How 2 CRS to 4 CRS conversion can improve Throughput in LTE?
If you have use same power setting, you will reduce 3dB with 4CRS which you have less overshooting/overlapping area, less user and less PRB utilization which can high possibility impact your throughput
Another thing 4CRS with MaxRank4 you can get more than 2 Stream on MIMO configuration
I am also having the same question that how 2 crs to 4 crs conversion improves throughput as total available Resources for carrying data will be reduced once 2 crs to 4 crs conversion is done.
This will answer question of crs port: Cell Specific Reference Signal (CRS) - (Advanced LTE-A FDD Downlink)
It shrinks the coverage in short from 2 to 4.
You use all four layers for tx rx mode but port for rs is 2 instead of 4 inspite you have all the ports available.
As the no of RS increases from 16 to 24, the demodulation performance of reference signal improves.
Hence CQI improves.
Furthermore, the PMI also increase from 7 to 64.
Thanks good info. So its good for capacity layer in case of multicarrier network.
With 4 CRS (4 antenna port) number of RS REs increased and PDSCH REs reduced.
But with 4 antenna ports, number of precoding metrices (PMI codebooks) increase from 6 to 64.
It means with 4 CRS UE can send PMI with better accuracy and granularity.
Hence downlink scheduled MCS can be improved and becomes more accurate.
Furthermore, with increase in RS REs, channel estimation and demodulation of PDSCH is improved which improves CQI.
This overall results in improve throughput in 4 CRS compare to 2 CRS.
I think number of codebook for 2 CRS is 4 and Precoding matrix information is size of 8 (Index 0 to 7, although index 7 is not used).
For 4CRS, number of codebook is 16 and Precoding matrix information is size of 64 (Index 0 to 63).
That’s why in DCI format, we see Precoding information as 3 bits for 2 CRS and 6 bits for 4 CRS.