An Analysis of the Effectiveness of Hybrid Transmission Schemes

A comparison is made of the performance of pure retransmission, forward error correction and hybrid (error detecting/correcting) schemes for data transmission in a noisy (probability of error, P > 10
⁻⁴
) binary symmetric channel. The performance calculations are based on the use of BCH codes for error detection and correction up to the full correction capability of the code. It is shown that a probability of undetected error of less than 10
⁻⁹
error/bit, can be achieved by correcting only a few errors while retaining a reasonable throughput and a very low retransmission rate. The best codes in the class considered are specified and the complexity of instrumentation is estimated. Finally, various combinations of possible systems employing half duplex and reverse channel operation are used in a comparison of the transmission schemes. For line error rate worse than 10
⁻⁴
error/bit, a hybrid system operating with a reverse channel is superior to the other possibilities.