Cisco MC16S Manual de usuario descargar pdf (Pagina 9)

Two-Way Cable

Cisco uBR7200 Series MC16S Cable Modem Card Spectrum Management 9

The system will not hop endlessly, because one cable modem is generating 90% of the errors and

90% of the trafﬁc.

If the CMTS does not receive two polls in a row, it will signal a frequency hop. A single modem

missing two polls in a row counts as 10% missed polls. The CMTS polls all modems sequentially.

It waits for 20 seconds. If it misses two polls in a row again, it frequency hops again. This pattern is

repeated.

Note Regardless of the number of missed polls during the 20 second hop threshold time, it will not

hop again thus preventing endless frequency hopping.

The default threshold of 100% can be modiﬁed using the following IOS global conﬁguration

command:

cable spectrum-group {1|2|3|...|32} frequency hop threshold {1|2|3|...|100}

The percentage threshold method prevents a single failing cable modem from affecting service to

other good cable modems. To prevent excessive frequency hop, the minimum period between hops

can be changed from the default value of 300 seconds using the following Cisco IOS global

conﬁguration command.

cable spectrum-group {1|2|3|...|32} frequency hop period {1|2|3|...|3600}

If the destination channel is expected to be impaired, then the frequency hop period threshold can be

reduced to a small value such as 10 seconds. This allows the frequency hop to continue more rapidly

until a clear channel is found.

The current implementation is known as blind frequency hop because there is no “look-ahead”

mechanism. In this case, the search time is 0 seconds and the switching time is 20 ms.

Upstream Physical Layer Conﬁguration

The upstream port becomes “up” when it is assigned an upstream frequency and it is conﬁgured to

be administratively up. Conﬁguring a spectrum group enables frequency agility and disables the

ﬁxed upstream frequency setting.

Note Frequency assignment is independent of the conﬁgured shutdown state. A conﬁgured no

cable upstream n shutdown places the port in the “adminup” state. If cable upstream n shutdown

is conﬁgured and no frequency assigned, then the port transitions to the “down” state.

Global Conﬁguration

A maximum of 32 spectrum groups can be conﬁgured in the system. Conﬁguring a spectrum group

allows the upstream frequency and input power level to change whenever noise impairs upstream

data trafﬁc.

cable spectrum-group

groupnum

[ time

day hh:mm:ss

] [delete]

frequency

ctr-freq-hz power-level-dBmV

cable spectrum-group

groupnum

[ time

day hh:mm:ss

] [delete]

band

start-freq-hz end-freq-hz power-level-dBmV

groupnum

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 33 34

Comentarios a estos manuales

Sin comentarios

Cisco MC16S Manual de usuario Pagina 9

Comentarios a estos manuales

Relacionado con productos y manuales para Redes Cisco MC16S