Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-07-20
2002-12-17
Jung, Min (Department: 2731)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S528000
Reexamination Certificate
active
06496518
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an SDH (Synchronous Digital Hierarchy) transmission system, and a frame transmission method in an SDH transmission system and an SDH transmission unit, and more particularly to a transmission method suitable for use in a SONET in accordance with an SDH transmission mode.
(2) Description of the Related Art
(A) Description of Transmission Frame Handled in SONET (SDH) Transmission Mode
FIG. 9
is a diagram showing a format of a basic transmission frame handled in a SONET (Synchronous Optical Network). As shown in
FIG. 9
, the basic transmission frame for the SONET has 9×3 bytes of overhead
10
containing various operation and maintenance (supervisory control) information such as frame synchronization signal, or parity check signal, and 9×87 bytes of payload
20
containing actually transmitted data, resulting in information of 9×90 bytes in total. In the SONET, the 90×9 bytes (=810 bytes) of frame is transmitted 8000 times per second, thereby generating a signal [referred to as STS-1 (Synchronous Transport Signal Level 1) , or STM-0 (Synchronous Transfer Module Level 0) in the SDH] having a transmission rate of 51.84M (=90×9×8×8000) b/s. As used herein, “SONET” means a network currently used in North America in accordance with an SDH transmission mode.
Further, as is well known, the overhead
10
is provided with a section overhead [(R-) SOH]
11
which, in communication between a line terminal multiplex relay transmission unit (LTE) and a regenerator unit (REG), or between the regenerator units (REG) (referred to as “section” in the SONET, or “regenerator (R-) section” in the SDH: see reference numeral
11
A in
FIG. 13
) , is terminated and replaced at the LTE and the REG, and a line overhead [LOH (M-SOH)]
12
which, in communication between the LTE (referred to as “line” in the SONET, or “multiplex (M-)section” in the SDH: see reference numeral
12
A in FIG.
13
), is terminated and replaced at the pieces of LTE.
Additionally, the overhead
10
is provided with the various operation and maintenance information. For example, as shown in
FIG. 10
, in the SOH
11
are defined A
1
, A
2
bytes used to establish frame synchronization, a digital error supervising [BIP (Bit Interleaved Parity] byte B
1
used on the section
11
A, and data communication channel (DCC) bytes D
1
to D
3
(data link of 192 k b/s) for communication for a supervisory control in the section
11
A. In the LOH
12
are defined a BIP byte B
2
over a line
12
A, APS (Automatic Protection Switch) bytes K
1
, K
2
, and DCC bytes D
4
to D
12
(data link of 576 k b/s) over the line
12
A.
Moreover, in
FIGS. 9 and 10
, pointer bytes (AU [administrative unit] pointer)
13
shows, by using an address, a difference between a phase of a transmission frame and a frame phase of an administrative data unit (VT: Virtual Tributary Unit) contained in the payload
20
. The pointer bytes
13
can rapidly establish frame synchronization of the VT.
Further, in the SONET, the basic transmission frame (STS-1) having the above-mentioned format is processed through byte multiplexing by n frames (where n=3, 12, 48, 192, and so forth), thereby forming an STS-n frame as shown in FIG.
11
. It is possible to generate a high-speed signal with, for example, an STS-3 (of 155.52M b/s=51.84M b/s×3) if the STS-1 frame is processed through the byte multiplexing by 3 frames, an STS-12 (of 622.08 M b/s) if processed through the byte multiplexing by 12 frames, anSTS-48 (of 2.488 G b/s) if processed through the byte multiplexing by 48 frames, and an STS-192 (of 9.953 G b/s) if processed through the byte multiplexing by 192 frames. Moreover, in the SDH, STM-N (N=n/3) respectively correspond to signals having the same transmission rates as those of the above STS-n.
Here, in the case of the STS-192, as shown in
FIG. 12
, the frame includes 9×576 (3×192) bytes of overhead
10
and 9×16704 (87×192) bytes of payload
20
. However, all the bytes of the overhead
10
are not used. As shown in
FIG. 12
, only one byte is used for each area for operation and maintenance information (such as B
1
, E
1
, and F
1
) except special signals (such as A
1
, A
2
bytes, and BIP byte B
2
). Hence, under the present circumstances, almost the entire area of the overhead
10
is left free.
(B) Description of SONET
FIG. 14
is a block diagram showing an illustrative SONET (transmission system). In the SONET
100
shown in
FIG. 14
, a 10 G ring network
200
for handling a transmission frame (STS-192) of about 10 G b/s, 2.4 G ring networks
300
,
400
for handling a transmission frame (STS-48) of about 2.4 G b/s, and a 622 M ring network
500
for handling a transmission frame (STS-12) of about 622 M b/s are interconnected through transmission units serving as gateways which will respectively be described infra.
Further, as shown in
FIG. 14
, for example, in the 10 G ring network
200
(hereinafter briefly referred to as 10 G ring
200
), a plurality of 10 G b/s line terminal multiplex relay transmission units (LTE)
110
-
1
to
110
-
4
and a plurality of 10 G b/s regenerator units (REG)
111
are connected in a ring manner. Similarly, in the 2.4 G ring networks
300
,
400
(hereinafter briefly referred to as 2.4 G rings
300
,
400
), 2.4 G b/s LTE
120
-
1
to
120
-
4
, and
130
-
1
to
130
-
4
are connected in the ring manner. In the 622M ring network
500
(hereinafter briefly referred to as 622M ring
500
), 622M b/s LTE
140
-
1
to
140
-
4
are connected in the ring manner.
Moreover, in the 10 G ring network
200
, according to a maximum transmittable distance of the line terminal multiplex relay transmission unit
110
-
i
(where i=1 to 4), a proper number of regenerator units (REG)
111
are mounted between the line terminal multiplex relay transmission units
110
-
i
to form the section
11
A. It is to be noted that the regenerator unit
111
may be mounted in the 2.4 G rings
300
,
400
, or in the 622M ring
500
.
Here, the transmission units (LTE)
110
-
i,
120
-
i,
130
-
i,
and
140
-
i,
and the transmission units
111
[hereinafter referred to as “transmission unit
100
A” or “node unit
100
A” unless the transmission units
110
-
i,
120
-
i,
130
-
i,
140
-
i,
and
111
(LTE, REG) are individually shown] forming the rings
200
to
500
respectively have the function of performing replacement (termination/insertion) processing of the overhead
10
of the received transmission frame STS-n (STM-N). With attention to the function, as shown in
FIG. 15
, the transmission unit includes interface portions
171
to
173
according to a transmission frame to be handled (a speed of an accommodated line), a HUB circuit portion
174
, a HED circuit portion
175
, optical fibers
176
, a CPU circuit portion
177
, and so forth.
Further, each of the above interface portions
171
to
173
terminates a corresponding optical signal frame among, for example, an OC-192 (Optical Carrier-level 192) serving as an optical signal frame of the STS-192, an OC-48 serving as an optical signal frame of the STS-48, and an OC-12 serving as an optical signal frame of the STS-12, and extracts OH information in the overhead
10
to output the OH information to the HUB circuit portion
174
, while inserting (storing) the OH information output from the HUB circuit portion
174
in the overhead
10
at a predetermined position.
However, the overhead
10
serving as a candidate for the termination/insertion processing varies depending upon whether it is processed in the interface portions
171
to
173
in the LTE
110
-
i,
120
-
i,
130
-
i,
and
140
-
i,
or in those in the REG
111
. That is, both the SOH
11
and the LOH
12
are terminated in each of the LTE
110
-
i,
120
-
i,
130
-
i,
and
140
-
i,
and only the SOH
11
is terminated in each of the REG
111
.
Moreover, all the interface portions
Fujitsu Limited
Jung Min
Katten Muchin Zavis & Rosenman
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