FAST FACTS:
CQI is used in HSDPA as a measure of the downlink channel quality as perceived by the terminal which transmits the CQI values regularly to the nodeB which uses this information for scheduling of further downlink data transmissions.
CQI is used in HSDPA as a measure of the downlink channel quality as perceived by the terminal which transmits the CQI values regularly to the nodeB which uses this information for scheduling of further downlink data transmissions.
·
Based
on SIR-measurements on the Common Pilot Indicator Channel (CPICH)
·
An
increase of one step in the CQI value represents an increase of SIR of the
CPICH by one db
·
Each
5 bit CQI value is directly mapped to a transport block size (TBS), number of
channelization code and modulation degree. Depending on the capabilities of the
receiver, these values may differ between receivers for each CQI value.
·
The
nodeB uses these mapped values as an input to the scheduling algorithm.
·
The
scheduling algorithm for most implementations also considers other parameters
such as buffer status and priority levels.
·
The
CQI values range between 0(worst) and 30(highest).
·
CQI
values and their respective mappings to TBS, number of channelization codes and
modulation degree for each HSDPA category can be found in 3GPP specs
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