Cyclic Prefix and Intrafix Insertion for frequency domain equalization(FDE) of Shaped-offset QPSK

Abstract

In this research, we consider the problem of cyclic block construction for (FDE) of SOQPSK using an intra- x segment in addition to the cyclic pre- x. We propose a novel procedure to compute the intra- x symbols for both SOQPSK-MIL and 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. The trellis of SOQPSK-TG signal is very complicated (512 states) because of its partialresponse characteristic. 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 intra- x upto 2 symbols. A detailed numerical evaluation of this approximate technique is performed to study the trade-o between the reduction in the intra- x length and the deviation from constant envelope of the generated signal. The trellis of SOQPSK-TG signal is very complicated (512 states) because of its partial-response characteristic. 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 intra- x upto 2 symbols. A detailed numerical evaluation of iii iv this approximate technique is performed to study the trade-o between the reduction in the intra- x length and the deviation from constant envelope of the generated signal.