Softbank's massive investment in Sprint has renewed analyst speculation about the transaction's implications for Clearwire.

Sprint is Clearwire's largest shareholder, and the two companies are closely connected on mobile broadband services.

The $20.1 billion transaction between Sprint and Softbank announced early this morning did not address the relationship with Clearwire beyond saying that the deal "does not require Sprint to take any actions involving Clearwire."

Even though Softbank has not indicated its investment in Sprint will eventually extend to Clearwire, shares of Clearwire soared more than 26 percent in morning trading on investor optimism that Softbank was also targeting the WiMAX operator.

"We believe that Softbank's deep-pocketed, visionary leader Son may be the white knight that [Clearwire’s management] and holders have been looking for in their negotiations with cash-strapped 49.6 percent shareholder Sprint," Macquarie Research analysts Kevin Smithen and Zach Smithen said in research notes, referring to Softbank CEO Masayoshi Son.

Just what a potential Softbank stake in Clearwire would look like is unclear. Some speculated that Softbank would condition its investment in Sprint on the operator gaining full control over Clearwire, but that provision was not listed in today’s announcement.

Others expect Softbank to wait until it closes the Sprint deal before making a move on Clearwire.

An intervention from Softbank could allow Sprint to benefit from Clearwire's substantial spectrum holdings, which range between 120 MHz and 150 MHz in its markets, said BTIG Research analyst Walter Piecyk.

"What could truly differentiate Sprint would be the deployment of TDD-LTE networks on Clearwire’s spectrum in the top 35 markets, which are home to 125 million Americans," Piecyk said in a research note. "The speeds from a well-built TDD-LTE network, with that much spectrum, could materially outpace what Verizon and AT&T are offering in the market today, or even three years from now."

Rumors circulated last week that Softbank would follow its investment in Sprint with a stake in Clearwire.

The talk was fueled by both Sprint’s connection to Clearwire and the fact that both Softbank and Clearwire are deploying TD-LTE in the 2.5 GHz and 2.6 GHz bands.

Sprint is Clearwire's primary wholesale customer for its WiMAX network, and although Sprint plans to phase out its use of WiMAX, it is already signed up for wholesale access to Clearwire's TD-LTE service to supplement its own FDD-LTE network.

Clearwire plans to have the first 5,000 cell sites for its TD-LTE network installed by the end of next June, eventually overlaying 8,000 of its WiMAX cell sites with the service.

The operator said earlier this month that it may delay a portion of the build but did not specify which phase of the deployment would be affected.