Event-driven Messages Research Articles

Enhanced Congestion Control Model Based on Message Prioritization and Scheduling Mechanism in Vehicle-to-Infrastructure (V2I)

Vehicular Ad Hoc Networks (VANETs) is an origination of Mobile Ad-Hoc Network (MANET), where road vehicles will distribute messages and provide safety alerts to notice hazardous circumstances to the drivers. One of its greatest challenges is ensuring Quality of Service (QoS) owing to channel sharing, high traffic and topology changes in VANETs. These challenges cause of degradation of network performance. Congestion control should be properly considered to improve the network performance and transmission message over VANETs. However, there seem significant limitations to most of the other current congestion control mechanisms. In this paper, an enhanced congestion control model based on prioritization and scheduling-based strategy is proposed. This strategy assigns priorities of the safety messages and non-safety messages based of the message type and network condition. Further, safety message can be classified into event-driven messages and beacon messages. At that point, all messages transmit into the appropriate queue based on their priority and schedule all messages in each queue. However, when new message enqueue, reschedule in each queue may cause additional unwanted delay to be processed cause of inefficient scheduling technique. Thus, an improved dynamic scheduling algorithm also proposed to schedule the messages in this circumstance.

A study on universal observation control system and its application for LAMOST

The observatory control system (OCS), a part of automated control of Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), runs on the CentOS6 platform and implements the communication between modules based on Common Object Request Broker Architecture (CORBA). However, CORBA is complicated and has limited development support; moreover, the official support for CentOS6 has ended. OCS inherently has some shortcomings such as the over-concentration of control and the blocking of device status processing, which hinder the realization of automated observation control of LAMOST. Therefore, this study designs and implements a universal observation control system (UOCS) for optical telescopes. The UOCS takes the device command as the basic execution unit, controls the device execution logic using observation script, controls the observation logic by event-driven messaging, and realizes mutual decoupling between modules via a distributed control mode, thereby ensuring high system robustness. The UOCS performs significantly better than OCS in terms of the observation performance, operator complexity, and communication error. Currently, UOCS is applied to the automated control of some devices and subsystems in LAMOST observation. It will be applied to the automated observation control of Multi-channel Photometric Survey Telescope by 2021.

Industry practices and challenges for the evolvability assurance of microservices

ContextMicroservices as a lightweight and decentralized architectural style with fine-grained services promise several beneficial characteristics for sustainable long-term software evolution. Success stories from early adopters like Netflix, Amazon, or Spotify have demonstrated that it is possible to achieve a high degree of flexibility and evolvability with these systems. However, the described advantageous characteristics offer no concrete guidance and little is known about evolvability assurance processes for microservices in industry as well as challenges in this area. Insights into the current state of practice are a very important prerequisite for relevant research in this field.ObjectiveWe therefore wanted to explore how practitioners structure the evolvability assurance processes for microservices, what tools, metrics, and patterns they use, and what challenges they perceive for the evolvability of their systems.MethodWe first conducted 17 semi-structured interviews and discussed 14 different microservice-based systems and their assurance processes with software professionals from 10 companies. Afterwards, we performed a systematic grey literature review (GLR) and used the created interview coding system to analyze 295 practitioner online resources.ResultsThe combined analysis revealed the importance of finding a sensible balance between decentralization and standardization. Guidelines like architectural principles were seen as valuable to ensure a base consistency for evolvability and specialized test automation was a prevalent theme. Source code quality was the primary target for the usage of tools and metrics for our interview participants, while testing tools and productivity metrics were the focus of our GLR resources. In both studies, practitioners did not mention architectural or service-oriented tools and metrics, even though the most crucial challenges like Service Cutting or Microservices Integration were of an architectural nature.ConclusionsPractitioners relied on guidelines, standardization, or patterns like Event-Driven Messaging to partially address some reported evolvability challenges. However, specialized techniques, tools, and metrics are needed to support industry with the continuous evaluation of service granularity and dependencies. Future microservices research in the areas of maintenance, evolution, and technical debt should take our findings and the reported industry sentiments into account.

Sporadic Ultra-Time-Critical Crowd Messaging in V2X

Life-critical warning message, abbreviated as warning message, is a special event-driven message that carries emergency information in Vehicle-to-Everything (V2X). Three important characteristics that distinguish warning messages from ordinary vehicular messages are sporadicity, crowding, and ultra-time-criticality. Specifically, warning messages come only once in a while in a sporadic manner; however, when they come, they tend to come as a crowd and they need to be delivered in short order. This paper puts forth a medium-access control (MAC) protocol for warning messages. The overall MAC protocol operates by means of interrupt-and-access. To circumvent potential inefficiency arising from message sporadicity, we adopt an override network architecture whereby warning messages are delivered on the spectrum of the ordinary vehicular messages. A vehicle with a warning message first sends an interrupt signal to pre-empt the transmission of ordinary messages, so that the warning message can use the wireless spectrum originally allocated to ordinary messages. In this way, no exclusive spectrum resources need to be pre-allocated to the sporadic warning messages. Following the interrupt, for transmissions of ultra-time-critical crowd messages, we employ advanced channel access techniques to ensure reliable message delivery within an ultra-short time in the order of 10 ms.

A novel clustering technique to stop congestion occur vehicular ad-hoc networks using node density based on received signal strength

Vehicular Ad Hoc Network (VANET) has received better consideration from academic researcher and automobile companies in modern years. Meanwhile, Congestion control remains the major area of research in VANET due to its characteristics such as high mobility, high vehicle density, and unbounded network size, frequent exchange of information, rapidly changing network topology, and lack of central management. Congestion in the VANET broadcast channel may occur, because of number of vehicles in a relatively tiny area raises, the communications channel becomes exceed by beacon message, and event-driven messages. Researchers have suggested a number of answers to control these issues and also to reduce congestion in VANET atmosphere. Congestion in VANET occurs when the vehicles are in the dense part while the network node is carrying more data than it can handle. More vehicles in cluster area are attempting to broadcast simultaneously in dense condition, it will reduce Packet Delivery Ratio and thus congestion will occur. We proposed density based dynamic clustering (DBDC) which finds the high dense region in the cluster and do sub-clustering. First, we find Average Vehicle Density Threshold Value using Received Signal Strength (RSS) to determine the high dense part. Performance result shows our approach is better in all aspects comparing with VWCA clustering approach and also provides high cluster stability.

IEEE 1609.4 다중 채널 운용에서 사건기반 긴급메시지의 지연 성능 분석

IEEE 1609.4 다중 채널 운용에서 사건기반 긴급메시지의 지연 성능 분석

Secure and Blockchain-Based Emergency Driven Message Protocol for 5G Enabled Vehicular Edge Computing.

Basic safety message (BSM) are messages that contain core elements of a vehicle such as vehicle’s size, position, speed, acceleration and others. BSM are lightweight messages that can be regularly broadcast by the vehicles to enable a variety of applications. On the other hand, event-driven message (EDM) are messages generated at the time of occurrence such as accidents or roads sliding and can contain much more heavy elements including pictures, audio or videos. Security, architecture and communication solutions for BSM use cases have been largely documented on in the literature contrary to EDM due to several concerns such as the variant size of EDM, the appropriate architecture along with latency, privacy and security. In this paper, we propose a secure and blockchain based EDM protocol for 5G enabled vehicular edge computing. To offer scalability and latency for the proposed scenario, we adopt a 5G cellular architecture due to its projected features compared to 4G tong-term evaluation (LTE) for vehicular communications. We consider edge computing to provide local processing of EDM that can improve the response time of public agencies (ambulances or rescue teams) that may intervene to the scene. We make use of lightweight multi-receiver signcryption scheme without pairing that offers low time consuming operations, security, privacy and access control. EDM records need to be kept into a distributed system which can guarantee reliability and auditability of EDM. To achieve this, we construct a private blockchain based on the edge nodes to store EDM records. The performance analysis of the proposed protocol confirms its efficiency.

On the impact of service-oriented patterns on software evolvability: a controlled experiment and metric-based analysis.

BackgroundDesign patterns are supposed to improve various quality attributes of software systems. However, there is controversial quantitative evidence of this impact. Especially for younger paradigms such as service- and Microservice-based systems, there is a lack of empirical studies.ObjectiveIn this study, we focused on the effect of four service-based patterns—namely Process ion, Service Façade, Decomposed Capability, and Event-Driven Messaging—on the evolvability of a system from the viewpoint of inexperienced developers.MethodWe conducted a controlled experiment with Bachelor students (N = 69). Two functionally equivalent versions of a service-based web shop—one with patterns (treatment group), one without (control group)—had to be changed and extended in three tasks. We measured evolvability by the effectiveness and efficiency of the participants in these tasks. Additionally, we compared both system versions with nine structural maintainability metrics for size, granularity, complexity, cohesion, and coupling.ResultsBoth experiment groups were able to complete a similar number of tasks within the allowed 90 min. Median effectiveness was 1/3. Mean efficiency was 12% higher in the treatment group, but this difference was not statistically significant. Only for the third task, we found statistical support for accepting the alternative hypothesis that the pattern version led to higher efficiency. In the metric analysis, the pattern version had worse measurements for size and granularity while simultaneously having slightly better values for coupling metrics. Complexity and cohesion were not impacted.InterpretationFor the experiment, our analysis suggests that the difference in efficiency is stronger with more experienced participants and increased from task to task. With respect to the metrics, the patterns introduce additional volume in the system, but also seem to decrease coupling in some areas.ConclusionsOverall, there was no clear evidence for a decisive positive effect of using service-based patterns, neither for the student experiment nor for the metric analysis. This effect might only be visible in an experiment setting with higher initial effort to understand the system or with more experienced developers.

Time-to-Collision-Based Awareness and Congestion Control for Vehicular Communications

Vehicular wireless communications require both congestion control to guarantee the availability of a fraction of the bandwidth for safety-related event-driven messages in emergency cases, and awareness control to adapt the beaconing activity to the application needs and surrounding traffic situation. Most current approaches either ignore the traffic situation and only adapt the beaconing rate to the channel congestion state or override the congestion control limits, leading to questionable results in both cases. In this paper, we conceive and validate a novel approach, combining both aspects. Based on distributed Network Utility Maximization (NUM), our algorithm satisfies the constraints on channel availability, whereas the safety of the surrounding traffic situation is captured with a time-to-collision metric, used to assign priorities in the optimal allocation problem. The performance of the proposed approach is validated and compared to other popular algorithms. Results show that our proposal automatically anticipates a potential increase in rate due to a critical safety situation, but does not interfere with the reserved bandwidth for safety applications.

Supporting Beacon and Event-Driven Messages in Vehicular Platoons through Token-Based Strategies.

Timely and reliable inter-vehicle communications is a critical requirement to support traffic safety applications, such as vehicle platooning. Furthermore, low-delay communications allow the platoon to react quickly to unexpected events. In this scope, having a predictable and highly effective medium access control (MAC) method is of utmost importance. However, the currently available IEEE 802.11p technology is unable to adequately address these challenges. In this paper, we propose a MAC method especially adapted to platoons, able to transmit beacons within the required time constraints, but with a higher reliability level than IEEE 802.11p, while concurrently enabling efficient dissemination of event-driven messages. The protocol circulates the token within the platoon not in a round-robin fashion, but based on beacon data age, i.e., the time that has passed since the previous collection of status information, thereby automatically offering repeated beacon transmission opportunities for increased reliability. In addition, we propose three different methods for supporting event-driven messages co-existing with beacons. Analysis and simulation results in single and multi-hop scenarios showed that, by providing non-competitive channel access and frequent retransmission opportunities, our protocol can offer beacon delivery within one beacon generation interval while fulfilling the requirements on low-delay dissemination of event-driven messages for traffic safety applications.

Dynamic Contention Window based Safety-Application Model for Vehicular Ad-hoc Networks

The paper proposes a dynamic contention window based safety-application model to provide service to the Event Driven Messages (EDMs) over the beacon messages by varying the Contention Window (CW) size dynamically. This is done to ensure timely distribution of EDM as these messages are most critical messages and require immediate transmission in order to maintain the essence of the network. For prioritization, whenever the vehicular network detects an EDM, the system holds all the beacon messages, prioritizing EDMs and reduces the CW size by a pre-defined factor. This factor is continuously increased if consecutive EDMs are received at the vehicles queue. Consequently, for broadcasting beacons in the absence of EDM, the proposed model first evaluates backlogged packets, which is estimated by using round trip time and varies the size of CW accordingly. This is done to maintain the network performance even in the absence of EDM. The model is validated against the simulation result. It can be evident from the simulation results that our model provides smallest CW without degrading the performance of the network in terms of collision probability.

A Review of Congestion Control Schemes for Vehicular Ad-Hoc Network (VANET) Communication

Intelligent Transportation Systems (ITS) are built on top of self-organizing networks, known as Vehicular Ad hoc Networks (VANET). In VANET, each vehicle equipped with communication devices represents a node and is allowed to send and receive safety messages through wireless communication channels. These messages are either periodic (beacons) or event-driven. Beacons are transmitted periodically while the event-driven messages are generated when an abnormal condition or an imminent danger is detected. The event-driven messages should be delivered to neighbouring nodes with high reliability and limit time as a single delayed or lost message could result in loss of lives. In dense network, the periodic messages broadcast lead to broadcast storm/blind flooding problem in VANETs. It is very important to keep the communication channel free from congestion in order to ensure timely and reliable delivery of event-driven safety messages. This study presents a review of existing congestion control schemes for VANETs with the aim of discussing the contributions and drawbacks of the algorithms.

Mobility dependent clustering-based data transmission under variable data rate for different node densities in vehicular ad hoc network

Vehicular environments impose stringent requirements on the communication channels due to their inherent feature of being geographically constrained, unpredictable vehicular density, varying channel capacity and highly dynamic in nature. Enhancement in the existing vehicular communication technologies is important not only for efficient utilisation of the available bandwidth but also for event-driven safety message dissemination in vehicular ad hoc network (VANET). From safety point of view these enhancements demand high reliability; time bound delivery and inevitable channel access. In this paper we compare and evaluate the performance of mobility aware clustering based single-hop and multi-hop broadcast network in the IEEE 802.11p standard for different node densities and varying data transfer rates. Simulation results using NS-2 are presented to evaluate various quality of service (QoS) parameters such as, throughput, packet delivery ratio and end to end delay. Significant observations have been made which would envisage further research in this field.

The Traffic Adaptive Data Dissemination (TrAD) Protocol for both Urban and Highway Scenarios.

The worldwide economic cost of road crashes and injuries is estimated to be US$518 billion per year and the annual congestion cost in France is estimated to be €5.9 billion. Vehicular Ad hoc Networks (VANETs) are one solution to improve transport features such as traffic safety, traffic jam and infotainment on wheels, where a great number of event-driven messages need to be disseminated in a timely way in a region of interest. In comparison with traditional wireless networks, VANETs have to consider the highly dynamic network topology and lossy links due to node mobility. Inter-Vehicle Communication (IVC) protocols are the keystone of VANETs. According to our survey, most of the proposed IVC protocols focus on either highway or urban scenarios, but not on both. Furthermore, too few protocols, considering both scenarios, can achieve high performance. In this paper, an infrastructure-less Traffic Adaptive data Dissemination (TrAD) protocol which takes into account road traffic and network traffic status for both highway and urban scenarios will be presented. TrAD has double broadcast suppression techniques and is designed to adapt efficiently to the irregular road topology. The performance of the TrAD protocol was evaluated quantitatively by means of realistic simulations taking into account different real road maps, traffic routes and vehicular densities. The obtained simulation results show that TrAD is more efficient in terms of packet delivery ratio, number of transmissions and delay in comparison with the performance of three well-known reference protocols. Moreover, TrAD can also tolerate a reasonable degree of GPS drift and still achieve efficient data dissemination.

Event-Driven Messaging for Offline Data Quality Monitoring at ATLAS

During LHC Run 1, the information flow through the offline data quality monitoring in ATLAS relied heavily on chains of processes polling each other's outputs for handshaking purposes. This resulted in a fragile architecture with many possible points of failure and an inability to monitor the overall state of the distributed system. We report on the status of a project undertaken during the LHC shutdown to replace the ad hoc synchronization methods with a uniform message queue system. This enables the use of standard protocols to connect processes on multiple hosts; reliable transmission of messages between possibly unreliable programs; easy monitoring of the information flow; and the removal of inefficient polling-based communication.

A novel context-aware variable interval MAC protocol to enhance event-driven message delivery in IEEE 802.11p/WAVE vehicular networks

Vehicular Ad hoc NETworks (VANETs) are the key to the future of Intelligent Transportation Systems (ITS). In VANETs, event driven safety messages, generated for example when an abnormal condition or an imminent danger is detected, have stringent requirements on delay. However, due to the inherent drawbacks of CSMA which is used in VANETs, such messages will not be able to meet the timing constraints in dense traffic scenarios. In this paper, we introduce a Context Aware Variable Interval MAC (CAVI-MAC) protocol for IEEE 802.11p/WAVE VANETs which utilizes multichannel access scheduling in a novel way. We differentiate between event driven and periodic messages by assigning priorities and also suggest a probabilistic model for addressing interference from hidden terminals. We also use a novel atomic model to analyze the propagation of event driven messages. Extensive simulations over lower Manhattan city scenario for a variety of metrics indicate that CAVI-MAC provides better performance (packet delivery ratio) than any of the existing protocols.

An Efficient Message Dissemination Technique in Platooning Applications

Autonomous driving in road trains, a.k.a. platooning, may reduce fuel consumption considerably if the inter-vehicle distances are kept short. However, to do this, the intra-platoon communication must not only be reliable but also able to meet strict deadlines. While time-triggered messages are the foundation of most distributed control applications, platooning is likely to also require dissemination of event-driven messages. While much research work has focused on minimizing the age of periodic messages, state-of-the-art for disseminating event-driven messages is to let all nodes repeat all messages and focus on mitigating broadcast storms. We derive an efficient message dissemination scheme based on relay selection which minimizes the probability of error at the intended receiver(s) for both unicast and broadcast, without degrading the performance of co-existing time-triggered messages. We present a full analysis of the resulting error probability and delay, when relayers, selected by our algorithm, are used to disseminate messages within a platoon. Numerical results indicate that the proposed relaying policy significantly enhances the reliability for a given delay.

Robust and Efficient Broadcast Scheme of Event-Driven Warning Messages for Vehicular Environments

In vehicular ad hoc networks, it is important to broadcast time-sensitive and event-driven warning messages to vehicles. To improve traffic safety, a robust and efficient dissemination protocol is proposed for vehicle-to-vehicle communication aimed at supporting the dissemination of event-driven warning messages to approaching vehicles in an emergency situation. The objective is to minimize the number of rebroadcasting transmissions while simultaneously achieving low transmission latency and reducing redundant messages. To guarantee efficiency, the scheme time parameters are designed according to the mobility and the number information of neighboring vehicles. To guarantee robustness, the message dissemination performance of multiple vehicles is analyzed under various traffic conditions. Simulation studies are conducted with the ns-2.35 network simulation, and the robust and efficient dissemination protocol and two existing protocols (Flood, DV-CAST) are compared in transmission latency, delivery ratio, and total packets transmitted.

Cross-layer congestion control model for urban vehicular environments

Congestion control in Vehicular Ad Hoc Networks (VANETs) is challenging due to limited bandwidth, dynamic topology and lack of central coordination. Unlike previous works which focus on congestion control with a fixed channel load threshold that causes bandwidth wastage, this paper presents a cross-layer congestion control model which consists of two modules to alleviate congestion in the congestion detection center. In first module, the event-driven messages are prioritized when an imminent danger or abnormal situation is detected on the road. Then in second module, the channel load threshold is assigned dynamically based on beaconing load and transmit power properties which results a satisfaction level of maximum load beaconing. As a result, it alleviates congestion problems and improves bandwidth usage in VANETs. Experimental results on different data-sets including various vehicle densities, distances and road maps with and without obstacles (e.g. walls and buildings) show that the proposed method outperforms existing methods in terms of the average delivery ratio, message reception probability and average delay of time. Moreover, the results prove that the performance of all approaches degraded significantly in realistic scenarios (i.e. scenario with obstacles) compared to unrealistic scenario (i.e. scenario without obstacles) due to wireless signal attenuation and absorption.

A scalable data dissemination protocol for both highway and urban vehicular environments

Vehicular ad hoc networks (VANETs) enable the timely broadcast dissemination of event-driven messages to interested vehicles. Especially when dealing with broadcast communication, data dissemination protocols must achieve a high degree of scalability due to frequent deviations in the network density. In dense networks, suppression techniques are designed to prevent the so-called broadcast storm problem. In sparse networks, protocols incorporate store-carry-forward mechanisms to take advantage of the mobility of vehicles to store and relay messages until a new opportunity for dissemination emerges. Despite numerous efforts, most related works focus on either highway or urban scenarios, but not both. Highways are mostly addressed with a single directional dissemination. For urban scenarios, protocols mostly concentrate on either using infrastructure or developing methods for selecting vehicles to perform the store-carry-forward task. In both cases, dense networks are dealt with suppression techniques that are not optimal for multi-directional dissemination. To fill this gap, we present an infrastructure-less protocol that combines a generalized time slot scheme based on directional sectors and a store-carry-forward algorithm to support multi-directional data dissemination. By means of simulations, we show that our protocol scales properly in various network densities in both realistic highway and urban scenarios. Most importantly, it outperforms state-of-the-art protocols in terms of delivery ratio, end-to-end delay, and number of transmissions. Compared to these solutions, our protocol presents up to seven times lower number of transmissions in dense highway scenarios.