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In time-varying channel, the Doppler effect destroys the subcarrier orthogonality of orthogonal frequency-division multiplexing (OFDM) system which leads inter-carrier interference (ICI). This paper presents a time domain ICI self-cancellation method from the view of equivalent channel time variation mitigation. By utilizing the assumption of linear time-varying channel model, a set of windowing coefficients is derived to mitigate the equivalent channel time variation of the corresponding part into flat. The ICI is therefore reduced by lessening the equivalent channel time variation. The proposed window shape is found as the Franks window. The theoretical ICI power and bit error rate (BER) performance for using the proposed window shape are investigated and validated by simulation results. Comparing to Chang's equivalent windowing method and the 4-step window shape for low-complex windowing method, the proposed method can provide better ICI cancellation performance given with the same criterion.

Based on the standard of digital audio broadcasting (DAB) Eureka 147 system to improve structures of transmitter/receiver, this paper proposes a physical layer transmission technique capable of boosting the spectrum efficiency up to two times of that of the DAB-Eureka 147 system while the backwards compatibility is guaranteed. The proposed transmission technique comprises the development of both the modulation and demodulation schemes. In the developed modulation scheme, differential 16-level amplitude/ phase shift keying (D16 APSK) is adopted to replace the differential quadrature-phase-shift-keying (DQPSK) used in the DAB Eureka 147 system. In the developed demodulation scheme, on the other hand, a detector for two-level differential amplitude-shift-keying (DASK) signal is proposed which can be implemented with rather low hardware costs. The performance is presented by the Simulink platform in multipath fading channel model.