A lossless layered coding strategy for MIMO systems

This paper provides a simple solution to a long standing problem of applying long block codes to multiple-input multiple-output (MIMO) quasi-static or slowly time-varying fading channels, in which past coding strategy may suffer unnecessary outage if maximum likelihood decoding is too complex to be employed. The solution is to avoid outage by employing a layered coding strategy using a rateless code at a layer. An acknowledgment is sent from the receiver to the transmitter when the receiver has accumulated enough information to decode. In a transmission, a codeword may span one or a few fading blocks. However, the total long term transmission rate can approach the ergodic capacity, and therefore, is lossless compared to outage events in traditional coding strategy. The theoretical tool introduced is a generalization of Feinstein´s lemma for channels with acknowledgement. It represents a departure from traditional Shannon channel capacity that characterizes the data rate of one transmission of a code word