Layered turbo space-time coded MIMO-OFDM systems for time varying channels

A joint detection-estimation scheme is proposed for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. The transmitter employs a layered turbo space-time code. The iterative scheme proposed for the receiver integrates in one scheme turbo decoding, co-antenna interference suppression and channel estimation. A main observation is that the high coding gain of the turbo space-time code can compensate for the application of a simple co-antenna interference suppression scheme and can also facilitate good channel estimates. The performance of the MIMO-OFDM system is validated by simulations under various channel conditions, including high Doppler. Numerical results show that for a 4 transmit 4 receive antenna (4T4R) system, with a data rate of 4 Mb/s over a 1.25 MHz bandwidth, a packet error rate (PER) of 10^-2 is achieved at a signal-to-noise ratio (SNR) of 16 dB for a typical urban channel with Doppler frequencies as high as 200 Hz. For a 4T6R system, the same performance can be achieved for only 6 dB SNR.