Channel sounding for distributed transmission

Abstract

A method for a primary wireless transmitter is disclosed. The primary wireless transmitter is configured to participate in transmission to a wireless receiver using spatial multiplexing in coordination with one or more secondary wireless transmitters. The method comprises assigning—from a collection of available channel sounding resources—respective channel sounding resources to the primary wireless transmitter and to the one or more secondary wireless transmitters, wherein each available channel sounding resource is assigned to at most one of the wireless transmitters. Each assigned respective channel sounding resource is for transmission of a respective non-spatial-multiplexed first channel sounding signal, and the first channel sounding signals are for phase tracking of signals transmitted by the primary wireless transmitter and/or for phase tracking of signals transmitted by the one or more secondary wireless transmitters. The method also comprises transmitting, to the one or more secondary wireless transmitters, information indicative of the respective channel sounding resources assigned to the one or more secondary wireless transmitters. Methods for the secondary wireless transmitters and the wireless receiver are also disclosed, as well as corresponding apparatuses, transmitter, receiver, access point, user station, control node, and computer program product.