Extended Uniform Channel Decomposition for MIMO Communications with Intersymbol Interference

In this paper, a joint design of a unitary precorder and a decision feedback equalizer (DFE) is considered to decompose a multi-input multi-output (MIMO) intersymbol interference (ISI) channel into multiple scalar layers with identical mean square errors (MSEs), and consequently, achieve much improved error probability performance over the standard DFE without a precoder. This design represents an extension of the existing uniform channel decomposition (UCD) scheme for frequency-flat MIMO channels. Therefore, it is named extended UCD (EUCD). In contrast to the trivial extension of the UCD scheme which uses the orthogonal frequency division multiplexing (OFDM) to obtain multiple frequency flat channels and applies the standard UCD to each of them, the EUCD scheme uses a MIMO minimum-mean square error decision feedback equalizer (MMSE-DFE) to eliminate ISI and only needs one precoder for the entire broadband. To eliminate error propagation, another form of the EUCD is also presented which uses the dirty paper coding (DPC) to cancel ISI at the transmitter. The practical implementation aspect is also considered. An example via numerical simulation validates the remarkable performance of the EUCD in terms of uncoded error probability.