Real-Time Communication

Telemedicine promises an improvement of health care service quality in rural, urban, dense and mobile areas. In order to implement the telemedicine in these areas, a low cost telemedicine system with acceptable quality for medical data transfer is required. This paper discusses simulation and implementation results of a low cost telemedicine system including wireless medical interface and communication infrastructure. A simulation has been done to investigate the network quality of service. The infrastructure has been also implemented using low cost 5.8 GHz transceiver for backhauls and low cost 2.4 GHz transceiver for clients. Test result shows that the low cost telemedicine system is able to do real time communication between patient and medical staff with medical data rate up to 2 Mbps. It shows that the low cost telemedicine system using wireless mesh network can be implemented in remote area with acceptable medical data transfer quality.

In this article, we assess the value of VRoma for Latin language learning. In particular, we discuss three exercises that we developed which combine Latin language and Roman culture in order to help students reinforce their Latin skills and gain a more in-depth understanding of ancient Roman society. Daily journals and evaluations of the assignments provided an assessment of student motivation and gave us information concerning students' perceptions of the benefits and challenges of working in the VRoma MOO. Transcripts and e-mail responses, both composed in Latin, allowed us to assess both the quality of students' interaction in the target language and their understanding of cultural and linguistic structures. Our studies have shown that by combining visual arts and cultural data with the capacity for real time communication in Latin, VRoma provides a unique opportunity for students to be immersed in language and culture simultaneously. Such an opportunity is not only useful for developing students' language skills but also for giving them a more sophisticated understanding of the ways that language and culture are integrated.

Real-time control applications will benefit in the near future from the enhanced performance provided by multi-core processor architectures. Nevertheless real-time communication will continue to be critical in distributed plasma control systems where the plant under control typically is distributed over a wide area. At RFX-mod real-time communication is crucial for hard real-time plasma control, due to the distributed architecture of the system, which consists of several VMEbus stations. The system runs under VxWorks and uses Gigabit Ethernet for sub-millisecond real-time communication. To optimize communication in the system, a set of detailed measurements has been carried out on the target platforms (Motorola MVME5100 and MVME5500) using either the VxWorks User Datagram Protocol (UDP) stack or raw communication based on the data link layer.

Few would argue that music is basic to the human experience, and that at its best, it can unify, transform, and transcend. Accordingly, it is not only valuable to experience music but also to nurture the innate musical ability that every human possesses. In resource-limited environments, the prospect of musical development through the study of an instrument can be sparse. In particular, children in resource-poor rural settings may have little opportunity to discover the delight of expressing the inexpressible through a musical instrument. ...

Several distributed real-time applications (e.g., medical imaging, air traffic control, and video conferencing) demand hard guarantees on the message delivery latency and the recovery delay from component failures. As these demands cannot be met in traditional datagram services, special schemes have been proposed to provide timely recovery for real-time communications in multihop networks. These schemes reserve additional network resources (spare resources) a priori along a backup channel that is disjoint with the primary. Upon a failure in the primary channel, its backup is activated, making the real-time connection dependable. In this paper, we propose a new method of providing backups called segmented backups, in which backup paths are provided for partial segments of the primary path rather than for its entire length, as is done in the existing schemes. We show that our method offers: 1) improved network resource utilization; 2) higher average call acceptance rate; 3) better quality-of-service guarantees on propagation delays and failure-recovery times; and 4) increased flexibility to control the level of fault tolerance of each connection separately. We provide an algorithm for routing the segmented backups and prove its optimality with respect to spare resource reservation. We detail necessary extensions to resource reservation protocol (RSVP) to support our scheme and argue that they increase the implementation complexity of RSVP minimally. Our simulation studies on various network topologies demonstrate that spare resource aggregation methods such as backup multiplexing are more effective when applied to our scheme than to earlier schemes.

Many knowledge management (KM) efforts revolve around managing documents in a repository or enabling better real-time communication. An ideal approach would combine these with the ability to create knowledge content that can be either formal or informal in nature, in a rapid, real-time manner. We will call this Rapid Knowledge Construction (RKC). This paper describes the concepts underpinning our approach to RKC, and provides a case study of the approach in an industry context. The Compendium approach, which has been applied in projects in both industry and academic settings, facilitates the rapid creation of the content of a KM repository, by combining collaborative hypermedia, group facilitation techniques, and an analytical methodology rooted in knowledge acquisition and structured analysis. Compendium addresses key challenges for the successful introduction of KM technologies into work practice: (i) customization for different use contexts; (ii) integration of formal and informal communication; (iii) integration of both prescribed and ad hoc representations; (iv) validation and cross-referencing of the repository 'on the fly' at the point of entry;

Field Programmable Gate Array (FPGA) devices are coming very strongly in the digital hardware systems due to the availability of ready to use resources, parallel logic operations and reconfigurable designs. The usage of FPGA systems in real time domain is also a very fruitful proposition as the FPGA devices are coming with processing cores for Real Time data processing. In a complex system scenario involving a large amount of processing tasks, there is a requirement of building the system using multiple FPGA devices. To make this possible we have to establish a real time data communication between the FPGA devices and to make it even better we have to apply data encryption techniques for making this communication secured. In this paper we demonstrate the design and implementation of a 32-bit RSA algorithms by developing suitable Hardware and Software design on Xilinx Spartan-3E (XC3S500E-FG320) device, the implementation has been tested successfully for real time serial data communication between multiple FPGA devices using the RS232 serial interface. This development work is also useful for the embedded applications, which requires on board execution of security algorithms. The system is optimized in terms of execution speed and also has been verified using real time debugging tools.

Cost related to the wiring of sensors and actuators in the manufacturing industry is rapidly increasing with the number of field devices. Complex engineering as well as cable wear and tear are important factors. For over a decade, fieldbuses have been the dominating approach to simplify installation, reduce engineering efforts, and increase reliability at the field level. The next step in this process is to introduce wireless communication in certain problematic parts of the field network. In order to do this, a reliable real-time communication system, designed to cope with the harsh environments where factory automation systems are employed, is required. The Wireless Interface for Sensors and Actuators (WISA), with its two subconcepts WISA-power and WISA-com, is such a system. This paper discusses how the WISA concept can be efficiently integrated into wired field networks for factory automation-both state-of-the-art [Process Fieldbus Decentral Peripherals (PROFIBUS DP)] and new (PROFINET IO) networks. We propose amendments to WISA, which will improve the 802.11b/g coexistence and harmonize the integration of WISA for sensor/actuator communication in, e.g., PROFINET IO systems. The suggested improvements relate to both the radio protocol in order to improve coexistence with other wireless technologies as well as concepts for the integration of WISA into the field network of PROFINET/PROFIBUS.

The recent development of Field-Programmable Gate Array (FPGA) architectures, with soft core (MicroBlaze) and hard core (PowerPC) processors, embedded memories and IP cores, offers the potential for high computing power. Presently FPGAs are considered as a major platform for high performance embedded applications as it provides the opportunity for reconfiguration as well as good clock speed and design resources. As the complexities in the embedded applications increase, use of an operating system brings in a lot of advantages. In present day application scenarios most embedded systems have real-time requirements that demand the use of Real-time operating systems (RTOS), which creates a suitable environment for real time applications to be designed and expanded easily. In an RTOS the design process is simplified by splitting the application code into separate tasks and then the scheduler executes them according to a specific schedule, meeting the real-time deadline. In this research work, we propose the design and implementation of a real-time FPGA based application, which demonstrates the creation of real-time process tasks in FPGA systems for successful real-time communication between multiple FPGA systems. We have chosen the RSA based encryption and decryption algorithm for this implementation, as security is one of the most important need for data communication. At first we demonstrate the real-time execution of multiple process tasks in a single FPGA system for the encryption and decryption of data. Next we describe the most challenging part of our work, where we establish the real-time communication between two FPGA systems, each running the encryption engine and decryption engine respectively and communicating with one another via an RS232 communication link. The results show that our design is better in terms of execution speed in comparison with the existing research works.

This paper proposes a virtual token-passing mechanism, which allows the coexistence of legacy industrial Ethernet devices with enhanced (real-time) devices in the same bus network. The VTPE mechanism allows the implementation of real-time (RT) applications upon legacy bus-based industrial networks, enforcing the adequate timing behavior of the supported applications. It enables the traffic separation between legacy Ethernet stations and enhanced (RT) stations. A set of experiments has been performed, which allowed to measure the message access delay and the token rotation time. The achieved results clearly demonstrate that the VTPE architecture enables the support of RT communication upon legacy bus-based industrial Ethernet networks, even when the communication medium is shared with uncontrolled traffic sources.

User participation has transformed the way news travel the globe. With the rise of the 'Web 2.0' phenomenon users have been empowered with the means of creating and distributing informational items, which we call social feeds. Platforms like Twitter 1 and Facebook 2 provide a variety of tools to facilitate real-time communication among people. But social sites are not limited to personal chat; they also provide an effective means for organizing large groups of people in response to catastrophic disasters. Monitoring these feeds can provide time-critical information, but can easily lead to information overload due to the large amount of data being shared.

Enabling mobility in IP networks is an important issue for making use of the many light-weight devices appearing at the market. The IP mobility support being standardized in the IETF uses tunnelling of IP packets from a Home Agent to a Foreign Agent to make the mobility transparent to the higher layer. There are a number of problems associated with Mobile IP, such as triangular routing, each host needing a home IP address, tunnelling management, etc. In this paper, we propose to use mobility support in the application layer protocol SIP where applicable, in order to support real-time communication in a more efficient way.

With the success of wireless technologies in consumer electronics, standard wireless technologies are envisioned for the deployment in industrial environments as well. Industrial applications involving mobile subsystems or just the desire to save cabling make wireless technologies attractive. Nevertheless, these applications often have stringent requirements on reliability and timing. In wired environments, timing and reliability are well catered for by fieldbus systems (which are a mature technology designed to enable communication between digital controllers and the sensors and actuators interfacing to a physical process). When wireless links are included, reliability and timing requirements are significantly more difficult to meet, due to the adverse properties of the radio channels.

In this paper, a new Traffic Separation mechanism (TSm) is proposed for CSMA-based networks. The TSm mechanism is intended to be used as an underlying traffic separation mechanism, able to prioritize traffic in CSMA-based networks. It allows the coexistence of standard CSMA (non-modified) stations with TSm (modified) stations in the same communication domain. When a station implementing the TSm mechanism has a high-priority message to transfer, it will impose its transfer prior to any message from standard CSMA stations. This behavior guarantees the highest transmitting probability to the TSm-enabled station in open communication environments. Therefore, the TSm approach can be used as an underlying mechanism to build real-time communication systems upon CSMA-based networks. The behavior of the TSm mechanism was assessed by simulation in the case of a relevant CSMA-based network (IEEE 802.11). The simulation analysis shows that the TSm mechanism guarantees values for both the throughput and the average access delay that significantly improve the results obtained for standard IEEE 802.11 stations.

Today, mobile communications play a central role in the voice/data network arena. With the deployment of 3G just around the corner, new directions are already being researched. In this paper we address the evolution of mobile communications, from its first generation, 1G, to the latest 3G, and ...

Data gathering in a timely and reliable fashion has been a key concern in wireless sensor networks particularly related to military applications. The introduction of real time communication has created additional challenges in this area with different communication constraints. Since sensor networks represent a new generation of time-critical applications, it is often necessary for communication to meet real time constraints. However, research dealing with providing QoS guarantees for real time traffic in sensor networks is still immature. To provide guaranteed QoS in WSN, this paper presents a novel analytical model based on limited service polling discipline. The proposed model implements two queues in a sensor node which are being served according to round robin service. The model is based on M/D/l queueing system (a special class of M/G/l queueing systems), which takes into account two different classes of traffic in a sensor node. The exact queueing delay in a sensor node for corresponding classes is calculated. Further, the analytical results are validated through an extensive simulation study.

Large-scale wireless sensor networks represent a new generation of real-time embedded systems with significantly different communication constraints from traditional networked systems. This paper presents RAP, a new real-time communication architecture for large-scale sensor networks. RAP provides convenient, high-level query and event services for distributed micro-sensing applications. Novel location-addressed communication models are supported by a scalable and light-weight network stack. We present and evaluate a new packet scheduling policy called velocity monotonic scheduling that inherently accounts for both time and distance constraints. We show that this policy is particularly suitable for communication scheduling in sensor networks in which a large number of wireless devices are seamlessly integrated into a physical space to perform real-time monitoring and control. Detailed simulations of representative sensor network environments demonstrate that RAP significantly reduces the end-to-end deadline miss ratio in the sensor network. Proceedings of the Eighth IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS'02) 0-7695-1739-0/02 $17.00 © 2002 IEEE munication channel. Progress of user-level activities and their ability to meet end-end deadlines are therefore determined by scheduling of the communication medium rather than scheduling of the processor. Towards that end, new real-time communication architectures are required for ad hoc wireless environments.

In Next Generation Networks (NGN) a variety of services with different requirements, like real time communications, broadband Internet access, email services are expected. Consequently, Packet Scheduling mechanisms and Resource Allocation techniques for Quality of Service (QoS) guarantees will play a key role.

The cabled LEO-15 observatory was a vision of Fred Grassle and Chris von Alt that became a reality in 1996 with the deployment of Nodes A and B in 15 meters of water off of Tuckerton, New Jersey. These nodes have served the scientific community well for almost a decade providing power to a variety of sensors and bi-directional real-time communication between the sensors and the PIs computer located on shore. However, technology and scientific needs have changed since these nodes were deployed making it necessary to upgrade the nodes to meet not only today's demands but also to provide expandability and flexibility for the future. The nodes must be able to do more than provide real-time data. They need to be a part of a sustained and interactive network of autonomous and remote platforms that coordinate sampling in space as well as in time. Rutgers University Mid-Atlantic Bight National Undersea Research Center (MABNURC) has partnered with WETSAT, Inc. to accomplish the LEO upgrade and expansion.

The Controller Area Network (CAN) is a fieldbus network with real-time capabilities. It is generally considered that CAN guarantees atomic multicast properties, through its extensive error detection/signalling mechanisms. However, there are error situations where messages can be delivered in duplicate by some receivers or delivered only by a subset of the receivers.

In this paper, we address issues related to preventing traffic analysis in computer networks used for realtime mission-critical applications. We consider an IP-based network where headers of packets, including source host address and destination host address, are readable by an observer (i.e., by a potential enemy). Although the encryption of network packets significantly increases privacy, the density of the traffic can still provide useful information to the observer. We take an approach by manipulating traffic in the network through host-based rerouting and traffic padding so that the traffic shows a time-invariant pattern. Thus, the observer can not derive any useful information about the real traffic pattern. By evaluating the performance of the algorithms used for this problem in terms of acceptance rate and execution time, we found that some well-known theoretical optimal and nearoptimal algorithms failed to meet one or the other criteria. In this paper, we present a heuristic method that can effectively prevent traffic analysis while at the same time meeting real-time requirements. Our algorithm generates a plan that specifies where and when the dummy packets should be transmitted and if and how the payload packets should be rerouted and can yield high acceptance rate with low execution time. The success of the algorithm stems from the fact that it explicitly takes into account of real-time requirements and properly balances the traffic over the links.

The paper presents a family of architectures for FFT implementation based on the decomposition of the perfect shuffle permutation, which can be designed with variable number of processing elements. This provides designers with a trade-off choice of speed vs. complexity (cost and area.). A detailed case study is provided on the implementation of 1024point FFT with 2 processing elements using 45nm process technology, including area, timing, power and place-and-route results.

Until recently, research on cellular networks concentrated only in single-hop cellular networks. The demand for high throughput has driven to architectures that use multiple hops in the presence of infrastructure. We propose an architecture for multihop cellular ...

Microblogs have received considerable attention in crisis communication due to its real-time nature. Despite this, research has not adequately addressed how users make use of information amongst the vast amount of real-time content available in a crisis. Hence, this study aims to understand information use in crisis situations by employing microblogs. Taylor"s [4] information use environment (IUE) model provides theoretical background for this study. According to this model, there are eight classes of information use. We focus on the IUE surrounding the 2010 Icelandic volcano eruption. Our study uses Twitter to analyze users" postings related to this volcano. The types of postings were ascertained using content analysis. Our findings suggest enlightenment to be the largest category of information use. Other categories such as status messages, problem understanding and factual data were also reported. Further, humour not previously identified by Taylor [4] emerged as a substantial class of information use.

Many software applications have been developed in recent years, to exploit the convergence between voice and data networks and the availability to the final user of high speed and low cost connections. These software applications operate in real-time communication scenarios and, at least in principle, should ensure portability and platform independence. In this paper a software IP telephony application completely written in Java language and called JavaNetPhone is presented. The aim of such a communication tool is to operate in a business LAN environment, based on the Media Gateway Control Protocol framework, to extend the already available telephony facilities. At the authors' best knowledge, other similar applications exist, but they adopt different programming languages and sometimes are not platformindependent. The prototype functionalities evaluation show that the application can give acceptable voice performance, and further developments are being pursued to provide the adoption of wireless communication technologies, such as BlueTooth and WiFi, according to the increasing demand for user's mobility.

The dramatically increased bandwidths and processing capabilities of future high-speed networks make possible many distributed real-time applications, such as sensor-based applications and multimedia services. Since these applications will have traffic characteristics and performance requirements that differ dramatically from those of current data-oriented applications, new communication network architectures, and protocols will be required. In this paper we discuss the performance requirements and traffic characteristics of various real-time applications, survey recent developments in the areas of network architecture and protocols for supporting real-time services, and develop frameworks in which these, and future, research efforts can be considered

This paper presents the design and implementation of a user-level real-time network system in Real-Time Mach. Traditional network systems for microkernel based operating systems, which tend to focus on high performance and flexibility, are not suitable for real-time communication. Our network system provides a framework for implementing real-time network protocols which require to bound protocol processing time, and it is suitable for implementing on microkernel based operating systems. In this paper, we especially focus ...

Open Manufacturing Equipment is mandatory to answer the demand of modern manufacturing for distributed monitoring or automation, and to allow fast system reconfiguration. The project is inspired by the reference models defined by the ISO/OSI Manufacturing Message Specification for remote machine tool supervision (MMS) and the Open System Architecture within Control Applications (OSACA). Instead of proposing MMS or OSACA protocols for communication, we propose a unified object-oriented solution based on the OMG-CORBA software bus. Adopting a common object-oriented approach for both remote communication and internal architecture of a NC platform is conceivable. It leads to a design very close to the one proposed in the mentioned standards. The consequences of including a Manufacturing Object Messaging System on the NC design model are discussed. A Java and CORBA based demonstration prototype has been developed. The end of the paper describes how we address real-time constraints on communications.

A new approximation technique to a certain class of nonlinear filtering (signal processing) problems is considered here. The method is based on an approximation of a nonlinear, partially observable system by a bilinear model with fully observable states. The filter development proceeds from the assumption that the unobservable states are conditionally Gaussian with respect to the observation initially. The method is shown to be promising for real-time communication and sonar applications as demonstrated by computer simulations. Moreover, some of the traditional techniques evolve as special cases of this methodology.

A real time simulation study for the evaluation of traffic flow in low earth orbit (LEO) satellite constellations, used for the interconnection of high-speed networks, is presented in this paper. The proposed model simulates end to end the traffic process at the packet level, supporting successfully the implementation of self-similar traffic sources , a modeling approach that has been considered more realistic than the well-known Poisson, for real-time communications. An in-depth study for the establishment of inter-satellite links (ISLs) and the design of the terrestrial and space segments is presented and the performance of the integrated system is evaluated in terms of delay and throughput parameters.

Low voltage electrical wiring in homes has largely been dismissed as too noisy and unpredictable to support high speed communication signals. Power Line Communication (PLC) is a communication method where signals are carried across already existing power lines, rather than through other mediums such as optical fibers or radio waves. PLC has been a very important inter-discipline topic for power, communications, industrial and automation engineers and researchers since 1980s. Designing and planning optimized or standard PLC systems require information and data regarding signal attenuations, load variations and communication performance for various locations of the world which have different power networks. In this paper, we highlight our own proprietary designed real-time communication (RTC) routing protocol based on flood transmission for the application of home automation via power line. The designed protocol also has features such as multitasking, Amplitude Shift Keying (ASK) modulation and even parity error detection. Multipoint of receiver units can be controlled (On / Off) by the main controller unit sending command data using power line as transmission medium to the corresponding devices. Analysis on protocol performance and reliability test in terms of packet drop, delay-jitter and number of loads along the line had been carried out.

Ethernet was not originally developed to meet the requirements of real-time industrial automation systems and it was commonly considered unsuited for applications at the field level. Hence, several techniques were developed to make this protocol exhibit real-time behavior, some of them requiring specialized hardware, others providing soft-real-time guarantees only, or others achieving hard real-time guarantees with different levels of bandwidth efficiency. More recently, there has been an effort to support quality-of-service (QoS) negotiation and enforcement but there is not yet an Ethernet-based data link protocol capable of providing dynamic QoS management to further exploit the variable requirements of dynamic applications. This paper presents the FTT-Ethernet protocol, which efficiently supports hard-real-time operation in a flexible way, seamlessly over shared or switched Ethernet. The FTT-Ethernet protocol employs an efficient master/multislave transmission control technique and combines online scheduling with online admission control, to guarantee continued real-time operation under dynamic communication requirements, together with data structures and mechanisms that are tailored to support dynamic QoS management. The paper includes a sample application, aiming at the management of video streams, which highlights the protocol's ability to support dynamic QoS management with real-time guarantees.

Handovers may cause delays and packet losses that affect real-time communication performance. Mobility protocols at several layers are designed to support handover, but they need to be optimized to ensure high-quality application performance. Existing optimization techniques are not sufficient to take care of interdomain and intertechnology handovers involving different access technologies, such as Wi-Fi, GSM, CDMA, and WiMAX. We categorize several types of handover, describe handover delay components, and propose a handover optimization framework called Media Independent Pre-Authentication that can provide optimizations for interdomain and intertechnology handover in a manner that is transparent to mobility management protocols. In addition, we also present experimental results demonstrating that this framework can achieve a significant reduction in handover delays for both network-layer and application-layer mobility management protocols.

Wireless Sensor Networks (WSNs) have been attracting increasing interests for developing a new generation of embedded systems with great potential for many applications such as surveillance, environment monitoring, emergency medical response and home automation. However, the communication paradigms in WSNs differ from the ones attributed to traditional wireless networks, triggering the need for new communication protocols. In this context, the recently standardised IEEE 802.15.4 protocol presents some potentially interesting features for deployment in wireless sensor network applications, such as powerefficiency, timeliness guarantees and scalability. Nevertheless, when addressing WSN applications with (soft/hard) timing requirements some inherent paradoxes emerge, such as power-efficiency versus timeliness, triggering the need of engineering solutions for an efficient deployment of IEEE 802.15.4 in WSNs. In this chapter, we will explore the most relevant characteristics of the IEEE 802.15.4 protocol for wireless sensor networks and present the most important challenges regarding time-sensitive WSN applications. We also provide some timing performance and analysis of the IEEE 802.15.4 that unveil some directions for resolving the previously mentioned paradoxes.

Performance of a modem designed for HF communications is presented in this contribution. The aim was to attain the real time communication for interactive voice transmission. Therefore, powerful coding for error protection and long interleaving was not permitted. Frequency selective HF channel was converted into a set of frequency flat channels with MultiCarrier modulation, Orthogonal Frequency Division Multiplex (OFDM). Spread Spectrum Technique (SST) was applied to improve modem's performance. This technique takes advantage of frequency diversity, as one symbol is transmitted (spreaded) over larger number of subcarriers (N), and more symbols (N) are transmitted simultaneously. Use of SS techniques permits us to perform advanced signal processing in receiver and further enhance modem's performance. We applied Multi User Detector (MUD) in receiver, denoting as "virtual users" the symbols transmitted simultaneously with different spreading codes. For data transmission, when delay is not restricted, coding and interleaving can be incorporated, improving drastically the performance.