An Analysis of Wireless Device Implementations
on Universal Serial Bus
Universal Serial Bus (USB) is a new personal computer (PC) interconnect that can support simultaneous
attachment of multiple devices. The USB Human Interface Device (HID) class is targeted a relatively low
speed user input devices like keyboards, mice and joysticks. HID class device developers wish to provide
wireless versions of their products and take advantage of the USB features. This paper presents an
analysis of the issues related to implementing HID class devices that attach to the Universal Serial Bus
through a USB to Wireless Adapter or Dongle. In general the issues raised here apply to any single USB
device that presents multiple HID class devices to the system and the requirements of a device to be HID
A USB HID class device must meet the requirements of the USB Core and HID Class specifications.
These specifications define the protocol, commands and data that must pass between the USB host adapter
and the device. The premise of this paper is that there should be no difference between a wireless and a
wired HID class device, as seen by the USB host. The function of the Wireless Dongle is to is to provide
this transparent operation. This paper analyzes the requirements that a wireless device must meet to
emulate a HID class device to a USB host over a wireless link.
General Wireless Requirements
A key assumption is that the Wireless Dongle communicate with up to 15 independent wireless device
simultaneously and attach to the USB with a single physical connection. In essence the Wireless Dongle is
a host to multiple wireless devices just as the USB Host adapter is a host to multiple USB devices. This
hierarchy mirrors the current USB Host/hub/device hierarchy.
Wireless devices must also support other features of USB such as Hot Plug-in, persistent addressing,
power management and wakeup. Each of these features are key to meeting the usage model that defined
USB and through the Dongle, wi