Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-09-25
2002-11-26
Cangialosi, Salvatore (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S541000
Reexamination Certificate
active
06487223
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission apparatus based on the Synchronous Digital Hierarchy (SDH), and more particularly to an SDH transmission apparatus having a highly flexible system configuration.
2. Description of the Related Art
Recent advancement in international standardization of SDH transmission systems have accelerated the development of many types of standard multiplex transmission units, allowing a variety of digital transmission systems to be integrated in different ways. To meet the various needs, however, it is desired to develop such an SDH transmission apparatus that is equipped with a versatile mechanism to cross-connect low-order and high-order group transmission units, while allowing various classes of digital bitstreams to be handled with simple internal structure, regardless of their levels in the SDH multiplexing hierarchy.
Here, a few examples of conventional transmission apparatus are presented in
FIGS. 30
to
32
.
FIG. 30
shows a transmission apparatus which has a cross-connect unit
101
to interconnect high-level group units including two STM-1 units
102
and
103
, and low-order group units including a plurality of 2M units
104
. The STM-1 units
102
and
103
are SDH transmission apparatus serving as multiplex/demultiplex facilities, which convert the signal frames from the Synchronous Transfer Module Level 1 (STM1) format to the Administrative Unit-
4
(AU-4) format, and vice versa. They provide the cross-connect unit
101
with multiplexed signals having the AU-4 frame format. The 2M units
104
interface with lower speed services by acting as multiplex/demultiplex facilities which convert C-12 frames to Tributary Unit Group-2 (TUG-2) frames, and vice versa. Here, the term “C-12” denotes a container which accommodates 2.048 Mb/s Plesiochronous Digital Hierarchy (PDH) signals, where the name “2M unit” implies this specific bitrate to be handled. The 2M units
104
provides the cross-connect unit
101
with multiplexed signals having the TUG-2 frame format. The cross-connect unit
101
is a switching element that supports the consolidation, segregation, and grooming of paths running across a plurality of transmission lines. It also functions as a frame format converter that enables TUG-2 multiplexed signals sent from the plurality of 2M units
104
to be reformed into AU-4 multiplexed signals.
FIG. 31
is a block diagram of another type of a transmission apparatus, which employs a cross-connect unit
111
to interconnect high-level group units including two STM-1 units
112
and
113
, and low-order group units including a plurality of 34M units
114
. The STM-1 units
112
and
113
serve as multiplex/demultiplex facilities which convert STM-1 frames to AU-4 frames, and vice versa, thus providing the cross-connect unit
111
with AU-4 multiplexed signals. The 34M units
114
interface with lower speed services by acting as multiplex/demultiplex facilities to convert C-3 frames to TUG-3 frames, and vice versa. Here, the term “C-3” represents a container which accommodates 34.368 Mb/s PDH signals, as the name “34M unit” implies. The 34M units
114
supply the cross-connect unit
111
with TUG-3 multiplexed signals. Besides providing path switching capabilities, the cross-connect unit
111
serves as a frame format converter that allows TUG-3 multiplexed signals sent from the plurality of 34M units
114
to be reformed into AU-4 multiplexed signals.
FIG. 32
illustrates still another example of a transmission apparatus, which has a cross-connect unit
121
to interconnect high-level group units including two STM-4 units
122
and
123
, and low-order group units including a plurality of 140M/STM-1 units
124
. The STM-4 units
122
and
123
are multiplex/demultiplex facilities that convert STM-4 frames to AU-4 frames, and vice versa, thus providing the cross-connect unit
121
with AU-4 multiplexed signals. The 140M/STM-1 units
124
serve as multiplex/demultiplex facilities to convert C-4 or STM-1 frames to AU-4 frames, and vice versa. A C-4 frame is a container which accommodates 138.264 Mb/s PDH signals. The 140M/STM-1 units
114
supply the cross-connect unit
121
with AU-4 multiplexed signals. Note here that the cross-connect unit
121
does not have a function to convert signal formats, since its input and output signals have a unified format, AU-4.
As understood from
FIGS. 30
to
32
, conventional SDH transmission apparatus have different internal configurations depending on the hierarchical levels of multiplexed signals that they should deal with. Particularly, it is a problem that their integral cross-connect units have to be replaced with other ones, in order to introduce a different type of low-order group units into the system. Recall the aforementioned transmission apparatus of
FIG. 30
, for example. The cross-connect unit
101
used in this transmission apparatus is designed to interface with a particular type of low-order group units, i.e., 2M units. For this reason, it is not possible to install 34M units in place of the present 2M units
104
. To do so, the cross-connect unit
101
must be changed to another type, such as a cross-connect unit
111
shown in FIG.
31
. Similarly, since the cross-connect unit
111
shown in
FIG. 31
cannot work with 140M/STM-1 units
124
in
FIG. 32
, one should replace it with another type of cross-connect unit, such as a cross-connect unit
121
shown in
FIG. 32
, in order to use 140M/STM-1 units.
The conventional transmission apparatus have still another problem as will be described below.
FIG. 33
shows a system in which network devices
131
to
133
each consolidate 2.048 Mb/s or 34.368 Mb/s PDH signals into a single STM-1 bitstream and a network device
134
multiplexes four STM-1 bitstreams into a single STM-4 bitstream. Here, the network devices
131
to
133
each correspond to the transmission apparatus of
FIG. 30
or
FIG. 31
, while the network device
134
corresponds to the transmission apparatus of FIG.
32
. These four network devices
131
to
134
are under the control of a management unit
135
which monitors and supervises them through the connection paths indicated by the broken lines. As
FIG. 33
shows, this conventional system is not simple since it requires two processing stages only to convert 2.048 Mb/s or 34.368 Mb/s PDH signals into a single STM-4 bitstream. As such, the increase in the number of network elements will make the management tasks more complex and result in a higher system cost that the customer should pay for.
SUMMARY OF THE INVENTION
Taking the above into consideration, an object of the present invention is to provide an SDH transmission apparatus with a simplified internal configuration, employing a versatile cross-connect unit that can deal with various classes of digital bitstreams regardless of their levels in the multiplexing hierarchy.
To accomplish the above object, according to the present invention, there is provided an SDH transmission apparatus which multiplexes transmission signals according to a multiplexing hierarchy. This apparatus comprises the following elements:
a mounting rack having a plurality of module slots and a backplane providing electrical interconnection among functional modules installed in the plurality of module slots;
a cross-connect unit, installed in dedicated cross-connect unit slots on the mounting rack, which comprises high-order group ports and low-order group ports;
at least one high-order group transmission unit, installed in dedicated high-order group slots on the mounting rack, which sends and receives multiplexed signals at a predetermined level of the multiplexing hierarchy to/from the high-order group ports of the cross-connect unit; and
a plurality of low-order group transmission units, installed in dedicated low-order group slots on the mounting rack, which sends and receives the multiplexed signals at the predetermined level of the multiplexing hierarchy to/from the low-order group ports of the cross-connect unit.
The above and o
Cangialosi Salvatore
Fujitsu Limited
Katten Muchin Zavis & Rosenman
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