Channel sounding for distributed transmission

A method of operating a secondary wireless transmitter configured to participate in transmission to a wireless receiver using spatial multiplexing in coordination with at least a primary wireless transmitter, the method comprising:

• receiving, from the primary wireless transmitter, information indicative of respective channel sounding resources from a collection of available channel sounding resources, the respective channel sounding resources assigned to the secondary wireless transmitter;
• wherein each channel sounding resource assigned to the secondary wireless transmitter is assigned only to the secondary wireless transmitter;
• wherein each assigned respective channel sounding resource is for transmission of a respective non-spatial-multiplexed first channel sounding signal;
• wherein 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 secondary wireless transmitter.

A method of operating a wireless receiver configured to receive spatial multiplexing transmissions from a primary wireless transmitter in coordination with one or more secondary wireless transmitters, the method comprising:

• receiving, from one or more of the primary and secondary wireless transmitters, information indicative of respective channel sounding resources from a collection of available channel sounding resources, the respective channel sounding resources assigned to the primary and secondary wireless transmitters;
• wherein each available channel sounding resource is assigned to at most one among a set of wireless transmitters comprising the primary wireless transmitter and the one or more secondary wireless transmitters;
• wherein each assigned respective channel sounding resource is for transmission of a respective non-spatial-multiplexed first channel sounding signal;
• wherein 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.

An apparatus for a control node of a system comprising a primary wireless transmitter configured to participate in transmission to a wireless receiver of the system using spatial multiplexing in coordination with one or more secondary wireless transmitters of the system, the apparatus comprising:

• processing circuitry;
• memory containing instructions executable by the processing circuitry whereby the apparatus is operative to cause:
• assignment, 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 among a set of wireless transmitters comprising the primary wireless transmitter and the one or more secondary wireless transmitters;
• wherein each assigned respective channel sounding resource is for transmission of a respective non-spatial-multiplexed first channel sounding signal;
• and
• wherein 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.

A wireless communications system, comprising:

• a primary wireless transmitter configured to participate in transmission to a wireless receiver using spatial multiplexing in coordination with one or more secondary wireless transmitters, the primary wireless transmitter comprising:
• first processing circuitry configured to cause the primary wireless transmitter to:
• assign, 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 among a set of wireless transmitters comprising the primary wireless transmitter and the one or more secondary wireless transmitters;
• wherein each assigned respective channel sounding resource is for transmission of a respective non-spatial-multiplexed first channel sounding signal;
• and wherein 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;
• and
• transmit, 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;
• a secondary wireless transmitter configured to participate in the transmission to the wireless receiver using spatial multiplexing in coordination with at least the primary wireless transmitter, the secondary wireless transmitter comprising:
• second processing circuitry configured to cause the secondary wireless transmitter to:
• receive, from the primary wireless transmitter, information indicative of the respective channel sounding resources assigned to the secondary wireless transmitter;
• wherein each channel sounding resource assigned to the secondary wireless transmitter is assigned only to the secondary wireless transmitter.