Cisco Cisco IOS Software Release 12.1(3)EC
Cisco uBR7200 Series Dynamic Upstream Modulation
Command Reference
9
Cisco IOS Release 12.1(3a)EC1
Note
The upstream request and station maintenance messages use less time on the cable
network when configured in QPSK for symbol rates of 640, 1280 and 2560 Ksymbols/sec,
Thus, these messages are actually more efficient when used in QPSK mode and they
ensure a more reliable modem connection. The upstream initial maintenance message
takes exactly the same amount of time on the cable network no matter how it is configured.
Modems will connect more quickly and experience fewer cycles of power-adjustment
during initial maintenance if the system is set for QPSK.
network when configured in QPSK for symbol rates of 640, 1280 and 2560 Ksymbols/sec,
Thus, these messages are actually more efficient when used in QPSK mode and they
ensure a more reliable modem connection. The upstream initial maintenance message
takes exactly the same amount of time on the cable network no matter how it is configured.
Modems will connect more quickly and experience fewer cycles of power-adjustment
during initial maintenance if the system is set for QPSK.
Router# configure terminal
Router(config)# cable modulation-profile 2 request 0 16 1 8 qpsk scrambler
152 no-diff 64 fixed uw8
Router(config)# cable modulation-profile 2 initial 5 34 0 48 qpsk scrambler
152 no-diff 128 fixed uw16
Router(config)# cable modulation-profile 2 station 5 34 0 48 qpsk scrambler
152 no-diff 128 fixed uw16
Router(config)# cable modulation-profile 2 short 6 75 6 8 16qam scrambler 152
no-diff 72 fixed uw8
Router(config)# cable modulation-profile 2 long 8 220 0 8 16qam scrambler 152
no-diff 160 fixed uw8
In the following example, all message types are carried with 16QAM modulation. Although 16QAM
modulation offers a consistent modulation scheme for all five types of messages, the added length of
the 16QAM preamble offsets the increased bandwidth efficiency of the MAC data message for the
station maintenance messages and bandwidth request messages.
modulation offers a consistent modulation scheme for all five types of messages, the added length of
the 16QAM preamble offsets the increased bandwidth efficiency of the MAC data message for the
station maintenance messages and bandwidth request messages.
Router# configure terminal
Router(config)# cable modulation-profile 2 request 0 16 1 8 16qam scrambler
152 no-diff 128 fixed uw16
Router(config)# cable modulation-profile 2 initial 5 34 0 48 16qam
scrambler 152 no-diff 256 fixed uw16
Router(config)# cable modulation-profile 2 station 5 34 0 48 16qam
scrambler 152 no-diff 256 fixed uw16
Router(config)# cable modulation-profile 2 short 5 75 6 8 16qam scrambler
152 no-diff 144 fixed uw8
Router(config)# cable modulation-profile 2 long 8 220 0 8 16qam scrambler
152 no-diff 160 fixed uw8
Add the cable upstream port-number modulation-profile primary profile-number secondary
profile-number command to the appropriate interface(s). In this example, modulation-profile 2 is for
16QAM modulation and profile 1 is for QPSK modulation.
profile-number command to the appropriate interface(s). In this example, modulation-profile 2 is for
16QAM modulation and profile 1 is for QPSK modulation.
Router# configure terminal
Router(config)# interface Cable6/0
Router(config-if)# cable upstream 0 modulation-profile 2 1
Command Reference
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