This paper shows a fast simulation method of low-density parity-check (LDPC) codes over an additive non-Gaussian noise channel. The evaluation of an error performance of LDPC codes is usually executed by using a Monte-Carlo simulation since the theoretical calculation method has not been reported. It is very difficult to evaluate an error performance of LDPC codes with finite block length when the error probability is very low. To solve this problem, some fast simulation methods by using importance sampling (IS) are proposed. However, the conventional methods can not reduce the simulation time of LDPC codes over an additive non-Gaussian noise channel because the simulation probability density function (PDF) used in IS is designed for an additive white Gaussian noise. We propose a new simulation PDF design related to the Chernoff bound to estimate an error performance of LDPC codes over an additive non-Gaussian noise channel. In addition, we show some numerical examples to demonstrate the effectiveness of the proposed simulation method. The simulation time of the proposed method is reduced to about 1/2000 of that of the conventional method when we estimate the frame error rate of 10−10.
This paper shows a fast simulation method of low-density parity-check (LDPC) codes over an additive non-Gaussian noise channel. The evaluation of an error performance of LDPC codes is usually executed by using a Monte-Carlo simulation since the theoretical calculation method has not been reported. It is very difficult to evaluate an error performance of LDPC codes with finite block length when the error probability is very low. To solve this problem, some fast simulation methods by using importance sampling (IS) are proposed. However, the conventional methods can not reduce the simulation time of LDPC codes over an additive non-Gaussian noise channel because the simulation probability density function (PDF) used in IS is designed for an additive white Gaussian noise. We propose a new simulation PDF design related to the Chernoff bound to estimate an error performance of LDPC codes over an additive non-Gaussian noise channel. In addition, we show some numerical examples to demonstrate the effectiveness of the proposed simulation method. The simulation time of the proposed method is reduced to about 1/2000 of that of the conventional method when we estimate the frame error rate of 10−10.
This paper shows a fast estimation method of very low error rate of low-density parity-check (LDPC) codes. No analytical tool is available to evaluate performance of LDPC codes, and the traditional Monte Carlo simulation methods can not estimate the low error rate of LDPC codes due to the limitation of time. To conquer this problem, we propose another simulation method which is based on the optimal simulation probability density function (PDF). The proposed simulation PDF can also avoid the dependency between the simulation time and the number of dominant trapping sets, which is the problem of some fast simulation methods based on the error event simulation method. Additionally, we show some numerical examples to demonstrate the effectiveness of the proposed method. The simulation time of the proposed method is reduced to almost less than 1/10 of that of Cole et al.'s method under the condition of the same accuracy of the estimator.
This study shows a new design method of a simulation probability density function (PDF) for a fast frame error rate (FER) evaluation of low-density parity-check (LDPC) codes. It is difficult to evaluate a very low FER of LDPC codes by Monte Carlo simulation methods since it has excellent performance under iterative decoding. Cole et al. proposed a three-step estimation method of the low FER of LDPC codes of moderate block length. By applying the importance sampling method, which is one of the fast simulation methods, the simulation time of the error performance of LDPC codes can be reduced. Another simulation PDF, which can treat more dominant trapping sets (TS) than Cole et al.'s method, is proposed. The selection of the dominant TS as proportional to its probability reduces the number of simulation runs without deteriorating the accuracy of the estimator. Unbiased estimator is given as well as that that of the Cole et al.'s method. Some numerical examples are shown to demonstrate the effectiveness of the proposed method. The simulation time for an LDPC code of length 504 is reduced to 1/10 when we evaluate FER of around 10-14.
This paper shows a fast simulation method of low-density parity-check (LDPC) codes by using importance sampling (IS). In IS, the design of the simulation probability density function (PDF) plays a very important role to reduce the simulation time. We derive the optimal simulation PDF, which can reduce the variance of the estimator to zero. Since the optimal simulation PDF includes true error probability, it can not be utilized in the practical simulation. The simulation PDF which approximates the optimal simulation PDF is proposed. In addition, we show some numerical examples to show the effectiveness of the proposed simulation method.
In this paper, we propose an estimation method of a very low bit error rate (HER) of low-density parity-check (LDPC) codes. No analytical tool is available to evaluate performance of LDPC codes, and traditional Monte Carlo simulation methods can not estimate low HER of LDPC codes due to the limitation of time. Cole et al, show a fast frame error rate simulation method of LDPC codes by applying importance sampling (IS). At first, we extend Cole et aI.'s method to the HER estimation of LDPC codes. Since the simulation time of the HER evaluation version of the Cole et aI.'s method is proportional to the number of total dominant trapping sets used in the simulation, we should appropriately choose the dominant trapping sets to reduce the simulation time. To avoid the difficulty, we propose another simulation method, which selects a dominant trapping set as proportional to its upper bound. Additionally, we show some numerical examples to demonstrate the effectiveness of the proposed method. When we evaluate HER of 10−16, the simulation time of the proposed method is reduced to 1/6.6 of that of the HER evaluation version of the Cole et al.'s method under the condition of the same accuracy of the estimator.
Elementary trapping sets (ETSs) have been found to be the main cause of error floor in the decoding of low-density parity-check (LDPC) codes. Moreover, irregular LDPC codes that avoid harmful [w; u; e] ETSs have been constructed and have shown to possess superior error performance compared with other LDPC codes. In this paper, we attempt to evaluate irregular LDPC code performance under an additive white Gaussian noise channel within the high SNR region using the importance sampling (IS) approach in conjunction with the identification of [w; u; e] ETSs. For any given irregular LDPC code, we will first apply a three-step method that aims to search as many ETSs within the code as possible. Then, we will classify these ETSs into different groups based on their labels, i.e., [w; u; e]'s. Further, by dividing the error region into various sub-regions centered by ETSs, we apply the IS simulator to evaluate the error rate of each of the sub-regions. Based on the error rates of all the sub-regions, we can estimate the overall error rate of the LDPC code. Results have indicated that our proposed IS scheme can produce speed-up gains up to 3.9×109 times compared to Monte Carlo simulations.
The error-correcting performance of low-density parity check (LDPC) codes, when decoded using practical iterative decoding algorithms, is known to be close to Shannon limits for codes with suitably large blocklengths. A substantial limitation to the use of finite-length LDPC codes is the presence of an error floor in the low frame error rate (FER) region. This paper develops a deterministic method of predicting error floors, based on high signal-to-noise ratio (SNR) asymptotics, applied to absorbing sets within structured LDPC codes. The approach is illustrated using a class of array-based LDPC codes, taken as exemplars of high-performance structured LDPC codes. The results are in very good agreement with a stochastic method based on importance sampling which, in turn, matches the hardware-based experimental results. The importance sampling scheme uses a mean-shifted version of the original Gaussian density, appropriately centered between a codeword and a dominant absorbing set, to produce an unbiased estimator of the FER with substantial computational savings over a standard Monte Carlo estimator. Our deterministic estimates are guaranteed to be a lower bound to the error probability in the high SNR regime, and extend the prediction of the error probability to as low as 10-30. By adopting a channel-independent viewpoint, the usefulness of these results is demonstrated for both the standard Gaussian channel and a channel with mixture noise.