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By contrast, Comtech EF Data's DVB-CID provides you with the interference source's
identification information within seconds. Once you identify the offending carrier, you may then
contact the uplinking station and request that the station shut down or otherwise remove the
identified transmission from service.
D.3
Functional Description
In a typical network, there can be many CDM-425 Advanced Satellite Modems with DVB-CID,
and one (or more) MCDD-100 MetaCarrier Detection Devices to verify the presence of the DVB-
CID on each carrier. In an interference situation, the MCDD-100 may be used to decode the
DVB-CID of an interfering carrier that may not be part of one's own transmission network, as long
as the interfering carrier has an embedded DVB-CID.
The CDM-425 Advanced Satellite Modem creates a composite carrier by first sizing the
appropriate MetaCarrier, and then by adding the spread spectrum CID (at a highly reduced power
spectral density compared with that of the host carrier).
The size of the MetaCarrier is determined based purely on symbol rate and is totally independent
of modulation and coding, resulting in two (2) discrete sizes of MetaCarrier being combined with
the host carrier. The MetaCarrier parameters are shown below:
Host Carrier
128 ksps to < 512 ksps
512 ksps to < 2048 ksps
2048 ksps to < 4096 ksps
4096 ksps to < 8192 ksps
8192 ksps to 12500 ksps
*kchips per sec refers to the direct sequence spread spectrum chipping rate
As shown here, the bandwidth of the host carrier is always wider than the MetaCarrier, the worst
case being a 112 kcps MetaCarrier underneath a 128 ksps host carrier. In all configurations of the
combined carrier, the MetaCarrier raises the transmission power less than 0.1 dB above the
original carrier.
Note that in accordance with the DVB specification, Carrier ID is only available
when the Transmit symbol rate is greater than, or equal to 128 ksps.
The CID message is composed of the following information:
•
CDM-425 Advanced Satellite Modem MAC Address
•
Contact Telephone number
•
Latitude and Longitude
•
Custom message
Appendix D
Embedded DVB-CID MetaCarrier
112 kchips per sec *
224 kchips per sec
224 kchips per sec
224 kchips per sec
224 kchips per sec
D–2
CDM-425 Advanced Satellite Modem
DVB-CID psd relative to host carrier
psd
-27.5 dB
-27.5 dB
-24.5 dB
-21.5 dB
-18.5 dB
MN-CDM-425
Revision 0
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