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.