Valve does not publish documentation about the protocol transmitted by Lighthouse base stations. Some external-to-Valve engineers have reverse-engineered the protocol and provide documentation at the following locations:
Note: this is not Valve-sanctioned information and while it may be useful for current implementations, Valve reserves the right to change the protocol at anytime in the future. Also, note that Triad is not speaking for Valve on this subject but is rather stating a Triad opinion. With all that said, this documentation is useful for understanding how the current system works.