Speech packet switching method and device

• US 4,453,247 A
• Filed: 03/03/1982
• Issued: 06/05/1984
• Est. Priority Date: 03/27/1981
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kato, Takao, Terada, Matsuaki, Suzuki, Michio, Toki, Ryuichi
• Primary Examiner(s): Olms, Douglas W.
• Application Number:
  US06/354,182
• Time in Patent Office: 825 Days
• Field of Search: 370/94, 370/60
• US Class Current: 370/252
• 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 speech packet switching system, an input speech signal to a speech packet transmitting station is converted to a digital signal to form speech data blocks, which are discriminated to talkspurt blocks and silence blocks, and only the talkspurt speech blocks are packetized and transmitted through a speech packet switching network. In a receiving station, a series of speech packets received in one talkspurt period are temporarily stored in a variance absorbing buffer to compensate for a variance of transmission delay times resulting from the transmission through said speech packet switching network to add variance absorbing times to the speech packets depending on the transmission delay times of the respective speech packets. Then the speech packets are sequentially reproduced. A size of the variance absorbing buffer is determined by a variance of the transmission delay times of the speech packets received in one talkspurt period and the size of the variance absorbing buffer for the next talkspurt period is dynamically changed based on the determined size. A constant speech quality is assured to a change of the variance of the transmission delay times of the speech packets due to a change of traffic in the speech packet switching network.

Claims

1. In a speech packet switching system having receiving means for receiving speech packets transmitted via a speech packet switching network, a variance absorbing buffer for temporarily storing therein the speech packets received by said receiving means to compensate for a variance of transmission delay times resulting from the transmission through said speed packet switching network, and reproducing means for reproducing the speech packets serially read out from said variance absorbing buffer,

a speech packet switching method comprising the steps of:

determining a variance of transmission delay times of the speech packets in a talkspurt period received by said receiving means;

determining a size of said variance absorbing buffer corresponding to the determined variance; and

dynamically changing the size of said variance absorbing buffer for the next talkspurt period based on the determined size.

2. A speech packet switching system comprising:

receiving means for receiving speech packets transmitted via a speech packet switching network;

a variance absorbing buffer for temporarily storing therein the speech packets received by said receiving means;

reproducing means for reproducing the speech packets read out from said variance absorbing buffer;

computing means for calculating a variance of transmission delay times of the speech packets in a talkspurt period received by said receiving means and calculating a size of said variance absorbing buffer corresponding to said variance; and

means for dynamically changing the size of said variance absorbing buffer for the next talkspurt period based on the size determined by said computing means.