The effect of channel´s delay spread on the efficiency of OFDM system

Multipath spread is one of the most important factors which limit data transfer with high bit rate. Data transfer with high bit rate is possible in the range of gigahertz. The main problem in this frequency range is multipath spread. Orthogonal frequency division multiplexing (OFDM) technique divides the transferring symbols between several subcarriers and transfers them simultaneously. Accordingly this technique is very resistant against the adverse effects of multipath spread. As a result of the increasingly grow of systems with high capacity, the uses of this technique increases cumulatively. OFDM system along with MIMO has been offered for the next generations of cell phones. Channel coding plays an important role in improving the efficiency of OFDM. Due to the special structure of OFDM, using channel coding in it, compared with uni-subcarrier systems, has special features which enhance the efficiency of the system. For this reason, this system is also called coded OFDM or COFDM. In this article in addition to studying the OFDM technique, we will consider the role of the delay spread of the channel in increasing the coding interest of the channel and the efficiency of OFDM system.