Softmodem

The first generations of hardware modems (including acoustic couplers) and their protocols used relatively simple modulation techniques such as FSK or ASK at low speeds.

New modulation required mixing analog and digital components, and eventually incorporating multiple integrated circuits (ICs) such as logical gates, PLLs and microcontrollers.

Later techniques used in modern V.34, V.90 and V.92 protocols (such as a 1664-point QAM constellation) are so complex that implementing them with discrete components or general purpose ICs became impractical.

Furthermore, improved compression and error correction schemes were introduced in the newest protocols, requiring extra processing power in the modem itself.

Initially the solution was to use LSI ASICs which shrank the various implementations into a small number of components, but since standards continued to change, there was a desire to create modems that could be upgraded.

Since then, some softmodems have been created as standalone software projects utilizing standard sound card interfaces, such as an experimental open-source 96 kbit/s leased-line softmodem called AuDSL from 1999,[6] and the Minimodem project which implements several FSK modem standards.

[5] The original stated purpose of the DSP-based softmodem was to provide for upgradeability, a concern in an era when modem standards were changing rapidly.