth conservation and power efficiency. Spatial multiplexing involves deploying multiple antennas at the transmitter and at the receiver. Independent streams can then be transmitted simultaneously from all the antennas. This increases the data rate into multiple folds with the number equal to minimum of the number of transmit and receive antennas. This is called MIMO (as a branch of intelligent antenna). Apart from this, the reliability in transmitting high speed data in the fading channel can be improved by using more antennas at the transmitter or at the receiver. This is called transmit or receive diversity. Both transmit/receive diversity and transmit spatial multiplexing are categorized into the space-time coding techniques, which does not necessarily require the channel knowledge at the transmit. The other category is closed-loop multiple antenna technologies which use the channel knowledge at the transmitter..

4G wireless standards:
In September 2009 the technology proposals have been submitted to ITU-R as 4G candidates. Basically all proposals are based on two technologies:
* LTE Advanced standardized by the 3GPP;
* 802.16m standardized by the IEEE.
Considering the huge industry support for 3GPP based technologies such as LTE the vision of an almost unified global 4G standard might not be out of reach anymore. A first set of 3GPP requirements on LTE Advanced has been approved in June 2008. LTE Advanced will be standardized in 2010 as part of the Release 10 of the 3GPP specification. LTE Advanced will be fully built on the existing LTE specification Release 10 and not be defined as a new specification series.
Towards4G...

For 1 and 2G standards, bandwidth maximum is 9.6 kbit/sec, This is approximately 6 times slower than an ISDN (Integrated services digital network). Rates did increase by a factor of 3 with newer handsets to 28.8kbps. This is rarely the speed though, as in crowded areas, when the network is busy, rates do drop dramatically.

Third generation mobile, data rates are 384 kbps (download) maximum, typically around 200kbps, and 64kbps upload. These are comparable to home broadband connections.
Fourth generation mobile communications will have higher data transmission rates than 3G. 4G mobile data transmission rates are planned to be up to 100 megabits per second on the move and 1000gigbits per second stationary, this is a phenomenal amount of bandwidth, only comparable to the bandwidth workstations get connected directly to a LAN.
4G SYSTEMS:
There are major three types of systems in 4G technology, they are listed below as follows
1. 1. WiMAX
2. 2. LTE
3. UMB

WiMAX:
WiMAX stands for Worldwide interoperability for Microwave Access.WiMAX is a wireless digital communications system, also known as IEEE 802.16, that is intended for wireless "metropolitan area networks". WiMAX can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations. In contrast, the WiFi/802.11 wireless local area network standard is limited in most cases to only 100 - 300 feet (30 - 100m).With WiMAX, WiFi-like data rates are easily supported, but the issue of interference is lessened. WiMAX operates on both licensed and non-licensed frequencies, providing a regulated environment and viable economic model for wireless carriers.
The IEEE 802.16 standard defines the technical features of the communications protocol. The WiMAX forum offers a means of testing manufacturer's equipment for compatibility, as well as an industry group dedicated to fostering the development and commercialization of the technology.

The carriers want 'evolution rather than revolution' with each advance in system design. That has already been seen in current 3G systems but still not to the extent that carriers would like.That is why 802.16 has core requirements that are adaptable to many types of applications and ability to extend the platform in several ways, such as higher order MIMO-AAS, without breaking core compatibility. Like LTE, WiMAX strives to be a 'long term evolution' framework platform. So both because these systems use a set of core and optional technologies and because they are fully expected to evolve over time, it is misleading to call WiMAX or LTE 'a technology'

LTE:

Long Term Evolution, the 4th generation mobile broadband standard, successor to UMTS (which is a 3G cellular technology) Increased spectrum efficiency for larger carriers and therefore increase capacity.It consists of lower cost per bit and lower prices for end-users.It has Simplified protocol stack & all-IP network architecture.
It provides reduced latency,easier network management.Has high Flexibilities and scalability in deployment depending on spectrum availability.Operating in various frequency bands from 1.4 to 20MHz and therefore can be deployed in lower frequencies.
Operators can start with smaller deployment and increase bandwidth as users increase and
supports resource aggregation for radio band resources
UMB:
UMB (Ultra Mobile Broadband) was the brand name for a project within 3GPP2 to improve the CDMA2000 mobile phone standard for next generation applications and requirements. In November 2008, Qualcomm, UMB's lead sponsor, announced it was ending development of the technology, favoring LTE instead.
Like LTE, the UMB system was to be based upon Internet (TCP/IP) networking technologies running over a next generation radio system, with peak rates of up to 280 Mbit/s. Its designers intended for the system to be more efficient and capable of providing more services than the technologies it was intended to replace. To provide compatibility with the systems it was intended to replace, UMB was to support handoffs with other technologies including existing CDMA2000 1X and 1xEV-DO systems. However 3GPP added this functionality to LTE, allowing LTE to become the single upgrade path for all wireless networks. No carrier had announced plans to adopt UMB, and most CDMA carriers in Australia, USA, Canada, China, Japan and Korea have already announced plans to adopt either WiMAX or LTE as their 4G technology.
UMB was intended to be a so-called fourth-generation technology. These technologies use a high bandwidth, low latency, underlying TCP/IP network with high level services such as voice built on top. Widespread deployment of 4G networks promises to make applications that were previously not feasible not only possible but ubiquitous. Examples of such applications include mobile high definition video streaming and mobile online gaming.UMB's use of OFDMA would have eliminated many of the disadvantages of the CDMA technology used by its predecessor, including the "breathing" phenomenon, the difficulty of adding capacity via microcells, and the fixed bandwidth sizes that limit the total bandwidth available to handsets.Data speeds over 275 Mbit/s downstream and over 75 Mbit/s upstream Scalable bandwidth between 1.25-20 MHz (OFDMA systems are especially well suited for wider bandwidths larger than 5 MHz)
Current research:
Pervasive networks are an amorphous and at present entirely hypothetical concept where the user can be simultaneously connected to several wireless access technologies and can seamlessly move between them (See vertical handoff, IEEE 802.21). These access technologies can be Wi-Fi, UMTS, EDGE, or any other future access technology. Included in this concept is also smart-radio (also known as cognitive radio technology) to efficiently manage spectrum use and transmission power as well as the use of mesh routing protocols to create a pervasive network.
Future development plans:
Digiweb, an Irish fixed and wireless broadband company, announced that they have received a mobile communications license from the Irish Telecoms regulator, ComReg. This service will be issued the mobile code 088 in Ireland and will be used for the provision of 4G Mobile communications.Aruond 2011 Digiweb will launch a mobile broadband network using FLASH-OFDM technology at 872 Mhz.
On September 20, 2007, Verizon Wireless announced that it plans a joint effort with the Vodafone Group to transition its networks to the 4G standard LTE. On December 9, 2008, Verizon Wireless announced that they intend to build and begin to roll out an LTE network by the end of 2013.
Telus and Bell Canada, the major Canadian cdmaOne and EV-DO carriers, have announced that they will be cooperating towards building a fourth generation (4G) LTE wireless broadband network in Canada. As a transitional measure, they are implementing 3G UMTS to go live by early 2010.Sprint offers a 3G/4G connection plan, currently available in select cities in the United States. It delivers rates up to 36 Mbit/s.
O2 is to use Slough as a guinea pig in testing the 4G network and has called upon Huawei to install LTE technology in six masts across the town to allow people to talk to each other via HD video conferencing and play PlayStation games while on the move.
Conclusion:
4G will change the way we work, live and play. Cheap end user costs, fast, always on, reliable connectivity, where ever you are, what ever your doing. Some people view 3G as a stop gap until the real 4G network arrives, something which is due around 2010, and will impact every one, every where.
This technology will overcome the disadvantages of the past technologies.World with this will become very fast & furious .Thus we conclude that the upcoming world will be fulfilled by 4g technology……,