System for synchronizing a plurality of nodes to concurrently generate output signals by adjusting relative timelags based on a maximum estimated timelag

• US 5,923,902 A
• Filed: 02/19/1997
• Issued: 07/13/1999
• Est. Priority Date: 02/20/1996
• Status: Expired due to Term

• Current Assignee: Yamaha Corporation
• Original Assignee: Yamaha Corporation
• Inventors: Inagaki, Yoshihiro
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): YUAN, CHIEN H
• Application Number:
  US08/800,969
• Time in Patent Office: 874 Days
• Field of Search: 370/350, 370/468, 375/356, 395/551, 395/826, 395/878, 395/879, 395/881, 707/8, 365/189.04
• US Class Current: 710/58
• CPC Class Codes: H04J 3/0664 unidirectional timestamps
• CPC Class Codes: H04J 3/067 Details of the timestamp structure
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 69/28 Timers or timing mechanisms used in protocols
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A network system has a plurality of nodes interconnected to each other for transferring a data packet from a transmitting node to receiving nodes so as to concurrently drive the same. In the transmitting node, an estimating device estimates a time lag which exists between the transmitting node and each of the receiving nodes and which varies among the receiving nodes. A determining device detects a maximum one of the estimated time lags so as to set a reference time by which all of the receiving nodes can be synchronized with each other. A transmitting device transmits a data packet to the receiving nodes together with the reference time stamped on the data packet. In each of the receiving nodes, a receiving device receives the data packet together with the stamped reference time. An adjustment device temporarily retains the received data packet for adjusting the difference in the time lags among the receiving nodes according to the reference time so that all of the receiving nodes can be driven concurrently with each other.

Claims

1. A network system comprising a plurality of nodes that are interconnected to each other and that transfer a data packet from a transmitting node to receiving nodes to concurrently generate output signals by processing the data packet, wherein the transmitting node includes (a) an estimating device that estimates a time lag which exists between the transmitting node and each of the receiving nodes and which varies among the receiving nodes, (b) a determining device that detects a maximum one of the estimated time lags to set a reference time by which all of the receiving nodes can be synchronized with each other to concurrently generate the output signals, and (c) a transmitting device that transmits a data packet to the receiving nodes together with the reference time stamped on the data packet;

and

wherein each of the receiving nodes includes (a) a receiving device that receives the data packet together with the stamped reference time, and (b) an adjustment device that temporarily retains the received data packet to adjust the difference in the time lags among the receiving nodes according to the reference time such that all of the receiving nodes can be driven to concurrently generate the output signals so that final output timings of the output signals are synchronized with each other.

2. A network system according to claim 1, wherein the estimating device estimates a transfer time lag which represents a traveling time of the data packet from the transmitting node to each of the receiving nodes so that the determining device detects a maximum one of the transfer time lags to set the reference time to thereby absorb difference in the transfer time lags among the receiving nodes.

3. A network system according to claim 2, wherein the estimating device estimates the transfer time lag in terms of a hop number counted from the transmitting node to each of the receiving nodes.

4. A network system according to claim 1, wherein the estimating device estimates an operational time lag which represents a time consumed for processing the data packet in each of the receiving nodes so that the determining device detects a maximum one of the estimated operational time lags to set the reference time to thereby absorb difference of the operational time lags among the receiving nodes.

5. A network system according to claim 1, wherein the estimating device estimates a total time lag which is a sum of a transfer time lag and an operational time lag, the transfer time lag representing a traveling time of the data packet from the transmitting node to each of the receiving nodes, and the operational time lag representing a time consumed for processing the data packet in each of the receiving nodes, so that the determining device detects the maximum one of the total transfer time lags as the reference time to thereby absorb difference in the total transfer time lags among the receiving nodes.

6. A network system according to claim 1, wherein the adjustment device temporarily retains the received data packet for an adjustive time interval which is calculated by subtracting the time lag from the reference time.

7. A network system according to claim 1, wherein the transmitting node transmits an audio data packet while each of the receiving nodes operates to generate an output signal, wherein the output signal comprises musical tones according to the audio data packet concurrently with each other when the reference time is reached.

8. A network system comprising a plurality of nodes interconnected to each other for transferring a data packet from a transmitting node to receiving nodes so as to concurrently generate output signals by processing the data packet, wherein the transmitting node includes (a) estimating means for estimating a time lag which exists between the transmitting node and each of the receiving nodes and which varies among the receiving nodes, (b) determining means for detecting a maximum one of the estimated time lags so as to set a reference time by which all of the receiving nodes can be synchronized with each other to concurrently generate the output signals, and to transmitting means for transmitting a data packet to the receiving nodes together with the reference time stamped on the data packet;

and

wherein each of the receiving nodes includes (a) receiving means for receiving the data packet together with the stamped reference time, and (b) adjustment means for temporarily retaining the received data packet for adjusting the difference in the time lags among the receiving nodes according to the reference time such that all of the receiving nodes can be driven to concurrently generate the output signals so that final output timings of the output signals are synchronized with each other.

9. In a network system comprising a plurality of nodes interconnected to each other, a method for transferring a data packet from a transmitting node to receiving nodes so as to concurrently generate output signals by processing the data packet, the method comprising the steps of:

operating the transmitting node for estimating a time lag which exists between the transmitting node and each of the receiving nodes and which varies among the receiving nodes;

detecting a maximum one of the estimated time lags so as to set a reference time by which all of the receiving nodes can be synchronized with each other to concurrently generate the output signals;

transmitting a data packet to the receiving nodes together with the reference time stamped on the data packet;

operating each of the receiving nodes for receiving the data packet together with the stamped reference time; and

temporarily retaining the received data packet for adjusting the difference in the time lags among the receiving nodes according to the reference time such that all of the receiving nodes can be driven to concurrently generate the output signals so that final output timings of the output signals are synchronized with each other.

10. A machine readable media containing instructions for causing a network system composed of a plurality of nodes interconnected to each other to perform a method of transferring a data packet from a transmitting node to receiving nodes so as to concurrently generate output signals by processing the data packet, the method comprising the steps of:

operating the transmitting node for estimating a time lag which exists between the transmitting node and each of the receiving nodes and which varies among the receiving nodes;

detecting a maximum one of the estimated time lags so as to set a reference time by which all of the receiving nodes can be synchronized with each other to concurrently generate the output signals;

transmitting a data packet to the receiving nodes together with the reference time stamped on the data packet;

operating each of the receiving nodes for receiving the data packet together with the stamped reference time; and

temporarily retaining the received data packet for adjusting the difference in the time lags among the receiving nodes according to the reference time such that all of the receiving nodes can be driven to concurrently generate the output signals so that final output timings of the output signals are synchronized with each other.