Software radio is an emerging technology, thought to build flexible radio systems, multiservice, multistandard, multiband, reconfigurable and reprogrammable by software. The flexibility of a software radio system consists in its capability to operate in multiservice environments, without being constrained to particular standard, but able to offer, services of any already standardized systems or future ones on radio frequency band. The presence of the software defining the radio inter face necessarily implies the use of DSPs to replace dedicated hardware to execute, in real-time, the necessary software. Digital communication standard are generally based on different master clock rates. Thus sample rate conversion is required in systems that possess signals of different communication standards..

Software Radio(43)

Software Radio
Abstract
Software radio is the art and science of building radios using software.Given the constraints of todays technology,there is still some hardware involved,but the idea is to get the software as close to the antenna as possible.Ultimately we are turning hardware problems into software problems. A software radio is a radio whose channel modulation waveforms are defined in sofware.The fundamental characteristic is that software defines the transmitted waveforms and software demodulates the recieved waveforms. That is waveforms are generated as sampled digital signals,converted from digital to analog via a wideband DAC and then possibly upconverted from IF to RF.The reciever,similarly,employa a wideband ADC that captures all of the chnnels of the software radio node.The reciever then extracts,downconverts and demodulates the channel waveform using software on a general purpose computer.