Multicarrier communication is a technique for transmitting data that divides the data into multiple portions and then transmits the portions in parallel via a number of separate narrowband carriers. In a multicarrier channel, multipath fading can cause the transmission coefficients associated with one or more subcarriers to be low while those associated with other subcarriers are high. These low transmission coefficients can result in a poor quality signal in the receiver for these subcarriers (e.g., low signal to noise ratio (SNR)), which may reduce the receiver's ability to reliably demodulate and decode the corresponding data. In many cases, the subcarriers that experience bad fading will occur in clusters.
One technique for reducing the effects of multipath fading is known as multiple input, multiple output or MIMO. MIMO is a wireless communication technique that uses multiple antennas at each end of a communication channel (or at least at one end) to provide multiple spatial channels through which signals may propagate. MIMO can reduce some of the negative effects of fading by spreading signals across several channels with relatively independent fading characteristics. However, even when MIMO is being using, bit error rates can still be too high due to impulse or frequency noise that effects some or all of the channels at the same time. New techniques are needed for effectively dealing with fading in MIMO based systems.