Afar AR-24010E, Руководство оператора

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pulsAR radio Operator's Manual
“fast” (see command roam) . In this mode the radio scans for alternate channels at a rate eight times
faster than in normal mode and therefore can track a fast changing RF environment. There are two
drawbacks to the fast roaming mode: (i) you can not have roaming branches, and (ii) the radio
throughput is reduced by 22%.
2.2.4 Roam change hub criteria
When a mobile node scans its environment and finds one or more alternate access points, it decides
on its own when it is appropriate to change to an alternate hub. You have some control over this
decision with the
roam change-hub command. There are three settings, see the description in
section 4 under roam command to find which setting may be appropriate for your application.
2.2.5 Redundant RF paths
In a tree network you can deploy a leaf node with two antennas pointing at two different access points
(branches or root) and setup it up to roam between the two antennas and frequencies. The leaf will
initially select the best path to reach the root of the network. If a radio upstream fails, the leaf will
automatically switch to the alternate access point to avoid the failed path to the root.
2.2.6
Redundant hub operation:
In a point-to-multipoint deployment it is often desirable to deploy the hub site with two redundant
radios. You can use the roaming feature to achieve this result. Configure the two hubs to different
non-overlapping channels. Configure all the remotes to roam between the two hub channels. If one
of the hub radios fail, or if there is interference in one of the channels, the remote radios will
automatically attach to the other hub.
In this application, since you would be co-locating the two hub radios, you need to pay attention to
the possibility of self-interference. Section 2.4 describes this issue and what you need to do to avoid
it.
2.3 Time Division Duplex
2.3.1 Fixed and variable cycle split
The pulsAR radio operates in Time Division Duplex (TDD) mode meaning that the radio switches
between transmit and receive over RF. In a point-to-multipoint topology this cycle consists of one
phase used for outbound transmissions (from parent to children) and a separate phase for inbound
transmissions (from the children to the parent). In the tree topology the cycle includes four phases: a
branch node first communicates with its children (transmit and then receive) and then with its
parent(receive and then transmit).
The radio provides two parameters that let you configure the TDD operation to best suit your
application. You can select the total
cycle period between 20 and 40 ms and you can control the
cycle split to favor either outbound or inbound traffic. You only need to set these two parameters at
the hub or root node: all the children will pick up these TDD values from their parents.
A cycle period of 20 ms (default) results in lower latencies throughout the network. However there
will be more transitions between transmit and receive resulting in somewhat lower throughput
capacity for the network. A cycle period of 40 ms has the opposite effect.
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