Detection of duplicate participants in a two-way modem environment
US7006446B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Jan 14, 2000 |
| Grant date | Feb 28, 2006 |
| Priority date | — |
| Expiry date | Jan 14, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2463/101
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Duplicate participants (e.g., cloned subscriber units) (274) are detected in a communication network, such as a hybrid fiber/coax (HFC) cable television network or the like, by monitoring the physical layer of the network to detect transmission differences between such units. The subscriber units (14, 16, 18, 274, 276) may be cable modems that transmit upstream signals with associated identifiers to a headend (10, 200), e.g., to access the Internet or for telephony. Measured characteristics of the upstream signals can include: (1) propagation time (235), (2) frequency (240), (3) power (245), and (4) spectral characteristics (250). For propagation time, the reception time of the upstream message can be compared to a headend clock (215) and also to other messages with the same modem ID. For spectral characteristics, adjustment coefficients can be provided to the units to normalize the spectrum of the upstream signal to a baseline spectrum. When discrepancies are detected for an upstream signal that indicate duplicate modems are operating in the network, the account of the corresponding unit can be terminated.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.