Communication Protocol

Many different quantum information communication protocols such as teleportation, dense coding and entanglement based quantum key distribution are based on the faithful transmission of entanglement between distant location in an optical network. The distribution of entanglement in such a network is however hampered by loss and noise that is inherent in all practical quantum channels. Thus, to enable faithful transmission one must resort to the protocol of entanglement distillation. In this paper we present a detailed theoretical analysis and an experimental realization of continuous variable entanglement distillation in a channel that is inflicted by different kinds of non-Gaussian noise. The continuous variable entangled states are generated by exploiting the third order non-linearity in optical fibers, and the states are sent through a free-space laboratory channel in which the losses are altered to simulate a free-space atmospheric channel with varying losses. We use linear optical components, homodyne measurements and classical communication to distill the entanglement, and we find that by using this method the entanglement can be probabilistically increased for some specific non-Gaussian noise channels.

This paper presents PROTOB, an object-oriented methodology and CASE system based on an extended dataflow model dcfined using PROT nets. It consists of several tools supporting specification, modclling and prototyping activities within the framework of the operational software life cycle paradigm. As its major application area it addresses distributed systems, such as real-time embedded systems, communication protocols and manufacturing control systems. The system automatically generates the distributed and Objcct-Oriented implementation code in Ada cxploiting advanced features of the language such as tasks and packages. Acknowledgments -This work has been partly supported by the C.N.R. Progetto Finalizzato Sistemi Informatici e Calcolo Parallel0 'SPECTER' -Specification, Design and Validation of Real Time Systems.

Consider the problem to design a component that combined with a known part of a system, called the context, conforms to a given overall specification. This question arises in several applications ranging from logic synthesis to the design of discrete controllers. We cast the problem as solving abstract equations over languages. As part of an ongoing research project we already defined language equations with respect to two language composition operators: synchronous composition,, and parallel composition,¥; conformity ...

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Long reconfiguration times form a major bottleneck in dynamic reconfigurable systems. Many approaches have been proposed to address this problem. However, improvements in the configuration circuit that introduces this overhead are usually not considered. The high reconfiguration times are due to the large amount of configuration bits sent through a constrained data path. In order to alleviate this, we propose a novel FPGA configuration circuit architecture to speedup bitstream (re)configuration and relocation. Experimental results using the MCNC benchmark set indicate that our proposal reconfigures 4 times faster and relocates 19.8 times more efficient compared to the state of the art approaches. This is achieved by transporting only the data required for the configuration in flight and by avoiding external communication while relocating. Moreover, the configuration bitstream sizes of the evaluated benchmarks are reduced by 65 % on average. In addition, our proposal introduces negligible hardware and communication protocol overheads.

Complexity of distributed real-time applications such as automotive electronics has increased dramatically over the last couple of years. As a result, developing communication protocols to address real-time requirements of these applications such as reliability, intime delivery of messages, priority support, and faulttolerance needs more sophisticated techniques. To satisfy these requirements, special communication architectures have been designed. The most important methods presented are TDMA (Time Division Multiple Access), Token Ring and CAN (Controller Area Network). Recently, a new algorithm called RDM (Round Data Mailer) has been presented. The focus of this paper is on the studying of the Round Data Mailer technique and evaluating its message delivery performance by making a comparison of the result of simulated RDM and CAN.

Design space exploration is a component of the product optimization process that confronts the architect with the task of evaluating a large number of design choices. In order to achieve this goal software tools are used to automatically determine the benefits and drawbacks of each proposed implementation. In the field of processor architecture one such tool is UNISIM. The UNISIM environment provides a framework for design space exploration in the form of libraries and tools for evaluating designs through cycle-accurate simulation. UNISIM emphasizes modularity and reusability of modules, by defining a standard interface for inter-module communication. The simulator is capable of providing accurate results in terms of number of cycles required for the execution of a specific program, however it does not offer any information regarding the power consumption, the occupied silicon area or the clock rate the design is capable of. In order to overcome these limitations, we attempt to produce in this study a hardware implementation that closely follows the structure of the simulator at source code level. In large part, this translation process involved only a change in syntax from the C code to Verilog. Our study shows that our objective can be achieved at moderate implementation cost while preserving all the features of the original software simulation. We emphasize modularity and a standardized control flow for intermodule communication, which are also the defining characteristics of the software implementation.

Races in Message Sequence Charts may lead to a bad interpretation of described behaviours, and are often considered as a design error. While there is a quadratictime algorithm detecting races in Basic Message Sequence Charts (BMSCs), the problem is undecidable for High-level Message Sequence Charts (HMSCs). To improve this negative situation for HMSCs, we introduce two new notions: a new concept of race called trace-race and an extension of the HMSC formalism with open coregions, i.e. coregions that can extend over more than one BMSC. We present three arguments showing benefits of our notions over the standard notions of race and HMSC. First, every trace-race-free HMSC is also race-free. Second, every race-free HMSC can be equivalently expressed as a trace-race-free HMSC with open coregions. Last, the trace-race detection problem for HMSC with open coregions is decidable and PSPACE-complete (the problem is in P if the number of processes and gates is fixed).

The objective of the Canadian Advanced Nanospace eXperiment (CanX) program is to develop highly capable "nanospacecraft," or spacecraft under 10 kilograms, in short timeframes of 2-3 years. CanX missions offer low-cost and rapid access to space for scientists, technology developers, and operationally responsive missions. The Space Flight Laboratory (SFL) at the University of Toronto Institute for Aerospace Studies (UTIAS) has developed the Canadian Advanced Nanospace eXperiment 2 (CanX-2) nanosatellite that launched in April 2008. CanX-2, a 3.5-kg, 10 x 10 x 34 cm satellite, features a collection of scientific and engineering payloads that push the envelope of capability for this class of spacecraft. The primary mission of CanX-2 is to test and demonstrate several enabling technologies for precise formation flight. These technologies include a custom cold-gas propulsion system, a 30 mNms nanosatellite reaction wheel as part of a three-axis stabilized momentum-bias attitude control system, and a commercially available GPS receiver. The secondary objective of CanX-2 is to fly a number of university experiments including an atmospheric spectrometer. At the time of writing CanX-2 has been in orbit for three weeks and has performed very well during preliminary commissioning. The mission, the engineering and scientific payloads, and the preliminary on-orbit commissioning experiences of CanX-2 are presented in this paper.

The objective of the Canadian Advanced Nanospace eXperiment (CanX) program is to develop highly capable "nanospacecraft," or spacecraft under 10 kilograms, in short timeframes of 2-3 years. CanX missions offer low-cost and rapid access to space for scientists, technology developers, and operationally responsive missions. The Space Flight Laboratory (SFL) at the University of Toronto Institute for Aerospace Studies (UTIAS) has developed the Canadian Advanced Nanospace eXperiment 2 (CanX-2) nanosatellite that launched in April 2008. CanX-2, a 3.5-kg, 10 x 10 x 34 cm satellite, features a collection of scientific and engineering payloads that push the envelope of capability for this class of spacecraft. The primary mission of CanX-2 is to test and demonstrate several enabling technologies for precise formation flight. These technologies include a custom cold-gas propulsion system, a 30 mNms nanosatellite reaction wheel as part of a three-axis stabilized momentum-bias attitude...

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Many organizations around the world have started to adopt Web services as well as server farms and clouds hosted by large enterprise and data centers for various applications. Web Services offer several advantages over other communication technologies. However, they have high latency and often suffer from congestion and bottlenecks due to the massive load generated by web service requests from large numbers of end users. SOAP (Simple Object Access Protocol) is the basic XML-based communication protocol of Web services. XML is a verbose encoding language in comparison with other technologies such CORBA and RMI. In this paper, two new redundancy-aware SOAP Web message aggregation models -Twobit and One-bit XML status tree -are proposed to enable the Web servers to aggregate SOAP responses and send them back as one compact aggregated message in order to reduce the required bandwidth, latency, and improve the overall performance of Web services. XML message compressibility, the Jaccard based clustering technique, and the vector space model are three similarity measurements that are proposed to cluster SOAP messages as groups based on their similarity degree. The clustering based similarity measurements enable the aggregation techniques to potentially reduce the required network traffic by minimizing the overall size of the messages. The experiments show significant performance for both aggregation techniques achieving compression ratios as high as 25 for aggregated SOAP messages.

Despite significant research effort, the performance of distributed medium access control methods has failed to meet theoretical expectations. Previously, we have proposed the concept for a fully-distributed, but non-optimum opportunistic medium access control called Channel MAC. In this paper, we present the Channel MAC protocol operations addressing the issues of information exchange between nodes, predicting transmission intervals and selecting transmission thresholds to achieve fairness. Although the proposed prediction scheme based on mean channel fading is simple to implement, it is imperfect leading to some performance losses. Event based simulation tool NS2 is used to analyse the performance of Channel MAC in a number of network scenarios. We analyse the performance of the proposed protocol using the performance metric; throughput, fairness and delay. The simulation results show throughput performance improvement of up to 30% with Channel MAC over IEEE 802.11 in certain multihop scenarios. Generally, the proposed protocol outperforms 802.11 in all analysed network scenarios. We also show that the severe resource starvation problem (unfairness) of IEEE 802.11 in some network scenarios is reduced by the Channel MAC mechanism.

The purpose of this article is to accomplish various appointed objectives. The objectives of this article include: to become acquainted with the Modbus RTU protocol, to implement the Modbus RTU protocol onto an Arduino Uno microcontroller as a slave and to test the Arduino Uno slave using a free Modbus master program. The Arduino Uno slave must be fully configurable where the user can set all the Modbus communication parameters such as slave ID, parity, communication rate, number of stop bits, etc. The user must also be able to assign values or variables to a particular coil or register regardless of the order of the previously used coils or registers. The Arduino slave must also communicate with the master over a RS232 connection.

The purpose of this article is to accomplish various appointed objectives. The objectives of this article include: to become acquainted with the Modbus RTU protocol, to implement the Modbus RTU protocol onto an Arduino Uno microcontroller as a slave and to test the Arduino Uno slave using a free Modbus master program. The Arduino Uno slave must be fully configurable where the user can set all the Modbus communication parameters such as slave ID, parity, communication rate, number of stop bits, etc. The user must also be able to assign values or variables to a particular coil or register regardless of the order of the previously used coils or registers. The Arduino slave must also communicate with the master over a RS232 connection.

Dagstuhl seminar 10381 on robust query processing (held 19.09.10 -24.09.10) brought together a diverse set of researchers and practitioners with a broad range of expertise for the purpose of fostering discussion and collaboration regarding causes, opportunities, and solutions for achieving robust query processing. The seminar strove to build a unified view across the loosely-coupled system components responsible for the various stages of database query processing. Participants were chosen for their experience with database query processing and, where possible, their prior work in academic research or in product development towards robustness in database query processing. In order to pave the way to motivate, measure, and protect future advances in robust query processing, seminar 10381 focused on developing tests for measuring the robustness of query processing. In these proceedings, we first review the seminar topics, goals, and results, then present abstracts or notes of some of the seminar break-out sessions. We also include, as an appendix, the robust query processing reading list that was collected and distributed to participants before the seminar began, as well as summaries of a few of those papers that were contributed by some participants.

The increasing complexity of embedded systems requires modeling at higher levels of abstraction. Transaction level modeling (TLM) has been proposed to abstract communication for high-speed system simulation and rapid design space exploration. Although being widely accepted for its high performance and efficiency, TLM often exhibits a significant loss in model accuracy. In this article, we systematically analyze and quantify the speed/accuracy trade-off in TLM. To this end, we provide a classification of TLM abstraction levels based on model granularity and define appropriate metrics and test setups to quantitatively measure and compare the performance and accuracy of such models. Addressing several classes of embedded communication protocols, we apply our analysis to three common bus architectures, the industry-standard AMBA advanced high-performance bus (AHB) as an on-chip parallel bus, the controller area network (CAN) as an off-chip serial bus, and the Motorola ColdFire Master Bus as an example for a custom embedded processor bus. Based on the analysis of these individual busses, we then generalize our results for a broader conclusion. The general TLM trade-off offers gains of up to four orders of magnitude in simulation speed, generally however, at the price of low accuracy. We conclude further that model granularity is the key to efficient TLM abstraction, and we identify conditions for accuracy of abstract models. As a result, this article provides general guidelines that allow the system designer to navigate the TLM trade-off effectively and choose the most suitable model for the given application with fast and accurate results.

We develop an octonionic representation of the payoff function for three player, two strategy, maximally entangled quantum games in order to obtain computationally friendly version of this function. This computational capability is then exploited to analyze and potentially classify the Nash equilibria in the quantum games.

The commercial availability of computational resources enable consumers to scale their applications on-demand. However, it is necessary for both consumers and providers of computational resources to express their technical and economic preferences using common language protocols. Ultimately, this requires clear, flexible and pragmatic communication protocols and policies for the expression of bids and resulting generation of service level agreements (SLAs). Further standardization efforts in such description languages will foster the specification of common interfaces and matching rules for establishing SLAs. Grid middleware are not compatible with market-orientated resource provisioning. We aim to reduce this gap by defining extensions to a standardized specification such as JSDL. Furthermore, we present a methodology for matchmaking consumer bids and provider offers and map the additional economic attributes into a SLA. We demonstrate the usage of the message protocols in an application scenario.

In developing countries, demand for 24x7x365 availability of reliable power is on rise. On the other side distribution utilities in these countries, finds growing deployment of renewables driven distributed generation. This on one side, creates complex and challenging network topologies, but in process ensures better availability of power with integration and adoption of advanced control & automation. Under such scenario, integrated dual side voltage sensing reclosers helps distribution utilities in achieving different Fault Detection Isolation & Restoration (FDIR) schemes with smaller footprint in simple but performance efficient and cost-effective way. This paper, after brief introduction on power distribution improvement schemes, based on author experience highlights the application benefits of integrated dual voltage sensing reclosers for smart grid – FDIR initiatives

We address the problem of minimizing the communication involved in the exchange of similar documents. We consider two users, A and B, who hold documents x and y respectively. Neither of the users has any information about the other's document. They exchange messages so that B computes x; it may be required that A compute y as well. Our goal is to design communication protocols with the main objective of minimizing the total number of bits they exchange; other objectives are minimizing the number of rounds and the complexity of internal computations. An important notion which determines the efficiency of the protocols is how one measures the distance between x and y. We consider several metrics for measuring this distance, namely the Hamming metric, the Levenshtein metric (edit distance), and a new LZ metric, which is introduced in this paper. We show how to estimate the distance between x and y using a single message of logarithmic size. For each metric, we present the first communication-efficient protocols, which often match the corresponding lower bounds. In consequence, we obtain error-correcting codes for these error models which correct up to d errors in n characters using O(d•polylog(n)) bits. Our most interesting methods use a new transformation from LZ distance to Hamming distance.

This paper presents a family of intelligent ultra low R DSON power switches replacing electromechanical relays in the car. This approach removes fuses and reduces wire harness complexity with a significant system cost savings. The paper explains how the Power QFN (PQFN) package with multiple chips reduces board space, reaches R DSON of 2mΩ, provides very low thermal resistance and brings intelligent features to increase system reliability.

A.4 Results obtained by simulating in urban scenario the ES configuration (chunk_size=28278, timeout=6.00000, max_attempts=9). . . . . . . A.5 Results obtained by simulating in urban scenario the SA configuration (chunk_size=19756, timeout=6.43308, max_attempts=3). . . . . . . A.6 Results obtained by simulating in urban scenario the CARLINK configuration [24] (chunk_size=25600, timeout=8.0, max_attempts=8). A.7 Results obtained by simulating in highway scenario the PSO configuration (chunk_size=29257, timeout=6.42140, max_attempts=9). . . A.8 Results obtained by simulating in highway scenario the DE configuration (chunk_size=19810, timeout=6.91179, max_attempts=8). . . A.9 Results obtained by simulating in highway scenario the GA configuration (chunk_size=34542, timeout=9.54986, max_attempts=10). . . A.10 Results obtained by simulating in highway scenario the ES configuration (chunk_size=38490, timeout=8.15197, max_attempts=12). . . A.11 Results obtained by simulating in highway scenario the SA configu- ration (chunk_size=32002, timeout=8.21363, max_attempts=4). . . A.12 Results obtained by simulating in highway scenario the CARLINK configuration (chunk_size=25600, timeout=8.0, max_attempts=8). . A.13 Execution time in seconds for the algorithms to find the best solution (Best sol.) and to finish the whole process (Total) solving the OFTC problem in the urban scenario. Each row indicates an independent run of 30 (#).

The evaluation of new communication protocols for Vehicular Ad-hoc Networks (VANETs) is a hot topic in research. An efficient design and actual deployment of such software tools is crucial for any VANET. The design phase is difficult and often relies on computer simulation. The later evaluation of protocols in real VANETs is complex due to many difficulties concerning the availability of resources, accurate performance analysis, and reproducible results. Simulation is the most widely solution to make a good design but it presents also an important challenge: the fidelity of the simulation compared to the real results. In this article we measure the differences between the simulation versus the real results with actual moving cars in order to quantify the accuracy of the VANET simulations inside the European CARLINK Project 1 . After a thorough revision of the state of the art, we here go for an analysis of JANE and VanetMobiSim/ns-2, two simulation frameworks. Later, we have defined the scenario where both, simulations and real tests, will be carried out. Our results show that JANE is more appropriate for simulating applications, while ns-2 is more accurate in dealing with the underlying mobile communication network.

The emerging field of vehicular ad hoc networks (VANETs) deals with a set of communicating vehicles which are able to spontaneously interconnect without any pre-existing infrastructure. In such kind of networks, it is crucial to make an optimal configuration of the communication protocols previously to the final network deployment. This way, a human designer can obtain an optimal QoS of the network beforehand. The problem we consider in this work lies in configuring the File Transfer protocol Configuration (FTC) with the aim of optimizing the transmission time, the number of lost packets, and the amount of data transferred in realistic VANET scenarios. We face the FTC with five representative state-of-the-art optimization techniques and compare their performance. These algorithms are: Particle Swarm Optimization (PSO), Differential Evolution (DE), Genetic Algorithm (GA), Evolutionary Strategy (ES), and Simulated Annealing (SA). For our tests, two typical environment instances of VANETs for Urban and Highway scenarios have been defined. The experiments using ns-2 (a well-known realistic VANET simulator) reveal that PSO outperforms all the compared algorithms for both studied VANET instances.

Due to the autonomous nature of spacecraft, on-board devices feature relatively complex functionality in their software, including interface(s) that provide telecommands and telemetry. Once in space, the devices are physically inaccessible and even a small defect can cause a major failure from which recovery is impossible. To prevent defects with such consequences, the development of on-board software for space applications requires a substantial investment in quality and additional manual work results in increased cost. Therefore, it is necessary to consider opportunities that reduce manual work while minimizing the impact in quality. This paper presents the particular solution adopted for the GNSSaS mission (developed by the NSSTC) and generalizes it to propose a framework for the development of on-board software for small satellites. It evaluates different software components involved in a mission and attempts to identify all opportunities to use data modelling and automated code generation to support the development, validation and operations of software for both space and ground segments. The proposed opportunities are described in detail and their impacts are discussed in terms of quality and cost. As in previous works, the code generation from interface data models were explored and additional opportunities were implemented as well. As it is shown in the GNSSaS satellite, it is possible to develop feature rich, complex and flexible software in-time, in-quality and in-budget with a relatively small team.

Address-Event-Representation (AER) is a pixels whose code or address was on the bus. In this way, communication protocol for transferring asynchronous events cells with the same address in the emitter and receiver chips between VLSI chips, originally developed for bio-inspired are virtually connected with a stream of pulses. The receiver processing systems (for example, image processing). Such cell integrates the pulses and reconstructs the original low systems may consist of a complicated hierarchical structure frequency continuous-time waveform. Cells that are more with many chips that transmit data among them in real time, while performing some processing (for example, convolutions). active access the bus more frequently than those less active. To develop AER based systems for image processing it is very CHIPI CHIP2 convenient to have available some kind of tool for generating /_ IDIGITAL

Presently, there are many research work for sensor networks. In our previous work, we implemented a simulation system for sensor networks. But, we considered that the event node is stationary in the observation field. However, in many applications the event node may move. For example, in an ecology environment the animals can move randomly. In this work, we want to investigate how the sensor network performs in the case when the event node moves. We carried out the simulations for lattice topology and TwoRayGround radio model considering AODV and DSR protocols. We compare the simulation results for two cases: when the event node is mobile and stationary. The simulation results have shown that the routing efficiency for the case of mobile event node is better than the stationary event node using AODV protocol. Also, the goodput for the mobile event node case does not change too much compared with the stationary event case using AODV, but the goodput is not good when the number of nodes is increased.

We discuss the design and implementation of network and transport layer protocols for mobile networking. The network architecture used is unique in that it separates the mobile network(s) from fixed networks and provides connectivity between the two via special gateways. These gateways split all transport connections and provide QoS guarantees to mobile users for all their open connections. We provide summaries of our protocols and discuss possible improvements.

The next-generation electric power systems (smart grid) are studied intensively as a promising solution for energy crisis. One important feature of the smart grid is the integration of high-speed, reliable and secure data communication networks to manage the complex power systems effectively and intelligently. We provide in this paper a comprehensive survey on the communication architectures in the power systems, including the communication network compositions, technologies, functions, requirements, and research challenges. As these communication networks are responsible for delivering power system related messages, we discuss specifically the network implementation considerations and challenges in the power system settings. This survey attempts to summarize the current state of research efforts in the communication networks of smart grid, which may help us identify the research problems in the continued studies.

This paper describes the implementation and test of a control and data acquisition board designed to be integrated on systems demanding high availability and reliability, foreseen for future experiments like ITER or other long operation fusion devices. The Advanced Telecommunications Computing Architecture (ATCA) standard (PICMG 3.0 and 3.4) was selected for board implementation, which has support for the desired system robustness and performance. Some board features such as rear Input/Output (IO) signals connectivity (passive, copper tracks only), cable-less hot-swap maintenance, Intelligent Platform Management Controller (IPMC) and redundancy on timing signals, communications links and power supplies are significant board improvements, relatively to previous control and data acquisition boards, allowing the development of more reliable system architectures. Moreover, the developed board is also compatible with the emerging ATCA eXtensions for Instrumentation (AXIe) specifications, which provides additional timing and synchronization signals on the backplane. ATCA full-mesh, multi-gigabit, full-duplex, pointto-point communication links between Field Programmable Gate Arrays (FPGA), of peer boards inside the shelf, allow the implementation of distributed algorithms and development of Multi-Input Multi-Output (MIMO) systems. Up to 48 analog input channels, simultaneously digitized (2 MSPS @ 18-bits), are filtered/decimated by the board FPGA and sent to the ATCA/AXIe host through Peripheral Component Interconnect express (PCIe) using Direct Memory Access (DMA). In real-time, the host can update up to 48 analog output channels (1 MSPS @ 18-bits), per board, through PCIe. Further board characteristics comprise analog IO channels with galvanic isolation and an optional signal chopper mode, for offset compensation over time on digital integration of magnetic signals. Board time synchronization is attained by means of the Inter-Range Instrumentation Group (IRIG) time-code.

1976 TABLE I [14] J. C. Ashlock and S. M. Lurie, "On the application of extremevalue statistics to command oriented problems," Jet Propulsion Actual BER Estimated BER Lab.,Pasadena, CA,Tech. Rep. 32-1025, Oct. 15, 1966. [15] E. C. Posner, "The application of extreme-value theory to Prob. of False Alarm 0.22 X 10-3 10-3 error-free communication,"

Digital signal processors are highly used in a large variety of today's domestic and industrial applications. This paper emphasizes on the principles and techniques involved in professional audio processing field. Some basic digital audio effects are described along with the corresponding guidelines for DSP implementation.

In this paper, we present a machine-learning technique to counteract jamming attacks in underwater networks. Indeed, this is relevant in security applications where sensor devices are located in critical regions, for example, in the case of national border surveillance or for identifying any unauthorized intrusion. To this aim, a multi-hop routing protocol that relies on the exploitation of a Q-learning methodology is presented with a focus on increasing reliability in data communication and network lifetime. Performance results assess the effectiveness of the proposed solution as compared to other efficient state-of-the-art approaches.

The advent of high-speed networks has resulted in increased communication processing requirements. In order to meet this increase in processing requirements, a multiprocessing network interface is considered for processing multiple layers of a communication protocol stack. In particular, we consider the processing of layers 2 through 6 of open system interconnection (OSI) on the network interface. OS1 processing is computationally expensive because of the inclusion of the transfer syntax conversion at the presentation layer. The approach taken is to process different packets in parallel. The results obtained from simulations indicate that our approach has promise for OS1 processing at higher rates.

We consider models of N interacting objects, where the interaction is via a common resource and the distribution of states of all objects. We consider the case where the number of transitions per time slot per object vanishes as N grows. We show that, under mild assumptions and for large N , the occupancy measure converges, in probability and in mean square over any finite horizon, to a deterministic dynamical system. Our method of proof is inspired by stochastic approximation algorithms. The convergence results allow us to derive properties valid in the stationary regime. We use this to develop a critique of the fixed point method sometimes used in conjunction with the decoupling assumption.

L.0 is an executable specification language designed for describing communications protocols and similar reactive systems. L.0 is synchronous and rule-based. The rules are either cause-effect rules or constraints. Rules can be activated and deactivated dynamically. Several can be fired simultaneously. L.0 has modern notions of encapsulation and data sharing. Indirection, quantification, and recursive definition of modules increase its expressiveness. L.0 has been used in several development projects to design, simulate, and prototype protocols. It seems to provide a paradigm that is precise and yet can be used by designers and engineers who are not specialists in specification languages. This paper gives an overview of L.0 and its applications to protocols.

We propose two algorithms to form spanning trees in sensor networks. The first algorithm forms hierarchical clusters of spanning trees with a given root, the sink. All of the nodes in the sensor network are then classified iteratively as subroot, intermediate or leaf nodes. At the end of this phase, the local spanning trees are formed, each having a unique subroot (clusterhead) node. The communication and data aggregation towards the sink by an ordinary node then is accomplished by sending data to the local subroot which routes data towards the sink. A modified version of the first algorithm is also provided which ensures that the obtained tree is a breadth-first search tree where a node can modify its parent to yield shorter distances to the root. Once the subspanning trees in the clusters are formed, a communication architecture such as a ring can be formed among the subroots. This hybrid architecture which provides co-existing spanning trees within clusters yields the necessary foundation for a two-level communication protocol in a sensor network as well as providing a structure for a higher level abstraction such as the γ synchronizer where communication between the clusters is performed using the ring similar to an α synchronizer and the intra cluster communication is accomplished using the sub-spanning trees as in the β synchronizers. We discuss the model along with the algorithms, compare them and comment on their performances.

We study the problem of discrete distribution testing in the two-party setting. For example, in the standard closeness testing problem, Alice and Bob each have t samples from, respectively, distributions a and b over [n], and they need to test whether a = b or a, b are-far (in the 1 distance) for some fixed > 0. This is in contrast to the well-studied one-party case, where the tester has unrestricted access to samples of both distributions, for which optimal bounds are known for a number of variations. Despite being a natural constraint in applications, the two-party setting has evaded attention so far. We address two fundamental aspects of the two-party setting: 1) what is the communication complexity, and 2) can it be accomplished securely, without Alice and Bob learning extra information about each other's input. Besides closeness testing, we also study the independence testing problem, where Alice and Bob have t samples from distributions a and b respectively, which may be correlated; the question is whether a, b are independent of-far from being independent. Our contribution is threefold: • Communication: we show how to gain communication efficiency as we have more samples, beyond the information-theoretic bound on t. Furthermore, the gain is polynomially better than what one may obtain by adapting one-party algorithms. For the closeness testing, our protocol has communication s =Θ n 2 /t 2 as long as t is at least the information-theoretic minimum number of samples. For the independence testing over domain [n] × [m], where n ≥ m, we obtain s =Õ (n 2 m/t 2 + nm/t + √ m). • Lower bounds: we prove tightness of our trade-off for the closeness testing, as well as that the independence testing requires tight Ω(√ m) communication for unbounded number of samples. These lower bounds are of independent interest as, to the best of our knowledge, these are the first 2-party communication lower bounds for testing problems, where the inputs represent a set of i.i.d. samples. • Security: we define the concept of secure distribution testing and argue that it must leak at least some minimal information when the promise is not satisfied. We then provide secure versions of the above protocols with an overhead that is only polynomial in the security parameter.

The need for precision measurement of dc current in the nanoampere and picoampere ranges is continuously increasing. The present paper discusses in detail the establishment of measurement facility for the first time at NPLI for these low level DC current ranges by using primary measurement standards of DC voltage and DC resistance. The same has been implemented by developing the fully automated system. The automation provides an efficient way for the low level current measurement as measuring sub nanoampere current manually is subjected to various sources of errors. Introduction An accurate measurement of low currents down to pA range is in extreme need nowadays for the calibration of current detectors, picoamperemeters

The Planets Testbed, a key outcome of the EC co-funded Planets project, is a web based application that provides a controlled environment where users can perform experiments on a variety of preservation tools using sample data and a standardised yet configurable experiment methodology. Development of the Testbed required the close participation of many geographically and strategically disparate organisations throughout the four-year duration of the project, and this paper aims to reflect on a number of key ...

We present an approach for applying symmetry reduction techniques to probabilistic model checking, a formal verification method for the quantitative analysis of systems with stochastic characteristics. We target systems with a set of non-trivial, but interchangeable, components such as those which commonly arise in randomised distributed algorithms or probabilistic communication protocols. We show, for three types of probabilistic models, that symmetry reduction, similarly to the non-probabilistic case, allows verification to instead be performed on a bisimilar quotient model which may be up to factorially smaller. We then propose an efficient algorithm for the construction of the quotient model using a symbolic implementation based on multi-terminal binary decision diagrams (MTBDDs) and, using four large case studies, demonstrate that this approach offers not only a dramatic increase in the size of probabilistic model which can be quantitatively analysed but also a significant decrease in the corresponding run-times.

Deriving test cases from formal specifications of communicating processes has been studied for a while. Several methods have been proposed for specifications based on FSM (Finite State Machines), LTS (Labelled Transition Systems), IOTS (Input Output Transition Systems), etc. However, most approaches are limited to a finite set of actions, excluding the possibility of communicating typed values between processes. This article presents a test derivation and selection method based on a model of communicating processes with inputs, outputs and data types, which is closer to actual implementations of communication protocols.

There has been a lot of research on testing based on formal specifications, especially in the area of communication protocols. Most approaches take as starting point some finite model of the required behaviours of the system under test, such as Finite State Machines. This paper discusses the problems that arise when the underlying model of the specification is not finite.

Para la realización del análisis de un protocolo de comunicaciones en una red de tipo Ad Hoc es necesario incluir en el modelo no solamente las características internas del protocolo sino, además, el contexto propio bajo el cual se desenvuelve. En la evaluación de su desempeño, en consecuencia, el protocolo debería ser probado en condiciones en las que se incluyan movimientos realistas de los usuarios móviles. En este artículo se revisan varios modelos de movilidad que fueron usados en la experimentación. Dado que resulta muy costoso realizar la evaluación sobre una red Ad Hoc real, se optó por una técnica basada en simulación que permitió extraer las conclusiones de esta investigación. Dentro de los modelos de movilidad usados se encuentran aquellos que representan nodos móviles cuyo movimiento es mutuamente independiente y modelos de movilidad que representan nodos móviles cuyos movimientos son interdependientes. Se presentan algunos resultados de la simulación en NS-2 que ilustra...

In this paper, we study the verification of dense time properties by discrete time analysis. Interval Duration Logic, (IDL), is a highly expressive dense time logic for specifying properties of real-time systems. Validity checking of IDL formulae is in general undecidable. A corresponding discrete-time logic QDDC has decidable validity. In this paper, we consider a reduction of IDL validity question to QDDC validity using notions of digitization. A new notion of Strong Closure under Inverse Digitization, SCID, is proposed. For all SCID formulae, the dense and the discrete-time validity coincide. Moreover, SCID has good algebraic properties which can be used to conveniently prove that many IDL formulae are SCID. We also give some approximation techniques to strengthen/weaken formulae to SCID form. For SCID formulae, the validity of dense-time IDL formulae can be checked using the validity checker for discrete-time logic QDDC. This work was partly carried out under the VSRP program of TIFR, Mumbai.