The motivation comes from the sheer scale of modern monitoring systems. Billions of IoT devices now gather information about activities in working and living environments, from smart farms to hospitals, and most of these deployments lean on the Cloud for data analysis and artificial intelligence. But the Cloud was never designed for split-second responsiveness. Data traveling from a sensor to a distant data center and back accumulates latency at every hop, and for applications where long delays are simply not acceptable—patient monitoring, industrial safety, livestock health tracking—that round trip can render the entire system useless. The Fog computing concept emerged precisely to close this gap, extending the Cloud by executing application tasks close to the network edge, near where the data is born.

Fog computing, however, introduces its own dilemma. Edge nodes are deliberately modest machines, placed near sensors to keep response times short, and their finite processing capacity becomes a bottleneck as more devices join. Each additional sensor adds data traffic, and each added task competes for the same limited fog resources. The central question the Serbian researchers posed was deceptively simple: what is the acceptable load—the number of participants acting as end devices—that can be loaded onto the system without violating a required performance parameter such as an acceptable delay? Answering it requires a model detailed enough to capture real system behavior and an optimization method efficient enough to search the vast space of possible configurations.

The team’s approach rests on two pillars. The first is iFogSim, a widely used simulation toolkit for modeling and simulating resource management techniques in Internet of Things, Edge, and Fog computing environments. The researchers modeled the structure of their Cloud-Fog system in iFogSim, which then produces values of system performance as its output—most importantly, the application delays that result from executing applications near sensor devices. The second pillar is the Particle Swarm Optimization algorithm, a nature-inspired metaheuristic that searches for optimal solutions by mimicking the social behavior of bird flocks or fish schools. In PSO, a population of candidate solutions, called particles, moves through the search space, each adjusting its trajectory based on its own best position so far and the best position found by the swarm.

The marriage of these two tools is what makes the method workable. iFogSim alone can tell you the delay for a given configuration, but it cannot tell you which configuration to try next. Exhaustively testing every possible number of devices and placement of application modules would be computationally prohibitive, since the configuration space grows explosively with system size. By using the delay values returned by iFogSim as the fitness signal for the PSO algorithm, the researchers created a feedback loop: the optimizer proposes a candidate load, the simulator evaluates its consequences, and the optimizer refines its search accordingly. The result is an estimate of the optimal system load—the largest number of end devices the infrastructure can support while keeping latency within the boundary the application demands.

The significance of knowing this number extends well beyond latency itself. As the authors note, once operators obtain information about optimal system load values, broader system performance can be managed and ensured within acceptable boundaries. Application latency, power consumption, and network utilization are all coupled: an overloaded fog node burns more energy per task, saturates its network links, and pushes delays upward simultaneously. A capacity estimate derived from delay constraints therefore acts as a proxy guard for the entire performance envelope. Network designers can provision fog nodes with confidence, knowing how many sensors each can serve, and can plan expansions before congestion degrades service rather than after users notice it.

The study situates itself within a large and rapidly growing body of research on application placement and resource management in fog environments. Recent literature has explored deadline-based dynamic resource allocation, learning automata approaches to module placement, genetic algorithms for service placement, and machine learning-driven solutions for resource management. Surveys of the field document a proliferation of metaheuristic task scheduling methods for latency-sensitive IoT applications, including swarm-based techniques. What distinguishes the new work is its focus on capacity estimation rather than scheduling: instead of deciding where to place a fixed set of tasks, it determines how many devices the system can accept in the first place, treating the load itself as the decision variable to be optimized.

The practical domains that stand to benefit are those the authors and the wider literature repeatedly highlight. Fog-enabled healthcare systems, where patient vital signs must be analyzed with minimal delay, have been a driving application for fog research since its inception. Smart farming deployments, which motivated the authors’ own institutional context at the Faculty of Agronomy in Čačak, rely on dense sensor networks monitoring livestock and crops, where reliability provisioning in the IoT-Fog-Cloud continuum is an active concern. Real-time health monitoring for smart homes and hospitals, fog-enabled smart car parking, and augmented brain-computer interaction have all been demonstrated as fog applications in prior work, and each shares the same constraint: the value of the service collapses if the response arrives too late.

The methodology also reflects pragmatic engineering choices. Building the model in a Python environment makes the estimation pipeline accessible and extensible, since Python hosts both the optimization libraries and the tooling needed to drive simulators programmatically. Relying on iFogSim, which has been extended in subsequent versions to handle mobility, clustering, and microservice management, grounds the performance figures in a simulator that the fog research community has validated across many studies. The authors report that no datasets were generated or analyzed during the study, indicating that the contribution lies in the modeling and algorithmic framework itself rather than in empirical field measurements—a common and accepted practice in simulation-based capacity planning research.

As IoT deployments continue to multiply, the kind of foresight this method provides will become less of a luxury and more of a necessity. Operators of monitoring systems cannot afford to discover their infrastructure’s limits through service degradation, particularly in delay-priority applications where the consequences of lag are measured in safety and health outcomes. By translating the abstract question of system capacity into a concrete, computable estimate—how many end devices can join before the acceptable delay is breached—the study gives network architects a number they can design around. It is a reminder that in the race to connect everything, the most valuable computation may sometimes be the one performed before deployment: calculating exactly how far a system can stretch before it snaps.

Subject of Research: Estimating acceptable device load in Cloud-Fog computing systems for delay-sensitive IoT applications using Particle Swarm Optimization and iFogSim simulation

Article Title: Estimation of acceptable load in Cloud-Fog computing for delay-priority applications

Article References: Marković, D., Stamenković, Z., Đorđević, B., & Ranđić, S. (2026). Estimation of acceptable load in Cloud-Fog computing for delay-priority applications. Cluster Computing, 29(14), Article 812. https://doi.org/10.1007/s10586-026-06589-6

Image Credits: AI Generated

DOI: 10.1007/s10586-026-06589-6

Keywords: fog computing, cloud computing, Internet of Things, Particle Swarm Optimization, iFogSim, latency, delay-sensitive applications, resource management, sensor networks, edge computing, load estimation, task scheduling