NO.OF GBPS DATA TRANSMITED THROUGH THIS METHOD!!

OFDM(orthogonal frequncy division multiplexing)

OFDM is a high speed data trancfer method.using this method we can transmit data at a rate of 100gbps.

To overcome the effect of multi path fading problem available in UMTS, LTE uses Orthogonal Frequency Division Multiplexing (OFDM) for the downlink - that is, from the base station to the terminal to transmit the data over many narrow band careers of 180 KHz each instead of spreading one signal over the complete 5MHz career bandwidth ie. OFDM uses a large number of narrow sub-carriers for multi-carrier transmission to carry data.

Orthogonal frequency-division multiplexing (OFDM), is a frequency-division multiplexing (FDM) scheme used as a digital multi-carrier modulation method.

OFDM meets the LTE requirement for spectrum flexibility and enables cost-efficient solutions for very wide carriers with high peak rates. The basic LTE downlink physical resource can be seen as a time-frequency grid, as illustrated in Figure below:

The OFDM symbols are grouped into resource blocks. The resource blocks have a total size of 180kHz in the frequency domain and 0.5ms in the time domain. Each 1ms Transmission Time Interval (TTI) consists of two slots (Tslot)

Each user is allocated a number of so-called resource blocks in the time.frequency grid. The more resource blocks a user gets, and the higher the modulation used in the resource elements, the higher the bit-rate. Which resource blocks and how many the user gets at a given point in time depend on advanced scheduling mechanisms in the frequency and time dimensions.

The scheduling mechanisms in LTE are similar to those used in HSPA, and enable optimal performance for different services in different radio environments

Advantages of OFDM

The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe channel conditions (for example, attenuation of high frequencies in a long copper wire, narrowband interference and frequency-selective fading due to multipath) without complex equalization filters.

Channel equalization is simplified because OFDM may be viewed as using many slowly-modulated narrowband signals rather than one rapidly-modulated wideband signal.

The low symbol rate makes the use of a guard interval between symbols affordable, making it possible to eliminate inter symbol interference (ISI).

This mechanism also facilitates the design of single frequency networks (SFNs), where several adjacent transmitters send the same signal simultaneously at the same frequency, as the signals from multiple distant transmitters may be combined constructively, rather than interfering as would typically occur in a traditional single-carrier system.

!!ERA OF ULTRA HIGH SPEED OPTICAL FIBER !!

optical fiber research for the ultrahigh-speed, high-capacity era

Internet traffic is increasing exponentially with the accelerating spread of services such as social networking and video content services. The bandwidth of optical fiber communications systems that form the backbone for this communication is also being increased yearly. However, there are limits to the increase in bandwidth and speed that can be achieved with the single-mode optical fiber currently in use, and it is estimated that these limits will be reached in ten years. Therefore, a new transmission medium that overcomes these limitations will need to be created. We are focusing on ways to spatially extend the transmission area of optical fiber, which is one way to overcome these limitations. Current optical fibers transmit optical signals using a single mode, through a single core (transmission path) within a strand of quartz glass. However, optical fiber design and production technology is advancing because of the employment of complex cross sections such as hole structures, and digital transmission processing technology.

 Fiber with multiple cores in a single strand of quartz glass, and multi-mode fiber capable of transmitting stable signals with multiple modes in a single core are presenting new possibilities for novel fiber structures with higher spatial multiplexing. We have continued to demonstrate the possibilities of multicore fiber with, for example, a successful 1-Pbit/s transmission over a single 12-core optical fiber of 52 km, which is a world record (ECOC (European Conference on Optical Communication) International Exhibition, Sept. 2012.

!!WOW !! FIBER CREATED!! OPERATS AT 99.7% SPEED OF LIGHT!!

!!record !! fiber Created, that operates at 99.7% speed of light!!!

Researchers at the University of Southampton in England have produced optical fibers that can transfer data at 99.7% of the universe’s speed limit: The speed of light. The researchers have used these new optical fibers to transfer data at 73.7 terabits per second — roughly 10 terabytes per second, and some 1,000 times faster than today’s state-of-the-art 40-gigabit fiber optic links, and at much lower latency.

The speed of light in a vacuum is 299,792,458 meters per second, or 186,282 miles per second. In any other medium, though, it’s generally a lot slower. In normal optical fibers (silica glass), light travels a full 31% slower. Light actually travels faster through air than glass — which leads us neatly onto the creation of Francesco Poletti and the other members of his University of Southampton team: A hollow optical fiber that is mostly made of air. 


It might seem counterintuitive, transmitting light down fibers made primarily of air, but look around you: If light didn’t travel well through air, then you’d a hard time seeing. It isn’t like researchers haven’t tried making hollow optical fibers before, of course, but you run into trouble when trying to bend around corners. In normal optical fiber, the glass or plastic material has a refractive index, which causes light to bounce around inside the fiber, allowing it to travel long distances, or Remove the glass/plastic and the light just hits the outer casing, causing the signal to fizzle almost immediately. The glass-air interface inside each fiber also causes issues, causing interference and limiting the total optical bandwidth of the link.