Salam
STBC(Space Time Block Code) and STTC(Space Time Trellis Code) with common parameters and good design are the same in diversity gain, but STTC has coding gain and STBC dosnt have coding gain. then STTC has better performance(better BER) than STBC. but it is more complex. then it depend on application and BER performance need to use STBC and STTC