Sprint said today it will launch its new CDMA-based push-to-talk service on Sunday as it works to phase out its iDEN network, which has been losing customers for years.

The company is keeping mum on a report from CNET that it will launch its own LTE network early next year on reallocated G-block spectrum from the iDEN shutdown.

Sprint plans to make a major announcement about its network on Oct. 7 and it is also rumored the company may get the iPhone during the same month. The deployment of its own LTE network would free Sprint from its sometimes contentious relationship with Clearwire, which it currently depends on for mobile broadband service.

Sprint’s iDEN-based Nextel brand, known for its walkie-talkie-like features, will be completely supplanted by the new CDMA-based Direct Connect service in 2013, the operator said when it first announced the plans in March. Direct Connect’s coverage will match Sprint’s CDMA voice footprint by early next year. Direct Connect’s footprint will eventually be double that of its iDEN predecessor.

“Our customers are asking for broadband and push-to-talk,” said Paget Alves, president of Sprint Business, in a statement. “We’ve seen steadily increasing demand for faster data speeds, better and broader coverage, and more applications on push-to-talk devices. Sprint Direct Connect is designed to solve for all three.”

The upgraded PTT service will offer new capabilities like group push-to-talk for up to 200 participants, interoperability with Land Mobile Radio and notifications on a user’s availability. International push-to-talk and other features will be added early next year.

Sprint is launching the service on the Kyocera DuraMax and plans to come out with the Kyocera DuraCore and an Android-based Motorola smartphone sometime in the fourth quarter. The DuraMax is a ruggedized device with a 2-inch display and 3.2-megapixel camera. It will hit shelves on Oct. 2 and costs $70 after a mail-in rebate and two-year contract.