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In this Letter, a new criterion based on frozen BER (FBER) is proposed to early stop belief propagation (BP) decoding of polar codes. The authors first verify that the behaviour of FBER along with the iteration is almost the same as the information BER. Based on this phenomenon, the authors propose a new criterion by detecting the status of FBER to determine whether the BP decoding is successful or not. To reduce the complexity, only a part of frozen bits transmitted in most reliable frozen sub‐channels are considered. Simulation results show that the proposed criterion is more hardware friendly than the existing criteria. [ABSTRACT FROM AUTHOR]

Frame error rate bound is a useful tool to predict the performance behaviour of coded faster than Nyquist system (FTN). In this Letter, the Euclidean distance distribution (EDD) of FTN signalling is assumed continuous and obeys the Gaussian distribution for its long memory length. By using the autocorrelation properties of the error sequences, the EDD of FTN is estimated and the simplified bound is further derived which indicates that the performance of coded FTN system is bounded by the performance of employed coding scheme. Simulation results show that the bound is well matched with the simulated performance in high SNR regime. [ABSTRACT FROM AUTHOR]

Faster‐than‐Nyquist (FTN) signalling, as a bandwidth‐efficient modulation format, attracts many researchers' attention. However, the symbol rates of FTN signal are increasing when the packing ratios decreases. Moreover, the FTN signal with small packing ratios requires a high‐rate analogue‐to‐digital converter. Since the bandwidth of FTN signal remains the same, the samples taken at Nyquist sampling rate do not suffer information loss. However, the variable packing ratios induce extra memory‐consumption when the FTN signal is sampled at Nyquist sampling rate. To reduce the sampling rate and the memory‐consumption, a new receiver of FTN signal with oversampling is proposed. Simulation results show that the receiver can perform close to the convolution code line. At the same time, the sampling rate and the memory‐consumption can be reduced by adjusting the oversampling factors according to the packing ratios. [ABSTRACT FROM AUTHOR]

In the digital communications, due to the timing‐offset existing between the transmitter and receiver, timing synchronisation is a critical problem which may have dramatic effect on the transmission performance in the faster‐than‐Nyquist (FTN) signalling system. For solving this problem, considering the intentionally intersymbol interference introduced by FTN, a new non‐data aided timing‐delay estimation scheme is proposed. Moreover, the proposed method can be also applied into the M‐ary quadrature amplitude modulation. In the end, the performance of the proposed scheme for FTN system is tested and verified. [ABSTRACT FROM AUTHOR]

Theoretically, the accurate signal‐to‐noise ratio (SNR) is necessary when using a successive cancelation (SC) or belief propagation (BP) decoder for polar codes. However, the effect of an SNR mismatch on the bit error rate performance of polar codes has not been addressed yet. The sensitivity of polar decoding with SC and BP decoders to the mismatch of SNR is studied. Theoretical and simulation results show that an estimation of SNR is not necessary for polar codes from a practical point of view. [ABSTRACT FROM AUTHOR]

A parallel concatenated coding structure, which can improve the performance of polar codes in finite‐length regime, is proposed. In the proposed structure, the encoder is built using two systematic polar codes (SPCs), and the decoder adopts iterative belief propagation decoding algorithm. Numerical results in the binary‐input additive white Gaussian noise channel indicate that the proposed coding scheme can improve BER performance of polar codes significantly. Specially, BER of the proposed coding scheme with length 192 is almost equal to that of original SPCs with length 256, when the code rate is 1/3. [ABSTRACT FROM AUTHOR]

A new non‐data aided frequency‐offset estimation scheme for faster‐than‐Nyquist (FTN) signalling system is proposed. Considering the intentionally introduced intersymbol interference, the envelope of carrier signals is time varying, which makes it difficult to estimate the carrier frequency‐offset at the receiver. In order to improve the estimation performance, a new estimation scheme is proposed which is based on Newton's method for minimising the non‐linear least‐squares error. Moreover, the proposed estimation scheme can be also applied into M‐ary pulse‐amplitude modulation. Further, the performance of proposed frequency‐offset estimation scheme for FTN is verified and tested. [ABSTRACT FROM AUTHOR]

Considering the intentionally introduced inter‐symbol interference and coloured noise, proposed is a new signal‐to‐noise ratio (SNR) estimator based on the expectation–maximisation algorithm for the faster‐than‐Nyquist signalling system. The proposed SNR estimator can maximise the likelihood function by iteratively using the soft information from the channel decoder. Moreover, the new SNR estimator can be applied into high‐order modulation. The performance of the proposed SNR estimator is verified and tested. [ABSTRACT FROM AUTHOR]

The detection performance of high-frequency surface wave radar (HFSWR) is significantly impacted by ionospheric clutter and sea clutter. In order to suppress the ionospheric clutter, a new method based on the largest Lyapunov exponent prediction algorithm is proposed in this Letter. Firstly, it is demonstrated, for the first time, that the ionospheric clutter from HFSWR is a chaotic dynamical process, and then the largest Lyapunov exponent is estimated using the Wolf algorithm. After verifying the actual data, this suppression algorithm can decrease the amplitude of the ionospheric clutter by at least 30 dB. [ABSTRACT FROM AUTHOR]