ATM data controller

Details ATM data controller ATM data controller

1998-11-20

2001-09-11

Ngo, Ricky (Department: 2664)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S412000, C370S429000, C370S474000, C370S477000, C370S521000, C375S241000

Reexamination Certificate

active

06289020

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an ATM data controller to be provided between an ATM (Asynchronous Transfer Mode) interface and a data processing system to be connected to the ATM interface, for controlling data exchange between the ATM interface and the data processing system, and particularly to the ATM data controller having a function for compressing and decompressing data to be exchanged between them.
In a Japanese patent application entitled “A Relay/Exchange System of Compressed Vocal Data in an ATM Network”, laid open as a Provisional Publication No. 055753/'97, there is disclosed a prior art for reducing quality degradation and relaying delay of vocal data in a relay/exchange system connected to an ATM network wherein the vocal data are exchanged being compressed into low bit-rate digital data.
FIG. 8
is a block diagram illustrating the relay/exchange system of the prior art.
Referring to
FIG. 8
, a voice terminal
30
, such as a telephone, is connected to an ATM network by way of a digital exchange
20
, and a cell assembling/disassembling unit
10
is provided between the digital exchange
20
and the ATM network, which takes charge of compression/decompression of the vocal data together with assemble/disassemble of ATM cells. A cell assembling/disassembling unit having the same configuration with the cell assembling/disassembling unit
10
is provided for each pair of trunk lines (not depicted in the drawings) of the digital exchange
20
.
The cell assembling/disassembling unit
10
comprises a CDV (Cell-Delay-Variation) absorbing buffer
111
for buffering ATM cells received from the ATM network, a CDV absorption controller
112
, a cell disassembling section
113
, a decompression section
114
and a first selector
115
. The cell disassembling section
113
reproduces compressed digital vocal data by disassembling ATM cells read out from the CDV absorbing buffer
111
. The decompression section
114
decompresses the compressed digital vocal data into digital vocal data. The first selector selects data to be transferred to the digital exchange
20
from either of the digital vocal data outputted from the decompression section
114
or the ATM cells directly read out from the CDV absorbing buffer
111
.
The cell assembling/disassembling unit
10
also comprises a compression section
121
, a cell assembling section
122
, a second selector
123
, and a relay/exchange detection section
131
. The compression section
121
compresses digital vocal data supplied from the digital exchange
20
into compressed digital vocal data of a low bit rate, which is assembled into ATM cells by the cell assembling section
122
. The second selector
123
selects data to be transmitted to the ATM network from either of ATM cells assembled by the cell assembling section
122
or the data directly supplied from the digital exchange
20
.
The relay/exchange detection section
131
takes charge of discriminating whether the data supplied from the digital exchange
20
is the data originated from a voice terminal
30
accommodated in the digital exchange, or the data relayed by another digital exchange by way of the ATM network, and controls the first and the second selector
115
and
123
according to the discrimination result.
When the data supplied from the digital exchange
20
is found to be the data relayed from another digital exchange through the ATM network, the relay/exchange detection section
131
controls the first selector
115
to select ATM cells directly read out from the CDV absorbing buffer
111
and the second selector
123
to select the data supplied directly from the digital exchange
20
, because the ATM cells received from the ATM network are also to be relayed to the other digital exchange through the ATM network.
Thus, unnecessary decompression and compression of the vocal data to be relayed by the digital exchange
20
from the ATM network to the ATM network are avoided, and the quality degradation and the relaying delay of the vocal data are prevented, in the relay/exchange system according to the prior art.
However, there are problems in the prior art of
FIG. 8
, when it is applied as an ATM data controller for controlling data exchange between an ATM interface and a data processing system to be connected to the ATM interface.
A first problem is that the transmission efficiency of the ATM network cannot be made high because the cell assembling/disassembling unit
10
of
FIG. 8
has no CDV-absorbing buffer for buffering ATM cells to be transmitted to the ATM network. When the data supplied from the digital exchange
20
is the digital vocal data originated from the voice terminal
30
, it is assembled into ATM cells after compressed by the compressing section
121
according to the recommendation G. 728 of the ITU-T standard, for example. Therefore, a time interval for the data compression is needed after a cell is transmitted until a next cell is prepared, which makes low the transmission efficiency of the ATM network.
A second problem is that operational load of a CPU of the ATM data controller becomes high, because such data compression/decompression as above described is usually implemented by a software program executed by the CPU, when the ATM data controller performs the data compression/decompression between the data processing system and the ATM interface. Therefore, the operational load of the CPU taken by the data compression/decompression may obstruct other processing to be performed by the CPU.
A third problem is that transmission rate of data other than the vocal data is limited within the cell-transfer-rate of the ATM network, because the cell assembling/disassembling unit
10
of
FIG. 8
has
110
means for compressing or decompressing data other than the digital vocal data.
SUMMARY OF THE INVENTION
Therefore, a primary object of the present invention is to provide an ATM data controller for controlling data exchange between an ATM interface and a data processing system to be connected to the ATM interface, whereby ATM cells are assembled and disassembled without degrading transmission efficiency of the ATM network and numeral data is compressed and decompressed without needing CPU load.
In order to achieve the object, an ATM data controller of the invention for controlling data exchange between a data processing system and an ATM interface comprises:
a first data buffer for buffering transmission data supplied from and received data to be supplied to the data processing system;
a third data buffer for buffering transmission ATM cells to be transmitted to and received ATM cells received from the ATM interface;
a second data buffer for buffering transmission cell data to be assembled into the transmission ATM cells and received cell data obtained by disassembling the received ATM cells;
a data compressing/decompressing means for compressing the transmission data into the transmission cell data when the data compressing/decompressing means is controlled to compress the transmission data, controlling the second data buffer to buffer the transmission cell data supplied from the data compression/decompression means when the data compressing/decompressing means is controlled to compress the transmission data and to buffer the transmission data directly outputted from the first data buffer when the data compressing/decompressing means is not controlled to compress the transmission data, and decompressing the received cell data supplied from the second data buffer into the received data when the data compressing/decompressing means is controlled to decompress the received cell data;
an ATM interface control section for assembling the transmission ATM cells by adding cell-headers onto the transmission cell data, in the cell-headers data-compression flags being set when the ATM interface control section is controlled to set the data-compression flags, disassembling the received ATM cells into the received cell data by deleting cell-headers from the received ATM cells, and controlling the second data buffer to

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