Abstract: A system for communication between two communication platforms, including a near-earth returning platform and a remote platform. A bidirectional asymmetrical communication link is set up between the two platforms.

Abstract: A method of reconfiguring a data unit communication network that comprises bridge nodes is described. Each bridge node comprises two or more ports for receiving and sending data units, a controller for controlling said bridge node and for handling received data units, and a record for associating data unit address information with port identification information. The controller is capable of querying said record for determining which one or more ports to forward a received data unit to.

Abstract: A method of reconfiguring a data unit communication network that comprises bridge nodes is described. Each bridge node comprises two or more ports for receiving and sending data units, a controller for controlling said bridge node and for handling received data units, and a record for associating data unit address information with port identification information. The controller is capable of querying said record for determining which one or more ports to forward a received data unit to.

Abstract: A system for communication between two communication platforms, including a near-earth returning platform and a remote platform. A bidirectional asymmetrical communication link is set up between the two platforms.

Abstract: A network bridge comprising two ports for connection to two networks, a spanning tree controller and a wireless bridge link controller for each port. The ports employ an adaptive modulation technique. The wireless bridge link controller is connected to the port to exchange physical layer information with said port. When the port detects a change of its PHY mode, it sets the path cost of the link to a value configured for the new PHY mode and forces the bridge to recalculate its spanning tree. The wireless bridge link controller is also connected to the spanning tree controller. If the bridge detects that it has not received BPDUs for a certain time period and the timer will expire soon, the bridge forces the port, via the wireless bridge link controller, to use a more robust PHY mode.

Abstract: A network bridge comprising two ports for connection to two networks, a spanning tree controller and a wireless bridge link controller for each port. The ports employ an adaptive modulation technique. The wireless bridge link controller is connected to the port to exchange physical layer information with said port. When the port detects a change of its PHY mode, it sets the path cost of the link to a value configured for the new PHY mode and forces the bridge to recalculate its spanning tree. The wireless bridge link controller is also connected to the spanning tree controller. If the bridge detects that it has not received BPDUs for a certain time period and the timer will expire soon, the bridge forces the port, via the wireless bridge link controller, to use a more robust PHY mode.

Abstract: A method for monitoring a redundant (passive) transmitter, being, for example, part of a base station of a point-to-multipoint radio communications system transmits, during normal operation, a spread-spectrum signal over the redundant transmitter, the spread-spectrum signal being of low spectral power in comparison with data signals being transmitted by the active transmitter of the base station. One or more receivers are associated, for example, with terminal stations in communication with the base station and detect the presence of the spread-spectrum signal. If the spread-spectrum signal is not found to be present, the receivers provide an indication of this, and from this indication, a decision is made as to the integrity of the redundant transmitter.

Abstract: A method for monitoring a redundant (passive) transmitter, being, for example, part of a base station of a point-to-multipoint radio communications system transmits, during normal operation, a spread-spectrum signal over the redundant transmitter, the spread-spectrum signal being of low spectral power in comparison with data signals being transmitted by the active transmitter of the base station. One or more receivers are associated, for example, with terminal stations in communication with the base station and detect the presence of the spread-spectrum signal. If the spread-spectrum signal is not found to be present, the receivers provide an indication of this, and from this indication, a decision is made as to the integrity of the redundant transmitter.

Abstract: The method of receiving a coded data signal encoded by means of a state transition diagram having a number of states (U, V, W, X) by a receiver, the receiver including a demodulator that generates estimated symbols (c′i) from the data signal and a following data decoder, includes forming a number (N) of groups (a,b) from the states (U, V, W, X) of the state transition diagram; continuously making estimations of probabilities of group membership of a current state of the data decoder (Dd) in the groups (a,b); furnishing the estimations to the demodulator as assisting signals and generating the estimated symbols (c′i) using them. In another embodiment, a number (K) of groups (I,II) are formed from channel symbols of a channel symbol alphabet, estimates of probabilities of group membership of received symbols are continuously made, the estimates are supplied to the demodulator (Dd) as assisting signals and the estimated symbols (c′i) are generated from them.

Abstract: To calibrate a transmitter and/or sender for controlling a beam forming network, each of the control signals is divided into a plurality of frequency segments. The control signal of each frequency segment is multiplied by complex coefficients so that the transmitter output signals, after passing through a reference receiver, are identical to the respective control signals. A similar adjustment is performed for the receive direction. The method and the device allow the same beam characteristic.

Abstract: In order to allow a flexible allocation of transmission capacities in a radio transmission system, without disrupting or interrupting existing radio connections, a control device is provided which, in the event of a change in the transmission channels, adjusts one or more of the transmission parameters in a central station and in affected subscriber stations in such a way that the bandwidth of the available radio channel is optimally utilized. For this purpose, the modems present in the central station and in the subscriber stations are equipped with two transmitted signal paths and two paths and two received signal paths, only one of received signal paths (ENC1, ENC2, IF1, IF2, MOD1, MOD2, DEM1, DEM2, DF1, DF2, DEC1, DEC2), only one of which is activated in each case for a signal transmission. The outputs of the transmitted signal paths and the inputs of the received signal paths are equipped with frequency splitters.

Abstract: In order to permit flexible allocation of transmission capacities in such a radio transmission system, without interrupting or disturbing existing radio links, provision is made for a control device which, in response to a change of transmission channels in the central station and in the subscriber stations in question, adjusts one or a plurality of transmission parameters so that both the band width of the available radio frequency channel is optimally utilized, and a required resistance to interference is attained in the radio frequency channel. To that end, the modems existing in the central station and in the subscriber stations are equipped with L transmission channels and K receiving channels, of which, in each case, a maximum of L-1 in the transmission direction, and a maximum of K-1 in the receiving direction are activated.

Abstract: A frequency and phase regulating circuit, particularly for a digital complex-value vestigial sideband signal or Nyquist flank-filtered signal, with a regulating loop having a filter device which generates, from the signal to be regulated, a symmetrical double sideband signal band-delimited to a reference frequency. This regulating circuit is particularly suitable for a digital TV demodulator.

Abstract: A frequency detector is provided for carrier frequency synchronization in a digital receiver including a frequency control circuit having a voltage-controlled oscillator (VCO), a multiplier for the received signal and the VCO signal and a device to suppress double frequency signal terms of the product signal from the multiplier. The frequency detector includes cascades of complex bandpass filters and real or complex pre-equalizers, which include bandpass filters (BP) and pre-equalizers (VE) for the real part (x) and the imaginary part (y) of the product signal, and a logic circuit which has a combining device for the cascade output signals that forms a control signal (u.sub.f) for the voltage-controlled oscillator (VCO). The combining device squares or multiplies the cascade output signals to form resulting signals as a measure of power and subtracts the resulting signals from each other to produce the control signal.

Abstract: A method of synchronizing clock pulses of a clock pulse generator used in a receiver of digital data transmissions. The received signal is demodulated by multiplying it in quadrature by an output signal of a carrier oscillator to obtain demodulated in-phase and quadrature components. The demodulated components are lowpass filtered to suppress harmonics of the carrier frequency and then bandpass filtered into two complex signals. The two complex signals are then linked together with a first linkage circuit to form a first control signal u.sub.TI. The two complex signals are also linked together with a second linkage circuit to form a second control u.sub.TR, wherein the two control signals can be interpretated as the real and imaginary components of a complex control signal u.sub.T =u.sub.TR +ju.sub.TI. The two components are separately averaged and then evaluated to form an actuation signal having an actuation value .delta.

Abstract: The invention relates to a timing error detector for clock pulse synchronization in a receiver for synchronous data transmission. The timing error detector receives, as the demodulated received signal, the in-phase component and the quadrature component from the product of the received signal with the output signal of the carrier oscillator, with these components being lowpass filtered so that the signal terms of the double frequency are suppressed. The output signal serves as control signal u.sub.TI for the clock pulse generator. The timing error detector includes two bandpass filters fed with the demodulated received signal and a linkage circuit which generates the control signal from the complex bandpass output signals. The detector is characterized in that a further linkage circuit VF is provided which generates a control signal u.sub.f to control the frequency of the carrier oscillator from the complex output values of bandpass filters BP+ (FIG. 4).

Abstract: The present invention relates to a multicarrier demodulator for separating and demodulating a digitalized frequency multiplexed signal into a plurality (L) of individual channel signals, with the separation being performed using a frequency division demultiplexer (FDM). The separated channel signals are each filtered using bandwidth limitation filters and thereafter demodulated using a synchronous demodulator. Following demodulation, the signals are filtered by interpolation filters, data (Nyquist) filters, and subsequently decided upon in a decider. The invention is characterized by the fact that the demodulator operates upon a pair of phase displaced complex channel signals.

Abstract: A method and circuit arrangement for synchronizing a receiver in a digital transmission system with transmission of a special preamble selected in such a manner that, with correct demodulation, the received signal has a cosine shape with a pattern frequency fp from which the clock pulse frequency results, and wherein frequency and/or phase of the carrier and clock pulse signal, respectively, are estimated, and, after demodulation with an assumed carrier frequency ft0, the individual spectral lines (gp, gn) of the received signal (rd) are obtained by filtering, and from these signals, their frequency (fgp, fgn) and phase ( gp, gn) are determined by linear regression, with these frequency and phase values being used, by means of subsequent difference and sum formation, to obtain the following estimated values: ##EQU1##