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.

Speech Quality Estimation: Models and Trends

Abstract: This article presents a tutorial overview of models for estimating the quality experienced by users of speech transmission and communication services. Such models can be classified as either parametric or signal based. Signal-based models use input speech signals measured at the electrical or acoustic interfaces of the transmission channel. Parametric models, on the other hand, depend on signal and system parameters estimated during network planning or at run time. This tutorial describes the underlying principles as well as advantages and limitations of existing models. It also presents new developments, thus serving as a guide to an appropriate usage of the multitude of current and emerging speech quality models.

Characteristics of pressure-based input for mobile devices

Abstract: We conducted a series of user studies to understand and clarify the fundamental characteristics of pressure in user interfaces for mobile devices. We seek to provide insight to clarify a longstanding discussion on mapping functions for pressure input. Previous literature is conflicted about the correct transfer function to optimize user performance. Our study results suggest that the discrepancy can be explained by different signal conditioning circuitry and with improved signal conditioning the user-performed precision relationship is linear. We also explore the effects of hand pose when applying pressure to a mobile device from the front, the back, or simultaneously from both sides in a pinching movement. Our results indicate that grasping type input outperforms single-sided input and is competitive with pressure input against solid surfaces. Finally we provide an initial exploration of non-visual multimodal feedback, motivated by the desire for eyes-free use of mobile devices. The findings suggest that non-visual pressure input can be executed without degradation in selection time but suffers from accuracy problems.

Latent perceptual mapping with data-driven variable-length acoustic units for template-based speech recognition

Abstract: In recent work, we introduced Latent Perceptual Mapping (LPM) [1], a new framework for acoustic modeling suitable for template-like speech recognition. The basic idea is to leverage a reduced dimensionality description of the observations to derive acoustic prototypes that are closely aligned with perceived acoustic events. Our initial work adopted a bag-of-frames strategy to represent relevant acoustic information within speech segments. In this paper, we extend this approach by better integrating temporal information into the LPM feature extraction. Specifically, we use variable-length units to represent acoustic events at the supra-frame level, in order to benefit from finer temporal alignments when deriving the acoustic prototypes. The outcome can be viewed as a generalization of both conventional template-based approaches and recently proposed sparse representation solutions. This extension is experimentally validated on a context-independent phoneme classification task using the TIMIT corpus.

A stackelberg game for power control and channel allocation in cognitive radio networks

Abstract: The ongoing growth in wireless communication continues to increase demand on the frequency spectrum. The current rigid frequency band allocation policy leads to a significant under-utilization of this scarce resource. However, recent policy changes by the Federal Communications Commission (FCC) and research directions suggested by the Defense Advanced Research Projects Agency (DARPA) have been focusing on wireless devices that can adaptively and intelligently adjust their transmission characteristics, which are known as cognitive radios. This paper suggests a game theoretical approach that allows master-slave cognitive radio pairs to update their transmission powers and frequencies simultaneously. This is shown to lead to an exact potential game, for which it is known that a particular update scheme converges to a Nash Equilibrium (NE). Next, a Stackelberg game model is presented for frequency bands where a licensed user has priority over opportunistic cognitive radios. We suggest a modification to the exact potential game discussed earlier that would allow a Stackelberg leader to charge a virtual price for communicating over a licensed channel. We investigate virtual price update algorithms for the leader and prove the convergence of a specific algorithm. Simulations performed in Matlab verify our convergence results and demonstrate the performance gains over alternative algorithms.

A taxonomy of quality of service and Quality of Experience of multimodal human-machine interaction

Abstract: Quality of Service (QoS) and Quality of Experience (QoE) are not only important for services transmitting multimedia data, but also for services involving multimodal human-machine interaction. In order to guide the assessment and evaluation of such services, we developed a taxonomy of the most relevant QoS and QoE aspects which result from multimodal human-machine interactions. It consists of three layers: (1) The QoS-influencing factors related to the user, the system, and the context of use; (2) the QoS interaction performance aspects describing user and system behavior and performance; and (3) the QoE aspects related to the quality perception and judgment processes taking place inside the user. For each of these layers, we provide metrics which make system evaluation more systematic and comparable.