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 & Signal. The organization has 3473 authors who have published 5208 publications receiving 65429 citations. The organization is also known as: DTAG & German Telecom.

MeasuRouting: a framework for routing assisted traffic monitoring

Abstract: Monitoring transit traffic at one or more points in a network is of interest to network operators for reasons of traffic accounting, debugging or troubleshooting, forensics, and traffic engineering. Previous research in the area has focused on deriving a placement of monitors across the network toward the end of maximizing the monitoring utility of the network operator for a given traffic routing. However, both traffic characteristics and measurement objectives can dynamically change over time, rendering a previously optimal placement of monitors suboptimal. It is not feasible to dynamically redeploy/reconfigure measurement infrastructure to cater to such evolving measurement requirements. We address this problem by strategically routing traffic subpopulations over fixed monitors. We refer to this approach as MeasuRouting. The main challenge for MeasuRouting is to work within the constraints of existing intradomain traffic engineering operations that are geared for efficiently utilizing bandwidth resources, or meeting quality-of-service (QoS) constraints, or both. A fundamental feature of intradomain routing, which makes MeasuRouting feasible, is that intradomain routing is often specified for aggregate flows. MeasuRouting can therefore differentially route components of an aggregate flow while ensuring that the aggregate placement is compliant to original traffic engineering objectives. In this paper, we present a theoretical framework for MeasuRouting. Furthermore, as proofs of concept, we present synthetic and practical monitoring applications to showcase the utility enhancement achieved with MeasuRouting.

RZ versus NRZ modulation format for dispersion compensated SMF-based 10-Gb/s transmission with more than 100-km amplifier spacing

Abstract: We compared numerically and experimentally the transmission behavior of return-to-zero (RZ) and nonreturn-to-zero (NRZ) modulated signals, 10 Gb/s were transmitted over 2040-km standard single-mode fiber using an alternating dispersion compensation scheme in a recirculating loop with 102 km amplifier spacing. Receiver sensitivities of -33 dBm (NRZ) and -35 dBm (RZ) could be achieved. RZ allows for a simple linear dispersion compensation whereas NRZ suffers from nonlinear signal distortion. NRZ requires under-compensation of the linear chromatic dispersion dependent on signal power and transmission length. Therefore, NRZ makes network design more difficult.

Cooperative Interference Prediction for Enhanced Link Adaptation in the 3GPP LTE Uplink

Abstract: The interference situation in the uplink of cellular networks, such as the 3GPP UTRAN Long Term Evolution (LTE), is usually highly volatile since from one transmission time interval to the other different users might be scheduled in nearby cells, thus often causing completely different levels of interference. This unstable behavior of the interference generally has a negative impact on the performance of fast link adaptation schemes since there is always an inherent delay between the time when the link adaptation is performed and the actual data transmission. In order to partially mitigate this problem, we propose in this paper a novel approach for predicting the interference situation during the actual data transmission already in advance, so that the link adaptation process can be considerably improved. This is accomplished by exchanging scheduling information between a set of cooperating base stations combined with multi-cell channel estimation. The performance of the proposed scheme is evaluated by means of extensive system-level simulations and we show that significant performance gains may be realized this way.

Interactive hybrid recommender system

Abstract: A hybrid recommender system, in which the initial stereotype is manually defined by an expert and an affinity vector of stereotypes relating to each specific user who registers onto the system, is created to define a specific profile for each user. Recommendations for a specific user are generated according to the initial stereotype and the affinity vector of stereotypes. A binary feedback, from user regarding specific items picked by him is received (e.g., while of the item), which can be either positive or negative. Then the affinity vector of stereotypes is updated.

Symmetrical dispersion compensation for standard monomode-fiber-based communication systems with large amplifier spacing.

Abstract: Optical 10-Gbit / s return-to-zero pulse transmission in cascaded communication systems using dispersion compensation of the standard monomode fiber with large amplifier spacing is examined. It is shown that pulse distortions that are due to Kerr nonlinearity are significantly diminished by symmetrical ordering of the compensation sections when the total number of precompensation and postcompensation sections is equal. Repositioning of these sections is not critical.