Redline Communications AN-50, User Manual

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AN-50 System User Manual
Redline Communications …..solving the first mile challenge .
"power reserve", in which extra power is designed into the link budget to deal with
additional fades arising from such factors as climatic conditions (seasonal), multipath
dispersions, and shadowing effects from natural (foliage) and man-made obstacles
(buildings). The FM is determined by the availability one desires. Availability is defined
as the amount of time (expressed in % per year) that a link properly detects the signal.
"Properly” in this case is a BER that is less than 10
-9
. The table below describes the
outage period per year that corresponds to the different availability values.
Table 10: Availability Versus Outage Time
Availability (%) Outage Period Per Year
99.9 8.8 hours
99.99 53 minutes
99.999 5.3 minutes
99.9999 32 seconds
It is recommended that the link be designed for availability greater than 99.99%. The tool
automatically calculates the estimated required fade margin over distance to achieve this
availability.
A key advantage of the Redline product is that it features a transmission correction
scheme called Automatic Repeat Request (ARQ). The ARQ algorithm essentially
detects when a packet(s) has been lost, due to fading, and makes a request to the
remote system to re-transmit the lost packet(s). This feature provides an equivalent link
budget gain of over 5 dB, which translates directly to an improved margin.
Another key advantage of the Redline product is that it features dynamic adaptive
modulation, i.e., the system selects the modulation scheme automatically on a burst-by-
burst basis, based on the measured S/N response. In this manner, the network is
constantly balanced for the optimum spectral efficiency, no matter what propagation
conditions prevail. Higher order modulation schemes (e.g., 64 QAM) are typically
deployed at reduced ranges while lower order modulation schemes (e.g., BPSK) are
implemented at long distances.
A sample link budget is shown in Figure 38 for the AN-50 system operating in 64 QAM,
3/4 code rating, providing a net burst throughput of 54 Megabits per second (Mbps). This
provides an average throughput of 43 Mbps to the Ethernet port. The calculation is
performed for LOS, however the graph (shown in Figure 39 below) also covers the
OLOS and NLOS conditions.
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