March 27, 2015
By: Lara Pan
OFDM is Orthogonal Frequency Division Multiplexing.
While COFDM stands for Coded Orthogonal Frequency Division Multiplexing. JH Stott of BBC Research and Development stated; “COFDM can cope with high levels of multipath propagation, with a wide spread of delays between the received signals. This leads to the concept of single-frequency networks in which many transmitters send the same signal on the same frequency, generating “artificial multipath”. COFDM resists well with co-channel narrowband interference, as may be caused by the carriers of existing analogue services.”
So COFDM is a great combination of encoding technology and OFDM modulation, which can be widely used and still with great potential in Terrestrial digital TV transmission systems as well as many other wireless transmission system applications for UAV, Oil Fields, Mining, Land Surveying, Police Defense or National Public Security, etc.
OFDM is widely used on LOS(Line of Sight) and fixed point to point/point to multipoint while COFDM with its high resistance of signal attenuation and FEC(Forward Error Correcting) advantages can send video signals from any moving objects like an floating fleet, a racing car, a tracking dog or a flying helicopter to commanding centers. The system is stabilized by Coded signals to be separated to divided single carriers, with OFDM it is like a broader high way can have only 30 cars racing together on this same path, but now with COFDM there are 30 divided paths for 30 cars to race at the same time but no interference. Therefore, we believe that COFDM will still be with much less latency and better image clarity.
So COFDM is with much higher efficiency in super-speed real-time mobile wireless transmission than OFDM with applications for live broadcasting video transmission, public mobile communication system application, real-time monitoring of maritime wireless transmission, coastal defense, port inspection and other industries.
As a conclusion, whenever you need an OFDM solution, you can always replace it by COFDM, but whenever you need a COFDM, you can never use OFDM. Need a convergence kind of story, then choose your own COFDM.
Appendix: Lara Pan is the Business Development Executive of Zhongchuang Tech, a telecom tycoon in Wireless Video Transmission systems. People like me wonder the differences between COFDM&OFDM Modulations, we got helped and now it's our pleasure to help you understand these differences better.