MDS 05-4846A01, Rev. H
SD Series Technical Manual
49
the
Diagnostic Settings
screen (see “Diagnostic Settings” on
Page 52). A Store and Forward device is a radio designated to
retransmit data to/from an outlying Remote (see SAF Network,
below).
•
SAF Network
—(AP Only) Selects whether or not a Store and For-
ward radio is present in the network (
True
), or not (
False
). Store and
Forward extends the coverage area of a network beyond the pri-
mary “footprint” of the system. This can be used to link outlying
Remotes (or Remotes blocked by terrain or other obstructions)
into the network. A detailed discussion on using Store and For-
ward is provided below.
•
Repeater Network
—(AP Only) This setting must be enabled if the
RF network contains a repeater station, or communications will
not work. Remotes automatically learn this setting from the AP.
•
Retry Count
—If a message is not acknowledged after transmission
it will be resent. This value controls how many times the radio
attempts to resend the message before discarding it.
•
Time-to-Live (s)
—When a message arrives from the payload inter-
face(s) it is time-stamped and queued for radio transmission. If
the radio cannot transmit the message before the Time-to-Live
(TTL) value, the message is discarded. This helps prevent stale or
old data from being sent over the air.
Store and Forward Operation
Store and Forward (SAF) operation extends a wireless network’s cov-
erage area by electing a device (or devices) to store data and forward it
to a unit (or units) beyond the reach of the primary coverage area. Con-
ventional RF repeaters receive and transmit data simultaneously. They
are effective at increasing range with low latency, but they are more
expensive, have high power consumption, and require more complex
installation. SAF-designated units act as smart single radio packet
repeaters. The SAF feature provides a simple, low cost alternative to
range extension when a traditional repeater isn’t desired.
Figure 30 on Page 50 depicts a typical single unit SAF network. This
network supports a
single
SAF hop. Chained SAF hops are not allowed.
However, multiple SAF radios are supported provided their RF cov-
erage areas do not overlap, as this would create radio interference and
severely reduce throughput. SAF will work in conjunction with repeater
assemblies to provide even more extended range.
NOTE:
Remote radios being served by a Store-and-Forward unit must
have their TX/RX frequencies set to match those of the
AP/Master station. This allows communication with the SAF
radio, which uses standard Remote TX/RX frequencies.
