ENHANCED PDCCH LINK ADAPTATION IN LTE

Here we will discuss about a LTE Feature called Enhanced PDCCH Link Adaptation. The main aim of this feature is to increase the capacity to allow more users to be scheduled by improving the efficiency of PDCCH usages. The capacity can be improved by Utilization of CCE in more efficient way.

How it Works: In every period channel quality(CQI) is reported to eNodeB by UE. In basic PDCCH Link adaptation its uses the PDSCH successful transmission and its offset as an information for PDCCH to achieve any particular BLER.
                          Enhanced PDCCH Link Adaptation uses PDSCH HARQ-ACK from UE and also the PUSCH detection result to determine whether the PDCCH transmission is successful or not.

Algorithm Flow:

 1. SINR Estimation: Based on the CQI Report report that UE sent to eNodeB.

 2. PDCCH Outer Loop Adjustment: To Achieved the required BLER.

 Elements to determine the criteria:
   > Success or failure of the PDCCH transmission. The HARQ-ACK reports and PUSCH Detection results are used for this. As long as the eNodeB can detect the ACK, either positive or negative, PDCCH transmission considered successful. 

> Aggressive or Conservative PDCCH Allocation. The PDCCH allocation is considered conservative if the allocation of CCE exceeds the required number and the aggressive one is the other way around.

From the outer loop adjustment, the output is required number of CCE for the same.

 The result of the implementation can be seen in the below chart.

Based on the chart above it can be seen that the CCE used decreased by 27% and the cell throughput improved by 1.55%.

Conclusion: This feature is capable to occupy CCE more efficient which lead into the increased cell Throughput.