Although IH-TCM has a defect that the decoding delay is long, the results obtained in 3 have shown that IH-TCM acheives large asymptotic coding gain and is easy to emplement. For constructing IH-TCM system, use of the asymptotic coding gain is a convenient way of estimation for the reliability. However, it must be used carefully. In some cases, IH-TCM which shows high reliability and small complexity in computer simulation is not the same as that obtaind by maximizing asymptotic coding gain.
We have shown some bit error performances of IH-TCM and U-TCM obtaind by computer simlation. It follows from the result that there are IH-TCM systems with smaller complexity of implementation than U-TCM systems having the same decoding error probability at a practical SNR.
The results of computer simulation have been given for only a few cases of IH-TCM systems. However, they suggest that IH-TCM has the possibility of being a practical way to realize highly reliable and efficient communication systems.