Periodic and Sporadic Device Requests

As the Universal Serial Bus 2.0 becomes a major driving force in the peripherals market now, the variety of devices and their request types also impose challenging issues on resource allocation of bus bandwidth. research aims at the proposing of a USB-compliant system architec- ture and real-time scheduling algorithms for the resource allocation of USB 2.0 and 1.1 device requests jointly in a Quality-of-Service fashion. Periodic requests, such as isochronous and interrupt transfers, are guaranteed with preservation of bus bandwidth and schedulability tests. Spo- radic requests, such as control and bulk transfer, are serviced with probabilistic performance guarantees. The capability of this work is demonstrated with evaluations over a Linux system prototype, for which we have encouraging re- sults.