Real-time Communication Protocol Research Articles

An adaptive MAC protocol for real-time and reliable communications in medical cyber-physical systems

With the increasing demands for high-quality health-care services, medical cyber-physical systems over wireless body sensor networks have emerged as a promising solution for vital life signals monitoring. These systems require the communication protocols to be both reliable and real-time in data transmissions. IEEE 802.15.4 can be regarded as the canonical protocols in this area owing to its low-power and low-cost features. However, it falls short of reliability and timeliness guarantees. To address this issue, we propose an adaptive MAC protocol based on IEEE 802.15.4, namely Ada-MAC. The proposed protocol combines schedule-based on time-triggered protocol and contention-based CSMA/CA mechanism. It can not only enable dynamic Guaranteed Time Slots allocation but also provide differentiated services for different nodes according to their data types. The proposed protocol is implemented on the OMNeT++ platform. Extensive simulations are conducted to evaluate the performance of Ada-MAC in comparison with the traditional IEEE 802.15.4 MAC. The results show the superiority of the proposed protocol in terms of reliability and timeliness.

The Cross-Browser Multi-Platform Real Time Online Monitoring System Based on WebSocket

The traditional HTTP protocol uses the request、response mode, and it does not support the characteristics such as real-time information transmission and server push. In this paper, the use of HTM5 in the WebSocket protocol supports long connection, full duplex communication and other characteristics, and the design of a new set of real-time online monitoring system has been made, not only solve the efficiency problem of implementation of Web real time communication protocol HTTP polling and other technology, but also ensure cross browser system of multi platform characteristics.

RTXP: A localized real-time MAC-routing protocol for wireless sensor networks

Protocols developed during the last years for Wireless Sensor Networks (WSNs) are mainly focused on energy efficiency and autonomous mechanisms (e.g. self-organization, self-configuration, etc.). Nevertheless, with new WSN applications, new QoS requirements appear, such as time constraints. Real-time applications require the packets to be delivered before a known time bound which depends on the application requirements. We particularly focus on applications which consist in alarms sent to the sink node. We propose Real-Time X-layer Protocol (RTXP), a real-time communication protocol. RTXP is a MAC and routing real-time communication protocol that is not centralized, but instead relies only on local information. To the best of our knowledge, it is the first real-time protocol for WSNs using an opportunistic routing scheme in order to increase the packet delivery ratio. In this paper we describe the protocol mechanisms. We give theoretical bounds on the end-to-end delay and the capacity of the protocol. Intensive simulation results confirm the theoretical predictions and allow to compare RTXP with a real-time scheduled solution. RTXP is also simulated under harsh radio channel, in this case, the radio link introduces probabilistic behavior. Nevertheless, we show that RTXP performs better than a non-deterministic solution. It thus advocates for the usefulness of designing real-time (deterministic) protocols even for highly unreliable networks such as WSNs.

On design and formal verification of SNSP: a novel real-time communication protocol for safety-critical applications

The correct operation of time-triggered protocols highly depends on the well-synchronized clocks of the system. To maintain the global time, one strict constraint must be exerted on communication activities (e.g. temporal padding and sparse time base etc.), which not only increases complexity of the protocol design but also incurs a penalty in the network utilization. While for event-triggered protocols, it is difficult to achieve the real-time requirement and determinism. Therefore, it is necessary to explore the combination of the advantages of these two categories of protocol for applications in different scenarios. This paper proposes the Safe Node Sequence Protocol (SNSP), which is a variant of full time-triggered protocol TTP/C. In SNSP, a strict node sequence is defined and the order of communication events is established by this pre-configured order without binding to global time, so the protocol changes communication activities and error detection to an event-triggered model. Therefore, SNSP possesses the characteristics of both time-triggered and event-triggered model. Also, the potential impact of global time, such as byzantine clock failure, on the protocol is eliminated. At the same time, the formal verification of SNSP is much easier in the absence of global time. Moreover, we model the protocol and use formal checker SPIN to validate the basic fault-tolerant requirement of SNSP. The simulation results show the protocol enables better resource utilization and is more effective.

Multi-Velocity Energy-Efficient Reliable Routing Protocol for Coal Mine Monitoring

sensor network has been used in many real-time applications that require reliable and timely delivery of data. This paper presents a real-time communication protocol with data recovery at each hop level to guarantee reliability and also uses the latency of link to determine the shortest path and promises speedy delivery for wireless sensor networks. The proposed protocol provides services such as route discovery based on the reaching speed of the node, multipath forwarding using required reliability and data recovery in single hop. Simulation result shows that the proposed protocol significantly improves the effective capacity of a sensor network in terms of reliability and quickness. Moreover the protocol is highly responsive to the various error conditions experienced and adaptive to large-scale dynamic sensor networks. KeywordsSensor Networks, QoS, multispeed, reliable routing, energy efficiency

R2P: An open source hardware and software modular approach to robot prototyping

Rapid prototyping is a key aspect for the development of innovative robotic applications. A modular, platform-based, approach is the way to obtain this result. Modular approaches are common for software development, but hardware is still crafted often re-inventing solutions every time. As a consequence, the resources that should be invested in the development of a new robot get often drained by the implementation of a physical, working prototype to test the application idea. To overcome this problem, we propose R2P (Rapid Robot Prototyping), a framework to implement real-time, high-quality architectures for robotic systems with off-the-shelf basic modules (e.g., sensors, actuators, and controllers), integrating hardware and software, which can be assembled in a plug-and-play way. R2P provides hardware modules, a protocol for real-time communication, a middleware to connect components as well as tools to support the development of software on the modules. R2P aims at dramatically reduce time and efforts required to build a prototype robot, making it possible to focus the resources on the development of new robotic applications instead of struggling on their implementation. This enables also people with experience in a specific application domain, but with little technical background, to actively participate in the development of new robotic applications. R2P is open-source both in its software and hardware to promote its diffusion among the robotics community and novel business models that will substantially reduce the costs to design a new robotic product.

Research on IEC 61850 Gateway Based on MMS Mapping

IEC 61850 is an international standard developed by the International Electrotechnical Commission TC57 substation automation communication networks and systems. It uses MMS (Manufacturing Message Specification) as a real-time communication protocol of the application layer, and achieves the communication between the substation layer and the spacer layer. This paper describes the features and functions of the IEC 61850 and MMS technology and focuses on the principle of MMS mapping in the application of IEC 61850 , then preliminarily leads to the overall design framework of the IEC 61850 gateway.

LOARP: A Low Overhead Routing Protocol for Underwater Acoustic Sensor Networks

Underwater wireless communications among underwater sensor nodes enable a large number of scientific, environmental and military applications. For example, autonomous underwater vehicles will enable exploration of deep sea resources and gathering of scientific data for collaborative missions. In order to make underwater applications possible, real-time communication protocols among underwater devices must be enabled. Because of the high attenuation and scattering effect of radio and optical waves, respectively, these underwater devices are based on acoustic wireless technology. The unique characteristics of underwater acoustic channel - such as distance-dependent limited bandwidth and high propagation delays, require new, efficient and reliable communication protocols over multiple hops to network multiple devices which may be either static or mobile. This paper proposes a new low overhead ad hoc routing protocol designed for underwater acoustic sensor network. The protocol performs route discovery when needed in an on-demand manner. It also characterises a route maintenance phase which tries to recover a failed route. Detection of route failure can generate a lot of routing traffic. The proposed protocol tries to minimize this routing traffic by detecting failure in a more intelligent way either by monitoring network data traffic (if present) or generating lazy acknowledgements (if necessary). Reducing routing traffic minimizes the chance of packet collisions which in turn increases data packet delivery ratio. The performance of the proposed protocol is measured in terms of network throughput, packet delivery ratio, average endto-end delay and control overhead. The results are compared to those obtained using similar on-demand routing protocols. Simulation results show that the reduction of routing traffic can improve the performance of the network.

A Novel Routing Protocol that Guarantees Swiftness and Reliability for Wireless Sensor Network

sensor network has been used in many real-time applications that require reliable and timely delivery of data. This paper presents a real-time communication protocol with data recovery at each hop level to guarantee reliability and also uses the latency of link to determine the shortest path and promises speedy delivery for wireless sensor networks. The proposed protocol provides services such as route discovery based on the reaching speed of the node, multipath forwarding using required reliability and data recovery in single hop. Simulation result shows that the proposed protocol significantly improves the effective capacity of a sensor network in terms of reliability and quickness. Moreover the protocol is highly responsive to the various error conditions experienced and adaptive to large-scale dynamic sensor networks.

Building mobile multimedia services: a hybrid cloud computing approach

Mobile multimedia services are in high demand, but their development comes at high costs. The emergent computing paradigm cloud computing has great potential to embrace these issues. In fact, we are at the early stage of the coalescence of cloud computing, mobile multimedia and the Web. Motivated by the tremendous success story of the Web based on its simplicity principles, we argue for a comprehensive review on current practices of web and mobile multimedia cloud computing techniques for avoiding frictions. We draw on experience from the development of advanced collaborative multimedia web applications utilizing multimedia metadata standards like MPEG-7 and real-time communication protocols like XMPP. We propose our i5CLoud, a hybrid cloud architecture, which serves as a substrate for scalable and fast time-to-market mobile multimedia services. This paper demonstrates the applicability of emerging cloud computing concepts for mobile multimedia.

Evaluation of Vehicular Ad Hoc Networks on Safety Traffic

Vehicular Ad hoc NETworks in which no centralized static station or infrastructure are supported is gaining increasing popularity. Due to mobility, the topology of the networks changes continuously and wireless links break down and reorganize frequently. These features cause traditional real-time communication protocols to be inapplicable in a mobile setting. The increasing research of real-time communication in Mobile Ad hoc wireless NETworks (MANETs) is to enable distributed applications among mobile nodes in infrastructure-free environments. Vehicular Ad hoc NETworks (VANETs) characterized by nodes with relatively high mobility and various disturbed environments represent a number of remarkable challenge dissimilar to MANETs. Applications of inter-vehicle and vehicle-to-roadside wireless communication that make use of VANETs require reliable communication that provides a guarantee of real-time message propagation. Nowadays, most of researches in VANETs domain concentrate on the development of layered communication protocols.

MCRT

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.

Evaluating a new communication protocol for real-time distributed control

The recent trend in distributed automation and control systems has been towards event-triggered system architectures such as UML and IEC 61499. Although existing communication protocols (e.g., Ethernet) can support high-level communication within these systems, there is contention as to which low-level protocol to use, or if any exist that meet the requirements of being event-triggered and hard real-time. This paper proposes a new way to measure communication performance. The goal of the new measurement method is to stress the necessity that a real-time communication protocol needs to be both efficient and fair. This is illustrated by comparing three communication strategies: Controller Area Network (CAN), Time-Triggered CAN (TTCAN) and Escalating Priority CAN (EPCAN). The first two represent the extremes between event-triggered and time-triggered communication strategies; the third is introduced to illustrate the benefits of a new event-based communication protocol proposed by the authors.

MULTICAST CONGESTION CONTROL SRMSH APPROACH USING COMMUNICATING REAL-TIME STATE MACHINES

New real-time applications frequently involve timing constraints related to accurate services from communication protocols. Concretely, real-time communication protocols utilize timers to implement these constraints between system event occurrences. In this context, the study of congestion control for Internet reliable multicast is at present an active research field related to real-time protocols. In this paper, the authors present an innovative real-time transport protocol named Scalable Reliable Multicast Stair Hybrid (SRMSH) as new hybrid multiple layer mechanism for multicast congestion control providing detection and recovery loss. This work is focused on formal specification of SRMSH approach using Communicating Real-Time State Machines as a formal method. Besides, SRMSH validation is presented within a formal proof framework in order to check the functional safety and liveness properties. As a result, authors outline a dynamical system framework in order to model behavior of their presented solution.

Transport protocol for real-time communication in Wireless Sensor Networks

Wireless sensors need data that arrive in time. This demand is fulfilled by a real-time communication for applications that use WSN technologies. The protocols, TCP and UDP, were not designed for real-time communication in wireless networks. The proposed protocol can manage data unit delays by considering time and space evaluations. The protocol designed in this study is compared with the UDP protocol. Both protocols are compared for the data units travel times and for the timelyput, which is the throughput of data units which arrive in time and which can be used by the application. This novel protocol achieves better results.

A TLA+ Formal Specification and Verification of a New Real-Time Communication Protocol

We describe the formal specification and verification of a new fault-tolerant real-time communication protocol, called DoRiS , which is designed for supporting distributed real-time systems that use a shared high-bandwidth medium. Since such a kind of protocol is reasonably complex and requires high levels of confidence on both timing and safety properties, formal methods are useful. Indeed, the design of DoRiS was strongly based on formal methods, where the TLA+ language and its associated model-checker TLC were the supporting design tool. The protocol conception was improved by using information provided by its formal specification and verification. In the end, a precise and highly reliable protocol description is provided.

Design and Implementation of a Wireless Fieldbus for Plastic Machineries

Fieldbus systems are well known in the industrial automation world. Due to the increasing demand for scalability and capability of working in harsh environment, the use of wireless communication is gaining in importance. In the past, some efforts were pursued to encapsulate wired standards over wireless link, but their diffusion is limited by reliability and predictability requirements. In addition, event-driven protocols borrowed from the consumer world (as IEEE802.11 or IEEE802.15.4) are not well suited for some industrial applications. In this paper, authors present the design and the experimental evaluation of a wireless real-time communication protocol that tries to overcome these limits. It exploits standard hardware to lower cost and implements a hybrid medium access strategy. Time Division Multiple Access scheduling is used to ensure time deadlines respect, while Carrier Sense Multiple Access with Collision Avoidance is used for acyclic communications, as those involved in network management. It has been successfully adopted for temperature monitoring in plastic machineries. The prototype network adopts star topology and can manage up to 16 nodes with a refresh time of 128 ms.

A Sensor Network Architecture for Tsunami Detection and Response

In this paper, we propose a sense and response system for tsunami detection and mitigation. We use the directed diffusion routing protocol as a baseline network protocol and develop several communication mechanisms to improve its performance. These include an efficient flooding technique, a route repair algorithm, and distributed services framework. We summarize the analysis mechanism used to predict tsunami propagation and briefly discuss the results of this algorithm. Finally, we describe potential barrier mechanisms and the real-time communication protocol that supports time-critical response of the system.

Implementation and analysis of real-time communication protocol compositions

A flexible way of building modular communication stacks relies on the use of protocol composition. This paper describes a protocol composition framework that simplifies the task of deriving the worst-case response time of a protocol composition from the protocol implementation. In order to derive the worst-case response time of a protocol composition, one needs to capture its event-graph: the event-graph consists of the set of all events processed by each component and the relation between those events. The framework, called RT-Appia, takes a pragmatic approach: instead of requiring the use of domain specific code analysis tools, or dedicated compilers, it simply requires protocol programmers to make explicit which events are processed and produced by each layer, and how these events are related. An interesting aspect of the approach is that the same data structures that are used to simplify the task of computing the worst-case response time of the protocol composition are also used to optimize the performance and to debug the resulting implementation.

SENORA: A P2P Service-Oriented Framework for Collaborative Multirobot Sensor Networks

SENORA is an open hardware and software architecture for the cooperative coordination of multiple heterogeneous mobile robots operating in a common environment. It is designed to meet the stringent requirements of modern loosely coupled multirobot architectures, such as flexibility, reliability, and fault tolerance. As such, the proposed architecture enables the robots to cope with the ubiquitous presence of various types of uncertainties in their operating environments. SENORA is a fully autonomous and scalable sensory-based peer-to-peer (P2P) framework. It also offers a real-time inter-robot communication protocol and it is based on the state-of-the-art P2P technology, which is specifically designed to satisfy the requirements of physical sensory data publishing and fusion. This architecture is implemented and evaluated on a team of indoor mobile robots. The test results manifest the architecture's distinguished features and capabilities