The C-Band Alliance (CBA), a coalition of satellite service providers, strengthened a proposal to open key mid-band spectrum to US mobile operators, adding 100MHz of bandwidth to a prior offer.

In a filing with the Federal Communications Commission (FCC), the group offered to make a total of 280MHz of spectrum between 3.7GHz and 4.2GHz (C-Band) available to mobile operators through a private auction. It pledged to make 100MHz of the total available in the top 46 metropolitan areas in the country within 18 months and the remainder within 36 months.

CBA added it reached a consensus with major operators including AT&T, Verizon and US Cellular on guidelines for the proposed sale. The updated plan is a significant jump from the 180MHz CBA previously proposed: the group said it was able to increase its offer thanks to advanced technologies which improve the efficiency of satellite video delivery.

The CBA’s offer comes as the FCC scrambles to make mid-band spectrum available to operators for 5G deployments. The spectrum is in short supply in the US, but is considered critical for the next-generation technology because it offers a good balance of coverage and capacity compared with low-band or mmWave.

Opening the C-Band would bring the country into closer alignment with others across the globe which have already earmarked the spectrum for next generation deployments.

However, the move comes as pressure mounts on the FCC to hold a public auction for the band, rather than allowing CBA to manage the sale.

Last week, US politicians introduced new legislation which would require the FCC to conduct a public auction of at least 200MHz of C-Band spectrum by 30 September 2022.

The FCC is currently weighing its options, with a decision expected before the end of 2019.