SK Telecom will pump another $270 million into Helio, its wireless joint venture with EarthLink.

With the investment, SK Telecom will clinch greater control of the venture. Precisely how that plays out is still being negotiated, though, according to EarthLink.

Whatever success Helio is experiencing has not been enough to offset mounting losses, and EarthLink is unwilling or unable to devote more of its own money to the venture.

Helio ended August with 130,000 subscribers, according to EarthLink, which alluded to “growth and usage metrics of its core services far above industry averages in most areas.”

Helio expects to end the year with between 200,000 and 250,000 subscribers. If that goal is met, Helio’s yearly revenue will be between $140 million and $170 million, but its net loss will be between $340 million and $360 million, EarthLink said.

“We are very pleased that with SK Telecom’s funding, Helio will be able to move forward with its innovative business plan without the need for further investment by EarthLink, while continuing to allow our company to have a substantial ownership interest in Helio’s future,” said Rolla P. Huff, EarthLink president and CEO.