Techniques for coordinated beamforming in millimeter wave systems

A method for wireless communication at a transmission-reception point, comprising:

• performing individual beam training with a user equipment (UE), wherein performing the individual beam training comprises:
• transmitting beam swept synchronization signals to the UE;
• and
• receiving, from the UE, a first set of beams for non-coordinated transmission by the transmission-reception point and a signal strength for a plurality of beam pairs, each beam pair of the plurality of beam pairs comprising a beam of the first set of beams and a beam of a second set of beams for reception at the UE;
• receiving, from the UE, an indication of a plurality of co-phasing factors within an antenna panel of the transmission-reception point based at least in part on the individual beam training performed with the UE, wherein the plurality of co-phasing factors are based at least in part on a plurality of symbol estimates associated with the individual beam training;
• determining a coordinated beam for a coordinated beam training based at least in part on the plurality of co-phasing factors;
• transmitting, to the UE, a reference signal over the coordinated beam as part of the coordinated beam training with one or more additional transmission-reception points;
• and
• transmitting, to the UE, a beamformed transmission over the coordinated beam, the beamformed transmission coordinated with at least one joint beamformed transmission to the UE from the one or more additional transmission-reception points.

An apparatus for wireless communication at a user equipment (UE), comprising:

• a processor;
• memory in electronic communication with the processor;
• and
• instructions stored in the memory and executable by the processor to cause the apparatus to:
• perform individual beam training with a transmission-reception point of a plurality of transmission-reception points, wherein, to perform the individual beam training, the instructions are executable by the processor to cause the apparatus to:
• receive beam swept synchronization signals from the transmission-reception point;
• select, in response to the receiving, a first set of beams for non-coordinated transmissions by the transmission-reception point and a second set of beams for reception at the UE;
• and
• determine a signal strength for a plurality of beam pairs, each beam pair of the plurality of beam pairs comprising a beam of the first set of beams and a beam of the second set of beams;
• transmit, to the transmission-reception point, an indication of a plurality of co-phasing factors within a first antenna panel of the transmission-reception point based at least in part on the individual beam training performed with the transmission-reception point, wherein the plurality of co-phasing factors are based at least in part on a plurality of symbol estimates associated with the individual beam training;
• perform a coordinated beam training with the plurality of transmission-reception points based at least in part on the plurality of co-phasing factors;
• determine, based at least in part on the coordinated beam training, a set of beam weights for coordinated reception of a coordinated beamformed transmission comprising joint transmissions from the plurality of transmission-reception points to the UE;
• and
• receive, at the UE and based at least in part on the determining, the coordinated beamformed transmission from the plurality of transmission-reception points.

An apparatus for wireless communication at a transmission-reception point, comprising:

• a processor;
• memory in electronic communication with the processor;
• and
• instructions stored in the memory and executable by the processor to cause the apparatus to:
• perform individual beam training with a user equipment (UE), wherein, to perform the individual beam training, the instructions are executable by the processor to cause the apparatus to:
• transmit beam swept synchronization signals to the UE;
• and
• receive, from the UE, a first set of beams for non-coordinated transmission by the transmission-reception point and a signal strength for a plurality of beam pairs, each beam pair of the plurality of beam pairs comprising a beam of the first set of beams and a beam of a second set of beams for reception at the UE;
• receive, from the UE, an indication of a plurality of co-phasing factors within an antenna panel of the transmission-reception point based at least in part on the individual beam training performed with the UE, wherein the plurality of co-phasing factors are based at least in part on a plurality of symbol estimates associated with the individual beam training;
• determine a beam for a coordinated beam training based at least in part on the plurality of co-phasing factors;
• transmit, to the UE, a reference signal over the beam as part of the coordinated beam training with one or more additional transmission-reception points;
• and
• transmit, to the UE, a beamformed transmission over the beam, the beamformed transmission coordinated with at least one joint beamformed transmission to the UE from the one or more additional transmission-reception points.