Transmission error recovery for digital communication systems using variable length data packets where data is stored in header locations of memory

Decoder apparatus for receiving variable length data packets containing a header portion and a data portion from portions of successive lines of a data multiplex frame, and for 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 the data packet start addresses in designated locations of an address memory;
• means responsive to said data packet start addresses for storing data from the received data packets in designated locations in said data memory;
• means for recovering information, from the header portions of data packets being received, indicative of the length of the respective data packet for use in establishing data packet boundaries;
• means for recovering a plurality of next data packet position indicators from fixed positions in different lines of said data multiplex frame;
• and
• means for using said next data packet position indicators to reestablish correct data packet boundaries during the receipt of said data multiplex frame should an error occur in said data packet length information.

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.

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.