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With the rapid development of society, the improvement of material level and the current situation of the large-scale population flow in China, the awareness of security is becoming more and more important in people’s life. With the rapid development of image processing and computer vision technology, people try to analyze, process and understand the collected video image automatically without human intervention. The intelligent video monitoring system collects video signals of interested objects in a dynamic scene through a camera, and processes and analyzes image information by a computer. Only by establishing a reasonable and effective urban video monitoring management system can government departments find out problems in the first time. The traditional highway monitoring and commanding traffic scheduling system based on GIS, which can obtain road traffic information and conduct traffic scheduling by remote sensing, has the disadvantage of poor effect on traffic scheduling. In this paper, real-time communication technology and computer vision acquisition technology are used to build a city monitoring system. The experimental results show that this method has strong timeliness and good monitoring effect. Compared with the state-of-the-art methodologies, the proposed framework is efficient and accurate.

With a high frame-rate and high bit-rate, ultra-high definition (UHD) real-time communication (RTC) users could sometimes suffer from severe service degradation. Due to the fluctuations of frames incoming and decoding at the client side, a decoder queue could be formulated before the streaming decoder at the client side. Those fluctuations could easily overload the decoder queue and introduce a noticeable delay for those queued frames. In this paper, we propose a Frame-Skipping mechanism to effectively reduce the queuing delay by actively managing the frames inside the decoder queue. We jointly optimize the frames with skipping to maintain the end-to-end delay while ensuring the decoding quality of video codec. We also mathematically quantify the potential performance with a Markovian chain. We evaluate the Frame-Skipping mechanism with our trace-driven simulation with real word UHD RTC traces. Our experiments demonstrate that Frame-Skipping can reduce the ratio of severe decoder queue delay by up to 23x and the ratio of severe total delay by up to 2.6x.

Many wearable applications utilize wireless communication to provide the user with comfort features. With a typically rather small consumer market using technologies in the ISM band is beneficial in order to be cost effective. Safety relevant wearable applications, such as a wireless airbag jacket, face the challenge of providing real-time communication in noisy and volatile environments. In this evaluation we analyze different Wireless Body Area Network (WBAN) technologies with respect to their performance for real-time applications in mobile scenarios. The well established approach of using frequency diversity for increased reliability in noisy environments is evaluated for mobile scenarios.

We present the SphericRTC system for real-time 360-degree video communication. 360-degree video allows the viewer to observe the environment in any direction from the camera location. This more-immersive streaming experience allows users to more-efficiently exchange information and can be beneficial in the real-time setting. Our system applies a novel approach to select representations of 360-degree frames to allow efficient, content-adaptive delivery. The system performs joint content and bitrate adaptation in real-time by offloading expensive transformation operations to the GPU via CUDA. The system demonstrates that the multiple sub-components -- viewport feedback, representation selection, and joint content and bitrate adaptation -- can be effectively integrated within a single framework. Compared to a baseline implementation, views in SphericRTC have consistently higher visual quality. The median Viewport-PSNR of such views is 2.25 dB higher than views in the baseline system.

In the proposed system, a strategy for the control of energy consumption by home appliances is provided. The statistics of previous energy production and consumption of a case study city are used in providing the strategy. In the design of the proposed system, home appliances are categorized into three levels of priority, even though it can be more than three. In this article the control of energy consumption is achieved using a real time energy consumption manager (ECM) based on stored data without the need for real time communication. The system which is proposed here is affordable and simple. Also, it does not require grid upgrade or power line communication through the grid.

Smart meter is solid state device based instrument that collect electricity consumption to monitor real time electricity consumption means hour to hour or less and communicates the data at least daily, back to the utility for monitor, control and billing purpose. Smart meter is a digital electronic meter which provides real time communication which means any mode of telecommunication in which all users can exchange information instantly or with negligible response time between the consumer and the utility which makes complete system profitable. Complication such as calculation of meter reading and billing, demand requirement, cheating, unauthorized connection etc. can be cleared up through smart metering. This paper proposes the design and fabrication of smart meter. The overall consumption of any consumer which is real time data communicates to smart meter via radio frequency link. In house display system, which requires confirmation to interact with smart meter also offers consumer to set consumption limit with SMS alerts and turn ON/OFF the supply of electric energy. The whole consumption details of each appliance are also sent to utility with consumption date and time via SMS for billing purpose. The utility also has access to the smart meter for power cut off in case of bills not being paid.

For the purpose of keeping a plasma in steady state and avoiding instabilities, the experimental advanced superconducting tokamak (EAST) plasma control system (PCS) needs more diagnostic data produced by the EAST distributed subsystems to perform its complex control algorithms. To solve the transmission problem of all these data, a real-time communication system based on the messaging, real time, and grid real time operating system and reflective memory (RFM) network is designed. It is expected to enable the data acquisition (DAQ) systems of various EAST subsystems to be able to transfer the diagnostic data to the PCS in real time through the RFM network as the data are acquired. Then, the PCS can use these available data to carry out the necessary calculations according to the control algorithms and send the commands to the subsystems in every control cycle. To reach this goal, a small real-time communication system, adapted from the prototype of the EAST vacuum DAQ system (sampling rate of 10 KHz), was built for a performance test. In this test, the vacuum DAQ system transferred the acquired data to the PCS within the control cycle of $100~\mu \text{s}$ , which tentatively meets the abovementioned requirements. The test was performed for 1000 s to get a stable and reliable result, which is described in detail in this paper as well as plans for future work.

Applications requiring real-time communication (RTC) between Internet peers are ever increasing. RTC requires not only congestion control but also minimization of queuing delays to provide interactivity. It is known that the well-established transmission control protocol congestion control is not suitable for RTC due to its retransmissions and in-order delivery mechanisms, which induce significant latency. In this paper, we propose a novel congestion control algorithm for RTC, which is based on the main idea of estimating—using a Kalman Filter—the end-to-end one-way delay variation which is experienced by packets traveling from a sender to a destination. This estimate is compared with a dynamic threshold and drives the dynamics of a controller located at the receiver, which aims at maintaining queuing delays low, while a loss-based controller located at the sender acts when losses are detected. The proposed congestion control algorithm has been adopted by Google Chrome. Extensive experimental evaluations have shown that the algorithm contains queuing delays while providing intra and inter protocol fairness along with full link utilization.

While web applications continue to employ traditional client-server model, most of the current applications demand real time bi-directional communication. In such setups, data exchanges between both the parties (client and server) are very frequent. Thus, performance of the network is subject to various factors decided by the choice of data exchange mechanism. This shows that the choice of data exchange mechanism is vital to performance of a web-application employing it. This paper compares various data exchange mechanisms with respect to factors affecting real time web applications. While the absolute values of benchmarking may vary with the systems, the relative difference between them can be used as a reference for selecting a mechanism for an application. Hence, this paper can be used as a reference to choose appropriate data exchange mechanism for the concerned application.

High-performance embedded systems running real-time applications demand communication solutions providing high data rates and low error probabilities, properties inherent to optical solutions. However, providing timing guarantees for deadline bound applications in this context is far from basic due to the parallelism inherent in multiwavelength networks and often bound to include a large amount of pessimism. Assuming deterministic medium access, an admission control algorithm using a schedulability analysis can ensure deadline guarantees for real-time communication. The traffic dependency analysis presented in this paper is specifically targeting a multichannel context, taking into consideration the possibility of concurrent transmissions in these types of networks. Combining our analysis with a feasibility analysis in admission control, the amount of guaranteed hard real-time traffic could be shown to increase by a factor 7 in a network designed for a radar signal processing case. Using this combination of analysis methods will render possible an increased amount of hard real-time traffic over a given multichannel network, leading to a more efficient bandwidth utilization by deadline dependent applications without having to redesign the network or the medium access method.

Generally, Pollution estimations are performed utilizing costly hardware at settled areas or committed portable hardware research centers. This is a coarse-grained and costly approach to estimate pollution. In this paper, we present a portable approach for estimating fine-grained air quality continuously. We propose practical information acquisition model for indoor and outdoor air quality monitoring which can be carried anywhere as a portable device. It consists of gas detection circuitry for CO, CO2, PM2.5, PM10 and humidity sensor. Array of gas sensors are connected to microcontroller after signal conditioning circuit. This data is sent to a cloud service platform which provides facility of accessing the data in the form of real-time graph. An android app has been developed for the easy access of the air quality data on mobile phones. Data can be collected from many such Active Queue Management (AQM) blocks. We present fundamental models and examine its execution challenges.

In this paper, the Beidou high-precision positioning technology, the autonomous inspection technology of the UAV and the communication technology of the UAV are used to construct the inspection architecture of the UAV autonomous inspection. The inspection architecture includes UAV inspection path standard planning and acquisition verification, UAV autonomous flight control system, UAV and application platform communication control, UAV inspection results identification and management. Based on high-precision positioning technology, we designed the architecture of the UAV autonomous inspection system, the UAV autonomous inspection security strategy and transaction processing mechanism, the UAV’s real-time video and position transmission system. Then we successfully developed the UAV Autonomous inspection system. After testing, based on high-precision positioning technology, the accuracy of the UAV autonomous inspection repeat flight can reach 5cm (EW), 6cm (NS), 7cm (H), and the stop point heading angle is 56″ on average, which can indicate that under the guarantee of this system, the UAV can carry an important role in inspection work safely and effectively.

The problem of fingerprint-based attendance management has been overcome in previous studies. Web Service Implementation (WS) has successfully handled fingerprint machine communication with a web-based monitoring system with a different platform. However, it is not yet known the size of the data transfer rate between the fingerprint machine and the monitoring system. The primary purpose of this research is to test and measure data transfer speed and memory usage. Experiments in this study were carried out by connecting five fingerprint machines with a web-based monitoring system. Node.js is installed on the server-side that is connected to the web service and database. The experiment is repeated; the data transfer speed and memory usage are recorded in the table and averages are calculated. The experimental results in the study showed that after 50 trials it was known that the average time of data transfer was 14.53 ms and the average memory usage was 17.42 Mb. So that communication between fingerprint machines and web-based monitoring systems can be categorized as real-time communication.

The Unified Vehicular Volume Reduction Program was implemented to reduce the number of cars in a particular area as to lessen traffic congestions by restricting cars depending on the day with the corresponding last digit of the vehicle's plate number. The purpose of this study is to reinforce and automate the detection of violators of the vehicular volume reduction using a cloud based detection and real-time communication of number coding violators through character recognition and image processing. With the use of a Raspberry Pi, a web camera, and a monitor, the research aims to create a cost-effective number coding violation detector that can notify the violator as well as keep the logs in a database storage.

Wireless sensor networks have found their way into a wide range of applications, among which environmental monitoring systems have attracted increasing interests of researchers. Main challenges for these applications are scalability of the network size and energy efficiency of the spatially distributed nodes. Nodes are mostly battery-powered and spend most of their energy budget on the radio transceiver module. In normal operation modes most energy is spent waiting for incoming frames. A so-called Wake-On-Radio (WOR) technology helps to optimize trade-offs between energy consumption, communication range, complexity of the implementation and response time. We already proposed a new protocol called SmartMAC that makes use of such WOR technology. Furthermore, it gives the possibility to balance the energy consumption between sender and receiver nodes depending on the use case. Based on several calculations and simulations, it was predicted that the SmartMAC protocol was significantly more efficient than other schemes being proposed in recent publications, while preserving a certain backward compatibility with standard IEEE802.15.4 transceivers. To verify this prediction, we implemented the SmartMAC protocol for a given hardware platform. This paper compares the realtime performance of the SmartMAC protocol against simulation results, and proves the measured values are very close to the estimated values. Thus we believe that the proposed MAC algorithms outperforms all other Wake-on-Radio MACs.

According to the existing problems in the supervision of on-site operation of electrical power system, an on-site operation monitoring and command system is designed. The on-site video is transmitted to command center via servicer by wireless network. But due to the instability of wireless network bandwidth, the real-time transmission of video can’ t be guaranteed. Even the transmission delay is long and the frames are lost seriously. In order to make the video transmission real-time and integrity, a video optimal transmission method based on the frame similarity is proposed. On the basis of the characteristics of H.264 video coding mode, the frame similarity parameter is marked to distinguish the frame importance. The network bandwidth changes is monitored in real time and the Prio-Drop scheduling algorithm is presented, so the important frames can be transmitted in advance. The test indicates that the optimal transmission method can improve the decoding quality of transmitted video, and achieve the requirements of real-time video transmission, which provided the technical guidance for enhancing the power supervision and strengthening emergency command.

This paper presents a novel method to communicate necessary data between the users of Plug-in-Hybrid Electric Vehicles (PHEVs) and the DC fast charging stations. PHEVs are getting promoted around the world for multiple reasons. DC fast charging stations can act as a catalyst to the success of such promotions. Proper deployment of renewable based DC fast charging stations with smart communication facilities with the users can encourage the wide use of PHEVs. The exchange of various information include state of charge (SoC) of PHEV batteries, location of nearest charging station and crowd level at the charging stations are employed in this work. The proposed scheme utilizes global system for mobile (GSM) technology, global positioning system (GPS) and a dedicated website to provide the real time information through a website link given to the user.

Based on phasor measurement units (PMUs), a synchronphasor system is widely recognized as a promising smart grid measurement system. It is able to provide high-frequency, high-accuracy phasor measurements sampling for Wide Area Monitoring and Control (WAMC) applications. However, the high sampling frequency of measurement data under strict latency constraints introduces new challenges for real time communication. It would be very helpful if the collected data can be prioritized according to its importance such that the existing quality of service (QoS) mechanisms in the communication networks can be leveraged. To achieve this goal, certain anomaly detection functions should be conducted by the PMUs. Inspired by the recent emerging edge-fog-cloud computing hierarchical architecture, which allows computing tasks to be conducted at the network edge, a novel PMU fog is proposed in this paper. Two anomaly detection approaches, Singular Spectrum Analysis (SSA) and K-Nearest Neighbors (KNN), are evaluated in the PMU fog using the IEEE 16-machine 68-bus system. The simulation experiments based on Riverbed Modeler demonstrate that the proposed PMU fog can effectively reduce the data flow end-to-end (ETE) delay without sacrificing data completeness., Comment: presented at the 2nd IEEE International Conference on Fog and Edge Computing (ICFEC 2018), Washington DC, USA, May 1, 2018

The metrology field has been progressed with the appearance of the wireless intelligent sensor systems providing more capabilities such as signal processing, remote multi-sensing fusion etc. This kind of devices is rapidly making their way into medical and industrial monitoring, collision avoidance, traffic control, automotive and others applications. However, numerous design challenges for wireless intelligent sensors systems are imposed to overcome the physical limitations in data traffic, such as system noise, real time communication, signal attenuation, response dynamics, power consumption, and effective conversion rates etc, especially for applications requiring specific performances. This paper analyzes the performance metrics of the mentioned sensing devices systems which stands for superior measurement, more accuracy and reliability. Study findings prescribe researchers, developers/ engineers and users to realizing an optimal sensing motes design strategy that offers operational advantages which can offer cost-effective solutions for an application., Comment: 10 pages, 14 figures, 7 tables, journal research paper. arXiv admin note: substantial text overlap with arXiv:1409.6884

The IEEE Time-sensitive Networking (TSN) Task Group has recently standardized enhancements for IEEE 802.3 networks for enabling it to transport time-triggered traffic (aka scheduled traffic) providing them with stringent bounds on network delay and jitter while also transporting best-effort traffic. These enhancements primarily include dedicating one queue per port of the switch for scheduled traffic along with a programmable gating mechanism that dictates which of the queues are to be considered for transmission. While the IEEE 802.1Qbv standards define these mechanisms to handle scheduled traffic, it stops short of specifying algorithms to compute fine-grained link schedules for the streams of scheduled traffic. Further, the mechanisms in TSN require creation of so-called guard bands to isolate scheduled traffic from the best-effort traffic. These guard bands may potentially result in bandwidth wastage, and hence schedules with lower number of guard bands are preferred. In this paper, we introduce the No-wait Packet Scheduling Problem (NW-PSP) for modelling the scheduling in IEEE Time-sensitive Networks and map it to the No-wait Job-shop Scheduling Problem (NW-JSP), a well-known problem from the field of operational research. In particular, we present a Tabu search algorithm for efficient computing of schedules and a schedule compression technique to reduce number of guard bands in schedule. Our evaluations show that our Tabu search algorithm can compute near-optimal schedules for over 1500 flows and the subsequent schedule compression reduces the number of guard bands on an average by 24%.

Video conferencing applications require low latency and high bandwidth. Standard TCP is not suitable for video conferencing since its reliability and in order delivery mechanisms induce large latency. Recently the idea of using the delay gradient to infer congestion is appearing again and is gaining momentum. In this paper we present an algorithm that is based on estimating through a Kalman filter the end-to-end one way delay variation which is experienced by packets traveling from a sender to a destination. This estimate is compared to an adaptive threshold to dynamically throttle the sending rate. The control algorithm has been implemented over the RTP/RTCP protocol and is currently used in Google Hangouts and in the Chrome WebRTC stack. Experiments have been carried out to evaluate the algorithm performance in the case of variable link capacity, presence of heterogeneous or homogeneous concurrent traffic, and backward path traffic.

Communication networks to support space missions were originally architected around non-real time data services. In fact, missions have always required real-time services (e.g. telemetry and command), but the bulk of scientific data being returned to Earth has typically been highly delay tolerant. Nevertheless, future robotic and human exploration activities are rapidly pushing towards low latency, high data rate services. Examples can be found both in the near Earth domain (e.g. near real-imagery through NASAs LANCE program) and the deep space domain (e.g. HD video from Mars). Therefore, the goal of this paper is to quantify the effect of new real-time high data rate communication requirements on the ground segment of current communication networks. To that end, we start by analyzing operational schedules for NASAs Space Network (SN) in order to characterize the utilization of the overall network in terms of total data volume and contact time, as well as identify current mission drivers. These results are compared against proposed network requirements for future robotic and human near Earth exploration activities in order to quantitatively assess gaps in the SN capabilities. Using these results, we implement a rule-based expert system that translates SN-specific operational contacts into high-level data requirements for the ground segment of the network. We then exercise the expert system in order to derive the requirements that future exploration activities will impose on the SN. Finally quantify the impact of real-time data delivery services across NASAs ground segment by computing the wide-area network cost for different levels of data timeliness.

In this paper, the real-time EtherCAT technology is introduced in detail, which including operating principle, communication protocol and the superiority performance of EtherCAT i.e. synchronicity, simultaneousness and high speed. To show how to design a slave system that considering the characteristics of application, the method of developing systems based no EtherCAT technology are proposed. Finally, a data acquisition system based on EtherCAT technology is designed. Application of EtherCAT technology can improve the real-time characteristics of data communication in wind power system.

The international standard, ISO-11783, was designed for the communication within an agriculture machinery. Even if it is based on the CAN (Control Area Network) protocol, its extended features which include point-to-point communication and large data transmission support show different network performance from the standard CAN. This paper proposes a dynamic priority allocation method to improve the real-time performance of ISO-11783. Computer simulation shows reduction of the deadline-missed cases and community latency via proposed algorithm.

The paper presents an investigation into wireless sensor networks (WSNs) for cattle monitoring. The proposed solution fulfils the requirement for intensive condition monitoring of individual animals, aggregation and timely reporting of data to the farm manager. The core contribution of this study is a wireless communication solution designed for both loose house dairy cattle and free ranging beef cattle. The design target utilises inexpensive, low power consumption sensor nodes as the base elements of a data gathering and communication infrastructure. This platform facilitates real-time data download for loose housed dairy cattle and non real-time communication for free ranging beef cattle where the former is more challenging. In order to meet the target objectives, both the hardware and software are designed to adapt to the deployment challenges which include mobility, radio path interference, short transmission range of sensor nodes and limited resources in terms of energy and storage. These challenges have been analysed and addressed. Laboratory experiments and farm trials have been carried out to evaluate the performance of the platform communication protocol. The results of experiments demonstrate that the platform performs efficiently while conforming to the limitations associated with WSN implementations.

As many radio chips used in today’s sensor mote hardware can work at different frequencies, several multichannel communication protocols have recently been proposed to improve network throughput and reduce packet loss for wireless sensor networks. However, existing work cannot utilize multiple channels to provide explicit guarantees for application-specified end-to-end communication delays, which are critical to many real-time applications such as surveillance and disaster response. In this article, we propose MCRT, a multichannel real-time communication protocol that features a flow-based channel allocation strategy. Because of the small number of orthogonal channels available in current mote hardware, MCRT allocates channels to network partitions formed based on many-to-one data flows. To achieve bounded end-to-end communication delay for every data flow, the channel allocation problem has been formulated as a constrained optimization problem and proven to be NP-complete. We then present the design of MCRT, which includes a channel allocation algorithm and a real-time packet forwarding strategy. Extensive simulation results based on a realistic radio model and empirical results on a real hardware testbed of Tmote nodes both demonstrate that MCRT can effectively utilize multiple channels to reduce the number of deadlines missed in end-to-end communications. Our results also show that MCRT outperforms a state-of-the-art real-time protocol and two baseline multichannel communication schemes.

Priority-based wormhole switching with a priority share policy has been proposed as a possible solution for real-time on-chip communication. However, the blocking introduced by priority share complicates the analysis process. In this paper, we propose a new "per-priority" basis analysis scheme which computes the total time window at each priority level instead of each traffic-flow. By checking the release instance of each flow at the corresponding priority window, we can determine schedulability efficiently. Building on this static analysis, for a given set of tasks and network topology, we further propose a task mapping and priority assignment algorithm, in such a way that the hard time bounds are met with a reduced hardware overhead. Experiment results show that significant resource saving can be achieved with no performance degradation in terms of missed deadlines. By using this approach, a broad class of real-time communications with different QoS requirements can be explored and developed in a SoC/NoC communication platform.

Synchronous bandwidth, defined as the maximum time a node is allowed to send its synchronous messages while holding the token, is a sensitive parameter for deadline guarantees of synchronous messages in any timed token network. In order to offer such guarantees, synchronous bandwidth has to be allocated carefully to each individual node. This paper studies the synchronous bandwidth allocated to those synchronous message streams whose deadlines are less than twice the Target Token Rotation Time (TTRT). A new approach for allocating synchronous bandwidth to such streams, which can be used with any previously published local synchronous bandwidth allocation (SBA) for guaranteeing a general synchronous message set with its minimum deadline (D"m"i"n) no less than 2.TTRT, is proposed. The proposed scheme can be applied efficiently in practice to any general synchronous message set with D"m"i"n>TTRT. Numerical examples are presented to demonstrate the enhanced performance of this new local scheme over any of the previously published local SBA schemes.

Video conferencing applications have significantly changed the way people communicate over the Internet. Web Real-Time Communication (WebRTC), drafted by the World Wide Web Consortium (W3C) and Internet Engineering Task Force (IETF) working groups, has added new functionality to the web browsers, allowing audio/video calls between browsers without the need to install any video telephony applications. The Google Congestion Control (GCC) algorithm has been proposed as WebRTC's congestion control mechanism, but its performance is limited due to using a fixed incoming rate decrease factor, known as alpha (a). In this paper, we propose a dynamic alpha model to reduce the available receiving bandwidth estimate during overuse as indicated by the over-use detector. Experiments using our specific testbed show that our proposed model achieves a 33% higher incoming rate and a 16% lower round-trip time, while keeping a similar packet loss rate and video quality, compared to a fixed alpha model.

This paper investigates a real-time communication platform for a Smart Grid adaptive Volt-VAR Optimization (VVO) engine. Novel VVO techniques receive inputs from Advanced Metering Infrastructure (AMI) to dynamically optimize distribution networks. As communication platform design and characteristics affect Smart Grid-based VVO performance in terms of control accuracy and response time, VVO ICT studies is essential for grid planners and/or power utilities. Hence, this paper primarily introduces a real-time co-simulated environment comprised of Smart Grid adaptive VVO engine, RTDS model and system communication platform using DNP3 protocol. This platform is built to test and asses the influence of different components included in Smart Grid monitoring and control system; namely the sensors, measurement units, communication infrastructure on the operation and control of VVO. Moreover, this paper uses a real-time platform to check the robustness of the monitoring and control applications for communication network considerations such as delays and packet loss. Next, this paper investigates how such a platform could look into communication issues while taking system requirements into consideration. A 33-node distribution feeder is employed to check system performance through communication parameters such as throughput and response time.

Networked Control System Laboratory(NCSLab) 3D is built on the basis of NCSLab which is a platform to carry out real-time control system experiments through the Internet and has been developed into a 3D version for conducting virtual experiments for now. To experiment with models in NCSLab 3D, the communication between the NetCon which is an algorithm simulator and the server as well as that between the server and the Web client is a key issue which needs to be addressed in the first place. This paper proposes a real-time communication method which can adapt the parameter to make the data transmission in the receiver synchronous with that in the sender. Thus, annoying problems such as the long time delay or data loss can be to a large extent avoided and real-time virtual experiment can be guaranteed. The one capacity water tank is taken as an example to verify the method and the result shows a good real-time performance.

This paper proposes a generic communication system, which is controlled by a formalized process model. This system architecture is instantiated for the public transport domain. The operation of this system combines a distributed work-flow model (Business Process Modell and Notation, BPMN) with open communication standards incorporating real time communication (RTC) characteristics as provided by e.g. LTE mobile IP networks. The performed formalization meets the requirements of a typical scenario in public transport: connection protection. The participants involved are represented by the control center, along with the mobile and distributed users: drivers and passengers. Formalization with BPMN allows the modelling and understanding of the various interactions and communications between the different agents. For public transport operators the approach set out in this paper leads to a considerable economic advantage. Passengers benefit from improved customer experience in seamless travel across different modes of transportation

This paper presents a novel control algorithm to decrease the worst-case delay bound for high rate homogeneous and heterogeneous real-time flows when the network traffic load becomes heavy. The algorithm is adaptive based on the instantaneous network situations. It employs a generalized form of traditional (σ,ρ) regulator called the generalized (σ,ρ,λ) regulator that operates like the (σ,ρ) regulator under the normal network traffic load situation, but provides more regulations for the heavy network traffic load situation. For a set of real-time flows, we can show that Drg≤Dg where Drg and Dg are the worst-case delay bounds with the (σ,ρ,λ) regulator and the (σ,ρ) regulator respectively. More specifically, we have developed a set of formulas to set the parameters for the new regulator so as to reduce the worst-case delay bounds for the real-time flows. We can prove that there exists a threshold input rate ρ* such that Drg = Dg for ρ≤ρ* and Drg ρ*. When the average input rate of real-time flows is very high, the generalized regulator can effectively control the delay. The extensive experiment data match our theoretical results.

Due to the low price and robustness resulting from its wide acceptance and deployment, Ethernet has become an attractive candidate for real-time control networks. However, it is difficult to build a real-time control network using the standard Ethernet because the Ethernet MAC protocol-1-persistent CSMA/CD protocol-may cause unpredictable access delay. When both real-time and nonreal-time packets are concurrently transported over an ordinary Ethernet, real-time (RT) packets from a node may experience a large delay due to 1) contention with nonRT packets in the local node where they originate and 2) collision with RT and nonRT packets from the other nodes. To resolve this problem, we design, implement, and evaluate an adaptive traffic smoother. Specifically, we design two adaptive traffic smoothers, one at the kernel level and the other at the user level. The kernel-level traffic smoother is installed between the IP layer and the Ethernet MAC layer for better performance, and the user-level traffic smoother is installed on top of the transport layer for better portability. The kernel-level traffic smoother first gives RT packets priority over nonRT packets in order to eliminate contention within the local node. Second, it smoothes nonRT traffic so as to reduce collision with RT packets from the other nodes. This traffic smoothing can dramatically decrease the packet-collision probability on the network. The traffic smoother, installed at each node, regulates the node's outgoing nonRT traffic to maintain a certain rate. In order to provide a reasonable nonRT throughput while providing probabilistic delay guarantees for RT traffic, the nonRT traffic-generation rate is allowed to adapt itself to the underlying network load condition. Our implementation of the traffic smoother requires only a minimal change in the OS kernel without any modification to the current standard of Ethernet MAC protocol or the TCP or UDP/IP stack. The traffic smoother has been implemented on the Linux OS and is shown to reduce the RT message deadline-miss ratio up to two orders of magnitude under a heavily loaded condition, while the nonRT throughput drops only by half. For better portability, we also implemented and evaluated a user-level traffic smoother on top of the transport layer. Moreover, we emulate a switch using a kernel-level traffic smoother to evaluate the performance of traffic smoother in a switched Ethernet environment that can scale to a large control network.

The presentation of packet-level communication network performance data to a user in an easy to assimilate, visual form by computer screen is considered. Standard presentation mechanisms such as bar graphs and numeric (text) displays require considerable concentration on behalf of the operator if more than a very small number of measurement values are presented. However, for many network operation tasks the initial requirement is for the relative value of the measurements and any trends in these measurements to be readily identifiable. A different approach to measurement presentation has therefore been considered whereby an object's shape is distorted in proportion to the values of a set of measurement data. A casual viewing of the object therefore immediately indicates the relative values of the measurements. This approach has been applied to the presentation of packet delay values for a commercially operational network, and its use in a performance measurement system for the commercial communication network is described.

In IEEE 802.12 network, a repeater arbitrates among transmission requests on a round robin basis. A node can transmit a packet only when it is granted by the repeater. Recently, the IEEE 802.12 Committee approved a burst mode in which a node can transmit multiple packets per grant. In burst mode a bandwidth, or the number of packets per grant should be allocated taking into account the timing constraints of real-time messages. This paper proposes bandwidth allocation algorithms based on the burst mode to guarantee the deadlines of periodic real-time messages. Once the bandwidth of each node is derived from the lengths and deadlines of periodic messages, a node is allowed to transmit packets up to the allocated bandwidth per grant. Experimental results show that the proposed algorithms providemuch higher guarantee ratio and graceful degradation for heavy network load, compared with the existing approaches.