Nonredundant error correction for π/4-QPSK in mobile satellite channels

An improved π/4-QPSK (quadrature phase shift keying) receiver which incorporates a simple nonredundant error correction (NEC) structure is proposed for satellite and land-mobile digital broadcasting. The bit error rate (BER) performance of the π/4-QPSK with NEC is analyzed and evaluated in fast Rician fading and an additive white Gaussian noise (AWGN) environment using computer simulation. It is demonstrated that with simple electronics one can improve the performance of a noncoherently detected π/4-QPSK signal in both AWGN and fast Rician fading. When the K-factor (defined as the ratio of the average power of the multipath signal to direct path power) of the Rician channel decreases, the improvement increases. An improvement of 1.2 dB could be obtained at a BER of 10^-4 in an AWGN channel. Three types of noncoherent detection schemes for π/4-QPSK with a NEC structure are discussed: IF (intermediate frequency) band differential detection; baseband differential detection; and FM discriminator