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Chapter 11 - DOCSIS Analyzer
10713 Vxx.11
DOCSIS Analyzer
Chapter 11
11.1
Introduction
The analyzer of the measuring receiver operates in accordance with specification DOCSIS 3.0 or
DOCSIS 3.1. DOCSIS stands for “Data-Over-Cable Service Interface Specification”. The standard
sets the rules for fast, bi directional communication and IP data exchange between the headend
and the user either via a pure coaxial network or an HFC network (Hybrid Fiber/Coaxial). The
counterpart station for the cable modem (CM) on the user side is the CMTS (Cable Modem
Termination System) in the headend.
Figure 11-1 Communication network
The data from the head end to the customer is transmitted in the so-called downstream (DS);
information returning from the customer is transmitted in the upstream (US). The US and DS are
transmitted in the same cable but in different frequency ranges.
Figure 11-2 Head-end - Modem
With DOCSIS, there are two different specifications: Euro-DOCSIS and US-DOCSIS. You can
measure both standards with the measuring instrument. The differences are in the DS error
protection and the DS channel bandwidths and in the channel spacing and DS and US frequency
range (see chapter 6.2.2 - DIGITAL (DVB-C, DOCSIS) operating mode). The content of the
messages that are exchanged between the head end and the user is identical in both
specifications.
The main extension in DOCSIS3.1 is the additional OFDM-Standard for transmission. The
fundamentals of that are also known from the DVB-T/T2 standard. The maximum downstream
bandwidth is increased up to 192MHz and therefore much bigger than in EU/US-Docsis. Also the
frequency range is increased, so the maximum possible datarate for transmissions are much higher
than in DOCSIS3.0. Further details you can read in the Application Note Docsis-3.1.
