Space-frequency bit-interleaved convolutional and turbo coded OFDM systems with simplified iterative approaches

In this paper, space–time bit–interleaved coded OFDM (orthogonal frequency division multiplexing) modulated systems are studied. Using multiple antennas at transmitter and receiver side, spatial diversity can be exploited with ordinary channel codes followed by an interleaver. Moreover, the combined use with OFDM modulation enable effective frequency selectivity exploitation in multipath channels. High spectral efficiency can be achieved using high modulation orders and increasing the number of transmitting antennas. Asymptotical performances are analyzed using pairwise error probability evaluation. It is shown as transmission parameters and radio channel characteristics impact on achievable diversity order and coding gain. Different channel codes are taken into account. Convolutional codes with several constraint lengths are simulated and results are compared with those of turbo coded solution. The iterative receiver complexity grows at the increase of modulation order, subcarriers and number of antennas. Simplified detection criterions can be used for signals separation at receiver side. Turbo coded system allows for iterative approaches with reduced complexity when some turbo decoding iterations are performed between successive detection steps.