Multiplex communications – Communication techniques for information carried in plural... – Assembly or disassembly of messages having address headers
Reexamination Certificate
1998-07-27
2002-08-27
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication techniques for information carried in plural...
Assembly or disassembly of messages having address headers
C370S477000, C370S252000, C370S395300
Reexamination Certificate
active
06442175
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to technology for enhancing the communication quality of communication data such as voice data, when the data is relayed by transmission equipment in a network which transmits fixed-length cells, such as an ATM (asynchronous transfer mode) network.
2. Description of the Related Art
In a case where TDM (time division multiplexing) equipment are to be replaced with ATM equipment by exploiting a direction selecting function based on exchanges which are used in an existing network built up of the TDM equipment, it is requested that voice of short delay and high quality having been obtained in the TDM network be maintained even after the shift to the ATM network.
FIG. 1
is a diagram showing the architecture of a prior-art, voice data relaying system which employs TDM equipment.
In each TDM equipment
1502
for connecting exchanges
1501
as shown in
FIG. 1
, the delay (transmission delay) of data within the equipment is slight. Therefore, even when the voice data is relayed by the plurality of TDM equipment
1502
, the delay thereof poses no problem.
However, in a case where a CODEC (coder/decoder) block being a device which codes and decodes voice data by the use of compression technology is installed in each TDM equipment
1502
in order to effectively utilize a transmission line, the relaying of the voice data by the plurality of TDM equipment
1502
results in degrading the communication quality of this voice data. The reason therefor is that the operations of voice coding/decoding are repeated for the number of times corresponding to the number of times of relaying, to increase the degradation of a voice quality attributed to the coding/decoding and the delay of the voice data attributed to voice compression.
In the example of
FIG. 1
, the TDM equipment
1502
(#
2
) to which the exchange
1501
(#
2
) of a relay station is connected between the exchange
1501
(#
1
) in which a telephone set having called out is accommodated and the exchange
1501
(#
3
) in which a telephone set to call to is accommodated. On this occasion, the degradation of the communication quality of the voice data increases in the two CODEC blocks which are included in the TDM equipment
1502
(#
2
).
There have been known various techniques collectively called digital one-link relaying technology wherein, in order to prevent the delay and the quality degradation which are incurred by the coding/decoding of the voice data in the relaying office, the voice data is not coded/decoded in the TDM equipment
1502
(#
2
) serving as the relaying office, whereby the number of times of the operations of coding/decoding the voice data matches the number of times corresponding to one link of the TDM equipment
1502
.
In the example of
FIG. 1
, in a case where the exchange
1501
(#
2
) does not operate as the relaying office, that is, in a case where the exchange
1501
(#
2
) is an office to which a telephone set having called out is connected or an office to which a telephone set to call in is connected, the CODEC block of the TDM equipment
1502
(#
2
) functions, so that the data which is transmitted between the TDM equipment
1502
(#
2
) and the exchange
1501
(#
2
) becomes decoded original voice data.
On the other hand, in a case where the exchange
1501
(#
2
) operates as the relaying office, the CODEC blocks of the TDM equipment
1502
(#
2
) do not function, so that the data which is relayed and transmitted in both ways between the TDM equipment
1502
(#
2
) and the exchange
1501
(#
2
) remains coded voice data.
In this case, the data which is transmitted bears passing-particular-equipment identification data for identifying whether or not the exchange
1501
(#
2
) is to operate as the relaying office (that is, whether or not the particular equipment is to be passed). The TDM equipment
1502
(#
2
) judges the passing-particular-equipment identification data, whereby the CODEC blocks are controlled to be valid/invalid.
Owing to such digital one-link relaying technology, voice communications of high quality can be realized in the TDM network even when a plurality of relaying equipment exist.
Meanwhile, in recent years, it has come to be eagerly requested that a TDM network be replaced with an ATM network for the purposes of heightening the transmission speed of communications and enlarging the traffic volume thereof.
FIG. 2
is a diagram showing the architecture of a prior-art, voice data switching system which employs ATM equipment
1601
substituted for the TDM equipment
1502
in the TDM network depicted in FIG.
1
.
Referring to
FIG. 2
, a CLAD (cell assembly/disassembly) block installed in each ATM equipment
1601
is a device which assembles voice data into an ATM cell and which disassembles an ATM cell into voice data.
Besides, an ATM cell switch block installed in each ATM equipment
1601
operates as illustrated in FIG.
3
. More specifically, the ATM cell switch block analyzes destination information affixed to the header part of the ATM cell which is entered from a port lying on the side of the CLAD block, so as to switch the ATM cell in the direction of a destination, and it alters the destination information of the header part to one corresponding to the next relaying destination and then delivers the resulting ATM cell to a port lying on the side of a transmission line. Also, regarding the ATM cell which is reversely entered from a port lying on the side of the transmission line, the ATM cell switch block analyzes destination information affixed to the header part of the entered ATM cell so as to switch this cell, and it alters the destination information of the header part and then delivers the resulting ATM cell to a port lying on the side of the CODEC block as corresponds to the next destination.
In general, a data transmission rate at the input/output port of an ATM cell switch block to which a CLAD block is connected is very high, so that the input/output port can process data of large traffic volume (ATM cell). In contrast, since data to be processed by the CLAD block is only voice data, a data processing rate in the CLAD block is much lower than the data transmission rate at the input/output port of the ATM cell switch block. In order to effectively use the data transmission capacity of the input/output port of the ATM cell switch block, therefore, a plurality of CLAD blocks are often connected to one input/output port.
In the architecture depicted in
FIG. 2
, the ATM equipment
1601
form paths which are always fixed, among the respective exchanges
1501
.
With the prior art illustrated in
FIG. 2
, however, the process for assembling or disassembling the ATM cell for the voice data is required in the CLAD block within each ATM equipment
1601
even in the case of adopting the vocal digital one-link relaying technology which employs the passing-particular-equipment identification data or the like and which has been realized in the TDM network. The prior art therefore has the problem that delays ascribable to the cell assembly/disassembly in the two CLAD blocks within the ATM equipment
1601
to which the exchange
1501
(#
2
) of the relaying office is connected are accumulated, resulting in the increase of a delay in the understanding of the voice data.
FIG. 4
is a diagram showing the architecture of another prior-art, voice data relaying system which employs ATM equipment
1601
substituted for the TDM equipment
1502
in the TDM network depicted in FIG.
1
.
The architecture in
FIG. 4
differs from the architecture in
FIG. 2
in the point that a signalling termination block for receiving and analyzing the signalling information of voice is installed in each ATM equipment
1601
, and that a dynamic path extending from a calling office (the exchange
1501
in which a telephone set having called out is accommodated) to a final called office (the exchange
1501
in which a telephone set to call in is accommodated) is formed in the A
Katten Muchin Zavis & Rosenman
Kizou Hassan
Pezzlo John
LandOfFree
Digital one-link relaying system for communication data in a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Digital one-link relaying system for communication data in a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digital one-link relaying system for communication data in a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2887641