Abstract
In this paper, we consider the problem of cyclic block construction, for frequency-domain equalization (FDE) of SOQPSK, using an intrafix segment in addition to the cyclic prefix. We propose a novel procedure to compute the intrafix symbols for SOQPSK-TG waveforms used in aeronautical telemetry. The proposed method is employed to generate an exact cyclic signal, which is a requirement for implementation of FDE at the receiver. We identify that the required number of symbols to generate an exact cyclic signal are unreasonably large for SOQPSK-TG (9 symbols per block). Thus, we also propose an approximate technique that utilizes only dominant Laurent pulses to help reduce the length of intrafix upto 2 symbols. A detailed numerical evaluation of this approximate technique is performed to study the trade-off between the reduction in the intrafix length and the ideal properties of the exact signal. Bit-error rate (BER) results are presented for minimum-mean squared error (MMSE) equalizer when the cyclic part of the received signal is made by approximation. Simulation results show that MMSE equalizer shows similar level of performance with original and approximate signal.