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Description  |
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BACKGROUND OF THE INVENTION
The invention relates to data communications and in particular to a system
for the detection and correction of faults in a data communications
network from a central location.
In my copending, commonly assigned patent application, System For The
Quantitative Measurement Of Impairments In The Communication Channel Of A
Quadrature Amplitude Modulation Data Communication System, Ser. No.
16,912, filed Mar. 2, 1979 there is disclosed a technique for QAM eye
pattern analysis which permits the quantitative evaluation of a
communications channel or media interconnecting two remote communication
equipments of a data communication network. The communications equipment,
in the form of transmit and/or receive modems may be interconnected by a
communication channel comprising dedicated or dialed up commercial,
military or foreign voice-grade telephone lines and include PCM, carrier,
satellite and cable links.
In my copending, commonly assigned patent application, In-Service
Monitoring System For Data Communications Network, Ser. No. 17,042, filed
Mar. 2, 1979 there is disclosed a technique for the non-interfering
monitoring of the components of a data communications network including
the detection and isolation of faults and potential failures within the
network.
The techniques disclosed in the above mentioned patent applications solve
many long felt needs since they permit the evaluation of the communication
of data from location to location without interfering with such data
communication. The systems also permit potential future problems to be
located and corrected prior to a degradation of the communications system
to a point where it interferes with data transmission.
While these copending cases solve many of the problems heretofore
encountered they still require that at each location of a data
communications network a monitoring function be performed. For
multi-location networks this would be both costly and time consuming.
In view of the above, it is the principal object of the present invention
to provide a system whereby the monitoring of the condition of components
of a multi-location data communications network may be attained from a
central location.
A further object is to provide such a system wherein adjustment or
reconfiguration of the components of the network at the several remote
sites may be attained from the central location.
Still further objects and advantages will be apparent from a review of the
detailed description of a preferred embodiment of my invention.
SUMMARY OF THE INVENTION
The above and other beneficial objects and advantages are attained in
accordance with the present invention by providing a data communications
network consisting of data terminal equipment provided at at least two
locations remote from each other. At each location, transmit and/or
receive communications equipment is connected to the data terminal
equipment and interconnected through a suitable communications channel,
media or links. Auxiliary signal processors are provided at each location
interfaced with the communications equipment and adapted to derive, on a
non-interfering basis, information from the communications equipment
relative to the status of the data terminal equipment, communications
equipment, and communications channel.
An auxiliary communications equipment is also provided at each location
interfaced with the auxiliary signal processor thereat. A central
controller is provided at a central location which could, if desired, be
the location of one of the data terminal equipments. The auxiliary
communications equipments are each interconnected, through a
communications link, with the central controller thereby providing a
telemetry interface between the central controller and the auxiliary
signal processors.
The auxiliary communications equipment may be comprised for example, of a
low speed FSK modem which transfers data in a portion of the
communications media bandwidth which is not utilized for normal data
traffic. In a system which utilizes 2400 bps modems for the communications
equipment which operate within a frequency range of 1000 Hz to 2,600 Hz
for data traffic, the auxiliary communications equipment may operate at a
rate of 110 bps within a frequency range of 340 Hz to 540 Hz.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a schematic block diagram of the system in accordance with the
present invention;
FIG. 2 is a schematic block diagram of the auxiliary communications
equipment utilized in the system of the present invention; and
FIG. 3 is a waveform diagram depicting the separation of data and telemetry
information.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference is now made to the drawings and to FIG. 1 in particular wherein a
data communications system 10 in accordance with the present invention is
depicted. The system comprises at least two data terminal equipments 12
and 14 provided at locations remote from each other. At each location
there is also located communications equipment 16 (or 18). The
communications equipment are in the form of transmit/receive modems and
pass customer data to each other over a suitable communications media or
channel such as a telephone link.
In the preferred embodiment, the modems 16 and 18 employ PSK modulation
transferring data at a rate of 2400 bps. The modems 16 and 18 are
connected to their associated data terminal equipment 12 and 14 by means
of an RS232-C interface in a manner described in more detail in the
previously mentioned application Ser. No. 17,042, filed Mar. 2, 1979 for
In-Service Monitoring System For Data Communications Network.
At each location there is also provided an auxiliary processing element 20
(or 22). Preferably the auxiliary processing element is contained in the
same chassis as the communications element 16 (or 18). The details of the
interface between the auxiliary processing element 20 (or 22) and
communications element 16 (or 18) are also set forth in the previously
mentioned copending applications.
In accordance with the present invention, there is also provided an
auxiliary communications element at each location. Accordingly, a
telemetry channel subsystem 24 is provided at the location of modem 16,
and preferably within the same chassis and similarly a telemetry channel
subsystem 26 is provided at the location of modem 18, preferably within
its chassis.
The inputs and outputs of the auxiliary processing elements 20 and 22 are
provided from and to the telemetry channel subsystems 24 and 26
respectively which comprise FSK modems which operate at a data rate of 110
bps.
Commands to the telemetry channel subsystems and information from them are
provided to a central controller 28. The central controller 28 may be
provided at the location of one of the data terminals or at a different
location. The central controller comprises a mini-computer such as, for
example, the model TI 990/10 available from the Texas Instruments Corp.
Reference is now made to FIG. 2 wherein the telemetry channel subsystem is
depicted.
As shown, data or commands from the central controller pass to a local
auxiliary processing equipment 20 along line 30. The data from the central
controller is also supplied to a local FSK transmitter 32. The output of
FSK transmitter 32 is fed to an adder 34 along with the output of a PSK
transmitter and supplied to the telephone line. At the remote end, a high
pass filter 36 is provided to remove the low frequency FSK and pass the
resultant PSK signal to the PSK receiver along line 38. A low pass filter
40 is also provided to remove the PSK from the composite signal and to
supply the remaining FSK signal to the FSK receiver 42. The FSK receiver
output is fed to the remote auxiliary processing element 22.
Data from auxiliary processing element 22 is provided to the FSK
transmitter 44 within its co-located auxiliary communications element 26.
The data signal is summed, through adder 46 with the PSK transmitter
output of modem 18. The composite output at the remote site is connected
to a telephone channel and thereby to the local site (i.e., the location
of communications equipment 16). High and low pass filters 48 and 50
separate the composite PSK and FSK signals at the local site and feed them
respectively to the PSK input and FSK receiver 52. The FSK receiver data
output is combined by means of OR gate 54 with the output of local
auxiliary processing equipment 20 and fed to the central controller.
As will be noted from the following detailed description of the
relationship between the auxiliary communications equipments and central
controller, a key feature of the central controller is that it continually
addresses and queries each auxiliary processing equipment in the network
as to the status of that auxiliary processing equipment, the corresponding
communications equipment, the corresponding data terminal and the status
of the communications media with regard to channel impairments. If the
equipments at the site queried are not in a normal state, an alarm
response is returned to the central controller from the queried auxiliary
processing equipment. The alarm response also includes both the address or
identification of the auxiliary processing equipment generating the alarm
as well as the class of parameter which is not within normal limits and
generated the alarm.
FIG. 3 presents the output spectra of the PSK transmitter and FSK
transmitter. The PSK energy is in a frequency band of 1,000 to 2,600 Hz
and the FSK energy is in a frequency band of 340 to 540 Hz. Hence, both
these signals may be simultaneously transmitted on a telephone channel
without mutual interference. Also shown in FIG. 3 are the characteristics
of high pass and low pass signal separating filters.
The command or interrogation signalling formats used by the central
controller 28 is one of two types. Type 1 interrogations are used when the
central controller automatically polls each auxiliary processing element
20 and 22 as to whether or not the auxiliary processing element has
determined that any parameters relating to its data terminal equipment,
communication media, communications equipment or the auxiliary processing
equipment itself are at alarm level. The poll format expressed in bits is
000A.sub.1 A.sub.2 A.sub.3 A.sub.4 A.sub.5 P1. The first bit is set to 0
to indicate a start bit of the character. The next two bits are set to 0
also. Next five address bits A.sub.1 through A.sub.5 occur. A parity check
of the preceding seven bits follows and finally a 1 is included to
indicate the end of the character. A second word composed of
0A.sub.6 A.sub.7 A.sub.8 A.sub.9 FFFP1
follows. The first bit is again a 0 to indicate start of character. Next
four more address bits follow. Three format indicator bits, indicated by
FFF follow. Finally, a parity bit and a 1 to indicate end of character are
included.
If the format indicator bits are 000, the message is an auto scan query and
the total message length is two characters.
If the format indicator bits are 001, the query contains a third character.
This third character contains a specific command. The bit pattern for the
command character is
0C.sub.1 C.sub.2 C.sub.3 C.sub.4 C.sub.5 C.sub.6 C.sub.7 P1
where the C.sub.k s are employed to indicate the specific command type.
The response of the auxiliary processing equipment to an autoscan poll may
be one of two types. If no parameters have reached an alarm limit level,
the auxiliary processing equipment echoes back the query. If an alarm has
occurred, the auxiliary processing equipment echoes the query plus two
additional characters which indicate the cause(s) of the alarm(s). The 14
data bits contained in the two characters contain the following
information:
______________________________________
B1 DTE interface Alarm
B2 Phase Jitter Alarm
B3 Signal to Noise Ratio Alarm
B4 Signal Quality Alarm
B5 Received Signal Level Alarm
B6 Power Supply Voltage Alarm
B7 Spare
B1 Standby CE Alarm
B2 CE in Test Mode
B3 Message Front Panel Switch ON
B4 Spare
B5 External Input ON
B6 Spare
B7 Spare
______________________________________
The response to the status query is a 32 character message which is
composed of the following characters:
______________________________________
CH.sub.1 -CH.sub.2
Address
CH.sub.3 -CH.sub.6
Status as detailed below
CH.sub.7 Phase Jitter Value
CH.sub.8 Spare
CH.sub.9 -CH.sub.10
Sum of c.sup.2
CH.sub.11 -CH.sub.12
Sum of d.sup.2
CH.sub.13 CE Power Supply Voltage Value
CH.sub.14 Receiceived Signal Level Value
CH.sub.15 -CH.sub.16
LSD Alarm Timer Limit Value
CH.sub.17 -CH.sub.18
RTS Alarm Timer Limit Value
CH.sub.19 -CH.sub.20
CTS Alarm Timer Limit Value
CH.sub.21 RLS Alarm Limit Value
CH.sub.22 Phase Jitter Alarm Limit Value
CH.sub.23 -CH.sub.24
SNR Alarm Limit Value
CH.sub.25 Status as detailed below
CH.sub.26 Frequenty Offset Value
CH.sub.27 Release Number of ROMS in APE
CH.sub.28 -CH.sub.32
Spare
______________________________________
The 35 status bits in characters three, four, five, six and 25 are defined
as follows:
______________________________________
B1 Transmit Data Activity -
normal or alarm
B2 Receive Data Out - normal or alarm
B3 Transmit Clock Out -
normal or alarm
B4 Receive Clock - normal or alarm
B5 Signal Quality - good or bad
B6 CE Muted - yes or no
B7 CE in Test Mode - yes or no
B8 ROM Release Number in Character 27 -
yes or no
B9 CE 5v Supply Voltage - normal
or alarm
B10 Standby CE 5v Supply Voltage -
normal or alarm
B11 Analog Loopback - enabled or
disabled
B12 Digital Loopback - enabled or
disabled
B13 APE Self-test - passed or failed
B14 CE Self-Test - passed or failed
B15 DTE CTS - normal or alarm
B16 DTE RTS - normal or alarm
B17 Line Signal Detect - normal or alarm
B18 CE Local Test Mode - yes or no
B19-B20 CE Type
01 is 4800
10 is 2400
11 is 9600
B21 Standby CE Available - yes or no
B22 Data Set Ready - on or off
B23 Data Terminal Ready - on or off
B24 CE Stream Disabled - yes or no
B25 CE Rate - high or low
B26 Dial Line Connected - yes or no
B27 Auto Answer - enabled or disabled
B28 CE is - remote or master
B29 CE in Control is - main or standby
B30 Standby CE Self-Test - pass or fail
B31 Customer Data Lines - leased or
dialed
B32 Telemetry Data Lines - leased or
Dialed
B33 Standby CE - present or absent
B34 Dial Backup Equipment - present or
not present
B35 Dial Under APE Control - yes or no
______________________________________
From a study of the two responses which have been discussed in detail, it
is obvious that the central controller 28 may assess the condition of all
communication equipment, auxiliary processing equipment, and the
parameters which relate to the condition of the communication media in
both directions. Additionally, as discussed in the previously mentioned
copending applications, the information is obtained without interruption
of normal customer data traffic. Numerous other commands may also be
employed to provide reconfiguration functions such as:
______________________________________
1. Switch in standby CE
2. Change data rate of CE
3. Cause CE to answer dialed call
4. Cause CE to perform bit error rate
test
5. Cause CE to perform detailed out-of-
service self test
6. Turn off CE
______________________________________
Hence, an operator at the central controller location may assess the
performance of the total communication network and all elements of the
network. Moreover, he may reconfigure the network or its elements to
compensate for or offset degradations within the network.
Thus, in accordance with the above, the aforementioned objectives are
effectively attained.
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