SISO FB-MAP Detection for Turbo-Coded Differential PSK Systems

A new decoding scheme for product accumulate (PA) code over a space optical Poisson/pulse-position modulation (PPM) channel is investigated. In this scheme, the PPM and the accumulator of the PA code are taken as a single inner code, decoded with an iterative demodulating-decoding technique based on Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm, rather than belief propagation (BP) algorithm in the original scheme. Simulation results show that this scheme provides much better bit error rate (BER) performance. At a BER of 10−5, the new scheme has a gain of 1.8 dB more than the original one. In addition, extrinsic information transfer (EXIT) charts are employed to analyze and compare the performance. The results indicate that the new scheme has not only better BER performance, but also lower error floor.

Vehicle-to-Vehicle (V2V) communication is crucial for intelligent transportation system (ITS). Accurate channel estimation is important for realizing reliable V2V communication. However, these existing channel estimation methods cannot provide an accurate estimation performance in low and high signal-to-noise ratio (SNR) simultaneously. To address this problem, an improved channel estimation method was proposed in this paper. The method we proposed is based on constructed data-pilots (CDP) channel estimation method, Spectral Temporal Averaging (STA), and SNR threshold determined by minimum square error (MSE) performance. Simulation results show our proposed method can get better Bit Error Rate (BER) performance than STA channel estimation method and CDP channel estimation method in a low SNR range, and get an almost same BER performance as the CDP channel estimation method in a high SNR range.

With the development of 5G technology, it is nec-essary to transmit backhaul-data with higher spectral efficiency and better Bit Error Rate (BER) performance. In this paper, the scheme of Impulse Index Modulation with the Polarized Antenna Bank (IIM-PAB) is proposed based on the the horizontally polarized antennas and the vertically polarized antennas, the polarized antenna bank and index modulation are used to improve spectrum efficiency and BER performance. The improvements offered by the proposed IIM-PAB scheme at higher spectral efficiency values look promising to unlock the potential of IM-based with 2ASK (Binary Amplitude Shift Keying) solutions. The proposed scheme can be widely applied in the field of the large-capacity wireless transmission.

In this paper, we analyze the sequential message- passing decoding algorithm of low-density parity-check (LDPC) codes by partitioning check nodes. This decoding algorithm shows better bit error rate (BER) performance than the conventional message-passing decoding algorithm, especially for the small number of iterations. Analytical results indicate that as the number of partitioned subsets of check nodes increases, the BER performance is improved. We also derive the recursive equations for mean values of messages at check and variable nodes by using density evolution with a Gaussian approximation. From these equations, the mean values are obtained at each iteration of the sequential decoding algorithm and the corresponding BER values are calculated. They show that the sequential decoding algorithm converges faster than the conventional one. Finally, the analytical results are confirmed by the simulation results.

The joint transmission scheme of polar codes and sparse code multiple access (SCMA) has been regarded as a promising technology for future wireless communication systems. However, most of the existing polar-coded SCMA (PC-SCMA) systems suffer from high latency caused by the feedback iteration and list decoding. In addition, the error performance of PC-SCMA systems is unsatisfactory for ultra-reliable transmission. Inspired by the compelling benefits of non-binary polar codes, in this paper, we design a non-binary polar-coded SCMA (NB-PC-SCMA) system with a free order matching strategy to address the issues of delay and reliability. Specifically, we first formulate a joint factor graph for NB-PC-SCMA and propose a non-binary successive cancellation list (NB-SCL) and damping based joint iterative detection and decoding (NSD-JIDD) multiuser receiver to improve the BER and latency performance. Then, a lazy-search based NB-SCL (L-NB-SCL) decoding is proposed to reduce the computational complexity by simplifying the path search pattern of the list decoder. After that, we modify the update of user nodes for SCMA detection to improve the convergence error and finally propose the improved NSD-JIDD (ISD-JIDD) algorithm, which can avoid redundant operations by exploiting L-NB-SCL decoding. Simulation results show that the proposed NB-PC-SCMA system achieves better bit error rate (BER) performance and considerable latency gain when compared to its counterparts. In particular, the proposed ISD-JIDD can achieve similar BER performance of NSD-JIDD with less complexity.

In this paper, we propose a binary frequency shift keying (2FSK) demodulation method via adaptive frequency scaling stochastic resonance (AFS-SR), aiming to improve reliability of deepwater extremely vertical acoustic communication. Through the sea trial experiment, we prove the greatest problem of vertical acoustic channel is the significantly amplitude fading of the signal. And the amplitude fading of the signal is more severe, when the underwater acoustic is transmitted from negative gradient to positive gradient. For verifying the reliability performance of the proposed approach, a simulated comparison with traditional 2FSK coherent and non-coherent demodulation is conducted. And computer simulation results indicate that, the method proposed exhibits better bit error rate (BER) performance than traditional methods in low signal-to-noise ratio (SNR). Moreover, for the BER value of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> , the method we proposed provides approximately 11dB better BER performance than traditional demodulation. The result demonstrates that the proposed method has a good application prospect in vertical acoustic channel. Therefore, it is extremely helpful to develop the level of riser safety monitoring for deepwater drilling riser.

In MC-CDMA, the data rate can be increased by reducing the spreading factor SF or by allowing multicode transmission. In this paper, we evaluate by computer simulations which gives a better bit error rate (BER) performance lower SF or multicode operation - when high level modulation is used in addition to error control coding. For a coded system in a frequency selective channel, there is a tradeoff between frequency diversity gain due to the spreading of symbols, coding gain due to better frequency interleaving effect and orthogonality destruction. It is shown that for QPSK, the performance of OFDM (MC-CDMA with SF=1) is almost the same as that of a fully spread MC-CDMA system. However, for 16QAM and 64QAM, the BER performance is better for lower SF unlike the uncoded system, wherein higher SF gives a better BER

In the spectrally efficient frequency division multiplexing (SEFDM) non-orthogonal multicarrier signal, higher spectral efficiency can be achieved at the expense of self-created inter carrier interference (ICI). The effective interference, which is contributed by all sub-carriers, has to be minimized and this results in a receiver of significant complexity. In order to mitigate the interference and simplify the receiver design, in this work, a precoding technique, based on eigenvalue decomposition of the sub-carrier correlation matrix, is utilised. Briefly, the technique is based on modifying the data sent on individual sub-carriers according to the signal quality of each, which is based on the sub-carrier to interference ratio (ScIR) of such sub-carrier as estimated from eigenvalue decomposition. A full system model is presented in this paper and simulations show that the precoding of SEFDM results in either better bit error rate (BER) performance compared to that of an orthogonal frequency division multiplexing (OFDM) system of the same spectral efficiency or in higher effective bit rate relative to an OFDM system with the same BER performance. Modelling is done in simple Gaussian noise channels and in a static frequency selective channel and for different modulation formats. Results show that for the same bandwidth a 128QAM precoded SEFDM system outperforms a 16QAM OFDM one by offering 75% bit rate increase. Furthermore, Turbo coding assisted BER performance comparisons are investigated in this work. Using 64QAM modulated symbols, the precoded SEFDM outperforms the typical OFDM by several dBs.

One of the basic keys in the next generation wireless communications systems is to propose a convenient channel estimation technique, which in turn provides a better Bit Error Rate (BER). In Multicarrier Code Division Multiple Access (MC-CDMA) system, channel estimation is very important to overcome the effect of channel fading, which may distort the symbols of the information and resulting in a considerable degradation in the BER. On the other hand, the digital modulator and demodulator associated with MC-CDMA modulation is an acceptable numerical complexity (logarithmic) for applications with low computing resources. In this paper, a New Channel Estimation (NCE) scheme has been proposed by reserving suitable positions for the pilot carrier, mainly based on interleaved partitions, by filling these carriers with the unit signal to avoid the computational complexity involved in the channel estimation scheme. The simulation results show that the NCE method applied to MC-CDMA system achieves a better improvement regarding BER performance under Rayleigh and Rice fading channels.KeywordsBERMC-CDMANCEFading channelsRayleighRice

A new rate 1/2 turbo code with short memory 2 is developed in this paper. The proposed turbo code consists of two 4-state parallel concatenated non-punctured systematic rate-2/3 convolutional codes. Using a modified maximum a posteriori (MAP) decoding algorithm working on dual codes, its bit error rate (BER) performance is comparable to that of the classic 16-state turbo code at short block lengths, such as k=1024, while its decoding complexity is less than 1/8 that of the classic 16-state turbo codes; for information block length k=504, its BER performance is better than that of the (1008, 3, 6) LDPC codes with comparable decoding complexity. The dual code decoding algorithm is intrinsically partial parallel and a considerably higher throughput of the turbo decoder can be obtained compared with classic turbo codes consisting of punctured codes. The simulation results show that the proposed turbo code can be a competitive technique for short block length applications.

Optimized polar-coded cooperation with an approximate prior probability-based threshold decision is proposed to improve the reliability and complexity in selective decode-and-forward (SDF) cooperation of multiple satellite constellation systems. First, an SDF scheme with polar coding is adopted in cooperative communications for efficient code construction and relay forwarding. Second, in the logarithmic belief propagation (BP) polar decoding, the variable iterative threshold is derived with independent and variable signal-to-noise ratio (SNR)-based approximate prior probability. This threshold reduces complexity by eliminating active nodes with high reliability in each decoding iteration. Third, the information detection factor is introduced to evaluate the accuracy of decoded bits, thereby limiting the average decoding iterations to improve decoding efficiency. Simulation results show that the proposed polar-coded SDF cooperation obtains 1.5 dB performance gain at a bit error rate (BER) of 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> compared with that of existing LDPC-related schemes. The complexity of the optimized logarithmic BP decoding is reduced by 25%–50% compared with that of the traditional BP decoding. Therefore, the proposed scheme has good BER performance and low complexity in cooperative communications of multisatellite and wireless integrated systems.

In this paper, we propose a closed-form, near-optimal signal detection (SD) scheme for underwater acoustic wireless (UAW) communication affected by non-Gaussian impulsive noise. First, we introduce an optimal SD scheme based on a Neyman-Pearson criterion-driven likelihood-ratio test (LRT), which directly employs a noise probability density function (PDF) calculated from measured UAW noise. We demonstrate that this optimal SD scheme significantly outperforms the conventional linear correlator (LC)-based SD scheme designed for Gaussian-noise channels, in terms of detection error rate (DER) performance. To address the prolonged noise observation time required for direct PDF calculation, we then propose an SD scheme that approximates the noise PDF using the Student ’s t-distribution (StD). The StD-aided PDF approximation yields a closed-form LRT expression and enables low-complexity statistical parameter estimation, in contrast to the conventional α- stable distribution-based schemes. Simulation results based on a variety of noise datasets reveal that the proposed StD-based SD scheme achieves DER performance close to that of the optimal SD scheme, while maintaining substantially lower computational complexity and shorter noise observation times.

The conventional soft decision decoding (SDD) methods require various hard decision decoders (HDDs) based on different codes or re-manipulate the generator matrix by the complicated Gaussian elimination technique according to the bit reliability. This paper presents a general multi-class neural network (NN)-based decoder for the short linear block codes, where no HDD and Gaussian elimination are required once the NN is constructed. This network architecture performs multi-classification to select the messages with high occurrence probabilities and chooses the best codeword on a maximum likelihood basis. Simulation results show that the developed approach outperforms the existing deep neural network (DNN)-based decoders in terms of decoding time and bit error rate (BER). The error-correcting performance is also superior to the conventional Chase-II algorithm and is close to the ordered statistics decoding (OSD) in most cases. For Bose–Chaudhuri–Hocquenghem (BCH) codes, the SNR is improved by 1dB to 4dB as the BER is 10−4. For the (23, 12) quadratic residue (QR) code, the SNR is improved by 2dB when the BER is 10−3. The developed NN-based decoder is quite general and applicable to various short linear block codes with good BER performance.

It’s critical to design a robust wireless communication system that achieves an improved bit error rate (BER) in mobile channels. In this paper, a 2x2 space-time (ST) orthogonal frequency division multiplexing (OFDM) system is proposed with conjugate cancellation (CC) two-path transmission scheme. The 2x2 STCC-OFDM system features in the excellent inter-carrier interference (ICI) mitigation in the mobile channels with a better BER than that of a conventional 2x2 ST-OFDM system. Five orthogonal transforms are employed as the precoder to enhance the BER further, such as Zadoff-Chu transform (ZCT), slant transform (ST), discrete Hartley transform (DHT), Haar transform (HT), and Walsh–Hadamard transform (WHT). ZCT row wise precoder provide the lowest peak-to-average power ratio and good BER performance. Simulations demonstrate that the proposed STCC-OFDM systems are robust to various channel environments Although the STCC-OFDM systems improve BER with the cost of reducing bandwidth efficiency when compared to a ST-OFDM, they can be compensated by a higher QAM constellation size.

We present the BER performance for fractional-tap-spaced DFEs with adaptive a priori H/sub /spl infin// filtering algorithm and with H/sub 2/ (recursive least squares, RLS) filtering algorithm in various frequency selective fading channels. Computer simulation results demonstrate the better bit error rate (BER) performance of the DFE with the adaptive a priori H/sub /spl infin// filtering algorithm when the ratio of the average energy-per-bit to the white noise spectral density (E/sub b//N/sub 0/) and channel-fading rate (f/sub d/T/sub s/) is large. Therefore, it is concluded that the adaptive a priori H/sub /spl infin// filtering algorithm is more robust and less sensitive to modeling error and channel parameter variation but more sensitive to input white noise.