5-5 MINI-LINK BAS
EN/LZB 111 0542 P2B Technical Description
5.2.1 Media Control Loops
Media control loops are needed to control transmission parameters of
Terminals and RN in order to make a proper working of PMP
transmission scheme.
PMP synchronisation encompasses carrier amplitude and frequency
control, symbol clock phase and modulation index control. These
control loops are used to compensate the effects of the real
components and of the radio propagation.
The above controls are distinguished in local internal loop and in
remote radio loop. The local loops are confined to the Node whereas
radio loops encompass node and terminals while the others are the
radio controls loop. These are:
• Carrier Amplitude
− Local Loop in Down-Link
− Local/Remote loop in Up-Link
• Carrier Frequency
− Only internal Local Loop, at the AT side
• Modulation Index
− Local/Remote loop in Down-Link
− Local/Remote loop in Up-Link
• Clock Phase
− Only internal Local Loop in Up-Link
The internal and radio loops share the same error detectors. The error
corrections are either performed internally in the demodulator for the
internal control loops or performed in the remote radio and modulator
for the radio control loops.
The action of internal control loops is faster than of the remote, with
the only exception of the amplitude control loop; they act directly on
the received bit stream, whereas the radio control loops act at the
remote transmission side and their time response depends on the loop
bandwidth.
In order to implement the radio control loops, a logical channel within
the physical radio channel is provided to send back through the air
interface the error information to the terminals.
Symbol clock phase and modulation index control are strictly related
to the modulation and demodulation processes and are following
described.
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