At the Bluetooth Developers Conference here this week, the wireless network technology is finally coming down to earth, with device makers beginning to deploy it in large numbers but with interoperability and cost issues looming.

The past six months have seen shipments of Bluetooth components jump sharply, according to some vendors, but analysts say the technology's growing pains aren't going away yet. As more consumers start to try to use it, things may get worse before they get better, according to at least one analyst.

Bluetooth is designed for wireless data transmission at the relatively low speed of 768k bps (bits per second) over a short distance (10 meters or less). It is intended primarily for "personal area networks" that wirelessly link devices that a user carries, keeps on a desk or in a cubicle. Vendors have touted it for applications ranging from synchronizing a PDA (personal digital assistant) with a PC to controlling home appliances by remote control, but to date it has been used mostly in mobile phones and wireless headsets.

The low cost, acknowledged as a big factor in getting people to buy into Bluetooth, will be driven down further by new products at the show. Also this week, some vendors also will be introducing ways to make Bluetooth coexist with IEEE 802.11b wireless LANs, which use the same spectrum of radio frequencies at 2.4GHz.

But as vendors try to expand the applications of Bluetooth, it's hard to ensure that all Bluetooth-enabled devices can really work with each other, according to analysts and one developer who is helping vendors integrate Bluetooth into devices.

"You have this large SIG (the Bluetooth Special Interest Group) that's made up of so many vendors, and everyone's coming at this from a slightly different angle, which makes for kind of a mess," said Chris Kozup, an analyst at International Data Corp. (IDC), in Framingham, Massachusetts.

Although the Bluetooth SIG oversees the standard and sets guidelines for interoperability tests, testing is carried out by a number of different Bluetooth Qualification Boards (BQBs) around the world. In order to test new "profiles" that vendors add to give Bluetooth new capabilities, some BQBs go beyond the baseline tests, acknowledged Gerhard Heider, general manager of Philips Semiconductors NV's connectivity product line.

However, Heider defended the testing process and said it is well-prepared to test basic interoperability.

"There are a lot of profiles that aren't even finished yet, so of course they aren't interoperable yet," Heider said. When vendors do extend Bluetooth, typically they go back to the SIG and propose that the new capability be added to the standard.

"In a young technology, you will not always achieve 100 percent interoperability from day one. It's everyone's concern," Heider said.

Gartner Inc. analyst Ken Dulaney was not so sanguine.

"The broad interoperability that people really want is not delivered today," Dulaney said. This may turn off users just as consumer Bluetooth products become widely available over the next year or so. After what may amount to a beta test by early adopters, the technology finally will become viable for most consumers about two years from now, he said.

By contrast, IEEE 802.11b wireless LANs have had a smoother road because of rigorous certification by the Wireless Ethernet Compatibility Alliance (WECA), Dulaney and others said.

"The Bluetooth SIG has got to take a greater sense of responsibility," he said.

Standards are well established for baseline Bluetooth functions such as radio communication, but the BQBs are still learning how to test at a higher level, according to Seung Yi, senior software engineer at BSquare Corp., in Bellevue, Washington. BSquare helps vendors integrate different capabilities, including Bluetooth, into devices running embedded versions of Microsoft Corp. Windows.

"Now we need to start looking at the application level, because . . . the user only sees the application, so it's the weakest link," Yi said.

An emerging specification for the Java programming language may ease interoperability, Yi said. On Dec. 29, the Java community will begin a public review of a proposed specification that would allow developers to write Bluetooth-aware applications on an ad hoc basis.

As an example of how this would help users, if a consumer wanted to buy a soda from a vending machine using a Bluetooth-enabled mobile phone, the device could download client software from the vending machine that could talk to the vending machine over Bluetooth without a hitch, he said.

Solutions also are on the way for another perceived roadblock to Bluetooth. Bandspeed Inc. will unveil at the show a chip set that will detect interference in the 2.4GHz radio spectrum and make Bluetooth signals travel over unused frequencies in that band. Designed to work with a modified Bluetooth protocol stack from Open Interface North America Inc., the chip set will sidestep interference from IEEE 802.11b LANs as well as from devices such as microwave ovens and cordless phones.

Vendors are looking to less expensive components to eventually drive consumer interest in Bluetooth. Ericsson Technology Licensing AB will demonstrate at the show evaluation boards with samples of Ericsson's fourth-generation Bluetooth radio, a highly integrated component with a design that reduces by half the number of components needed to build a Bluetooth system, leading to lower cost, according to a company statement.

The critical point in cost reduction is a US$5 chip set, most vendors agree. Philips Semiconductors expects to see chip sets at that price in late 2002 or 2003, down from a price of about US$10 today, said Philips' Heider.

Inflated expectations may have tarnished Bluetooth, said Gartner's Dulaney and others who still believe the technology has a big future.

"Bluetooth is just now passing over the peak of inflated expectations," Dulaney said.

Even a man credited with pioneering Bluetooth, Ericsson Technology Licensing Chief Scientist Jaap Haartsen, in Emmen, The Netherlands, agreed in an interview Monday.

"The drum rolls surrounding Bluetooth were needed to convince the electronics makers that there is a big market for it and to get Bluetooth accepted as a standard. People were enthused about the potential and the possibilities, however there were many expectations that couldn't be realized within a certain time," Haartsen said.

"I had expected more vendor adoption by now, but it is a sign of the time. New things require investments that don't bring an immediate return. With the economic downturn, those kinds of investments are typically the first to go," he added.

The Bluetooth Developers Conference continues through Thursday.

Joris Evers, IDG News Service Amsterdam Correspondent, contributed to this story.