Transmission error recovery for digital communication systems

Claim 2

A method in accordance with claim 1 wherein said succession of variable length data packets is received within portions of successive lines of a data multiplex frame, said method comprising the further steps of: recovering information, from the header for a data packet currently being received, indicative of the length of said data packet; recovering a next data packet position indicator from data contained in one or more lines of said data multiplex frame; comparing a subsequent data packet position indicated by said next data packet position indicator to a subsequent data packet position indicated by the current data packet length information to determine if a correspondence exists; and relying on the next data packet position indicator instead of the current data packet length information to locate said subsequent data packet position in the event that said correspondence does not exist.

Claim 3

A method in accordance with claim 2 wherein: a plurality of next data packet position indicators are recovered to enable periodic verification of data packet boundaries during the receipt of said data multiplex frame and to provide a rapid recovery should an error occur.

Claim 5

Decoder apparatus for receiving variable length data packets containing a header portion and a data portion and storing encoded data from said data portions to enable prompt recovery from errors affecting the identified length of a data packet, comprising: means for assigning data packet start addresses to said received data packets, each data packet start address designating a location in a data memory for commencing the storage of data contained in the corresponding data packet; means for storing data from the header portions of said data packets together with the data packet start address for the corresponding data packet in designated locations of a header memory; and means responsive to said data packet start addresses for storing data from the received data packets in designated locations in said data memory.

Claim 6

Decoder apparatus in accordance with claim 5 wherein said variable length data packets are received within portions of successive lines of a data multiplex frame, said apparatus further comprising: means for recovering information, from the header for a data packet currently being received, indicative of the length of said data packet; means for recovering at least one next data packet position indicator from data contained in one or more lines of said data multiplex frame; means for comparing a subsequent data packet position indicated by a next data packet position indicator to a subsequent data packet position indicated by current data packet length information to determine if a correspondence exists; means responsive to the current data packet length information to locate a subsequent data packet in a received data stream in the event that said correspondence exists; and means responsive to said next data packet position indicator instead of the current data packet length information to locate said subsequent data packet in said received data stream in the event that said correspondence does not exist.

Claim 7

Decoder apparatus in accordance with claim 5 wherein said variable length data packets are received within portions of successive lines of a data multiplex frame, said apparatus further comprising: means for recovering information, from the header for a data packet currently being received, indicative of the length of said data packet; means for recovering at least one next data packet position indicator from data contained in one or more lines of said data multiplex frame; means responsive to the next data packet position indicator to locate a subsequent data packet in said received data stream upon recovery of the next data packet position indicator; and means responsive to the current data packet length information to locate a subsequent data packet in a received data stream when a next data packet indicator is not recovered to override the current data packet length information.

Claim 8

Decoder apparatus in accordance with one of claims 5 to 7 further comprising: means for reading the data packet start address for a stored data packet from said header memory; means for outputting the data portion of said stored data packet from said data memory commencing at the data packet start address read from said header memory; and data decoder means coupled to said data memory for receiving and decoding said output data portion.

Claim 9

Decoder apparatus in accordance with one of claims 5 to 8 further comprising: means for recovering information, from the header for a data packet currently being received, indicative of the length of said data packet; wherein said assigning means are responsive to said recovered information for generating the data packet start address for the data packet currently being received.

Claim 10

Decoder apparatus in accordance with claim 9 wherein: said data memory comprises a plurality of rows for storing data; and said assigning means provide a data packet start address pointing to a new row in said data memory for commencing the storage of data from each new data packet.

Claim 11

Decoder apparatus in accordance with one of claims 5 to 10 wherein said variable length data packets are received within portions of successive lines of a data multiplex frame, said apparatus further comprising: means for recovering at least one next data packet position indicator from data contained in one or more lines of said data multiplex frame; means for comparing a subsequent data packet position indicated by a next data packet position indicator to a subsequent data packet position indicated by current data packet length information to determine if a correspondence exists; means responsive to the current data packet length information to locate a subsequent data packet in a received data stream in the event that said correspondence exists; and means responsive to said next data packet position indicator instead of the current data packet length information to locate said subsequent data packet in said received data stream in the event that said correspondence does not exist.

Claim 12

Decoder apparatus in accordance with one of claims 5 to 10 wherein said variable length data packets are received within portions of successive lines of a data multiplex frame, said apparatus further comprising: means for recovering at least one next data packet position indicator from data contained in one or more lines of said data multiplex frame; means responsive to said next data packet position indicator to locate a subsequent data packet in said received data stream upon recovery of the next data packet position indicator; and means responsive to the current data packet length information to locate a subsequent data packet in a received data stream when a next data packet indicator is not recovered to override the current data packet length information.

Claim 13

Receiver apparatus for recovering variable length data packets from a received data stream, said data packets defining a data multiplex frame, comprising: means for recovering information, from a header for a data packet currently being received, indicative of the length of said data packet; means for recovering a plurality of next data packet position indicators provided in said data multiplex frame; means for comparing a subsequent data packet position indicated by a next data packet position indicator to a subsequent data packet position indicated by current data packet length information to determine if a correspondence exists; means responsive to the current data packet length information to locate a subsequent data packet in the received data stream in the event that said correspondence exists; and means responsive to said next data packet position indicator instead of the current data packet length information to locate said subsequent data packet in the received data stream in the event that said correspondence does not exist; wherein said next data packet position indicators enable periodic verification of data packet boundaries within said data multiplex frame during the receipt of said data stream should an error occur.

Claim 14

Receiver apparatus for recovering variable length data packets from a received data stream, said data packets defining a data multiplex frame, comprising: means for recovering information, from a header for a data packet currently being received, indicative of the length of said data packet; means for recovering a plurality of next data packet position indicators provided in said data multiplex frame; means responsive to a next data packet position indicator to locate a subsequent data packet in the received data stream upon the recovery of the next data packet position indicator; and means responsive to the current data packet length information to locate a subsequent data packet in the received data stream when a next data packet indicator is not recovered to override the current data packet length information; wherein said next data packet position indicators enable the periodic recovery of correct data packet boundaries within said data multiplex frame during the receipt of said data stream should an error occur.