Pilot symbol aided QPRS for digital land mobile applications

The performance of a narrowband partial response signaling system in a frequency selective fading channel is studied for different receiver structures. Bit errors caused by Rayleigh fading are mitigated by periodically inserting pilot symbols that are used to provide amplitude and phase references at the receiver. It is shown that the delay spread tolerance of a quadrature partial response signaling, (QPRS) system is comparable to that of π/4-quadrature phase shift keying (QPSK) systems. Analytical and computer simulation results indicate that the performance of bit-by-bit detection is the same as that of maximum-likelihood receivers in a fading channel, whereas the lattice has nearly 2.5-dB gain in the additive white Gaussian noise (AWGN) channel. The performance gain of two-branch maximum-ratio (MR) combining and selection diversity receivers which can be implemented in the baseband is also studied