Comtech EF Data MCED-100 - Manual (Page 21)

MCED-100 MetaCarrier Embedding Device Revision 1
Introduction MN-MCED100
1–3
The entire CID message is broken into 18 packets containing 122 bits (formatting, FEC and user
information) for a total message length of 2,196 bits for the transmission of the MetaCarrier.
Each packet of the MetaCarrier message carries 32 bits of CID information data. However, the
MAC address is sent at a higher rate (more often), so that upon reception of a frame that is
comprised of three (3) packets, the MAC address may be obtained.
The data rate of messages being carried in the MetaCarrier is shown before spreading is applied
and the associated time to send a complete CID message (including the framing and FEC). The
time for a complete message is only valid once the MCDD‐100 has achieved lock to the
MetaCarrier which may cause the stated times to be longer:
Embedded MetaCarrier CID Data Rate Time for Complete Message
224 kcps 56 bps 41.0 seconds
112 kcps 28 bps 82.0 seconds
Therefore, the time for the MCED‐100 to insert a complete CID ID sequence is as follows. Note
that the time for unique ID may be shorter than shown, since upon achieving lock to the
MetaCarrier, the unique ID is immediately made available, since MetaCarrier lock requires the
reception of three full packets to declare lock:
Embedded MetaCarrier CID Data Rate Time for Unique ID
224 kcps 56 bps 6.9 seconds
112 kcps 28 bps 13.8 seconds
The MCED‐100 provides fail‐safe embedding of the MetaCarrier by passively coupling the CID onto
the transmission such that the transmission path remains unbroken in the event the MCED‐100
fails, loses power, or is turned off.
Changes to the MCED‐100’s configuration are typically not required. However, when
characteristics of the transmission carrier (e.g., frequency, symbol rate, modulation) are
changed, the MCED‐100 must be forced to re‐analyze the uplink carrier. This can be performed
in three ways:
1. Disable, Reconfigure, Re‐enable Carrier Transmission – Turn the transmit carrier off,
reconfigure the carrier, and then turn the carrier back on.
Most satellite modems will automatically turn the carrier off while carrier
parameters such as frequency or symbol rate are being changed, and
then automatically turn the carrier back on. Some modems, however,
will execute these steps faster than the MCED-100 can detect the loss of
transmit carrier power and return to the carrier detect mode. To ensure
reacquisition of the new transmission carrier, force the carrier off for a
minimum of two seconds.
2. Perform a “soft” reboot of the MCED‐100 – Reboot the unit via the MCED‐100 HTTP
Web Server Interface ‘UTILITY | REBOOT’ or ‘ADMIN | FIRMWARE’ pages.