Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-03-11
2001-02-13
Vu, Huy D. (Department: 2733)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S467000
Reexamination Certificate
active
06188701
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for interfacing between different networks.
2. Description of the Related Art
Currently there are networks using asynchronous signals (hereinafter called a DSn network) and networks using synchronous (SONET) signals (hereinafter called a SONET network) in the transmission networks of North America, etc. When a DSn network and a SONET network are connected, a SONET optical transmission apparatus is used. Although an apparatus for connecting a network using-a DS3 (44.736 Mbps) signal (hereinafter called a DS3 network) to a network in which signals can be demultiplexed and multiplexed in units of STS1 (51.84 Mbps, a frame format of a SONET network) in the SONET network (hereinafter called a SONET STS1 network), is implemented, an apparatus for connecting a network using the DS3 (44.736 Mbps) signal to a network in which signals can be demultiplexed and multiplexed in units of VT1.5 (1.728 Mbps, a signal provided to easily add/drop-multiplex the payload of an STS signal, given the abbreviation VT of virtual tributary) in the SONET network (hereinafter called a SONET VT network), is not implemented yet.
That is, a conventional apparatus can multiplex and demultiplex DS3 signals received from a DSn network only in units of STS1 units (51.84 Mbps) in the SONET network, but cannot multiplex and demultiplex the DS3 signals in units of VT1.5 units (1.728 Mbps).
The SONET network and the DS3 network are formed independently of each other. Therefore, if a DS3 signal is connected to the SONET network, the conventional apparatus cannot monitor the condition of the DS2 signal in a DS3 signal, nor a DS1 signal in the DS3 network, though the apparatus can monitor the condition of the connecting signal of the DS3 signal.
Recently there has been an increasing demand for an apparatus in which signals can be multiplexed and demultiplexed in units of VT1.5 while operating the DS3 network, and that which can enter a SONET VT network. It is an object of the present invention to provide an apparatus for converting DS3 signals to VT1.5 signals, and constructing a VT1.5 network so that an apparatus supporting the SONET VT network can receive the services of a network using the DS3 (44.736 Mbps) signal.
FIG. 1
shows the configuration in the case where a SONET VT network is connected to a DS3 network by combining a conventional M13 apparatus and a conventional ADM apparatus. First, an STS1 input signal from the SONET VT network is demultiplexed and converted by an ADM
2700
. The STS1 signal transmitted from a SONET network is first demultiplexed and converted to VT signals by an STS1/VT1.5 demultiplexer unit
2702
, and further demultiplexed and converted to DS1 signals by a VT1.5/DS1 demultiplexer unit
2703
. When the VT signals are demultiplexed and converted to the DS1 signals, the signals stored in the memory of the VT1.5/DS1 demultiplexer unit
2703
are output synchronized with a clock generated by a clock generator unit for the DS1 network
2704
. When the DS1 signals demultiplexed and converted in this way are multiplexed and converted to a number of DS2 signals, the DS1 signals are stored once in a memory of an M13 apparatus, read using a DS2 clock, and multiplexed to the DS2 signals. Furthermore, these DS2 signals are synchronized with a clock signal from a clock generator unit for the DS3 network
2707
, are stored once in the memory of a DS2/DS3 multiplexer unit
2706
, are read using a clock for a DS3 network, are multiplexed and converted to a DS3 signal, and sent out to the DS3 network. However, the provision of a memory for 28 channels of DS1 in an apparatus in order to multiplex and convert DS1 signals to DS2 signals leads to large-scale circuitry and an increased consumption of power.
FIG. 2
shows the configuration in the case where a network using a DS3 (44.736 Mbps) signal is connected to a SONET network by using a conventional apparatus. In this case, the DS3 network can be connected only to a SONET STS1 (51.84 Mbps) network, and only the condition of a DS3 signal can be monitored for an asynchronous network, and both DS2 and DS1 signals in the DS3 signal cannot be monitored.
That is, when a conventional ADM
2800
is used, the DS3 signal received from the DS3 network is converted by a DS3/STS1 multiplexer unit
2803
, and the alarm signal of the DS3 signal is detected by a DS3 alarm detector unit
2802
, which is reported to a SONET condition reporting unit
2801
. Since the SONET condition reporting unit
2801
transmits this alarm signal to the SONET network via an intra-apparatus condition monitor unit, the alarm information of the DS3 signal is sent to the SONET network, but the alarm information of both DS2 and DS1 signals cannot be extracted.
FIG. 3
shows the configuration in the case where a DS3 network is connected to a SONET VT network by combining a conventional M13 apparatus and a conventional ADM apparatus. In this case, the condition of DS3, DS2 and DS1 signals can be monitored by the M13 apparatus, but cannot be monitored in a SONET network, since the M13 apparatus and the ADM apparatus are different apparatuses.
That is, since the conventional M13 apparatus
2900
and the conventional ADM apparatus
2906
are configured independently, and both M13 apparatus
2900
and ADM apparatus
2906
are configured to transmit an alarm signal only to a DS3 network and a SONET network, respectively, the alarm information of the SONET network cannot be monitored from the DS3 network. The DS3 signal transmitted from the DS3 network is input to the DS3/DS2 demultiplexer unit
2902
of the M13 apparatus
2900
, an alarm is detected by a DS3 alarm detector unit
2903
, and the result of alarm detection is transmitted to the DSn condition reporting unit
2901
. The DS2 signals output from the DS3/DS2 demultiplexer unit
2902
are input to a DS2/DS1 demultiplexer unit
2904
, the signals are converted to DS1 signals, an alarm is detected by a DS2 alarm detector unit
2905
, and the result of alarm detection is transmitted to a DSn condition reporting unit
2901
. The DSn condition reporting unit
2901
is configured to transmit the result of the alarm detection to the DS3 network, and the detection result of the DS3 and DS2 alarms obtained in the M13 apparatus is not transmitted to the SONET network. To the conventional ADM apparatus
2906
are sent the DS1 signals demultiplexed and converted by the M13 apparatus
2900
. In the ADM apparatus
2906
the DS1 signals are converted to VT1.5 signals by a DS1/VT1.5 multiplexer unit
2907
, and a DS1 alarm detector unit
2908
detects the alarm of a DS1 signal and transmits the alarm to a SONET condition reporting unit
2910
. The SONET condition reporting unit
2910
transmits the result of this alarm detection to the SONET network. On the other hand, the VT1.5 signals converted by the DS1/VT1.5 multiplexer unit
2907
are transmitted to a VT1.5/STS1 multiplexer unit
2909
, and are converted to an STS1 signal, which is sent to the SONET network.
That is, the SONET network and the DSn network are formed independently of each other, and when a DSn network is connected to a SONET network using a conventional unit, only the information of the DSn signal at the contact point connected to the SONET network can be monitored.
Currently when a DS3 signal is connected to a SONET VT network, there is a demand for the condition monitoring and management of the DS2 and DS1 signals in the DS3 signal, even in the SONET VT network.
In one aspect of the present invention, the method for connecting to the SONET VT network by converting the DS3 (44,736 Mbps) signal to the DS1 (1,544 Mbps) signal once in the apparatus is utilized as means for connecting the DSn network to a SONET network. However, when converting the DS3 signal to the DS1 signal, the method described below is usually utilized in the conventional method.
FIG. 4
shows the configuration of the system. The system comprises a DS3/DS2 demultiplexer unit
3000
, a DS2/DS1 demultiplexer unit
3001
Oka Akihiko
Tsukamoto Keiichiro
Boakye Alexander
Fujitsu Limited
Helfgott & Karas P.C.
Vu Huy D.
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