Cselt-centro Studi E Laboratori Telecomunicazioni S.p.a.

Selenia Spazio

Gian B Alaria

Cesare Poggio

Paolo Destefanis

Silvano Appiano

Roberto Preti

Giovanni Ventimiglia

A controller is provided for a baseband switching matrix with one space switching stage. The matrix supplies the controller with a number of service channels (IOTS, CH) of the uplink frames, which channels comprise encoded commands that are decoded by the controller which generates service channels (IOTD, FMC) for the downlink frames and sends them towards the matrix. The controller is subdivided into three functional units: a preprocessing unit (PREL) which decodes uplink frame service channels; a processing unit (ELAB), which receives the commands decoded by the preprocessing unit and/or by a telecontrol station with which it performs a bidirectional dialogue and generates control signals comprising the matrix switching states; and an interface unit (INTM) comprising two memories (MEMA, MEMB) alternatively operating as active or backup memory, which store the switching states supplied by the processing unit and send them to the matrix.

On-board switching controller for a satellite with on-board switching

Television signals generated at a transmitting station are digitized and are then transformed into bit groups by a precoder reducing their information content by eliminating redundancies, as by comparing each pixel of a given frame with the homologous pixel of the immediately preceding frame and, upon detecting their equality, emitting a particular reduction code in lieu of an otherwise emitted luminance signal. A message encoder following the precoder generates outgoing data words which may comprise a luminance value accompanied by an integrity code, a changeover signal accompanied by a reduction code, a numerical value specifying the number of consecutive pixels remaining unchanged from the preceding frame, or a synchronizing code. The bits of the outgoing data words are serialized and are temporarily stored in a buffer register in order to be sent at regular intervals, via a communication channel, to a receiving station where a message decoder regroups them in their original order. The decoder separates the luminance data from the reduction codes under the control of a local clock, re-expands the reduced information and, after checking for transmission errors, converts the received data into luminosity signals designed to reproduce the original television picture.

Coding and decoding method and system for variable-length sequences of

An SS/TDMA communication system comprises a multiplicity of ground stations, including one master station and a number of traffic stations without control function, exchanging digitized voice or other message signals via a relay station aboard a satellite. Each ground station comprises base-band equipment including a transmitting section, a receiving section and a control unit. The control unit of the master station generates outgoing timing signals and processes incoming timing signals for synchronizing the operations of its own equipment and that of the traffic stations with the operation of a switching unit of the satellite-borne relay station; this control unit also emits routing instructions for that switching unit. The transmitting section of each ground station is served by an independent time base while its receiving section has a time base locked to the clock of the satellite; both time bases are adjustable by the associated control unit for correlation with the timing signals sent to and received back from the relay station.

Base-band equipment for ground stations of satellite telecommunication

Digitized message samples or bytes appearing in time slots of an outgoing PCM frame, temporarily allocated to respective local channels such as telephone lines of limited activity, are written during alternate storage periods of, say, 32 ms (each encompassing 256 PCM frames) in a pair of memories from which they are alternately read out in a different sequence to form special packets of interleaved bytes from respective channel pairs or other channel groupings. A number of such special packets are assembled together with other packets from more active channels into an outgoing TDMA frame which forms part of a superframe equal in length to a storage period; the TDMA frames are modulated at an accelerated bit rate upon an r-f carrier for transmission to a relay station aboard a satellite. Upon redistribution of the packets at the relay station according to their respective destinations, they are beamed back to earth for reception by other ground stations. There the special packets of incoming TDMA frames are alternately written, during like storage periods, in another pair of memories from which they are then read out in respective time slots of consecutive incoming PCM frames before being sent to their destinations. A TDMA frame period of each superframe is used to carry a synchronization code generated in the transmitting section and extracted in the receiving section of a ground station for correlating its operation with a clock aboard the satellite.

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Turin, Italy

Gian B Alaria