Data transmission protocol method and apparatus

• US 5,854,840 A
• Filed: 05/20/1997
• Issued: 12/29/1998
• Est. Priority Date: 04/26/1995
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Cannella, James E. Jr.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US08/859,262
• Time in Patent Office: 588 Days
• Field of Search: 380/9, 380/49
• US Class Current: 380/268
• CPC Class Codes: H04L 12/56 Packet switching systems
• CPC Class Codes: H04L 2007/045 Fill bit or bits, idle words
• CPC Class Codes: H04L 25/45 using electronic distributors
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/65 Network streaming protocols, e.g. real-time transport protocol [RTP] or real-time control protocol [RTCP]
• CPC Class Codes: H04L 65/70 Media network packetisation
• CPC Class Codes: H04L 69/323 in the physical layer [OSI layer 1]
• CPC Class Codes: H04L 69/324 in the data link layer [OSI layer 2], e.g. HDLC
• CPC Class Codes: H04L 7/046 using a dotting sequence
• CPC Class Codes: H04L 7/048 using the properties of error detecting or error correcting codes, e.g. parity as synchronisation signal
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04N 21/2381 Adapting the multiplex stream to a specific network, e.g. an Internet Protocol [IP] network transmission of MPEG streams over ATM H04L12/5601
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/242 Synchronization processes, e.g. processing of PCR [Program Clock References] arrangements for synchronising broadcast or distribution via plural systems in broadcast distribution systems H04H20/18
• CPC Class Codes: H04N 21/4305 Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/4363 Adapting the video stream to a specific local network, e.g. a Bluetooth® network
• CPC Class Codes: H04N 21/4381 Recovering the multiplex stream from a specific network, e.g. recovering MPEG packets from ATM cells transmission of MPEG streams over ATM H04L12/5601
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 7/1675 Providing digital key or authorisation information for generation or regeneration of the scrambling sequence pseudo-random number generators in general G06F7/58
• CPC Class Codes: H04N 7/52 : Systems for transmission of a pulse code modulated video signal with one or more other pulse code modulated signals, e.g. an audio signal or a synchronizing signal assembling of a multiplex stream by combining a video stream with other content or additional data, remultiplexing of multiplex streams, insertion of stuffing bits into the multiplex stream, assembling of a packetised elementary stream at server side H04N21/236; disassembling of a multiplex stream, remultiplexing of multiplex streams, extraction or processing of Service Information, disassembling of packetised elementary stream at client side H04N21/434

Abstract

A data communications protocol for single path media having low data error rate requires the generation of a data packet with a start code field having a predetermined pattern, a byte count field for defining a data field having a maximum predetermined length in bytes, a data payload field having a byte count according to the value of the byte count field and a cyclic redundancy check field of predetermined length. The value of the byte count field may be fixed, may be changed from packet to packet or may be changed upon initialization. The described data communications protocol permits utilization with data types varying from high definition television to alarm reporting applications. Moreover, the data rate may be varied by varying an idle time signal duration up to a maximum (when the idle time signal duration is reduced to zero). According to one exemplary embodiment for plastic fiber optic media, MPEG2 transport stream packets may be transmitted at 54 MBaud over distances of 20 meters or even more with other media.

Claims

1. Physical layer data signal originating apparatus for application with a single optical fiber comprising

a time base generator for generating a signal at a predetermined signaling rate,

a channel coder comprising a data scrambler and a run-length activated inverter coupled to the time base and to an output of the scrambler, and

a transmitter including an LED optical source and driver circuitry responsive to the output of the channel coder for outputing a signal to the optical fiber.

2. The physical layer data signal originating apparatus according to claim 1 wherein said data scrambler scrambles the digital data according to a pseudo-random bit sequence generated according to a polynomial.

3. Physical layer data signal receiving apparatus for application with a single optical fiber comprising

a receiver including an optical detector and a clock recovery circuit responsive to the optical detector and

a channel decoder comprising a run-length activated inverter and a descrambler, the channel decoder outputing clock and data to a link layer circuit.

4. Physical layer data signal receiving apparatus according to claim 3 wherein said data descrambler descrambles the digital data according to a pseudorandom bit sequence generated according to a polynomial.