Stacking Up High-speed Bluetooth Against Certified Wireless USB
By Mike Foley
April 2, 2007
The emergence of Certified Wireless USB and high-speed Bluetooth technology, both using the same WiMedia UWB radio, has led many to assume that one technology will dominate across all types of devices and usage scenarios, much as earlier wireless technologies, such as Wi-Fi and even today's Bluetooth wireless technology, had once been hyped as the single solution for all wireless needs.
Bluetooth technology defied the original "one-size-fits-all" hypeýand the pessimism that followedýby gaining traction in the market for which it was originally designed. Namely, mobile phones and the devices that connect to mobile phones.
Wi-Fi, too, established its own dominance in the market for which it was optimized: wireless local area networking between PCs and access points. While the marketplace did not satisfy observers' lust for decisive victory between Wi-Fi and Bluetooth technologies, it did sort out which technology is superior for each application.
Similarly, high-speed Bluetooth technology and Certified Wireless USB work best in different applications, and the marketplace will once again decide where each technology will land based on these technologies' core strengths.
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| Figure 1: Combined Bluetooth Certified Wireless USB protocol stack. |
Bluetooth: Optimized for the Mobile Environment
Bluetooth technology has firmly established itself as the short-range wireless technology of choice for mobile devices and personal area networks. Its dominance in the mobile market is set to continue.
Led by strong penetration into mobile phones, over 600 million Bluetooth enabled devices were shipped in 2006, creating an installed base of more than a billion Bluetooth units. Growth in shipments is widely predicted to continue for years to come, and by the end of the decade, manufacturers will likely be shipping more than two billion Bluetooth enabled devices every year.
With data rates of up to three megabits per second, the Bluetooth radio has proven more than adequate for applications like streaming audio and voice, image and text file transfer, printing, and input from human interface devices.
Bluetooth technology has established the model for quick and easy setup of ad-hoc personal area networks between PCs, mobile phones, headsets, cars, cameras, printers, and other portable devices.
Crucial to Bluetooth technology's success in mobile devices has been the work put into the technology's profiles, defining usage scenarios as diverse as stereo music streaming, home-patient monitoring, and dial-up networking.
The Bluetooth profiles enable a driverless model where manufacturers need only incorporate the necessary profiles into their devices to be assured of compatibility and interoperability with companion devices from any manufacturer.
This "forward compatibility" means that today's products are compatible with tomorrow's accessories, with no driver installation or updates required. The Bluetooth wireless solution is perfect for "closed boxes" such as media players, embedded automotive electronics, and many mobile phones.
Mobile phones have already taken over the role of camera, address book, and personal organizer, with digital cameras, email, and Internet browsing capabilities standard features in today's high-end phones. Handsets continue to acquire functions once reserved for dedicated portable devices, and music-capable mobile phones are forecast to outsell dedicated MP3 players within several years.
Likewise, the array of accessories that connect wirelessly to the mobile phone continues to grow. Along with today's headphones, hands-free car kits and speakers in the car, in the office, and at home, tomorrow's mobile phone will be able to connect to video screens.
According to Fiona Thomson of IMS Research, "The equipment where Bluetooth has established itself is increasingly being used to provide data-hungry applications. Where once a short-range wireless connection was used to synchronize an address book, it may now be used to synchronize part of a music collection.
"With these changes in use there was a threat that Bluetooth could be left behind, restricted to voice applications and to handset and headsets products. However, with its combination with UWB, being able to utilize the technology's high data rates has meant that Bluetooth has the potential to be more than just a voice application."
High-speed Bluetooth technology opens up new media experiences, letting the user stream video and music content stored on the mobile phone or other portable player to whatever screen and speakers are nearby.
Synchronizing music and video libraries becomes easier than ever before, with high speed Bluetooth technology allowing wireless transfer of data between media player and PC at the speed of today's wired connections.
At home, high speed Bluetooth technology will enable streaming high-definition video and "surround sound" audio from a portable media player to a home theater. The experience will be enhanced further by a screen on the TV remote control that will show "picture-in-picture" videoýor live video from a baby monitor in the next room.
In the car, video will stream from the phone to the car's built-in video screens, while digital still and video cameras will display images on the TV or computer screen, or print them directly to a photo printer.
Legacy Bluetooth Applications
To ensure that tomorrow's Bluetooth enabled devices can connect to the billion Bluetooth devices already shipped, high speed Bluetooth technology will retain the robust, power-efficient 2.4 GHz radio found in existing Bluetooth devices.
This dual-radio approach means that devices always have a low-power channel available for pairing and maintaining connections when high data throughput is not required and provides backward compatibility with the installed base of over a billion devices.
This strategy allows devices such as headsets, mice, and keyboards that require long battery life but limited data rates to continue to use the 2.4 GHz radio for low power communications, while maintaining compatibility with high speed Bluetooth devices.
Certified Wireless USB: Strengths and
Having emerged as the primary contender among a variety of technologies advertised as "wireless USB," Certified Wireless USB will assume its place as the pre-eminent wireless USB technology once qualified (or "certified") devices begin shipping in 2007.
Certified Wireless USB is backed by the organization responsible for wired USB, the USB Implementers Forum (USB-IF), and enjoys broad industry support.
Certified Wireless USB will come to market with the advantage of wired USB's proven position as the interface of choice for connecting peripherals to the PC. Early Certified Wireless USB devices will attempt to replace the cable for existing USB devices using so-called Device Wire Adapters (DWAs).
By converting a PC's USB port into a wireless USB hub, DWAs will quickly extend wireless capability to a host of USB devices, such as printers and scanners, while opening up new applications such as wireless stereo speakers for the PC. For devices that traditionally connect to the PC in a 'host-to-device configuration, Certified Wireless USB will most likely enjoy a quick market adoption.
However, as Bluetooth wireless technology has demonstrated, simply cutting the cord changes the way people use their electronic devices, and Certified Wireless USB must take these changes into account if it is to move beyond simple cable replacement into a technology that changes the way people use technology in their daily lives.
Without products available today, it is uncertain whether Certified Wireless USB will grow into product categories outside of the PC environment, USB's traditional domain.
Unlike wired USB, which was designed from the start for connections from a PC to a peripheral device, Wireless USB must accommodate so-called "dual-role" devices in situations where it is not clear which device should govern the connection.
Under Certified Wireless USB it will be possible, for example, to connect a camera directly to a printerýboth devices that would fall under the category of a peripheral when connected to a PC via wired USB.
Such devices have given rise to the need to "re-architect" USB for the wireless environment. Those who expect the switch from wired to wireless USB to be as easy as placing a radio on each end of the connection are bound to be disappointed, as issues caused by the move to wireless have made Certified Wireless USB significantly more complex than regular wired USB.
The USB protocol was designed to work in the safe confines of a cabled connection, where data packets arrive predictably and on time, and where the two devices are always in touch with one another.
By contrast, in a noisy, unpredictable radio environment, obstacles such as the loss of large chunks of data due to interference, not to mention connections that are dropped entirely, are commonplace.
Certified Wireless USB requires additional layers of complexity to handle the loss of significant amounts of data and the need to re-establish connections in a noisy RF conditions.
Usability, Pairing, and Setup
As one of the first true "plug and play" interfaces, wired USB represented a major leap forward in improving ease of use for PCs and peripherals. In the consumer's mind, wired USB possesses a brand image all wireless technologies envy: it is simple to connect, and devices "just work" with each other.
In the translation from wired to wireless, the USB-IF faces the same tradeoffs between security and ease-of-use that Bluetooth technology engineers dealt with years ago, and by the time devices come to market, the Certified Wireless USB user experience will look very similar to that of Bluetooth wireless technology.
Certified Wireless USB has adopted a similar device pairing technique: pressing a button on each device and comparing a visual indication on both devices to confirm the devices have found each other.
Consumers unfamiliar with this process face a learning curve just like they would with Bluetooth technology. The constraints imposed by operating in a wireless environment require very different user interactions as compared to the "plug and play" experience consumers have come to expect with wired USB.
In fact, to get around these constraints, proposals exist for the optional use of a wired USB connection in order to pair Certified Wireless USB devices. While simple and familiar, the wired pairing model will seem anachronistic to many consumers expecting a full wireless experience, and is impractical for the type of "ad-hoc" or "peer-to-peer" pairingsýsending a calendar appointment to a business colleague, or transferring a file from one PC to another at a meeting, for exampleýwhere Bluetooth wireless technology excels.
Meanwhile, like wired USB, Certified Wireless USB will continue to require the use of driversýsoftware installed on the PC or mobile phoneýto properly manage connections between devices. This stands in contrast to Bluetooth technology, which enables a full-featured "out-of-the-box" user experience without requiring any software installation.
There is no guarantee that Wireless USB will satisfy users who expect wired USB-like simplicity in setting up their Wireless USB products, and customers are quite unforgiving of difficult technology; according to recent data from Microsoft as quoted in PC Magazine, 30% of wireless access points are returned because customers have trouble setting up the devices.
Name and Trademark Issues
To complicate matters further, the USB-IF will face an uphill struggle to establish a brand that represents compatibility and ease of use in the customer's mind. A 2005 brand awareness study by Millward Brown revealed that nearly 30% of consumers in the UK, US, and Japan believe they already own one or more wireless USB products, even though no Certified Wireless USB devices have been shipped to date.
In reality, these devices that consumers associate with Certified Wireless USB actually represent a combination of Wi-Fi, Bluetooth technology, and other proprietary wireless devices. Thus any wireless device or adapter that plugs into a USB port is at risk of being considered "Wireless USB."
Unfortunately, the USB-IF has lost trademark control over the term "Wireless USB' and has been forced to adopt 'Certified Wireless USB" as an enforceable brand name. The Cable-Free USB and WirelessUSB brands, along with the large number of Wi-Fi and proprietary products currently marketed as "Wireless USB," have set a compatibility trap that will spring as soon as Certified Wireless USB devices start to hit the market.
None of these different but similar-sounding brands are interoperable with one another, though buyers have so far shown little ability to discern among the different technologies.
Power Requirements
One of the main benefits of UWB radio is its extremely high power efficiency: by sending so much data so quickly, the "power per bit" required is extremely low when sending large amounts of data. Unfortunately, this form of power efficiency is only useful when sending large amounts of data at a time.
For devices that spend most of the time in "sleep" or "standby" mode, the existing 2.4 GHz Bluetooth radio requires far less power than the UWB radio to maintain a connection.
Current estimates place the standby battery current drawn by the UWB radio in standby mode at 20 to 100 times greater than that of the 2.4 GHz Bluetooth radio in its standby mode.
Bluetooth enabled keyboards and mice, which only need to transmit a few bytes of data at a time with long periods of inactivity, enjoy much longer battery life than they would with a technology such as Certified Wireless USB that lacks a low-power alternate radio.
For this reason, Bluetooth technology will remain the wireless standard of choice for connecting human interface peripherals to PCs, PDAs, and mobile phones. Global Regulatory Issues The USB-IF has chosen the 3-5 GHz frequency band for Certified Wireless USB's WiMedia radio, achieving a shortened silicon development cycle but subjecting Certified Wireless USB to limited global regulatory approval.
Outside the United States, much of the spectrum below 5 GHz remains encumbered with restrictions, and in the spectrum that is allowed, costly detect-and-avoid (DAA) schemes are required to utilize the full allowed bandwidth.
In contrast, High Speed Bluetooth Technology is designed to operate above 6 GHz, where more spectrum is available around the world. The Bluetooth Special Interest Group brings its proven regulatory negotiating expertise to the table, ensuring that High Speed Bluetooth Technology is a truly global solution.
Conclusion
As has happened with today's wireless technologies, manufacturers will pick the right UWB-based wireless technology for the job, and the marketplace will put an end to the "one-size-fits-all" hype.
Built on top of the highly successful wired PC interface technology, Certified Wireless USB lets manufacturers take advantage of specialized software for their own devices, in the same way that a conventional USB printer or camera is supported by specialized software installed on the PC.
Designed to "cut the cable" for USB devices, Certified Wireless USB is a logical choice for applications that are already designed to run on the PC through a USB interface, such as printers, scanners, cameras, and other highly capable and specialized PC peripherals.
These PC-centered devices will continue to utilize the extensibility that has made USB successful, including software updates and downloadable drivers, while taking advantage of the freedom and convenience that Certified Wireless USB offers.
The choice is a different one for devices outside of the core PC/USB realm, where the requirement for software installation is a disadvantage, and where existing software development and compatibility assurance is most beneficial.
Supported by extensive software development and the standardized profiles that can be easily built into a product for instant compatibility with all varieties of companion devices, Bluetooth wireless technology is perfect for the "ecosystem" of devices built around the mobile phone, as well as the growing array of sophisticated devices in the home and office, including set-top boxes, televisions, and game consoles.
All of these devices need to support a broad range of compatible devices right out of the box, and High Speed Bluetooth Technology ensures this compatibility for today's and tomorrow's devices.
The WiMedia UWB radio opens up exciting new applications such as streaming video, bulk photo downloading, and MP3 player synchronization. Retaining the proven, highly economical 2.4 GHz Bluetooth radio as secondary channel, high-speed Bluetooth technology also ensures backwards compatibility with the one billion Bluetooth enabled devices shipped to date, while offering a low-power connectivity mode for the best possible battery life in mobile handsets, mice, keyboards, and other battery-powered devices.
Mobile phones will continue to add capabilities for both work and play through rich music and video streaming experiences, in-phone video cameras, email synchronization, and other functions already appearing in the latest high-end handsets.
In the next few years, mobile phones will be firmly established as the center of the user's on-the-go media and computing experience.
Users will continue to learn the benefits of printing from their mobile phones via Bluetooth wireless technology, while high-speed Bluetooth technology will provide the needed connectivity for the growing array of video devices centered around the mobile phone, including televisions, set-top boxes, and in-car video screens.
As IMS's Thomson elaborates, "High speed Bluetooth is optimized for different scenarios than previous Bluetooth solutions and is expected to penetrate into a growing number of portable electronic devices to provide new use cases such as transferring music to a portable digital media player, downloading a music video onto a cellular handset and streaming video.
However, high speed Bluetooth will meet head on with Certified Wireless USB (WUSB) in some applications. IMS expects high-speed Bluetooth to remain dominant in cellular handsets and WUSB to become prolific in the PC space, however, in certain portable applications such as printers and digital cameras the market will have to decide."
Meanwhile, there is another factor at work that will likely influence the market's decision: the number of individual radios in today's high-end mobile phone is increasing at a rapid and potentially unsustainable rate.
Added to today's cellular, Wi-Fi, infrared, and Bluetooth radios will be a variety of specialized radios such as Near-Field Communications (NFC) and RFID. There is only so much room for radios in a mobile phone, and manufacturers will need to pick the few that offer the best connectivity per dollar and per square centimeter of circuit board.
Bluetooth wireless technology, the solution with global regulatory approval, proven ease of use, and profile support, is the obvious choice for the mobile devicesýand the devices they connect toýtoday, tomorrow, and into the future.
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