Cisco Prisma II bdr Dig Rev 2 1 Dual Mux Sys for High Density Installations Installation Guide
Introduction
As services become more numerous and take rates increase for these services, the
upstream spectrum becomes increasingly crowded. Meanwhile, more downstream
content continues to demand additional resources from the plant as well. The result
is a strain on transport capacity. It is cost prohibitive to add fiber to achieve more
capacity by increasing fiber count. An alternative is to more effectively use the
capacity available.
upstream spectrum becomes increasingly crowded. Meanwhile, more downstream
content continues to demand additional resources from the plant as well. The result
is a strain on transport capacity. It is cost prohibitive to add fiber to achieve more
capacity by increasing fiber count. An alternative is to more effectively use the
capacity available.
As services become more accepted, penetration rates have increased, creating a
higher level of traffic in the upstream path. Additionally, new services such as
telephony are rich in upstream data requirements, further exacerbating the situation.
higher level of traffic in the upstream path. Additionally, new services such as
telephony are rich in upstream data requirements, further exacerbating the situation.
System Impacts
System operators are looking for ways to reduce the size of home pockets served by
each reverse path signal. Options open to them are segmenting existing nodes or
replacing them with multiple nodes deeper in the network, either of which requires
additional fiber capacity. DOCSIS 1.1 provides some relief with the freedom to use
additional frequencies in the reverse spectrum, allowing more spectrum to carry
payload signals. Still, the need for more reverse path capacity in each fiber remains.
each reverse path signal. Options open to them are segmenting existing nodes or
replacing them with multiple nodes deeper in the network, either of which requires
additional fiber capacity. DOCSIS 1.1 provides some relief with the freedom to use
additional frequencies in the reverse spectrum, allowing more spectrum to carry
payload signals. Still, the need for more reverse path capacity in each fiber remains.
We present in this paper a significant advance in the carrying capacity of reverse
path traffic over a fiber link. With advanced digital signal processing algorithms, a
single wavelength can transport up to four separate individual reverse path signals,
fully recovered and separable at the headend. This represents up to 140 MHz of
useable bandwidth from a single node. Previous attempts to provide this level of
performance have proven unfeasible. Sacrificing performance by sampling and
transporting with fewer bits of information resulted in unacceptably low
performance. The option of increasing the bit rate of the transport to 5 Gbps results
in an inordinate cost increase. The 4:1 digital transport provides increased capacity
with little, if any, performance penalty and a much lower price than other options.
path traffic over a fiber link. With advanced digital signal processing algorithms, a
single wavelength can transport up to four separate individual reverse path signals,
fully recovered and separable at the headend. This represents up to 140 MHz of
useable bandwidth from a single node. Previous attempts to provide this level of
performance have proven unfeasible. Sacrificing performance by sampling and
transporting with fewer bits of information resulted in unacceptably low
performance. The option of increasing the bit rate of the transport to 5 Gbps results
in an inordinate cost increase. The 4:1 digital transport provides increased capacity
with little, if any, performance penalty and a much lower price than other options.
4:1 TDM digital transport doubles the capacity of optical spectrum over 2:1
digital transport systems and quadruples the capacity of standard analog
transport.
transport.
In this paper, we will first describe the process we use to reduce the amount of bits
required to be transported, enabling the low cost transport of 4:1 time division
multiplex (TDM) signals. We will then discuss the concept of NPR performance
benchmarks and why traditional views of NPR may be misleading when trying to
fully understand the performance of digital transport technologies in a realistic
system. Finally, we will discuss the implications to a typical system architecture to
show a realistic expectation of performance using 4:1 bdr
required to be transported, enabling the low cost transport of 4:1 time division
multiplex (TDM) signals. We will then discuss the concept of NPR performance
benchmarks and why traditional views of NPR may be misleading when trying to
fully understand the performance of digital transport technologies in a realistic
system. Finally, we will discuss the implications to a typical system architecture to
show a realistic expectation of performance using 4:1 bdr
™
technology.
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Improving the Performance and Capacity of Digital Reverse Systems
4000819 Rev B