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Figure 6. Additional configurations.
Figure 6 shows on the top a HS/SD solution using four antennas per hop. This is the best solution for long
hops: no loss of fade margin and switching is hitless in both directions.
The middle solution is 2+0, i.e. two working channels and no protection channel. However, considering
Ethernet traffic, 2+0 has some protection against a single equipment failure. Two separate radio channels
are required and when properly configured, when a fault occurs in an ODU or modem, L2 or L1 aggregated
packet traffic is automatically rerouted to the remaining working channel. Half of the packet capacity is still
available when one channel is faulty.
The bottom configuration in Fig. 6 is an aggregation node solution: separate sites connected to a single IDU
and a single Ethernet connector. One or more radio channels will be needed depending on the angular
spacing of antenna directions. In principle 4+0 without XPIC can be even used on a single hop but then four
radio channels are needed.
It is possible to use less radio channels on the same hop using XPIC and crossed polarizations (Figure 7
below). The modems are interconnected using XPIC cables. The system calculates the original signals using
all available information, i.e. both IF signals are connected to both modems.
