In perhaps the longest courtship in telecom history, T-Mobile US and Sprint announced today that they will merge and form a 5G powerhouse. The all-stock deal would combine Sprint, which has a market value of $26 billion, with T-Mobile, which has a market value of $55 billion, based on Friday’s closing prices. The companies said the deal represents a total implied enterprise value of $146 billion for the combined company.

The two companies have talked about merging a number of times in the past several years. Under the Obama Administration the deal was halted because of concerns that regulators wouldn’t approve it. And more recently, plans were put on hold after there were reportedly disagreements over who would control the company.

The all-stock deal will give Sprint shareholders 0.10256 T-Mobile shares for each Sprint share they own. The new company will use the T-Mobile name and current T-Mobile CEO John Legere will head up the new firm. Mike Sievert, currently COO of T-Mobile, will be president and COO of the combined company. T-Mobile Chairman Tim Hottges will serve as chairman of the board of the new company.

T-Mobile’s majority shareholder Deutsche Telekom will own about 42 percent of the combined firm, while SoftBank, which has a controlling interest in Sprint, will own 27 percent of the company.

The proposed merger will likely face an uphill battle with regulators. The Justice Department sued AT&T in November to block its $85 billion takeover of Time Warner Inc. That trial is currently underway.

And in 2011 AT&T announced plans to purchase T-Mobile but then changed course once regulators signaled that they wouldn’t approve the deal.

Sprint and T-Mobile are positioning this merger as a necessary step for 5G. The two companies said that they plan to invest up to $40 billion in a new 5G network.

In addition, the two companies will combine Sprint’s wide swath of 2.5 GHz spectrum with T-Mobile’s nationwide 600 MHz spectrum and other assets to build a 5G network that will have much deeper coverage than either could do alone.

Prior to the merger, Sprint had said that it would launch a 5G network in 2019 using its 2.5 GHz spectrum. Likewise, T-Mobile said it would begin to launch its mobile 5G deployment in 2019 using the company’s 600 MHz spectrum.

If the merger is approved, it’s unclear who will be the CTO of the new T-Mobile. In a news release about the merger, the companies said that the remaining members of the new management team would be selected from both companies during the closing period.

Sprint has definitely been more vocal about its participation in open source groups than T-Mobile.

In an interview with SDxCentral earlier this year, Ron Marquardt, vice president of technology at Sprint, said when it comes to 5G he believed that the network core will be key. “What we need is network architects to think like software architects so we can manage the complexity,” he said.

Sprint also was behind the C3PO open source project, teaming with Intel to develop a more flexible and scalable 5G control plane.