Mobile networks hit speed bumps

By Bob Brewin, Computerworld |  Networking

Don't count on actually obtaining the maximum advertised speed from much-ballyhooed advanced mobile wireless networks when they're rolled out later this year.

That's the message from large enterprise wireless users, network equipment providers, analysts and the carriers themselves. Carriers acknowledged last week that the average throughput on third-generation mobile wireless networks will be in the range of only one-third to one-half of the peak speeds they hyped in announcements at the recent annual Cellular Telecommunications & Internet Association conference in Las Vegas.

Though the carriers had boasted raw speeds for 3G networks starting at 144K bit/sec. this year, with speeds reaching 2M to 3M bit/sec. in the 2004 time frame, Verizon Wireless in Bedminster, N.J., said that in tests, throughput averaged only 50K bit/sec. on its 144K bit/sec. service.

Verizon spokeswoman Andrea Linsky said that when the company rolls out a 2.4M bit/sec. service next year, speeds will average "500K bit/sec. in a mobile environment, and you'll only get 2.4M bit/sec. in a fixed environment."

These speeds are also application-dependent, Linsky said, meaning that when a user downloads a fat file, throughput should increase. "When you need the speed, you'll get it," she said.

Randy Roy, vice president of network systems at FedEx Corp. in Memphis, said wireless network users need to consider average speeds rather than "raw channel speeds."

Roy said he expects that the 144K bit/sec. networks will average 50K to 70K bit/sec. Although it's much slower than the peak speeds touted by the carriers, this range "is still significantly higher than the networks that exist today," he said. "Our private [wireless network] averages 9.6K [bit/sec.]."

The 144K bit/sec. peak speed cited by the carriers "is the speed of a single packet under optimum conditions," said Ken Dulaney, an analyst at Gartner Inc. in Stamford, Conn. "We expect most 3G technologies to provide somewhere between 28K bit/sec. and 64K bit/sec." But, he added, "because we are trying to match speeds obtained under the wired circuit-switched system to wireless packet, it's a very, very rough guess."

Tom Crook, director of technology research and development at Sprint PCS Group in Kansas City, Mo., said the tests his company has run show an average throughput "in the 60K to 70K bit/sec. range" on the 144K bit/sec. service it plans to introduce this year.

"That's the nature of [radio frequency] networks," Crook said. "The signal gets weaker the farther away you get from a cell tower." A user closer to the tower will obtain higher average speeds than a user at the edge of a cell site, he explained.

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