Method of and apparatus for checking datapath failure in a communication muldem

• US 4,601,028 A
• Filed: 06/18/1984
• Issued: 07/15/1986
• Est. Priority Date: 06/18/1984
• Status: Expired due to Term

• Current Assignee: Alcatel Network Systems India Limited (Nokia Corporation)
• Original Assignee: Rockwell International Corporation
• Inventors: Pepmiller, Paul E., Huffman, Charles E.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Chin, Wellington
• Application Number:
  US06/621,397
• Time in Patent Office: 757 Days
• Field of Search: 370/13, 370/14, 370/15, 370/84, 371/24, 371/25
• US Class Current: 370/217
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085

Abstract

Actual customer data is routed through a composite muldem which comprises a high speed section and a plurality of low speed sections with the signals being switched or transferred between the high speed and low speed sections all at a common frequency. This same customer data is then tested by a bit by bit comparison circuit which tests the data after it is split, rerouted in various datapath configurations and compared in a logical fashion to first detect datapath failure and then isolate the failure to a specific part of the composite muldem by a set of logical deductions.

Claims

1. Testing apparatus of the class described comprising, in combination:

high speed to low speed muldem apparatus comprising a plurality of multiplex-demultiplex modules where each of the modules interfaces between a common frequency and, depending on the application, one of either a customer low speed frequency or a high speed line frequency;

bit by bit comparator apparatus connected to each of said modules for testing the module by comparing data input to the module at the common frequency with data output by the module and returned through other datapaths where it is returned to the common frequency and checked for identity of logic value with the data input;

means for directing typical transmission line data to a module to be tested for operability and to said comparator apparatus; and

means for providing a return datapath connection, including reconversion means to said common frequency, for the non-common frequency terminals of said module to be tested to said comparator means for the bit by bit comparison testing.

2. Apparatus for converting between signals on a high speed multiplexed data transmission line and a plurality of lower speed multiplexed customer data transmission lines and for testing the conversion modules used therein comprising, in combination:

high speed first signal interface module means including multiplex and demultiplex portions, said first module means converting from a high speed frequency to a common frequency;

a plurality of low speed second signal interface module means each including multiplex and demultiplex portions, said second module means converting from a low speed customer frequency to said common frequency; and

testing third means connected to said first and second module means for selectively connecting a module in a test condition and receiving data therefrom at said common frequency from which to ascertain operability of the module being tested.

3. Muldem apparatus comprising, in combination:

at least one high speed to common frequency multiplex-demultiplex module;

a plurality of low speed to common frequency multiplex-demultiplex modules; and

bit by bit comparator test means, operating only at said common frequency, for testing, through signal datapath looped back conditions, any of said modules by comparing signals indicative of data input to and output from said modules.

4. Apparatus for checking communication equipment by rerouting data signals and comparing results comprising, in combination:

high speed signal interface first means including multiplex and demultiplex portions, said first means converting signals from a high to a common frequency;

a multiplicity of low speed signal interface second means including multiplex and demultiplex portions, said second means converting signals between a low speed and a common frequency;

standby high speed signal interface third means including multiplex and demultiplex portions, said third means converting signals from a high to a common frequency;

standby low speed signal interface fourth means including multiplex and demultiplex portions, said fourth means converting signals from a low speed to a common frequency;

bit by bit signal comparator testing fifth means including first and second input means;

control sixth means interconnecting said first through fifth means for normally routing signals between said first and said second means and alternately routing signals through said third and fourth means as apparent data transmission faults are detected in said first or said second means; and

interconnect seventh means for routing incoming signals through said demultiplex portion of said third means to said first input means of said fifth means and for also routing incoming high speed data signals which have completed their normal path through the demultiplex portions of said first means and said second means back through said multiplex portion of said fourth means to said second input means of said sixth means, a satisfactory comparison test indicating proper operation of the demultiplex portions of said first, second and third means and the multiplex portion of said fourth means.

5. The method of testing for datapath failure in a high speed/low speed muldem having primary and standby multiplexers and demultiplexers for operability while the system is actively passing data comprising, the steps of:

routing data signals, at a common frequency in a switching network between high speed and low speed muldem portions, between main units, between standby units and between main and standby units; and

comparing data bits input to and output from said muldem in a bit by bit comparator by demultiplexing the high speed signals in a standby high speed module and multiplexing the low speed signals in a standby low speed module, the outputs of said standby modules comparing identically when the main data paths are functioning properly.

6. The method of testing for datapath failure in a high speed/low speed muldem having primary and standby multiplexers and demultiplexers for operability while the system is actively passing data comprising, the steps of:

routing data signals, at a common frequency in a switching network between high speed and low speed muldem portions, between main units, between standby units and between main and standby units;

multiplexing signals received by the low speed portion of said muldem in a standby multiplexer to generate a first test signal;

multiplexing and demultiplexing the first test signal in a loopback configuration of the high speed standby muldem portion to generate a second test signal; and

comparing said first and second test signal on a bit by bit basis, the comparison equaling true when the standby high speed datapath is functioning properly.

7. The method of checking an operational muldem during data transmission having main high speed and main low speed sections and standby modules for each of said sections for datapath failure wherein the sections and modules include multiplexers and demultiplexers comprising, the steps of:

routing data signals, at a common frequency, in a switching network between the high speed sections, the low speed sections and the standby modules;

monitoring first and second test signals as applied for bit by bit comparison;

first checking the demultiplexer main sections by returning outgoing signals through appropriate standby low speed multiplexers to provide a first test signal for a first set of comparisons and by routing the incoming signal through the high speed standby demultiplexer to selectively provide a second test signal to be used in the first set of comparisons;

second checking the multiplexer main sections by selectively routing incoming signals through appropriate standby low speed multiplexers to provide a first test signal for a second set of comparisons and by alternately returning the outgoing signal through the high speed standby demultiplexer to selectively provide a second test signal to be used in the second set of comparisons;

third, when either of the first and second checks reveals a datapath failure, checking each individual datapath in the main high speed section by comparing as a third test signal the data signal at the common frequency and an alternate path version of said data as a second test signal supplied by the standby high speed demultiplexer for a third set of comparisons; and

finally, when either of the first and second checks reveals a datapath failure, checking each individual datapath in the main low speed section by comparing as a fourth test signal the data signal at the common frequency and an alternate path version of said data as a second test signal supplied by the standby low speed multiplexer for a fourth set of comparisons.

8. Apparatus for providing a frequency converting function between signals on a high speed multiplexed data transmission line and a plurality of lower speed multiplexed customer data transmission lines and for testing the conversion modules used therein comprising, in combination:

high speed first signal interface modules means including multiplex and demultiplex portions, said first module means providing a two-way function of converting signals between a high speed frequency and a common frequency;

a plurality of low speed second signal interface module means each including multiplex and demultiplex portions, said second module means providing a two-way function of signals between a low speed customer frequency and said common frequency; and

testing third means connected to said first and second module means for selectively connecting at least one module to be tested and receiving versions of data provided to and passed therethrough and returned to said testing third means at said common frequency from which data the apparatus may deduce the probability of satisfactory operation of the module being tested.

9. Muldem apparatus comprising, in combination:

high frequency to common frequency first interface module means including multiplex and demultiplex portions;

a plurality of common frequency to low frequency second interface module means each including multiplex and demultiplex portions;

datapath testing third means;

high speed data fourth means, connected to said first module means, for supplying data to and receiving data from said first means;

low speed data fifth means, connected to said second module means, for supplying data to and receiving data from said second means; and

control sixth means, connected to said first, second, third, fourth and fifth means, for selectively manipulating datapaths whereby said third means compares two data streams derived from muldem received data to test muldem operability.