Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-10-26
2003-06-10
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S442000, C370S395100
Reexamination Certificate
active
06577623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multiplexing technology for processing fixed-length cell data such as an ATM cell, etc. and time-division data in time-division multiplexing communications when these data coexist.
2. Description of the Related Art
Recently, as a private branch LAN, etc. becomes more and more popular with Internet access, intra-net, and groupware, etc. implemented, a WAN communications device is required to integrate and accommodate a conventional voice trunk line and a low-speed data transmission line with a LAN traffic, and to dynamically secure a relay bandwidth of a LAN traffic having a high burst function.
An ATM multiplexing technology for transmitting each piece of data by logically multiplexing fixed-length cell data has been studied as a technology of dynamically using a relay bandwidth mainly for use in a broadband field. Recently, this ATM multiplexing technology has been applied to a narrowband field.
In this case, an existing STM (synchronous transfer mode) exclusive line capable of mainly using a multiplexing access service, etc. is used as a trunk line. In transmitting existing low-rate media information, a delay occurring when data is put in a cell has a large influence on the communications quality. Consequently, there is a need for a multiplexing device capable of integrating an ATM multiplexing technology for efficient transmission and flexible operation under traffic fluctuations into a TDM (time-division multiplexing) technology for exactly guaranteeing the quality of a circuit.
FIG. 1
shows the configuration of the first conventional technology of a multiplexing device. With this multiplexing device, the data communications between terminal ports
103
, between a terminal port
103
and the line port
104
, or between line ports
104
(one of the ports is not shown in the figure) are made through an ATM switch (ATM-SW)
101
and an ATM bus
102
using multiplexed ATM cells.
Therefore, to support the function of utilizing the TDM multiplexing technology, a package for realizing the TDM function is independently developed and implemented such that a realized TDM process can be performed within the package.
FIG. 2
shows the configuration of the second conventional technology of a multiplexing device. With this multiplexing device, a TDM multiplexing unit
201
is completely separate in function from an ATM multiplexing unit
202
, and the data communications between these units are established through a cell assembling/disassembling unit (CLAD)
211
in the ATM multiplexing unit
202
and a CLAD interface unit (CLAD IF)
207
in the TDM multiplexing unit
201
.
A terminal port
205
in the TDM multiplexing unit
201
accommodates a TDM terminal for TDM communications. The TDM multiplexing unit
201
terminates the STM exclusive line for TDM transmission. The data communications between these ports are established through a TDM switch (TDM-SW)
203
and a TDM bus
204
using multiplexed time-division data.
On the other hand, a line port
210
in the ATM multiplexing unit
202
terminates an ATM exclusive line. A terminal port not shown in
FIG. 2
accommodates an ATM terminal which establishes ATM communications. The data communications between these ports are established through an ATM-SW
208
and an ATM bus
209
using a multiplexed ATM cell.
The CLAD IF
207
in the TDM multiplexing unit
201
has the function of multiplexing/demultiplexing time-division data to be put in a cell, and the function of processing the multiplexed time-division data as a frame or multi-frames. The CLAD IF
207
in the TDM multiplexing unit
201
and the CLAD
211
in the ATM multiplexing unit
202
are connected by a TDM multiplexing line
212
in which a frame or multi-frames are put. Then, the CLAD
211
in the ATM multiplexing unit
202
puts in a cell the time-division data which has been multiplexed and put in a frame or multi-frames. It also has the function of converting an ATM cell into time-division data.
Described below is the first case of conventional ways for effective use of resources,in which an ATM cell i's transmitted using an arbitrary time slot of an STM exclusive line through an existing STM exclusive line available mainly for multiplexed access services, etc., not through a large transmission-capacity ATM exclusive line as a trunk line of the ATM cell.
To realize the first case with the configuration according to the first conventional technology shown in
FIG. 1
, it is necessary to realize within the line port
104
the function of terminating the time-division multiplexed data transmitted through the STM exclusive line, and the function of mapping an ATM cell input through. the ATM bus
102
to an arbitrary time slot in the STM exclusive line, and conversely retrieving and outputting to the ATM bus
102
the ATM cell mapped to the optional time slot.
Therefore, if the number of groups of the time slots to which the ATM cells are mapped becomes large, then it is necessary to correspondingly extend the above described conversion function in the line port
104
. Therefore, it is hard to realize a flexible line port
104
, and the number of extended ports is limited.
On the other hand, the first case with the configuration according to the second conventional technology shown in
FIG. 2
can be realized as follows. That is, the line port
210
for terminating time-division data is extended in the ATM multiplexing unit
202
corresponding to each time slot to which ATM cells are mapped. The line port
210
is connected to the terminal port
205
provided in the TDM multiplexing unit
201
. The ATM cell transmitted to and from the line port
210
in the ATM multiplexing unit
202
through the terminal port
205
is mapped to predetermined one or more time slots in the STM exclusive line terminated by a line port
206
.
In this case, when the number of time slots to which the ATM cell is to be mapped increases in the STM exclusive line which terminates the line port
206
, only the line port
210
in the ATM multiplexing unit
202
and the terminal port
205
in the TDM multiplexing unit
201
have to be correspondingly extended. Therefore, with the configuration according to the A second conventional technology, a flexible operation can be realized to some extent when the number of time slots to which an ATM is to be mapped increases.
However, with the configuration according to the second conventional technology, it is necessary to simultaneously extend the line port
210
in the ATM multiplexing unit
202
and the terminal port
205
in the TDM multiplexing unit
201
, thereby causing the problem that the number of packages increases.
Described below is the second case in which an ATM cell contains existing low-rate media data such as modem data, FAX data, etc.
To include low-rate media data in an ATM cell, a CLAD is required to assemble and disassemble the ATM cell. In this case, the low-rate media data has to be mapped to an ATM cell without padding dummy data after the low-rate media data is time-division multiplexed, in order to suppress the delay in putting data in a cell and prevent the reduction in multiplexing efficiency. Furthermore, the function of arbitrarily relay the multiplexed low-rate media data in units of that media data is also required.
To realize the second case with the configuration according to the first conventional technology shown in
FIG. 1
, the terminal port
103
is designed to contain a plurality of terminals which communicate low-rate media data. In the terminal port
103
, the low-rate media data is time-division multiplexed/demultiplexed in units of plural terminals. The corresponding time-division multiplexed data should be mapped to an ATM cell.
As a result, according to the first conventional technology, the low-rate media data which can be time-division multiplexed is limited to the data which can be communicated by a terminal accommodated by the terminal port
103
. Accordingly, there is the problem that it is difficult to realize a flexib
Kawai Yoshio
Mitsumori Yasuyuki
Murakami Shigeharu
Shibuya Kazuhiro
Katten Muchin Zavis & Rosenman
Kizou Hassan
Pezzlo John
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