MINI-LINK BAS 5-18
Technical Description EN/LZB 111 0542 P2B
FEC bits are inserted in each timeslot in addition to the original MAC
packet data stream. The FEC bits are spread unevenly over the slots in
such a way to better protect information fields related to the MAC
protocol than the payload.
FEC is able to correct one error in the protected field. As
demodulation process cause double adjacent errors, fields covered by
FEC are bit interleaved and two FEC coded are actually acting in
order to ensure that the double adjacent errors generated by the
demodulation process will result in one error in a field covered by the
FEC.
5.4.5 Performance Monitoring
Facilities are foreseen in order to support the quality performance
monitoring in the LLC layer.
Evaluation of performance are mainly based on the mismatch detected
on the byte referred as CRC-8, as this byte is meant to detect errors in
a complete TDMA/TDM slot encompassing then both ATM cell and
permit field.
The performance parameters are evaluated per NU both in uplink and
downlink, as there are different physical links for each NU.
In order to do this in the uplink the RN has to take in account the
transmitting NU whereas in the downlink the NU can monitor all
TDM slots.
Performance events provided for the ATM layers are:
• Cell error ratio
• Cell loss Ratio
• UBR discarded cells
• CBR discarded cells
Performance events provided for the physical layer are:
• Unavailability/Availability Time (UAT/AT)
• Errored Second Ratio (ESR)
• Severely Errored Second Ratio (SESR)
• Background Block Error Ratio (BBER)
In order to evaluate the above Performance Events following
parameters are counted:
• Number of received TDMA/TDM slots
• Number of CRC-8 errors on uplink, calculated over the complete
TDMA slot, or missing TDMA slots, for measurement on
physical layer
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