Method and apparatus are described for improving information transfer over
USB. In one approach, hub-based extension is realized wherein power is distributed
using auxiliary wiring distinct from signal and power wiring present in conventional
USB cabling. Additional signals allow optimization of power distribution for powering
attached devices, and for detecting and handling illegal connection configurations.
In another approach, improvements are realized through use of alternative signaling
techniques which eschew reflective and high-speed common-mode signaling. Described
are various configuration, media and signal-protocol combinations, including implementations
containing embedded hubs. Methods ensuring reliable system behavior are also described,
including determination of extension path delay and use of topology-enforcement hubs.
In other approaches, further improvements are realized by allowing information
exchanges to take longer than the nominal timeout period, or by allowing host requests
to be delayed for transmission until the extended bus is available for use.