| 摘要 |
A system and method for locating ingress noise gaps for an upstream data carrier in a cable network utilizing cable modems is described. A system for identifying a transmission frequency that has less noise than other available frequency bands includes a packet generator, a rate controller, an echo device, a demodulator, and a packet checker. The packet generator and rate controller, contained in a cable modem termination system, send test data downstream to the echo device which then redirects the test data upstream at a selected test frequency. The echo device, which may be located within the cable modem termination system or outside the termination system, listens on the downstream path for data packets addressed to it. Once received, the echo changes the address of the test data to the address of the packet checker. The packet checker then receives and analyzes the test data packet sent from the echo device to assess the amount of noise on that particular test frequency. The echo device can be a subscriber cable data modem configured to receive test packets sent downstream or a custom-built device located anywhere on the downstream path or within the cable modem termination system.
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