Adaptive guard interval length for OFDM-based WLAN systems in frequency selective channels

The long-term variation of the channel leads to changing the delay spread during the transmission time. This variation degrades the performance of conventional Orthogonal Frequency Division Multiplexing (OFDM) systems that use fixed length of the guard interval by introducing Inter-Symbol-Interference (ISI) in highly frequency selective scenarios (high delay spread) or causes needless loss of capacity for small delay spread values. In this paper an adaptive OFDM system with variable guard interval length is introduced, in which the channel delay spread is estimated using super resolution technique and then a signal is fed back to the transmitter in order to change the guard interval aiming at maximizing the throughput without sacrificing the performance in terms of Bit Error Rate (BER).