Method and apparatus for channel sounding for a mu-mimo wireless communication network

A multi user multiple input multiple output (MU-MIMO) wireless communication network comprising an access point and at least a first subscriber module of a first sounding group of subscriber modules,

• the access point comprising a processor configured to cause the access point to form a respective MU-MIMO beam from the access point to each subscriber module of the first sounding group of subscriber modules by applying a beamforming weightset to a weighting matrix, the beamforming weightset having been determined on the basis of previously determined channel estimates, and to use each MU-MIMO beam to transmit a respective sounding symbol, each respective sounding symbol being different from each other sounding symbol of the first sounding group, and
• the first subscriber module of the first sounding group, comprising a processor configured to cause the first subscriber module to receive a first sounding symbol transmitted to the first subscriber module in a respective MU-MIMO beam, and to determine whether to send a response message to the access point in response to the receipt of the first sounding symbol on the basis of a determination of a received level of interference to the first sounding symbol.

A method of operating a subscriber module in a multi user multiple input multiple output (MU-MIMO) wireless communication network comprising an access point and a plurality of subscriber modules, the method comprising:

• receiving a first sounding symbol at the subscriber module, the subscriber module being in a first sounding group of subscriber modules, the first sounding symbol having been transmitted from the access point in a first MU-MIMO beam, the first MU-MIMO beam having been formed using a weighting matrix to form a respective MU-MIMO beam from the access point to each subscriber module of the first sounding group to transmit simultaneously a respective sounding symbol for each beam to each subscriber module, each respective sounding symbol being different from each other sounding symbol of the first sounding group, the beamforming weightset for the weighting matrix having being determined on the basis of previously determined channel estimates;
• and
• determining whether to send a response message to the access point in response to the receipt of the first sounding symbol on the basis of a determination of a received level of interference to the first sounding symbol.

A subscriber module for use in a multi user multiple input multiple output (MU-MIMO) wireless communication network comprising an access point and a plurality of subscriber modules, the subscriber module comprising a processor configured to cause the subscriber module to:

• receive a first sounding symbol at the subscriber module, the subscriber module being in a first sounding group of subscriber modules, the first sounding symbol having been transmitted from the access point in a first MU-MIMO beam, the first MU-MIMO beam having been formed using a weighting matrix to form a respective MU-MIMO beam from the access point to each subscriber module of the first sounding group to transmit simultaneously a respective sounding symbol for each beam to each subscriber module, each respective sounding symbol being different from each other sounding symbol of the first sounding group, the beamforming weightset for the weighting matrix having being determined on the basis of previously determined channel estimates;
• and
• determine whether to send a response message to the access point in response to the receipt of the first sounding symbol on the basis of a determination of a received level of interference to the first sounding symbol.