Scientific-atlanta, Inc.

Steven S Lawrence

Christopher H Birch

Paul D Nicholas

Christian V Van Staden

Walter R Brooks

Mark J D'Sylva

Robert Strother-Stewart

A multiplex frame format for transmitting digital data in a data transmission system comprises a PACKETS portion comprising a highly error-protected region and a region having only Reed Solomon encoding as an error protection measure, the PACKETS portion including low speed data. The frame format also comprises portions for transmitting medium (AUDIO) and high speed (VIDEO) data streams following the PACKETS portion. Prior to transmission, the composed frame comprising the PACKETS, AUDIO and VIDEO portions is interleaved and the BLOCK SYNC and FRAME SYNC are added. A multiplex structure control packet word of the PACKETS portion immediately follows FRAME SYNC. Thus, the FRAME SYNC word defines where interleaving begins. A demultiplexer in concert with a microcontroller of a decoder decodes the multiplex structure control word and related PACKETS and outputs digital data streams to related output peripheral processors. The BLOCK SYNC word preferably comprises one eight bit byte and contains network signaling or other data at predetermined bit positions within the word. Moreover, the frame format is flexible and may vary in horizontal and vertical dimensions as digital service streams are varied due to service requirements or priorities. The multiplexers for forming the frame according to the present invention may be arranged in redundant (hot standby) or in multi-service arrangements synchronized by a synchronizing waveform, digitally generated to comprise a continuous 3.375 MHz portion and a single cycle frame marking signal of greater magnitude but significantly lower frequency.

System and method for transmitting a plurality of digital services

In a receiver for receiving a carrier modulated with data, there is provided a system for locating and tracking said carrier. The carrier is located by sweeping a frequency range containing said carrier. False lockup are inherent when a wide frequency sweep demodulator attempts to lock onto a carrier, and the system recognizes such lockups by monitoring data from a Viterbi error correction circuit. On false lockup, the system breaks the lockup and continues the sweep until the true data carrier is located and tracked.

Method and apparatus for locating and tracking a QPSK carrier

Synchronizing waveform generator

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Toronto, Canada

Steven S Lawrence