Cisco Model D-PCG1000 PowerKEY CAS Gateway 技术参考
July 2004
Preventing the Miscalculation of Bandwidth
on the BFS QAMs
on the BFS QAMs
Overview
Introduction
Cisco® engineers have discovered that the qamManager is miscalculating the
bandwidth associated with inband system information (SI) on System Release
(SR) 2.x/3.x. The miscalculation is reserving more bandwidth than is needed. In
instances where there are a large number of hubs in the network, the bandwidth
numbers are significantly high compared with the actual bandwidth being used on
the distinguished quadrature amplitude modulation (QAM) modulator.
Note: The distinguished QAM is typically the BFS QAM.
When large amounts of bandwidth are reported and the system believes that the
Note: The distinguished QAM is typically the BFS QAM.
When large amounts of bandwidth are reported and the system believes that the
QAMs are nearing their maximum limits, data cannot be added to the BFS carousels.
Although we have determined the cause of this miscalculation, the updated software
has not yet been released. In the interim, we encourage all sites using SR 2.x/3.x that
are experiencing problems adding new BFS carousels to disable inband SI, and
therefore eliminate the miscalculation of bandwidth on the BFS QAMs.
When inband distribution of SI is turned off, out-of-band SI is automatically used by
When inband distribution of SI is turned off, out-of-band SI is automatically used by
the Digital Home Communications Terminal (DHCT). Using out-of-band
distribution of SI does not adversely affect your system because the DNCS sends
both inband and out-of-band SI. Therefore, turning off inband SI actually reduces the
amount of work imposed on the DNCS.
Purpose
This technical bulletin assists system operators who are having difficulty adding
data to the BFS carousels as a result of an inaccurate bandwidth calculation.