University of Debrecen
In an OFDM system, IDFT and CP insertion at the transmitter together with CP removal and DFT at the receiver help to convert an inter-symbol interference channel into several ISI free sub-channels. The CP length is designed no less than the length of the Channel Impulse Response (CIR) in order to eliminate the effects of the Inter-Block Interference (IBI) and Inter-Carrier Interference (ICI). Unfortunately, scenarios with insufficient CP may occur. For example, in a relay network, where the multipaths may be from relay nodes and thus, the CIR order may be hard to predict because the time delays of the multipaths from the relay nodes may be hard to predict due to their motions and different locations.