A period between SNR pollings.
The SNR is collected from the Fast Fourier Transform
(FFT) measurement over the in-use band when there is
no CM signals. When the CMTS detects that SNR doesn't
meet ccsUpSpecMgmtSnrThres1 or ccsUpSpecMgmtSnrThres2,
a possible hopping occurs, depending on the type of
ccsUpSpecMgmtHopPriority.