Comtech EF Data CDM-570AL - Functional Description

CDM-570A/570AL Satellite Modem with Optional Packet Processor
Revision 5
Carrier ID (DVB-CID MetaCarrier) R–2 MN-CDM570A
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.
R.3 Functional Description
In a typical network, there can be many CDM-570A/570ALs 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-570A/570AL 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 Embedded DVB-CID MetaCarrier DVB-CID psd relative to host carrier psd
128 ksps to < 512 ksps
112 kchips per sec *
-27.5 dB
512 ksps to < 2048 ksps 224 kchips per sec -27.5 dB
2048 ksps to < 4096 ksps 224 kchips per sec -24.5 dB
4096 ksps to < 8192 ksps 224 kchips per sec -21.5 dB
8192 ksps to 12500 ksps 224 kchips per sec -18.5 dB
*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-570A/570AL MAC Address
• Latitude and Longitude
• Contact Telephone Number
• Custom Message