Depending on the specifics of a cost-sharing situation, one or more classes of wireless licensees may be impacted by a cost-sharing event. Regardless of who the players may be, three predecessors must occur in order for cost sharing to be triggered:

1. a relocation of an incumbent facility that was eligible for reimbursement at the new entrant's expense, and
   
   
2. the registration of this incumbent relocation with the CTIA Spectrum Clearinghouse, and



3. a subsequent beneficiary to this relocation filing base station information with the CTIA Spectrum Clearinghouse that is within a certain distance of the relocated facility and is co-channel to the same facility.

Typically, an incumbent relocation involves an Advanced Wireless Service ("AWS") or Mobile Satellite Service ("MSS") licensee, acting as a Relocator, to move an Incumbent user of the 2.1 GHz spectrum to alternative communication means in an effort to avoid potential interference. Then, the relocator registers the details of its relocation with the CTIA Spectrum Clearinghouse, LLC for cost-sharing purposes. Finally, the CTIA Spectrum Clearinghouse continuously performs Proximity Threshold Tests to identify situations where the later entrant(s) may have benefitted from another's spectrum clearing effort based on details of its base stations deployment information (PCN). The FCC has mandated that all who benefit from this spectrum-clearing activity must share in the associated costs.

AWS/MSS Licensee – An entity granted an FCC license to operate in the 1710-1755 MHz and 2110-2155/2180-2200 MHz spectrum frequency bands.

Incumbent – Broadband Radio Service (BRS) provider currently operating in the 2150-2160/62 MHz spectrum band or a Fixed Microwave Service (FS) carrier currently operating in the 2110-2150 MHz and/or 2160-2200 MHz spectrum bands.

Licensee – An AWS or MSS Licensee.

Relocator –  Either: (i) a Licensee that has paid consideration to an Incumbent, pursuant to a relocation agreement, to relocate or otherwise terminate the operations of such Incumbent licensed system operating in the AWS bands; or (ii) a Fixed Service Microwave Incumbent that has expended resources in order to voluntarily relocate its licensed system out of the AWS spectrum band.