Multiplex communications – Fault recovery – Bypass an inoperative channel
Reexamination Certificate
1998-10-02
2001-07-17
Ngo, Ricky (Department: 2731)
Multiplex communications
Fault recovery
Bypass an inoperative channel
Reexamination Certificate
active
06262973
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a digital multiplexed wireless apparatus (SDH wireless transmission apparatus) using microwaves in an SDH (Synchronous Digital Hierarchy) network. More particularly, the invention relates to an SDH wireless apparatus, which has a plurality of working lines and at least one standby line, for sending and receiving wireless signals in which STM (Synchronous Transfer Mode) signals are used as baseband signals.
An SDH wireless transmission apparatus tends to have a large amount of hardware owing to the size of its transmission capacity. There is increasing need to reduce the size and cost of such apparatus.
In addition, demand for integrated supervision of wireless transmission apparatus and equipment such as optical transmitters and switches has grown in recent years. In SDH communication networks, supervisory control systems are being standardized in accordance with ITU-T and other recommendations, and the need for integrated supervision that is not media-dependent is growing year by year.
In SDH network management, moreover, there is a need for consolidated management of communication devices supplied by a plurality of vendors. However, SDH networks employ additional signals referred to as SOH (Section Overhead) and, though methods of using SOH are being decided by ITU-T, etc., whether or not SOH is used and methods of using SOH differ subtly from one manufacturer to another. As a consequence, an expedient sometimes adopted is to change the way overhead is used as by setting the method of use, thereby making it possible to deal with equipment manufactured by multiple vendors. However, the setting of the equipment and the method of use become more complicated and cost rises. The present invention concerns an SDH wireless transmission apparatus that addresses these difficulties.
The application of SDH techniques in networks is progressing especially in the field of optical transmission. There are cases in which such an SDH communications network incorporates wireless transmission channels. For example, in a case where an SDH communications network is constructed across the ocean or across steep mountainous areas, an optical cable must be laid on the ocean floor or across mountainous terrain. However, the work for laying such cables is a major undertaking and requires great expenditures. When an SDH communications network is constructed in areas where the laying of cable is difficult, as in the case of the ocean floor or steep mountain ranges, an optical transmission line is laid as far as the entrance to the area, an optical transmission line is laid from the exit of the area and a wireless transmission path (channel) is introduced between these two optical transmission lines.
FIG. 19
illustrates an example of the arrangement of an SDH network in which a wireless transmission path is introduced into an optical transmission line. Transmission is performed upon terminating the redundant lines of the optical transmission path. The network includes optical transmission units
1
a,
1
b
and wireless units
2
a
,
2
b
. Optical transmission lines
3
1W
~
3
2P
are laid between the optical transmission unit
1
a
and the wireless unit
2
a
. The optical transmission lines
3
1W
,
3
2W
are working channels, and the optical transmission lines
3
1P
,
3
2P
are protection (i.e., standby) channels. The protection channels
3
1P
,
3
2P
become working channels when failures develop in the working channels
3
1W
,
3
2W
, respectively. Identical data is transmitted on the working channels and protection channels.
Numerals
4
1W
,
4
2W
denote wireless working channels provided to correspond to the optical working channels
3
1W
,
3
2W
, respectively. Numeral
4
P
represents one wireless protection channel. The wireless unit
2
a
terminates the optical protection channels and transmits data from the optical working channels
3
1W
,
3
2W
to the opposing wireless unit
2
b
via the wireless working channels
4
1W
,
4
2W
. Further, when a failure has developed in one of the wireless working channels
4
1W
,
4
2W
, the wireless unit
2
a
transmits data, which has been accepted from the corresponding optical working channel, to the wireless unit
2
b
via the wireless protection channel
4
P
, thereby relieving the failed wireless working channel.
Optical transmission lines
5
1W
~
5
2P
are laid between the wireless unit
2
b
and the optical transmission unit
1
b
. The optical transmission lines
5
1W
,
5
2W
are working channels, and the optical transmission lines
5
1P
,
5
2P
are protection channels. The protection channels
5
1P
,
5
2P
become the working channels when failures develop in the working channels
5
1W
,
5
2W
, respectively. The wireless unit
2
b
sends the optical working channel
5
1W
and the optical protection channel
5
1P
data accepted from the first wireless working channel
4
1W
or wireless protection channel
4
P
(at the time of failure), and sends the optical working channel
5
2W
and the optical protection channel
5
2P
data accepted from the second wireless working channel
4
2W
or wireless protection channel
4
P
(at the time of failure). As a result, identical data is transmitted to the optical working channels and optical protection channels.
In
FIG. 19
, an optical working channel and an optical protection channel form a pair, and two of such pairs are provided. However, N (≧2) pairs are provided ordinarily. More specifically, the optical channels consist of N pairs of optical working channels and optical protection channels. The wireless channels have wireless working channels corresponding to the N-number of optical working channels as well as one wireless protection channel.
FIG. 20
is a diagram for describing the structure of a frame in SDH. This is for a transmission rate of 155.52 Mbps. One frame is composed of 9×270 bytes. The first 9×9 bytes constitute section overhead (SOH), and the remaining bytes constitute path overhead (POH) and payload (PL).
Section overhead SOH transmits information (a frame synchronizing signal) representing the beginning of the frame, information specific to the transmission line (namely information which checks for error at transmission time, information for network maintenance, etc.) and a pointer indicating the position of the path overhead POH. Path overhead POH transmits end-to-end supervisory information within a network. The payload PL is a section which transmits 150-Mbps information.
The section overhead SOH is composed of regenerator section overhead of 3×9 bytes, a pointer of 1×9 bytes and multiplex section overhead of 5×9 bytes. As shown in
FIG. 21
, the multiplex section is the section between terminal repeater units
11
,
12
. In a case where a number of transmission lines
13
a
~
13
c
and repeaters
14
a
,
14
c
are provided between the terminal repeater units
11
,
12
, the regenerator section is the section between both ends of one transmission line, and the multiplex section is composed of a plurality of regenerator sections.
As shown in
FIG. 22
, the regenerator section overhead has bytes A
1
~A
2
, C
1
, B
1
, E
1
, F
1
, D
1
~D
3
, and the multiplex section overhead has bytes B
2
, K
1
~K
2
, D
4
~D
12
, S
1
, Z
1
~Z
2
. The meaning of each byte is illustrated in FIG.
23
. The regenerator section overhead and multiplex section overhead have a number of undefined bytes. Use of these bytes is left to the communications manufacturer concerned.
The K
1
byte among the overhead bytes is used mainly to request switching and designates the level of the switch request and the switched line. The K
2
byte is used mainly to respond to the K
1
byte and indicates whether the system is 1:1 or 1:N (number of working channels with respect to one protection channel), the type of changeover mode, content of a failure, etc. There are two types of switching modes, namely a unidirectional mode, in which only a signal in one direction is changed over, and a bidirectional mode, in which signals in both direct
Ayukawa Ichiro
Hazama Hisamichi
Mizuno Shingo
Sakama Tadayuki
Shiraishi Yuji
Fujitsu Limited
Helfgott & Karas P.C.
Ngo Ricky
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