Power and spectrally efficient SFH-FQPSK for PCS applications

A power and spectrally efficient slow frequency hopping FQPSK (SFH-FQPSK) is proposed for future personal communications systems (PCS). The authors apply the constant envelope FQPSK modem/radio architecture (filtered QPSK (Feher, 1982)) to a slow frequency hopping system to achieve higher spectrum efficiency as well as higher power efficiency. Being a constant envelope system, SFH-FQPSK can operate with class C power amplifier without output backoff (OBO). Therefore, it is 4-7 dB more power efficient than T/4-QPSK which is currently adopted as the US digital cellular and Japanese handyphone PCS standards. As compared to the European DECT and GSM standard GMSK, the proposed SFH-FQPSK is about 50% more spectrally efficient. The BER performance of this system, employing convolutional coding and Viterbi decoding for FEC, is evaluated in a Rayleigh fading/AWGN environment. Results show that the BER performance of the authors hard-limited SFH/FQPSK is as good as that of linear SFH coherent QPSK (SFH-CQPSK), and is 3 and 5 dB better than ideal coherent QPSK and differentially encoded coherent QPSK (DEQPSK) systems, respectively. With the higher spectral and power efficiency and superior BER performance, the authors conclude that the proposed SFH-FQPSK is an excellent candidate for the future high-capacity PCS networks