We proposed a new RF-pilot based carrier frequency offset and phase noise estimation (RB-CFOPNE) scheme in offset-QAM-based filterbank multicarrier (FBMC-OQAM) systems. The performance of the proposed RB-CFOPNE with rectangular QAM modulations is evaluated by Monte Carlo simulation. The results of numerical analysis show that this method could tolerant huge frequency offset and phase noise with high speed communication system. The better performance makes it become possible for real application.
We apply the intra-symbol frequency domain averaging (ISFA) channel estimation algorithm to the intensity modulation and direct detection (IM/DD) 16QAM orthogonal frequency division multiplexing (OFDM) system and improve the performance of the system. In the paper, the weighting coefficients in the algorithm are changed to obtain the best system performance. In order to study the applicability of the algorithm, the number of different subcarriers is simulated and better system performance is obtained. In the case of changing the transmission distance, we compare the performance of traditional algorithms and ISFA.
KEYWORDS: Modulation, Signal detection, Signal to noise ratio, Signal processing, Optical engineering, Computer programming, Digital signal processing, Wavelength division multiplexing, Sensors, Transmitters
Three soft-input-soft-output (SISO) detection methods for dual-polarized quadrature duobinary (DP-QDB), including maximum-logarithmic-maximum-a-posteriori-probability-algorithm (Max-log-MAP)-based detection, soft-output-Viterbi-algorithm (SOVA)-based detection, and a proposed SISO detection, which can all be combined with SISO decoding, are presented. The three detection methods are investigated at 128 Gb/s in five-channel wavelength-division-multiplexing uncoded and low-density-parity-check (LDPC) coded DP-QDB systems by simulations. Max-log-MAP-based detection needs the returning-to-initial-states (RTIS) process despite having the best performance. When the LDPC code with a code rate of 0.83 is used, the detecting-and-decoding scheme with the SISO detection does not need RTIS and has better bit error rate (BER) performance than the scheme with SOVA-based detection. The former can reduce the optical signal-to-noise ratio (OSNR) requirement (at BER=10−5) by 2.56 dB relative to the latter. The application of the SISO iterative detection in LDPC-coded DP-QDB systems makes a good trade-off between requirements on transmission efficiency, OSNR requirement, and transmission distance, compared with the other two SISO methods.
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