5-2
5.1
WHAT ARE THE PROBLEMS IN ADVANCED
SERVICES?
A.
Noise (Ingress) in Return Path Frequencies
For two-way systems, ingress and noise are far greater problems in
the reverse path than they are in the forward path. The reasons are
fairly straightforward:
Accumulation of Noise means that problems compound far more
quickly than in the forward path. In a forward path network, noise or
interference generated at one point in the network affects everyone
‘downstream’ from the noise source.
F i b e r
Fig. 5-1 Customers Affected by forward Path Ingress Source
In order to limit these problems, hardline and better quality
equipment are used at the upstream connections, and less
expensive equipment is used downstream. In the reverse path
system, however, a noise problem affects everyone in the same ‘leg’
of the network all the way back to the Headend receiver. This
means that the “quality first close to the Headend and cost first close
to the customer” concept no longer works.