Wireless USB FAQ

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1 May 2009, Comments: 0

Since its introduction, USB has become the de facto standard in the personal computing industry, with billions of devices in use around the world. Wireless USB promises to expand on the legendary ease of use of traditional wired USB by extending the “plug-and-play” paradigm to an environment where the cables between the PC and devices no longer exist. In this FAQ, we will address the most common questions about Wireless USB and explain in plain English what it all means.

What is Certified Wireless USB?
Certified Wireless USB is the natural evolution and extension of the ubiquitous Universal Serial Bus (USB) protocol, first introduced in 1994.

At the heart of Certified Wireless USB is a radio technology new to the consumer space: Ultra-wideband. This high-bandwidth, low-power method of wireless data transmission enables the secure, high-speed connection required for the USB-like user experience. This radio platform, developed by the WiMedia Alliance, was chosen in 2004 to serve as the foundation for wireless USB. The official specification, released as version 1.0 in May 2005 by the Wireless USB Promoter Group, will be revised to version 1.1 sometime in 2008 and add updates for better power efficiency and support for frequencies above 6 GHz.

Certified Wireless USB was designed from the ground up to address the specific challenges of wireless communications and personal networking. It is based on an Ultra-wideband (UWB) radio system called orthogonal frequency division multiplexing (OFDM) which was created by the WiMedia Alliance expressly for wireless USB. The Wireless Promoter Group, consisting of seven companies – Intel Corporation, HP, LSI Logic, Microsoft Corporation, NEC Corporation, NXP Semiconductors, and Samsung Electronics – defined the core specification with the support of more than 100 contributing members.

This specification, called Wireless USB Specification version 1.0 (soon to be 1.1), is managed by the USB Implementers Forum (USB-IF). Certified Wireless USB includes features necessary for the long-term viability of the solution, such as radio power management, additional security features, and, the potential for the datarate to improve as Certified Wireless USB support is adopted natively by new hardware and operating system updates.

How fast is Certified Wireless USB? What is its operating range?
Real-world performance is expected to vary greatly depending on the distance required. Wireless USB is designed for optimal performance when the devices are less than 10 meters (33 ft) away from the computer. Although speeds of up to 480 Mbps are advertised, this is a theoretical maximum. It is reasonable to expect performance upwards of 50-100 Mbps at short range, with performance decreasing as distance increases. As more computing systems integrate native support for Wireless USB rather than using dongles or adapters, it is reasonable to expect performance approaching 200 Mbps and beyond.
Why might I want Certified Wireless USB?
Certified Wireless USB builds upon the consumer awareness of USB and its legendary ease of use. Similar to the impact on networking and the freedom that Wi-Fi brought to mobile internet access in the last decade, wireless USB promises a user experience with fewer cables. This means consumer electronics without the typical rat’s nest of wires, easier installation and set-up for devices in the digital home, and revolutionary new products such as wireless monitors and displays.

Apart from removing the wires from computer peripherals to make them more convenient to use, wireless USB opens up some rather interesting product opportunities. Imagine eliminating the thick cables between your display and your computer. Or streaming video to multiple displays within a room – including your 60-inch flat panel – without a video splitter and without video cables. Digital cameras would be able to store the captured images not just on large flash cards in the camera, but on much larger storage devices stored in a briefcase or in a jacket pocket. That same digital camera could then stream pictures and video to any wireless USB enabled display in the room. Because the maximum throughput of wireless USB promises to be significantly higher than the fastest Wi-Fi connections, richer and more interactive user experiences will be possible.

How does Wireless USB work?
Certified Wireless USB builds on top of the fundamental operational model of traditional wired USB. That is, wireless USB connects devices such as printers, keyboards, and storage media to the computer in a “plug-and-play” fashion, but without cables. In order to accomplish this, both new hardware adapters and new software drivers are required.

At the heart of a wireless USB system is the radio and antenna system. Certified Wireless USB employs a wireless technology called Ultra-wideband (UWB), which operates in the frequency range of 3.1 to 10.6 GHz. (For reference, 802.11 Wi-Fi networks are commonly operating at 2.4 GHz, the same frequency as some cordless phones, microwave ovens, and Bluetooth devices). One of the key advantages to a UWB system is the low power consumption (great for portable devices) and wide frequency spectrum of operation.

UWB is actually not a new technology – it was invented in the 1960s primarily for military use in secure communications and ground-penetrating radars. Mainly a technology developed under classified US government programs, UWB now enjoys much more research and development attention without classification restrictions.

The ultra-wideband radio system employed by Certified Wireless USB is different from other wireless technologies on the market because it spreads data transmission over a very wide frequency spectrum in the form of brief, low-power pulses. In short, this allows the wireless system to avoid transmission at troublesome frequencies, such as the 5 GHz range (802.11a, some cordless phones). The orthogonal frequency division multiplexing (OFDM) scheme, developed by the WiMedia Alliance and selected as the exclusive radio platform for Certified Wireless USB, allows the bit rate and signal strength of each carrier to adapt so that good channels get used more than those that hamper transmission.

Certified Wireless USB allows up to 127 devices to connect directly to the host computer. Unlike wired USB, this is possible without hubs, because there are no wires.

What hardware do I need to use WUSB? Will my existing USB peripherals still work?
Think of wireless USB as an additional way in which to connect devices to a computer. Thus, traditional USB ports are here to stay, at least for the foreseeable future. All of your current USB peripherals will still utilize the wired USB connection they always have.

Wireless USB, however, opens up a variety of new types of devices. Wireless USB hubs, or bridging devices, will allow you to plug wired USB peripherals into the hub, but the hub itself will enjoy a wireless connection to the computer. In this way, you can experience the convenience of wireless connectivity without replacing all your USB peripherals with wireless versions.

To aid in the transition from a world with only wired USB to one where Certified Wireless USB will one day be supported natively on the motherboard of new computers, the concept of Device Wire Adapters (DWA) and Host Wire Adapters (HWA) was created. HWAs are essentially “dongles” that physically connect to the computer via USB 2.0 or a laptop’s CardBus or ExpressCard interface, and provide Wireless USB host capability to any number of WUSB devices. DWAs, or “Wireless USB hubs”, allow existing wired USB devices to be used wirelessly with a WUSB host.

Over time, the industry will move towards more integrated solutions where any required hardware is built-in to the computer and adapters will not be necessary. Of course, you would need a computer so-equipped to enjoy wireless USB built-in.

Where are all the Wireless USB products?
Wireless USB products have been late in arriving, mainly due to manufacturers needing to overcome technical hurdles inherent in any new technology launch. But the wait is over, and you can expect to see numerous product announcements leading up to the Christmas season. While this is exciting for the industry as a whole, it will be a while before native hardware and driver support for Certified Wireless USB is built into computers and major operating systems. Naturally, speed, compatibility and robustness will improve in successive product generations as the technology becomes more widely adopted and manufacturers tweak, revise, and redesign their products for optimal performance.
Will Wireless USB eventually replace wired USB?
Despite rapid advancements in wireless technology through the course of the computing industry, good old wired connections still enjoy speed and some security advantages over their wireless counterparts. It is just that much more straightforward and fast to get electrons traveling nicely down a few pieces of copper than it is to transmit signals through thin air and in the presence of interference. There is simply no chance of an unwanted party connecting to your local USB storage device, for instance, when the cable is directly connected to your PC (provided your networking environment is properly secure).

Wired USB 2.0 and the new USB 3.0 (a.k.a. SuperSpeed USB) standard are not going away, but will remain the device interconnect standard of choice for the foreseeable future. The issues of speed and distance pose significant challenges to any connection standard, but are always an order of magnitude more difficult to solve in a wireless environment.

Lastly, the issue of cost will likely always favor the wired USB solution over wireless USB. Interface chips simply are less complex in a wired world, and that allows the cost of products that contain them to be lower as well. For users who don’t need the convenience and freedom that wireless USB offers, wired USB is here to stay.

What operating systems support Certified Wireless USB?
In a nutshell, all major computer operating systems are planned to support wireless USB. However, at the moment, wireless USB functionality is provided only by proprietary software drivers and is largely device-specific.

As the standard matures and subsequent releases of your favorite operating system become available, we expect native wireless USB support to be built in. Products containing DWA and DHA will utilize custom wireless USB drivers for the foreseeable future.

Microsoft has stated officially (warning: MS DOC) that Windows drivers for the Wireless Host Controllers Interface (WHCI), Host Wire Adapters (HWA) and Device Wireless Adapters (DWA) are currently in Alpha. Shipping drivers are said to be forthcoming, depending on hardware availability and other such factors, although a specific date for wide-scale availability has not been provided.

Apple has not released any information regarding Mac OS X support for Certified Wireless USB. In classic Apple fashion, they may be just playing these cards close to their chest. When some official announcement is made, you can be sure to read it here on our site.

Is Certified Wireless USB secure?
By design, Certified Wireless USB is a very secure method of data transmission. As with any wireless technology, there is the possibility for data in the air to be available to other wireless receivers in range with malicious intent. Encryption is incorporated at multiple layers of the protocol, which forces a secure relationship to be automatically negotiated between each wireless USB device and the host computer using unique keys. This type of arrangement provides an extremely high-level of security to the data link, without passwords for the user to enter or forget. Coming in the updated specification (version 1.1), first-time device association will be simplified through the use of Near Field Communication (NFC) capabilities, meaning that devices can be introduced to their computers by a touch-and-go action.

The inherent low-power nature of the ultra-wideband radios used in Certified Wireless USB also plays a factor in the security. Since the maximum range is not more than 10 metres, the threat of data being stolen or read by others is limited to those who can be situated within close proximity to the wireless USB network.

Will other wireless technologies interfere with my WUSB devices?
The wireless transmission techniques used in Certified Wireless USB promise to be some of the most robust schemes of their type in the consumer market. Interference robustness is far better than Wi-Fi. Ultra-wideband signals will not be affected by out-of-band interferers such as Wi-Fi, Bluetooth, or cordless phones, even at close proximity. The reason for this is the use of a wide frequency spectrum with extremely low power at any one given frequency (but high power spectral density) versus “narrowband” systems which occupy only a small range of dedicated bands.

UWB is very tolerant of interference from other UWB sources but equally important, will “peacefully” co-exist with other wireless networks such as Wi-Fi and not interfere with Wi-Fi operation. Put simply, the limited range of UWB will undoubtedly be more of a limitation for potential users than interference robustness.

What does the future hold for WUSB and what about those competing standards?
Over the past few years, several alternate “flavors” of wireless USB have been developed, none of which play any significant role in the market today.

The first such flavor was released by Cypress Semiconductor in 2003 and is technically the only version that can be called WirelessUSB [tm] because it is trademarked. It is a very low-speed, limited “variant” of USB that was primarily targeted as a replacement for Bluetooth. Its key application lies in the wireless connections of human interface devices (HIDs) such as mice and keyboards. It uses a proprietary 2.4 GHz radio with a datarate of only 62.5 kbps. Cypress’ WirelessUSB has very limited appeal in today’s consumer electronics and computer industry and is rarely mentioned in mass publications or on the internet.

The second flavor was pioneered by Freescale Semiconductor (formerly a division of Motorola, Inc.), trademarked “CableFree USB”, and promoted by the UWB Forum and its partners. This variant used an ultra-wideband radio technology called direct sequence (DS-UWB) and its main advantage was that it was built on top of the USB 2.0 protocol in use today. This meant that users could make a seamless transition from wired USB 2.0 or 1.1 to a CableFree wireless USB system with absolutely no changes required to the computer, operating system, or software drivers. CableFree USB was a very compelling advancement in 2005 and 2006, and was actually first to market at the Consumer Electronics Show in 2006 with the multi-award-winning Belkin CableFree USB 4-port hub. Since that time, Freescale and its CableFree USB promoters have abandoned the market, leaving only one viable solution remaining: Certified Wireless USB.

True competition for Certified Wireless USB will come primarily from Bluetooth and IEEE 802.11n (the latest and fastest variant of Wi-Fi).

Bluetooth became popular primarily for low-speed short-range personal area communications and due to its extremely low cost of implementation. It uses the massively crowded 2.4 GHz radio frequency and currently is limited to a maximum datarate of about 2.1 Mbps. Knowing that the maximum throughput would need to be able to scale higher to ensure the future viability of Bluetooth, supporters of Bluetooth selected the OFDM-UWB radio platform for future integration with Bluetooth technology. This means that future versions of Bluetooth will use very much the same wireless technology as Certified Wireless USB, with similar high data rate capabilities for multimedia applications such as video streaming. It will certainly be very interesting to see how this plays out, and whether Bluetooth and Certified Wireless USB will be able to co-exist.

802.11n (and its predecessors 802.11g/b/a), are without question the standard in wireless networking. Originally developed to address the problem of deploying Local Area Networks (LANs) without cabling, it has truly changed the face of mobile computing and is supported by every major operating system, most gaming consoles, and many mobile devices and mobile phones. In its latest iteration, 802.11n, data rates in excess of 100 Mbps are achievable at a range of up to 30m or greater. Starting a few years ago, due to the lack of any other high-speed wireless protocol, many manufacturers of digital cameras and printers proceeded to install support for 802.11 networking in order to achieve wireless data transfer. Certified Wireless USB would have been a more logical choice, but it was not ready and is still in its infancy.