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The differential chaos shift keying with code index modulation (CIM-DCSK) using Walsh codes can increase the data rate, but error rate performance degrades over practical multipath channel with high delay spread. To tackle this drawback, this paper proposes a parallel CIM-DCSK (PT-CIM-DCSK), where the first time slot is used to transmit the chaotic reference sequence, and the second slot is used to transmit the multiple sequences carrying data bits. In particular, multiple $q$ chaotic sequences are added for data transmission in parallel, and each sequence is modulated by CIM-DCSK with $m_{c}$ bits. By exploiting the quasi-orthogonal characteristics of permuted chaotic signals, the interference between $q$ sequences can be remarkably suppressed. In this way, given the data rate, PT-CIM-DCSK can achieve a larger length of Walsh segment than the CIM-DCSK, since its parallel transmission compensates the rate. In addition, the error performance of the proposed scheme over the multipath Rayleigh fading channel is theoretically analyzed. The theoretical and consistent simulation results demonstrate that the PT-CIM-DCSK can obtain significant performance gains over the conventional CIM-DCSK, and the gain can be up to 5 dB in multipath fading channel with high delay. This is because the larger Walsh segment of PT-CIM-DCSK provides the enhanced robustness against multipath effect. The performance superiority of the proposed scheme is further verified in practical ultra-wideband (UWB) wireless industrial scenarios, which suggests promising for low-cost and low-complexity wireless communication applications. [ABSTRACT FROM AUTHOR]

The study designs a type of plasma antenna array with four quartz fluorescent lamps, which can be classified into linear polarization and circular polarization (CP). The antenna arrays are designed into a self-phase-shifting cross shape, and the kHz alternating current power supplies are adopted in the proposed antenna arrays. Experimental results show that the cross vibrator antenna can realize not only impedance and pattern reconstruction, but also the polarization transformation. Moreover, the horizontal polarization, vertical polarization, and CP can be mutually transformed into each other by changing the vibrator operation mode. It is noted that we can easily transform the left-hand circular polarization and right-hand circular polarization into each other via modifying vibrator length and plasma density. Compared with a conventional metal antenna with the same shape, polarization conversion can be realized in an easier yet faster way via the help of self-phase-shifting plasma antenna array. [ABSTRACT FROM AUTHOR]

This brief presents a nonbinary adaptive 2D scheduling-based majority logic decoding (NB-ATS-MLGD) algorithm for NAND flash memory. The proposed algorithms provide considerable tradeoff between error-correcting capability and decoding complexity, and make the NB-MLGD decoding more attractive for practical purposes in the multi-level cells (MLC) NAND flash memory. The most significant feature of the proposed NB-ATS-MLGD algorithm is the 2D layered scheduling strategy, where the decoding orders of check nodes (CNs) and variable nodes (VNs) are both adaptive. By leveraging on the MLC flash memory bit error patterns, an early-correcting (EC) criterion is incorporated into the NB-ATS-MLGD algorithm. Furthermore, the simplification and parallelization of proposed algorithms make them more practical in NAND flash memory. Simulation results show that the proposed algorithms increase the lifetime of MLC flash memory up to 3000 program-and-erase (PE) cycles and have desirable convergence speed compared with the conventional non-binary MLGD algorithm. When at low PE cycles, the NB-EC-ATS-MLGD algorithm improves frame error rate (FER) performance by more than 3 order of magnitudes compared with the conventional non-binary MLGD algorithm. [ABSTRACT FROM AUTHOR]

To increase program-and-erase (PE) cycles for the multi-level-cell NAND flash memory, a page-based dynamic partitioning scheduling (DPS) algorithm for low-density parity-check codes is proposed in this brief. The proposed scheme provides a dynamic scheduling metric to obtain variable nodes (VNs) with the highest erroneous probabilities in each iteration so as to improve the convergence speed of decoding. Then, two DPS-based belief-propagation (BP) and min-sum (MS) decoding algorithms are introduced, named DPS-based BP (DPS-BP) and DPS-based MS (DPS-MS), respectively, which utilize the interaction between the upper page and the lower page bits to detect the probable charge-shift memory cells. Simulation results show that the proposed DPS-BP and DPS-MS decoding algorithms improve the PE endurance up to about 700 and 1000 cycles against the conventional BP and MS decoding algorithms, respectively, at a bit-error-rate of ${10}^{{-5}}$. In addition, an effective approximation method is presented to reduce the hardware complexity in practical implementations, in which the size of each partitioned group is preset to raise the efficiency of the VN units. [ABSTRACT FROM AUTHOR]

In this paper, a detector-aware low-density parity-check (LDPC) code optimization algorithm is proposed for the ultra-high density magnetic recording channel, such as bit-patterned magnetic recording and two-dimensional magnetic recording, where a 2-D detector (2D-DET) is employed to combat 2-D intersymbol interference (2D-ISI) effects, by acquiring the variance of the 2D-ISI channel log-likelihood ratios corresponding to the specific 2D-DET. The new parameter builds a bridge of LDPC code optimization between the ISI-channel and the additive white Gaussian noise channel. Numerical results show that our proposed algorithms are more efficient in running time than other recently proposed optimization algorithms. Moreover, the protograph-based quasi-cyclic (QC) codes using the proposed optimization strategy, which have a low-complexity QC encoder structure with an effectual parallelizable protograph decoder composition, enjoy up to one order of magnitude performance gain in bit error rate over the other random codes that suffer from high error floors. [ABSTRACT FROM AUTHOR]

2-D inter-symbol-interference (2-D-ISI), consisting of ISI in the down track direction and inter-track interference along the cross-track direction, is a major factor that severely degrades the performance of ultra-high density magnetic recording systems. Due to its superior performance and the protograph structure which facilitates high-speed encoding and decoding, the protograph codes have shown a high potential to tackle 2-D-ISI. However, so far, no work has been reported on the design of non-binary protograph-based low-density parity-check (NP-LDPC) codes for 2-D-ISI channels. In this paper, we first propose a modified protograph extrinsic information transfer analysis. In conjunction with the asymptotic ensemble weight distribution analysis, they both serve as theoretical tools to analyze the performance of NP-LDPC codes designed for the 2-D-ISI channels. By further applying a fast search approach, we construct two types of NP-LDPC codes for 2-D-ISI channels. Both theoretical analyses and simulated results show that the proposed codes outperform the existing binary LDPC codes that optimized for 2-D-ISI channels as well as the non-binary quasi-cyclic LDPC code, at both low and high SNR regions. [ABSTRACT FROM AUTHOR]

In this paper, protograph-based quasi-cyclic (QC) low-density parity-check (LDPC) codes are proposed for the efficient structure coding of LDPC codes in 2-D intersymbol interference (ISI) ultrahigh density magnetic recording channels, such as bit-patterned magnetic recording and 2-D magnetic recording, where a reduced-complexity 2-D detector based on the iterative row–column soft detection feedback with Gaussian approximation is employed instead of the full 2-D Bahl–Cocke–Jelinek–Raviv detector. The proposed protograph-based codes, whose base matrices are constructed according to the degree sequences for 2-D-ISI channels, have a low-complexity QC encoder structure with a readily parallelizable protograph decoder structure. Simulation results show that the proposed protograph-based QC-LDPC codes outperform the random LDPC codes optimized for additive white Gaussian noise channels. Furthermore, the performance of the QC codes is similar to that exhibited by ISI-optimized random LDPC codes designed for 2-D-ISI channels, while retaining the implementational benefits. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of the protograph-based low-density parity-check (LDPC) codes for 2-D intersymbol interference (ISI) channels with magnetic recording density. The protograph LDPC codes have been shown to possess simple hardware implementation and excellent error performance over additive white Gaussian noise channels and over partial response channels. We propose a design scheme and construct two new protograph LDPC codes for 2-D ISI channel, with the help of extrinsic information transfer chart analysis and asymptotic ensemble weight distribution analysis. The theoretical analyses and simulated results show that the proposed codes outperform the previously optimized irregular LDPC code in both low- and high-SNR regions. Thus, the proposed codes are good alternatives compared with other error-correction codes for the use in magnetic recording systems. [ABSTRACT FROM AUTHOR]

In this paper, 2-D normalized min-sum (NMS) algorithm and offset min-sum (OMS) algorithm are proposed for efficient decoding of low-density parity-check (LDPC) codes in 2-D intersymbol interference (ISI) ultra-high density magnetic recording channels, such as bit-patterned magnetic recording and 2-D magnetic recording, where a reduced-complexity 2-D detector based on the iterative row-column soft detection feedback with Gaussian approximation detector is employed instead of the full 2-D Bahl–Cocke–Jelinek–Raviv (BCJR) detector. The normalization and offset factors of the 2-D NMS and 2-D-OMS, are optimized based on the extended density evolution for LDPC coded 2-D ISI channel, respectively. Simulation results show the performance loss caused by the reduced-complexity LDPC decoder can be almost fully recovered by the proposed approaches, while retaining the benefit of low complexity in decoder compared with the belief propagation (BP) decoding. Furthermore, both the NMS and OMS exhibit a lower error floor than that of BP decoding in high signal-to-noise ratio region. [ABSTRACT FROM AUTHOR]

Shingled magnetic recording (SMR) with 2-D magnetic recording has recently emerged as a promising technology to sustain the growth of magnetic storage areal density. However, with the reduction of track pitch, the intertrack interference (ITI) becomes a major impairment. Furthermore, in SMR, the ITI is non-uniform among the top and lower tracks. A 2-D read channel which makes use of an array of read heads can effectively detect and compensate the severe ITI. In this paper, based on a read-array SMR channel model with non-uniform ITI, a shuffled multi-track detection (SMTD) detector, which shuffles and propagates the most reliable extrinsic information among the upper, lower, and middle detectors, is proposed to mitigate ITI more effectively. With the optimized non-binary low-density parity-check code, the performance of the proposed SMTD over the read-array SMR channel is evaluated. [ABSTRACT FROM AUTHOR]

Quasi-cyclic low-density parity-check (QC-LDPC) codes constructed by using algebraic approaches, such as finite geometry and finite field, generally have good structural properties and very low error-floors, and facilitate hardware implementation. Irregular QC-LDPC codes constructed from such QC-LDPC codes by using the masking technique, when decoded with the sum-product algorithm (SPA), have low decoding complexity, but often show early error-floors. In this paper, the relationship of cycle, girth and approximate cycle EMD (ACE) between the masking matrix and masked matrix is investigated, and the ACE algorithm is modified and used to construct the masking matrix for irregular QC-LDPC codes. Simulations demonstrate that the codes constructed by masking with ACE optimization exhibit much improved waterfall performance and lower error floors. [ABSTRACT FROM PUBLISHER]

In this paper, optimization of low-density parity-check (LDPC) codes to approach the symmetric information rate (SIR) of two-dimensional (2-D) intersymbol interference (ISI) channels is proposed for high-density magnetic recording, such as bit-patterned magnetic recording (BPMR) and 2-D magnetic recording (TDMR). The code design makes use of the modified Extrinsic Information Transfer (EXIT) chart, where the optimal variable node degree is searched by selecting the best check node degree to fit the check node decoder (CND) EXIT curve to the EXIT curve of the variable node decoder (VND) curve combined with 2-D detector. Simulation results show that LDPC codes with code length 10^4 bits optimized for a 2-D ISI channel corresponding to 4 \Tb/in^2 recording density can achieve bit error rate 10^-5 at signal-to-noise ratio 0.33 dB away from the SIR. To our knowledge, this is the first capacity-approaching LDPC code successfully optimized for a 2-D ISI channel. [ABSTRACT FROM PUBLISHER]

In this paper, we present a new error-correction scheme, referred to as embedded marker code scheme (EMCS), for channels corrupted by insertions, deletions and additive white Gaussian noise (AWGN). The EMCS uses the pinning bits, which have the potential to lower the error floors of the outer low-density parity-check (LDPC) codes, for both resynchronization and improving error-correction performance. Furthermore, the soft-input synchronization for the inner decoder and the joint iterative decoding between the inner decoder and the outer decoder is employed to further improve the overall performance of the new scheme. Simulations show that the proposed EMCS reduces the code rate loss as compared with the conventional marker code scheme and achieves a better tradeoff between the error performance and the decoding complexity. Therefore, the new scheme can reduce code rate loss and improve storage efficiency when it is used in bit-patterned media recording (BPMR) systems. [ABSTRACT FROM PUBLISHER]