Boeing Satellite Systems International has signed up to build a fleet of seven satellites that will provide broadband internet connectivity from medium Earth orbit for SES’ O3b network.

O3b was set up a decade ago to provide internet access to the “Other 3 Billion” in the world who have been left out because they’re too remote or too poor to get connected. Last year, SES took over majority ownership of O3b Networks, which currently has 12 first-generation satellites in a 5,000-mile-high orbit.

Eight more of the first-generation satellites, also built by Boeing, are to be launched in 2018 and 2019 on Russian-built Soyuz rockets by the European Arianespace consortium. Boeing’s next-generation O3b mPower satellites are due to go into orbit starting in 2021.

“With this new technology and design, Boeing is able to build satellites faster and more cost-effectively while still providing the high performance our customers have come to expect from Boeing digital satellites,” Paul Rusnock, chairman and CEO of Boeing Satellite Systems International, said in an news release.

In its own news release, SES said the “super-powered” mPower satellites will have 30,000 fully shapeable and steerable beams, making it the world’s most bandwidth-efficient satellite system. The constellation is designed to provide coverage for four-fifths of Earth’s surface.

O3b is already providing satellite data services for ships at sea as well as exotic parts of the world ranging from the Democratic Republic of the Congo to the Southeast Asian nation of Timor-Leste and the Cook Islands.

The mPower initiative is part of a wave of broadband satellite services due to hit the market in the years ahead. OneWeb and SpaceX are both developing satellite systems for global internet access, and Boeing has laid out its own plan for a 1,000-satellite constellation in low Earth orbit to provide broadband data service.

SES’ plans are most directly in competition with ViaSat, which is also planning a high-throughput satellite constellation in medium Earth orbit.

Blue Origin, the space venture founded by Amazon billionaire Jeff Bezos, has a deal with OneWeb to start launching satellites on its New Glenn rocket in the 2021 time frame. SES did not announce the launch provider for the O3b mPower satellites, but it’s theoretically possible for Blue Origin to handle those launches as well.