USB is getting a facelift through several initiatives that will provide greater freedom
and convenience for connecting all types of devices. Already the most successful interface
in PC history __ with more than two billion USB-enabled devices shipped worldwide in 2006,
according to In-Stat __ new wireless and connectivity capabilities will help USB stay in
the mainstream. Most new technologies have been in development for several years, but
products are finally hitting store shelves. USB solution providers are predicting these
advances will increase USB adoption in consumer electronics devices, further boosting USB
volumes.

Several technologies target wireless personal area networking (WPAN) and feature either
high data rates or lower power consumption, including wireless USB and low-rate WPAN.
Wireless USB provides the same functionality
and speed as high-speed USB 2.0, but without the cable. Low-rate WPAN provides wireless
connectivity for cost-sensitive, battery-operated devices with modest data transmission
requirements.

ExtremeUSB, developed by Icron Technologies,
extends USB connections well beyond the standard desktop range of five meters and can be
used with standard 802.11g radios. For those interested in connecting peripherals to each
other without an intervening PC, USB On-The-Go enables point-to-point connections between
peripherals that must share data, such as mobile phones, printers, and cameras.

Cutting the Cord

Wireless USB is a new high-rate WPAN technology
based on “ultra-wideband,” or UWB, radio technology. It lets devices exchange files at
rates up to 480Mbps at short range (typically three meters or less), matching the speed of
wired USB 2.0. Wireless USB preserves the functionality of wired USB and provides enhanced
support for streaming-media consumer electronics devices and peripherals. Networks will
also operate over a ten-meter range with a reduced data rate of 110Mbps.

This technology can help tidy up the office environment
by eliminating cables between PCs, printers, cameras, MP3 players, and external storage
devices, such as high-density drives. Since many device types already have wired USB
connections, developers can leverage software stacks as they migrate their products to
wireless USB. In the future, users can discard their collection of diverse USB cables.

The home entertainment center is accumulating
myriad devices and a tangle of wires between them. Although many consumer electronics are
USB-enabled, such as HDTVs, game consoles, and personal video recorders, a lack of
plug-n-play capability plagues stationary components. Some emerging product categories,
like the entertainment
PC, could gain better traction if device manufacturers embraced standard data connectivity
such as wireless USB.

The wireless USB certification process is well underway, and companies are announcing
their solutions. Realtek, for example, launched RTU7105, a single-chip, all-CMOS solution
supporting Certified Wireless USB Device Controller and WiMedia Logical Link Control
Protocol functionality. The chip integrates protocol adaptation layers, a media access
controller, a baseband processor,
RF transceivers, and USB2.0 and SDIO interfaces.

Laptops are being unveiled that support wireless USB, such as the ThinkPad T61p from
Lenovo, which supports ultra-wideband technology with an optional add-in card.

Long Range Wireless USB

ExtremeUSB was developed to enable USB devices in industrial and commercial
environments
where operational requirements, such as connections hundreds of meters long, exceed those
of the typical desktop PC. It is fully USB compliant and is the only USB Implementers
Forum approved extension solution.

The WiRanger is the world’s first wireless USB 2.0 hub, combining Icron’s patented
ExtremeUSB technology and an industry standard 802.11g radio, as shown in Figure 1. The
WiRanger Hub enables wireless connection of USB devices including printers, scanners,
isochronous web cams, hard drives, and MP3 players.

Low-Power Wireless Options

Two wireless technologies, Wibree and ZigBee/IEEE 802.15.4-2003, are emerging to
provide low-rate WPAN solutions in a space that has been dominated by Bluetooth (IEEE
802.15.1-2002). They target battery-operated devices, such as mobile phones and pagers,
that share relatively small amounts of data with other devices. As with Bluetooth,
these emerging wireless technologies will create new opportunities for USB dongles
needed by PCs, printers, and perhaps home entertainment systems.

In June 2007, the Nokia-led Wibree Forum announced it was merging with the Bluetooth
Special Interest Group (SIG), the body that oversees the wireless standard. Wibree is a
Nokia-developed ultra-low-power wireless
technology used for networking highly portable devices. Like Bluetooth, it operates in the
2.4GHz band, connecting devices within a ten-meter range with a data rate of 1Mbps. Some
view Wibree and Bluetooth as complementary technologies: Wibree exchanges small packets of
data and control information, and Bluetooth is well-suited for streaming and
data-intensive applications such as file transfer. Bluetooth is widely used in phones, but
Wibree may be a better solution for the smaller devices around the phone such as watches,
wireless keyboards, and gaming and sports sensors.

ZigBee is a specification for a suite of high-level communication protocols using
small, low-power digital radios based on the IEEE 802.15.4 standard with data rates of
250Kbps, 40Kbps, and 20Kbps. The ZigBee 1.0 specification
was ratified on December 14, 2004, and is available to members of the ZigBee Alliance.

Companies such as Microchip have offerings
that make it easy to design using IEEE 802.15.4 wireless networking. Microchip’s MRF24J40
is a 2.4GHz IEEE 802.15.4 RF transceiver targeted for the ZigBee protocol and proprietary
wireless protocols in RF applications that require low power. The ZENA wireless network
analyzer tool further enables development of ZigBee protocol systems using Microchip’s
devices. Microchip also developed the MiWi protocol, a free, small-footprint protocol for
customers who do not need the ZigBee protocol’s interoperability but want to use IEEE
802.15.4 transceivers in low-cost, peer-to-peer, star-and-mesh networks.

Data Rate and Distance

Developers of wireless technologies must be content with the tradeoff between data rate
and distance for their target applications. In Figure 2, UWB and IEEE 802.15.4/ZigBee are
compared to other wireless technologies. UWB supports the highest data rate, but distances
are limited to three to ten meters. IEEE 802.15.4/ZigBee has a relatively short range and
small data rate due to its use of simpler, lower-power radios that minimize power
consumption.

USB On-the-Go

The USB Implementers Forum added a supplement to the standard USB 2.0 that supports
point-to-point connectivity between peripheral devices called USB On-the-Go (OTG). This
enhancement eases the development of user-friendly features in mobile devices, such as
letting a camera communicate directly to a printer instead of using a PC as an
intermediary. Other use models are shown in Figure 3.

To maintain backward compatibility to prior USB standards, OTG still maintains host and
peripheral roles. When two peripherals are communicating, one will be the host and the
other the peripheral, initially defined by how they are cabled together. Some OTG devices
can switch roles through the host negotiation protocol without changing the cabling.

Products supporting OTG are available, including the Atmel AT90USB device, a high-end,
eight-bit AVR microcontroller. It addresses embedded applications requiring USB
connectivity in host and function modes. The AT90USB microcontroller also complies with
the USB OTG standard, allowing dual-role devices in applications operating as either host
or peripheral.

USB 3.0?

Although plans have not been announced, there is little doubt that work has begun on
the next-generation, high-speed USB specification.
Those involved are keeping a lid on developments, but many speculate that one of the next
advances is to increase the wireless
USB data rate up to 1Gbps.

With a faster USB link, some interesting use models could emerge. In his blog, Jeffrey
Foerster of Intel writes, “Looking to the future, though, there are two primary
applications
of interest which could drive the need for higher-and-higher throughputs, namely wireless
video cable replacement and rapid large-file download. In addition to video, the other
application driving the need for high-throughput radios is rapid large file `synch-n-go’.
How long would you wait to download an HD movie from a kiosk to your laptop or handset
before getting on an airplane (a 20 GByte HD movie takes about 27 minutes at 100 Mbps and
only 32 seconds at 5 Gbps speeds)? As the patience of consumers continues to shrink,
having the ability to download large files quickly becomes more important.”