System for digitized voice and data with means to compensate for variable path delays

• US 4,538,259 A
• Filed: 07/05/1983
• Issued: 08/27/1985
• Est. Priority Date: 07/05/1983
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Moore, Brian B.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Scutch, III, Frank M.
• Application Number:
  US06/511,059
• Time in Patent Office: 784 Days
• Field of Search: 370/60, 370/94, 370/58, 370/85
• US Class Current: 370/394
• CPC Class Codes: H04J 3/0632 Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES] queuing arrangements in packet switching elements H04L49/90; synchronising systems for the synchronous transmission of a pulse code modulated video signal with one or more other pulse code modulated signals H04N7/56
• CPC Class Codes: H04L 12/64 Hybrid switching systems

Abstract

In a communications system in which voice is transmitted as packets of digitized samples, a receiving station delays the output of the first packet in a way that compensates for wide variations in the intervals at which successive packets are received. According to one feature of this system, a first packet is transmitted at a higher priority so that a greater delay can be used without encounter problems that arise from the uncertainty in the delay in transmitting this packet. In another feature of this system, the arrival time of the first few packets of a conversation are detected and the delay is readjusted in case the first packet has been unusually delayed.

Claims

1. In a communication system of the type in which voice signals for a sending station are formed into a packet and in which Packets from several sending stations are combined into a message and are transmitted to intended receiving stations, the system having alternate pathways through intermediate stations such that messages containing first or subsequent packets in a conversation may arrive at an intended receiving station at varying times in relation of the time when the voice signal originated, the intermediate stations having means for handling a message according to a priority carried by the message, and in which the receiving station has means for delaying the output of the first packet of a conversation to compensate for variations in the delays of said subsequent packets, the improvement comprising,

means at the sending station for designating a message containing a first packet of a conversation to have a higher priority and for designating messages not containing a first packet of a conversation to have a lower priority,

whereby the range of delays for the first packet of a conversation transmitted through said pathways is less than the range of delays for packets transmitted at a lower priority and thereby a reduction is made in the range of the minimum time interval between the latest arrival of said first packet of a conversation and the earliest arrival of a message containing the next packet of the same conversation, and

means in a receiving station for delaying the first packet by an amount that is related to the more closely defined range of time intervals between said first packet and said next packet and is appropriate to a wide range of delays in the subsequent messages.

2. In the system defined in claim 1, the improvement comprising,

means in a receiving station for detecting the time occurrence of a few packets following the first packet, and

means for giving an additional time delay to one of the first few packets to correspond to delays encountered by said following few packets,

whereby the system is adapted to a wide range in the distribution of delays in subsequent packets.

3. The system of claim 2 wherein the means for detecting the relative arrival times of the next few packets after the first sample comprises,

means for detecting the times of arrival of a number of packets that is typically silence at the beginning of a voice conversation,

whereby the system adjusts the delay before the typical voice signal begins.

4. The system of claim 2 wherein the system comprises means for buffering a small number of samples, and wherein

the means for detecting the times of arrival of the next few samples comprises,

means for detecting an overflow of the buffering means.

5. The system of claim 4 wherein the means for detecting the times of arrives comprises means for detecting an underflow of the buffering means.