Radio Terminals
4.6 1+1 Protection
4.6.1 Overview
A Radio Terminal can be configured for 1+1 protection. This configuration
provides propagation protection and equipment protection on the MMU, RAU
and antenna. Propagation protection may be used on radio links where fading
due to meteorological and/or ground conditions make it difficult to meet the
required transmission quality.
Configurations for 1+1 protection can be in hot standby or working standby. In
hot standby mode, one transmitter is working while the other one, tuned to the
same frequency, is in standby. It is not transmitting but ready to transmit if
the active transmitter malfunctions. Both RAUs receive signals. When using
two antennas, they can be placed for space diversity with a mutual distance
where the impact of fading is reduced.
In working standby mode, both radio paths are active in parallel using different
frequencies, realizing frequency diversity. Using two different frequencies
improves availability, because the radio signals fade with little correlation to
each other. Space diversity can be implemented as for hot standby systems.
6654
f2
f1
Working Standby
f1
f1
Hot Standby
Figure 73 Radio link protection modes
For information specific for XPIC, Section 4.6.3 on page 98.
4.6.2 Functional Description
The following different protection cases can be identified:
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