Implementation of wideband VoIP middleware using embedded systems

摘要

Current Analog Telephone Adaptors (ATA) which are commonly used by small business and home offices to implement Internet telephony applications are designed to work with an audio bandwidth of 300 Hz to 3.4 KHz, a holdover from the one hundred year history of telephone companies trying to accommodate a high volume of calls over copper. Recent network improvements in the last decade allow for a wider bandwidth. However, existing work in wideband audio for telephony has been mainly focused either on mobile telephony or high end teleconferencing equipment but not on ATA devices. This paper proposes improvements to ATA devices that allow an audio bandwidth of 50 Hz to 7 KHz. An implementation is discussed where a minimal upgrade to an open source ATA based on GPL licensed hardware is modified to support wideband, and a middleware layer software is modified to also handle the wider bandwidth. Moreover, promising results when using the modified hardware and software were obtained. The results indicated that with slight CPU overloading, the modified hardware and software can be used for wideband telephony.