Wi-Fi Weds Bluetooth

It was inevitable. As connectivity has continued its evolution of putting more functions in a single box, the pairing of more than one popular wireless technology into a single device was just a matter of time.

That's why companies are now putting Wi-Fi and Bluetooth together into handhelds

such as smartphones and PDAs.  But while this marriage may seem like a dream come true for consumers, as demonstrated by the popularity of the combo in the consumer market, it's proven to be a challenge for OEMs and chipmakers faced with the task of getting these star-crossed lovers to work together.

That's because both technologies work on the 2.4GHz frequency. The industry sought to address this challenge with the Bluetooth 1.2 specification, which defines a mechanism called adaptive frequency hopping that allows Bluetooth to "hop" around the wireless LAN in use.

"If there is a collision, the Bluetooth device identifies the collision and removes the offending frequency from the hopping sequence," Paul Marino, Philips VP and GM of Connectivity of Semiconductors, told Electronic News. "Coexistence in itself is addressed by the standard."

Philips, one of the companies offering a combined Wi-Fi/Bluetooth technology, developed specialized hardware and software that are embedded in its WLAN and Bluetooth system-in-a-package (SiP), dubbed BGW200, to further work around coexistence issues.

Another problem with the combined wireless technology is co-location, an issue that comes up if two devices in the neighborhood of each other are oppositely transmitting and receiving. So far the industry has not standardized on a way to address this, Marino said, noting that Philips uses packet traffic arbitration to identify a conflict and arbitrate.

"It's not only about having them exist together," he said, "but also making sure that in protecting them from one another one does not negatively affect the throughput."

Broadcom, another connectivity player stepping up to the challenge, describes the issue as one of noise.

"When you put both wireless LAN and Bluetooth inside a small box and they are both transmitting, the wireless LAN transmitter transmits very high power against the Bluetooth one. When the wireless LAN is transmitting, it pretty much could saturate the transceiver so that you can't hear anything on the Bluetooth side. That's called in-band interference," Scott Bibaud, Broadcom's director of marketing for Bluetooth products, said.

Broadcom's answer? Their InConcert collaborative code system, a hardware/software technology that allows "intelligent sharing" of the 2.4GHz frequency range, synchronizing transmissions to maximize throughput and performance for both standards. "Not only do they not interfere with each other, we can also negotiate between the Bluetooth and wireless devices who has the higher priority for transmission," Bibaud said.

Still, with all its faults, this marriage is worth fighting for, according to IDC. The market research firm found that in 2003 -- a year that saw handheld shipments slip about 10 percent -- Hewlett-Packard experienced 101.5 percent year-over-year growth in that segment. HP's stellar growth was due in large part to its HP iPAQ 4150, which combines both Bluetooth and wireless LAN capability, IDC said. "The market for converged mobile devices, which will surpass 20 million units in 2004, has demonstrated strong growth potential as consumers continue to show interest in improved devices combining data and telephony capabilities," David Linsalata, an analyst at the firm, recently reported. "This growth will be driven by evolutions in form factor, pricing and power consumption."