Wireless USB

USB has become one of the favored ways to hook up peripherals to PCs. We never cease to be amazed at some of the devices that you can put on a USB bus, everything from keyboards and mice to digital microscopes to scanners, printers, cameras, and more.

Sometimes people get darn silly about USB, using it to recharge AA batteries, power a little fan or light for a laptop. If your PC is like ours, your USB bus is a busy place. USB has gone through two major standard revisions, version 1.1 and version 2.

Version 2 is almost always backward-compatible with version 1.1, and both standards are supported by all the current versions of Windows in the OS. The major difference between the two versions is the throughput; version 1.1 is slow at 12 Mbps, while version 2 runs at 480 Mbps.

The original lowspeed devices ran at 1.5 Mbps per channel. The upshot of all of this is that low speed USB devices are better supported for wireless connections than high speed devices can be. Most high speed devices need to be plugged directly into a port or a USB hub to work with wireless networking devices.

No doubt you’ve encountered wireless adapters or dongles that are used to connect a computer to a wireless keyboard and to a wireless mouse. A wireless dongle serves the same function for connected wireless devices as the USB host adapter serves for its connected devices.

Most USB wireless connectors that are designed to meet the USB Human Interface Device (HID) standard have a 15- device connection limit. So there’s also a 15-device limit to wireless USB host adapters and hubs.

What the USB HID standard says is that any compatible wireless host adapter or hub must support plug and play, power management, persistent addressing, and be capable of being woken up from sleep.

Part of the USB addressing scheme maintains both the serial numbers and port addresses of connected devices, the former being the default means of recognition. In terms of what that means to you, when you plug in a USB device it should be recognized and automatically configured.

If the operating system realizes that the device is unknown or that it doesn’t have the proper driver to control the device, then the OS will either search for the driver or ask you to supply the driver file manually. USB is one of the best examples of Plug and Play (PnP) in action, and wireless USB extends this convenience to even more devices.

There are three different kinds of wireless connections to USB devices currently in use:

  • Devices that turn a USB port into a wireless NIC.
  • USB devices that allow a direct connection between the peripheral (when it has a transceiver of its own) and the access point.
  • A wireless USB hub that you can plug other non-wireless USB devices into.

In the first option, there are many examples of devices that can convert a USB port into a wireless NIC card. Most of these devices, like the Linksys WUSB12, have a form factor similar to a keychain USB flash drive and are 802.11b devices. More recently 802.11g USB adapters have begun to appear.

Buffalo Technology’s WLI-USB-G54 Airstation is a wireless USB 2.0 device that retails for anywhere from $30 to $70, while the Linksys WUSB54G is a nearly identical device. USB wireless G adapters offer fast throughput without any USB penalty.

Not surprisingly, you’ll also find that vendors offer combination wireless USB/32 MB flash storage drive adapters, like the SMC WUSB32—EZ Connect for $65. If you need to add an IrDA capability to a computer, check out the USB 1.1 IrDA adapters s from CP Technologies, a $30 device.

There are several examples of wireless USB hubs on the market. Take for example the AnywhereUSB hub from Digi. This hub lets you connect USB devices to either a LAN or a WLAN without a computer to manage the process.

Digi calls this USB over IP technology, but somewhere on the network is a computer or server that has the necessary drivers to do the translation. The USB/5 (5 USB ports) has the same characteristics as any USB hub for PnP, and enables you to connect devices such as a bar code reader, a fingerprint scanner, or a portable display.

Digi also sells a line of USB sensors called Watchport that can measure things like temperature, as well as a USB camera, and the Edgeport USB to serial converter devices. So with the AnywhereUSB system you can remotely place USB peripherals. Figure below shows a picture of the AnywhereUSB wireless hub.

Digi AnywhereUSB wireless hub.Other examples of wireless USB hubs include one from a company called Silex. They offer a single port wireless USB 2.0 hub for a high speed printer, scanner, or storage device connection, model SX-3700WB.

Pricom’s SX-5000U2 can serve as a four port USB hub and print server, and when you attach another USB hub to one of the SX-5000U2’s ports you can fan out (from one port to many) up to nine USB 2.0 devices.

These two devices connect using the 802.11b standard. The SX-5000U2 is more than just a simple wireless USB hub. It comes with software to convert a multifunction printer and a scanner into a shared network resource.

There’s support for HP JetAdmin and Web JetAdmin management software, printer status notification, as well as automated e-mail printing. To set up printers and other devices on the SX-5000U2 you would create the configuration on your computer and then copy the settings to a USB pen drive (supplied with the product).

You then take the pen drive to the location of the wireless USB hub/server, insert it, and configuration is complete. Security features of the 5000U2 include IP filtering, and it will also support IPv6 addressing.

There are efforts underway to develop Wireless USB (WUSB) for high speed transfers up to the current 480 Mbps USB limit using ultra-wideband (UWB) and multiband technologies, and longer range plans suggest it might be possible to reach 1 Gbps.

WUSB is a hub and spoke network with the host initiating data traffic to client devices, directing traffic, and time slicing the bandwidth among what is called its cluster. Each cluster of WUSB has a 127-device limit and two or more clusters can use the same radio cell (reception area for a signal).

This high speed is possible for a relatively low powered bus because the typical device connection is meant to be less than 30 feet or 10 meters. That will make a WUSB bubble about the same size as Bluetooth’s. An article on the emerging WUSB standard may be found at Intel.com.