1,720,975 research outputs found
On the objective evaluation of real-time networked games
No full textWith the recent evolution of network-based multiplayer games and the increasing popularity of online games demanding strict real-time interaction among players - like First Person Shooter (FPS) -, game providers face the problem to correlate network conditions with quality of gaming experience. This paper addresses the problem of the estimation gameplay quality during real-time games; in particular, we focus on FPS ones. Current literature usually considers end-to-end delay as the only important parameter and deducts system performance indexes from graphical ones. Player satisfaction, on the other hand, is usually evaluated in a subjective way: asking the player, or measuring how long he/she stays connected. In this paper we use a testbed with synthetic players (bots) to directly correlate network end-to-end delay and jitter with expected players' satisfaction. Running extensive experiments we argue about effective in-game performances degradation of penalized players. Performances are measured in terms of score and number of actions kills, actually - performed per minute
A protocol to improve the state scalability of source specific multicast
No full textSource specific multicast (SSM) is a viable solution for current multicast applications, since the driving applications to date are one to many, including Internet TV, distance learning, file distribution, streaming media, etc. It brings many benefits in billing, address allocation, and security. However, SSM still confronts the serious state scalability problem when there are a large number of simultaneous on-going multicast groups in the network. We propose a protocol to improve the state scalability of source specific multicast, which is called aggregated source specific multicast (ASSM). We design the detailed ASSM protocol and show that our solution can obtain significant multicast state and tree management overhead reduction while achieving transparency to end-users, compatibility with existing multicast technologies and low overhead
Measuring and modelling the group membership in the Internet
No full textIn this paper, we measure and model the distribution of multicast group members. Multicast research has traditionally been plagued by a lack of real data and an absence of a systematic simulation methodology. Although temporal group properties have received some attention, the location of group members has not been measured and modelled. However, the placement of members can have significant impact on the design and evaluation of multicast schemes and protocols as shown in previous studies. In our work, we identify properties of members that reflect their spatial clustering and the correlation among them (such as participation probability, and pairwise correlation). Then, we obtain values for these properties by monitoring the membership of network games and large audio-video broadcasts from IETF and NASA. Finally, we provide a comprehensive model that can generate realistic groups. We evaluate our model against the measured data with excellent results. A realistic group membership model can help us improve the effectiveness of simulations and guide the design of group-communication protocols
Aggregated Multicast - A Comparative Study
No full textThough IP multicast is resource ef£cient in delivering data to a group
of members simultaneously, it suffers from scalability problem with the
number of concurrently active multicast groups because it requires a
router to keep forwarding state for every multicast tree passing through
it. To solve this state scalability problem, we proposed a scheme, called
aggregated multicast. The key idea is that multiple groups are forced to
share a single delivery tree. In our earlier work, we introduced the basic
concept of aggregated multicast and presented some initial results to
show that multicast state can be reduced. In this paper, we develop a more
quantitative assessment of the cost/bene£t trade-offs. We propose an algorithm
to assign multicast groups to delivery trees with controllable cost
and introduce metrics to measure multicast state and tree management
overhead for multicast schemes. We then compare aggregated multicast
with conventional multicast schemes, such as source speci£c tree scheme
and shared tree scheme. Our extensive simulations show that aggregated
multicast can achieve signi£cant routing state and tree management overhead
reduction while containing the expense of extra resources (bandwidth
waste and tunnelling overhead). We conclude that aggregated multicast is a very cost-effective and promising direction for scalable transit
domain multicast provisioning
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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