PLC Settings (DOCSIS 4.0 Downstream)

PLC Settings contains a group of parameters to automatically or manually control Physical-layer Link Channel properties.

The DocsisFastDetection macro makes setting up the demodulator faster and easier by automating the process of detecting and applying the input signal's PLC information.

Parameter	Description
Automatic	When selected, the demodulation is automatically configured with the information detected from the Physical-layer Link Channel (PLC). Default: Automatic When Initial Settings = Manual and PLC Settings = Automatic, the User Profiles section of the Format tab is active and user-specified Profiles B-P are used by the demod, but any Profile A and NCP specified by the user is ignored. BER analysis is not supported for for 8192-QAM and 16384-QAM modulation. In Automatic mode, if 8192-QAM or 16384-QAM modulation is detected and BER Analysis radio button is selected (enabled), the VSA software will deselect BER Analysis and continue the measurement with MER only.
Manual	When selected, set the parameters to manually configure the Physical-layer Link Channel. When Manual is selected, Initial Settings is also set to Manual. BER analysis is not supported for for 8192-QAM and 16384-QAM modulation. In Manual mode, if 8192-QAM or 16384-QAM modulation is used in a profile, uncheck (disable) the BER Analysis radio button to avoid a warning message and validation process failure.
	Time Interleaving Depth: Set the depth (number of symbols) used for time interleaving. Default: 4096 Range: 4096, 8192
	Rolloff Period: Select the time-domain windowing between symbols. This property specifies how much time-domain windowing the transmitter used between symbols. Normally, a transmitter will do this windowing to smooth the discontinuity between OFDM symbols, to reduce the spectral leakage outside the nominal signal bandwidth. Default: 5.0 us Range: 0.9375 us, 1.25 us, 2.5 us, 3.75 us, 5.0 us
	Continuous Pilots: Defines the list of continuous pilot subcarrier locations. The format is a comma-separated string. Each number represents a subcarrier location. The software checks the validity of the string and reports a validation message directly below the Continuous Pilots field.
	Exclusion Bands: Defines the list of exclusion bands. An exclusion band defines the inactive subcarriers in a DOCSIS signal. The format is a comma-separated list of numbers. Each number represents a subcarrier location. Each pair of numbers represents the lower and upper edges of an exclusion band. For example: 0,1200,1500,1600,3200,4095 indicates that subcarriers 0 through 1200, 1500 through 1600, and 3200 through 4095 are not active subcarriers.
User Profiles	Profile IDs: Sets the Profile IDs that correspond to the Modulation Assignments. The format is a comma-separated list of numbers. Each number is a profile ID (Profiles A-P = 0-15, NCP = 255). For each number in this list, there should be (FFT Length) entries in the Modulation Assignments list. The order of the Profile ID list corresponds to the sections in the Modulation Assignments list. Modulation Assignments: Sets the modulation order for each subcarrier in each profile. The format is a comma-separated list of numbers. Each entry in the Modulation Assignments list corresponds to a subcarrier in the OFDM symbol. The value is the power of 2, so 4 = 16-QAM, 12 = 4096-QAM. A value of nothing or -999 means “not assigned.” The subcarriers are listed starting at the lowest subcarrier in frequency. The Modulation Assignments apply to all symbols. The following modulation formats are supported: Supported: BPSK, 16-QAM, and 64-QAM to 16384-QAM Not Supported: QPSK (Except for NCP) and 32-QAM User Profile Editor: Sets Profile IDs and Modulation Assignments in a user-friendly editor. For each profile (Profiles A-P = 0-15 in the Profile IDs field, NCP = 255), a corresponding drop-down selects a modulation format. Click Apply to apply the changes to the Profile IDs and Modulation Assignments fields. See the User Profile Editor topic for more information.