Concurrent Schedules Research Articles

Prospective control by reinforcers in human choice: Misallocation and bias, but not time orientation, influences reinforcer control

Research with nonhuman animals and children suggests reinforcer control is prospective; that is, behaviour is organised according to the likely future, as extrapolated from past experience. The present experiment extended this work to adult choice, and also explored the effects of individual differences in past, present, and future time-orientation on reinforcer control. Participants (N = 163) responded in a concurrent schedule in which the probability of a reinforcer at the same location as the previous reinforcer varied across conditions. Choice tracked these probabilities, albeit imperfectly, indicating that reinforcers controlled behaviour prospectively. Deviations in choice from reinforcer probabilities were well-captured by a quantitative model assuming that such deviations arise because reinforcers are misallocated to the wrong alternative and because of biases towards one alternative. This replicates previous findings in pigeons and children, hence demonstrating the cross-species generality, and developmental continuity, of prospective reinforcer control. Individual differences in time orientation appeared not to influence reinforcer control, although further work is needed to explore the conditions under which time orientation modulates prospective reinforcer control.

Enhancing timeliness of port placement for new treatment patients: A quality improvement initiative.

335 Background: Timely port placement is crucial for patients beginning new treatments, yet delays can impede care and satisfaction. This initiative aimed to address these delays and improve port placement efficiency for new treatment patients. Methods: A single-center prospective cohort study was conducted between July 2022 and December 2023. Data was collected to assess the time from port order to port placement. Interventions included concurrent scheduling of consult and port placement visits in coordination with interventional radiology (IR) and workflow redesign to enhance oncology navigator involvement by directing port orders to an oncology navigation pool for expedited processing and scheduling. The primary endpoint was to compare the mean difference in days between IR consult order and port placement among pre- and post-intervention groups. Results: The study included 144 patients: 102 in the pre-intervention group (July 2022-June 2023) and 42 in the post-intervention group (July 2023-December 2023). The post-intervention group showed a 26.35% improvement in time to port placement from appointment, compared to pre-intervention intervals. The combined quarterly mean indicated a 14.37% reduction in time to port placement from order. The mean interval between IR consult order and port placement was 15.59 days pre-intervention and 13.35 days post-intervention, with a mean difference of 2.24 days (CI -0.92 to 5.4; p = 0.08). Conclusions: This quality improvement initiative demonstrated substantial progress in reducing delays in port placement for new treatment patients. Optimizing workflow processes and increasing navigator involvement significantly improved timeliness and the overall patient experience. Continued monitoring and refinement of these interventions are essential for sustaining these improvements over time. Mean interval between IR consult order and port placement. Timeframe of Pre-intervention Group Mean of Pre-Intervention Group* Mean of Post-Intervention Group* (July 2023-Dec 2023) Mean Difference Between Pre and Post Intervention Group* Standard Error Confidence Interval p-value July 2022-Dec 2022 16.12 13.35 2.76 1.91 -1.04 to 6.57 0.07 Jan 2023-Jun 2023 14.93 13.35 1.58 1.59 -1.59 to 4.74 0.16 July 2022-Jun 2023 (overall) 15.59 13.35 2.24 1.60 -0.92 to 5.40 0.08 *Mean expressed in days.

SIGEPS: A System for Managing the Health Internship Program.

The healthcare sector's demand for a skilled workforce necessitates effective management of internship and residency programs. This study introduces the System for Managing the Health Internship Program (SIGEPS), aimed at addressing internship and residency management challenges in Joinville's municipal health network. The method of this study focused on developing a computational solution with applied and exploratory objectives. The research adopted a User-Centered Development approach, involving seven stages from scope determination to system implementation. Key stages included selecting Google's free technological tools, developing forms for information input, integrating these into a Google Sheets spreadsheet, and creating a website for schedule display. The primary result was the successful development of SIGEPS, which automated the process from initial requests to scheduling and analysis of healthcare institutions and displayed schedules online. The system offers several advantages over previous models, such as concurrent scheduling by multiple employees, process automation, enhanced information transparency, and improved efficiency with significant time savings. Future enhancements include integrating decision support systems and enabling data analysis reports through dashboards to further reduce scheduling efforts and enhance professional efficiency. This study demonstrates the feasibility of developing and implementing a free computational solution using the Google platform for managing internships and residencies in the healthcare sector.

Effects of pharmacological and environmental manipulations on choice between fentanyl and shock avoidance/escape in male and female rats under mutually exclusive and non-exclusive choice conditions.

Substance use disorders are defined by persistent drug consumption despite adverse consequences. Accordingly, we developed two fentanyl-vs-shock avoidance/escape choice procedures in which male and female rats responded under a fixed-ratio (FR)1:FR1 concurrent schedule of shock avoidance/escape and IV fentanyl under either mutually exclusive or non-exclusive choice conditions. Initial experiments using a discrete-trial procedure determined behavioral allocation between mutually exclusive shock avoidance/escape and different fentanyl doses (0.32-18 μg/kg/infusion; Experiment 1). Shock intensity (0.1-0.7 mA) and shock avoidance/escape response requirement (FR1-16) were also manipulated (Experiment 2). Next, we used a free-operant procedure in which shock avoidance/escape and fentanyl were continuously available under non-exclusive conditions, and response-shock (R-S) interval (30-1000 s) was manipulated (Experiment 3). Finally, we tested the hypothesis that extended-access fentanyl self-administration would produce fentanyl dependence, establish fentanyl withdrawal as an endogenous negative reinforcer, and increase fentanyl choice in both procedures (Experiments 4 and 5). The shock avoidance/escape contingency decreased fentanyl self-administration, and rats consistently chose shock avoidance/escape over fentanyl in both choice conditions. Decreasing shock intensity or increasing shock avoidance/escape response requirement failed to increase fentanyl choice, suggesting that fentanyl and shock avoidance/escape are independent economic commodities. Increasing the R-S interval increased fentanyl choice but failed to increase shock delivery. Extended fentanyl access engendered high fentanyl intake and opioid withdrawal signs but failed to increase fentanyl choice under either choice condition. These results suggest that neither positive fentanyl reinforcement nor negative reinforcement by fentanyl withdrawal is sufficient to reduce shock avoidance/escape-maintained responding and increase foot shock as an adverse consequence.

Managing coopetition dynamics: A longitudinal study of a multiparty alliance formation in a large utilities project

AbstractMultiparty alliances (MPAs) are increasingly used to deliver large utilities infrastructure projects on‐time, on‐budget, and to specified quality. In theory, MPAs should help buyers to coordinate suppliers, enable concurrent scheduling, and create process innovations. On the other hand, these governance structures are inherently less stable than dyadic relationships due to their additional complexity and greater opportunities for free riding. We conduct a multi‐source, longitudinal study, investigating how a buyer actively manages the dynamics between competition and cooperation during the formation of an MPA consisting of a lead organization and directional relationships between all partners. We contribute to MPA and coopetition literature by exploring cooperation and competition dynamics that are associated with the MPA structure that would largely be absent in dyads, and unpack the process by which a buyer orchestrates these dynamics by sequentially introducing new initiatives that seek to balance coopetition. MPAs have been recommended by governments and industry bodies as one solution for time and cost overruns in the utilities infrastructure sector, our study also provides guidance to buyers on the management of the alliance during the critical formation stage of the relationship lifecycle.

Resurgence and Behavioral Contrast, Compared and Contrasted.

This is a review of the relation between operant response resurgence and behavioral contrast. Both are defined by rate changes in a target response as a function of environmental changes spatially or temporally distal to the location of the target response. The typical procedures for investigating these two phenomena differ in that (1) resurgence is studied using concurrent schedules and behavioral contrast predominantly with multiple schedules and (2) resurgence is assessed against an extinction baseline of the target response and behavioral contrast has been assessed under a variety of reinforcement schedules. The distinctions between concurrent and multiple schedules, however, may be ones of degree rather than kind. Research into both phenomena reveals considerable overlap in the controlling variables of the two. With certain caveats, resurgence appears to be an instance of behavioral contrast measured against an extinction baseline. Because of Point 2 above, most instances of behavioral contrast do not meet the definition of resurgence. Investigating resurgence while maintaining target responding by a schedule of reinforcement might be useful, but such a procedure would not qualify as resurgence because it violates the definition of resurgence as the return of a previously reinforced but currently extinguished response. Several implications of the similarities and differences between the two are discussed.

Light Weight Concurrent Scheduling of Mobile Sink routing protocol towards Minimization of Propagation Delay against Spatial and Temporal Uncertainties of Cluster based Wireless Sensor Network

Wireless Sensor Network highly exposed to certain security attacks due to various uncertainties of the network which lead to node compromise. Hence considerable attention has been made by researcher during scheduling of the mobile sink to data collection of sensed information from the sensor nodes. Many secure data aggregation mechanism has been proposed to withstand the network against these kind of attack. Despite of many advantageous, those architectures will lead to several limitations such as large propagation delay and high energy consumption and spatial and temporal uncertainties. In order to mitigate those challenges, Light Weight Concurrent Scheduling of Mobile Sink routing protocol towards Minimization of Propagation Delay against Spatial and Temporal Uncertainties of Wireless Sensor Network is designed. It should be capable achieving energy efficiency and collision avoidance due to uncertainty in transmission and reception. Proposed model eliminates the packet collision and poor channel utilization challenges. Initially, node is partitioned and cluster head is selected based on the highest energy density of the node in the particular location. Employing Full duplex channel easily examines the spatial and temporal characteristic of the node through utilization cache information of routing table. It further helps to build the light weight scheme with behavioral strategies of the nodes for secure propagation of the sensed data to the mobile sink. Light weight scheme deployed in mobile sinks estimate the node trustworthiness and simultaneously collects the secure aggregated data packets of the sensor node through cluster head against dynamic time slots concurrently .Comparing with traditional secure routing architecture, simulation results demonstrates that proposed architecture can reduce the propagation delay against various uncertainties and maximizes the life time of the network on increasing the networking performances with respect to packet delivery ratio, throughput and propagation delay. Finally proposed model obtains the cooperative communication of sensor node information to the base station through mobile sink on heterogeneous wireless sensor network environment. DOI: https://doi.org/10.52783/pst.387

The generalization-across-dimensions model applied to conditional temporal discrimination.

Can simple choice conditional-discrimination choice be accounted for by recent quantitative models of combined stimulus and reinforcer control? In Experiment 1, two sets of five blackout durations, one using shorter intervals and one using longer intervals, conditionally signaled which subsequent choice response might provide food. In seven conditions, the distribution of blackout durations across the sets was varied. An updated version of the generalization-across-dimensions model nicely described the way that choice changed across durations. In Experiment 2, just two blackout durations acted as the conditional stimuli and the durations were varied over 10 conditions. The parameters of the model obtained in Experiment 1 failed adequately to predict choice in Experiment 2, but the model again fitted the data nicely. The failure to predict the Experiment 2 data from the Experiment 1 parameters occurred because in Experiment 1 differential control by reinforcer locations progressively decreased with blackout durations, whereas in Experiment 2 this control remained constant. These experiments extend the ability of the model to describe data from procedures based on concurrent schedules in which reinforcer ratios reverse at fixed times to those from conditional-discrimination procedures. Further research is needed to understand why control by reinforcer location differed between the two experiments.

A Sequential Sampling Approach to the Integration of Habits and Goals

Habits often conflict with goal-directed behaviors and this phenomenon continues to attract interests from neuroscientists, experimental psychologists, and applied health psychologists. Recent computational models explain habit-goal conflicts as the competitions between two learning systems, arbitrated by a central unit. Based on recent research that combined reinforcement learning and sequential sampling, we show that habit-goal conflicts can be more parsimoniously explained by a dynamic integration of habit and goal values in a sequential sampling model, without any arbitration. A computational model was developed by extending the multialternative decision field theory with the assumptions that habits bias starting points of preference accumulation, and that goal importance and goal relevance determine sampling probabilities of goal-related attributes. Simulation studies demonstrated our approach’s ability to qualitatively reproduce important empirical findings from three paradigms – classic devaluation, devaluation with a concurrent schedule, and reversal learning, and to predict gradual changes in decision times. In addition, a parameter recovery exercise using approximate Bayesian computation showcased the possibility of fitting the model to empirical data in future research. Implications of our work for habit theories and applications are discussed.

A rapid procedure to assess shifts in discriminative control over drinking during recovery-like behavior

BackgroundPreviously, we reported that recovery-like behavior decreases stimulus control over drinking, and this likely plays a role in the clinical observation that longer recovery increases relapse resistance. Those studies were conducted using a procedure that required repeated assessment, preventing a longitudinal analysis of the changes in stimulus control over time in each individual. Here we recapitulate those results and extend them to female rats using a more efficient procedure that allows repeated assessment of changes in stimulus control over drinking during recovery. MethodsUnder a multiple concurrent schedule, rats were trained to reliably respond predominantly for ethanol (concurrent Ethanol FR5, Food FR150) in the presence of one stimulus and for food (concurrent Ethanol FR5, Food FR5) in the presence of another stimulus. Stimuli were either lights or tones, depending on the group. After that, a drinking phase in which only the stimulus occasioning ethanol responding was presented (10 or 20 sessions) followed by recovery-like sessions in which only the stimulus occasioning food responding was presented. During these sessions, rats were exposed to the ethanol stimulus under extinction during the first component on sessions 0, 1, 2, 4, 8, and 16. The number of food responses during these stimulus exposures prior to the first five ethanol responses was the primary measure. ResultsConsistent with the earlier procedure, the number of food responses during ethanol tests increased as a function of the number of recovery sessions completed, regardless of whether the stimuli were visual or auditory. However, there were no significant effects of extended alcohol exposure or sex. ConclusionsA rapid procedure consistent with the earlier procedure and clinical evidence was developed in which stimulus control over drinking decreased following longer periods of recovery. Under conditions tested, stimulus type, length of drinking history, and sex did not affect this relationship.

Evaluating functional communication training without extinction in public school settings

AbstractFunctional communication training (FCT) in the treatment of escape‐maintained problem behavior for children with disabilities often includes extinction for problem behavior, which is difficult for educators to implement in classroom settings. This study evaluated the effects of FCT with concurrent schedules, as an alternative to extinction, for two children with disabilities and multiply maintained problem behavior including escape functions. FCT with concurrent schedules reduced problem behavior for one participant and increased mands for both participants. The mixed effects across participants and behaviors may inform boundary conditions for FCT with concurrent schedules.

Acquisition of cocaine reinforcement using fixed-ratio and concurrent choice schedules in socially housed female and male monkeys.

Previous studies in socially housed monkeys examining acquisition of cocaine self-administration under fixed-ratio (FR) schedules of reinforcement found that subordinate males and dominant females were more vulnerable than their counterparts. The present studies extended these findings in two ways: (1) to replicate the earlier study, in which female monkeys were studied after a relatively short period of social housing (~ 3months) using cocaine-naïve female monkeys (n = 9; 4 dominant and 5 subordinate) living in well-established social groups (~ 18months); and (2) in male monkeys (n = 3/social rank), we studied cocaine acquisition under a concurrent schedule, with an alternative, non-drug reinforcer available. In contrast to earlier findings, subordinate female monkeys acquired cocaine reinforcement (i.e., > saline reinforcement) at significantly lower cocaine doses compared with dominant monkeys. In the socially housed males, no dominant monkey acquired a cocaine preference (i.e., > 80% cocaine choice) over food, while two of three subordinate monkeys acquired cocaine reinforcement. In monkeys that did not acquire, the conditions were changed to an FR schedule with only cocaine available and after acquisition, returned to the concurrent schedule. In all monkeys, high doses of cocaine were chosen over food reinforcement. The behavioral data in females suggests that duration of social enrichment and stress can differentially impact vulnerability to cocaine reinforcement. The findings in socially housed male monkeys, using concurrent food vs. cocaine choice schedules of reinforcement, confirmed earlier social-rank differences using an FR schedule and showed that vulnerability could be modified by exposure to cocaine.

Contingent administration of typical and biased kappa opioid agonists reduces cocaine and oxycodone choice in a drug vs. food choice procedure in male rhesus monkeys.

Combinations of mu and kappa-opioid receptor (KOR) agonists have been proposed as analgesic formulations with reduced abuse potential. The feasibility of this approach has been increased by the development of KOR agonists with biased signaling profiles that produce KOR-typical antinociception with fewer KOR-typical side effects. The present study determined if the biased KOR agonists, nalfurafine and triazole 1.1, could reduce choice for oxycodone in rhesus monkeys as effectively as the typical KOR agonist, salvinorin A. Adult male rhesus monkeys (N = 5) responded under a concurrent schedule of food delivery and intravenous cocaine injections (0.018mg/kg/injection). Once trained, cocaine (0.018mg/kg/injection) or oxycodone (0.0056mg/kg/injection) was tested alone or in combination with contingent injections of salvinorin A (0.1-3.2µg/kg/injection), nalfurafine (0.0032-0.1µg/kg/injection), triazole 1.1 (3.2-100.0µg/kg/injection), or vehicle. In each condition, the cocaine or oxycodone dose, as well as the food amount, was held constant across choice components, while the dose of the KOR agonist was increased across choice components. Cocaine and oxycodone were chosen over food on more than 80% of trials when administered alone or contingently with vehicle. When KOR agonists were administered contingently with either cocaine or oxycodone, drug choice decreased in a dose-dependent manner. Salvinorin A and triazole 1.1 decreased drug-reinforcer choice without altering total trials completed (i.e., choice allocation shifted to food), while nalfurafine dose dependently decreased total trials completed. These results demonstrate that salvinorin A and triazole 1.1, but not nalfurafine, selectively reduce cocaine and oxycodone self-administration independent of nonspecific effects on behavior, suggesting that G-protein bias does not appear to be a moderating factor in this outcome. Triazole 1.1 represents an important prototypical compound for developing novel KOR agonists as deterrents for prescription opioid abuse.

Optimum Scheduling of a Multi-Machine Flexible Manufacturing System Considering Job and Tool Transfer Times without Tool Delay

In order to minimize makespan (Cmax) without causing tool delay with the fewest copies of each tool type, this study investigates the concurrent scheduling of automated guided vehicles (AGVs), machines (MCs), tool transporter (TT), and tools in a multi-machine flexible manufacturing system (FMS). The tools are housed in a central tool magazine (CTM), accessible to and utilized by several machines. AGVs and the tool transporter (TT) move jobs and tools between machines. Since it involves allocating tool copies and AGVs to job operations, sequencing job operations on machines, and related trip operations, such as AGVs’ and TT’s empty trip and loaded trip times, this simultaneous scheduling problem is highly complicated. This issue is resolved using the symbiotic organisms search algorithm (SOSA), based on the symbiotic interaction strategies that organisms adapt to survive in the ecosystem. This study proposes a mixed nonlinear integer programming formulation to address this problem. Verification is performed using an industrial problem from a manufacturing organization. The results show that employing two copies for two tool types out of 22 tool kinds and one copy for the remaining tool types results in no tool delay, which causes a reduction in the Cmax as well as cost. The industries that can benefit directly from this study are consumer electronics manufacturers, original equipment manufacturers, automobile manufacturers, and textile machine producers. The results demonstrate that the SOSA provides promising results compared to the flower pollination algorithm (FPA).

Concurrent Scheduling of Machines and Tools without Tool Delay in a Multi Machine FMS using Flower Pollination Algorithm

Concurrent Scheduling of Machines and Tools without Tool Delay in a Multi Machine FMS using Flower Pollination Algorithm

Substitutability of nicotine and sucrose in rats: A behavioral economic analysis

Despite considerable evidence suggesting that sweet foods are a substitute for nicotine in humans, no formal behavioral economic analysis of this interrelationship has been conducted in nonhumans. The purpose of the present study was to examine this phenomenon in rats using concurrent schedules of sucrose pellet, chow pellet, and nicotine reinforcer delivery. Rats responded on separate levers that delivered sucrose pellets, chow pellets, or nicotine infusions under concurrent fixed-ratio (FR) 1 schedules for each commodity within a closed economy. Following stable food and nicotine intake, the unit price of either sucrose or nicotine (the primary commodity) was increased while the two alternative commodities remained unchanged. Substitution was quantified using a behavioral economic cross-price model, as well as a novel commodity relation index that normalizes consumption of dissimilar commodities. Asymmetrical partial substitution was observed, wherein sucrose served as a partial substitute for nicotine, but nicotine failed to substitute for sucrose. Moreover, sucrose was a stronger partial substitute for nicotine than chow in most rats. These findings indicate that substitution of food for nicotine depends on the type of food. These findings mirror the selective increase in carbohydrate intake that can occur during smoking cessation and demonstrate a behavioral economic mechanism that may mediate it.

A comparison of the reinforcing strength of cocaethylene and cocaine in monkeys responding under progressive-ratio and concurrent choice schedules of reinforcement

BackgroundIndividuals who use cocaine have high rates of co-morbid alcohol use and when ethanol and cocaine are administered concurrently, the metabolite cocaethylene is formed. Cocaethylene is equipotent to cocaine in blocking dopamine reuptake and substitutes for cocaine in drug discrimination studies. However, no previous work has directly compared the reinforcing strength of cocaine to cocaethylene. MethodsIn Experiment 1, three individually-housed adult male rhesus macaques self-administer cocaine under a progressive-ratio (PR) schedule of reinforcement, during daily 4-hr sessions. Under this schedule, the primary dependent variable is the number of injections received, or the break point (BP). Saline, cocaine (0.001–0.3mg/kg/injection) and cocaethylene (0.0003–0.1mg/kg/injection) dose-response curves were determined. In Experiment 2, two female cynomolgus and one rhesus macaque responded under a concurrent schedule of drug (cocaine or cocaethylene) vs. 1.0-g banana-flavored food pellets, during daily 1-hr sessions. ResultsBoth cocaine and cocaethylene functioned as reinforcers under the PR and concurrent choice schedules of reinforcement. Under the PR schedule, peak BPs were not significantly different, nor were ED50 values on the ascending limb, suggesting that cocaethylene has equal reinforcing strength and potency to cocaine. Under the concurrent drug-food choice procedure, cocaethylene was also equally potent to cocaine. ConclusionsUnder two schedules of reinforcement designed to assess reinforcing strength, cocaethylene and cocaine were equipotent and of equal reinforcing strength. Because cocaethylene has a longer duration of action, it is important for studies designed to evaluate treatments for cocaine use to also consider the effects of these interventions on cocaethylene.

Ethanol-paired conditioned stimulus effects on concurrent reinforced responding for ethanol and food.

The influence of Pavlovian Conditioned Stimuli (CS) on ethanol self-administration and choice between ethanol and an alternative are potentially important. Ethanol-paired CS might increase ethanol self-administration, especially when it has been reduced during recovery, though the selectivity of these increases has been questioned. To date, one study examined the effects of an ethanol-paired CS on ethanol choice and found that the CS increased ethanol-responding more than food-responding when both were in extinction. However, it remains unclear whether ethanol-paired CS increase ethanol-choice that is not in extinction. Here, we examine the effects of an ethanol-paired CS on ethanol-choice when both food- and ethanol-responding are reinforced. Sixteen adult male Lewis rats were trained on a concurrent schedule to respond for ethanol on one lever and for food on the other lever. Ethanol was available under an FR 5 schedule, and food was available under an FR schedule that was adjusted for each rat to earn an equal number of food and ethanol deliveries. Then, 2-min light presentations were paired with an RT 25-sec schedule of ethanol delivery for 10 sessions in the absence of both levers. After this, subjects were placed back on the concurrent schedule for one session, then five sessions with the CS being present or absent on each trial of the concurrent schedule occurred. Rats learned to respond on one lever for ethanol and on the other for food and earned similar numbers of ethanol and food deliveries. During Pavlovian Conditioning, the number of head entries into the head-entry detector was higher in the presence of the CS than in its absence. In the test sessions, rats made more ethanol responses in the presence of the CS than in its absence. However, this effect was small and did not increase the amount of ethanol earned. Thus, ethanol-paired CS could increase ethanol-responding under a choice procedure but did not increase ethanol consumption meaningfully under the studied conditions.

Efficient linearizability checking for actor‐based systems

AbstractRecent demand for distributed software had led to a surge in popularity in actor‐based frameworks. However, even with the stylized message passing model of actors, writing correct distributed software is still difficult. We present our work on linearizability checking in DS2, an integrated framework for specifying, synthesizing, and testing distributed actor systems. The key insight of our approach is that often subcomponents of distributed actor systems represent common algorithms or data structures (e.g., a distributed hash table or tree) that can be validated against a simple sequential model of the system. This makes it easy for developers to validate their concurrent actor systems without complex specifications. DS2 automatically explores the concurrent schedules that system could arrive at, and it compares observed output of the system to ensure it is equivalent to what the sequential implementation could have produced. We describe DS2's linearizability checking and test it on several concurrent replication algorithms from the literature. We explore in detail how different algorithms for enumerating the model schedule space fare in finding bugs in actor systems, and we present our own refinements on algorithms for exploring actor system schedules that we show are effective in finding bugs.

Joint Optimization of Relay Selection and Transmission Scheduling for UAV-Aided mmWave Vehicular Networks

To deal with the explosive growth of mobile traffic, millimeter-wave (mmWave) communications with abundant bandwidth resources have been applied to vehicular networks. As mmWave signal is sensitive to blockage, we introduce the unmanned aerial vehicle (UAV)-aided two-way relaying system for vehicular connection enhancement and coverage expansion. How to improve transmission efficiency and to reduce latency time in such a dynamic scenario is a challenging problem. In this paper, we formulate the joint optimization problem of relay selection and transmission scheduling, aiming to reduce transmission time while meeting the throughput requirements. To solve this problem, two schemes are proposed. The first one is the random relay selection with concurrent scheduling (RCS), a low-complexity algorithm implemented in two steps. The second one is the joint relay selection with dynamic scheduling (JRDS), which fully avoids relay contentions and exploits potential concurrent ability, to obtain further performance enhancement over RCS. Through extensive simulations under different environments with various flow numbers and vehicle speeds, we demonstrate that both RCS and JRDS schemes outperform the existing schemes significantly in terms of transmission time and network throughput. We also analyze the impact of threshold selection on achievable performance.