That's the implication from the program lineup at this week's Rawcon conference in Boston, where a paucity of Bluetooth papers adds fuel to analyst speculation that the highly touted wireless networking technology may not be able to compete with the faster 802.11b on one end and simpler, low-power alternatives on the other.

Represented by a mere two papers, Bluetooth is notable mostly by its absence from the IEEE's Rawcon technical conference, which focuses on all things wireless.

"Despite the hype and expectations, Bluetooth clearly hasn't lived up to expectations," said Craig Mathias, principal at the Farpoint Group (Ashland, Mass). "We're telling clients to not pay a whole lot [of] attention to it."

While agreeing that ditching Bluetooth is "definitely something people are thinking about," Navin Sabharwal, wireless and home networking analyst with Allied Business Intelligence Inc (Oyster Bay, NY), cautioned against writing off the technology. "There's still a lot of development happening on the Bluetooth front, so I think it's very premature to call Bluetooth dead," Sabharwal said.

Rawcon is replete with state-of-the-art presentations on all the major wireless categories. From cellular to fixed broadband wireless access to wireless local-area networks (WLANs) and ultrawideband radio, the annual conference offers its usual "all you can eat" buffet of wireless design research and implementation strategies.

Bluetooth is touched on exactly twice: in papers by teams at the National Central University in Chung-li, Taiwan, and the Georgia Institute of Technology in Atlanta. Otherwise, this one-time high-flier is a no-show.

The Georgia Tech paper describes how a complete 20dBm Bluetooth module, with integrated antenna, can be built using commercial 0.24micron CMOS and low-temperature, co-fired ceramic processes. The design uses a system-on-package approach to surpass the 0 to 4dBm power output of system-on-chip implementations.

The Taiwan group, meanwhile, will describe an integrated CMOS power amplifier and down converter for 2.4GHz Bluetooth implementations.

Arguing that Bluetooth will not cost less than the 802.11b WLAN technology that's already shipping, Mathias maintains that the window has closed on Bluetooth. "The only real advantage is power consumption - and if that's important to you, just turn the power down on the 802.11b radio," he said, pointing out that Bluetooth's 1Mbit/s performance is much lower than 802.11b's 11Mbits/s.

Cost advantage

But analyst Sabharwal countered, "I have a very hard time seeing 802.11b being integrated into cell phones and cordless headsets." He also gives Bluetooth the edge in form factor and pricing. He pointed to a 2:1 cost differential between 802.11b solutions, at $20 per chipset, and Bluetooth, at under $10.

Bluetooth was never meant to be a high-speed network connection in the realm of 802.11b, just a simple cable-replacement technology for personal-area networks (PANs). As such, its most highly touted application remains cell phones and other portable devices. However, according to Mathias, "We're getting a lot of interest now from customers looking to put 802.11b radios in cell phones to access WLANs. That sure sounds like a good idea to me."

Though Bluetooth has the advantage of an Internet Protocol-based voice component, Mathias nonetheless argued, "I don't think you need to integrate voice and data into a single architecture. People will have a voice and a data radio - with VoIP [voice-over-Internet Protocol] not taking off until 4G [fourth-generation] systems, which are still eight to 10 years away."

On the cable-replacement side for headsets, Bluetooth is under pressure from established, lower-power, lower-cost alternatives such as magnetic-field-based PAN connections. Aura Communications Inc (Wilmington, Mass), a leading developer of such devices, this month will sample its LibertyLink programmable single-chip solution for point-to-point (204.8kbit/s) and point-to-multipoint (51.2kbit/s) PAN connectivity.

Using Gaussian minimum-shift keying of a magnetic field, the device is targeting the same applications as Bluetooth: cell phone headsets, game controllers and wireless desktops. However, with a current consumption of 7 milliamps off a 2.4volt nominal supply, the LibertyLink can cater to full-duplex voice over a distance of 1 meter. The current falls to 2mA for 115kbit/s data transmission over the same distance. In standby, the current consumption drops to 120 microamps. Overall, Aura is promoting LibertyLink as a 10 to 30 times power-consumption improvement over RF solution - at a lower cost.

With 802.11b finding its way into diverse applications, many of them not anticipated by the standard's originators, the problem for designers becomes one of maintaining interoperability. To head off such issues, Greg Ennis, technical director of the Wireless Ethernet Compatibility Alliance, the representative body for 802.11b, will discuss "the backward-compatibility and interoperability challenges" in his opening keynote address at Rawcon on Monday (Aug 20).

Ennis will urge engineers designing next-generation WLAN products to avoid the temptation of stripping 802.11b features and functionality as they strive to integrate the spec into low-cost portable devices. Cutting corners in this way would compromise the very interoperability that has made the technology so successful, Ennis said.

"We're looking at MP3 players, cell phones and other devices that will have embedded WLANs." These, said Ennis, will have much different needs than the more typical print-server application of 802.11b.

Two radios

Before the integration of WLAN with everyday devices can begin, there's the practical issue to solve of how to put two radios on a cell phone - one for voice and one for data. One possibility is software-defined radios (SDRs) that can switch between the two. At Rawcon, just such an approach will be detailed by researchers from NTT's Wireless Systems Innovation Laboratory (Kanagawa, Japan). In a paper on an SDR design for cellular/ WLAN systems, researchers will describe a prototype platform that supports both the Japanese Personal Handyphone System and 802.11b radios.

The NTT designers implemented digital up- and down-conversion, filtering and other functions in FPGAs and used a low-IF front end (though the group sees direct conversion as even more promising for the front end). Though still in a raw state, the platform proved the feasibility of the design's key blocks: the DSP and the FPGA stages.

On another front, the deployment of fixed broadband wireless access (FBWA) systems has long been hampered by the issue of coverage, and the problem of non-line-of-sight (NLOS) operation remains. WJ Communications Inc (San Jose, Calif) will deliver a paper this week showing the hardware feasibility of using multiple-in, multiple-out technology to form FBWA links in excess of 50bits/s/Hz - despite severe multipath interference in NLOS environments.

To date, spectral efficiencies of only 4bits/s/Hz have been proven. "Ours is still very much an experimental prototype," said Max Montone, head of advanced wireless development at WJ and author of the Rawcon paper. "But it's still an industry first."

As operating frequencies go above 10GHz, NLOS becomes an increasingly intractable problem due to the very physics of signal propagation. As a result, FBWA has traditionally been relegated to high-speed point-to-point connections. To allow for greater coverage, distributed mesh networks have become an exciting alternative. KDDI's R&D Laboratories Inc in Japan will be describing its version of a mesh approach at Rawcon.

"Mesh networks base their entire concept on one node being handed over to the next, which I consider dangerous," said Dieter Scherer, an independent consultant in FBWA. Service providers are "quite coy about how to do frequency reuse as their customer base rises." Scherer will describe at Rawcon a repeater alternative with a lower barrier to entry than traditional basestations or mesh nodes.

Scherer brushes aside the travails of local multipoint distribution service as a blip in FBWA's uptake. "I agree it's down now, but wait five years. Fibre to the curb will not be able to compete with fixed wireless - that's my conviction," he said.

Ultrawideband awaits approval

Another technology waiting to take off is ultrawideband. Touted as the solution for everything from radar to car safety to wireless networking, the technology is awaiting approval from the Federal Communications Commission, though some applications have been given the go-ahead. The FCC's Office of Engineering and Technology will submit its guidelines for the remaining applications, including communications, by year's end.

Ultrawideband spreads its signal - albeit at low power - across a swath of frequencies ranging from dc to 3GHz, cutting right across the global positioning system and personal communications system (PCS) bands. While promoters claim the technology's low power means it won't interfere with those bands - and two papers at Rawcon delve into that theory - Farpoint's Mathias says they're missing the point.

"If you've bought spectrum licences, say 30MHz in the PCS band, you're going to exclusively licence that territory," he said. "The UWB [ultrawideband] guys are going to be competing with them directly, so having spent millions of dollars for that spectrum, [the licence holders] are going to fight the UWB guys and take them straight to court - along with the FCC."