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SAN JOSE – While King Harald Bluetooth unified much of Scandinavia, the technology named after him still hasnt learned how to play nice.
After five years of development, Bluetooth technology providers sought to establish the nascent technologys potential at the Bluetooth Developer Conference here this week. To reach it, the technology will have to learn to interoperate with the 802.11 WiFi protocols which share the same frequency.
According to analyst firm the Zelos Group, by 2006 adoption and sales of Bluetooth wireless technology will result in $2.6 billion of incremental revenue for mobile operators in the US. But Bluetooth, the wireless technology that enables cable less connection of devices like PDAs, mobile phones and laptops, also shares the 2.4-GHz frequency spectrum with WiFi.
Consider a user who owns an 802.11-enabled laptop, a handheld PDA using Bluetooth and a wireless cell phone using either technology, executives said. If a user receives a call on the cell phone, will he be able to answer it and not affect the operation of the laptop and PDA? In most cases, the answer would be no: the user would either have cell phone connectivity or laptop connectivity, not both.
Coexistence essential
But is coexistence as important as it is made out to be? Joel Linsky of Silicon Wave believes it is. “We see coexistence issues slowing the adoption of Bluetooth over 802.11b,” he said.
Toshiba is very concerned about the coexistence of wireless technology. “There are so many wireless products competing in the market place,” said Robert Graham, a principal wireless engineer at Toshiba. “Were putting wireless in washing machines, notebooks, NASA astronauts are trying wireless to communicate with ground stations. In fact, we have introduced Wi-Fi into a mix of Bluetooth products to see what interference issues pop up.”
While most companies try to come up with products that are compatible with both technologies, differences inevitably arise. 802.11b is better at transmitting data – up to 100 feet instead of just a few feet with Bluetooth. At 11-Mbits/s, the technology whips past Bluetooths 100-300 Kbit/s data rates. But Wi-Fi chips are power hungry and less practical when used for handheld devices like PDAs and cell phones, according to Nick Hunn, managing director of TDK.
“The prime difference between 802.11 and Bluetooth is that 802.11 replaces one cable while Bluetooth replaces any cable and can connect everything from a digital camera to laptop to mouse,” Hunn said. “Yes, it doesnt have high speed. But when you are traveling you dont need to carry lots of cables with you because Bluetooth replaces all of them.”
Microwave ovens run at the 2.4-GHz frequency, as do plasma lighting systems. All of this generates a surprising amount of interference in the 2.4-GHz frequency band. This has contributed to some of the fears satellite radios have had over the adoption of Bluetooth and Wi-Fi, executives acknowledged.
“IT departments are already banning Bluetooth to prevent it from interfering with Wireless LAN,” Graham said. “Bluetooth is definitely a threat to them. But hey, even microwave ovens generate more interference.”
Arguments like these seek to promote Bluetooth technology over Wi-Fi. While it is true that Wi-Fi has not been able to address either cost or power consumption as well as Bluetooth, Graham from Toshiba thinks both technologies first have to resolve the interference problem in the 2.4-GHz band.
Merged Bluetooth
/WiFi chips, or not?”>
“I dont see a merge here. Youll continue to see what we have right now – device to device connectivity with each device choosing the technology to use depending on what it needs,” Graham said.
The problem is that many communications chip manufacturers do see a design path toward a merged Bluetooth/802.11 capable chip. While there are several potential design methods, all assume Bluetooth and 802.11 antennae will be in close proximity, almost assuring interference. Furthermore, upon encountering interference, an 802.11 transceiver lowers its data rate to ensure fidelity; “exactly the wrong thing to do, as it increases the problem of interference,” said Tim Godfrey, strategic marketing manager at Intersil.
The 1.2 version of the Bluetooth specification, due next year, will support adaptive frequency hopping. Bluetooth radios with AFH will survey the frequency band for potential sources of interference, such as a channel on which an 802.11b wireless network is operating, and exclude the channel from its pseudo-random hopping pattern.
“Once 802.11b is switched on, Bluetooth can be smart enough to figure that out and hop out of the bandwidth,” Godfrey said. “This opens up a new world of coexistence with a bunch of products buying out of the same band.”
The spec will account for a mix of AFH-less 1.1 Bluetooth devices and the newer 1.2 products, potentially leading to a complicated mix of hopping patterns and timings, said Joel Linsky, a senior Bluetooth design architect for Silicon Wave and a member of the 802.11 Coexistence working group.
Silicon Wave has worked with Intersil and Intel to address the coexistence issue with Blue802 – an example of proprietary coexistence technology, that enables Bluetooth applications such as mouse, keyboard, printing and file transfer to take place at the same time the user is connected to the network over 802.11b.
While other proposed solutions, such as Alternating Wireless Mechanism Access (AWMA) and Packet Traffic Arbitration either multiplex the Bluetooth and 802.11 signals or ask the Media Access Controller to act as a “traffic cop” between the two, Blue802 simply uses the 802.11 chips power-saving mode to switch the 802.11 portion on and off. Blue802 effectively shares bandwidth by only having one component in operation at one time, Intersils Godfrey said. While the technology has been out since April, the chipset is not yet available in full production.
Alternative solutions
“Alternative” Bluetooth solutions are also beginning to crop up. Some Bluetooth proponents have sought to address power consumption issues by aligning itself with Zigbee, a technology involving low data rate and low power consumption wireless networking.
The alliance created the 802.15.4 standard, dubbing Zigbee the commercial name. Zigbee has a very long battery life and 802.15.4 link rates, and is powered by a primary rechargeable cell. Want a wireless “Clapper”? ZigBee could be the basis for it.
“In contrast, Bluetooth requires an adapter to be recharged in the night. I can see a lot of application spaces opening up for Bluetooth and Zigbee combination technology – in industrial control systems, sensor nets and medical applications,” TDKs Hunn said.
On the other hand, WiMedia was designed for short-range multimedia solutions. “No previous multimedia standard was optimized for wireless,” Bob Heile, chairman of the IEEE 802.15.2, Co-existence task groups and chief technical officer at Appairent Technologies.
The WiMedia draft standard calls for 55 Mbits/s in an unlicensed 2.4-GHz unlicensed band, over about a 50-meter distance, he said.
The WiMedia Alliance consists of Appairent Technologies, Inc.; Eastman Kodak Company; HP; Motorola, Inc.; Royal Philips Electronics; Samsung Electronics Co. Ltd.; Sharp Laboratories of America, Inc.; Time Domain Corporation; and XtremeSpectrum, Inc.
The adoption of Bluetooth technology is also dependent on the availability of compelling solutions to users needs. Widespread adoption would have to go beyond the coolness factor – the “look what Ive got” appeal that Bluetooth providers highlight in customer handouts.
Success will boil down to market dynamics: what works and what doesnt will depend on cost. “Wi-Fi is cheaper in the short term,” Heile said. “But in the long term it is cheaper to implement Bluetooth because currently you can put more products into the range without affecting your power supply. With PDAs on Wi-Fis you get huge battery costs. Also, in the long term, implementation of technology gets cheaper for Bluetooth because so many companies are continuing research.”
