Wireless USB: The Next Frontier?

by Paul Arnote (parnote)

Let's see a show of hands: who among you thinks I'm talking about 802.11 b/g/n networking adapters when I mention Wireless USB? OK … you can put your hands down. You are incorrect. What I'm referring to when I say Wireless USB is the next generation of USB connectivity with a wide assortment of computing peripherals.

Development has been underway since the original Wireless USB (nicknamed WUSB) specification came out in 2005. Amazingly, not too much has been heard about it since then (or even then), its development is somewhat behind schedule, and it has been somewhat overshadowed by the much touted USB 3.0 specification that promises to offer up to 5.0 Gbps throughput and improved power efficiency.


Wireless USB is only a seemingly natural extension of the original USB ideology, which allows users to connect with up to 127 devices, via the USB Hub Controller, by using wireless technology (via the Ultra-Wide Band, or UWB, radio platform) to wirelessly provide that USB connection with printers, cameras, scanners, mice, keyboards, external hard drives, etc. — virtually anything you would connect by way of a wired USB connection — without the rat's nest of wires that tend to clog up the rear of many users' computers. Plans are to also extend WUSB to include many common consumer electronics products, including TVs, optical disc players, music players, camcorders, mobile phones, and many other items that require a high data throughput.

In fact, WUSB devices will look like, and act like, those familiar devices that you use with a wired USB connection, except without the wires. WUSB is designed to offer up to 480 Mbps throughput with devices that are within 3 meters (10 feet) of the computer, and up to speeds of 110 Mbps with devices that are within 10 meters (approximately 33 feet). All of this is accomplished via a small, built-in antenna that is 27 mm long and only 3 mm thick.

Several companies (Agere Systems, Hewlett-Packard, Intel, Microsoft, NEC, Philips Semiconductors, and Samsung Electronics, among others) banded together to form the Wireless USB Promoter Group in 2004. And, despite the delays and being overshadowed by the much-hyped SuperSpeed USB 3.0, the WUSB standard is scalable to multi-Mbps data transmission. Some of the other hardware vendors that have signed on to support WUSB reads like a veritable who's-who in the computing world and consumer electronics. They include: ATI, nVidia, Belkin, AMD, Creative, Foxconn, Fujitsu, LG, Iomega, K-Micro, Kodak, Lexmark, Logitech, Nokia, Oki, Plextor, Sony, SanDisk, TDK, Tektronics, Texas Instruments, Epson, Buffalo, Asics, and Toshiba — among many others. There are over 100 companies that have signed on to support WUSB.


The issue of data security is addressed in the standard, and is designed to be relatively transparent to the end user. Security between the host and device adapters is accomplished one of three ways. The first way sets up the security between the host and the device via a one time cable connection between them. Simply plug in the cable between the host and the device, and they learn about one another and share a secret key. After that one time connection, the devices may then communicate wirelessly. The second way is by sharing a private, encrypted numeric key that the end user must acknowledge. The third way is by way of what's called "Near Field Communication," often referred to as NFC. Similar to RFID tags that are used in shipping containers and access badges that allow some workers access to restricted areas (like what we use at the hospital where I work), the devices use a very low-powered radio frequency to communicate with one another over very short distances, within the range of 3 to 10 cm (1 to 4 inches). The low power connections make it virtually impossible for an active attack to occur.

Power Consumption

WUSB also addresses power consumption. It is designed, from the ground up, to have exceptionally modest power needs. This will be good news for netbook and notebook users who may be running on battery power, since it won't have a significant impact on battery life. The devices require only 130-160 mWatts of power to transmit and receive data. By using Orthogonal Frequency Division Multiplexing (OFDM) modulation, or Multiband OFDM, (the same modulation used by WiFi), coupled with the UWB radio frequencies used, WUSB uses only about one-thousandth of the power of WiFi. In all fairness, WUSB has a lot less range than WiFi, so the power savings make sense.

Another thing that helps save power is that the host and device adapters go to "sleep" after a period of time when they are not being used to transmit data. The host adapter "wakes up" when it is called, and the device adapter "wakes up" when it receives an acknowledgment from the host adapter that it is being communicated with. In this manner, the adapters are not continually broadcasting, thus saving power, a precious commodity when you are running off of smallish batteries with finite amounts of power.

Continuity, Legacy, and Coexistence

WUSB is designed to take advantage of the over 2 billion USB devices that are already out there, and to coexist without conflict with those legacy devices. Backward compatibility is built in, so that applications designed to work with USB will also be able to work, seamlessly, with WUSB devices. It is also designed to coexist, peaceably, with other wireless technologies, such as WiFi, Bluetooth, Wireless 1394, and WiNet.

Since WUSB is built adhering to the current USB standards, consumers and end users can expect that seamless integration of WUSB devices with their current cache of USB devices. Just as with the current USB standard, WUSB uses the familiar "hub-n-spoke" design, and is able to address up to 127 USB devices connected to the single host.

Where's Linux in the picture?

A decade ago, when USB burst upon the scene, Linux old-timers may remember how slow Linux was to adopt the USB standard. But that was then. Today, the scene is likely to be completely different, and Linux stands to be one of the first operating systems to support and adopt any new USB standards that come along — just as Linux is expected to be one of the first to support SuperSpeed USB 3.0.

But, a decade ago, Linux did not have as broad of a user base as it does now. And, among hardware vendors, Linux is becoming the operating system of choice in which to write device drivers. The advantage is that Linux drivers won't have to be developed, since they will already exist.

The new descriptors, requests, and bitfields that will be associated with WUSB have already been rolled into the Linux kernel, and have been there since kernel version 2.6.13. Still, there's work to be done, either via device drivers or the kernel itself, to address the variable transfer rates, authentication, and packet sizes.

So, Where is it?

Believe it or not, some WUSB devices have already started to filter out to the marketplace. The wireless USB page on the USB-IF (USB Implementer's Forum) lists 120 WUSB products that have already started to hit consumer shelves. As is usual with most new technologies, you will pay a premium price for early adoption of WUSB. The current crop of WUSB devices are quite pricey. It is expected, however, as WUSB becomes more and more prevalent in the marketplace, that prices will moderate and fall to price levels similar to those of the current crop of wired USB devices. For example, you can take a gander at some of the WUSB devices offered by "Cables To Go," a cable retailer, at this web site: http://search.cablestogo.com/?N=0&Ntt=wireless+usb. You can see the full list of WUSB products that are available by going to the USB-IF Products Page.


WUSB holds the promise of making USB devices easier to use, and eliminating the rat's nest of wires that snake behind our computer desks. And, it will do this without compromising the security of data. Since the WUSB standard is scalable to be able to take advantage of future speed increases that may come down the USB pipeline — e.g., SuperSpeed USB 3.0 — WUSB stands a chance of being around for quite some time to come, once it arrives.