Speech and data multiplexor optimized for use over impaired and bandwidth restricted analog channels
US4757495A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 5, 1986 |
| Grant date | Jul 12, 1988 |
| Priority date | — |
| Expiry date | Mar 5, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L5/0053
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
The present invention relates to an apparatus and method for the simultaneous transmission of analog speech and modulated data, such apparatus and method being optimized for use over impaired and bandwidth restricted analog channels, or digital representations of such channels. In each instance of use, an evaluation is made of the available channel bandwidth, with a frequency division multiplex scheme allocating a voice sub-band, with data transmission allocated to sub-bands above, below, or around, this selected voice sub-band. The speech and data sub-band allocations are made by the multiplexor in response to user input of either a requested speech quality, a requested data rate, or a value indicating the relative user weighting of speech quality and data rate. A multi-carrier multi-mode modulation scheme is employed for data transmission, with this scheme having the ability to fully utilize the remaining bandwidth, and further, being capable of adapting to the impairments most likely present on the fringes of bandwidth restricted analog channels. When the analog channel employed is the standard voice-grade telephone circuit, good speech quality simultaneously with 3000 bps data …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.