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12
When using L2 aggregation, a single "stream" is not distributed to the two radio paths due to the known
limitation of the standard LAG method. Several streams (e.g. different MAC DA or SA) are needed in order
to use the full capacity.
The more advanced NEC proprietary L1 aggregation (Physical RTA, PRTA) method will create a genuine
combined Ethernet port towards the air and even a single Ethernet stream can use the full capacity.
Modem versions supporting L1 aggregation PRTA: see Table 6 below (page 24).
CONFIGURATION DIAGRAMS
Figures 5 to 7 present the available configurations for iPasolink.
Figure 5. Basic configurations
From top to bottom, Figure 5 shows first a basic 1+0 hop, then a 1+1 Hot Standby (HS) and finally a three-
antenna Space Diversity (SD) solution combined with HS protection.
A single antenna is used with a hybrid (HYB). The hybrid will cause some extra attenuation in the radio
path, with a corresponding loss in the fade margin and increase in the outage time caused by fading. The
three-antenna SD solution is thus less effective than a genuine SD solution. In addition the space diversity
in the right-to-left direction is based on transmitter switching, which is not hitless (bit errors when
switching over).
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