CP-QFSK modem for TDMA short range communications systems

Work presented in this paper investigates the feasibility of Continuous-Phase Quaternary Frequency Shift Keying (CP-QFSK) with limiter-discriminator detection modem as a viable dual data rate system that can be employed in TDMA short range communications systems. It offers a great deal of spectral efficiency in multi-channel systems, hardware simplicity and robustness to adjacent Channel Interference (ACI). The interrelated system design parameters are defined and optimized and the system performance in different propagation media is evaluated. Simulation results have demonstrated that adjacent channel rejection factor of 40 dB has been achieved and that the CP-QFSK system outperforms the GMSK modulation scheme as it causes far less ACI, and hence coexists well in a multi-channel system. Error correction coding has been applied to enhance the system quality.