Time-varying modulation systems

In the current communication standards, like WiMAX and LTE, the modulation system has usually fixed symbol block length or fixed subcarrier number. In this study, the authors introduce a new concept, namely time-varying symbol block or time-varying subcarrier number into the modulation systems to improve the system performance. The authors call the new modulation system time-varying orthogonal frequency-division multiplexing, time-varying orthogonal frequency-division multiple access for multicarrier modulation and time-varying single-carrier frequency-division multiple access for single-carrier modulation. Here, peak-to-average power ratio (PAPR) is used as a criteria to change the symbol block length timely. The algorithm for determination of the symbol block length is presented. The simulation results show that the time-varying modulation schemes can clearly reduce the PAPR values for both multicarrier and single carrier modulation systems.