Systems and methods related to a null-space for a MIMO transmitter system

A processing system for a Multiple Input Multiple Output, MIMO, Orthogonal Division Multiplexing, OFDM, transmitter system, the processing system comprising:

• precoder circuitry configured to precode a plurality of frequency-domain input signals to provide frequency-domain precoded signals for a plurality of subcarriers, the plurality of frequency-domain input signals comprising information for one or more transmit layers;
• and
• processing circuitry configured to process the frequency-domain precoded signals in accordance with a Convex Reduction of Amplitude, CRAM, based processing scheme to provide a plurality of time-domain precoded signals for a plurality of respective transmit branches of the MIMO OFDM transmitter system, wherein:
• the CRAM-based processing scheme uses a plurality of projection matrices for the plurality of subcarriers, respectively, to project clipping energy into a null space of the MIMO OFDM transmitter system;
• and
• the plurality of projection matrices are a function of static or semi-static information that defines the null space of the MIMO OFDM transmitter system, the static or semi-static information being static or semi-static information that relates to physical directions at which transmit power of the MIMO OFDM transmitter system is less than a threshold transmit power level.

A method performed by a processing system for a Multiple Input Multiple Output, MIMO, Orthogonal Division Multiplexing, OFDM, transmitter system, the method comprising:

• obtaining a plurality of projection matrices for the plurality of subcarriers, respectively, that are a function of static or semi-static information that defines a null space of the MIMO OFDM transmitter system, the static or semi-static information being static or semi-static information that relates to physical directions at which transmit power of the MIMO OFDM transmitter system is less than a threshold transmit power level;
• and
• using the plurality of projection matrices to generate a plurality of transmit signals for a plurality of respective transmit branches of the MIMO OFDM transmitter system,
• wherein the static or semi-static information comprises:
• (a) one or more physical characteristics of an antenna array of the MIMO OFDM transmitter system, (b) a physical deployment of one or more cells of a radio access network served by a base station in which the MIMO OFDM transmitter system is implemented, (c) a physical deployment of wireless communication devices within a coverage area of one or more cells of a radio access network served by a base station in which the MIMO OFDM transmitter system is implemented, (d) historical channel information for one or more wireless communication devices, or (e) a combination of any two or more of (a)-(d).