User's Manual

05-4446A01, Rev. C Mercury Reference Manual 67
For example, the third SNR value in Column D is 11.4 dB (8.4 + 3 =
11.4 dB), and the third SNR value in Column E is 17.1 (11.1 + 3 + 3 =
17.1 dB). Note that with a Hysteresis Margin of 3 dB, there is an overlap
of 3 between the Max SNR of one modulation and the Min SNR of the
next higher modulation.
In this case, if a link is operating with an SNR of 15 dB, then QPSK-3/4
modulation is used. The SNR must go above 17.1 dB before the link
shifts up to 16QAM-1/2 modulation. Conversely, the SNR will need to
drop below 11.4 dB before the link shifts down to QPSK-1/2.
The blank entries (--) in the table indicate infinite SNR (i.e., the top of
the range). For example, in columns B and C, 64QAM-3/4 modulation
is used for all SNR values from 20 dB and up.
3.5.2 Serial Port Configuration
Overview
The transceiver includes an embedded serial device server that provides
transparent encapsulation over IP. In this capacity, it acts as a gateway
between serial and IP devices. Two common scenarios are PC applica-
tions using IP to talk to remote devices, and serial PC applications
talking to remote serial devices over an IP network. These data services
are available from the COM1 port of the radio.
COM1 Port–Dual
Purpose Capability
The COM1 port is used as a local console connection point and to pass
serial data with an external device. Setting the COM1 port status to Enable
prevents access to the Management System (MS) through this port.
However, the MS can still be accessed via the LAN port using Telnet or
a web browser.
Table 3-3. Adaptive Modulation Protection and Hysteresis Margins
A B C D E F G
Protection 0 Protection 3 Protection 5
Hysteresis 0 Hysteresis 3 Hysteresis 3
Min SNR Max SNR Min SNR Max SNR Min SNR Max SNR
BPSK 3.3 5.8 3.3 11.8 3.3 13.8
QPSK-1/2 5.8 8.4 8.8 14.4 10.8 16.4
QPSK-3/4 8.4 11.1 11.4 17.1 13.4 19.1
16QAM-1/2 11.1 14.4 14.1 20.4 16.1 22.4
16QAM-3/4 14.4 18.4 17.4 24.4 19.4 26.4
64QAM-2/3 18.4 20 21.4 26 23.4 28
64QAM-3/4 20 -- 23 -- 25 --