The concept of software defined radio (SDR) has existed for many years. Consequently, you can find many descriptions of an SDR. A concise definition of an SDR is a radio in which some or all of the physical layer functions are software-defined. The physical layer function is the layer within the wireless protocol in which processing of RF, IF, or baseband signals (including channel coding) occurs. Many of today's SDRs have part of the signal processing implemented in software.
The ability to implement in software numerous waveforms and receiver functions is appealing from the perspective of cost, complexity, programmability, and more. A goal of SDR is to produce an entire radio in software, downconverting the received analog signal to baseband at the antenna port and eliminating much of the hardware in between. Today, SDR is increasingly implemented in both military and commercial networks in more modest ways. The challenge with any SDR design is that it is a complex system that requires analysis from the component through system levels in order to achieve the desired performance. This article explains the attributes of SDR, the design challenges, and it includes hands-on examples of how AWR's Visual System Simulator (VSS) software for system simulation of RF end-to-end architecture design can be used to address these challenges.
SDR in brief
There are many specific processes that define a radio as an SDR. A modern day cell phone, for example, can be considered an SDR because most (if not all) of the baseband processing is performed by a digital signal processing (DSP) chip. SDRs enable a single transceiver to accommodate many different waveforms, which makes it an essential ingredient in creating, for instance, a universally-compatible nationwide public safety network. SDR has long been attractive to manufacturers, commercial wireless carriers, and the military because it enables a single hardware platform to accommodate a wide array of modulated waveforms by implementing them in software. As a