Soft error modeling and remediation techniques in ASIC designs

Soft errors due to cosmic radiations are the main reliability threat during lifetime operation of digital systems. Fast and accurate estimation of soft error rate (SER) is essential in obtaining the reliability parameters of a digital system in order to balance reliability, performance, and cost of the system. Previous techniques for SER estimation are mainly based on fault injection and random simulations. In this paper, we present an analytical SER modeling technique for ASIC designs that can significantly reduce SER estimation time while achieving very high accuracy. This technique can be used for both combinational and sequential circuits. We also present an approach to obtain uncertainty bounds on estimated error propagation probability (EPP) values used in our SER modeling framework. Comparison of this method with the Monte-Carlo fault injection and simulation approach confirms the accuracy and speed-up of the presented technique for both the computed EPP values and uncertainty bounds.Based on our SER estimation framework, we also present efficient soft error hardening techniques based on selective gate resizing to maximize soft error suppression for the entire logic-level design while minimizing area and delay penalties. Experimental results confirm that these techniques are able to significantly reduce soft error rate with modest area and delay overhead.     

Characterizing,modeling, and analyzing soft error propagation in asynchronous and synchronous digital circuits

Soft errors, due to cosmic radiations, are one of the major challenges for reliable VLSI designs. In this paper, we present a symbolic framework to model soft errors in both synchronous and asynchronous designs. The proposed methodology utilizes Multiway Decision Graphs (MDGs) and glitch-propagation sets (GP sets) to obtain soft error rate (SER) estimation at gate level. This work helps mitigate design for testability (DFT) issues in relation to identifying the controllable and the observable circuit nodes, when the circuit is subject to soft errors. Also, this methodology allows designers to apply radiation tolerance techniques on reduced sets of internal nodes. To demonstrate the effectiveness of our technique, several ISCAS89 sequential and combinational benchmark circuits, and multiple asynchronous handshake circuits have been analyzed. Results indicate that the proposed technique is on average 4.29 times faster than the best contemporary state-of-the-art techniques. The proposed technique is capable to exhaustively identify soft error glitch propagation paths, which are then used to estimate the SER. To the best of our knowledge, this is the first time that a decision diagram based soft error identification approach is proposed for asynchronous circuits.     

Channel estimation technique in multi-antenna AF relay communication systems

The channel estimation technique is investigated in OFDM communication systems with multi-antenna Amplify-and-Forward (AF) relay. The Space-Time Block Code (STBC) is applied at the transmitter of the relay to obtain diversity gain. According to the transmission characteristics of OFDM symbols on multiple antennas, a pilot-aided Linear Minimum Mean-Square-Error (LMMSE) channel estimation algorithm with low complexity is designed. Simulation results show that, the proposed LMMSE estimator outperforms least-square estimator and approaches the optimal estimator without error in the performance of Symbol Error Ratio (SER) under several modulation modes, and has a good estimation effect in the realistic relay communication scenario.     

Error probability minimizing pilots for OFDM with M-PSK modulation over Rayleigh-fading channels

Orthogonal frequency division multiplexing (OFDM) with pilot symbol assisted channel estimation is a promising technique for high rate transmissions over wireless frequency-selective fading channels. In this paper, we analyze the symbol error rate (SER) performance of OFDM with M-ary phase-shift keying (M-PSK) modulation over Rayleigh-fading channels, in the presence of channel estimation errors. Both least-squares error (LSE) and minimum mean-square error (MMSE) channel estimators are considered. For prescribed power, our analysis not only yields exact SER formulas, but also quantifies the performance loss due to channel estimation errors. We also optimize the number of pilot symbols, the placement of pilot symbols, and the power allocation between pilot and information symbols, to minimize this loss, and thereby minimize SER. Simulations corroborate our SER performance analysis, and numerical results are presented to illustrate our optimal claims.     

Binomial distribution based grey wolf optimization algorithm for channel estimation in wireless communication system

Several input high-data-rate transmissions over broadband wireless channels are possible using multiple input multiple output (MIMO) systems paired with orthogonal frequency division multiplexing (OFDM) technology. Channel estimation is an essential technique and a necessary component of MIMO-OFDM systems. However, the noise will be there in MIMO-OFDM due to the environment. As a result, the wireless system performs degrades in terms of bit error rate (BER). The suggested method offers a better pilot pattern strategy for MIMO-OFDM and an efficient power allocation to address this issue. The binomial distribution-based grey wolf optimization (BDGWO) algorithm is proposed to identify the optimal pilot patterns. The power is then adaptively distributed to each transmit antenna to increase the spectral efficiency and maximum channel capacity through an adaptive neuro-fuzzy inference system with a sigmoid membership function (SMFANFIS). The best pilot patterns in PDGSIP (pilot design with generalized shift invariant property) were determined using the BDGWO algorithm based on the binomial distribution. According to the simulation results, the proposed BDGWO established pilot design with generalized shift invariant property (BDGWO-DGSIP) achieves higher performance compared other existing approaches such as PDGSIP, TPDGSIP, and LS in terms of NMSE, BER, and SER. Compared to the PDGSIP technique, the proposed PDGSIP-BDGWO system minimizes NMSE at 10%, BER at about 12%, and SER at 15%.     

估计误差下DF协作系统性能分析

信道估计误差是引起无线通信系统性能衰弱的重要因素之一。分析了瑞利信道条件下估计误差对译码前传协作系统性能的影响。推导并给出了估计误差条件下正交幅度调制信号译码前传协作系统码元错误概率的解析表达式和上界表达式,并分析了不同信道的方差对协作系统性能的影响。仿真结果显示,存在估计误差时,码元错误概率性能并未随着信噪比的增大而提高。同时发现,中继-目的链路的较大方差较源-中继链路显著改善码元错误概率性能。     

Analysis of SER of MIMO‐MRC systems with imperfect channel estimation in the presence of non‐Rayleigh CCIs

In this paper, we study the average symbol error rate (SER) for a multiple input multiple output (MIMO) maximal ratio combining (MRC) system with Rayleigh fading desired signal in the presence of non‐Rayleigh fading co‐channel interferers (CCIs) and additive white Gaussian noise (AWGN). To simulate the actual environments of wireless transmission, we assume that the transceiver only obtains imperfect channel estimation (ICE). For the cases of Nakagami and Rician fading CCIs, analytic expressions for the SER have been derived approximately by introducing the modified signal‐to‐interference and noise power ratio (SINR) that can be obtained by averaging the CCI term in the original SINR over the distribution of ICE of intended user. These formulas can provide important reference of design of MIMO diversity systems. Numerical simulations verify the effectiveness of these formulas. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimal diversity combining based on linear estimation of rician fading channels

Optimal receiver diversity combining employing linear channel estimation is examined. Based on the statistical properties of least-squares (LS) and minimum mean square error (MMSE) channel estimation, an optimal diversity receiver for wireless systems employing practical linear channel estimation on Rician fading channels is proposed. The new receiver structure includes the conventional maximal ratio combining receiver as a special case. Exact analytical expressions for the symbol error rates (SERs) of LS and MMSE channel estimation aided optimal diversity combining are derived. It is shown that, if an optimal detector is used, an MPSK wireless system with MMSE channel estimation has the same SER when the MMSE channel estimation is replaced by LS estimation. This is an interesting counterexample to the common perception that channel estimation with smaller mean square error leads to smaller SER. Extensive simulation results validate the theoretical results.     

Performance analysis of maximum likelihood detection in a MIMOantenna system

We provide an analysis of the performance of maximum likelihood detection (MLD) over flat fading channels in a wireless multiple input-multiple output (MIMO) antenna system. A tight union bound with an asymptotic form on the probability of symbol error rate (SER) for MIMO MLD systems with two-dimensional signal constellations (such as QAM and PSK) is introduced. Using this analytic bound, the performance of the MIMO antenna system is demonstrated quantitatively with respect to channel estimation, constellation size, and antenna configuration     

Error propagation analysis of V-BLAST with channel-estimation errors

In this letter, expressions are given for the symbol-error rate (SER) of the Vertical Bell Laboratories Layered Space-Time (V-BLAST) system, taking into account error propagation due to channel-estimation errors. In addition to error propagation, suboptimal substream ordering due to imperfect channel estimates is accounted for. First, the conditional SER is determined using the distribution of the signal-to-interference-plus-noise ratio of each substream, conditioned on the channel estimate. Then, the average SER as a function of the channel estimation error-to-signal ratio (ESR) is upper bounded by averaging over the distribution of the channel estimates. The upper bound on the SER is tighter than previous bounds in the literature. Comparisons with exact simulations demonstrate the accuracy of the SER expressions for a large range of ESRs.     

A Fast Statistical Soft Error Rate Estimation Method for Nano-scale Combinational Circuits

Nano-scale digital integrated circuits are getting increasingly vulnerable to soft errors due to aggressive technology scaling. On the other hand, the impacts of process variations on characteristics of the circuits in nano era make statistical approaches as an unavoidable option for soft error rate estimation procedure. In this paper, we present a novel statistical Soft Error Rate estimation framework. The vulnerability of the circuits to soft errors is analyzed using a newly defined concept called Statistical Vulnerability Window (SVW). SVW is an inference of the necessary conditions for a Single Event Transient (SET) to cause observable errors in the given circuit. The SER is calculated using a probabilistic formulation based on the parameters of SVWs. Experimental results show that the proposed method provides considerable speedup (about 5 orders of magnitude) with less than 5 % accuracy loss when compared to Monte-Carlo SPICE simulations. In addition, the proposed framework, keeps its efficiency when considering a full spectrum charge collections (more than 36X speedups compared to the most recently published similar work).     

Performance analysis of dual-hop fixed-gain AF relaying systems with OSTBC over Nakagami-m fading channels

In this paper, we present outage probability and symbol error rate (SER) performance analyses of a dual-hop transmission using fixed-gain amplify-and-forward relaying in flat Nakagami-m fading channels. The system under consideration is equipped with multiple antennas at source and destination adopting orthogonal space-time block coding to provide transmit diversity and maximum ratio combining to provide receive diversity, respectively. For integer and half-integer m values, closed forms of exact outage probability and moment generating function (MGF) expressions are derived through cumulative distribution function (CDF) of the overall system signal-to-noise ratio. Closed-form exact SER expressions based on the overall CDF are obtained for binary phase shift keying, binary frequency shift keying and M-ary pulse amplitude modulation. Exact SER expressions based on the MGF method are also obtained for binary differential phase shift keying, M-ary phase shift keying and M-ary quadrature amplitude modulation. Moreover, the asymptotic diversity order analysis is performed through derivations of asymptotic outage probability and SER. Theoretical analyses are validated by Monte Carlo simulations showing perfect match between each other.     

QoS‐aware packet forwarding in MIMO sensor networks: a cross‐layer approach

Multiple‐input multiple‐output (MIMO) enabled wireless sensor networks (WSNs) are becoming increasingly important since significant performance enhancement can be realized. In this paper, we propose a packet forward strategy for MIMO sensor networks by jointly considering channel coding, rate adaptation, and power allocation. Each sensor node has multiple antennas and uses orthogonal space time block codes (OSTBC) to exploit both spatial and temporal diversities. The objective is to determine the optimal routing path that achieves the minimum symbol error rate (SER) subject to the source‐to‐destination (S‐D) energy consumption constraint. This SER‐based quality‐of‐service (QoS) aware packet forwarding problem is formulated into the framework of dynamic programming (DP). We then propose a low‐complexity and near‐optimal approach to considerably reduce the computation complexity, which includes state space partition and state aggregation techniques. Simulations indicate that the proposed protocol significantly outperforms traditional algorithms. Further still, the performance gain increases with tighter S‐D energy constraint. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of channel estimation on the performance of a coherentDS-CDMA system

Direct-sequence code division multiple access (DS-CDMA) has become one of the favourite candidates for future mobile radio communication systems. The uplink of a coherent DS-CDMA system is investigated. The channel estimation is carried out via a control channel, which is transmitted simultaneously to the data channel. This concept is very closely related to the CODIT-CDMA concept. In the channel estimation, an averaging process is involved, which for long averaging periods, suppresses the noise influence efficiently. On the other hand, long averaging intervals lead to systematic errors in the estimated channel coefficients due to the time-variant behavior of the channel. Taking into account these effects, a closed-form analysis of the data-channel symbol-error rate (SER) is presented. This analysis allows the prediction of the system's performance and helps to optimize the parameter settings for channel estimation     

A Novel Multiuser Detection Algorithm for CDMA-Based MIMO-OFDM System

1Introduction Recently,MultipleInputMultipleOutput(MIMO)wirelesstechnologieshavecapturedalotofresearchin terest,giventhatthecapacityincreaseturnsouttobe achievable[1-2].OrthogonalFrequencyDivisionMulti plexing(OFDM)techniquehastheremarkablecharac teristic…     

Single-event multiple transients in guard-ring hardened inverter chains of different layout designs

Single-event multiple transients (SEMTs) measurement based on an on-chip self-triggered method is performed. Measurement results for guard-ring hardened inverter chains of two layout designs, including a source/drain sharing design and a conventional design, are compared under pulsed laser irradiation. Pulsed laser exposures with different energies show that the guard-ring hardened inverter chain with a source/drain sharing design is more sensitive to single-event double transients (SEDTs). It is found that SEDTs with small temporal differences can be merged into single-event single transients (SESTs) thanks to the pulse broadening effect. A layout-hardened design for SEDTs in the guard-ring hardened inverter chain is also suggested.     

Cosmic-ray soft error rate characterization of a standard 0.6-μmCMOS process

Cosmic-ray soft errors from ground level to aircraft flight altitudes are caused mainly by neutrons. We derived an empirical model for estimation of soft error rate (SER). Test circuits were fabricated in a standard 0.6-μm CMOS process. The neutron SER dependence on the critical charge and supply voltage was measured. Time constants of the noise current were extracted from the measurements and compared with device simulations in three dimensions. The empirical model was calibrated and verified by independent SER measurements. The model is capable of predicting cosmic-ray neutron SER of any circuit manufactured in the same process as the test circuits. We predicted SER of a static memory cell     

Efficient algorithms to accurately compute derating factors of digital circuits

Fast, accurate, and detailed Soft Error Rate (SER) estimation of digital circuits is essential for cost-efficient reliable design. A major step to accurately estimate a circuit SER is the computation of failure probability, which requires the computation of three derating factors, namely logical, electrical, and timing derating. The unified treatment of these derating factors is crucial to obtain accurate failure probability. Existing SER estimation techniques are either unscalable to large circuits or inaccurate due to lack of unified treatment of all derating factors. In this paper, we present fast and efficient algorithms to estimate SERs of circuit components in the presence of single event transients by unified computation of all derating factors. The proposed algorithms, based on propagation of error probabilities and shape of erroneous waveforms, are scalable to very large circuits. The experimental results and comparisons with Statistical Fault Injections (SFIs) using Monte-Carlo simulations confirm the accuracy (only 2% difference) and speedup (5–6 orders of magnitudes) of the proposed technique.     

Estimating symbol error rate vs. carrier to noise in IQ modulatedsystems based on digitization of constellation and statistical models

Methods used to characterize the degradation of symbol error rate (SER) vs. carrier-to-noise ratio (C/N) performance of several different components of systems that broadcast digital video signals are presented. The techniques are based on repetitively sampling and then digitizing the IQ constellation at baseband. Mathematically different levels of noise calculated relative to the carrier are added to the digitized constellation. Examination of the resulting distributions of noise versus error thresholds allows the estimation of SER vs. C/N in the absence of any error correction in the receiver. The effects of IF bandwidth and transmit and receive filters are also taken into account. The estimated SER vs. C/N can be plotted and compared to the theoretical SER vs. C/N for the modulation format, IF bandwidth, and transmit and receive filters in the system under test     

Recursive short-data-record estimation of AV and MMSE/MVDR linear filters for DS-CDMA antenna array systems

The presence of the desired signal during estimation of the minimum mean-square error (MMSE)/minimum-variance distortionless-response (MVDR) and auxiliary-vector (AV) filters under limited data support leads to significant signal-to-interference-plus-noise ratio (SINR) performance degradation. We quantify this observation in the context of direct-sequence code-division multiple-access (DS-CDMA) communications by deriving close approximations for the mean-square filter estimation error, the probability density function of the output SINR, and the probability density function of the symbol-error rate (SER) of the sample matrix inversion (SMI) receiver evaluated using both a desired-signal-"present" and desired-signal-"absent" input covariance matrix. To avoid such performance degradation, we propose a DS-CDMA receiver that utilizes a simple pilot-assisted algorithm that estimates and then subtracts the desired signal component from the received signal prior to filter estimation. Then, to accommodate decision-directed operation, we develop two recursive algorithms for the on-line estimation of the AV and MMSE/MVDR filter and we study their convergence properties. Finally, simulation studies illustrate the SER performance of the overall receiver structures.