User's Manual

ARCXTEND USER MANUAL – R1.4, ISSUE 4
Copyright 2005 Arcwave, Inc. 20
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CATV Plant
ARCXtend
Subscriber
Transceiver
Cable Modem
ARCXtend
Hub
Transceiver
CATV Upstream
Frequency
5 MHz - 42 MHz
ARCXtend Air Frequency
5258 MHz - 5342 MHz
CM Transmit
Frequency
5 MHz - 42 MHz
LAN or USB
frequency may be different than the cable modem receive frequency. This is generally not a
concern as most DOCSIS systems on which there is only one DOCSIS downstream channel on the
cable network do not specify the CM receive frequency in the CM configuration file, rather they let
the CM find the downstream on its own.
Upstream Configuration
The ARCXtend upstream block diagram is illustrated in Figure 4-2. Note that the North American
DOCSIS (Version 1.0 and 1.1) QPSK or QAM upstream signal is up to 3.2 MHz wide. DOCSIS 2.0
upstream signals can be as much as 6.4 MHz wide. All frequencies specified in this section are the
center frequency of the particular signal.
Figure 3-4: ARCXtend Upstream Block Diagram
Upstream Block Diagram
The cable modem (CM) is commanded by the downstream signal to transmit at a specific upstream
frequency between 5 MHz and 42 MHz. Note that any upstream frequency may be selected.
Refer to Figure 3-4 from right to left. The ARCXtend Subscriber Transceiver (CPE) up converts the
CM upstream signal to the 5300 MHz band and transmits two copies of the signal: 5300 MHz-[CM
transmit frequency] and 5300 MHz+[CM transmit frequency].
For example, if the CM upstream transmits frequency is 22.5 MHz; the ARCXtend CPE will
simultaneously transmit the signal on two air frequencies: 5277.5 MHz and 5322.5 MHz.
In summary, the CM upstream transmit frequency determines the two upstream air frequencies
transmitted by the ARCXtend CPE. The ARCXtend Hub selects either the high or low air frequency
and passes the user data upstream to the CATV plant at the original CM transmit frequency.