Cisco UBR7225VXR, Руководство по установке оборудования

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B-1
Cisco uBR7225VXR Universal Broadband Router Hardware Installation Guide
OL-17309-01
A P P E N D I X
B
RF Specifications
Information in the following tables is from the DOCSIS and EuroDOCSIS Radio Frequency Interface
Specification, and should be considered minimum recommended performance criteria for reliable data
transmission on cable networks. The full specification may be found at the CableLabs website
(
http://www.cablemodem.com ), and additional Euro-DOCSIS information may be found at ComLabs
website ( http://www.tcomlabs.com ).
•
NCTA—“NCTA Recommended Practices for Measurements on Cable Television Systems, 2nd
Edition”- National Cable Television Association, Washington DC, revised October 1993
• CableLabs1—“Two-Way Cable Television System Characterization,” Cable Television
Laboratories, Inc., April 12, 1995
•
CableLabs2—“Digital Transmission Characterization of Cable Television Systems,” Cable
Television Laboratories, Inc., November, 1999
Note
Raw data rate in Table B-1 and Table B-2 includes nominal data throughput plus overhead.
Table B-1 Downstream Channel Data Rates
Modulation Format
Channel
Bandwidth, MHz Symbol Rate,
Msym/sec Raw Data Rate,
Mbps Nominal Data
Rate, Mbps
QAM-64 6 5.056941 30.34 ~27
QAM-256 6 5.360537 42.88 ~38
QAM-64 8 6.952 41.71 ~37
QAM-256 8 6.952 55.62 ~50
Table B-2 Upstream Channel Data Rates
Symbol Rate,
ksym/sec
Channel
Bandwidth,
MHz QPSK Raw
Data Rate,
Mbps QPSK Nominal
Data Rate,
Mbps QAM-16 Raw
Data Rate,
Mbps QAM-16
Nominal Data
Rate, Mbps
160 0.20 0.32 ~0.3 0.64 ~0.6
320 0.40 0.64 ~0.6 1.28 ~1.2
640 0.80 1.28 ~1.2 2.56 ~2.3