Operating Manual 6175.4760.02 – 01 5.41
M3SR Series 4100 IP over Air (IPoA)
ALE-3G / xDL ARQ Functionality
Instead of the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) mechanism of
the IPoA protocol, the ALE-3G uses its own ALE algorithm to establish logical links between
stations of an ALE-3G network. This automatic link establishment algorithm chooses the best
communication channel to the destination based on channel quality analysis (LQA). After the
establishment of a logical link between two stations, the initiator of the link has the first op-
portunity to transfer an IP packet with one of the xDL protocols over the channel to the des-
tination. HDL (High Data Rate Link Protocol) and LDL (Low Data Rate Link Protocol) always
guarantee the error-free transfer of the packet by using an ARQ mechanism.
Since the ALE-3G channel access differs from the IPoA protocol, the following features of
the IPoA protocol are not needed or supported:
Note
FastLink Mode (FLM) Not needed. ALE-3G establishes logical links by itself.
IPoA Rebro Not supported.
Message Service Alert messages Not supported. xDL only supports Point-to-Point links.
IPoA operational mode Not supported.
IPoA connection mode Not supported.
Change of IP Air address Not supported. ALE-3G uses a static look-up table for
conversion of IP to ALE-3G address. This can only be
changed via configuration.
Multicast Routing Not supported. xDL only supports Point-to-Point links.
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