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Method of and device for reducing speech-reproduction irregularities in packet-switching telecommunication systems

  • US 4,317,195 A
  • Filed: 03/26/1980
  • Issued: 02/23/1982
  • Est. Priority Date: 03/27/1979
  • Status: Expired due to Term
First Claim
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1. A method of minimizing irregularities in the transmission of speech signals by packets of digitally coded voice samples originating at a first node and arriving at a second node of a routing network in a telecommunication system in which periods of coherent speech are translated into respective sequences of packets labeled with identification codes under the control of a transmission clock at the first node and are arrayed into an outgoing queue at the second node under the control of a reception clock independent of said transmission clock but operating at substantially the same rate, said packets of identical length and being subjected to variable delays in traveling from said first node to said second node,comprising the steps of:

  • determining at the second node, from labels carried by incoming packets, the time of departure of each packet from the first node as measured by said transmission clock;

    correlating the reading of said reception clock with that of said transmission clock at the beginning of voice communication between said nodes on the basis of said departure time and a minimum transit time established by substantially invariable network parameters;

    ascertaining from the departure time of an initial packet of a sequence thereafter arriving as part of said voice communication, and from the reading of the arrival time on the reception clock correlated with the transmission clock, an actual delay undergone by said initial packet;

    comparing said actual delay with a minimum overall delay obtained by adding a supplemental time lag to said minimum transit time;

    storing said initial packet at the second node for a limited time equal to the difference between said minimum overall delay and said actual delay upon the former exceeding the latter;

    releasing the initial packet at the end of said limited time to the output queue of the second node; and

    passing each subsequent packet of the same sequence to said output queue immediately upon arrival at the second node.

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