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ADC Telecommunications, Inc.
418 C
HAPTER 18: CONFIGURING CABLE MODEM TERMINATION SYSTEMS
Defining Modulation Profiles
Modulation profiles contain the profile properties of the CMTS upstream
data stream channels. The CMTS supports two profiles for the four upstream
channels. Each profile consists of a burst descriptor for the following Interval
Usage Codes:
■ Request: Interval when a request on bandwidth can be sent by the
modem.
■ Initial Maintenance: Interval when new modems can start establishing a
connection with CMTS with Initial Ranging Requests.
■ Station Maintenance: Interval when modems perform periodic ranging
with periodic ranging for adjusting power, timing and frequency.
■ Short Data: Interval when a modem can send upstream PDU (Protocol
Data Unit), which is less than one maximum burst size.
■ Long Data: Interval when the modem can send upstream PDU, when
one burst size exceeds one maximum burst size on the short data interval.
For each above-mentioned Usage Code, you must define eleven profile
parameters as described in the following sections.
Caution: Profiles affect the physical layer. Changes to profile properties
affects the performance and function of the CMTS. It is recommended that
an expert-level user perform Modulation Profile configuration.
Guard Time
The Guard Time parameter is the number of symbol-times that must follow
the end of this channel's burst. Note that this parameter is read-only.