PHR

Technical Explanation

The Power Headroom Report indicates how much spare transmit power remains in the UE's RF power amplifier before reaching P_CMAX: Power Headroom = P_CMAX - P_estimated. If PHR is positive (e.g. +12 dB), the gNodeB scheduler can assign more PRBs or higher MCS. If PHR is negative or zero, the UE is power-limited.

Key Functions

• Reports headroom between actual transmit power and maximum power P_CMAX
• Transmitted as MAC Control Element triggered by pathloss changes or timers
• Guides gNodeB scheduler in allocating uplink bandwidth and MCS