Potential users of band react to FCC refusal to settle interference dispute.

A plan to fix problems with the FCC’s novel licensing scheme in the 3650-3700 MHz band has come from the Fixed Wireless Communications Coalition (FWCC), a diverse group of fixed microwave users, providers, and manufacturers.

The 3650-3700 MHz band is unusual. In most shared bands, the rules require frequency coordination prior to licensing. A coordinator tries to slot each newcomer’s application into a frequency band where it will neither cause interference to incumbents, nor receive interference. The scheme protects those in first from those who arrive later, although the degree of protection varies with the type of service.

In the 3650-3700 MHz band, however, the FCC has established a kind of do-it-yourself frequency coordination on the fly. Before starting operation, each incoming user is expected to consult a database of other users, and to tailor the new station’s locations and parameters to avoid causing interference. The new location and parameters then go into the database for the guidance of those who come later. Licensees are expected to resolve any interference problems among themselves. The rules also require the use of “contention protocols” in the equipment to help prevent interference problems from arising in the first place.

It turns out the FCC means what it says about people working out problems on their own. A licensee in the band went to the FCC with a complaint that a newcomer had not bothered to check the database, was causing interference, and had not cooperated in fixing it. To the surprise of many, the FCC refused to intervene, reiterating that it would leave a resolution to the parties. We reported on the case back in December.

The FWCC expressed concern about this outcome, fearing that users with critical applications are likely to avoid the band, rather than risk interference over which they have no control. 

Part of the problem, it thinks, is that some of the key rules for the band use language that is merely advisory. The FWCC does not ask the FCC to play referee (a role the Commission plays in other contexts) – but it does want the rules reworded to make users’ responsibilities more clear.

Specifically, where the rule now says that licensees “should” consult the database, “should” try to avoid causing interference, and “are expected to” cooperate in resolving interference issues, the FWCC asks for an amendment to make these steps mandatory. This, the FWCC suggests, will preserve the speedy set-up and flexibility offered by the present rules, while improving the quality of service and giving providers better assurance that they can reliably meet customers’ needs.

Read the FWCC’s petition here.