Ascom Zelcom Ag

Zellweger Telecommunications Ag

Zellweger Tellecommunications Ltd.

Hanspeter Widmer

Roland Kueng

For the purpose of channel state estimation at the receiver end, a reference signal (f.sub.q (t)) is added to and is transmitted with the data signal (f.sub.i (t)) containing the actual information. The addition of the reference signal (f.sub.q (t)) to the data signal (f.sub.i (t)) is effected by means of a quadrature modulation with the reference signal on the Q-axis and with the data signal on the I-axis, the envelopes being selected so that the magnitude of the complex envelope is constant. The receiver has a function stage for preprocessing the receive signal, for quadrature detection of the data signal elements and reference signal elements (y.sub.i) and (b.sub.i) respectively, for selection of the data/reference signal and for estimating the channel state. This permits the operation of non-linear final stages of the transmitter and a maximum energy output from the transmitter, and the requirements of the short-wave transmission such as very low signal-to-noise ratio and signal interference ratio, fading, slightly drifting local oscillators and time bases, as well as high noise burst frequency are taken account of in an optimum manner. In addition the send signal has a narrow bandwidth and a low sensitivity to bit slip, which increases the connection probability and the robustness of the transmission.

Method and device for the digital transmission of information in

Selective addresses and/or emergency messages are transmitted between individual stations by using a calling signal consisting of a synchronization signal and an address signal (SS and AS) sent out by a transmitter. The address signal (AS) used is a FSK signal which forms a diversity pair by being subdivided into two identical m-ary FSK signals. The type of operation used is a Channel in Band Scanning. The apparatus contains an address signal receiver which is realized by Real Time-Digital-Signal processing. As a result, the desired participating stations and only these can be reliably and unequivocally activated. In addition, the process is extremely insensitive to interferences.

Process and apparatus for the transmission of selective addresses and/or

A connection (link setup) between individual stations of a radio network may be carried out fully automatically, and even with poor transmission quality, only the wanted stations are activated. A call signal includes a synchronization signal having narrow band, mark and space signals which form the component signals of a diverse pair of signals. A synchronization signal receiver independently detects and evaluates both of the component signals of the diverse pair as well as comparing the results thereof, with means of digital signal processing.

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Zurich, Switzerland

Hanspeter Widmer