U.S. Philips Corporation

Telecommunications Radioelectriques Et Telephoniques

501 Telecommunications Radioelectriques Et Telephoniques T.r.t.

Roger P Alexis

Loic B Guidoux

Bahman Barazeche

Marc Chelouche

Claude Pirolli

An information transmission arrangement comprising transceiver units (1, 2) located in a propagation medium (10) whose attentuation varies as a function of frequency. At least one unit (1) comprise a meter (67) for measuring the level of the received signal in order to influence the frequency variation control (32) of the control oscillator (28) in the send circuit (26, 28) of the other unit (2). This arrangement profits from a monotonic attenuation gradient of the propagation medium (10) having a zone (Z1) in the 50-60 GHz band to control the send level in a simple and effective manner.

Transceiver arrangement for optimizing received signal levels

In a mobile radio system, a method and apparatus for enabling a mobile station (M) to select a free duplex communication channel for communication with a fixed station (F). The fixed stations in the system detect duplex channels which are engaged in their rising paths and transmit a list of such engaged duplex channels over a signalling path. The fixed stations further transmit over such signalling path, in time division channels respectively allocated to them, a list of the duplex channels which they use and which are engaged in the descending paths. In the mobile station (M) the power levels of the signals received in the signalling path are measured and compared with an interference threshold power level to identify duplex channels of interfering fixed stations. A free duplex channel of a fixed station (F) is selected by the mobile station (M) by excluding channels of interfering fixed stations and channels of fixed station (F) which are engaged.

Method and apparatus for selecting a free channel in a mobile radio

The filter coefficients of an echo cancelling arrangement having a near echo canceller and a distant echo canceller are initialized in accordance with a method and apparatus wherein the following steps are performed:

Method and apparatus for initializing filter coefficients in an echo

A method of two-way radiocommunication between fixed stations and mobile stations permitting effective utilization of available radiocommunication channels. All the fixed stations transmit in a first radio path of multiplexed communication channels and all the mobile stations transmit in a second radio path of multiplexed communication channels, each pair of communication channels in the first and second paths being capable of handling two-way communication between any one of the fixed stations and any one of the mobile stations. When the channels are time-division multiplexed, in accordance with the TDMA-type method, only two numerical paths are utilized. When the channels are frequency-division multiplexed, in accordance with the FDMA-type method, only two frequency bands are allocated to radiocommunications.

Method of two-way radiocommunication between fixed stations and mobile

Method and apparatus for measuring the delay of the distant echo in an echo ancelling arrangement comprising a near echo canceller, a delay line and a distant echo canceller using the steps of

Method and apparatus for measuring distant echo delay in an echo

In this system in which the information signals to be transmitted are converted into the digital form, transmission is done via a frequency-division multiplexer which so transmit the bits of the information signals in parallel that the duration of the bits transmitted through the channels of the multiplexer is longer than double the difference in propagation time between two carriers obtained from the two transmitters which are nearest in the receiving zone, where the said carriers have levels which are near to one another. This solves the problem of overlap between the information signals. To control the problem of fading, three types of transmitters which have three carriers whose deviation is very small compared with the bandwith of a channel are used in the transmitter network.

Digital radio transmission system for transmitting a plurality of

According to the invention, it is proposed to use the code words D as the spreading word for the spectrum. The auto-correlation function of these words have zero values for all even temporary shifts other than the zero shift, the auto-correlation function then assuming the maximum or the minimum value. In addition, use is made of the secondary lobes of this auto-correlation function for carrying out, at the receiving end, the synchronization of a clock in the rhythm of the binary elements forming the spreading code words. Use: counteracting radio-electric interferences.

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Neuilly sur Seine, France

Roger P Alexis