Abstract
The simple and robust log-likelihood ratio (LLR) computation of coded Multiple Phase Shift Keying (MPSK) signals in Wireless Sensor Networks (WSNs) is considered under both phase noncoherent and Rayleigh fading channels for healthcare applications. We first simplify the optimal LLR for phase noncoherent channel, the estimation of the instantaneous channel state information (CSI) for both the fading amplitude and the additive white Gaussian noise (AWGN) is successfully avoided, and the complexity-intensive process for zero-order Bessel function of the first kind is also perfectly eliminated. Furthermore, we also develop the simplified LLR under Rayleigh fading channel. Correspondingly, the variance estimation for both AWGN and the statistical characteristic of the fading amplitude is no longer required, and the complicated process for implementation of the exponential function is also successfully avoided. Compared to the calculation of optimal LLR with full complexity, the proposed method is implementation-friendly, which is practically desired for energy-limited WSNs. The simulations are developed in the context of low-density parity-check (LDPC) codes, and the corresponding results show that the detection performance is extremely close to that of the full-complexity LLR metrics. That is, the performance degradation is efficiently prevented, whereas complexity reduction is also successfully achieved.
Highlights
We find that the decision statistic is exactly the same under both phase noncoherent channels and the Rayleigh fading channel when no coding is considered, and no contribution from the fade amplitude and the variance of the additive white Gaussian noise (AWGN) noise is observed in this decision statistic
We analyze the performance of the proposed scheme from multiple dimensions by simulating the bit error rate (BER), symbol error rate (SER) and packet error rate (PER) performance, variance, and phase robustness of different schemes, as well as the complexity of the numerical calculation process
This paper proposes two simple schemes to quickly generate bit likelihood ratio (LLR) for coded
Summary
Under a phase noncoherent channel, the pilot-aided LLR for LDPC coded MPSK orthogonal frequency division multiplexing transmission is developed in [18] It cannot be directly tailored for WSNs, wherein much attention is paid to low complexity, low cost, low power consumption. Multiple-symbol detection (MSD) scheme for offset quadrature phase shift keying (O-QPSK) receivers is considered in [24,25,26,27] All of these are developed without channel coding. We propose simple bit LLR calculation schemes for coded MPSK signals. In this case, the instantaneous fading amplitude is assumed to be available and known exactly at the receiver.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call