Introduction

Software-Defined Radio (SDR) Forum defines SDR technology as "radios that provide software control of a variety of modulation techniques, wide-band or narrow-band operation, communications security functions (such as hopping), and waveform requirements of current & evolving standards over a broad frequency range."

In a nutshell, Software-Defined Radio (SDR) refers to the technology wherein software modules running on a generic hardware platform consisting of DSPs and general purpose microprocessors are used to implement radio functions such as generation of transmitted signal (modulation) at transmitter and tuning/detection of received radio signal (demodulation) at receiver.

Software-Defined Radio (SDR) is a rapidly evolving technology that is receiving enormous recognition and generating widespread interest in the telecommunication industry. Over the last few years, analog radio systems are being replaced by digital radio systems for various radio applications in military, civilian and commercial spaces. In addition to this, programmable hardware modules are increasingly being used in digital radio systems at different functional levels. SDR technology aims to take advantage of these programmable hardware modules to build an open-architecture based radio system software.

SDR technology facilitates implementation of some of the functional modules in a radio system such as modulation/demodulation, signal generation, coding and link-layer protocols in software. SDR technology can be used to implement military, commercial and civilian radio applications. A wide range of radio applications like Bluetooth, WLAN, GPS, Radar, WCDMA, GPRS, etc. can be implemented using SDR technology. This whitepaper provides an overview of generic SDR features and its architecture with a special focus on the benefits it offers in commercial wireless communication domain.

This section gives a brief overview of a basic conventional digital radio system and then explains how SDR technology can be used to implement radio functions in software. It then explains the software architecture of SDR.
The digital radio system consists of three main functional blocks: RF section, IF section and baseband section. The RE section Consists of essentially analog hardware modules while IF and baseband sections contain digital hardware modules.

SDR has generated tremendous interest in the wireless communication industry for the wide- ranging economic and deployment benefits it offers. Following are some of the problems faced by the wireless communication industry due to implementation of wireless networking infrastructure equipment and terminals completely in hardware:

Commercial wireless network standards are continuously evolving from 2G to 2.5G/3G and then further onto 4G. Each generation of networks differ significantly in link-layer protocol standards causing problems to subscribers, wireless network operators and equipment vendors. Subscribers are forced to buy new handsets whenever a new generation of network standards is deployed. Wireless network operators face problems during migration of the network from one generation to next due to presence of large number of subscribers using legacy handsets that may be incompatible with newer generation network.

The network operators also need to incur high equipment costs when migrating from one generation to next. Equipment vendors face problems in rolling out newer generation equipment due to short time-to-market requirements.