WASHINGTON  The inability of most firefighters and police officers to talk to each other on their radios on Sept. 11, 2001, at the World Trade Center  one of the most vexing problems on that day nine years ago  still has not been completely resolved.

The problem, highlighted in the 9/11 Commission Report, was seen again in 2005 after Hurricanes Katrina and Rita. Public safety officers from different jurisdictions arrived at the scene of those disasters only to find that, unable to communicate with each other by radio, they had to resort to running handwritten notes between command centers.

Despite $7 billion in federal grants and other spending over the last seven years to improve the ability of public safety departments to talk to one another, most experts in such communications say that it will be years, if ever, before a single nationwide public safety radio system becomes a reality.

In the meantime, public safety and homeland security officials have patched together voice networks in some regions, including New York, that link commanders at various agencies. But the focus in Washington has turned to the development of the next generation of emergency communications, wireless broadband, which seeks to succeed where radio has failed.