Transceiver Design for MIMO Systems with Imperfect CSI at Transmitter and Receiver

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We consider transceiver design in uncoded multiple-input multiple-output (MIMO) systems with noisy channel state estimates. Specifically, we design a transceiver that takes into account the statistics of the CSI errors red to minimize the average bit average rate (BER) of the system. Our design utilizes the noisy CSI estimates and the error statistics at the transmitter to partition the spatial channels into `almost' independent streams. We also propose a joint bit and power loading (allocation) scheme to allocate information rate and power to each channel stream. Exact maximum likelihood (ML) decoding incurs a high complexity at the receiver; to circumvent this, stream-by-stream ML decoding is used at the receiver. We verify, via numerical results, that for a $4 \times 4$ system, the BER performance of the proposed joint bit and power loading transmission scheme far surpasses that of the schemes where only bit loading or only power loading is used. At a BER of $10^{-4}$, the joint bit and power loading scheme has an approximately 4dB gain over the bit loading scheme. In contrast, the scheme which ignores CSI errors has poor BER performance.