No abstract

Multi-standard software-definable radios which are capable of operation according to a variety of different mobile radio standards represent an extremely powerful tool for evolution towards future third-generation cellular systems. This is particularly the case in Europe where the emergence of advanced UMTS air-interfaces needs to be accompanied with some degree of backward compatibility with the well-established GSM/DCS systems. This paper examines a number of the architectural issues and trade-offs involved in the design of wideband multi-standard GSM/UMTS digital radios and presents an examination of the filtering and ADC technology requirements for their implementation. This work has been undertaken in the context of the FIRST project (Flexible Integrated Radio System Technology) as part of the ACTS mobile line.

In a relay satellite network, information from LEO satellites is transmitted first over an OISL (Optical InterSatellite Link) to a GEO relay satellite and then via microwave Ka-band from the GEO relay to the GS (Ground Station). ESA and ASV (Astrium Services) have initiated the program EDRS (European Data Relay Satellite) for the development and operation of several GEO relay satellites. This paper covers the digital concepts for packet data transmission with up to 1800 Mbps in the complete network LEOGEOGS. The LEO contains a digital processing unit where the outputs of several mass memories are encapsulated into packets, error-control coding is added and finally multiplexing and frame stuffing is applied to generate a data stream for the transmission over the OISL. Another digital processing unit is located in the GEO relay, where the data stream received from the OISL is again encapsulated and packetized, encrypted, encoded, multiplexed with idle frames and split to several Ka-band DL (DownLink) channels. The performance of the network is evaluated by a combination of analytical and simulation methods.

In the space business, there is typically a quite long period from the design and development of new technologies to their commercial use. Even comprehensive tests on ground cannot replace long-lasting experiments and tests in space. Such IOV (In Orbit Verification) activities provide the scientific basis for the introduction and application of new technologies and the necessary heritage for commercial satellite programs. The Heinrich-Hertz mission of a geostationary communication satellite with a planned life time of 15 years lead by the German Space Administration (DLR) establishes a valuable basis to verify new technologies scientifically in orbit over a long period of time and to gain heritage regarding their performance in space [1]. In addition, research institutes and the industry are enabled to perform numerous scientific and technological experiments over the full life time of 15 years. With this approach of the mission, the German Space Administration offers to the German satellite industry an outstanding advantage and gain in knowledge for the development of new communication technologies and their applications. The launch of the satellite is envisaged for 2016. The technical feasibility of the overall program was successfully demonstrated within a Phase A study. The major tasks for the payload responsible during Phase A have been: (1) survey and assessment of all proposed IOV-technologies, (2) development of a payload concept for the scientific-technical verification of the IOV-technologies.

Adaptive filters are updated with the stochastic gradient least mean squares algorithm (LMS) in many applications. A generally remaining dithering of the coefficients causes a residual signal with a variance which was calculated in Part I [2]. If adaptive filters are used in digital receivers for data communication, additional information about the statistics of the residual signal would be useful for the calculation of the overall error probability. This contribution deals with the exact computation of the amplitude distribution of the residual signal, both for infinite-as finite-precision adaptive operation. As main result, the residual signal is established as Gaussian distributed even for adaptive filters with only one coefficient, if certain conditions are fulfilled. The widely used assumptions for the analysis of adaptive filtering are partly confirmed and otherwise partly refused. Übersicht: Fur adaptive Filter wird bei vielen Anwendungen das stochastische Gradientenverfahren (LMS-Algorithmus) zur Einstellung der Koeffizienten verwendet Ein grundsätzlich immer verbleibendes Zittern der Koeffizienten fuhrt zu einem Restsignal, dessen Varianz in Teil I [2] berechnet wurde. Beim Einsatz adaptiver Filter in digitalen Empfängern zur Datenübertragung sollten zur Berechnung der Fehlerwahrscheinlichkeit die statistischen Eigenschaften des Restsignals bekannt sein. Die Amplitudenverteilung des Restsignals wird hier sowohl für die weitkontinuierliche wie die wertdiskrete Adaption exakt berechnet Als Hauptergebnis erweist sich das Restsignal als normalverteilt schon für Filter mit nur einem Koeffizienten, sofern gewisse Voraussetzungen erfüllt sind. Die üblichen Annahmen für die Analyse adaptiver Filter werden teilweise bestätigt und teilweise widerlegt. Für die Dokumentation: Adaptive Filter / LMS-Algorithmus / Koeffizientenzittern / Quantisierung / Konvergenz von Verteilungen / Funktionalgleichungen / Differential-und Differenzengleichungen