Certified Wireless USB - Overview

Overview

The rationale for this specification is the overwhelming success of USB as a base for peripherals everywhere: cited reasons include extreme ease of use and low cost, which allow the existence of a ubiquitous bidirectional, fast port architecture. The definition of Ultra-WideBand (UWB) matches the capabilities and transfer rates of USB very closely (from 1.5 and 12 Mbit/s up to 480 Mbit/s for USB 2.0) and makes for a natural wireless extension of USB in the short range (3 meters, up to 10 at a reduced rate of 110 Mbit/s). Still, there is no physical bus to power the peripherals any more, and the absence of wires means that some properties that are usually taken for granted in USB systems need to be achieved by other means.

The goal of the specification is to preserve the functional model of USB, based on intelligent hosts and behaviorally simple devices, while allowing it to operate in a wireless environment and keeping security on a par with the levels offered by traditional wired systems. It also seeks to be comparably power-efficient. To accomplish this, it uses an existing standard which defines a suitable physical layer and medium access control, through which the desired performance can be met, and it adds to it a convergence layer to merge both architectural efforts.

W-USB is defined as a bus, albeit logical and not physical, which can simultaneously connect a host with a number of peripherals. The host divides the available bandwidth through a time-division multiple access (TDMA) strategy. It maintains the ability of USB to safely manage devices on the fly. Hosts can communicate with devices up to 10 meters away.