An implementation provides a system that includes: a control module including a first antenna, the control module configured to generate a first radio frequency (RF) signal and transmit the first RF signal using the first antenna; an implantable lead module including a second antenna and at least one electrode configured to stimulate excitable tissue of a subject; and a relay module configured to receive the first RF signal; generate a second RF signal based on the first RF signal, the second RF signal encoding a stimulus waveform to be applied by the at least one electrodes of the implantable lead module to stimulate the excitable tissue of the subject; and transmit the second RF signal to the implantable lead module.