Cellular and other communication services are gradually improving in the Gulf Coast region more than three days after Hurricane Katrina blasted through, but service providers said Friday they still can"t reach equipment in the flooded city of New Orleans to make needed repairs.

Officials at Cingular Wireless LLC, Verizon Wireless, Sprint Corp. and BellSouth Corp. reported separately at noon on Friday that with flooding and power outages in New Orleans, crews can"t access cellular sites and switching stations for repairs. Sprint"s crews are waiting in Baton Rouge, La., until officials say it"s safe to enter New Orleans, a spokesman said.

Telecommunications have improved, however, in places such as Baton Rouge, Mobile, Ala. and Pensacola, Fla., company spokesmen said in separate interviews.

The carriers are all relying on backup generators and in some cases portable generators and cellular transceivers carried on panel trucks. When possible, the carriers are also increasing power to rooftop cell sites in New Orleans to boost signals, the spokesmen said.

Despite a massive effort with thousands of repair workers on the scene, the situation is obviously difficult, said Jeff Kagan, an independent telecommunications analyst in Atlanta. "All the carriers are still in survival mode," he said. "Some cities are better than others, but it is all one big mess.

"I think it will be a long time before we can determine how each carrier is doing, but it will not be easy," Kagan said. "This is much worse than the 9/11 emergency. It is not just a part of a city like New York. It is the entire Southeast that has been devastated.

"You have to be able to run repair trucks, but first you have to clear the streets," he continued.

"Some areas can be repaired quickly, and other areas will take weeks and months. It is not pretty, but the carriers are working hard to get service back up and running."

Only a small portion of a cellular call is carried over a wireless link, with cell sites usually connected to the rest of a network through T1 or fiber-optic connections, the spokesmen said.

"Flooding has its most dramatic effect on land lines, such as T1s and fiber," said Verizon spokesman Patrick Kimball. "It"s still a very difficult situation" in New Orleans.

Where there is service, even in restored areas, network congestion is high, and land-line users have heard "all circuits are busy" or a fast busy signal, Bill Oliver, BellSouth"s president of Lousiana operations, said in a statement. The wireless providers urged callers to use text messaging as an alternative to voice calls, partly because it requires less bandwidth.

None of the carriers could predict when service will resume, but Oliver said "key fiber breaks" in southeastern Louisiana will take more resources to repair. Of about 1 million landline phones in Lousiana that were out of service after the deadly storm hit on Monday, only 130,000 have been restored so far, Oliver said.

Various reports from New Orleans tell of desperate survivors offering to pay strangers to use a cell phone to reach family and friends.

Meanwhile, a few companies in the Gulf Coast region set up communications backup plans in advance of Katrina, which has left hundreds, perhaps thousands, of people dead.

For example, Siemens Enterprise Networks is working with a power utility in Mississippi that has been sending repair crews into the field with voice-over-Internet Protocol (VoIP) phones to make wireless calls via a satellite network, said Tim Perez, a Siemens director of sales. He wouldn"t identify the utility, but said the system has been the main means of voice communications for utility crew supervisors in the field, supplemented by Research In Motion Ltd. BlackBerry handhelds for e-mail access.

In this case, Siemens acted as integrator to arrange for satellite network bandwidth, allowing the users to connect to a Siemens IP-based voice switch in Atlanta. With the Siemens VoIP phones, the workers can make five-digit calls over a familiar device to co-workers without needing special codes for the satellite links, Perez said.

"It provides business as close-to-usual under very unusual circumstances," he said.

All of the wireless carriers in the region have supplied thousands of cell phones to be used by relief workers and emergency personnel. Even so, the cell phones are only as good as the network that supports them, said Jack Gold, an independent wireless industry analyst based in Westboro, Mass.

"When stuff"s under water, electrical stuff doesn"t work," he said. "Fundamentally, you are still dealing with the laws of physics."

Gold said emergency personnel and utility workers from hundreds of different groups face the same lack of radio interoperability with their private system emergency radios that has plagued police and fire departments for decades. The hurricane and the resulting flooding are another reminder that "we"re not moving fast enough" to create emergency radio interoperability for responding to homeland security and natural disaster emergencies.

"There"s a lot of work to be done with radio interoperability, since we have 80 years of private radio networks as an installed base," he said. Gold noted that Austin and its suburbs, as well as some communities in California, are working together to find common radios. But most municipalities don"t have the funds to abandon their systems.

A number of small companies is offering portable mesh networks that work over Wi-Fi and can be driven to disasters on short notice to provide a common IP platform so utilities, police, fire and other officials have interoperable communications, Gold said. "One universal IP network would help, but how you coordinate that is the problem," he said.