Link adaptation for spatial multiplexing

A link adaptation apparatus for a transmitter node configured for spatial multiplexing of signals into streams and for transmission of spatially multiplexed streams over one or more forward channels including a first forward channel, wherein each stream is intended for a receiver node, the apparatus comprising controlling circuitry configured to cause:

• selection of a transmission pre-coding setting for at least one of the spatially multiplexed streams based on an acquired channel estimate of the first forward channel;
• estimation of a forward channel disturbance component based on the selected transmission pre-coding setting, wherein the forward channel disturbance component includes signal distortion for the first forward channel caused by at least one hardware component of the transmitter node and/or the receiver node;
• and
• performance of link adaptation for at least one of the spatially multiplexed streams based on the selected transmission pre-coding setting and the estimated forward channel disturbance component, wherein
• the controlling circuitry is configured to cause the estimation of the forward channel disturbance component by causing estimation of a disturbance covariance matrix based on the selected transmission pre-coding setting, the acquired channel estimate of the first forward channel, and a model of the signal distortion for the first forward channel.