Mobile Entities Research Articles

Landscape and local factors drive pesticide distribution in perennial agroecosystems

Abstract Pesticides constitute a major threat to biodiversity, but our understanding of the complex interactions between local and landscape factors influencing their distribution in agroecosystems remains limited. We conducted a pioneering study where we screened spiders, rodents, plants and soils for multiple pesticide residues in perennial crops (orchards and vineyards) managed under organic (N = 8) and integrated pest management (N = 8) systems. We then quantified the proportional representation of major habitat types in surrounding landscapes. Additionally, we conducted interviews with farmers to gain precise insights into pesticide applications. We expected that landscape factors would be more important for mobile entities (i.e. spiders and rodents), while management type would be relatively more important for the sedentary entities (i.e. soils and plants). We detected various pesticides within studied crop types, including several forbidden in the European Union. We found that pesticide distribution in spiders was influenced by the proportion of semi‐natural habitats in the landscape, with pesticide concentration decreasing as the proportion of semi‐natural habitats increased. Additionally, we observed that the spectrum of pesticides in spiders increased with the dominance of web‐building spiders. In contrast, pesticide levels in rodents were not affected by either landscape composition or local management type. For plants, pesticide distribution was affected by the proportion of forests and shrublands and, to some extent, by local management practices. In the case of soil, pesticide distribution was primarily determined by local management. This study marks an effort in demonstrating that both local and landscape factors play crucial roles in shaping pesticide distribution within perennial crops. Importantly, the relative importance of these factors varied across the four matrices investigated. Synthesis and applications: To comprehend the factors that determine pesticide distribution in crops, it is crucial to monitor diverse ecosystem components rather than focusing on a few model species. This approach underscores the necessity for ecologically sensitive management at landscape scale. Such management should involve the preservation and enhancement of (semi)natural habitats around crops. These combined insights can form the foundation for conservation and management initiatives aimed at mitigating the impact of pesticides on biodiversity within crops.

Time optimal gathering of myopic robots on an infinite triangular grid

This work deals with the problem of gathering n oblivious mobile entities, called robots, at a point (not known beforehand) placed on an infinite triangular grid. The robots are considered to be myopic, i.e., robots have limited visibility. Earlier works of gathering mostly considered the robots either on a plane or on a circle or on a rectangular grid under both full and limited visibility. In the triangular grid, there are two works to the best of our knowledge. The first one is by Cicerone et al. on arbitrary pattern formation where full visibility is considered. The other one by Shibata et al. which considers seven robots with 2-hop visibility that form a hexagon with one robot in the center of the hexagon in a collision-less environment under a fully synchronous scheduler.In this work, we first show that gathering on a triangular grid with 1-hop vision of robots is not possible even under a fully synchronous scheduler if the robots do not agree on any axis. So one axis agreement has been considered in this work (i.e., the robots agree on a direction and its orientation). We have also shown that the lower bound for time is Ω(n) epochs when n number of robots are gathering on an infinite triangular grid. An algorithm is then presented where a swarm of n number of robots with 1-hop visibility can gather within O(n) epochs under a semi-synchronous scheduler. So the algorithm presented here is time optimal.

On the power of bounded asynchrony: convergence by autonomous robots with limited visibility

A distributed algorithm A\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathcal {A}}$$\\end{document} solves the Point Convergence task if an arbitrarily large collection of entities, starting in an arbitrary configuration, move under the control of A\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathcal {A}}$$\\end{document} to eventually form and thereafter maintain configurations in which the separation between all entities is arbitrarily small. This fundamental task in the standard OBLOT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal {OBLOT}$$\\end{document} model of autonomous mobile entities has been previously studied in a variety of settings, including full visibility, exact measurements (including distances and angles), and synchronous activation of entities. Our study concerns the minimal assumptions under which entities, moving asynchronously with limited and unknown visibility range and subject to limited imprecision in measurements, can be guaranteed to converge in this way. We present an algorithm operating under these constraints that solves Point Convergence, for entities moving in two or three dimensional space, with any bounded degree of asynchrony. We also prove that under similar realistic constraints, but unbounded asynchrony, Point Convergence in the plane is not possible in general, contingent on the natural assumption that algorithms maintain the (visible) connectivity among entities present in the initial configuration. This variant, that we call Cohesive Convergence, serves to distinguish the power of bounded and unbounded asynchrony in the control of autonomous mobile entities, settling a long-standing question whether in the Euclidean plane synchronously scheduled entities are more powerful than asynchronously scheduled entities.

An IoT Intelligent Approach for Safety and Efficiency of Robotic Medicine Delivery in Hospitals

In this paper, we introduce an IoT-based robotic medicine delivery system designed to boost safety and efficiency in hospital settings. This IoT-embedded robotic system integrates advanced sensors such as proximity, temperature, pressure, pulse rate, etc., sensors for ensuring real-time health and environmental monitoring behind this system. The robot is connected to a centralised controller, enabling healthcare workers to monitor patients using a cloud-based system. . Our robotic system moves about with the support of both line follower and LiDAR scanning technology for environmental safety and proximity detection. Experimental results show that the robotic system was able to navigate static obstacles and dynamically move away from the mobile entities within its reach without touching them. Besides, the proposed robotic system was able to reach the bed at the right time under normal operating conditions, which shows the efficiency of this approach in real-time settings. Patient feedback suggests that patients are very happy about the system, in terms of its usefulness, trustworthiness, and to their suprise to be taken care of by a robot. Overall, our study shows the potential of the proposed robotic system in streamlining the existing medicine delivery process in hospitals. It can potentially improve various aspects including safety, efficiency, patient compliance, and quality of care delivery. The promising results suggest further studies for incorporating advanced features and for ensuring compliance with regulatory requirements. Additional studies are to be conducted to further improve the proposed sensor-based robotic medicine delivery system, to facilitate its adoption in hospitals.

A Novel Hybrid Protocol and Code Related Information Reconciliation Scheme for Physical Layer Secret Key Generation

Wireless networks are vulnerable to various attacks due to their open nature, making them susceptible to eavesdropping and other security threats. Eavesdropping attack takes place at the physical layer. Traditional wireless network security relies on cryptographic techniques to secure data transmissions. However, these techniques may not be suitable for all scenarios, especially in resource-constrained environments such as wireless sensor networks and adhoc networks. In these networks having limited power resources, generating cryptographic keys between mobile entities can be challenging. Also, the cryptographic keys are computationally complex and require key management infrastructure. Physical Layer Key Generation (PLKG) is an emerging solution to address these challenges. It establishes secure communication between two users by taking advantage of the wireless channel's inherent features. PLKG process involves channel probing, quantization, information reconciliation (IR) and privacy amplification to generate symmetric secret key. The researchers have used various PLKG techniques to get the secret key, sTop of Form
 till they face problems in the IR scheme to obtain symmetric keys between the users who share the same channel for communication. Both the code based and protocol based methods proposed in the literature have advantages and limitations related to their performance parameters such as information leakage, interaction delay and computation complexity. This research work proposes a novel IR mechanism that combines the protocol and code-based error correction methods to obtain reduced Bit Mismatch Rate (BMR), reduced information leakage, reduced interaction delay, and reduced computational time to enhance physical layer secret key's quality. In the proposed research work, the channel samples are generated using the Received Signal Strength (RSS) and Channel Impulse Response (CIR) parameters. These samples are quantized using Vector Quantization with Affinity Propagation Clustering (VQAPC) method to generate the preliminary key. The samples collected by the two users who wish to communicate, (for example Alice and Bob) will be different due to noise in the channel and hardware limitations. Hence their preliminary keys will be different. Removing this discrepancy between Bob's and Alice's initial keys, using novel Hybrid Protocol and Code related Information Reconciliation (HPC-IR) scheme to generate error corrected key, is the most important contribution of this research work. This key is further encoded by the MD5 hash function to generate a final secret key for exchanging information between two users over the wireless channel. It is observed that the proposed HPC-IR scheme achieves BMR of 19.4%, information leakage is 0.002, interaction delay is 0.001 seconds and computation time is 0.02 seconds.

Dose-dependent long-distance movement of microRNA399 duplex regulates phosphate homeostasis in Arabidopsis.

MicroRNA399 (miR399), a phosphate (Pi) starvation-induced long-distance signal, is first produced in shoots and moves to roots to suppress PHO2 encoding a ubiquitin conjugase, leading to enhanced Pi uptake and root-to-shoot translocation. However, the molecular mechanism underlying miR399 long-distance movement remains elusive. Hypocotyl grafting with various Arabidopsis mutants or transgenic lines expressing artificial miR399f was employed. The movement of miR399 across graft junction and the rootstock PHO2 transcript and scion Pi levels were analyzed to elucidate the potential factors involved. Our results showed that miR399f precursors are cell-autonomous and mature miR399f movement is independent of its biogenesis, sequence context, and length (21 or 22 nucleotides). Expressing viral silencing suppressor P19 in the root stele or blocking unloading in the root phloem pore pericycle (PPP) antagonized its silencing effect, suggesting that the miR399f/miR399f* duplex is a mobile entity unloaded through PPP. Notably, the scion miR399f level positively correlates with its amount translocated to rootstocks, implying dose-dependent movement. This study uncovers the molecular basis underlying the miR399-mediated long-distance silencing in coordinating shoot Pi demand with Pi acquisition and translocation activities in the roots.

Online Distributed Optimization for Energy-Efficient Computation Offloading in Air-Ground Integrated Networks

Driven by ever-increasing vehicular intelligent computation-intensive and delay-sensitive services, this paper investigates the computing offloading in unmanned aerial vehicle (UAV)-assisted vehicular networks. Due to the limited onboard energy and computational resources of the mobile entities (i.e., the vehicles and the UAV), it is significant to explore the collaborative computation among the vehicles, the UAV, and the terrestrial computing servers for improving energy efficiency (EE) while trading off the service delay. Unlike existing work in the literature that is based on offline settings with a global view, an online distributed mechanism is proposed to cope with the spatial and temporal variations of the networks. Specifically, upon the arriving tasks and the real-time channel conditions, mobile entities adaptively decide about the task offloading and computational resources allocation in parallel. Moreover, the UAV also designs its trajectory with the residual battery capacity taken into account. Theoretical analysis shows that the developed approach can achieve the EE-delay tradeoff as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$[ {O(1/V),O(V)} ]$</tex-math></inline-formula> with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V$</tex-math></inline-formula> being a control parameter, and can strike a flexible balance between them by tuning <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V$</tex-math></inline-formula> . Numerical results verify the theoretical analysis and reveal that the performance gain can be obtained over conventional methods in the EE performance.

A DNA Origami-Based Biointerface to Interrogate the Spatial Requirements for Sensitized T-Cell Antigen Recognition.

When T cells scan the surface of antigen-presenting cells (APCs), they can detect the presence of just a few antigenic peptide/MHC complexes (pMHCs), in some cases even a single agonist pMHC. These are typically vastly outnumbered by structurally similar yet non-stimulatory endogenous pMHCs. How T cells achieve this enormous sensitivity and selectivity is still not clear, in particular in view of the rather moderate (1-100μM) affinity that T-cell receptors (TCRs) typically exert for antigenic pMHCs. Experimental approaches that enable the control and quantification of physical input parameters within the context of the immunological synapse to precisely interrogate the molecular consequences of TCR-engagement, appear highly advantageous when searching for better answers.We here describe the implementation of a biointerface that allows to experimentally define molecular distances between T-cell ligands as a means to correlate them with molecular dynamics of antigen engagement, downstream signaling, and the overall T-cell response. The basis of this biointerface is DNA origami nanostructures, which are (i) rigid and highly versatile platforms that can (ii) be embedded as laterally mobile entities within supported lipid bilayers and functionalized (iii) in a site-specific and orthogonal manner with (iv) one or more proteins of choice.

Mobile-Chain: Secure blockchain based decentralized authentication system for global roaming in mobility networks

Designing a secure and efficient authentication protocol is crucial and challenging in the mobility network. Due to the seamless roaming of mobile users over multiple foreign agents and the broadcast nature of the communication channel, the mobile networks are often exposed to several network attacks. To achieve perfect authentication and secure communication among mobility entities like MU (Mobile User), FA (Foreign Agent) and HA (Home Agent), the researchers have proposed numerous authentication protocols in the past. However, the existing protocols for the mobility environments are insufficient to address the fundamental security concerns and an adversary can impersonate the mobile user at anytime. Thus, we propose Mobile-Chain, a secure blockchain-based authentication system for mobility environments. The proposed Mobile-Chain is designed to protect user privacy and guarantees provable security like authentication, anonymity, untraceability, confidentiality, data integrity, and decentralization. The implementation of the security framework has been done on the ethereum blockchain platform using smart contracts written in a solidity programming language. The security analysis reveals that Mobile-Chain is robust against various security threats to which mobility networks are vulnerable. Besides, the authentication framework has been measured through a formal security verification tool known as Automated Validation of Internet Security Protocol and Application (AVISPA). Notably, the performance evaluation of the proposed protocol proves that it maintains performance gain, computationally efficient, and implementable in resource-limited wireless and mobility environments.

Mobility Digital Twin: Concept, Architecture, Case Study, and Future Challenges

A Digital Twin is a digital replica of a living or nonliving physical entity, and this emerging technology attracted extensive attention from different industries during the past decade. Although a few Digital Twin studies have been conducted in the transportation domain very recently, there is no systematic research with a holistic framework connecting various mobility entities together. In this study, a mobility digital twin (MDT) framework is developed, which is defined as an artificial intelligence (AI)-based data-driven cloud–edge–device framework for mobility services. This MDT consists of three building blocks in the physical space (namely, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Human</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Vehicle</i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Traffic</i> ), and their associated Digital Twins in the digital space. An example cloud–edge architecture is built with Amazon Web Services (AWS) to accommodate the proposed MDT framework and to fulfill its digital functionalities of storage, modeling, learning, simulation, and prediction. A case study of the personalized adaptive cruise control (P-ACC) system is conducted, which integrates the key microservices of all three digital building blocks of the MDT framework: 1) the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Human Digital Twin</i> with user management and driver type classification; 2) the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Vehicle Digital Twin</i> with cloud-based advanced driver-assistance systems (ADAS); and 3) the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Traffic Digital Twin</i> with traffic flow monitoring and variable speed limit. Future challenges of the proposed MDT framework are discussed toward the end of the article, including standardization, AI for computing, public or private cloud service, and network heterogeneity.

Embodying Meaning Visually: From Perceptual Dynamics to Motion Kinematics

Abstract This paper adopts an embodied cognitive perspective to review the significance of dynamic patterns in the visual expression of meaning. Drawing upon the work of Rudolf Arnheim we first show how perceptual dynamics of inanimate objects might be extended in order to structure abstract meaning in fixed images such as paintings. Second, we evaluate existing experimental work that shows how simple kinematic structures within a stationary frame might embody such high-level properties as perceptual causality and animacy. Third and last, we take inspiration from these experiments to shed light on the expressiveness of dynamic patterns that unfold once the frame itself becomes a mobile entity (i.e., camera movement). In the latter case we will also present a filmic case study, showing how filmmakers might resort to these dynamic patterns so as to embody a film’s story content, while simultaneously offering a further avenue for film scholars to deepen their engagement with the experimental method.

A trustable architecture over blockchain to facilitate maritime administration for MASS systems

Maritime Autonomous Surface Ship (MASS) is widely deemed as the future of global shipping. The cyber vulnerability has however been identified as an emerging problem and a potential barrier influencing MASS development. This paper, through the investigation of the fundamental trust problem with regards to the cyber security of MASS systems, aims to develop a blockchain-based scheme for the trust management of MASS. The innovative idea of using blockchain within the MASS context is that the mobile entities in the MASS operational environment constitute a decentralized opportunity network, which makes blockchain an appealing tool to provide a solution to evaluating and maximizing the trust over the dynamics of the entities. This paper elaborates the mechanism by which the MASS entities participate in keeping the main chain. Firstly, the paper illustrates how the Belief of Trust (BoT) among the entities is encoded and assembled into the chain, to allow MASS entities to have an initial judgement towards another entity before they get acquainted. Secondly, at the consensus layer of blockchain technique, it addresses how the witness, who has a temporary right of producing a block and append it to the chain, can be elected among the nodes and how to incent the nodes to maintain the blockchain from a proof-of-stake perspective. Finally, this paper describes how the MASS entities can use the certificate dependence information to evaluate the trust transition in the MASS operating environment. Typical scenarios are delineated to show the procedure of certificate inquiry, handover of controls between maritime supervision centers and shore-side remote control centers in case of the occurrence of unexpected events. The findings provide any entity in an MASS network with an effective solution to evaluating the degree of trust he can have for any targeted node/participant. They can therefore help choose better (more trustable) nodes to maintain the MASS network's knowledge of evidence to judge the trust on an unknown member.

Tight bounds on exploration of constantly connected cacti-paths

In this paper, we study the necessary and sufficient time to explore constantly connected dynamics graphs by a mobile entity (agent). A dynamic graph is constantly connected if for each time units, there exists a stable connected spanning tree [10]. We focus on the case where the underlying graph is a cactus-path (graph reduced to a path of k rings in which two neighbor rings have at most one vertex in common) and we assume that the agent knows the dynamics of the graph. We show that 5n - Θ(1) time units are necessary and sufficient to explore any constantly connected dynamic graph based on the cactus-path 〖Ch〗_(2,n) (composed of two same size ringsn). The upper bound is generalized on dynamic graphs based on cacti-paths with k rings. We show that for any constantly connected dynamic graph of size N based on a cactus-path, 4N -max{n_1,n_k} -3k -3 time units are sufficient to explore the graph, with k the length of the path, N=∑_(i=1)^k▒n_i -k+1 the size of the dynamic graph and n_i the size of the ring which is at position i starting from left to right.

On the development of flexible mobile multi-sensor units based on open-source hardware platforms and a reference framework

For some IoT applications, mobile entities are considered as the main source of sensed data, requiring the attachment of sensor modules on them. The endowing of sensing capabilities to such mobile entities can be performed in different ways, but the adoption of a reference hardware framework can bring a series of advantages, specially in dynamic complex scenarios. This article exploits the MSensorMob2 multi-sensor hardware framework for monitoring in areas with disconnection periods, comprising sensing, transmission and reconfiguration functions. Comprehensive analyses on multiple open-source hardware platforms are conducted, assessing their costs, deployment constraints and performance issues when implementing this development framework.

CoCo

As mobility is an important key to many applications, this work proposes a location-less model to represent mobility that is used to quantify correlations between mobility traces collected by built-in sensors on smartphones. We analyze the mobility correlations from two aspects: co-direction relationship and co-movement relationship . The former is to quantify the similarity of macroscopic moving directions between mobility traces, whereas the latter is to quantify the similarity of their microscopic vibrations. To verify the merits of the two proposed metrics, an exemplary use case, termed co-mobility detection , is considered to determine if two mobile devices share the same journey on the same mobile entity (e.g., carried by the same person). Comprehensive experiments with diverse combinations of mobility traces are conducted in three different environments with different density of Wi-Fi networks. The experimental results indicate that the proposed metrics can effectively evaluate both the coarse-grained similarity of moving directions and the fine-grained similarity of movement variations along mobility traces. The accuracy of the co-mobility detection algorithm can achieve 90% on average for mobility traces with a duration of 70 s.

A structured methodology for designing distributed algorithms for mobile entities

Following the wide investigation in distributed computing issues by mobile entities of the last two decades, we consider the need of a structured methodology to tackle the arisen problems. The aim is to simplify both the design of the resolution algorithms and the writing of the required correctness proofs. We would encourage the usage of a common framework in order to help both algorithm designers and reviewers in the intricate work of delivering and analyzing the proposed resolution strategies.We demonstrate the effectiveness and usefulness of the new methodology by highlighting various peculiarities arising in different scenarios. In particular, we consider two different tasks for asynchronous entities moving in the Euclidean plane and in graphs, respectively. We show how two resolution strategies have been designed by following the accurate guide dictated by the methodology. Furthermore, we also show how the corresponding correctness proofs are obtained.

Cooperative multi-agent model for collision avoidance applied to air traffic management

In the future, Air Traffic Control (ATC) will have to cope with a radical change in air traffic. Apart from the probable increase in traffic that will push the system to its limits, the insertion of new aerial vehicles such as drones into the airspace – with different flight performances, and utterly different objective – will increase its complexity. Current research aims at increasing the level of automation and/or partial delegation of the control to on-board systems. In this work, we investigate the collision avoidance management problem using a decentralized distributed approach. We propose an autonomous and generic multi-agent system to address this complex problem, where mobile entities are agents, that use a finite set of discrete speed vector modifications to follow their trajectories while avoiding separation losses. We validate our system using a state-of-the-art benchmark. The results underline the adequacy of our local and cooperative approach to efficiently solve the studied problem, competing with centralized methods. Additionally, the conducted sensitivity analysis underlines the robustness of our approach regarding some used parameters.

Pastoral dairying in rural Mongolia

In this photo essay, I illustrate ethnographic encounters with dairying practices and dairy microbes in various regions of Mongolia. Drawing on fieldwork conducted during two consecutive summers this essay focuses on the sociocultural role of microbial starter cultures in producing diverse dairy products (such as fermented mare’s milk) and in cross-generational knowledge transfer. The Mongolian word for starter culture is khöröngö, which also means capital and heritage. In this context, a sociocultural anthropological approach sheds new light on starter cultures as mobile entities of value across space and time.

Mobile Robots with Uncertain Visibility Sensors: Possibility Results and Lower Bounds

We consider mobile robotic entities that have to cooperate to solve assigned tasks. In the literature, two models have been used to model their visibility sensors: the full visibility model, where all robots can see all other robots, and the limited visibility model, where there exists a limit [Formula: see text] such that all robots closer than [Formula: see text] are seen and all robots further than [Formula: see text] are not seen. We introduce the uncertain visibility model, which generalizes both models by considering that a subset of the robots further than [Formula: see text] cannot be seen. An empty subset corresponds to the full visibility model, and a subset containing every such robot corresponds to the limited visibility model. Then, we explore the impact of this new visibility model on the feasibility of benchmarking tasks in mobile robots computing: gathering, uniform circle formation, luminous rendezvous, and leader election. For each task, we determine the weakest visibility adversary that prevents task solvability, and the strongest adversary that allows task solvability. Our work sheds new light on the impact of visibility sensors in the context of mobile robot computing, and paves the way for more realistic algorithms that can cope with uncertain visibility sensors.

A blockchain-based service for inviolable presence registration of mobile entities

Several applications can benefit from recording information about the places a mobile entity visits and the length of time it spends there (e.g., shoppers, employees, buses, portable equipment, autonomous robots). This paper presents our approach to recording spatio-temporal presence information in a secure and inviolable way using a Distributed Ledger Technology. We implemented this solution as a middleware service that uses Complex Event Processing on smartphones to record beacon-smartphone proximity data in a blockchain efficiently. We have built upon the previous version of our service to include access control to the stored information. We analyzed the impact of this addition on the service’s performance and observed that it introduced very little overhead while significantly increasing user privacy. Furthermore, we compared the effect of using different blockchain technologies on overall service performance and characterized scenarios where using either IoTeX or Ethereum can be suitable for this type of application.