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.

A Fundamental Relation Between Blind and Supervised Adaptive Filtering Illustrated for Blind Source Separation and Acoustic Echo Cancellation

Abstract: In recent years broadband signal aquisition by sensor arrays, e.g., for speech and audio signals in a hands-free scenario, has become a popular research field in order to separate certain desired source signals from competing or interfering source signals ((blind) source separation or interference cancellation) and to possibly dereverberate them (blind deconvolution). In various practical scenarios, some or even all interfering source signals may be directly accessible and/or some side information on the propagation path is known. In these cases we can tackle the separation problem by supervised adaptation algorithms, e.g., the popular LMS- or RLS-type algorithms, rather than the more involved blind adaptation algorithms. In contrast, for blind estimation, such as in the blind source separation (BSS) scenario where both the propagation paths and the original source signals are unknown, the method of independent component analysis (ICA) is typically applied. Traditionally, the ICA method and supervised adaptation algorithms have been treated as different research areas. In this paper, we establish a conceptually simple, yet fundamental relation between these two worlds. This is made possible using the previously introduced generic broadband adaptive filtering framework, called TRINICON. As we will demonstrate, not only both the well-known blind and supervised adaptive filtering algorithms turn out as special cases of this generic framework, but we also gain various new insights and synergy effects for the development of new and improved adaptation algorithms.

Positioning for Location-Aware Beamforming in 5G Ultra-Dense Networks

Abstract: 5G ultra-dense radio networks enhance utilization of spatial dimension by wide implementation of location-aware beamforming and interference mitigation techniques. Successful realization of simultaneous transmission and reception is possible by means of preliminary positioning of neighboring user equipment. Contribution of the current research is positioning accuracy limits estimation of user equipment using direction of arrival measurement processing in three-dimensional space with metrics of Cramer-Rao lower bound ellipsoid. Resulting accuracy limits were analyzed and visualized to assist in proper access nodes layout.

Degradation of multicarrier and single carrier transmission with frequency domain equalization due to pilot-aided channel estimation and frequency synchronization

Abstract: The performance of multicarrier and single carrier modulation schemes is compared for wideband mobile radio communication systems. In both cases the fast Fourier transform (FFT) and its inverse are utilized. The transmission systems are simulated with time-variant transfer functions measured with a wideband channel sounder. In case of OFDM, the individual subcarriers are modulated with fixed and adaptive signal alphabets. In particular, the systems are compared with respect to the degradation due to pilot-aided channel estimation and carrier frequency synchronization.

Fixed and mobile convergence: which role for optical networks?

Abstract: The current level of pooling and sharing between fixed and mobile infrastructures is not sufficient to allow the most efficient use of network resources, whether fixed, mobile, or Wi-Fi. In the perspective of 5G networks, efficient resource sharing of fixed and mobile infrastructures, called structural convergence, will be essential in the path toward an integrated fixed and mobile network. This structural convergence is being triggered by different architecture trends, e.g., baseband unit hostelling and mobile fronthaul technologies, heterogeneous radio access networks, and, most importantly, a unified optical access and aggregation network. The COMBO European project is studying architectural options for structural convergence leveraging on the aforementioned technological triggers and in particular on the evolution of optical access and aggregation technologies. These architectural options are described and analyzed with respect to anticipated needs for integrated fixed and mobile networks.

An Experimental Evaluation of Urban Networking using IEEE 802.11 Technology

Abstract: A new opportunity to reuse existing broadband access infrastructure has arisen by the high penetration of IEEE 80211 technology family DSL routers and cable modems with built-in WLAN capabilities allow broadband private customers to share bandwidth with third parties in a safe and controlled way The success of this approach is highly dependant on the performance of WiFi technology in urban areas It is critical to experimentally evaluate IEEE 80211 deployments in places such as houses, flats, parks and offices This paper describes a solution that enables controlled sharing of existing broadband connections to increase wireless access coverage The feasibility of our solution is pondered by performing a thorough study of urban networking using IEEE 80211 technology We evaluate the performance of this technology in urban environments and analyse the impact of typical factors such as (i) access point elevation in relation to the mobile client, (ii) inter-floor connectivity in urban buildings and (iii) widely used hardware Using the collected data, we estimate the potential service range for those opening their broadband connections The results suggest that sharing private connections could exponentially increase wireless coverage in urban areas