software-defined radio
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Software-defined radio (SDR) is a
radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...
communication system where components that have been traditionally implemented in
analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog ...
hardware (e.g. mixers,
filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...
s,
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the v ...
s,
modulator In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains informatio ...
s/
demodulator Demodulation is extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated ...
s,
detector A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
s, etc.) are instead implemented by means of software on a personal computer or
embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' as ...
. While the concept of SDR is not new, the rapidly evolving capabilities of digital electronics render practical many processes which were once only theoretically possible. A basic SDR system may consist of a
personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...
equipped with a
sound card A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio i ...
, or other
analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...
, preceded by some form of
RF front end RF is an abbreviation for radio frequency. Rf or RF may also mean: Arts and entertainment * ''Red Faction (series)'', a series of revolution video games * Rinforzando, , in music notation * ''RF Online'', an online RPG made by CCR Businesses * A ...
. Significant amounts of
signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, and scientific measurements. Signal processing techniq ...
are handed over to the general-purpose processor, rather than being done in special-purpose hardware (
electronic circuit An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical ...
s). Such a design produces a radio which can receive and transmit widely different radio protocols (sometimes referred to as waveforms) based solely on the software used. Software radios have significant utility for the military and
cell phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...
services, both of which must serve a wide variety of changing radio protocols in real time. In the long term, software-defined radios are expected by proponents like the Wireless Innovation Forum to become the dominant technology in radio communications. SDRs, along with
software defined antenna A reconfigurable antenna is an antenna capable of modifying its frequency and radiation properties dynamically, in a controlled and reversible manner. In order to provide a dynamic response, reconfigurable antennas integrate an inner mechanism (s ...
s are the enablers of the
cognitive radio A cognitive radio (CR) is a radio that can be programmed and configured dynamically to use the best wireless channels in its vicinity to avoid user interference and congestion. Such a radio automatically detects available channels in wireless spec ...
. A software-defined radio can be flexible enough to avoid the "limited spectrum" assumptions of designers of previous kinds of radios, in one or more ways including: *
Spread spectrum In telecommunication and radio communication, spread-spectrum techniques are methods by which a signal (e.g., an electrical, electromagnetic, or acoustic signal) generated with a particular bandwidth is deliberately spread in the frequency dom ...
and
ultrawideband Ultra-wideband (UWB, ultra wideband, ultra-wide band and ultraband) is a radio technology that can use a very low energy level for short-range, high-bandwidth communications over a large portion of the radio spectrum. UWB has traditional applicati ...
techniques allow several transmitters to transmit in the same place on the same frequency with very little interference, typically combined with one or more error detection and correction techniques to fix all the errors caused by that interference. *
Software defined antenna A reconfigurable antenna is an antenna capable of modifying its frequency and radiation properties dynamically, in a controlled and reversible manner. In order to provide a dynamic response, reconfigurable antennas integrate an inner mechanism (s ...
s adaptively "lock onto" a directional signal, so that receivers can better reject interference from other directions, allowing it to detect fainter transmissions. *
Cognitive radio A cognitive radio (CR) is a radio that can be programmed and configured dynamically to use the best wireless channels in its vicinity to avoid user interference and congestion. Such a radio automatically detects available channels in wireless spec ...
techniques: each radio measures the spectrum in use and communicates that information to other cooperating radios, so that transmitters can avoid mutual interference by selecting unused frequencies. Alternatively, each radio connects to a
geolocation database TV White Space database, also commonly referred to as (TV) geolocation database, is an entity that controls the TV spectrum utilization by unlicensed white spaces devices within a determined geographical area. Its sole objective is to enable unlic ...
to obtain information about the spectrum occupancy in its location and, flexibly, adjusts its operating frequency and/or transmit power not to cause interference to other wireless services. * Dynamic transmitter power adjustment, based on information communicated from the receivers, lowering transmit power to the minimum necessary, reducing the
near–far problem The near–far problem or hearability problem is the effect of a strong signal from a near signal source in making it hard for a receiver to hear a weaker signal from a further source due to adjacent-channel interference, co-channel interference, d ...
and reducing interference to others, and extending battery life in portable equipment. *
Wireless mesh network A wireless mesh network (WMN) is a communications network made up of radio nodes organized in a mesh topology. It can also be a form of wireless ad hoc network. Chai Keong Toh Ad Hoc Mobile Wireless Networks, Prentice Hall Publishers, 2002. ...
where every added radio increases total capacity and reduces the power required at any one node. Each node transmits using only enough power needed for the message to hop to the nearest node in that direction, reducing the near–far problem and reducing interference to others.


Operating principles

Superheterodyne receiver A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carr ...
s use a VFO (
variable-frequency oscillator A variable frequency oscillator (VFO) in electronics is an oscillator whose frequency can be tuned (i.e., varied) over some range. It is a necessary component in any tunable radio transmitter or receiver that works by the superheterodyne principl ...
), mixer, and
filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...
to tune the desired signal to a common IF (
intermediate frequency In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier sign ...
) or
baseband In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable into a ...
. Typically in SDR, this signal is then sampled by the analog-to-digital converter. However, in some applications it is not necessary to tune the signal to an intermediate frequency and the radio frequency signal is directly sampled by the
analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...
(after amplification). Real analog-to-digital converters lack the dynamic range to pick up sub-microvolt, nanowatt-power radio signals produced by an antenna. Therefore, a
low-noise amplifier A low-noise amplifier (LNA) is an electronic amplifier that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio. An amplifier will increase the power of both the signal and the noise present at its input, ...
must precede the conversion step and this device introduces its own problems. For example, if spurious signals are present (which is typical), these compete with the desired signals within the amplifier's
dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of signals, like sound and light. It is measured either as a ratio or as a base-1 ...
. They may introduce distortion in the desired signals, or may block them completely. The standard solution is to put
band-pass filter A band-pass filter or bandpass filter (BPF) is a device that passes frequencies within a certain range and rejects (attenuates) frequencies outside that range. Description In electronics and signal processing, a filter is usually a two-por ...
s between the antenna and the amplifier, but these reduce the radio's flexibility. Real software radios often have two or three analog channel filters with different bandwidths that are switched in and out.


History

In 1970, a researcher at a
United States Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national secu ...
laboratory coined the term "digital receiver". A laboratory called the Gold Room at TRW in California created a software baseband analysis tool called Midas, which had its operation defined in software. In 1982, while working under a US Department of Defense contract at
RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...
, Ulrich L. Rohde’s department developed the first SDR, which used the COSMAC (Complementary Symmetry Monolithic Array Computer) chip. Rohde was the first to present on this topic with his February 1984 talk, “Digital HF Radio: A Sampling of Techniques” at the Third International Conference on HF Communication Systems and Techniques in London. In 1984, a team at the
Garland, Texas Garland is a city in the U.S. state of Texas. It is located northeast of Dallas and is a part of the Dallas–Fort Worth metroplex. It is located within Dallas County except for small portions located in Collin and Rockwall Counties. At the ...
, Division of
E-Systems Raytheon Intelligence, Information, and Services (RIIS or IIS) is a business unit of Raytheon Company headquartered in Dulles, Virginia. IIS specializes in intelligence, surveillance, and reconnaissance, advanced cybersecurity solutions; weather ...
Inc. (now
Raytheon Raytheon Technologies Corporation is an American multinational aerospace and defense conglomerate headquartered in Arlington, Virginia. It is one of the largest aerospace and defense manufacturers in the world by revenue and market capitaliza ...
) coined the term "software radio" to refer to a digital baseband receiver, as published in their E-Team company newsletter. A 'Software Radio Proof-of-Concept' laboratory was developed by the E-Systems team that popularized Software Radio within various government agencies. This 1984 Software Radio was a digital
baseband In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable into a ...
receiver that provided programmable interference cancellation and demodulation for broadband signals, typically with thousands of
adaptive filter An adaptive filter is a system with a linear filter that has a transfer function controlled by variable parameters and a means to adjust those parameters according to an optimization algorithm. Because of the complexity of the optimization algorit ...
taps, using multiple
array processor In computing, a vector processor or array processor is a central processing unit (CPU) that implements an instruction set where its instructions are designed to operate efficiently and effectively on large one-dimensional arrays of data called ' ...
s accessing shared memory. In 1991, Joe Mitola independently reinvented the term software radio for a plan to build a GSM base station that would combine Ferdensi's digital receiver with E-Systems Melpar's digitally controlled communications jammers for a true software-based transceiver. E-Systems Melpar sold the software radio idea to the US Air Force. Melpar built a prototype commanders' tactical terminal in 1990–1991 that employed Texas Instruments TMS320C30 processors and Harris digital receiver chip sets with digitally synthesized transmission. The Melpar prototype didn't last long because when E-Systems ECI Division manufactured the first limited production units, they decided to "throw out those useless C30 boards", replacing them with conventional RF filtering on transmit and receive, reverting to a digital baseband radio instead of the SpeakEasy like IF ADC/DACs of Mitola's prototype. The Air Force would not let Mitola publish the technical details of that prototype, nor would they let Diane Wasserman publish related software life cycle lessons learned because they regarded it as a "USAF competitive advantage". So instead, with USAF permission, in 1991, Mitola described the architecture principles without implementation details in a paper, "Software Radio: Survey, Critical Analysis and Future Directions" which became the first IEEE publication to employ the term in 1992. When Mitola presented the paper at the conference, Bob Prill of GEC Marconi began his presentation following Mitola with: "Joe is absolutely right about the theory of a software radio and we are building one." Prill gave a GEC Marconi paper on PAVE PILLAR, a SpeakEasy precursor. SpeakEasy, the military software radio was formulated by Wayne Bonser, then of
Rome Air Development Center Rome Laboratory (Rome Air Development Center until 1991) is the US "Air Force 'superlab' for command, control, and communications" research and development and is responsible for planning and executing the USAF science and technology program. ...
(RADC), now Rome Labs; by Alan Margulies of MITRE Rome, NY; and then Lt Beth Kaspar, the original DARPA SpeakEasy project manager and by others at Rome including Don Upmal. Although Mitola's IEEE publications resulted in the largest global footprint for software radio, Mitola privately credits that DoD lab of the 1970s with its leaders Carl, Dave, and John with inventing the digital receiver technology on which he based software radio once it was possible to transmit via software. A few months after the National Telesystems Conference 1992, in an E-Systems corporate program review, a vice-president of E-Systems Garland Division objected to Melpar's (Mitola's) use of the term "software radio" without credit to Garland. Alan Jackson, Melpar VP of marketing at that time, asked the Garland VP if their laboratory or devices included transmitters. The Garland VP said: "No, of course not — ours is a software radio receiver." Al replied: "Then it's a digital receiver but without a transmitter, it's not a software radio." Corporate leadership agreed with Al, so the publication stood. Many amateur radio operators and HF radio engineers had realized the value of digitizing HF at RF and of processing it with Texas Instruments TI C30
digital signal processor A digital signal processor (DSP) is a specialized microprocessor chip, with its architecture optimized for the operational needs of digital signal processing. DSPs are fabricated on MOS integrated circuit chips. They are widely used in audio si ...
s (DSPs) and their precursors during the 1980s and early 1990s. Radio engineers at
Roke Manor Roke Manor is a 17th-century manor house approximately north-west of Romsey in Hampshire, England. The house and grounds are the headquarters of Roke Manor Research Ltd, a subsidiary of Chemring Group. History The first known reference t ...
in the UK and at an organization in Germany had recognized the benefits of ADC at the RF in parallel. Mitola's publication of software radio in the IEEE opened the concept to the broad community of radio engineers. His May 1995 special issue of the
IEEE Communications Magazine The ''IEEE Communications Magazine'' is a monthly magazine published by the IEEE Communications Society dealing with all areas of communications including light-wave telecommunications, high-speed data communications, personal communications syst ...
with the cover "Software Radio" was regarded as a watershed event with thousands of academic citations. Mitola was introduced by Joao da Silva in 1997 at the First International Conference on Software Radio as "godfather" of software radio in no small part for his willingness to share such a valuable technology "in the public interest". Perhaps the first software-based radio
transceiver In radio communication, a transceiver is an electronic device which is a combination of a radio ''trans''mitter and a re''ceiver'', hence the name. It can both transmit and receive radio waves using an antenna, for communication purposes. The ...
was designed and implemented by Peter Hoeher and Helmuth Lang at the German Aerospace Research Establishment ( DLR, formerly
DFVLR The German Aerospace Center (german: Deutsches Zentrum für Luft- und Raumfahrt e.V., abbreviated DLR, literally ''German Center for Air- and Space-flight'') is the national center for aerospace, energy and transportation research of Germany ...
) in
Oberpfaffenhofen Oberpfaffenhofen is a village that is part of the municipality of Weßling in the district of Starnberg, Bavaria, Germany. It is located about from the city center of Munich. Village The village is home to the Oberpfaffenhofen Airport and a m ...
, Germany, in 1988. Both transmitter and receiver of an adaptive digital satellite modem were implemented according to the principles of a software radio, and a flexible hardware periphery was proposed. In 1995, Stephen Blust coined the term "software defined radio", publishing a request for information from Bell South Wireless at the first meeting of the Modular Multifunction Information Transfer Systems (MMITS) forum in 1996, organized by the USAF and DARPA around the commercialization of their SpeakEasy II program. Mitola objected to Blust's term, but finally accepted it as a pragmatic pathway towards the ideal software radio. Although the concept was first implemented with an IF ADC in the early 1990s, software-defined radios have their origins in the U.S. and European defense sectors of the late 1970s (for example, Walter Tuttlebee described a VLF radio that used an ADC and an 8085 microprocessor), about a year after the First International Conference in Brussels. One of the first public software radio initiatives was the U.S. DARPA-Air Force
military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...
project named
SpeakEasy A speakeasy, also called a blind pig or blind tiger, is an illicit establishment that sells alcoholic beverages, or a retro style bar that replicates aspects of historical speakeasies. Speakeasy bars came into prominence in the United States d ...
. The primary goal of the SpeakEasy project was to use programmable processing to emulate more than 10 existing military radios, operating in
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
bands between 2 and 2000
MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
. Another SpeakEasy design goal was to be able to easily incorporate new coding and modulation standards in the future, so that military communications can keep pace with advances in coding and modulation techniques. In 1997,
Blaupunkt Blaupunkt GmbH () was a German manufacturer of mostly car audio equipment. It was owned by Robert Bosch GmbH from 1933 until 1 March 2009, when it was sold to Aurelius AG of Germany. It filed for bankruptcy in late 2015 with liquidation proceed ...
introduced the term "DigiCeiver" for their new range of DSP-based tuners with Sharx in
car radio Vehicle audio is equipment installed in a car or other vehicle to provide in-car entertainment and information for the vehicle occupants. Until the 1950s it consisted of a simple AM radio. Additions since then have included FM radio (1952), 8 ...
s such as the Modena & Lausanne RD 148.


SpeakEasy phase I

From 1990 to 1995, the goal of the
SpeakEasy A speakeasy, also called a blind pig or blind tiger, is an illicit establishment that sells alcoholic beverages, or a retro style bar that replicates aspects of historical speakeasies. Speakeasy bars came into prominence in the United States d ...
program was to demonstrate a radio for the
U.S. Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Sign ...
tactical ground air control party that could operate from 2
MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
to 2
GHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
, and thus could interoperate with ground force radios (frequency-agile VHF, FM, and
SINCGARS Single Channel Ground and Airborne Radio System (SINCGARS) is a Combat-net radio (CNR) used by U.S. and allied military forces. The CNR network is designed around three systems: SINCGARS, the high frequency (HF) radio, and the SC tactical sate ...
), Air Force radios (VHF AM), Naval Radios (VHF AM and HF SSB
teleprinter A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...
s) and satellites (
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ran ...
QAM Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message signa ...
). Some particular goals were to provide a new signal format in two weeks from a standing start, and demonstrate a radio into which multiple contractors could plug parts and software. The project was demonstrated at TF-XXI Advanced Warfighting Exercise, and demonstrated all of these goals in a non-production radio. There was some discontent with failure of these early software radios to adequately filter out of band emissions, to employ more than the simplest of interoperable modes of the existing radios, and to lose connectivity or crash unexpectedly. Its
cryptographic Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or '' -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adve ...
processor could not change context fast enough to keep several radio conversations on the air at once. Its software architecture, though practical enough, bore no resemblance to any other. The SpeakEasy architecture was refined at the MMITS Forum between 1996 and 1999 and inspired the DoD integrated process team (IPT) for programmable modular communications systems (PMCS) to proceed with what became the Joint Tactical Radio System (JTRS). The basic arrangement of the radio receiver used an
antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...
feeding an
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the v ...
and down-converter (see
Frequency mixer In electronics, a mixer, or frequency mixer, is an electrical circuit that creates new frequencies from two signals applied to it. In its most common application, two signals are applied to a mixer, and it produces new signals at the sum and di ...
) feeding an
automatic gain control Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the inpu ...
, which fed an
analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...
that was on a computer
VMEbus VMEbus (Versa Module Europa or Versa Module Eurocard bus) is a computer bus standard, originally developed for the Motorola 68000 line of CPUs, but later widely used for many applications and standardized by the IEC as ANSI/IEEE 1014-1987. I ...
with a lot of
digital signal processor A digital signal processor (DSP) is a specialized microprocessor chip, with its architecture optimized for the operational needs of digital signal processing. DSPs are fabricated on MOS integrated circuit chips. They are widely used in audio si ...
s (
Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globall ...
C40s). The transmitter had
digital to analog converter In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function. There are several DAC architec ...
s on the
PCI bus PCI may refer to: Business and economics * Payment card industry, businesses associated with debit, credit, and other payment cards ** Payment Card Industry Data Security Standard, a set of security requirements for credit card processors * Prov ...
feeding an up converter (mixer) that led to a power amplifier and antenna. The very wide frequency range was divided into a few sub-bands with different analog radio technologies feeding the same analog to digital converters. This has since become a standard design scheme for wideband software radios.


SpeakEasy phase II

The goal was to get a more quickly reconfigurable architecture, ''i.e.'', several conversations at once, in an ''open'' software architecture, with cross-channel connectivity (the radio can "bridge" different radio protocols). The secondary goals were to make it smaller, cheaper, and weigh less. The project produced a demonstration radio only fifteen months into a three-year research project. This demonstration was so successful that further development was halted, and the radio went into production with only a 4 MHz to 400 MHz range. The software architecture identified standard interfaces for different modules of the radio: "radio frequency control" to manage the analog parts of the radio, "modem control" managed resources for
modulation In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains informatio ...
and
demodulation Demodulation is extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated ...
schemes (FM, AM, SSB, QAM, etc.), "waveform processing" modules actually performed the
modem A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...
functions, "key processing" and "cryptographic processing" managed the cryptographic functions, a "multimedia" module did voice processing, a "human interface" provided local or remote controls, there was a "routing" module for network services, and a "control" module to keep it all straight. The modules are said to communicate without a central operating system. Instead, they send messages over the PCI
computer bus In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This ex ...
to each other with a layered protocol. As a military project, the radio strongly distinguished "red" (unsecured secret data) and "black" (cryptographically-secured data). The project was the first known to use
FPGA A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term '' field-programmable''. The FPGA configuration is generally specified using a hardware de ...
s (field programmable gate arrays) for digital processing of radio data. The time to reprogram these was an issue limiting application of the radio. Today, the time to write a program for an FPGA is still significant, but the time to download a stored FPGA program is around 20 milliseconds. This means an SDR could change transmission protocols and frequencies in one fiftieth of a second, probably not an intolerable interruption for that task.


2000s

The SpeakEasy SDR system in the 1994 uses a Texas Instruments TMS320C30
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFE ...
digital signal processor A digital signal processor (DSP) is a specialized microprocessor chip, with its architecture optimized for the operational needs of digital signal processing. DSPs are fabricated on MOS integrated circuit chips. They are widely used in audio si ...
(DSP), along with several hundred
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
chips, with the radio filling the back of a truck. By the late 2000s, the emergence of
RF CMOS RF CMOS is a metal–oxide–semiconductor (MOS) integrated circuit (IC) technology that integrates radio-frequency (RF), analog and digital electronics on a mixed-signal CMOS (complementary MOS) RF circuit chip. It is widely used in modern wire ...
technology made it practical to scale down an entire SDR system onto a single
mixed-signal A mixed-signal integrated circuit is any integrated circuit that has both analog circuits and digital circuits on a single semiconductor die.system-on-a-chip A system on a chip or system-on-chip (SoC ; pl. ''SoCs'' ) is an integrated circuit that integrates most or all components of a computer or other electronic system. These components almost always include a central processing unit (CPU), memory ...
, which
Broadcom Broadcom Inc. is an American designer, developer, manufacturer and global supplier of a wide range of semiconductor and infrastructure software products. Broadcom's product offerings serve the data center, networking, software, broadband, wirel ...
demonstrated with the BCM21551 processor in 2007. The Broadcom BCM21551 has practical commercial applications, for use in 3G
mobile phones A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...
.


Military usage


United States

The
Joint Tactical Radio System The Joint Tactical Radio System (JTRS) aimed to replace existing radios in the American military with a single set of software-defined radios that could have new frequencies and modes (“waveforms”) added via upload, instead of requiring mult ...
(JTRS) was a program of the US military to produce radios that provide flexible and interoperable communications. Examples of radio terminals that require support include hand-held, vehicular, airborne and dismounted radios, as well as base-stations (fixed and maritime). This goal is achieved through the use of SDR systems based on an internationally endorsed open
Software Communications Architecture {{inline, date=May 2014 The Software Communications Architecture (SCA) is an open architecture Open architecture is a type of computer architecture or software architecture intended to make adding, upgrading, and swapping components with other ...
(SCA). This standard uses
CORBA The Common Object Request Broker Architecture (CORBA) is a standard defined by the Object Management Group (OMG) designed to facilitate the communication of systems that are deployed on diverse platforms. CORBA enables collaboration between sys ...
on
POSIX The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...
operating systems to coordinate various software modules. The program is providing a flexible new approach to meet diverse soldier communications needs through software programmable radio technology. All functionality and expandability is built upon the SCA. SDRs flexibility results in expensive complexity, inability to optimize, slower ability to apply the latest technology, and rarely a tactical user need (since all users must pick and stay with the one, same radio if they're to communicate). The SCA, despite its military origin, is under evaluation by commercial radio vendors for applicability in their domains. The adoption of general-purpose SDR frameworks outside of military, intelligence, experimental and amateur uses, however, is inherently hampered by the fact that civilian users can more easily settle with a fixed architecture, optimized for a specific function, and as such more economical in mass market applications. Still, software defined radio's inherent flexibility can yield substantial benefits in the longer run, once the fixed costs of implementing it have gone down enough to overtake the cost of iterated redesign of purpose built systems. This then explains the increasing commercial interest in the technology. SCA-based infrastructure software and rapid development tools for SDR education and research are provided by the Open Source SCA Implementation Embedded (OSSIE) project. The Wireless Innovation Forum funded the SCA Reference Implementation project, an open source implementation of the SCA specification. ( SCARI) can be downloaded for free.


Amateur and home use

A typical
amateur An amateur () is generally considered a person who pursues an avocation independent from their source of income. Amateurs and their pursuits are also described as popular, informal, autodidacticism, self-taught, user-generated, do it yourself, DI ...
software radio uses a
direct conversion receiver A direct-conversion receiver (DCR), also known as homodyne, synchrodyne, or zero-IF receiver, is a radio receiver design that demodulates the incoming radio signal using synchronous detection driven by a local oscillator whose frequency is ide ...
. Unlike direct conversion receivers of the more distant past, the mixer technologies used are based on the quadrature sampling detector and the quadrature sampling exciter. The receiver performance of this line of SDRs is directly related to the dynamic range of the analog-to-digital converters (ADCs) utilized. Radio frequency signals are down converted to the audio frequency band, which is sampled by a high performance audio frequency ADC. First generation SDRs used a 44 kHz PC sound card to provide
ADC ADC may refer to: Science and medicine * ADC (gene), a human gene * AIDS dementia complex, neurological disorder associated with HIV and AIDS * Allyl diglycol carbonate or CR-39, a polymer * Antibody-drug conjugate, a type of anticancer treatm ...
functionality. The newer software defined radios use embedded high performance ADCs that provide higher
dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of signals, like sound and light. It is measured either as a ratio or as a base-1 ...
and are more resistant to noise and RF interference. A fast PC performs the
digital signal processing Digital signal processing (DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The digital signals processed in this manner are ...
(DSP) operations using software specific for the radio hardware. Several software radio implementations use the open source SDR library DttSP. The SDR software performs all of the demodulation, filtering (both radio frequency and audio frequency), and signal enhancement (equalization and binaural presentation). Uses include every common amateur modulation:
morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one of ...
, single-sideband modulation,
frequency modulation Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and Run-length limited#FM: .280. ...
,
amplitude modulation Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to ...
, and a variety of digital modes such as
radioteletype Radioteletype (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link. Radioteletype evolved from earlier landline teleprinter o ...
,
slow-scan television Slow-scan television (SSTV) is a picture transmission method, used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or color. A literal term for SSTV is narrowband television. Analog broadcast tel ...
, and
packet radio In digital radio, packet radio is the application of packet switching techniques to digital radio communications. Packet radio uses a packet switching protocol as opposed to circuit switching or message switching protocols to transmit digital dat ...
. Amateurs also experiment with new modulation methods: for instance, the
DREAM A dream is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around 5 to 20 minutes, althou ...
open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
project decodes the
COFDM In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communi ...
technique used by
Digital Radio Mondiale Digital Radio Mondiale (DRM; ''mondiale'' being Italian and French for "worldwide") is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—pa ...
. There is a broad range of hardware solutions for radio amateurs and home use. There are professional-grade transceiver solutions, e.g. the Zeus ZS-1 or the Flex Radio, home-brew solutions, e.g. PicAStar transceiver, the SoftRock SDR kit, and starter or professional receiver solutions, e.g. the FiFi SDR for shortwave, or the Quadrus coherent multi-channel SDR receiver for short wave or VHF/UHF in direct digital mode of operation.


RTL-SDR

Eric Fry discovered that some common low-cost
DVB-T DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Febr ...
USB dongles with the Realtek RTL2832U controller and tuner, e.g. the Elonics E4000 or the Rafael Micro R820T, can be used as a wide-band (3 MHz) SDR receiver. Experiments proved the capability of this setup to analyze Perseids meteor shower using Graves radar signals. This project is being maintained at
Osmocom Osmocom (open source mobile communications) is an open-source software project that implements multiple mobile communication standards, including GSM, DECT, TETRA and others. History and usage In 2008 Harald Welte and Dieter Spaar experiment ...
.


USRP

More recently, the
GNU Radio GNU Radio is a free software development toolkit that provides signal processing blocks to implement software-defined radios and signal processing, signal-processing systems. It can be used with external Radio frequency, RF hardware to create soft ...
using primarily the
Universal Software Radio Peripheral Universal Software Radio Peripheral (USRP) is a range of software-defined radios designed and sold by Ettus Research and its parent company, National Instruments. Developed by a team led by Matt Ettus, the USRP product family is commonly used ...
(USRP) uses a
USB Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad ...
2.0 interface, an
FPGA A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term '' field-programmable''. The FPGA configuration is generally specified using a hardware de ...
, and a high-speed set of analog-to-digital and digital-to-analog converters, combined with reconfigurable
free software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...
. Its sampling and synthesis bandwidth (30-120 MHz) is a thousand times that of PC sound cards, which enables
wideband In communications, a system is wideband when the message bandwidth significantly exceeds the coherence bandwidth of the Channel (communications), channel. Some communication links have such a high Bit rate, data rate that they are forced to use a ...
operation.


HPSDR

The
HPSDR The OpenHPSDR (High Performance Software Defined Radio) project dates from 2005 when Phil Covington, Phil Harman, and Bill Tracey combined their separate projects to form the HPSDR group. It is built around a modular concept which encourages ex ...
(High Performance Software Defined Radio) project uses a 16-bit analog-to-digital converter that provides performance over the range 0 to comparable to that of a conventional analogue HF radio. The receiver will also operate in the VHF and UHF range using either mixer image or alias responses. Interface to a PC is provided by a
USB Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad ...
2.0 interface, although
Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
could be used as well. The project is modular and comprises a
backplane A backplane (or "backplane system") is a group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used as a back ...
onto which other boards plug in. This allows experimentation with new techniques and devices without the need to replace the entire set of boards. An exciter provides of RF over the same range or into the VHF and UHF range using image or alias outputs.


WebSDR

WebSDR is a project initiated by Pieter-Tjerk de Boer providing access via browser to multiple SDR receivers worldwide covering the complete shortwave spectrum. Recently he has analyzed
Chirp Transmitter An ionosonde, or chirpsounder, is a special radar for the examination of the ionosphere. The basic ionosonde technology was invented in 1925 by Gregory Breit and Merle A. Tuve and further developed in the late 1920s by a number of prominent ph ...
signals using the coupled system of receivers.Chirp Signals analyzed using SDR http://websdr.ewi.utwente.nl:8901/chirps/


Other applications

On account of its increasing accessibility, with lower cost hardware, more software tools and documentation, the applications of SDR have expanded past their primary and historic use cases. SDR is now being used in areas such as wildlife tracking, radio astronomy, medical imaging research, and art.


See also

*
List of software-defined radios This article provides a list of commercially available software-defined radio Software-defined radio (SDR) is a radio communication system where components that have been traditionally implemented in analog hardware (e.g. mixers, filters, am ...
*
List of amateur radio software This is a list of software for amateur radio. Software tools Logging Software Operating systems The Debian project maintains a pure blend that includes ham radio software. The HamBSD project is a variation of OpenBSD. See also * ...
*
Digital radio Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services. Types In digital broadcasting syst ...
*
Digital signal processing Digital signal processing (DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The digital signals processed in this manner are ...
(DSP) *
Radio Interface Layer A Radio Interface Layer (RIL) is a layer in an operating system which provides an interface to the hardware's radio and modem on e.g. a mobile phone. Android RIL The Android Open Source Project provides a Radio Interface Layer (RIL) between Andr ...
(RIL) *
Softmodem A software modem, commonly referred to as a softmodem, is a modem with minimal hardware that uses software running on the host computer, and the computer's resources (especially the central processing unit, random access memory, and sometimes ...
*
Software defined mobile network Software-defined mobile networking (SDMN) is an approach to the design of mobile networks where all protocol-specific features are implemented in software, maximizing the use of generic and commodity hardware and software in both the core network a ...
(SDMN) *
Software GNSS Receiver A software GNSS receiver is a Global Navigation Satellite System (GNSS) receiver that has been designed and implemented using software-defined radio. A GNSS receiver, in general, is an electronic device that receives and digitally processes the ...
*
White space (radio) In telecommunications, white spaces refer to radio frequencies allocated to a broadcasting service but not used locally. National and international bodies assign frequencies for specific uses and, in most cases, license the rights to broadcast o ...
* White space (database) *
Bit banging In computer engineering and electrical engineering, bit banging is a "term of art" for any method of data transmission that employs software as a substitute for dedicated hardware to generate transmitted signals or process received signals. Soft ...


References


Further reading

* * ''Software defined radio : architectures, systems, and functions.'' Dillinger, Madani, Alonistioti. Wiley, 2003. 454 pages. * ''Cognitive Radio Technology.'' Bruce Fette. Elsevier Science & Technology Books, 2006. 656 pags. * ''Software Defined Radio for 3G,'' Burns. Artech House, 2002. * ''Software Radio: A Modern Approach to Radio Engineering,'' Jeffrey H. Reed. Prentice Hall PTR, 2002. * ''Signal Processing Techniques for Software Radio,'' Behrouz Farhang-Beroujeny. LuLu Press. * ''RF and Baseband Techniques for Software Defined Radio,'' Peter B. Kenington. Artech House, 2005, * ''The ABC's of Software Defined Radio,'' Martin Ewing, AA6E. The American Radio Relay League, Inc., 2012, * ''Software Defined Radio using MATLAB & Simulink and the RTL-SDR,'' R Stewart, K Barlee, D Atkinson, L Crockett, Strathclyde Academic Media, September 2015.


External links


The world's first web-based software-defined receiver
at the university of Twente, the Netherlands
Software-defined receivers connected to the Internet


* ttp://www.desktopSDR.com Free SDR textbook: Software Defined Radio using MATLAB & Simulink and the RTL-SDR
Welcome to the World of Software Defined Radio
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