Search

The blind quantum computation (BQC) protocol allows for privacy-preserving remote quantum computations. In this paper, we introduce a remote quantum error correction code preparation protocol for BQC using a cluster state and analyze its blindness in the measurement-based quantum computation model. Our protocol requires fewer quantum resources than previous methods, as it only needs weak coherent pulses, eliminating the need for quantum memory and limited quantum computing. The results of our theoretical analysis and simulations show that our protocol requires fewer quantum resources compared to non-coding methods with the same qubit error rate. [ABSTRACT FROM AUTHOR]

Compute-and-forward (CAF) relaying is an effective way to increase bandwidth efficiency of wireless two-way relay channels. Design of error-correcting codes and their decoding algorithms suitable for CAF relaying schemes remains an important issue to be studied. In this paper, we will analyze an asymptotic behavior of LDPC codes over two-way relay channels based on density evolution (DE). Because of the asymmetric characteristics of the channel, we use the population dynamics DE combined with DE formulas for asymmetric channels to obtain the belief propagation (BP) thresholds. Additionally, we also evaluate the asymptotic performance of spatially coupled LDPC codes for two-way relay channels. The results indicate that the spatially coupled codes yield improvements in the BP threshold compared with corresponding uncoupled codes for two-way relay channels. [ABSTRACT FROM AUTHOR]

This paper proposes a soft input decoding algorithm and a decoder architecture for generalized concatenated (GC) codes. The GC codes are constructed from inner nested binary Bose–Chaudhuri–Hocquenghem (BCH) codes and outer Reed–Solomon codes. In order to enable soft input decoding for the inner BCH block codes, a sequential stack decoding algorithm is used. Ordinary stack decoding of binary block codes requires the complete trellis of the code. In this paper, a representation of the block codes based on the trellises of supercodes is proposed in order to reduce the memory requirements for the representation of the BCH codes. This enables an efficient hardware implementation. The results for the decoding performance of the overall GC code are presented. Furthermore, a hardware architecture of the GC decoder is proposed. The proposed decoder is well suited for applications that require very low residual error rates. [ABSTRACT FROM PUBLISHER]

This paper proposes a new concatenated error correction coding scheme for 2-D magnetic recording (TDMR). The designed concatenated coding scheme consists of outer codes as binary polar codes and an inner code as non-binary low-density parity-check (LDPC) code. These error-correcting codes (ECCs) are considered to achieve large coding gains with small bandwidth expansion in the presence of intersymbol interference and inter-track interference. Polar codes have attracted much attention as one of the ECCs that provably achieve the optimal symmetric capacity of memoryless channels with an explicit construction and are decoded by the successive-cancellation decoding algorithm, whose computational complexity is comparatively low. Using systematic polar codes, we are able to design proper low-complexity ECCs with run-length-limited constraints for any TDMR schemes based on the selection criterion (which is called channel polarization) for choosing parity and information symbols by the magnitude of the approximately calculated mutual information amount regarding each recorded symbol in a codeword. Concretely, the concatenated coding schemes are designed for four-track and three-track recording, and the block error rate (BER) performances of 2-D partial response equalized signal processing schemes with proposed concatenated ECCs for bit-patterned media recording are evaluated. As a result, it shows that the BER performances of the proposed schemes are superior to that of the conventional scheme using a 1-D high rate binary LDPC code. [ABSTRACT FROM PUBLISHER]

Due to serious problems of SRAM-based caches in nano-scale technologies, researchers seek for new alternatives. Among the existing options, STT-RAM seems to be the most promising alternative. With high density and negligible leakage power, STT-RAMs open a new door to respond to future demands of multi-core systems, i.e., large on-chip caches. However, several problems in STT-RAMs should be overcome to make it applicable in on-chip caches. High probability of write error due to stochastic switching is a major problem in STT-RAMs. Conventional Error-Correcting Codes (ECCs) impose significant area and energy consumption overheads to protect STT-RAM caches. These overheads in multi-core processors with large last-level caches are not affordable. In this paper, we propose Asymmetry-Aware Protection Technique (A$^2$ PT) to efficiently protect the STT-RAM caches. A$^2$ PT benefits from error rate asymmetry of STT-RAM write operations to provide the required level of cache protection with significantly lower overheads. Compared with the conventional ECC configuration, the evaluation results show that A $^2$ PT reduces the area and energy consumption overheads by about 42 and 50 percent, respectively, while providing the same level of protection. Moreover, A$^2$ PT decreases the number of bit switching in write operations by 28 percent, which leads to about 25 percent saving in write energy consumption. [ABSTRACT FROM AUTHOR]

It is known that the error rate can be used as a measure of reliability and security over the wire-tap channel when practical, finite length codes are used for transmission, and the security gap is an error rate based metric able to jointly treat these two aspects. In this paper, we consider several low-density parity-check (LDPC) coded transmissions, which represent the state of the art for transmissions over the wire-tap channel and we assess and compare their security gap performance. We consider two kinds of wire-tap channels: the flat and the fast fading wire-tap channels with additive white Gaussian noise. As a reference, we use the progressive edge growth (PEG) algorithm for the design of unstructured LDPC codes and compare its performance with that of four approaches for designing structured LDPC codes. We analyze both systematic and non-systematic transmissions and show that some structured code design techniques are able to achieve comparable or even better performance than the PEG algorithm over the considered channels, while taking advantage of their simpler encoding and decoding procedures. [ABSTRACT FROM AUTHOR]

Consider the following unequal error protection scenario. One special message, dubbed the “red alert” message, is required to have an extremely small probability of missed detection. The remainder of the messages must keep their average probability of error and probability of false alarm below a certain threshold. The goal then is to design a codebook that maximizes the error exponent of the red alert message while ensuring that the average probability of error and probability of false alarm go to zero as the blocklength goes to infinity. This red alert exponent has previously been characterized for discrete memoryless channels. This paper completely characterizes the optimal red alert exponent for additive white Gaussian noise channels with block power constraints. [ABSTRACT FROM PUBLISHER]

This paper describes a combinatorial approach to estimate the error rate performance of low-density parity-check (LDPC) codes decoded by (quantized) soft-decision iterative decoding algorithms. The method is based on efficient enumeration of input vectors with small distances to a reference vector whose elements are selected to be the most reliable values from the input alphabet. Several techniques, including modified cycle enumeration, and the efficient derivation of problematic inputs for finer quantizers from those of coarser ones are employed to reduce the complexity of the enumeration. The error rate estimate is derived by testing the input vectors of small distances followed by estimating the contribution of larger distance vectors. We demonstrate by a number of examples that the proposed method provides accurate estimates of error rate with computational complexity much lower than that of Monte Carlo simulations, especially at the error floor region. [ABSTRACT FROM PUBLISHER]

In this paper, a symbol error rate (SER) study is presented for the dual-hop relay networks employing space–time block code (STBC) from coordinate interleaved orthogonal design (STBC-CIOD), where a relay with either a decode-and-forward (DF) or an amplify-and-forward (AF) protocol is equipped with multiple antennas. More specifically, we provide the union upper and lower bounds on the average SER by deriving an accurate closed-form formula for the corresponding symbol pairwise error rate (SPER). In addition, the asymptotic diversity order is analyzed. The theoretically derived bounds are in good agreement with the simulation results. [ABSTRACT FROM PUBLISHER]

We introduce in this paper the concept of a correctable error set and a fixed initialization decoding, by noticing that the sum-product decoder with a given iteration number only depends on the initialized probability of error, for a BSC. Although this value has been conventionally selected as the BSC crossover probability, we show that other selections can provide better performance or faster convergence. We also prove that for any fixed initialization (i.e., any given correctable error set), the word-error-rate can be represented as a polynomial of the BSC crossover probability. This suggests that the word-error-rate can be analytically derived from the knowledge of the correctable error set. [ABSTRACT FROM AUTHOR]

The use of open-loop coding can be easily extended to a closed-loop concatenated code if the transmitter has access to feedback. This can be done by introducing a feedback transmission scheme as an inner code. In this paper, this process is investigated for the case when a linear feedback scheme is implemented as an inner code and, in particular, over an additive white Gaussian noise (AWGN) channel with noisy feedback. To begin, we look to derive an optimal linear feedback scheme by optimizing over the received signal-to-noise ratio (SNR). From this optimization, a linear feedback scheme is produced that is asymptotically optimal in the sense of blocklength-normalized SNR; it is then compared to other well-known schemes. Then, the linear feedback scheme is implemented as an inner code to a concatenated code over the AWGN channel with noisy feedback. This code shows improvements not only in error exponent bounds, but also in bit error rate (BER) and frame error rate (FER). It is also shown that if the concatenated code has total blocklength L and the inner code has blocklength, N, the inner code blocklength should scale as N = O\left(C\over R\right), where C is the capacity of the channel and R is the rate of the concatenated code. Simulations with low-density parity-check (LDPC) and turbo codes are provided to display practical applications and their error rate benefits. [ABSTRACT FROM AUTHOR]

The error-pattern correcting code (EPCC) is a code designed to correct frequently observed error cluster patterns of the intersymbol interference (ISI) channel. This paper focuses on developing theoretical understanding of the performance of serial concatenation of the EPCC with an outer recursive systematic convolutional code (RSCC) in ISI channel environments. To analyze the performance of this EPCC-RSCC concatenation, an upper union bound on the maximum-likelihood (ML) bit-error rate (BER), averaged over all possible interleavers, is derived which offers crucial insights into the error floor behavior of the matching turbo decoder. The ML bound is also used to compare the performance of EPCC-RSCC to that of a stand-alone RSCC in serial concatenation to precoded and nonprecoded ISI channels. This comparison shows that by targeting the low Hamming-weight interleaved errors of the RSCC, which result in low Euclidean distance error events in the channel detector, EPCC-RSCC exhibits a much lower BER floor compared to conventional schemes, especially for high rate applications and short interleaver lengths. The error rate performance of an iterative suboptimal turbo equalizer (TE), called TE-EPCC, is also demonstrated to converge close to the ML bound at high SNR. [ABSTRACT FROM AUTHOR]

In this paper, we consider the problem of coding for the half-duplex nonorthogonal amplify-and-forward (NAF) cooperative channel where the transmitter to relay and the interrelay links are highly reliable. We derive bounds on the diversity order of the NAF protocol that are achieved by a distributed space-time bit-interleaved coded modulation (D-ST-BICM) scheme under iterative APP detection and decoding. These bounds lead to the design of space-time precoders that ensure maximum diversity order and high coding gains. The word error rate performance of D-STBICM are also compared to outage probability limits. [ABSTRACT FROM AUTHOR]

This paper considers the performance limits for joint detection and estimation from a finite set-valued observation that is stochastically related to the state or parameter of interest. Detection refers to inference about the existence of the state, whereas estimation refers to inference about its value, when detected. Since we need to determine the existence/non-existence of the state as well as its value, the usual notion of Euclidean distance error does not jointly capture detection and estimation error in a meaningful manner. Treating the state as set, which can be either empty or singleton, admits a meaningful distance error for joint detection and estimation. We derive bounds on this distance error for a widely used class of observation models. When existence of the state is a certainty, our bounds coincide with recent results on Cramér-Rao bounds for estimation only problems. [ABSTRACT FROM AUTHOR]

In this paper, a new approach is presented to derive the exact bit-error-rate (BER) performance of frequency-hopping spread-spectrum (FHSS) wireless networks with noncoherent M-ary frequency-shift keying (MFSK) in additive white Gaussian noise (AWGN) and Rayleigh fading channels. The new approach has enabled an exact evaluation of the BER, regardless of the modulation order M or the number of interferers. Theoretical results validated by simulations have shown that system performance is dominated by the first two hits, which lead to an accurate and computationally efficient approximation for the AWGN channel case. The exact and approximated results are compared with the simulation and semianalytic results presented in the literature. [ABSTRACT FROM AUTHOR]

This paper presents linear and nonlinear precoding design for error-rate improvement in orthogonal space-time block-coded (OSTBC) multiple-input-multiple-output (MIMO) orthogonal frequency-division-multiplexed (OFDM) downlink, where both the conditional mean of the channel gain matrix and the channel gain covariance matrix may be available at the transmitter. The conditional means of the channel matrix are derived for a general transmit-antenna-correlated frequency-selective fading MIMO channel with estimation errors and feedback delay. Mean-feedback linear precoding and nonlinear Tomlinson-Harashima precoding (THP) are developed to maximize the signal-to-noise power ratio (SNR). The intuition that when the mean feedback becomes accurate the mean-feedback precoding outperforms covariance precoding is confirmed. Dual-mode precoding is also proposed, in which the novel mean-feedback precoding or covariance precoding is adaptively chosen at the receiver. The precoding-mode switching metric is the maximized SNR, which is an indicator of the error rate. The receiver calculates its metric, selects the mode that achieves a higher SNR, and decides whether mean feedback is necessary. Our proposed precoders (both mean feedback and adaptive) significantly reduce the system error rate. Nonlinear precoding is shown to outperform linear precoding. Adaptive precoding outperforms both mean-feedback precoding and covariance precoding if individually applied in OSTBC OFDM. [ABSTRACT FROM AUTHOR]

In this paper, a novel class of serially concatenated convolutional codes (SCCCs) is addressed. In contrast to standard SCCCs, where high rates are obtained by puncturing the outer code, the heavy puncturing is moved to the inner code, which can be punctured beyond the unitary rate. We derive analytical upper bounds on the error probability of this code structure by considering an equivalent code construction consisting of the parallel concatenation of two codes, and address suitable design guidelines for code optimization. It is shown that the optimal puncturing of the inner code depends on the outer code, i.e., it is interleaver dependent. This dependence cannot be tracked by the analysis for standard SCCCs, which fails in predicting code performance. Based on the considerations arising from the bounds analysis, we construct a family of rate-compatible SCCCs with a high level of flexibility and a good performance over a wide range of code rates, using simple constituent codes. The error rate performance of the proposed codes is found to be better than that of standard SCCCs, especially for high rates, and comparable to the performance of more complex turbo codes. [ABSTRACT FROM AUTHOR]

Efficient operation of cognitive personal area networks (CPANs) necessitates accurate and efficient sensing of the primary user activity. This is accomplished in a cooperative manner by a number of nodes in the CPAN; the results of sensing are combined by the CPAN coordinator to form a comprehensive and timely channel map. The error of the sensing process is affected by various factors, including the ratio of the number of sensing nodes to the number of channels. In this paper, we present a probabilistic model of the sensing process and derive an analytical solution for the minimum number of sensing nodes that keeps the sensing error below prescribed limits. Then, we discuss three differential sensing policies in which separate sets of sensing nodes target idle and active channels only and show that the policy in which idle channels are given priority, but not exclusive treatment, achieves the best performance, as measured by the number of channels for which the information in the channel map is erroneous and the mean duration of that erroneous information. [ABSTRACT FROM AUTHOR]

This paper presents a novel Reed-Solomon codes based transmission scheme called RS-SC-CP. While RS-SC-CP is essentially a Reed-Solomon (RS) coded single carrier with cyclic prefix (SC-CP) system, a filter bank representation of the RS code is used. This filter bank representation unveils a DFT synthesis bank, just as in a traditional Orthogonal Frequency Division Multiplexing (OFDM) system (allbeit in a finite field). Therefore, RS-SC-CP is topologically equivalent with OFDM. As such, the RS-SC-CP system inherits the advantages of an SC-CP system over a traditional OFDM system like a low Peak to Average Power Ratio (PAPR). But, more importantly, it allows us to use a novel equalization technique that resembles a traditional OFDM equalizer. The equalizer of an RS-SC-CP receiver is split into two stages: the first stage encompasses a partial equalization in the complex field, which ensures that the residual channel response has integer coefficients. It is calculated using a Minimum Mean Square Error (MMSE) criterion. The residual ISI is removed by a Galois field equalizer in the second stage, posterior to the RS decoding removing the noise. Finally, the performance of the RS-SC-CP system is further evaluated by simulations showing the performance gain of the RS-SC-CP system compared to a traditional coded OFDM or Single Carrier with Cyclic Prefix (SC-CP) scheme. [ABSTRACT FROM AUTHOR]

In this paper a decision-directed Multiple-Input Multiple-Output (MIMO) channel tracking algorithm is enhanced to raise the channel estimate accuracy. While DDCE is prone to error propagation the enhancement employs channel decoding in the tracking process. Therefore, a quantized block of symbols is checked on consistency via the channel decoder, possibly corrected and then used. This yields a more robust tracking of the channel in terms of bit error rate and improves the channel estimate under certain conditions. Equalization is performed to prove the feasibility of the obtained channel estimate. Therefore a combined signal consisting of data and pilot symbols is sent. Adaptive filters are applied to exploit correlations in time, frequency and spatial domain. By using good error-correcting coding schemes like Turbo Codes or Low Density Parity Check (LDPC) codes, adequate channel estimates can be acquired even at low signal to noise ratios (SNR). The proposed algorithm among two others is applied for channel estimation and equalization and results are compared. [ABSTRACT FROM AUTHOR]

Multiple-input multiple-output (MIMO) system with multicode transmission can provide high speed data services by transmitting independent parallel substreams from multiple antennas and through multicode channelization. In this paper, we first introduce an iterative two-stage successive interference cancellation (SIC) detection scheme for a multicode MIMO system. The proposed technique cancels the interference signals successively in the space domain followed by the code domain. Next, we develop various transmit power allocation schemes over different data substreams for the proposed detection process to improve error rate performance. The joint transmit power allocation is derived to make the post-detection signal-to-interferenceplus-noise ratio (SINR) become the same for all substreams in both the space and code domains. As a computationally efficient scheme, we propose a two stage power allocation scheme, which allocates the total transmit power to the substreams in the code domain at the first stage, and allocates this code domain power to the substreams in the space domain at the second stage. Furthermore, variable and constant power ratio (PR) schemes are derived to reduce the feedback overhead. In particular, the constant PR scheme utilizes the transmit power ratio determined by the long-term statistical properties of the fading channel amplitudes, and achieves significantly reduced feedback rate. Numerical results show that the proposed transmit power allocation schemes for the two-stage SIC significantly outperform the equal power allocation scheme. [ABSTRACT FROM AUTHOR]

Tardos has proposed a randomized fingerprinting code that is provably secure against collusion attacks. We revisit his scheme and show that it has significantly better performance than suggested in the original paper. First, we introduce variables in place of Tardos' hard-coded constants and we allow for an independent choice of the desired false positive (FP) and false negative (FN) error rates. Following through Tardos' proofs with these modifications, we show that the code length can be reduced by more than a factor of two in typical content distribution applications where high FN rates can be tolerated. Second, we study the statistical properties of the code. Under some reasonable assumptions, the accusation sums can be regarded as Gaussian-distributed stochastic variables. In this approximation, the desired error rates are achieved by a code length twice shorter than in the first approach. Overall, typical FP and FN error rates may be achieved with a code length approximately five times shorter than in the original construction. [ABSTRACT FROM AUTHOR]

In this paper, a new channel-estimation algorithm based on maximum-likelihood (ML) algorithm for estimation and tracking of the multiple-input-multiple-output (MIMO) channels is presented. The ML algorithm presents the optimum estimation when the exact channel model is known. The derived channel-estimation algorithm is very efficient, with a computational complexity comparable to the least mean square and much lower than the recursive least squares and the Kalman algorithms. The proposed algorithm is analyzed, and the effect of the channel-tracking error is applied as a modifying component for the derived algorithm. The proposed algorithm is simulated for half- and full-rank flat-fading time-varying MIMO channels for the different values of fDT, Eb/No, and training lengths via Monte Carlo simulation technique. The minimum mean-square-error (mmse) joint detector is considered as the detection algorithm. The output of the mmse receiver is considered as the virtual training data in the blind mode of operation: the same as in the decision-directed algorithm. By various simulations, the bit error rate and the mse of tracking the proposed algorithm for different values of fDT, presenting the speed of channel variations, are evaluated and compared with the Kalman filtering approach. By simulating the proposed algorithm for different values of the training length, the minimum training length required for different channel conditions is extracted. [ABSTRACT FROM AUTHOR]

This paper studies pulse-based M-ary ultrawide-band communications analyzing both the symbol error rate (SER) and the information theoretic capacity C for single-link communications over both additive white Gaussian noise and multipath channels (taking into account random variations in both energy and correlation values). In particular, we consider M-ary N-orthogonal pulse-position-modulated (PPM) signals with numerical pulse-position optimization to exploit the negative values in the pulse correlation function. On one hand, the N-orthogonal PPM (N-OPPM) signals can accommodate a larger value of M than the nonoverlapping orthogonal PPM (OPPM) signals for a constant frame size and pulse width, allowing increasing the symbol transmission rate and/or the use of error correcting codes. However, N-OPPM requires a receiver with N correlators, while the receiver for OPPM requires one correlator. On the other hand, the pulse positions of the N-OPPM signals can be manipulated to shape the power spectrum density and decrease the level of the discrete components. However, this PPM manipulation changes the N-OPPM correlation properties of the signal set. At the same time, N-OPPM signals have equal or better performance than OPPM signals. More specifically, simulations show that for low values of M, the N-OPPM has lower SER and higher C than OPPM for the same signal-to-noise ratio (SNR), and that for larger values of M, it achieves similar SER and C. Hence, N-OPPM signals allow a tradeoff between transmission rate, signal performance, and receiver complexity. [ABSTRACT FROM AUTHOR]

It is well-known that the Euclidean algorithm can be used o find the systematic errata-locator polynomial and the errata-evaluator polynomial simultaneously in Berlekamp's key equation that is needed to decode a Reed-Solomon (RS) codes. In this paper, a simplified decoding algorithm to correct both errors and erasures is used in conjunction with the Euclidean algorithm for efficiently decoding nonsystematic RS codes. In fact, this decoding algorithm is an appropriate modification to the algorithm developed by Shiozaki and Gao. Based on the ideas presented above, a fast algorithm described from Blahut's classic book is derivated and proved in this paper to correct erasures as well as errors by replacing the Euclidean algorithm by the Berlekamp-Massey (BM) algorithm. These facts lead to significantly reduce the decoding complexity of the proposed RS decoder. In addition, computer simulations show that this simple and fast decoding technique reduces the decoding time when compared with existing efficient algorithms including the new Euclidean-algorithm-based decoding approach proposed in this paper. [ABSTRACT FROM AUTHOR]

This paper analyzes construction algorithms for low-density parity-check (LDPC) codes with respect to their unequal error protection (UEP) capabilities. We show that the choice of code construction algorithm highly affects the performance and UEP properties of LDPC codes with identical degree distributions. Our results provide an explanation to disagreements in earlier research. [ABSTRACT FROM PUBLISHER]