CQI

[rishi]

Hi Experts...

Can anyone say me about

What factors CQI is dependent and main differences between 16QAM and 64QAM technologies????

[blind shadow]

16 QAM has 16 phases in the quadrant as the modulation increases the phase also increases... the more the phase, the more chances of allocating data channels... data is modulated at a faster rate and is determined by the coding rate... the higher the coding rate the higher the throughput of course it all depends on the radio quality. (i hope this one helps)

[hari_2208]

CQI is used by wireles data technologies to provide fast feedback abt the currect status of the UE /rf condition.This along with the HARQ ack/nack ,cell load & specific implementation of schedular in nodeb or AP helps to decide what or when or how much data should be alocated to teh UE in next cycle.

now CQI conist of following i/ps in HSDPA
- DL SIR of HS-PDHSCH
- QUALITY IF Ec/Io for 3 slots , 1 slot before sending cqi
- TB size
- Mod type
- no of ovsf codes
- power

all above should allow to have service @ max BLER of 10%.And lastly some handset may only support qpsk ,while others can support qpsk & qam-16.

[hari_2208]

sorry forgot to add....

16 qam can allow to transmit total max 4 bits/symbols (data + code)
64 qam can allow to tranmit total max 6 bits/symbols (data + code)

but as the modulation order increases they need more power or /also clean rf condition for the r'cver to decode the data properly.

in lte-advanced i think they are talking of using 256 QAM,though iam not sure if its actually practcially done yet.