Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1998-09-25
2004-03-30
Olms, Douglas (Department: 2732)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S503000
Reexamination Certificate
active
06714531
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of avoiding an error of a pointer process in an SDH (synchronous digital hierarchy) transfer system and to a SDH radio communication device.
In recent years, a number of SDH networks have been implemented based on optical fibers, and, also, use of SDH systems has been on increase in digital multiplex radio systems. Against this background, it is vital to provide for SDH radio devices in implementing an SDH network where these SDH radio devices are equipped with stable high-quality data-transfer functions complying with the SDH interface. Also, a configuration that insures no malfunction is expected.
2. Description of the Related Art
FIG. 1
is an illustrative drawing showing a configuration of radio devices complying with the SDH interface. The configuration includes a carrier device
16
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1
of an SDH transfer system, radio devices
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2
and
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3
complying with the SDH interface, and a carrier device
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4
of another SDH transfer system.
The carrier devices
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1
and
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4
are connected to the radio devices
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2
and
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3
, respectively, via optical cables conveying optical signals or coaxial cables or the like for conveying electrical signals. The radio devices
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2
and
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3
are connected to each other by means of a radio communication line. In this radio communication line, a radio frame complementary overhead (RFCOH) is attached when transfer is engaged.
FIG. 2
is an illustrative drawing for explaining a main portion of the radio device complying with the SDH interface.
FIG. 2
is used for explaining a main portion of the radio device
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2
or
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3
.
The radio device in
FIG. 2
includes a carrier-side SDH-physical-interface (SPI) unit
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1
, a carrier-side regenerator-section-overhead (RSOH) processing unit
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2
, a carrier-side multiplex-section-overhead (MSOH) processing unit
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3
, a carrier-side administrative-unit-pointer (AU pointer) processing unit
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4
, a radio-side administrative-unit-pointer (AU pointer) processing unit
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5
, a radio-side multiplex-section-overhead (MSOH) processing unit
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6
, a radio-side regenerator-section-overhead (RSOH) processing unit
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7
, a modem
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8
, and a radio-transmission/reception unit (TX/RX)
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9
. A carrier-side processing unit is designated as
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10
, and a radio-side processing unit is denoted as
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11
. Here, an antenna for radio transmission/reception is not shown-in the figure.
The carrier-side SDH-physical-interface unit
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1
is an interface for exchanging optical/electrical signals with the carrier device
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1
or
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4
. The carrier-side regenerator-section-overhead processing unit
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2
, the carrier-side multiplex-section-overhead processing unit
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3
, and the carrier-side administrative-unit-pointer processing unit
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4
are used for exchanging data with the carrier device of the SDH transfer system by using a STM-1 frame format, for example.
The SDH transfer system transfers digital signals by use of a standard STM (synchronous transfer mode) frame format. In this case, the STM-1 frame format (155 Mbps), for example, includes a section overhead (SOH) having 9 rows each comprised of 9 bites and a payload having 9 rows each comprised of 261 bytes.
FIG. 3
is an illustrative drawing showing a STM-1 frame format. A section overhead (SOH)
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1
includes frame-synchronization bytes A
1
and A
2
, an STM-frame-identification byte J
0
, error monitoring bytes B
1
and B
2
, maintenance-personnel-voice-talk bytes E
1
and E
2
, a user-channel byte F
1
, data-communication-channel bytes D
1
through D
12
, pointer bytes H
1
and H
2
, stuff-operation bytes H
3
, a switch-control byte K
1
, a section-warning-display byte K
2
, a synchronization-clock-quality byte S
1
, and a error-notification byte M
1
. A regenerator-section overhead is denoted as RSOH, and a multiplex-section overhead is denoted as MSOH. Further, a portion which stores bytes H
1
, H
2
, and H
3
is referred to as an AU-pointer portion.
FIGS. 4A and 4B
are illustrative drawings for explaining the pointer bytes H
1
and H
2
, respectively. The pointer bytes H
1
and H
2
include 4 bits of new-data flags (NDF) N, SS bits, and a 10-bit pointer comprised of bits I and D.
The 4-bit new-data flags N are used for transferring an NDFEN signal (e.g., 1001) indicative of a change in a pointer value or an NORNDF signal (e.g., 0110) indicative of no change in the pointer value.
The 2-bit SS bits are used for detecting an invalid pointer. In detail, a set value or a fixed value is sent from a transmitter side, and a receiver side compares received SS bits with the set value or the fixed value in order to detect an invalid pointer.
The 10-bit pointer containing a pointer value is comprised of 5 bits of bit I and 5 bits of bit D arranged in turn at every other position, and is used for indicating a start position of multiplexed data in the payload as well as for controlling stuff operations.
The payload
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2
comprised of 9 rows of 261 bytes stores data starting from a selected one of positions provided at 3-byte intervals. A position of the first data (J1 bytes) in the payload is represented by the 10-bit pointer indicative of one of 0 through 782.
The 10-bit pointer included in the pointer bytes H
1
and H
2
indicates the position of the first data in the payload, and, also, is used for controlling stuff operations. The stuff operations include a positive stuff operation inserting 3-byte stuff bytes into the payload and a negative stuff operation relocating 3-byte data from the payload to the stuff-operation bytes H
3
#1 through H
3
#3 in the AU-pointer portion.
The 5 bits I in the 10-bit pointer are used when the positive stuff operation is performed. In the case of the positive stuff operation, the transmitter side obtains an inverse of each of 5 bits I of a preceding frame, and sends each of the obtained inverses as a bit I. By doing so, the transmitter side indicates an increment by 3 bytes of the position of the first data in the payload, and inserts 3 stuff bytes into the payload before transmitting an STM-1 frame signal.
The 5 bits D in the 10-bit pointer are used when the negative stuff operation is performed. In the case of the negative stuff operation, the transmitter side obtains an inverse of each of 5 bits D of a preceding frame, and sends each of the obtained inverses as a bit D. By doing so, the transmitter side indicates a decrement by 3 bytes of the position of the first data in the payload, and relocates 3-byte data from the payload to the stuff-operation bytes H
3
#1 through H
3
#3 in the AU-pointer unit before transmitting an STM-1 frame signal.
The receiver side checks the pointer bytes H
1
and H
2
, and accept them as a correct pointer indicative of the position of the first data in the payload if the pointer value represented by the 10 bits is identical in more than two consecutive frames. Because of this, even when bits I and bits D of the 10-bit pointer are used for the stuff operations, the pointer value can never be misidentified as indicating a wrong position of the first data in the payload.
Further, if no less than 3 bits I out of the total of 5 bits I are an inverse of respective bits I of the preceding frame and if no more than 2 bits D out of the total of 5 bits D are an inverse of respective bits D of the preceding frame, a determination is made that a positive stuff operation has been conducted. In this case, processing of the received payload data is carried out such that the stuff bytes inserted on the transmitter side are not read on the receiver side.
Further, if no less than 3 bits D out of the total of 5 bits D are an inverse of respective bits D of the preceding frame and if no more than 2 bits I out of the total of 5 bits I are an inverse of respective bits I of the preceding frame, a determination is made that a negative stuff operation has been conducted. In this case, the receiver side reads data from the stuff-oper
Abe Satoru
Oide Kenichi
Fujitsu Limited
Katten Muchin Zavis & Rosenman
Olms Douglas
Phunkulh Bob A.
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