Cisco WCM300 - Channel Bonded Cable Modem Implementation Manual page 27

Chapter 2 Cisco Cable Wideband Components
External Edge QAM Device
The Cisco wideband CMTS uses one or more external edge QAM (EQAM) devices. The EQAM device
is a network element in a separate chassis from the CMTS. The EQAM device has two or more Gigabit
Ethernet input interfaces that connect to a Wideband SPA. For output, the EQAM device has multiple
QAM modulators and RF upconverters that connect to a hybrid fiber coaxial (HFC) network. The edge
QAM device accepts MPEG over IP on its Gigabit Ethernet interfaces and routes the services to its QAM
RF outputs.
The following edge QAM devices have been tested for interoperability with other Cisco Cable Wideband
Solution, Release 1.0, components:
•
•
•
•
Table 2-5
Table 2-5
EQAM Device
Scientific Atlanta Continuum DVP XDQA24
Harmonic NSG 9116
Harmonic NSG 9000
Vecima Networks VistaLynx VL1000
Number of EQAM Devices Required
Each logical RF channel defined on the Wideband SPA must have one corresponding output QAM
channel on an EQAM device. The number of EQAM devices required is determined by two factors:
•
•
As an example, if a Cisco uBR10012 router (CMTS) contains two Wideband SPAs and each Wideband
SPA is configured for 18 RF channels, the total number of RF channels that are in use is 36. Therefore,
36 output QAM channels are required on the EQAM devices. This requirement for output QAM channels
could be met by deploying, for example, two DVP XDQA24 EQAMs (with 48 total QAMs) or three NSG
9116 EQAMs (with 48 total QAMs).
If more than two EQAM devices are required for two Wideband SPAs, a Gigabit Ethernet switch is
needed to connect the SPAs to the EQAM devices.
OL-10705-02
Scientific Atlanta Continuum DVP XDQA24, page 2-12
Harmonic NSG 9116, page 2-12
Harmonic NSG 9000, page 2-12
Vecima Networks VistaLynx VL1000, page 2-13
lists the number of output QAM channels supported by each edge QAM device.
EQAM Devices: Number of Output QAM Channels Supported
The number of logical RF channels in use on the Wideband SPAs in the CMTS. Each Wideband SPA
supports up to 24 logical RF channels depending on how it is configured.
– For annex A and 256 QAM, each Wideband SPA supports 18 RF channels.
For all other cases, each Wideband SPA supports 24 RF channels.
–
The number of output QAM channels on the EQAM device. See
Cisco Cable Wideband Solution Design and Implementation Guide, Release 1.0
Wideband CMTS Components
Number of Output QAM Channels Supported
scalable up to 24 QAM channels
16 QAM channels
scalable up to 72 QAM channels
scalable up to 24 QAM channels
Table 2-5.
2-11