Reduced Guard Interval Orthogonal Frequency Division Multiplexing: A Soft Trade-Off Solution Toward Spectral Efficiency

The guard interval, termed as cyclic prefix (CP) or zero-padding (ZP), is utilized to mitigate multipath interference in orthogonal frequency division multiplexing (OFDM) systems but at the expense of spectral efficiency. Symbol cyclic shift equalization (SCSE) is our previous proposal to address multipath propagation in CP-free OFDM systems. However, SCSE-OFDM exhibits poor bit error rate (BER) performance when the power of the shortest resolvable path is relatively low. In light of this, we carry out a reduced guard interval (RGI) OFDM scheme that achieves a soft trade-off between SCSE-OFDM and ZP-OFDM, where RGI length can be optimized using genetic algorithm. Simulation results demonstrate superior BER performance of RGI-OFDM over SCSE-OFDM and higher spectral efficiency compared to both SCSE-OFDM and ZP-OFDM. RGI-OFDM also exhibits evident advantages in harsh environments with large delay spread.