FCC chairman Tom Wheeler on Friday said that the agency’s goal for an auction of broadcast spectrum for wireless use is now the middle of 2015.

The agency had previously indicated that the incentive auction would be conducted by the end of 2014. Broadcasters had questioned whether they would be ready in time, particularly with a host of issues that remain to be resolved.

In a blog post, Wheeler said that “managing a complex undertaking such as this also requires an ongoing commitment to continuously and honestly assess its readiness and its project plan.”

With ever-increasing demand for spectrum for wireless use, the auction calls for broadcast stations to voluntarily give up spectrum and then share in the proceeds when it is put up for bid to mobile and telecom firms. Success of the auction, however, depends on a number of factors, including the complex design of the software. Earlier this week, Wheeler said that he was mindful of what happened to healthcare.gov in the rollout of the Affordable Care Act.

“I have often defined the complexity of this multipart simultaneous process as being like a Rubik’s cube,” Wheeler wrote. “As part of our auction system development, we will check and recheck the auction software and system components against the auction requirements, and under a variety of scenarios replicating real life conditions. “

He said that they plan to hold several software demonstrations as well as a “mock auction” “to ensure the software and system performance.” Further details of the timeline are set to be unveiled next month.

“Only when our software and systems are technically ready, user friendly, and thoroughly tested, will we start the auction,” he wrote.

Stations also are concerned that the FCC’s plans for “repacking” — in which some outlets will be moved elsewhere in the channel lineup — will degrade their broadcast signal. Also being worked out are agreements to ensure coverage for stations in market border areas with Canada and Mexico.

“First and foremost, we absolutely must make fact-based policy decisions in an open and transparent manner,” Wheeler wrote. “Beyond the policy issues, however, we must also exhaustively test the operating systems and the software necessary to conduct the world’s first-of-a kind incentive auction. This includes ensuring that such systems are user-friendly to both broadcasters and wireless carriers who will participate.”

Gordon Smith, president and CEO or the National Assn. of Broadcasters, said that the trade org “appreciates” the new timeline.

“As NAB has long maintained, given the complexity of the auction and its many moving parts, the most important goal is to get the auction done right,” he said in a statement.