DOCSIS 2.0 SCDMA capable sniffers which can capture legacy DOCSIS bursts as well

Abstract

A DOCSIS 2.0 compatible sniffer which can receive legacy DOCSIS 1.x TDMA bursts as well as DOCSIS 2.0 SCDMA bursts. One embodiment uses two cable modems in the sniffer, one to capture downstream data bursts and the other to capture downstream messages and to recover the downstream symbol clock and generate an upstream reference clock which is phase coherent with the recovered downstream symbol clock. The reference clock is used by a cable modem termination system to capture upstream SCDMA DOCSIS 2.0 bursts. DOCSIS 1.x TDMA bursts may also be captured. Other embodiments use a DOCSIS 2.0 compatible modem in the sniffer to lock onto a downstream, register as a cable modem in the system and capture downstream messages in order to derive the correct timing to generate control signals to control burst capture circuitry in the sniffer to capture DOCSIS 1.x and 2.0 upstream bursts. The digital samples of each burst can be sent digitally to the CMTS under test after some fixed delay or can be sent to the CMTS under test as an analog RF signal in repeater embodiments. This allows the CMTS under test to be simplified by pushing the burst capture circuitry out to the optical node.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. patent application Ser. No. 10 / 397,508, filed on Mar. 25, 2003, entitled “DOCSIS 2.0 SCDMA Capable Sniffers Which Can Capture Legacy DOCSIS Bursts As Well”.BACKGROUND OF THE INVENTION [0002] In cable modem systems, there is a need to be able to debug by capturing message and burst traffic in the upstream and downstream directions. In DOCSIS systems, there is a need to be able to capture all the data bursts, MAP and UCD messages, timestamp data, ranging request messages, ranging bursts, ranging response messages and all the other DOCSIS messages. [0003] Sniffers exist in the prior art. A DOCSIS traffic sniffer manufactured by Filtronic-Sigtek, Inc. (model number ST260B) can captures data bursts and message traffic in DOCSIS 1.0 and 1.1 systems. However, DOCSIS 2.0 systems include the ability to send spread spectrum bursts, and the Filtronic sniffer cannot capture and demodulate spread spectrum bur...

AI Technical Summary

Benefits of technology

The patent describes two types of sniffers, or devices used to capture data from cable modems. The first type uses a modified cable modem to capture downstream bursts and messages. The second type uses a slightly different cable modem to capture both downstream and upstream bursts. The sniffers have a linecard that includes a computer programmed to process the data and control the device. The captured data is used to synchronize the device with the cable modems and to determine the burst parameters. The technical effects of the patent are improved synchronization and more accurate burst capture for testing and analysis of cable modems.

Problems solved by technology

However, DOCSIS 2.0 systems include the ability to send spread spectrum bursts, and the Filtronic sniffer cannot capture and demodulate spread spectrum bursts and time division multiplexed bursts at symbol rates faster than symbol rates of DOCSIS 1.0 and 1.1 systems.

Conventional sniffers today are too complicated.

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