12676409
Measurements of the congestion responsiveness of windows streaming media
While previous research has shown that streaming media can respond to network congestion, it is not known to what extent commercial products are responsive. This research characterizes the bitrate response of Windows Streaming Media (WSM) to changes in network capacity and loss rate. A streaming media test bed was built to systematically vary network and content encoding characteristics and measure WSM congestion responsiveness. The results demonstrate that WSM improve response to congestion when content is encoded into several bitrates by the content provider.
9337355
Weather forecasting: predicting performance for streaming video over wireless LANs
The growth of wireless LANs has brought the expectation for high-bitrate streaming video to wireless PCs. However, it remains unclear how wireless channel characteristics impact the quality of streaming video sent over wireless LANs. This paper presents results from experiments that stream commercial video over a wireless campus network. By analyzing the streaming video quality and capturing wireless LAN characteristics across network and wireless link layers, "weather forecasts" are created such that selected wireless LAN performance indicators might be used to predict the streaming video quality. Furthermore, a quantified measurement of accuracy is presented to evaluate the effectiveness of individual weather forecasts. The paper evaluates six distinct weather forecasts four different streaming configurations including TCP and UDP streaming, and single and multiple-level encoded videos. The results show that the wireless Received Signal Strength Indicator (RSSI) and average wireless link capacity are the most accurate indicators to predict the performance of streaming video over wireless LANs. The weather forecast philosophy can be beneficial for adapting video streaming in wireless LAN environments.
52151541
Linear approximation of shortest superstrings
We consider the following problem: given a collection of strings <italic>s<subscrpt>1</subscrpt></italic>,…, <italic>s<subscrpt>m</subscrpt></italic>, find the shortest string <italic>s</italic> such that each <italic>s<subscrpt>i</subscrpt></italic> appears as a substring (a consecutive block) of <italic>s</italic>. Although this problem is known to be NP-hard, a simple greedy procedure appears to do quite well and is routinely used in DNA sequencing and data compression practice, namely: repeatedly merge the pair of (distinct) strings with maximum overlap until only one string remains. Let <italic>n</italic> denote the length of the optimal superstring. A common conjecture states that the above greedy procedure produces a superstring of length <italic>O(n)</italic> (in fact, 2<italic>n</italic>), yet the only previous nontrivial bound known for any polynomial-time algorithm is a recent <italic>O(n</italic> log <italic>n</italic>) result.
We show that the greedy algorithm does in fact achieve a constant factor approximation, proving an upper bound of 4<italic>n</italic>. Furthermore, we present a simple modified version of the greedy algorithm that we show produces a superstring of length at most 3<italic>n</italic>. We also show the superstring problem to be MAXSNP-hard, which implies that a polynomial-time approximation scheme for this problem is unlikely.
3009418
The hamiltonian index of a graph and its branch-bonds
Let $G$ be an undirected and loopless finite graph that is not a path. The minimum $m$ such that the iterated line graph $L^m(G)$ is hamiltonian is called the hamiltonian index of $G,$ denoted by $h(G).$ A reduction method to determine the hamiltonian index of a graph $G$ with $h(G)\geq 2$ is given here. With it we will establish a sharp lower bound and a sharp upper bound for $h(G)$, respectively, which improves some known results of P.A. Catlin et al. [J. Graph Theory 14 (1990)] and H.-J. Lai [Discrete Mathematics 69 (1988)]. Examples show that $h(G)$ may reach all integers between the lower bound and the upper bound.
15861046
A Survey on Topology issues in Wireless Sensor Network
Topology issues have received more and more attentions in Wireless Sensor Networks (WSN). While WSN applications are normally optimized by the given underlying network topology, another trend is to optimize WSN by means of topology control. A number of approaches have been invested in this area, such as topology directed routing, cooperating schemes, sensor coverage based topology control and network connectivity based topology control. Most of the schemes have proven to be able to provide a better network monitoring and communication performance with prolonged system lifetime. In this survey paper, we provide a full view of the studies in this area. By summarizing previous achievements and analyzing existed problems, we also point out possible research directions for future work .
5412677
Middleware for streaming 3D progressive meshes over lossy networks
Streaming 3D graphics have been widely used in multimedia applications such as online gaming and virtual reality. However, a gap exists between the zero-loss-tolerance of the existing compression schemes and the lossy network transmissions. In this article, we propose a generic 3D middleware between the 3D application layer and the transport layer for the transmission of triangle-based progressively compressed 3D models. Significant features of the proposed middleware include. 1) handling 3D compressed data streams from multiple progressive compression techniques. 2) considering end user hardware capabilities for effectively saving the data size for network delivery. 3) a minimum cost dynamic reliable set selector to choose the transport protocol for each sublayer based on the real-time network traffic. Extensive simulations with TCP/UDP and SCTP show that the proposed 3D middleware can achieve the dual objectives of maintaining low transmission delay and small distortion, and thus supporting high quality 3D streaming with high flexibility.
41518374
Longest cycles in regular 2-connected claw-free graphs
In this paper, we show that every 2-connected, k-regular claw-free graph on n vertices contains a cycle of length at least min 4k?2, n (k?8), and this result is best possible.