Method and apparatus for power headroom reporting procedure for new radio carrier aggregation

An apparatus comprising:

• at least one transceiver that communicates on a first serving cell having a first subcarrier spacing resulting in a first slot length and a second serving cell having a second subcarrier spacing resulting in a second slot length, the first subcarrier spacing being smaller than the second subcarrier spacing resulting in the first slot length being larger than the second slot length;
• and
• a controller coupled to the transceiver, where the controller ascertains that a power headroom report has been triggered for at least one selected from the first serving cell and the second serving cell,
• wherein apparatus has an uplink allocation corresponding to an uplink transmission in an allocated slot on the first serving cell, the allocated slot on the first serving cell overlapping with multiple slots on the second serving cell, wherein the multiple slots on the second serving cell include at least one fully overlapping slot starting with a first fully overlapping slot on the second serving cell that fully overlaps with the allocated slot on the first serving cell,
• wherein the controller generates a first power headroom report for the first serving cell based on the allocated slot on the first serving cell, the controller determines a power headroom report reference slot on the second serving cell, and the controller generates a second power headroom report for the second serving cell based on the power headroom report reference slot,
• wherein the transceiver transmits the first power headroom report and the second power headroom report in the uplink transmission,
• wherein the power headroom report reference is determined as the first fully overlapping slot on the second serving cell.