Wireless MRI coils require a local frequency reference that is very tightly synchronized with the main MRI system clock. In order to keep phase encoding errors to less than 1 degree of phase at 3T, the local reference clock cannot drift by more than +/-22ps. Unlike RF cables or optical fibers, a wireless communication channel is not constant in phase over time. Patient motion and multi-path fading cause the wireless signal to be modulated in amplitude and phase. When disciplining a local clock with the MRI system clock by wireless means, channel impairments have to be monitored and corrected.