Joint training interval length and power allocation optimization for MIMO flat fading channels

In this paper, we jointly optimize the training interval length and the power allocation for MIMO (multiple-input multiple-output) flat fading channels when a maximum a posteriori (MAP) detector is used at the receiver and the training and data powers are allowed to vary. We calculate the equivalent signal-to-noise ratio (SNR) at the output of the MAP detector. Based on this expression, we define an effective SNR taking into account the data throughput loss due to the use of pilot symbols. We find that the optimal length of the training interval maximizing this quantity is equal to the number of transmit antennas. When the values of the pilot and data powers are not allowed to be different, we give the optimal training interval length maximizing the effective SNR and we show that it can be larger than the number of transmit antennas.