Orthogonal Frequency Division Multiplexing (COFDM) technology is a modulation system that separates a single carrier signal into thousands of signal carriers at the same time. The signals are distributed perpendicularly to each other so they do not disrupt each other. As the name suggests, COFDM Technology divides a broad band channel into a number of unique narrow subcarriers/sub-channels.

COFDM technology is used mostly in European countries and is in line with the digital Video broadcasting (DVB) standards. There are certain limitations that are caused by the frequency fading, leading to varying signal strengths in addition to the inter symbol interference (ISI) that can take place if a symbol assumes a lengthy reflected path and gets delayed enough that it interferes with the successive symbol that has been transmitted over a shorter distance.

The major reason for the use of COFDM Technology in Europe is its capability to fully prevent multi-path effects. A travelling signal is usually met with obstacles such as buildings, canyons, and other things, which disperse the signal making it take several paths to reach its destination, the TV. The delayed arrival of the dispersed parts of the signal results in ghost images. Multi-path effects can also be caused by someone entering the room. That’s why some users in urban areas or places with tough terrain choose satellite or cable television rather than adjusting their antennas for enhanced reception.

COFDM technology is resistant to these multi-path effects since it utilizes multiple broadband carriers to send the same signal. Instead of an obstacle causing a signal to disperse, it moves around the obstruction, making it ideal for mobile TV viewing and DTV programming. Issues with multipath effects were sometimes reported in earlier assessments of 8-VSB, but features like internal antennas will eventually help prevent them.

Stations send the same signal all the time across various countries even by using single frequency networks. A single frequency network is made up of multiple stations that transmit the same signal at the same time using several transmitters. This enables consumers to watch the same TV broadcast wherever they are in Europe without any problems. COFDM is perfect for single frequency networks.

COFDM Technology also offers a realistic solution to the issue of inter symbol interference. Between two different symbols, a silent signal interval is observed to ensure that there is enough time for a replica of the symbol to be received without interfering with the following symbol.

When it comes to a single carrier network, the problem is that the length of the symbol can be too short for the required data transmission rate. In real situations, the guard interval required to make up for the path length disparities can be as long as or even longer than the actual symbol. This greatly reduces the data amount that can be transmitted because the interval period becomes dominant. The symbols of a COFDM wireless system ends up being longer than the number of sub-networks used. Consequently, a guard interval of a certain length ends up having a less impact on the transmitted data since the data transmitting symbol takes preference over the guard interval.