System information

Configuring the CMTS
6-61
Configuring a Spectrum Group
Each spectrum group contains spectrum data, a spectrum map, and channel
assignment:
• The spectrum data is where the collected spectrum noise information is kept. It
contains the starting frequency, resolution, number of data points, time of the last
measurement, and a pointer to an array where the noise level is kept.
• The spectrum map describes the way the upstream spectrum is used for a
particular band. It contains the start and stop frequency, and the current status.
• The channel assignment defines the frequency allocation of the upstream channel.
Each spectrum group also contains the following management information:
• Spectrum signal quality information is collected through the spectrum monitoring
process. This information contains the periodic error rate that is computed and
compared with the Forward Error Correction (FEC) error threshold to determine
if spectrum hopping is necessary, and the periodic combination of in-band power
and spectrum data collection to compute signal-to-noise ratio (SNR) for the
upstream channel.
• The spectrum schedule contains information on the availability of a certain
frequency band. The band can be made available statically, or available only at
certain time period(s). The actual available spectrum is the super set of all the
bands that are available at the time.
• Spectrum hopping rules determine the action taken when the spectrum manager
decides to change the parameters of an upstream channel to combat noise.
Operators can improve upstream channel conditions to combat ingress noise by
specifying hopping rules for upstream frequency changes, upstream frequency
band changes, modulation profile changes, channel-width reduction (until
channel conditions improve), and power adjustments (if it is necessary).
Note: The term "upstream channel" is synonymous to the term "upstream
port".