Dual mode phone line networking modem utilizing conventional telephone wiring
US6744812B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 6, 2002 |
| Grant date | Jun 1, 2004 |
| Priority date | — |
| Expiry date | Dec 6, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2027/0073
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A networking modem capable of full duplex communication over a telephone line is adapted for use as a component of a computer system. The modem comprises a digital signal processor (DSP) capable of implementing a plurality of digital modulation and demodulation techniques, including pulse position modulation (PPM), quadrature phase shift keying (QPSK), and quadrature amplitude modulation (QAM). The DSP implements a digital phase locked loop (DPLL), including a carrier NCO and a carrier detector to synchronize local demodulation timing to an incoming carrier signal. Available processing options include spectral agility for optimizing channel capacity, symbol shaping to compensate for evolving channel conditions, and echo cancellation. The digital processing provides a flexible, adaptive, programmable, and backward compatible solution to eliminate various problems with prior art systems, including timing inaccuracies, incompatibility with standard modulation techniques, the half duplex limitation, and the susceptibility to noise that increases intersymbol interference and limits throughput.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.