Deutsche Telekom

About: Deutsche Telekom is a company organization based out in Welwyn Garden City, United Kingdom. It is known for research contribution in the topics: Telecommunications network & Terminal (electronics). The organization has 3473 authors who have published 5208 publications receiving 65429 citations. The organization is also known as: DTAG & German Telecom.

Non-asymptotic Delay Bounds for Networks with Heavy-Tailed Traffic

Abstract: Traffic with self-similar and heavy-tailed characteristics has been widely reported in networks, yet, only few analytical results are available for predicting the delay performance of such networks. We address a particularly difficult type of heavy-tailed traffic where only the first moment can be computed, and present the first non-asymptotic end-to-end delay bounds for such traffic. The derived performance bounds are non-asymptotic in that they do not assume a steady state, large buffer, or many sources regime. Our analysis considers a multi-hop path of fixed-capacity links with heavy-tailed self-similar cross traffic at each node. A key contribution of the analysis is a probabilistic sample-path bound for heavy-tailed arrival and service processes, which is based on a scale-free sampling method. We explore how delays scale as a function of the length of the path, and compare them with lower bounds. A comparison with simulations illustrates pitfalls when simulating self-similar heavy-tailed traffic, providing further evidence for the need of analytical bounds.

Alternative similarity functions for graph kernels

Abstract: Given a bipartite graph of collaborative ratings, the task of recommendation and rating prediction can be modeled with graph kernels. We interpret these graph kernels as the inverted squared Euclidean distance in a space defined by the underlying graph and show that this inverted squared Euclidean similarity function can be replaced by other similarity functions. We evaluate several such similarity functions in the context of collaborative item recommendation and rating prediction, using the exponential diffusion kernel, the von Neumann kernel, and the random forest kernel as a basis. We find that the performance of graph kernels for these tasks can be increased by using these alternative similarity functions.

Nonlinear Optical Phase Conjugation

Abstract: A very fascinating application of nonlinear optical effects is the nonlinear phase conjugation (NPC) which will be discussed in this Chapter. Under particular circumstances, it is possible to compensate optical distortions with NPC and optical pulses in a fiber can be regenerated. Therefore, in the range of optical telecommunications the NPC, can be exploited for the compensation of group velocity dispersion [193] as well as nonlinear effects like SPM [194] or Raman scattering [195].

Sharing airtime with Shair avoids wasting time and money

Abstract: Shair is a system allowing contracted mobile phone users to benefit from their unused quota minutes and text messages. Unused minutes and texts are shared via opportunistic local connectivity, allowing other Shair users to use sharers' phones within reach of short range radio such as Bluetooth.