Softmodem - AbsoluteAstronomy.com

A Softmodem, or software modem, is a modem

Modem

A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...

with minimal hardware capacities, designed to use a host computer's resources (mostly CPU

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

power and RAM but sometimes even audio hardware

Sound card

A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...

) to perform most of the tasks performed by dedicated hardware in a traditional modem.

A Softmodem is also referred to as a Winmodem because the first commercially available softmodems mostly worked only with the Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

family of operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

s running on IBM PC compatible

IBM PC compatible

IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...

s. Although their usage has become more widespread on other operating systems and machines, such as embedded system

Embedded system

An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...

s and Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

, they are still difficult to use on operating systems other than Windows due to lack of vendor support and lack of a standard device interface. The term "Winmodem" is a trademark of U.S. Robotics

U.S. Robotics

USRobotics Corporation is a company that makes computer modems and related products. It sold high-speed modems in the 1980s, and had a reputation for high quality and compatibility. With the reduced usage of voiceband modems in North America in the early 21st century, USR is now one of the few...

but it is usually used to describe other modems

Genericized trademark

A genericized trademark is a trademark or brand name that has become the colloquial or generic description for, or synonymous with, a general class of product or service, rather than as an indicator of source or affiliation as intended by the trademark's holder...

with similar technologies.

Evolution and technology

As PSTN modem technology advanced, the modulation and encoding schemes became increasingly more complex, thus forcing the hardware used by the modems themselves to increase in complexity.

The first generations of modems (including acoustic coupler

Acoustic coupler

In telecommunications, the term acoustic coupler has the following meanings:# An interface device for coupling electrical signals by acoustical means—usually into and out of a telephone instrument....

s) and their protocols used relatively simple modulation techniques such as FSK or ASK at low speeds and with inefficient use of the telephone line's bandwidth. Under these conditions, modems could be built with the analog discrete component technology used during the late 70s and early 80s.

As more sophisticated transmission schemes were devised, the circuits grew in complexity, mixing analog with digital parts and eventually incorporating multiple ICs

Integrated circuit

An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

such as logical gates, PLL's and microcontroller

Microcontroller

A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...

s, while the techniques used in modern v34, v.90 and v.92

V.92

V.92 is an ITU-T recommendation, titled Enhancements to Recommendation V.90, that establishes a modem standard allowing near 56 kb/s download and 48 kb/s upload rates. With V.92 PCM is used for both the upstream and downstream connections; previously 56K modems only used PCM for downstream...

protocols (like 1024-QAM

Quadrature amplitude modulation

Quadrature amplitude modulation is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing the amplitudes of two carrier waves, using the amplitude-shift keying digital modulation scheme or amplitude modulation analog...

) are so complex that implementing a modem supporting them with discrete components or general purpose IC's would be very impractical, and a dedicated DSP

Digital signal processor

A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...

or ASIC

ASIC

ASIC may refer to:* Application-specific integrated circuit, an integrated circuit developed for a particular use, as opposed to a customised general-purpose device.* ASIC programming language, a dialect of BASIC...

is used instead, effectively turning the modem into a special embedded system

Embedded system

, a dedicated computer in its own right.

Furthermore, improved compression and error correction schemes were introduced in the newest protocols, requiring processing power by the modem itself. This made the construction of a mainly analog/discrete component modem impossible, especially when trying to achieve compatibility with older protocols using completely different modulation schemes.

Thus modems supporting those standards were becoming steadily more complex and expensive themselves, not to mention the fact that several conflicting standards in the early days of the various 33.6K (v34) and 56K protocols led to incompatibilities and the construction of modems with upgradeable firmware, which did all of the processing via a programmable DSP

Digital signal processor

A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...

.

By offering (or claiming to offer) the same functionality as a hardware modem at a fraction of the price and (theoretically) a capacity for unlimited upgrades, the advantages of software-based modems became compelling. However, they would still require significant advances in home PCs' CPU power in order to compete with hardware modems in terms of performance and reliability.

Advantages

Having most of the modulation functions delegated to software does serve to provide the advantage of easier upgrade

Upgrade

The term upgrade refers to the replacement of a product with a newer version of the same product. It is most often used in computing and consumer electronics, generally meaning a replacement of hardware, software or firmware with a newer or better version, in order to bring the system up to date...

ability to newer modem standard

Standardization

Standardization is the process of developing and implementing technical standards.The goals of standardization can be to help with independence of single suppliers , compatibility, interoperability, safety, repeatability, or quality....

s. However, this is hardly an advantage as of 2005, with the latest V.92 56K protocol practically bearing the maximum achievable performance for a normal PSTN modem and telephone line and no significant future improvements/advancements seeming possible. Nevertheless, this is not yet the case with the more recent software-based DSL modems

Digital Subscriber Line

Digital subscriber line is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop. In telecommunications marketing, the term DSL is widely understood to mean Asymmetric Digital Subscriber Line ,...

, whose easy upgradeability can still be an advantage. More commonly, however, softmodem drivers are enhanced in regard to their performance and to eliminate possible software bugs.

A more practical advantage of softmodems is given by the considerable reductions in production costs, component count, size

Dimension

In physics and mathematics, the dimension of a space or object is informally defined as the minimum number of coordinates needed to specify any point within it. Thus a line has a dimension of one because only one coordinate is needed to specify a point on it...

, weight

Weight

In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...

and power requirements compared to a hardware modem, whether external or internal, to the point that most modems that are integrated in portable computer systems (including high-end laptops and PDAs

Personal digital assistant

A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...

) are softmodems.

Because they do so little by themselves, a computer program could use a Softmodem as something other than a modem; for example, it could emulate an answering machine

Answering machine

The answering machine or message machine, also known as the telephone answering machine in the UK and some Commonwealth countries) and previously known as an ansaphone, ansafone, or telephone answering device is a device for answering telephones and recording callers' messages.Unlike voicemail,...

or a signal generator

Signal generator

Signal generators, also known variously as function generators, RF and microwave signal generators, pitch generators, arbitrary waveform generators, digital pattern generators or frequency generators are electronic devices that generate repeating or non-repeating electronic signals...

.

Most PC serial port

Serial port

In computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time...

s, the traditional interface for external hardware modems, are limited to 115,200 bits per second by UART limitations, though some ports are capable of 230,400 bit/s. V.92

V.92

modems with V.44 compression can have an effective throughput of up to 300,000 bit/s. Since a V.92 hardware modem performs V.44 compression internally, the speed of a serial port can limit a hardware modem's overall speed; this is not an issue for softmodems since the host PC performs V.44 compression and emulates the serial port. Thus, V.92/V.44 softmodems are potentially capable of outperforming hardware modems.

Disadvantages

Winmodems have earned a certain notoriety for slowing down their host computer systems and for having buggy drivers, although this reputation was largely garnered during the period of their introduction to the mass market, whereupon they were apt to use substandard drivers and be found in entry-level computers with slow CPUs. Any such reputation has not, however, halted their market popularity; most internal 56k modems produced since 1998 have been software-based.

Nowadays, with modern CPUs and better drivers, their most serious drawback is that they are operating system and machine dependent. They cannot always be used on other operating systems and host machines because the driver

Device driver

In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....

support requires far more effort to produce.

They consume some CPU

Central processing unit

cycles on the computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

to which they are attached, which can slow down application

Application software

Application software, also known as an application or an "app", is computer software designed to help the user to perform specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with...

software on older computers. They are sometimes referred to as a "port-on-a-stick".

The advantage of software upgradeability was diminished when many newer hardware modems gained the ability to upgrade firmware

Firmware

In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...

to support new standards. Modems such as those made by U.S. Robotics

U.S. Robotics

used generic digital signal processors architecture, which achieves the flexibility of softmodems, without sacrificing compatibility.

DSL softmodems

Although the term has historically been used to indicate the traditional "analog" PSTN software modems, there are some software-based DSL

Digital Subscriber Line

modems or even routers, which work on the same principles as their PSTN ancestors, only on a larger bandwidth and on a more complex signal. One of the first software based DSL modem chipsets was Motorola's

Motorola

SoftDSL chipset, for which similar considerations as "ordinary" PSTN modems can be made. The term WinDSL has shown up on technology sites like Slashdot

Slashdot

Slashdot is a technology-related news website owned by Geeknet, Inc. The site, which bills itself as "News for Nerds. Stuff that Matters", features user-submitted and ‑evaluated current affairs news stories about science- and technology-related topics. Each story has a comments section...

regarding this trend. DSL softmodems generally require the same interfaces as PSTN softmodems, such as USB

Universal Serial Bus

USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....

or PCI

Peripheral Component Interconnect

Conventional PCI is a computer bus for attaching hardware devices in a computer...

.

However, the increasing popularity of home networking limited the prospects for DSL softmodems. Many households and small businesses have a router connected to the DSL modem, and all their computers are connected by various types of wired or wireless networks to that router. For that reason, most broadband modems today (cable

Cable modem

A cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a HFC and RFoG infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high...

as well as DSL) are external devices with either Ethernet

Ethernet

Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....

connections for single PCs or routers, or built-in routers of their own; these interfaces require a full-hardware implementation. Most current broadband modems with USB jacks also have Ethernet jacks, and thus are full-hardware modems.

General description

Often, the term "Winmodem" or "softmodem" is used in a derogatory manner, as opposed to hardware or "real" modems. The argument is that a softmodem isn't a real modem at all, but rather a simple electrical interface between computer and phone line, limiting itself to very basic functions such as voltage/current adaptation and functioning essentially as a DAC

Digital-to-analog converter

In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...

/ADC

Analog-to-digital converter

An analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...

, much like a sound card

Sound card

which handles pure PCM and analog signals from and to the telephone line, while the host's CPU does the actual job of synthesizing or analyzing all necessary waveforms (carrier, dialing tones) and applying all necessary DSP

Digital signal processing

Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...

techniques (FSK, QAM

Quadrature amplitude modulation

, PSK etc.) to a "virtual" signal, in order to encode and decode inbound or outbound data.

This means that at least the simplest softmodem is nothing more than a special purpose sound card

Sound card

with mono DAC

Digital-to-analog converter

In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...

/ADC

Analog-to-digital converter

An analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...

's and a telephone line interface, while all actual signal encoding/decoding (as well as compression/decompression, error correction etc.) is done by the host machine, hence the terms HAM (Host Assisted Modulation) or HSP

Host Signal Processing

Host Signal Processing is a term used in computing to describe hardware such as a modem or printer which is emulated in software. Intel uses the term Native Signal Processing...

(Host Signal Processing). Many of the latest softmodem chipsets, e.g., the Intel Ambient, are even built around a standard AC'97 audio codec interface.

Software & Soundcard projects

The first softmodem-related announcements were made by Motorola

Motorola

, Intel and other companies, back in 1997, claiming that an ordinary sound card and some CPU power would be enough to emulate the functionality of an actual modem, although "sound card telephone adapters" and related software was never released or at least never caught on.

Reasons for that might have been the lack of standardized and fully functional audio card standards by 1997 (AC'97 was not standardized yet, and most sound cards were partially functioning "Soundblaster clones" which lacked even full duplex capabilities) and the lack of CPU power on entry-level PC's.

The approach of using a standard sound card

Sound card

was used by an experimental open-source 96 kbit/s leased-line softmodem called AuDSL in 1999.

Winmodem as a brand name

"Winmodem" is a U.S. Robotics

U.S. Robotics

brand name, but the term has now come to mean any software-based modem, in the same way that Xerox

Xerox

Xerox Corporation is an American multinational document management corporation that produced and sells a range of color and black-and-white printers, multifunction systems, photo copiers, digital production printing presses, and related consulting services and supplies...

refers to any copy machine in some parts of the world. , U.S. Robotics no longer uses "Winmodem" as a brand of modem. Instead, they use the term generically for modems that are controllerless but retain all other modem functions in hardware; this happens to include all of their current branded modems that are not full-hardware modems. This should not be seen as legal abandonment of the "Winmodem" brand name.

The term linmodem is often used to denote a winmodem with support for Linux

Linux

. It should also be noted that Lucent used the name "Win Modem" for certain controllerless chipsets.

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Evolution and technology

Advantages

Disadvantages

Categories

DSL softmodems

General description

Software & Soundcard projects

Winmodem as a brand name

External links