Circularly orthogonal sequences were designed for the time-domain channel estimation in MIMO SC-FDE systems.Firstly

Chu sequences were chosen as the base sequences

which were added by cyclic prefix and cyclic postfix to construct circularly orthogonal training sequences.The channel impulse response can be estimated by calculating the cross-correlation between the received signal and the corresponding local sequence.Further

a new training sequence structure was presented

in which the original "long" training sequences were replaced by successive and identical "short" sequences.The corresponding estimation algorithm achieves the same performance as "long" sequences based method.Simulation results show that the proposed algorithms can offer good BER performance even at low SNR

due to the successful interference suppression between the antennas and the decrease in the noise variance.