Error monitoring in digital transmission systems
AssigneeBell Telephone Laboratories, Incorporated
InventorRobert D. Howson
Life of this patent
Estimating the term…
Abstract
Errors in digital transmission are monitored by employing a cyclical-redundancy-check (CRC). A CRC code word having a predetermined number of bits is generated (via 310) from a block of bits (ESF) of a presently transmitted time division muliplexed (XTDM) signal. The code word bits are then inserted (via 304, 305, 306) into predetermined bit positions of the next subsequent block of bits (ESF) of the XTDM signal. In a receiver (FIG. 7), bits of a presently received time division multiplexed (RTDM) signal are compared (801, 802) to bits of a CRC code word generated from the last previously received block of bits to indicate errors in transmission. In a specific example, a 6-bit CRC code word is employed and the code word bits are inserted into predetermined framing bit positions.
Claims14
Apparatus for formatting a time division multiplexed signal including a series of blocks of bits, each block including a plurality of data bits and a plurality of additional bit positions,
- characterized by
- means (310) responsive to bits in a block of bits of the time division multiplexed signal (XTDM) for generating in accordance with a prescribed criterion a code word (CRC BITS) having a predetermined number of bits less in number than the plurality of additional bit positions;
- and
- means (301, 304-306) for inserting said code word bits in predetermined ones of the additional bit positions of a subsequent block of bits of the time division multiplexed signal being transmitted to monitor errors in transmission.
Apparatus for monitoring a received time division multiplexed signal including a series of blocks of bits, each block including a plurality of data bits and a plurality of additional bit positions,
- characterized by
- means (702) responsive to all the bits of a block of bits of the received time division multiplexed signal (RTDM) for generating accordance with a prescribed criterion a code word (CRC BITS) having a predetermined number of bits less in number than the plurality of additionsal bit position;
- and
- means (703) for comparing said code word bits with bits of a subsequent received block of bits of the time division multiplexed signal to generate error indications.
Apparatus for transmitting and receiving time division multiplexed signals including a series of blocks of bits, each block including a plurality of data bits and a plurality of additional bit positions,
- characterized by
- means (300) for formatting the time division multiplexed signal (XTDM) including means (310) responsive to bits in a block of bits of the time division multiplexed signal (XTDM) for generating in accordance with a prescribed criterion a code word (CRC BITS) having a predetermined number of bits less in number than the plurality of additional bit positions, and means (301, 304-306) for inserting said code word bits in predetermined ones of the additional bit positions of a subsequent block of bits of the time division multiplexed signal being transmitted to monitor errors in transmission;
- and
- means (700) for monitoring a received time division multiplexed signal including means (702) responsive to bits of a block of bits of the received time division multiplexed signal (RTDM) for generating in accordance with a prescribed criterion a code word (CRC BITS) having a predetermined number of bits less in number than the plurality of additional bit positions, and means (703) for comparing said code word bits with bits of a subsequent received block of bits of the time division multiplexed signal to generate error indications.
A method for formatting a time division multiplexed signal including a series of blocks of bits each block including a plurality of data bits and a plurality of additional bit positions, the method comprising the steps of:
- generating a code word having a predetermined number of bits less in number than the plurality of additional bit positions from bits in a block of bits of the time division multiplexed signal in accordance with a prescribed criterion;
- and
- inserting the code word bits in predetermined ones of the additional bit positions of a subsequent block of bits of the time division multiplexed signal.
A method for monitoring errors in a received time division multiplexed signal including a series of blocks of bits each block including a plurality of data bits and a plurality of additional bit positions, the method comprising the steps of:
- generating a code word having a predetermined number of bits less in number than the plurality of additional bit positions from bits of a block of bits of the time division multiplexed signal in accordance with a prescribed criterion;
- and
- comparing the code word bits with bits of a subsequent received block of bits of the time division multiplexed signal to generate error indications.
Dependencies are inferred from the claim text.