Showing papers on "Latency (engineering) published in 2003"

Herpes Simplex Virus Type 1 and Bovine Herpesvirus 1 Latency

Abstract: Primary infection by herpes simplex virus type 1 (HSV-1) can cause clinical symptoms in the peripheral and central nervous system, upper respiratory tract, and gastrointestinal tract. Recurrent ocular shedding leads to corneal scarring that can progress to vision loss. Consequently, HSV-1 is the leading cause of corneal blindness due to an infectious agent. Bovine herpesvirus 1 (BHV-1) has similar biological properties to HSV-1 and is a significant health concern to the cattle industry. Latency of BHV-1 and HSV-1 is established in sensory neurons of trigeminal ganglia, but latency can be interrupted periodically, leading to reactivation from latency and spread of infectious virus. The ability of HSV-1 and BHV-1 to reactivate from latency leads to virus transmission and can lead to recurrent disease in individuals latently infected with HSV-1. During latency, the only abundant HSV-1 RNA expressed is the latency-associated transcript (LAT). In latently infected cattle, the latency-related (LR) RNA is the only abundant transcript that is expressed. LAT and LR RNA are antisense to ICP0 or bICP0, viral genes that are crucial for productive infection, suggesting that LAT and LR RNA interfere with productive infection by inhibiting ICP0 or bICP0 expression. Numerous studies have concluded that LAT expression is important for the latency-reactivation cycle in animal models. The LR gene has recently been demonstrated to be required for the latency-reactivation cycle in cattle. Several recent studies have demonstrated that LAT and the LR gene inhibit apoptosis (programmed cell death) in trigeminal ganglia of infected animals and transiently transfected cells. The antiapoptotic properties of LAT map to the same sequences that are necessary for promoting reactivation from latency. This review summarizes our current knowledge of factors regulating the latency-reactivation cycle of HSV-1 and BHV-1.

Effect of latency on presence in stressful virtual environments

Abstract: Previous research has shown that even low end-to-end latency can have adverse effects on performance in virtual environments (VE). This paper reports on an experiment investigating the effect of latency on other metrics of VE effectiveness: physiological response, simulator sickness, and self-reported sense of presence. The VE used in the study includes two rooms: the first is normal and non-threatening; the second is designed to evoke a fear/stress response. Participants were assigned to either a low latency (/spl sim/50 ms) or high latency (/spl sim/90 ms) group. Participants in the low latency condition had a higher self-reported sense of presence and a statistically higher change in heart rate between the two rooms than did those in the high latency condition. There were no significant relationships between latency and simulator sickness.

Latency Compensating Methods in Client/Server In-game Protocol Design and Optimization

Abstract: Overview: Designing first-person action games for Internet play is a challenging process. Having robust on-line gameplay in your action title, however, is becoming essential to the success and longevity of the title. In addition, the PC space is well known for requiring developers to support a wide variety of customer setups. Often, customers are running on less than state-of-the-art hardware. The same holds true for their network connections. While broadband has been held out as a panacea for all of the current woes of on-line gaming, broadband is not an simple solution allowing developers to ignore the implications of latency and other network factors in game designs. It will be some time before broadband truly becomes adopted the United States, and much longer before it can be assumed to exist for your clients in the rest of the world. In addition, there are a lot of poor broadband solutions, where users may occasionally have high bandwidth, but more often than not also have significant latency and packet loss in their connections. Your game must to behave well in this world. This discussion will give you a sense of some of the tradeoffs required to deliver a cutting-edge action experience on the Internet. The discussion will provide some background on how client / server architectures work in many on-line action games. In addition, the discussion will show how predictive modeling can be used to mask the effects of latency. Finally, the discussion will describe a specific mechanism, lag compensation, for allowing the game to compensate for connection quality. Most action games played on the net today are modified client / server games. Games such as Half-Life, including its mods such as Counter-Strike and Team Fortress Classic, operate on such a system, as do games based on the Quake3 engine and the Unreal Tournament engine. In these games, there is a single, authoritative server that is responsible for running the main game logic. To this are connected one or more " dumb " clients. These clients, initially, were nothing more than a way for the user input to be sampled and forwarded to the server for execution. The server would execute the input commands, move around other objects, and then send back to the client a list of objects to render. Of course, the real world system has more components to it, but the simplified breakdown is useful for thinking about prediction …

The effect of latency on user performance in Warcraft III

Abstract: Latency on the Internet is a well-known problem for interactive applications. With the increase in interactive network games comes the increased importance of understanding the effects of latency on user performance. Classes of network games such as First Person Shooters (FPS) and Real Time Strategy (RTS) differ in their user interaction model and hence susceptibility to latency. While previous work has measured the effects of latency on FPS games, there has been no systematic investigation of the effects of latency on RTS games. In this work, we design and conduct user studies that measure the impact of latency on user performance in Warcraft III, a popular RTS game. As a foundation for the research, we separated typical Warcraft III user interactions into the basic components of explore, build and combat, and analyzed each individually. We find modest statistical correlations between user performance and latency for exploration, but very weak correlations for building and combat. Overall, the effect of even very high latency, while noticeable to users, has a negligible effect on the outcome of the game. We attribute this somewhat surprising result to the nature of RTS game-play that clearly favors strategy over the real-time aspects.

Paths, trees, and minimum latency tours

Abstract: We give improved approximation algorithms for a variety of latency minimization problems. In particular, we give a 3.59-approximation to the minimum latency problem, improving on previous algorithms by a multiplicative factor of 2. Our techniques also give similar improvements for related problems like k-traveling repairmen and its multiple depot variant. We also observe that standard techniques can be used to speed up the previous and this algorithm by a factor of O/sup /spl tilde//(n).

System and method for measuring and recording latency in internet protocol networks

Abstract: A system and method for measuring and recording latency in data networks. The system and method can be used to measure and record latency in a Simple IP network or a Mobile IP network. One embodiment of the present invention is a system and method for measuring latency between a first device and a second device, the first and second devices communicating in accordance with a communications specification. The system and method comprises the second device transmitting, during a communication session, a message to the first device; receiving a response message from the first device; computing an elapsed time from transmission of the message to receipt of the response message to determine the latency; and recording the latency in a latency parameter. The message and the response message are provided by the communications specification.

Method and apparatus for remote real time collaborative music performance

Abstract: A method and apparatus are disclosed to permit distributed performance by multiple musicians at remote locations The latency of the communication channel (150) is transferred to the behavior of the local instrument (180) so that a natural accommodation is made by the musician This allows musical events that actually occur simultaneously at remote locations to be played together at each location, though not necessarily simultaneously at all locations This allows locations having low latency connections to retain some of their advantage The amount of induced latency can be overridden by each musician

Using destination-set prediction to improve the latency/bandwidth tradeoff in shared-memory multiprocessors

Abstract: Destination-set prediction can improve the latency/bandwidth tradeoff in shared-memory multiprocessors The destination set is the collection of processors that receive a particular coherence request Snooping protocols send requests to the maximal destination set (ie, all processors), reducing latency for cache-to-cache misses at the expense of increased traffic Directory protocols send requests to the minimal destination set, reducing bandwidth at the expense of an indirection through the directory for cache-to-cache misses Recently proposed hybrid protocols trade-off latency and bandwidth by directly sending requests to a predicted destination setThis paper explores the destination-set predictor design space, focusing on a collection of important commercial workloads First, we analyze the sharing behavior of these workloads Second, we propose predictors that exploit the observed sharing behavior to target different points in the latency/bandwidth tradeoff Third, we illustrate the effectiveness of destination-set predictors in the context of a multicast snooping protocol For example, one of our predictors obtains almost 90% of the performance of snooping while using only 15% more bandwidth than a directory protocol (and less than half the bandwidth of snooping)

Disk drive employing a modified rotational position optimization algorithm to account for external vibrations

Abstract: A disk drive is disclosed which executes a rotational position optimization (RPO) algorithm to select a next command to execute from a command queue relative to an estimated access time. If an external vibration is detected, the RPO algorithm increases at least one of an estimated seek latency, an estimated settle latency, and an estimated rotational latency for each command in the command queue.

Methods and apparatus for characterizing a route in a fibre channel fabric

Abstract: Methods and apparatus are provided for determining characteristics associated with routes in fibre channel networks. Techniques are provided for inserting time stamp information into frames transmitted from a source to a destination and back to the source. Time stamp information allows a supervisor associated with a source to determine characteristics such as round trip times, latency between hops, and connectivity to a destination for specific routes.

Head Tracking Latency in Virtual Environments: Psychophysics and a Model:

Abstract: Quantification of perceptual sensitivity to latency in virtual environments (VEs) and elucidation of the mechanism by which latency is perceived is essential for development of countermeasures by VE designers. We test the hypothesis that observers use “image slip” (i.e., motion of the VE scene caused by system time lags) to detect the consequences of latency rather than explicitly detecting time delay. Our presumption is that forcing observers to change from constant rate to randomly paced head motion will disrupt their ability to discriminate latency based on perceived image slip. This study indicates that the disruption in motion pattern causes a shift in latency detection criteria and a minor degradation in discrimination ability. It is likely therefore that observers make at least some use of image slip in discriminating VE latency. It can also be inferred that when observers learn to discriminate latency, their Just Noticeable Difference (JND) remains below 17 ms.

Pass through circuit for reduced memory latency in a multiprocessor system

Abstract: A technique and mechanism for reducing memory latency asymmetry in a multiprocessor system by replacing one (or more) processors with a bypass or pass-through device. Using the pass-through mechanism, the reduced number of processors in the system enables all of the remaining processors to connect to each other directly using the interconnect links. The reduction in processor count improves symmetry and reduces overall latency thereby potentially improving performance of certain applications despite having fewer processors. In one specific implementation, the pass through device is used to connect two HyperTransport links together where each of the links is connected to a processor at the other end.

Incrementally improving lookup latency in distributed hash table systems

Abstract: Distributed hash table (DHT) systems are an important class of peer-to-peer routing infrastructures. They enable scalable wide-area storage and retrieval of information, and will support the rapid development of a wide variety of Internet-scale applications ranging from naming systems and file systems to application-layer multicast. DHT systems essentially build an overlay network, but a path on the overlay between any two nodes can be significantly different from the unicast path between those two nodes on the underlying network. As such, the lookup latency in these systems can be quite high and can adversely impact the performance of applications built on top of such systems.In this paper, we discuss a random sampling technique that incrementally improves lookup latency in DHT systems. Our sampling can be implemented using information gleaned from lookups traversing the overlay network. For this reason, we call our approach lookup-parasitic random sampling (LPRS). LPRS is fast, incurs little network overhead, and requires relatively few modifications to existing DHT systems.For idealized versions of DHT systems like Chord, Tapestry and Pastry, we analytically prove that LPRS can result in lookup latencies proportional to the average unicast latency of the network, provided the underlying physical topology has a power-law latency expansion. We then validate this analysis by implementing LPRS in the Chord simulator. Our simulations reveal that LPRS-Chord exhibits a qualitatively better latency scaling behavior relative to unmodified Chord.Finally, we provide evidence which suggests that the Internet router-level topology resembles power-law latency expansion. This finding implies that LPRS has significant practical applicability as a general latency reduction technique for many DHT systems. This finding is also of independent interest since it might inform the design of latency-sensitive topology models for the Internet.

Establishment and Maintenance of Gammaherpesvirus Latency Are Independent of Infective Dose and Route of Infection

Abstract: Gammaherpesviruses such as Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus are important human pathogens that establish long-term latent infections. Understanding of the initiation and maintenance of latent infections has important implications for the prevention and treatment of gammaherpesvirus-related diseases. Although much is known about gammaherpesvirus pathogenesis, it is unclear how the infectious dose of a virus influences its ability to establish latent infection. To examine the relationship between the infectious dose and gammaherpesvirus latency, we inoculated wild-type mice with 0.01 to 106 PFU of murine gammaherpesvirus 68 (γHV68) and quantitatively measured latency and acute-phase replication. Surprisingly, during latency, the frequencies of ex vivo reactivation were similar over a 107-fold range of doses for i.p. infection and over a 104-fold range of doses for intranasal infection. Further, the frequencies of cells harboring viral genome during latency did not differ substantially over similar dose ranges. Although the kinetics of acute-phase replication were delayed at small doses of virus, the peak titer did not differ significantly between mice infected with a large dose of virus and those infected with a small dose of virus. The results presented here indicate that any initiation of infection leads to substantial acute-phase replication and subsequent establishment of a maximal level of latency. Thus, infections with doses as small as 0.1 PFU of γHV68 result in stable levels of acute-phase replication and latent infection. These results demonstrate that the equilibrium level of establishment of gammaherpesvirus latency is independent of the infectious dose and route of infection.

Differential γ-Herpesvirus Distribution in Distinct Anatomical Locations and Cell Subsets During Persistent Infection in Mice

Abstract: Murine γ-herpesvirus 68 (MHV-68) provides an important experimental model for analyzing γ-herpesvirus latent infection. After intranasal infection with MHV-68, we analyzed the distribution of the virus in different anatomical locations and purified populations of cells. Our data show that long-term latency is maintained in a variety of anatomical locations and cell populations with different frequencies. Importantly, we demonstrate that although latency in the lung is established in a variety of cell subsets, long-term latency in the lung is only maintained in B cells. In contrast, splenic latency is maintained in macrophages and dendritic cells, as well as in B cells. In blood, isotype-switched B cells constitute the major viral reservoir. These results show that the cell subsets in which latency is established vary within different anatomical sites. Finally, we demonstrate that long-term latency is accompanied by a low level of infectious virus in lung and spleen. These data have important implications for understanding the establishment and maintenance of latency by γ 2 -herpesviruses.

Method and system for selectivity reducing call-setup latency through management of paging frequency

Abstract: A method and system for selectively reducing call-setup latency. The method and system provides for selectively increasing the paging frequency used for paging certain mobile stations, so as to decrease the time that it takes to establish radio-link connectivity with those mobile stations. The method and system is particularly useful when establishing real-time communication sessions, such as instant chat sessions, but may be useful in other scenarios as well.

Quality of service controller and method for a data storage system

Abstract: A quality-of-service controller and related method for a data storage system. Requests for each of a plurality of storage system workloads are prioritized. The requests are selectively forwarded to a storage device queue according to their priorities so as to maintain the device queue at a target queue depth. The target queue depth is adjusted response to a latency value for the requests wherein the latency value is computed based on a difference between an arrival time and a completion time of the requests for each workload. Prioritizing the requests may be accomplished by computing a target deadline for a request based on a monitored arrival time of the request and a target latency for its workload. To reduce latencies, the target queue depth may be reduced when the target latency for a workload is less than its computed latency value. To increase throughput, the target queue depth may be increased when the target latency for each workload is greater than each computed latency value.

Prophylaxis latency and outcome in bipolar disorders.

Abstract: Objective:To analyze new and reviewed findings to evaluate relations between treatment response and latency from onset of bipolar disorder (BD) to the start of mood-stabilizer prophylaxis.Method:We...

Method and apparatus for approximating location of node attached to a network

Abstract: A plurality of reference nodes that are attached to the network are correlated with geographic location. Communication latency between the reference nodes are used to approximate the location of a target node once the communication latency from one of the reference nodes to the target node is determined.

Effective Vaccination against Long-Term Gammaherpesvirus Latency

Abstract: The fundamental question of whether a primed immune system is capable of preventing latent gammaherpesvirus infection remains unanswered. Recent studies showing that vaccination can reduce acute replication and short-term latency but cannot alter long-term latency further call into question the possibility of achieving sterilizing immunity against gammaherpesviruses. Using the murine gammaherpesvirus 68 (γHV68) system, we demonstrate that it is possible to effectively vaccinate against long-term latency. By immunizing mice with a γHV68 mutant virus that is deficient in its ability to reactivate from latency, we reduced latent infection of wild-type challenge virus to a level below the limit of detection. Establishment of latency was inhibited by vaccination regardless of whether mice were challenged intraperitoneally or intranasally. Passive transfer of antibody from vaccinated mice could partially reconstitute the effect, demonstrating that antibody is an important component of vaccination. These results demonstrate the potential of a memory immune response against gammaherpesviruses to alter long-term latency and suggest that limiting long-term latent infection in a clinically relevant situation is an attainable goal.

Response Latency Methodology for Survey Research: Measurement and Modeling Strategies

Abstract: In public opinion research, response latency is a measure of attitude accessibility, which is the ease or swiftness with which an attitude comes to mind when a respondent is presented with a survey question. Attitude accessibility represents the strength of the association in memory between an attitude object and an evaluation of the object. Recent research shows that attitude accessibility, as measured by response latency, casts light on a wide range of phenomena of public opinion and political behavior. We discuss response latency method ology for survey research and advocate the use of latent response latency timers (which are invisible both to respondents and interviewers) as a low cost, low-maintenance alter native to traditional methods of measuring response latency in public opinion surveys. We show that with appropriate model specification latent response latency timers may provide a suitable alternative to the more complicated and expensive interviewer-activated timers.

Computation Hierarchy for In-network processing

Abstract: Explored the latency and energy tradeoffs introduced by the heterogeneity of sensor nodes in the netework.

Interfacing cores with on-chip packet-switched networks

Abstract: With the emergence of the packet-switched networks as a possible system-on-chip (SoC) communication paradigm, the design of network-on-chips (NoC) has provided a challenge to the designers. Meeting latency requirements of communication among various cores is one of the crucial objectives for system designers. The core interface to the networking logic and the communication network are the key contributors to latency. With the goal of reducing this latency we examine the packetization strategies in the NoC communication. In this paper, three schemes of implementations are analyzed, and the costs in terms of latency, and area are projected through actual synthesis.

Method and apparatus for characterizing and/or predicting display backlight response latency

Abstract: An approach to controlling an electronic system display includes determining a latency associated with changing a backlight brightness from a first level to a second level, and based on the determined latency, providing the latency predictions to a coordinating entity, which adjusts the backlight brightness and image luminance to occur in such a manner so as to substantially avoid associated visually disturbing artifacts which would otherwise occur if the two actions were applied asynchronously.

Elimination of response latency variability in neuronal spike trains.

Abstract: Neuronal activity in the mammalian cortex exhibits a considerable amount of trial-by-trial variability. This may be reflected by the magnitude of the activity as well as by the response latency with respect to an external event, such as the onset of a sensory stimulus, or a behavioral event. Here we present a novel nonparametric method for estimating trial-by-trial differences in response latency from neuronal spike trains. The method makes use of the dynamic rate profile for each single trial and maximizes their total pairwise correlation by appropriately shifting all trials in time. The result is a new alignment of trials that largely eliminates the variability in response latency and provides a new internal trigger that is independent of experiment time. To calibrate the method, we simulated spike trains based on stochastic point processes using a parametric model for phasic response profiles. We illustrate the method by an application to simultaneous recordings from a pair of neurons in the motor cortex of a behaving monkey. It is demonstrated how the method can be used to study the temporal relation of the neuronal response to the experiment, to investigate whether neurons share the same dynamics, and to improve spike correlation analysis. Differences between this and other previously published methods are discussed.

Timeslot arbitration scheme

Abstract: A method for arbitrating between a plurality of access requests issued in relation to a resource by a plurality of requestors, wherein each request can be one of at least two types, a first of the types having a higher latency associated with its performance than at least some of the other types, the method including the steps of: (a) receiving a plurality of the access requests; (the requests are not placed anywhere, they are simply received); (b) maintaining a current pointer that points to a current timeslot in a timeslot list, and at least one lookahead pointer that points to a future timeslot in the timeslot list; and (c) in the event an access request as arbitrated via the lookahead pointer is of the first type, initiating performance of the access request earlier than the position in the list suggests it would be performed should it be started when the current pointer reached the timeslot.

Maintenance of gammaherpesvirus latency requires viral cyclin in the absence of B lymphocytes.

Abstract: Gammaherpesviruses establish a life-long chronic infection that is tightly controlled by the host immune response. We previously demonstrated that viruses lacking the gammaherpesvirus 68 (gammaHV68) viral cyclin (v-cyclin) exhibited a severe defect in reactivation from latency and persistent replication. In this analysis of chronic infection, we demonstrate that the v-cyclin is required for gammaHV68-associated mortality in B-cell-deficient mice. Furthermore, we identify the v-cyclin as the first gene product required for maintenance of gammaherpesvirus latency in vivo in the absence of B lymphocytes. While the v-cyclin was necessary for maintenance of latency in the absence of B cells, maintenance of v-cyclin-deficient viruses was equivalent to that of wild-type gammaHV68 in the presence of B cells. These results support a model in which maintenance of chronic gammaHV68 infection requires v-cyclin-dependent reactivation and reseeding of non-B-cell latency reservoirs in the absence of B cells and raise the possibility that B cells represent a long-lived latency reservoir maintained independently of reactivation. These results highlight distinct mechanisms for the maintenance of chronic infection in immunocompetent and B-cell-deficient mice and suggest that the different latency reservoirs have distinct gene requirements for the maintenance of latency.