Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
2000-06-13
2004-06-15
Pezzlo, John (Department: 2662)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S412000, C370S477000, C710S068000
Reexamination Certificate
active
06751215
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an audio band signal transmission system having an audio transmission system which is arranged between a switching system and a cell switching system to transmit an audio band signal via an up line from the cell switching system to the switching system and a down line from the switching system to the cell switching system every connection, and an audio band signal transmission method.
In the prior art, in transmitting the audio signal, such a system is employed that high-efficiency audio compressed coding/decoding processes are performed so as to achieve effective use of the capacity of lines and also one channel is allocated to an audio compressed signal on one line by using time-division multiplex.
However, according to such time-division multiplex, idleness of the lines is generated since channels are still occupied in their idle state. Therefore, in order to achieve the effective use of the lines by such idleness of the lines, the audio signal is divided into compressed-coded audio frames and then transmitted as cells.
According to such system configuration, the method is utilized which enables other lines to utilize the idle transmission lines by transmitting no cell over the idle transmission lines to thus improve statistically a transmission efficiency.
Meanwhile, since compressed-coding cannot be applied to an audio band data signal employed in FAX, MODEM, etc. unlike the audio signal, the audio band data signal is formulated into the cells without compression and then transmitted as it is. Each cell consists of a header area which indicates supplementary information such as an address, data type, etc. and a data area which contains the compressed-coded audio signal or the audio signal per se.
In such above prior art, if the audio band signal transmission system is composed of a large scale network, as disclosed in Patent Application Publication (KOKAI) Hei 9-261239 as shown in
FIG. 22
, the audio band signal is transmitted to a telephone
103
as a calling destination to pass through relay principal points of a switching system
102
via an audio transmission system
100
and a transmission line
101
. At this time, line switching of the audio is carried out at the relay principal points by the switching system
102
.
Therefore, the audio transmission system
100
must absorb cell delay variationcell delay variation by delayed-reading the audio band signal, which is subjected to audio compressed coding by an audio compressed coding portion
2
B, by using a cell delay variationcell delay variation absorbing buffer
3
B, then decode the audio cells into the original state by audio compressed-decoding the audio band signal, which is subjected to cell delay variation absorption by using an audio compressed decoding portion
1
B, and then transfer the decoded audio to the switching system
102
.
Therefore, according to such audio band signal transmission system in the prior art, the message can be transferred between these telephones
103
in the communication network for the relay transmission, nevertheless various processes such as the audio compressed coding process, the audio compressed decoding process, the cell delay variation absorbing process, etc. are carried out repeatedly by the audio compressed coding portion
2
B, the audio compressed decoding portion
1
B, the cell delay variation absorbing buffer
3
B, etc. respectively every audio transmission system
100
even if such processes are not needed. As a result, there is such a problem that, because of such useless processes, not only degradation of the audio quality but also the delay time in process is increased.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems, and it is an object of the present invention to provide an audio band signal transmission system and an audio band signal transmission method, which are capable of suppressing a process delay time to the lowest minimum without degradation of audio quality of an audio band signal.
In order to achieve the above object, according to the present invention, there is provided an audio band signal transmission system having an audio transmission system which is arranged between a switching system and a cell switching system, and transmits an audio band signal via an up line from the cell switching system to the switching system and a down line from the switching system to the cell switching system every connection, and has a cell delay variation absorbing buffer for delayed-reading the audio band signal which is transmitted via the up line, comprising a connection identification number inserting portion provided for every connection, for setting a connection identification number which is to be identified every connection, and inserting own connection identification number into an audio band signal cell which is to be transmitted to the switching system via the up line for own connection; a connection identification number detecting portion provided for every connection, for detecting the connection identification number contained in the audio band signal cell which is to be transmitted from the switching system via the down line for own connection; and a routine correcting portion provided for every connection, for correcting a routine before the audio band signal cell, which is transmitted to the switching system via the up line for own connection in response to a predetermined control signal, is input into the connection identification number inserting portion corresponding to this connection, to thus transmit the audio band signal cell via the down line corresponding to own connection without intervention of the switching system and the cell delay variation absorbing buffer; wherein, when one connection identification number detecting portion of connection identification number detecting portions provided for every connection detects the connection identification number via the down line for own connection, it informs the connection identification number detecting portion which corresponds to the connection identification number to output the predetermined control signal.
Therefore, according to the audio band signal transmission system of the present invention, when it is decided in response to notification issued from other connection identification number detecting portion that the audio band signal cell which is to be transmitted to own connection is transmitted via the communication path which is extended over “the audio transmission system, the switching system, and the audio transmission system” in sequence, the routine of the cell is corrected before the audio band signal cell which is to be transmitted to the switching system via the up line for own connection is input into the connection identification number inserting portion which corresponds to this connection. Hence, the audio band signal cell can be transmitted via the down line corresponding to this own connection, without intervention of the switching system and the cell delay variation absorbing buffer. As a result, a process delay time can be suppressed to the lowest minimum without degradation of the audio quality of the audio band signal by omitting useless processes such as cell disassembling/assembling processes, etc. generated when the cell is transmitted to the switching system, cell delay variation absorbing process by the cell delay variation absorbing buffer, etc.
Also, according to the present invention, there is provided an audio band signal transmission method of transmitting an audio band signal via an up line from a cell switching system to a switching system and a down line from the switching system to the cell switching system every connection by using an audio transmission system arranged between the switching system and the cell switching system, and then delayed-reading the audio band signal, which is transmitted via the up line, by using a cell delay variation absorbing buffer in the audio transmission system, comprising the steps of setting a connection identific
Aoki Masao
Fuse Hidetoshi
Kawanobe Takeshi
Suganuma Toshiya
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
Pezzlo John
LandOfFree
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