Sprint, T-Mobile and Dish Network are teaming up to ensure smaller carriers can get their hands on low-band spectrum.

Along with regional carrier C Spire Wireless, the Competitive Carriers Association and advocacy groups like Public Knowledge, the group is lobbying the FCC to adopt rules in the upcoming 600 MHz auctions that will benefit carriers other than AT&T and Verizon, who together hold the majority of available below-1 GHz spectrum licenses.

“While many parties to this letter support additional measures to spur wireless broadband competition, our organizations have reached consensus on four principles that should serve as the foundation of any spectrum aggregation policy,” according to the joint filing.

The principles outlined touch on the need for aggregation limits on spectrum below 1 GHz; the need for clear limits in place prior to the incentive auctions; the need for rules to address market realities; and the need for a weighting policy for spectrum in all bands.

“These principles are not the only mechanisms necessary for a successful auction, but are important guidelines that emerged as the consensus view among our diverse group of stakeholders,” the group wrote in the filing.

The FCC’s highly anticipated 600 MHz auctions aren’t scheduled to take place until mid-2015 but already all major carriers and other interest parties have weighed in almost daily regarding the NPRM.

AT&T and Verizon have argued that spectrum aggregation limits could initiate a number of negative impacts on the incentive auctions, with special emphasis on the possibility of spectrum caps lowering auction revenue.