Licentia Patent-verwaltungs Gmbh

Deutsche Thomson-brandt Gmbh

Thomson Licensing S.a.

Thomson Licensing

Deutsche Forschungsanstalt Fur Luft-und Raumfahrt E.v.

Otto Klank

Dieter Rottmann

Wolfgang Klausberger

J&uuml;rgen Laabs

Jurgen Laabs

Ernst F Schroder

Walter Voessing

Patrick Robertson

Khaled Fazel

Juergen Laabs

Dominique Madeleine

Stephan Wuttke

Helmut Wossner

Wilfried Wahling

The invention relates to a channel entering method for a RF communication system, in particular an indoor network, comprising a plurality of subscriber stations), each of said subscriber stations having a transmitter and a receiver, whereby information can be exchanged between said subscriber stations using respective transmitters and receivers and a plurality of channels available for RF communication in said RF communication system.

Channel preselection method for a RF communication system

The invention relates to Channel entering method for a wireless communication system, in particular an indoor network, comprising a plurality of subscriber stations (S1 to Sn, n&gE;2), each of said subscriber stations (S1 to Sn) having a transmitter and a receiver, whereby information can be independently exchanged between said subscriber stations (S1 to Sn) using respective transmitters and receivers and a plurality of channels available for communication in said wireless communication system. A directional antenna is used to review a first channel (Cx) selection, whereby said first channel (Cx) is selected from a first group of channels (C1 to Cm, m&gE;2) of said plurality of channels available for communication between a first and a second subscriber station (Sx, Sy; 1&lE;x&lE;n, 1&lE;y&lE;n) of said plurality of subscriber stations (S1 to Sn).

Channel entering method for a wireless communication system and subscriber station

Indoor communication system and synchronization for a receiver

Coarse symbol synchronization is carried out during reception, for tuning, the signal being correlated in the time domain with various copies of itself which are shifted in time and correspond to the possible transmission modes. The present mode, the present guard interval and a sampling window are derived from this.

Method for receiving multicarrier digital signals

In the radio transmission method according to the invention, which operates with a mixed frequency and time division multiplex method FDMA/TDMA, in which a relatively broad frequency band is divided according to the FDMA method into a plurality of carrier frequency ranges, namely the so-called main channels, and a plurality of time slots, namely the so-called sub-channels, distributed in a frame structure, are formed on each carrier frequency level according to the TDMA method, a grouping, that is to say a so-called cluster, of subscriber stations is assigned a limited number of main channels. A main channel signal is divided into one or more sub-channel signals which are associated with a cluster and which are transmitted using the TDMA method. Each transmitter of an activated subscriber station transmits a detectable check signal, so that, on the basis of detection of a check signal in the respective receiver, other, newly activated subscriber stations can determine the presence of transmit signals which are present within a specific, spatially limited range, namely their own respective transmission range. The method according to the invention can be used for transmitting information between terminals in indoor networks in a wireless manner without a central station.

Radio transmission method for digital multimedia data signals between subscriber stations in a local network

A method and device in which only a single symbol is required for synchronization, and which permits the detection of appreciable deviations from the normal receiver oscillator frequency or of a deviation of the transmitter frequency from the given frequency pattern, and the correction of the oscillator frequency. The invention further includes an evaluation method for the signal which contains a multiplicity of modulated carriers. In a decoder, additional sequences are evaluated after demodulation and differential reconversion by means of a correlation.

Method for the transmission of reference signals in an OFDM system

A problem in the reception of terrestrially transmitted digital multicarrier broadcast signals is synchronization in case a receiver is switched on or tuned to another channel. The time required by the receiver to reach a given tuning frequency with adequate accuracy and to determine that the currently received signal is not a system-compliant signal is reduced significantly if a characteristic value calculated from correlation values between a windowed and FFT transformed section of the received signal and a reference symbol stored in the receiver does not exceed a pre-defined threshold. In such case the receiver can go ahead to the next tuning frequency. If, however, the characteristic value exceeds that threshold, then a system-compliant signal is found, even with an offset. The multicarrier signal will be further decoded in the normal way. Such conformity check can also be carried out in the subsequent normal reception mode.

Method for reception of multicarrier signals and related apparatus

Various methods for terrestrial transmission of digital broadcast signals as DVB, HDTV-T and DAB signals are known. One of these methods is the OFDM method, where the transmitted signal includes a multiplicity of modulated carriers. These carriers are separated in the receiver by means of a Fast Fourier Transformation (FFT). Before being transposed in the frequency domain by the FFT, the analog signal must be sampled. For this purpose a local oscillator controls the timing in front of the FFT. Oscillator imperfections like jitter and frequency offsets can degrade the accuracy of the sampling operation and therefore introduce intercarrier interferences after the FFT. A feedback loop combining the AFC and CPEE process has been designed in order to correct frequency deviations and to reduce jitter of the signal without introducing significant phase noise.

Method for the frequency correction of multicarrier signals and related

A satellite radio receiver obtains signals from a satellite receiving installation comprising one or more frequency converters which may, for example, undergo a frequency drift as a result of temperature variations which cannot be compensated for by an AFC circuit which is located in the satellite radio receiver and which controls a carrier oscillator for carrier regeneration in a demodulator circuit. A local oscillator for a mixer is designed as a PLL local oscillator (44) which can be tuned in large or small increments. The AFC circuit (1) and a synchronizing signal evaluation circuit (40) are coupled to a control circuit (34) so that the PLL local oscillator (44) is tuned: 1) outside the control range of the AFC circuit (1), with a large tuning increment in the case of undetected synchronizing signals, and 2) with a small tuning increment in the case of detected synchronizing signals, until the control range of the AFC circuit (1) is reached. The satellite radio receiver is suitable for connection to satellite receiving installations which comprise a plurality of frequency converters and therefore deviate the nominal receiving frequency in a summary fashion, and for private individual installations which, for economic reasons, possess low frequency stability.

Satellite radio receiver

Signal equalizing method employing test sequences

Apparatus in a receiver for adaptively adjusting the receiver response to changing signal conditions includes a shift register for serially loading signal and having parallel output taps for providing a plurality of signal samples in parallel. Matrix circuitry, coupled to the output taps, is arranged to provide the signal samples in a predetermined order to facilitate forming sums of products of such signal samples.

Adaptive digital filter for multi path distortion cancellation

A system for transmitting and receiving digitalized audio signals, particularly via satellites, wherein data sequences are arranged in timely succession within frames, wherein before transmission, the digitalized audio signal is converted to a digital signal representing the momentary frequency spectrum and, during subsequent coding of the digital audio signal to be transmitted, portions of this transformed signal are given different weights on the basis of psychoacoustic laws with respect to the accuracy of their representation.

Transmission system

In a digital tuning system for a radio receiver, which system includes a station memory having a plurality of memory locations for storing digit representations identifying respective broadcast frequencies to be received, a plurality of station selector elements each connected to be actuatable for addressing a respective memory location to cause the tuning system to tune the receiver to the station identified by the representations stored in the addressed memory location, a plurality of band selector elements each connected to be actuatable for causing the receiver to be tuned within a respective signal band, and components operable for continuously varying the receiving frequency to which the receiver is tuned, the station memory is provided with a plurality of additional memory locations and each band selector element is connected to address, upon being actuated, a respective additional memory location to cause the tuning system to tune the receiver to the station identified by representations stored in the addressed additional memory location, the additional memory locations not being addressable by the station selector elements.

Digital tuning system for a radio receiver

Method and apparatus for the measurement and indication of the position

In a tuning circuit for tuning a receiver to a desired broadcast frequency, which tuning circuit includes a source of counting pulses indicating the magnitude of the change in the frequency value to which the circuit is to be tuned, a counter connected to receive the counting pulses and to assume a count state representative of the broadcast frequency to which the circuit is to be tuned, and a timing member for producing a tuning signal having a value determinative of the frequency to which the circuit is tuned during a tuning operation, the timing member is provided with a unit connected to the source of counting pulses for deriving a control signal representative of the frequency of the pulses, and a unit connected for varying the tuning signal in accordance with the control signal in such a manner that as the frequency of the counting pulses increases, the rate of change of the frequency to which the circuit is tuned is increased.

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Lehrte-Arpke, Germany

Otto Klank