Improving the tolerance of stochastic LDPC decoders to overclocking-induced timing errors: a tutorial and design example

Channel codes such as Low-Density Parity-Check (LDPC) codes may be employed in wireless communication schemes for correcting transmission errors. This tolerance to channel-induced transmission errors allows the communication schemes to achieve higher transmission throughputs, at the cost of requiring additional processing for performing LDPC decoding. However, this LDPC decoding operation is associated with a potentially inadequate processing throughput, which may constrain the attainable transmission throughput. In order to increase the processing throughput, the clock period may be reduced, albeit this is at the cost of potentially introducing timing errors. Previous research efforts have considered a paucity of solutions for mitigating the occurrence of timing errors in channel decoders, by employing additional circuitry for detecting and correcting these overclocking-induced timing errors. Against this background, in this paper we demonstrate that stochastic LDPC decoders (LDPC-SDs) are capable of exploiting their inherent error correction capability for correcting not only transmission errors, but also timing errors, even without the requirement for additional circuitry. Motivated by this, we provide the first comprehensive tutorial on LDPC-SDs. We also propose a novel design flow for timing-error-tolerant LDPC decoders. We use this to develop a timing error model for LDPC-SDs and investigate how their overall error correction performance is affected by overclocking. Drawing upon our findings, we propose a modified LDPC-SD, having an improved timing error tolerance. In a particular practical scenario, this modification eliminates the approximately 1 dB performance degradation that is suffered by an overclocked LDPC-SD without our modification, enabling the processing throughput to be increased by up to 69.4%, which is achieved without compromising the error correction capability or processing energy consumption of the LDPC-SD

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

AIM: The SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery. METHODS: This was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin. RESULTS: Overall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P < 0.001). After adjustment, delay was not associated with a lower rate of complete resection (OR 1.18, 95% CI 0.90-1.55, P = 0.224), which was consistent in elective patients only (OR 0.94, 95% CI 0.69-1.27, P = 0.672). Longer delays were not associated with poorer outcomes. CONCLUSION: One in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Timing-error-tolerant iterative decoders

Iterative decoders such as Low-Density Parity-Check (LDPC) and turbo decoders have an inherent capability to correct the transmission errors that originate during communication over a hostile wireless channel. This capability has engendered the widespread use of LDPC and turbo decoders in current communications standards. As a result, signficant research efforts have been made in order to conceive efficient Very-Large-Scale Integration (VLSI) implementations of both LDPC and turbo decoders. Typically, these efforts have focused on optimizing only one of the various trade-offs associated with the hardware implementation of iterative decoders, such as the chip area, latency, throughput, energy efficiency or Bit Error Ratio (BER) performance. However, tolerance to timing errors that occur during the iterative decoding processing are typically not considered in these implementations. Owing to this, the BER performance and hardware efficiency of the proposed designs may be severely degraded, if timing errors occur during the iterative decoding process.Against this background, this thesis demonstrates that iterative decoders are capable of exploiting their inherent error correction capability to correct not only transmission errors, but also timing errors caused by overclocking and power supply variations. Moreover,we propose modifications to the iterative decoders designs, which further enhance their inherent tolerance to timing errors. We achieve this by considering the close relationship between the different trade-offs associated with the hardware implementation of iterative decoders, with the aim of achieving Pareto optimality, where none of these trade-offs can be further improved without degrading at least one of the others. Owing to this, our proposed timing-error-tolerant design methodology simultaneously considers the design constraints and parameters that affect not only the BER performance, but also the hardware efficiency of each implementation.We first investigate the benefits of stochastic computing in iterative decoders, by characterizing the inherent timing-error tolerance of Stochastic LDPC Decoders (SLDPCDs) and Stochastic Turbo Decoders (STDs). Moreover, we propose modifications to the SLDPCD and STD in order to further improve their inherent tolerance to timing errors. This is achieved by performing extensive transistor-level and post-layout simulations, in order to develop different timing analyses for determining the causes and effects of timing errors in these stochastic decoders. Following this, we propose a novel Reduced-Latency STD (RLSTD), which improves the latency of the state-of-the-art STD by an order of magnitude, without increasing its chip area or energy consumption. Our experimental results demonstrate that our proposed RLSTD achieves ultra-low-latencies required by next-generation Mission-Critical Machine-Type Communication (MCMTC).We also investigate the inherent tolerance to timing errors of a recently-proposed Fully-Parallel Turbo Decoder (FPTD). Furthermore, we propose a novel Reduced-Critical-Path Fully-Parallel Turbo Decoder (RCP-FPTD) algorithm and the employment of Better-Than-Worst-Case (BTWC) design techniques in FPTD and RCP-FPTD implementations, for the sake of improving their throughput and their tolerance to timing errors caused by overclocking. We demonstrate that the FPTD and RCP-FPTD implementations improve the throughput of the state-of-the-art turbo decoder by an order of magnitude. Finally, despite operating in the presence of timing errors, our proposed Better-Than-Worst-Case Reduced-Critical-Path Fully-Parallel Turbo Decoder (BTWC-RCP-FPTD) achieves throughputs on the order of tens of Gbps, which may be expected to be a requirement in next-generation wireless communication standards

Supplemental data of Stochastic Computing Improves the Timing-Error Tolerance and Latency of Turbo Decoders: Design Guidelines and Trade-offs

Supplemental data pertaining to different hardware implementations of Stochastic Turbo Decoders using TSMC 90nm technology. The data was obtained from the physical layout using automatic place and route with Cadence SoC Encounter.</span

Improving the Tolerance of Stochastic LDPC Decoders to Overclocking-Induced Timing Errors: A tutorial and Design Example

The header &quot;EbN0&quot; represents the ratio between the average energy used to transmit a bit and the noise power spectral density. The header &quot;BER&quot; represents the bit error ratio. Each column labelled as BER is plotted as a curve in the figures of the paper, corresponding to one of the set of scheme, namely the set of (628.3, 0.01), (718.8, 0.01), (718.8, 0.1), (1217.3, 0.1) and (1217.3, 0.3) for using 90nm fabrication technology and the set of (760.0, 0.01), (869.5, 0.1), (1171.2, 0.1), (1472.8, 0.1) and (1472.8, 0.3) for using 45nm fabrication technology. The order of the BER columns follows the same order as stated above.</span

Fisheries in southern Brazil: a comparison of their management and sustainability

Defined as operational units, the estuarine and marine fishing production systems (FPS) from the two southernmost states of Brazil, Santa Catarina and Rio Grande do Sul were analyzed using the RAPFISH technique with respect to sustainability of fisheries. The FPS were defined by 49 attributes divided into five fields: economic, social, ecological, technological and managerial. Data were obtained from the literature and interviews with fishers, skippers, and ship owners in 2003 and 2004. Overall, 26 FPS were identified: nine small-scale; three medium-scale; ten large-scale operating on the shelf, upper slope or nearby oceanic waters; and four large-scale fishing systems on the upper slope or neighboring oceanic waters. The latter included only foreign vessels, which produced frozen products exclusively for export. Analyses of 15 selected attributes more closely associated with sustainability in the five fields of evaluation showed all FPS in an intermediate position between the extremes of ideal and bad, reinforcing the perception that no FPS in southern Brazil can be considered truly sustainable; evidence of clearly unsustainable FPS was also not found. Thus RAPFISH fell short of producing a clear pattern that could result in sound management, probably due to disagreement among the different dimensions of sustainability. All five fields of evaluation were equally weighted; however, it could be argued that the biological and ecological status of fisheries were not given enough emphasis in relation to the other dimensions. Dissimilarities within FPS and differences regarding sustainability levels must all be taken into consideration for sound management measures

Factors Associated with Cocaine Consumption among Suicide Victim

Cocaine use is an increasingly frequent event, especially in young people, and can cause irreversible consequences, such as suicide. To evaluate the factors associated with cocaine use in the moments preceding to suicide. This is a population-based, cross-sectional, and analytical study conducted in the Brazilian Federal District by researchers from the Department of Health and the Civil Police Institute of Criminalistics. All people who died due to suicide in 2018 were included in the survey. Cocaine use was considered the dependent variable, and robust Poisson regression was performed to estimate the crude and adjusted prevalence ratios and their respective population confidence intervals. In 2018, 12,157 deaths were recorded, of which suicide accounted for 1.56% of all deaths. It was observed that being between 25 and 44 years old, male, and under the influence of alcohol or cannabis, had a strong positive association with cocaine consumption among suicide victims. Males, people with black skin, with lower level of education, with employment, and who were under the effect of the use of cannabis and/or alcohol in the previous hours of death had a higher propensity to consume cocaine immediately before suicide, with a moderate to strong magnitude of prevalence ratio. The findings of this research indicated the need for monitoring, by health services, of people most vulnerable to suicide through the consumption of psychoactive substances