Abstract: Event processing will play an increasingly important role in constructing enterprise applications that can immediately react to business critical events. Various technologies have been proposed in recent years, such as event processing, data streams and asynchronous messaging (e.g. pub/sub). We believe these technologies share a common processing model and differ only in target workload, including query language features and consistency requirements. We argue that integrating these technologies is the next step in a natural progression. In this paper, we present an overview and discuss the foundations of CEDR, an event streaming system that embraces a temporal stream model to unify and further enrich query language features, handle imperfections in event delivery, define correctness guarantees, and define operator semantics. We describe specific contributions made so far and outline next steps in developing the CEDR system.

Abstract: A system and method including asynchronous location-based messaging is provided. Multimedia content may be created and associated with a specific geographic location. Notification messages associated with location-based content may be designated for receipt by particular users, for example, when the users are located within a predetermined distance of the geographic location. The notification messages, which may be transmitted to users' mobile computing devices, may include information about, as well as a pointer to, the location-based content to enable the content to be accessed immediately or at a later time through any number of interfaces.

Abstract: Distributed systems are often modeled by objects that run concurrently, each with its own processor, and communicate by synchronous remote method calls. This may be satisfactory for tightly coupled systems, but in the distributed setting synchronous external calls lead to much waiting; at best resulting in inefficient use of processor capacity, at worst resulting in deadlock. Furthermore, it is difficult to combine active and passive behavior in concurrent objects. This paper proposes an object-oriented solution to these problems by means of asynchronous method calls and conditional processor release points. Although at the cost of additional internal nondeterminism in the objects, this approach seems attractive in asynchronous or unreliable environments. The concepts are integrated in a small object-oriented language with an operational semantics defined in rewriting logic, and illustrated by examples.

Abstract: Single-clocked digital systems are largely a thing of the past. Although most digital circuits remain synchronous, many designs feature multiple clock domains, often running at different frequencies. Using an asynchronous interconnect decouples the timing issues for the separate blocks. Systems employing such schemes are called globally asynchronous, locally synchronous (GALS). To minimize time to market, large SoC designs must integrate many functional blocks with minimal design effort. These blocks are usually designed using standard synchronous methods and often have different clocking requirements. A GALS approach can facilitate fast block reuse by providing wrapper circuits to handle interblock communication across clock domain boundaries. SoCs may also achieve power savings by clocking different blocks at their minimum speeds. For example, Scott et al. describe the advantages of GALS design for an embedded-processor peripheral bus.

Abstract: The issues of applying the code-division multiple access (CDMA) technique to an on-chip packet switched communication network are discussed in this paper. A packet switched network-on-chip (NoC) that applies the CDMA technique is realized in register-transfer level (RTL) using VHDL. The realized CDMA NoC supports the globally-asynchronous locally-synchronous (GALS) communication scheme by applying both synchronous and asynchronous designs. In a packet switched NoC, which applies a point-to-point connection scheme, e.g., a ring topology NoC, data transfer latency varies largely if the packets are transferred to different destinations or to the same destination through different routes in the network. The CDMA NoC can eliminate the data transfer latency variations by sharing the data communication media among multiple users concurrently. A six-node GALS CDMA on-chip network is modeled and simulated. The characteristics of the CDMA NoC are examined by comparing them with the characteristics of an on-chip bidirectional ring topology network. The simulation results reveal that the data transfer latency in the CDMA NoC is a constant value for a certain length of packet and is equivalent to the best case data transfer latency in the bidirectional ring network when data path width is set to 32 bits.

Abstract: An electronic circuit for use with time of arrival signals from a network, including a position determination unit, a first clock, a second clock, and processing circuitry coupled to said first clock, said second clock, and said position determination unit. The processing circuitry is operable to project a relatively-accurate subsequent global time based on said first and second clocks and to then return said relatively-accurate subsequent global time to said position determination unit to facilitate a subsequent position determination by said position determination unit.

Abstract: In wireless sensor networks there is a need to securely store monitored data in a distributed way whenever it is either not desired or simply not possible to transmit regional volatile information to an authorised recipient in real-time. In particular, for wireless sensor network applications with an asynchronous character, the wireless sensor network itself needs to store the monitored data. Since nodes may disappear over time, a replicated and read-protected, but yet space- and energy-efficient, data storage is mandatory. In this work we provide and analyse an approach for a tiny Persistent Encrypted Data Storage (tinyPEDS) of the environmental fingerprint for asynchronous wireless sensor networks. Even if parts of the network are exhausted, restoring rules ensure that, with a high probability, environmental information from past is still available.

Abstract: This paper is concerned with the optimal dynamic information fusion problem for asynchronous multirate multisensors By establishing the state space models at each scale, a novel algorithm is developed to recursively fuse the data from multisensors, where the ratio between the sampling rates of different sensors is allowed to be any positive integer Without using the traditional interpolation or augmentation approaches for states or measurements, the state estimate is obtained based on global measurements, and the obtained state estimate is then proven to be the optimal in the sense of linear minimum variance It is shown that our main results improve and extend the existing information fusion algorithms for which the sampling rate ratio of different sensors is restricted to one or a power of two Finally, the feasibility and efficiency of the proposed algorithm is illustrated by a numerical simulation example

Abstract: A high definition video transmitter and receiver are disclosed. The transmitter provides high definition video to a one-point receiver or to multipoint receivers. The transmission network is asynchronous and the receiver re-synchronizes the video. The transmission can be wired or wireless.

Abstract: We define reactive simulatability for general asynchronous systems. Roughly, simulatability means that a real system implements an ideal system (specification) in a way that preserves security in a general cryptographic sense. Reactive means that the system can interact with its users multiple times, e.g., in many concurrent protocol runs or a multi-round game. In terms of distributed systems, reactive simulatability is a type of refinement that preserves particularly strong properties, in particular confidentiality. A core feature of reactive simulatability is composability, i.e., the real system can be plugged in instead of the ideal system within arbitrary larger systems; this is shown in follow-up papers, and so is the preservation of many classes of individual security properties from the ideal to the real systems. A large part of this paper defines a suitable system model. It is based on probabilistic IO automata (PIOA) with two main new features: One is generic distributed scheduling. Important special cases are realistic adversarial scheduling, procedure-call-type scheduling among colocated system parts, and special schedulers such as for fairness, also in combinations. The other is the definition of the reactive runtime via a realization by Turing machines such that notions like polynomial-time are composable. The simple complexity of the transition functions of the automata is not composable. As specializations of this model we define security-specific concepts, in particular a separation between honest users and adversaries and several trust models. The benefit of IO automata as the main model, instead of only interactive Turing machines as usual in cryptographic multi-party computation, is that many cryptographic systems can be specified with an ideal system consisting of only one simple, deterministic IO automaton without any cryptographic objects, as many follow-up papers show. This enables the use of classic formal methods and automatic proof tools for proving larger distributed protocols and systems that use these cryptographic systems.

Abstract: There are many asynchronous communication situations for which the prevalent continuous connectivity paradigm is not needed. Communication with a fair delay tolerance may instead be provided by intermittent store-and-forwarding between nodes. This paper proposes a design for an open, receiver-driven broadcasting system that relies on delay-tolerant forwarding of data chunks through mobility of wireless nodes. The system provides public broadcast channels, which may be openly used for both transmission and reception. We show by analysis and simulation under benchmark mobility models that a delay-tolerant broadcast channel has both a sufficiently high throughput and reach to be interesting as a competitive alternative to the regulated wireless broadcast channel. The analysis is based on a queuing model to study the interactions among the mobile nodes in a street. The simulations complement this analysis for mobile nodes moving on a square according to benchmark mobility models. Finally, we present the design of, and experiences with, a proof-of-concept prototype

Abstract: INTRODUCTION ITERATIVE ALGORITHMS Basic theory Sequential iterative algorithms A classical illustration example ITERATIVE ALGORITHMS AND APPLICATIONS TO NUMERICAL PROBLEMS Systems of linear equations Nonlinear equation systems Exercises PARALLEL ARCHITECTURES AND ITERATIVE ALGORITHMS Historical context Parallel architectures Trends of used configurations Classification of parallel iterative algorithms SYNCHRONOUS ITERATIONS Parallel linear iterative algorithms for linear systems Nonlinear systems: parallel synchronous Newton-multisplitting algorithms Preconditioning Implementation Convergence detection Exercises ASYNCHRONOUS ITERATIONS Advantages of asynchronous algorithms Mathematical model and convergence results Convergence situations Parallel asynchronous multisplitting algorithms Coupling Newton and multisplitting algorithms Implementation Convergence detection Exercises PROGRAMMING ENVIRONMENTS AND EXPERIMENTAL RESULTS Implementation of AIAC algorithms with nondedicated environments Two environments dedicated to asynchronous iterative algorithms Ratio between computation time and communication time Experiments in the context of linear systems Experiments in the context of partial differential equations using a finite difference scheme APPENDIX: DIAGONAL DOMINANCE AND IRREDUCIBLE MATRICES Z-matrices, M-matrices, and H-matrices Perron-Frobenius theorem Sequences and sets REFERENCES INDEX

Abstract: An optical transmission network is inherently asynchronous due to the utilization of a variable overhead ratio (V-OHR). The network architecture makes extensive use of OEO regeneration, i.e., deals with any electronic reconditioning to correct for transmission impairments, such as, for example, FEC encoding, decoding and re-encoding, signal reshaping, retiming as well as signal regeneration. The optical transmission network includes a plesiochronous clocking system with intermediate nodes designed to operate asynchronously with a single local frequency clock without complicated network synchronization schemes employing high cost clocking devices such as phase locked loop (PLL) control with crystal oscillators and other expensive system components. The asynchronous network operation provides for asynchronous remapping or remapping of any client signal utilizing any type of transmission protocol where the line side rate or frequency is always the same frequency for the payload signal and the local frequency at an intermediate node is set to a local reference clock in accordance with the payload type and its overhead ratio, i.e., the overhead ratio is varied to meet the desired difference between the line rate or frequency and the desired client signal payload rate or frequency for the particular client signal payload type.

Abstract: An asynchronous program is one that contains procedure calls which are not immediately executed from the callsite, but stored and "dispatched" in a non-deterministic order by an external scheduler at a later point. We formalize the problem of interprocedural dataflow analysis for asynchronous programs as AIFDS problems, a generalization of the IFDS problems for interprocedural dataflow analysis. We give an algorithm for computing the precise meet-over-valid-paths solution for any AIFDS instance, as well as a demand-driven algorithm for solving the corresponding demand AIFDS instances. Our algorithm can be easily implemented on top of any existing interprocedural dataflow analysis framework. We have implemented the algorithm on top of BLAST, thereby obtaining the first safety verification tool for unbounded asynchronous programs. Though the problem of solving AIFDS instances is EXPSPACE-hard, we find that in practice our technique can efficiently analyze programs by exploiting standard optimizations of interprocedural dataflow analyses.

Abstract: Synchronization of relay nodes is an important and critical issue in exploiting cooperative diversity in wireless networks. In this paper, two asynchronous cooperative diversity schemes are proposed, namely, distributed delay diversity and asynchronous space-time coded cooperative diversity schemes. In terms of the overall diversity-multiplexing (DM) tradeoff function, we show that the proposed independent coding based distributed delay diversity and asynchronous space-time coded cooperative diversity schemes achieve the same performance as the synchronous space-time coded approach which requires an accurate symbol-level timing synchronization to ensure signals arriving at the destination from different relay nodes are perfectly synchronized. This demonstrates diversity order is maintained even at the presence of asynchronism between relay node. Moreover, when all relay nodes succeed in decoding the source information, the asynchronous space-time coded approach is capable of achieving better DM tradeoff than synchronous schemes and performs equivalently to transmitting information through a parallel fading channel as far as the DM tradeoff is concerned. Our results suggest the benefits of fully exploiting the space-time degrees of freedom in multiple antenna systems by employing asynchronous space-time codes even in a frequency-flat-fading channel. In addition, it is shown asynchronous space-time coded systems are able to achieve higher mutual information than synchronous space-time coded systems for any finite signal-to-noise ratio (SNR) when properly selected baseband waveforms are employed.

Abstract: A robust, scalable, and power efficient dual-clock first-input first-out (FIFO) architecture which is useful for transferring data between modules operating in different clock domains is presented. The architecture supports correct operation in applications where multiple clock cycles of latency exist between the data producer, FIFO, and the data consumer; and with arbitrary clock frequency changes, halting, and restarting in either or both clock domains. The architecture is demonstrated in both a 0.18- mum CMOS full-custom design and a 0.18-mum CMOS standard cell design used in a globally asynchronous locally synchronous array processor. It achieves 580-MHz operation and 10.3-mW power dissipation while performing simultaneous FIFO read and write operations at 1.8 V.

Abstract: Purpose – Effective teams use a balance of synchronous and asynchronous communication. Team communication is dependent on the communication acts of team members and the ability of managers to facilitate, stimulate and motivate them. Team members from organizations using different information systems tend to have different understanding, opinions, and rates of adoption and skills levels regarding specific IT tools. The purpose of this paper is to explore the effective use of tools for communication in design teams and the strategies for the use of specific tools.Design/methodology/approach – A review of the potential effectiveness of synchronous and asynchronous communication means and tools for team communication leads to a review of research conducted into the use of two relatively new electronic tools for team communication by design teams in The Netherlands.Findings – The research results revealed that a collective framework for team communication and collaboration using electronic tools was missing. T...

Abstract: Communication is a key factor in team performance, successful project completion, and effective project management. Collective asynchronous electronic messages on task and coordination sent among m...

Abstract: The article examines the two distinct modes of text-based discussion in computer-mediated communication: synchronous (real time) and asynchronous (delayed time). How these two forms impact student cognitive and affective outcomes in a learning environment is considered. The substance of the research concerns an educational psychology course where both synchronous web chat-style discussion and asynchronous web post-style discussion was used. The results of a student survey show that the type of discussion used did not have a demonstrable effect on student test performance.

Abstract: The FAUST chip integrates a baseband processing architecture in which communications between IPs are supported by an asynchronous network-on-chip (NoC). This distributed and modular structure facilitates physical implementation and power management. A 20-node NoC is implemented in 79.5mm2 using 0.13mum 6M CMOS to address 100Mb/s telecom systems

Abstract: This paper introduces a high-throughput asynchronous pipeline style, called high-capacity (HC) pipelines, targeted to datapaths that use dynamic logic. This approach includes a novel highly-concurrent handshake protocol, with fewer synchronization points between neighboring pipeline stages than almost all existing asynchronous dynamic pipelining approaches. Furthermore, the dynamic pipelines provide 100% buffering capacity, without explicit latches, by means of separate pullup and pulldown control for each pipeline stage: neighboring stages can store distinct data items, unlike almost all existing latchless dynamic asynchronous pipelines. As a result, very high throughput is obtained. Fabricated first-input-first-output (FIFO) designs, in 0.18-m technology, were fully functional over a wide range of supply voltages (1.2 to over 2.5 V), exhibiting a corresponding range of throughputs from 1.0-2.4 giga items/s. In addition, an experimental finite-impulse response (FIR) filter chip was designed and fabricated with IBM Research, whose speed-critical core used an HC pipeline. The HC pipeline exhibited throughputs up to 1.8 giga items/s, and the overall filter achieved 1.32 giga items/s, thus obtaining 15% higher throughput and 50% lower latency than the fastest previously-reported synchronous FIR filter, also designed at IBM Research.

Abstract: A first wireless node may synchronize its timeslots with the timeslots of a second wireless node that was previously transmitting and receiving data in an asynchronous manner with respect to the timeslots of the first wireless node. By synchronizing timeslots, the wireless nodes may avoid interference that may otherwise occur if the wireless nodes operate in an asynchronous manner. A wireless node shares its timing information with other wireless nodes by repeatedly transmitting timing reference signals in conjunction with a synchronization metric that defines the relative priority of the timing reference. In the event a wireless node does not receive a GPS-based timing reference, the wireless node may synchronize to a timing reference based on the parameters of the synchronization metric of that timing reference. In the event a wireless node does not receive any timing references, the wireless node may define and advertise it's a timing reference and associated synchronization metric. To avoid synchronization race conditions, the synchronization metrics may be defined such that wireless nodes that have different timing references will advertise different synchronization metrics.

Abstract: In this paper, we introduce a new model for the representation of distributed asynchronous implementations of synchronous specifications. The model covers classical implementations, where a notion of global synchronization is preserved by means of signaling, and globally asynchronous, locally synchronous (GALS) implementations where the global clock is removed. The new model offers a unified framework for reasoning about two essential correctness properties of an implementation: the preservation of semantics and the absence of deadlocks. We use it to derive criteria ensuring the correct deployment of synchronous specifications over GALS architectures. As the model captures the internal concurrency of the synchronous specification, our criteria support implementations that are less constrained and more efficient than existing ones. Our work also reveals strong ties between abstract semantics-preservation properties and more operational ones like the absence of deadlocks.

Abstract: This paper presents a simple framework unifying a family of consensus algorithms that can tolerate process crash failures and asynchronous periods of the network, also called indulgent consensus algorithms Key to the framework is a new abstraction we introduce here, called Alpha, and which precisely captures consensus safety Implementations of Alpha in shared memory, storage area network, message passing and active disk systems are presented, leading to directly derived consensus algorithms suited to these communication media The paper also considers the case where the number of processes is unknown and can be arbitrarily large

Abstract: New media such as email and mobile phones have made it easier to maintain relationships over distances. The present paper examines which media people use to maintain long-distance friendships. The main focus lies on the comparison of email and phone. Media choice theories like media richness theory assume that media can be classified according to their richness, and that people choose the medium which fits best to the affordances of a specific task. The phone as richer medium should be preferred over email in the case of maintenance of long-distance friendships because it is easier to express emotions and to give immediate feedback via phone than via email. Email is an asynchronous medium and communication via email is therefore independent of space and time. Therefore, it can also be argued that email is preferred over the phone because it makes it easier to communicate across different work schedules or even time-zones. In two studies (Study 1 conducted in the Netherlands, Study 2 conducted in Germany) ...

Abstract: New and improved methods and circuit designs for asynchronous circuits that are tolerant to transient faults, for example of the type introduced through radiation or, more broadly, single-event effects. SEE-tolerant configurations are shown and described for combinational logic circuits, state-holding logic circuits and SRAM memory circuits.

Abstract: Secure multi-party computation (MPC) allows a set of n players to securely compute an agreed function of their inputs, even when up to t players are under the control of an adversary. Known asynchronous MPC protocols require communication of at least Ω(n3) (with cryptographic security), respectively Ω(n4) (with information-theoretic security, but with error probability and non-optimal resilience) field elements per multiplication. We present an asynchronous MPC protocol communicating O(n3) field elements per multiplication. Our protocol provides perfect security against an active, adaptive adversary corrupting t < n/4 players, which is optimal. This communication complexity is to be compared with the most efficient previously known protocol for the same model, which requires Ω(n5) field elements of communication (i.e., Ω(n3) broadcasts). Our protocol is as efficient as the most efficient perfectly secure protocol for the synchronous model and the most efficient asynchronous protocol with cryptographic security. Furthermore, we enhance our MPC protocol for a hybrid model. In the fully asynchronous model, up to t honest players might not be able to provide their input in the computation. In the hybrid model, all players are able to provide their input, given that the very first round of communication is synchronous. We provide an MPC protocol with communicating O(n3) field elements per multiplication, where all players can provide their input if the first communication round turns out to be synchronous, and all but at most t players can provide their input if the communication is fully asynchronous. The protocol does not need to know whether or not the first communication round is synchronous, thus combining the advantages of the synchronous world and the asynchronous world. The proposed MPC protocol is the first protocol with this property.

Abstract: The paper presents a novel approach based on Bogor for the accurate verification of applications based on Publish- Subscribe infrastructures. Previous efforts adopted standard model checking techniques to verify the application behavior, but they introduce strong simplifications on the underlying infrastructure to cope with the state space explosion problem and make automatic verification feasible. Instead of building on top of existing model checkers, our proposal embeds the asynchronous communication mechanisms of Publish-Subscribe infrastructures within Bogor. This way, Publish-Subscribe primitives become part of the specification language as additional, domain-specific, constructs. Accurate models become feasible without incurring in state space explosion problems, thus enabling the automated verification of applications on top of realistic communication infrastructures.