Delay Probability Research Articles

Cross-Layer Optimization for Ultra-Reliable and Low-Latency Radio Access Networks

In this paper, we propose a framework for cross-layer optimization to ensure ultra-high reliability and ultra-low latency in radio access networks, where both transmission delay and queueing delay are considered. With short transmission time, the blocklength of channel codes is finite, and the Shannon capacity cannot be used to characterize the maximal achievable rate with given transmission error probability. With randomly arrived packets, some packets may violate the queueing delay. Moreover, since the queueing delay is shorter than the channel coherence time in typical scenarios, the required transmit power to guarantee the queueing delay and transmission error probability will become unbounded even with spatial diversity. To ensure the required quality-of-service (QoS) with finite transmit power, a proactive packet dropping mechanism is introduced. Then, the overall packet loss probability includes transmission error probability , queueing delay violation probability , and packet dropping probability . We optimize the packet dropping policy, power allocation policy, and bandwidth allocation policy to minimize the transmit power under the QoS constraint. The optimal solution is obtained, which depends on both channel and queue state information. Simulation and numerical results validate our analysis, and show that setting the three packet loss probabilities as equal causes marginal power loss.

Low-Latency Millimeter-Wave Communications: Traffic Dispersion or Network Densification?

Low latency is critical for many applications in wireless communications, e.g., vehicle-to-vehicle, multimedia, and industrial control networks. Meanwhile, for the capability of providing multi-gigabits per second rates, millimeter-wave (mm-wave) communication has attracted substantial research interest recently. This paper investigates two strategies to reduce the communication delay in future wireless networks: traffic dispersion and network densification. A hybrid scheme that combines these two strategies is also considered. The probabilistic delay and effective capacity are used to evaluate performance. For probabilistic delay, the violation probability of delay, i.e., the probability that the delay exceeds a given tolerance level, is characterized in terms of upper bounds, which are derived by applying stochastic network calculus theory. In addition, to characterize the maximum affordable arrival traffic for mm-wave systems, the effective capacity, i.e., the service capability with a given quality-of-service requirement, is studied. The derived bounds on the probabilistic delay and effective capacity are validated through simulations. These numerical results show that, for a given sum power budget, traffic dispersion, network densification, and the hybrid scheme exhibit different potentials to reduce the end-to-end communication delay. For instance, traffic dispersion outperforms network densification when high sum power budget and arrival rate are given, while it could be the worst option, otherwise. Furthermore, it is revealed that, increasing the number of independent paths and/or relay density is always beneficial, while the performance gain is related to the arrival rate and sum power, jointly. Therefore, a proper transmission scheme should be selected to optimize the delay performance, according to the given conditions on arrival traffic and system service capability.

Indeterminate QuantiFERON-TB Gold Increases Likelihood of Inflammatory Bowel Disease Treatment Delay and Hospitalization.

QuantiFERON-TB Gold (QFTG) is a blood test used to diagnose latent tuberculosis infection (LTBI) prior to TNF-α inhibitor (anti-TNF) initiation. We sought to determine factors associated with indeterminate QFTG results in inflammatory bowel disease (IBD) patients and whether indeterminate results are associated with IBD-related morbidity. This nested case-control study included IBD patients who underwent QFTG testing. Cases were patients with indeterminate QFTG and controls were those with negative QFTG. The association of demographic and clinical data with indeterminate QFTG result was assessed using logistic regression. We examined the clinical impact of indeterminate QFTG results on risk of hospitalization and delay in anti-TNF initiation using inverse probability-of-treatment weighting (IPTW) regression. We identified 411 patients with QFTG testing (320 negative, 80 indeterminate, and 11 positive results). No patient with an indeterminate result subsequently had LTBI. Systemic corticosteroid use (OR, 4.4; 95% CI, 2.0-9.6) and hospitalization at the time of QFTG (OR, 3.8; 95% CI, 1.9-7.7) were associated with indeterminate QFTG, while immunomodulator use was nearly statistically significant (OR, 3.1; 95% CI, 0.9-9.8) and anti-TNF use was not (OR, 0.9; 95% CI, 0.2-4.6). After IPTW adjustment, indeterminate QFTG was associated with a 23.1% (95% CI, 8.2%-37.9%) greater probability of delay in anti-TNF initiation beyond 30 days and an 11.9% (95% CI, 0.6%-23.1%) greater probability of hospitalization within 60 days. Systemic corticosteroid use and hospitalization were associated with an indeterminate QFTG result. Indeterminate QFTG results were associated with delayed anti-TNF initiation and subsequent hospitalization.

Data-Enabled Stochastic Modeling for Evaluating Schedule Robustness of Railway Networks

This paper evaluates the robustness of a railway network with respect to operational delays. It assumes that trains in the network operate on fixed routes and with reference to a timetable. A stochastic delay propagation model is proposed for identifying primary (externally imposed) delays and for computing the resultant secondary (knock-on) delays. Delay probability distributions are computed for each train at each station on its journey, using timetable and infrastructure data for identifying potential station resource conflicts with other trains. The delay predictions are used to evaluate schedule robustness using two newly proposed metrics. Individual robustness measures the ability of trains to limit the adverse effects of their own primary delays. On the other hand, collective robustness measures the ability of the network as a whole, to limit the knock-on effects of primary delays imposed on a small fraction of trains. The two metrics provide stochastic guarantees on the punctuality of trains when the published schedule is put in operation. The applicability of the proposed methodology is validated using empirical data from a portion of the Indian Railways network, containing more than 38,000 train arrival/departure records. While a railway network is used as a case study, the same ideas can be applied to any scheduled transportation network.

Estimation Delay Variation and Probability of Occurrence of Different Level of Services Based on Random Variations of Vehicles Entering Signalized Intersections

Estimation of delay in signalized intersection is a difficult and complicated process that depends on many variables. Among the factors influencing the intersection delay, variable of saturation degree (Xc) is one of the most important variables. In the present study, a new analytical method has been proposed for calculating delay variation at isolated intersections in under-saturated condition and under the influence of different number of vehicles entering to the intersections. Generally, the average delay for average number of vehicles entering intersection is currently calculated by the point to point method; then, the level of service of intersection is specified from the resulting delay. In the meantime, the influence of different number of vehicles entering to the intersections cannot be seen in such methods. But for the presented method in this paper the delay is expressed as a range of values for different values of saturation degree and different numbers of vehicles entering the intersections that it leads to achieve more real results from intersection's level of service.

Determinantes para o cumprimento de prazo e preço em obras da educação: uma análise nos municípios capixabas

Resumo Objetiva-se com este estudo analisar os determinantes que contribuem para explicar o cumprimento dos prazos e preços em obras do setor de educação nos municípios capixabas. Tem como norteadora a revisão de literatura dos tópicos relativos à eficiência na alocação dos recursos públicos e estudos anteriores. Os determinantes foram classificados em cinco dimensões. Os resultados indicaram que, quanto ao cumprimento de prazo, são determinantes: as modalidades de licitação concorrência pública e convite, o tipo de serviço executado de reforma, o número de habitantes, o governante reeleito e o partido do prefeito igual ao do presidente. Quanto ao cumprimento de preço: a modalidade convite, o número de habitantes e o partido do prefeito igual ao do presidente. Este estudo contribui para a identificação de características que podem auxiliar no aumento da eficiência na alocação dos recursos públicos.

Reservation, a tool to reduce the balking effect and the probability of delay

We investigate a threshold reservation policy implemented within a single customer’s class. From an explicit performance analysis, we prove that the potential of reservation is into the reduction of the balking effect together with a higher server’s utilization. However, it also may result in a higher expected waiting time and more abandonment. We conclude that reservation can be efficiently implemented in large systems, under high workload situations, with a low waiting aversion and a low impatience.

Markov chain model for delay distribution in train schedules: Assessing the effectiveness of time allowances

Train movements are subject to disturbances and disruptions, which may cause late departures and/or late arrivals at particular locations (e.g., terminals, stations, crossings) with respect to their pre-determined times. To prevent possible deviations from the scheduled times, time allowances are added to the process times (i.e., running times) as time supplements and to the time interval between successive trains (i.e., minimum headway) as buffer times. The amount of time allowances is decided during the timetable planning process and their contribution to the service quality is monitored in actual operation. The adequacy of time allowances results in punctual train operations, which is one of the primary interests of service users and providers. Because the sequence of train departure and arrival times can be viewed as a stochastic process, the performance of train operations may be analyzed and modeled using Markov chains. We modeled train departure and arrival delays at stations as states and analyzed the successive state changes along train paths in a single track railway. This allowed us to predict train states at certain event time steps and to estimate steady-state delay probabilities. The former may be used to reschedule train movements and the latter to measure timetable robustness.

A trust framework based smart aggregation for machine type communication

Machine type communication (MTC) is one of the significant communication paradigms in the fifth generation networks. The existing cellular networks are not designed for massive access of the MTC devices. Therefore, data aggregation and relaying are advocated to reduce the massive MTC access besides other physical layer solutions. In this paper, we propose a secured multiple mobile relay selection algorithm that smartly aggregates data from adjacent MTC devices through multiple user equipments and transmits it to the base station (BS). The paper also presents a framework for the selection of trusted relays to cooperatively aggregate MTC data and render two-hop connectivity to the BS. Our proposed algorithm is compared with existing algorithms on the basis of energy efficiency, system capacity, communication delay and outage probability. Our proposed algorithm outperforms the other schemes by improving outage probability and communication delay by 33% and 25%, respectively.

Fault detection filter design for continuous-time nonlinear Markovian jump systems with mode-dependent delay and time-varying transition probabilities

This paper focuses on fault detection filter (FDF) design for continuous-time nonlinear Markovian jump systems (NMJSs) with mode-dependent delay and time-varying transition probabilities (TPs). By using a novel Lyapunov-Krasovskii function and based on convex polyhedron technique, a new FDF, as the residual generator, is constructed to guarantee the mean-square exponential stability and a prescribed level of disturbance attenuation for admissible perturbations of NMJSs. Finally, the numerical simulation is carried out to demonstrate the effectiveness of our method.

Delay Discounting and Probability Discounting, But Not Response Inhibition, Are Associated With Sexual Risk Taking in Adults

Sexual risk behavior (SRB) is associated with impulsivity, but it is not clear whether different aspects of impulsivity are uniquely related to SRBs in adults. Unmarried adults ages 18 to 30 (N = 296; 41.0% male) recruited from the community reported their frequency of SRBs over the past six months using the Sexual Risk Survey (SRS; Turchik & Garske, 2009) and completed three behavioral measures of impulsivity: insensitivity to delayed consequences (delay discounting [DD]), insensitivity to probabilistic consequences (probability discounting [PD]) and response inhibition (stop signal task [SST]). SRS total scores were significantly related to both DD and PD but not SST. These findings suggest that insensitivity to delayed and probabilistic consequences, but not response inhibition, are meaningfully associated with SRBs in young adults. This may be important for the development of strategies to prevent or reduce sexual risk behaviors.

Fuzzy Logic-based Intelligent Scheme for Enhancing QoS of Vertical Handover Decision in Vehicular Ad-hoc Networks

The design of next generation networks in various technologies under the “Anywhere, Anytime” paradigm offers seamless connectivity across different coverage. A conventional algorithm such as RSSThreshold algorithm, that only uses the received strength signal (RSS) as a metric, will decrease handover performance regarding handover latency, delay, packet loss, and handover failure probability. Moreover, the RSS-based algorithm is only suitable for horizontal handover decision to examine the quality of service (QoS) compared to the vertical handover decision in advanced technologies. In the next generation network, vertical handover can be started based on the user’s convenience or choice rather than connectivity reasons. This study proposes a vertical handover decision algorithm that uses a Fuzzy Logic (FL) algorithm, to increase QoS performance in heterogeneous vehicular ad-hoc networks (VANET). The study uses network simulator 2.29 (NS 2.29) along with the mobility traffic network and generator to implement simulation scenarios and topologies. This helps the simulation to achieve a realistic VANET mobility scenario. The required analysis on the performance of QoS in the vertical handover can thus be conducted. The proposed Fuzzy Logic algorithm shows improvement over the conventional algorithm (RSSThreshold) in the average percentage of handover QoS whereby it achieves 20%, 21% and 13% improvement on handover latency, delay, and packet loss respectively. This is achieved through triggering a process in layer two and three that enhances the handover performance.

An improved gas kick detection method based on continuous Doppler ultrasonic wave in deep water drilling

Gas kick detection is an essential part of safe well control process in deep water drilling. The conventional gas kick detection methods are based on the drilling mud flow velocity measured near the well mouth which often results in a high probability of delay. For deep water drilling, the gas kick detection method based on non-intrusive detection at mud line is one of the most commonly used methods with low cost and strong timeliness. In this article, the reflection model of continuous Doppler ultrasonic wave in multiphase fluid was analyzed and an improved gas kick detection method at mud line was proposed. The proposed method gives a comprehensive judgment on gas kick state based on continuous Doppler shift frequency (multiphase flow velocity), amplitude, and spectral shape. Experimental results on water and 1.1 g/cm3 oil-based drilling mud demonstrated that the proposed method can detect early gas kick with over 3% void fraction effectively and measure multiphase flow velocity accurately under the steady flow state, showing a relative error smaller than 10%.

An intelligent resource management scheme for SDF-based cooperative spectrum sensing in the presence of primary user emulation attack

This paper focuses on designing an energy-efficient cognitive radio network (CRN) in the presence of a primary user emulation attacker. The approach requires suitable resource management schemes that help in maximizing energy efficiency (EE) of the secondary network while providing sufficient protection to the primary network. Hence, we propose a secondary users (SUs) selection algorithm for maximizing system throughput while ensuring spectrum sensing accuracy. Then the sensing time is evaluated for obtaining maximum throughput, minimum delay and minimum false alarm probability. Further, the non-linear EE maximization problem associated with the non-convex constraints is solved by our proposed novel iterative resource allocation (NIRA) algorithm to jointly optimize both sensing time and transmission power of the secondary network within which the fractional EE is transferred to convex programming by employing the Dinkelbach method in the outer layer and the constraints are addressed by dual decomposition and Difference of convex (DC) programming method. Simulation results validate the effectiveness of our proposed approaches, and the impact of different system parameters is also studied.

Association between the high soluble fms-like tyrosine kinase-1 to placental growth factor ratio and adverse outcomes in asymptomatic women with early-onset fetal growth restriction

ABSTRACTObjective: To assess whether the high soluble fms-like tyrosine kinase-1 (sFlt-1) to placental growth factor (PlGF) ratio is associated with adverse outcomes (e.g., HELLP syndrome [hemolysis, elevated liver enzymes, and low platelets], severe hypertension uncontrolled by medication, non-reassuring fetal status, placental abruption, pulmonary edema, growth arrest, maternal death, or fetal death) and a shorter duration to delivery in early-onset fetal growth restriction (FGR).Methods: Thirty-four women with FGR diagnosed at <34.0 weeks were recruited. Serum angiogenic marker levels were estimated within 6 hours of a diagnosis of FGR. A receiver operating characteristic curve was used to determine the threshold of the sFlt-1/PlGF ratio to predict adverse outcomes. We used multivariable logistic regression analysis to examine the association between the sFlt-1/PlGF ratio and adverse outcomes. Finally, we used Kaplan-Meier analysis and the log-rank test to assess the probability of delay in delivery.Results: Women who developed adverse outcomes within a week had a significantly higher sFlt-1/PlGF ratio than did those who did not develop complications. A cutoff value of 86.2 for the sFlt-1/PlGF ratio predicted adverse outcomes, with a sensitivity and specificity of 77.8% and 80.0%, respectively. Moreover, 58.4% of women with an sFlt-1/PlGF ratio ≥86.2 versus 9.1% of those with an sFlt-1/PlGF ratio <86.2 delivered within a week of presentation (p < 0.001). In multivariate analyses, an sFlt-1/PlGF ratio ≥86.2 (adjusted odds ratio 9.52; 95% confidence interval, 1.25–72.8) was associated with adverse maternal and neonatal outcomes.Conclusion: A high sFlt-1/PlGF ratio was associated with adverse outcomes and a shorter duration to delivery in early-onset FGR.

Efficient Random-Access Scheme for Massive Connectivity in 3GPP Low-Cost Machine-Type Communications

In order to facilitate low-cost network connection of many devices, machine-type communication (MTC) has evolved to low-cost MTC (LC-MTC) in the third-generation partnership project standard. LC-MTC should be able to effectively handle intensive accesses through multiple narrowband random-access channels (RACHs) assigned within the bandwidth of a long-term evolution system. As the number of MTC devices and their congestion rapidly increase, the random-access scheme for the LC-MTC RACH needs to be improved. This paper presents a novel random-access scheme that introduces virtual preambles of LC-MTC devices and associates them with RACH indexes to effectively discern LC-MTC devices. In comparison with the sole use of preambles, our scheme allows an LC-MTC device to better choose a unique virtual preamble. Thereby, the probability of successful accesses of LC-MTC devices increases in contention-based random-access environments. We experimentally assessed our scheme, and the results show that our scheme performs better than the existing preamble-based scheme in terms of collision probability, access delay, and access blocking probability.

Impact of Partial Time Delay on Temporal Dynamics of Watts–Strogatz Small-World Neuronal Networks

In this paper, we mainly discuss effects of partial time delay on temporal dynamics of Watts–Strogatz (WS) small-world neuronal networks by controlling two parameters. One is the time delay [Formula: see text] and the other is the probability of partial time delay [Formula: see text]. Temporal dynamics of WS small-world neuronal networks are discussed with the aid of temporal coherence and mean firing rate. With the obtained simulation results, it is revealed that for small time delay [Formula: see text], the probability [Formula: see text] could weaken temporal coherence and increase mean firing rate of neuronal networks, which indicates that it could improve neuronal firings of the neuronal networks while destroying firing regularity. For large time delay [Formula: see text], temporal coherence and mean firing rate do not have great changes with respect to [Formula: see text]. Time delay [Formula: see text] always has great influence on both temporal coherence and mean firing rate no matter what is the value of [Formula: see text]. Moreover, with the analysis of spike trains and histograms of interspike intervals of neurons inside neuronal networks, it is found that the effects of partial time delays on temporal coherence and mean firing rate could be the result of locking between the period of neuronal firing activities and the value of time delay [Formula: see text]. In brief, partial time delay could have great influence on temporal dynamics of the neuronal networks.

Robust State Feedback H∞ Control for Discrete-Time Fuzzy System With Random Delays

This paper investigates the problem of robust stabilization for a class of discrete-time Takagi–Sugeno (TS) fuzzy systems via input random delays in control input. The main objective of this paper is to design a state feedback H∞ controller. Linear matrix inequality (LMI) approach together with the construction of proper Lyapunov–Krasovskii functional is employed for obtaining delay dependent sufficient conditions for the existence of robust H∞ controller. In particular, the effect of both variation range and distribution probability of the time delay is taken into account in the control input. The key feature of the proposed results in this paper is that the time‐varying delay in the control input not only dependent on the bound but also the distribution probability of the time delay. The obtained results are formulated in terms of LMIs which can be easily solved by using the standard optimization algorithms. Finally, a numerical example with simulation result is provided to illustrate the effectiveness of the obtained control law and less conservativeness of the proposed result.

Distributed consensus of a class of networked nonlinear systems by non-uniform sampling with probabilistic transmission delays and its application to two-link manipulators

This paper investigates the primary problem of distributed consensus for Euler–Lagrange systems networked by using non-uniform sampling information with probabilistic transmission delay. In a real-world application, the information is likely to be exchanged in a discrete-time interval manner. Employing sampled-data information can save the energy cost and reduce the communication network burden. For the reasons given above, sampling control is applied in this paper. Meanwhile, we focus on the study of non-uniform sampling information exchanges in the communication network which is described in this paper. In order to verify the distributed consensus of Euler–Lagrange systems, matrix theory, algebraic graph theory and Lyapunov stability theory are applied. A distinctive feature of this paper is that the transmission delay is defined as the probability of time-varying delay. A numerical simulation is given to demonstrate the benefits and effectiveness of the proposed schemes.

Optimal Fusion Estimation with Multi-Step Random Delays and Losses in Transmission.

This paper is concerned with the optimal fusion estimation problem in networked stochastic systems with bounded random delays and packet dropouts, which unavoidably occur during the data transmission in the network. The measured outputs from each sensor are perturbed by random parameter matrices and white additive noises, which are cross-correlated between the different sensors. Least-squares fusion linear estimators including filter, predictor and fixed-point smoother, as well as the corresponding estimation error covariance matrices are designed via the innovation analysis approach. The proposed recursive algorithms depend on the delay probabilities at each sampling time, but do not to need to know if a particular measurement is delayed or not. Moreover, the knowledge of the signal evolution model is not required, as the algorithms need only the first and second order moments of the processes involved. Some of the practical situations covered by the proposed system model with random parameter matrices are analyzed and the influence of the delays in the estimation accuracy are examined in a numerical example.