Virtual radios

Conventional software radios take advantage of vastly improved analog to di gital converters (ADC's) and digital signal processing (DSP) hardware. Our approach, which we refer to as virtual radios, also depends upon high perfo rmance ADC's, However, rather than use DSP's, we have chosen to ride the cu rve of rapidly improving workstation hardware. We use wideband digitization and then perform all of the digital signal processing in user space on a g eneral purpose workstation. This approach allows us to experiment with new approaches to signal processing that exploit the hardware and software reso urces of the workstation. Furthermore, it allows us to experiment with diff erent ways of:structuring systems in which the radio component of communica tion devices is integrated with higher-level applications. This paper describes the design and performance of an environment we have c onstructed that facilitates building virtual radios and of two applications built using that environment. The environment consists of an input/output (I/O) subsystem that provides high bandwidth low latency user-level access to digitized signals and a programming environment that provides an infrast ructure for building applications. The applications, which exemplify some o f the benefits of virtual radios, are a software cellular receiver and a no vel wireless network interface.