77 research outputs found
An adaptive loss-aware flow control scheme for delay-sensitive applications in OBS networks
No full textOptical Burst Switching (OBS) is one of the most promising switching technologies for next generation optical networks. As delay-sensitive applications such as Voice-over-IP (VoIP) have recently become popular, OBS networks should guarantee stringent Quality of Service (QoS) requirements for such applications. Thus, this paper proposes an Adaptive Loss-aware Flow Control (ALFC) scheme, which adaptively decides on the burst offset time based on loss-rate information delivered from core nodes for assigning a high priority to delay-sensitive application traffic. The proposed ALFC scheme also controls the upper-bounds of the factors inducing delay and jitter for guaranteeing the delay and jitter requirements of delay-sensitive application traffic. Moreover, a piggybacking method used in the proposed scheme accelerates the guarantee of the loss, delay, and jitter requirements because the response time for. flow control can be extremely reduced up to a quarter of the Round Trip Time (RTT) on average while minimizing the signaling overhead. Simulation results show that our mechanism can guarantee a 10(-3) loss-rate under any traffic load while offering satisfactory levels of delay and jitter for delay-sensitive applications.The work was supported in part by the Korea Science and Engineering foundation(KOSEF) grant funded by the Korea government(MEST) (No.R11-2000-074-01001-0) and MIC, Korea under the ITRC program (ITAC1090060300350001000100100) supervised by IITA
A cross-layer approach for TCP optimization over wireless and mobile networks
No full textWe propose a path recovery notification (TCP-PRN) mechanism to prevent performance degradation during a handoff. Even though Freeze-TCP achieves a performance increase during hancloff, detecting accurate handoff time and the vulnerability of high variation in the round trip time (RTT) become obstacles for deploying Freeze-TCP in a real environment. The proposed protocol, TCP-PRN, quickly recovers lost packets by restoring the congestion window, preventing the congestion window to decrease, or immediately initiating the slow start algorithm. The simulation results of our study show better performance in a more realistic environment where the handoff prediction is difficult and the variation of RTT is higher. (c) 2008 Elsevier B.V. All rights reserved.This work was partially supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government(MOST)(No. R11-2000-074-02006-0). This work was partially supported by 2nd Phase of Brain Korea 21 project sponsored by Ministry of Education and Human Resources Development, Korea
Pt3Mn Intermetallic Catalysts for Oxygen Reduction Reaction in PEMFCs with Improved Activity and Durability
No full text
Performance Modeling of Communication Networks with Markov Chains
No full textThis book is an introduction to Markov chain modeling with applications to communication networks. It begins with a general introduction to performance modeling in Chapter 1 where we introduce different performance models. We then introduce basic ideas of Markov chain modeling: Markov property, discrete time Markov chain (DTMe and continuous time Markov chain (CTMe. We also discuss how to find the steady state distributions from these Markov chains and how they can be used to compute the system performance metric. The solution methodologies include a balance equation technique, limiting proba
Packet Transmission Order Based TCP Loss Recovery Algorithm: Extending Self Clocking Property to Resolve ACK Starvation
No full textAnalysis of Technological Innovation and Environmental Performance Improvement in Aviation Sector
No full textThe past oil crises have caused dramatic improvements in fuel efficiency in all industrial sectors. The aviation sector—aircraft manufacturers and airlines—has also made significant efforts to improve the fuel efficiency through more advanced jet engines, high-lift wing designs, and lighter airframe materials. However, the innovations in energy-saving aircraft technologies do not coincide with the oil crisis periods. The largest improvement in aircraft fuel efficiency took place in the 1960s while the high oil prices in the 1970s and on did not induce manufacturers or airlines to achieve a faster rate of innovation. In this paper, we employ a historical analysis to examine the socio-economic reasons behind the relatively slow technological innovation in aircraft fuel efficiency over the last 40 years. Based on the industry and passenger behaviors studied and prospects for alternative fuel options, this paper offers insights for the aviation sector to shift toward more sustainable technological options in the medium term. Second-generation biofuels could be the feasible option with a meaningful reduction in aviation’s lifecycle environmental impact if they can achieve sufficient economies of scale
Pricing of Digital Video Supply Chain: Free versus Paid Service on the Direct Distribution Channel
No full textMedia publishers that have commonly relied on profits from advertisements and content sales to fund their operations are not only content providers (manufacturers) to media aggregator platforms (retailers) but are also competing service providers (rival retailers) in the digital video supply chain. Different from a traditional media supply chain, they can easily operate their own direct distribution channels in the Internet era. In the digital video supply chain, it is not clear whether commercialization of the direct distribution channel would be beneficial for the media publisher because it would decrease profits from advertisements. The choice about commercialization should be investigated thoroughly because it is closely related to the media publishers’ sustainability as a public medium in a digital environment. In this study, we analyze the impacts of commercializing the direct distribution channel based on a game-theoretic approach. Specifically, we compare the profits of a media publisher with and without the commercialization of the channel from analyses of sequentially defined games. Our results show that media publishers prefer to use a free service on their direct channel if the content they provide is not highly valued. They can also choose not to provide their content to the media aggregator with a paid service
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