| 摘要 |
A DATA COMMUNICATIONS UNIT DETERMINES BOTH EFFICIENTLY AND ACCURATELY WHEN ONE OR MORE DATA UNITS SHOULD BE RECEIVED UNDER A VARIETY OF CONDITIONS.IN PARTICULAR, THE PRESENT INVENTION COMPENSATES FOR TRANSMISSION DELAYS AND FOR VARYING TRANSMISSION RATES OVER THE COMMUNICATIONS CHANNEL. DURING A COMMUNICATION BETWEEN FIRST (12) AND SECOND (14) COMMUNICTAIONS NODES, THE FIRST (12) RECEIVES A SEQUENCE OF DATA UNITS TRANSMITTED FORM THE SECOND NODE (14). THE FIRST COMMUNICATIONS (12) NODE DETERMINES THAT ONE OR MORE OF THE TRANSMITTED DATA UNITS WAS EITHER NOT RECEIVED AT ALL OR WAS ERRONEOUSLY RECEIVED (I.E. CORRUPTED) (BLOCK 24). THE FIRST NODE (12) THEN SENDS A REQUEST TO THE SECOND NODE (14) TO RETRANSMIT THE ONE OR MORE DATA UNITS NOT RECEIVED OR ERRONEOUSLY RECEIVED. A RETRANSMIT TIMER (94) IS STARTED WHEN THE RETRANSMISSION REQUEST IS SENT (BLOCK 28). THE RETRANSMIT TIMER (94) ACCOUNTS FOR THE DELAY TIME PERIOD REQUIRED FOR THE RETRANSMIT REQUEST TO REACH THE SECOND NODE (14), FOR THE SECOND NODE (14) TO TRANSMIT THE REQUESTED DATA UNITS, AND FOR THE RETRANSMITTED DATA UNITS TO REACH THE FIRST NODE (12). WHEN THE TIMER (94) INDICATES THAT THE DELAT TIME PERIOD HAS OCCURRED/EXPIRED, A COUNTER (92) IS STARTED. BASED ON THE COUNTER'S VALUE, A DETERMINATION IS MADE WHETHER ALL OF THE DATA UNITS REQUESTED TO BE RETRANSMITTED HAVE BEEN PROPERLY RECEIVED , NO FURTHER ACTION IS TAKEN. ON THE OTHER HAND, IF THE REQUESTED ONE OR MORE DATA UNITS TO BE RETRANSMITTED IS NOT RECEIVED OR IS ERRONEOUSLY RECEIVED, THE ABOVE-DESCRIBED PROCEDURE IS REPEATED.(FIG 1).
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