Multiple-input multiple-output (MIMO) communication techniques make use of multielement antenna arrays at both the TX and the RX side of a radio link and have been shown theoretically to drastically improve the capacity over more traditional single-input multiple output (SIMO) systems [2, 3, 5, 7]. SIMO channels in wireless networks can provide diversity gain, array gain, and interference canceling gain among other benets. Here we suggest a simple classification of MIMO channel and devise a MIMO channel model whose generality encompasses some important practical cases. Unlike the channel model used in [3, 15], our model suggests that the impact of spatial fading correlation and channel rank are decoupled although not fully independent, which allows for example to describe MIMO channels with uncorrelated spatial fading at the transmitter and the receiver but reduced channel rank (and hence low capacity).