This paper presents a low complexity optimized algorithm for design of bilayer lengthened LDPC(BL-LDPC) code for decode-and-forward relay system.The design is performed over the expanded graph of the BL-LDPC code,which consists of the original bilayer graph and the extra added relaygenerated parity check bits.To build up our proposed optimized algorithm,we present a modified Gaussian approximation algorithm for the expanded structure of the BL-LDPC code.Then using the proposed optimized algorithm,we find the optimum overall expanded graph of the BL-LDPC code.Simulation results show that the BL-LDPC codes obtained by our proposed optimized algorithm have excellent bit-error-rate performances and small gaps between the convergence thresholds and the theoretical limits when transmitted over the additive white Gaussian noise channels.
This paper focuses on the design of continuous phase-modulated systems and simplified receiver for highmobility wireless communications.A class of spectrally efficient coded modulation systems is proposed and analyzed in terms of Euclidean distance and spectral efficiency.Moreover,the simplified detector based on mismatched receiver is designed to reduce the detection complexity exponentially for partial response systems.To deal with the fast time-varying channels without channel state information,a class of noncoherent detection algorithms for continuous phase modulation systems is developed to offer near-coherent performance.The proposed system is assessed over both the additive white Gaussian noise and fast-fading channels.Numerical and simulated results show that the proposed system offers not only high spectral efficiency but also near-optimum performance over fast time-varying scenarios.
