Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B3/00—Line transmission systems
  • H04B3/54—Systems for transmission via power distribution lines
  • H04B3/542—Systems for transmission via power distribution lines the information being in digital form
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
  • H04L7/0008—Synchronisation information channels, e.g. clock distribution lines
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B2203/00—Indexing scheme relating to line transmission systems
  • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
  • H04B2203/5429—Applications for powerline communications
  • H04B2203/545—Audio/video application, e.g. interphone
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B2203/00—Indexing scheme relating to line transmission systems
  • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
  • H04B2203/5462—Systems for power line communications
  • H04B2203/5495—Systems for power line communications having measurements and testing channel
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/06—Synchronising arrangements
  • H04J3/0635—Clock or time synchronisation in a network
  • H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation

Definitions

• This disclosure relates to power-line modem networks, and more particularly, to an
• Powerline modems communicate by employing a power network as a transmission medium. Powerline modems are employed on a device to set up communication with a
• Such devices on the powerline network may share data including digitally compressed video or picture data.
• a timestamp is typically inserted into the data stream.
• the time stamp provides a reference for the rate in which the
• the present invention provides a plurality of devices having a powerline modem and a clock circuit for synchronizing a data rate.
• the powerline modem permits data
• a synchronization signal is transmitted over the powerline network.
• the synchronization signal includes a carrier operating at a frequency different from the data carriers and provides each of the plurality of devices a time reference to synchronize the data rate.
• invention includes a plurality of devices each having a powerline modem and a clock circuit
• the powerline modem permits data transmission between the plurality of devices over the powerline network on data carriers.
• a master device has a powerline modem coupled to the powerline network and includes a clock transmission circuit.
• the clock transmission circuit generates a synchronization signal over the powerline network
• the synchronization signal includes a carrier operating at a frequency different from the data carriers.
• the synchronization signal provides each of the plurality of devices a time
• transmitting the synchronization signal over a plurality of carriers operating at a frequency different from the data carriers is preferable.
• the step of transmitting a synchronization signal may include the step of sending a current timestamp to the plurality of devices. Each of the plurality of devices then sounds off during an assigned
• a correction factor is transmitted to the plurality of devices to correct synchronization of the clock circuit of the devices, which may include error offsets.
• FIG. 1 is a block/flow diagram showing a system/method for synchronizing a
• FIG. 2 is a diagram showing time slot allocation in accordance with an embodiment of
• the present invention synchronizes devices by employing one or more subcarrier
• a powerline modem network includes a plurality of powerline modem devices.
• Devices, which are serviced by the powerline modems, may include devices capable of
• the present invention provides synchronization for such devices to ensure a proper display rate.
• synchronization By employing additional subcarriers, synchronization
• the synchronization signals may be distributed over the network without reducing bandwidth of data subcarriers.
• the synchronization signals permit different devices with different standards
• Powerline modems communicate by employing a power network as a transmission medium. Powerline modems are employed on a device to set up communication with a master device or controller. Communication carried out on the powerline provides the
• Powerline devices may include devices capable of displaying video.
• the present invention describes a way to
• timing synchronization for devices transmitting digitally compressed video or other type of data that needs a time reference (e.g. MPEG data for video) over a powerline modem network.
• a time reference e.g. MPEG data for video
• timing synchronization is maintained between a transmitter and a receiver in accordance with timing information communicated over a subcarrier frequency to display
• a powerline network 12 which may include a hardwired electrical power system for a home
• NCR/DND or other media player (e.g., CD, etc.), a television, a monitor or any other display
• FIG. 1 illustratively depicts a network with three devices.
• a device 14 includes a master device, and device 16 and 18 include slave devices (labeled slave 1 and slave 2, respectively).
• Each device 14, 16 and 18 includes a powerline modem 20.
• Each powerline modem is capable of communication on powerline network 12, which permits communication
• Each of devices 16 and 18 includes a clock synchronization circuit 22, and master device 14 includes a clock
• Each powerline modem 20 includes a transmitter/receiver 26, which transmit and receive data on predetermined data subcarrier frequencies or data
• Powerline modems 20 employ a multicarrier modulation format in which data is
• Clock synch circuit 24 generates synch carrier 30. Clock circuits 22 listen for the
• synch carrier 30 uses the signal to synchronize data received by receivers 26.
• a particularly useful feature of the present invention permits asynchronous devices to be able to display synchronized video. That is, since, for example, MPEG synchronization occurs on a
• synch subcarrier 30 that is separate from the data
• devices e.g., devices 16 and 18
• Timing information that will be used to play back the MPEG video.
• Other data formats contemplated include video, audio or other applications.
• FIG. 2 is a table showing time slots 1-5 for the master device 14 and slave 1 and slave 2 devices (16 and 18
• This illustrative example is for a network with one master and two slave devices; however, a network with multiple slaves and even a hierarchical system of master
• Master (14) sends out a timestamp during one slot (slot 1) to provide
• slave 1 's time slot is slot 2 while slave 2's time slot is slot
• slave 1 and slave 2 may be either early or late in sounding off. Errors in synchronization manifest themselves using this sound-off procedure.
• the error may be determined as an offset between the slave's time slot start point and the actual transmitted sound-off start point indicated as errors 54 and 56. Based on possible errors
• the master then sends each of the slaves a correction factor 58 and 60 to adjust the clocks of slave 1 and slave 2.
• the correction factors 58 and 60 are sent during dedicated slots, e.g., slots 4 and 5.
• Devices having different standards, such as for example, different operating frequencies or different synchronization needs are permitted to derive a timing reference from synch subcarrier(s) 30.
• information on synch sub-carrier 30 may be asynchronous with the information on data subcarriers 28. This permits both fast and slow
• Each device in the system may have a clock resolution that maybe different from a synchronizing subcarrier frequency. While the synchronization subcarrier provides a certain
• the devices themselves may have a mechanism to interpret this information to update their own clocks, which may have a different resolution. In one embodiment, this can be accomplished by dropping the lower
• OFDM Orthogonal Frequency Division Multiplexing
• the subcarriers for such systems may be in the frequency ranges of between about 1 to about 30 MHz.
• subcarriers may be spaced between each frequency interval, however, such an implementation
• Possible embodiments of the present invention add an additional subcarrier(s) at the next available frequency interval(s) for synchronization purposes, or alternately dedicate a plurality of data subcarriers for synchronization purposes.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Power Engineering (AREA)
• Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
• Synchronisation In Digital Transmission Systems (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (2)

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ID=25243450

Family Applications (1)

Country Status (11)

Cited By (1)

Families Citing this family (38)

Family Cites Families (7)

• 2001
  • 2001-04-03 US US09/825,232 patent/US6834091B2/en not_active Expired - Lifetime
• 2002
  • 2002-04-02 MY MYPI20021190A patent/MY128467A/en unknown
  • 2002-04-03 BR BR0208321-3A patent/BR0208321A/pt not_active IP Right Cessation
  • 2002-04-03 JP JP2002580547A patent/JP4360522B2/ja not_active Expired - Fee Related
  • 2002-04-03 DE DE60207613T patent/DE60207613T2/de not_active Expired - Lifetime
  • 2002-04-03 CN CNB028077679A patent/CN100481748C/zh not_active Expired - Fee Related
  • 2002-04-03 KR KR10-2003-7012962A patent/KR20040007487A/ko not_active Ceased
  • 2002-04-03 AU AU2002256080A patent/AU2002256080A1/en not_active Abandoned
  • 2002-04-03 MX MXPA03009069A patent/MXPA03009069A/es active IP Right Grant
  • 2002-04-03 EP EP02725521A patent/EP1464136B1/en not_active Expired - Lifetime
  • 2002-04-03 WO PCT/US2002/010613 patent/WO2002082712A2/en not_active Ceased

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