A novel space-time LDPC code with time varying precoding

In this paper, a novel space-time low-density parity-check (LDPC) code with full diversity is studied. Precoded by time varying linear transformations (TVLT), space-time LDPC codes can achieve full transmit diversity gain without the intricate requirements of exhaustive tests according to the conventional criterions. A proposed lemma about the effects of TVLT on space-time codes is revised and reproved. With a view to the necessary condition of the application of TVLT to space-time codes, a tight upper bound on the minimum Hamming distances of LDPC codes is discussed. Combined with the favourable distance property of LDPC codes, the time varying precoding provides space-time codes with the full transmit diversity as well as the reasonable coding gain compared with that of the conventional counterparts.