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AR# 39957

LogiCORE IP LTE UL Channel Decoder - Can the IP decode the CQI field size from the decode RI in the same subframe?

Description

Can the IP decode the CQI field size from the decode RI in the same subframe?

For example, assuming there aretwo antennas, in section 5.2.2.6.1-1 of TS 36.212 it says that CQI/PMI report is (4+2N) when rank is 1 or (8+N) when rank is 2. In section 7.2.1 of TS 36.213 it states that in mode 1-2 (Wideband CQI and Multiple PMI) "For transmission mode 4 the reported PMI and CQI values are calculated conditioned on the reported RI". In this section it says that the minimum reporting interval for a periodic reporting of CQI and PMI and RI is 1 subframe.

The RI can be reported every subframe, so the CQI length is affected by the RI reported on that very same subframe. In this cases, the RI affects the length of the reported CQI/PMI. This is done via PUSCH so that a change in CQI length also affects the data decoding.

Can the IP decode the CQI field size from the decode RI in the same subframe?

Solution

The LogiCORE IPLTE Channel Decoder cannot at present decode the CQI field size from the decode RI in the same subframe.

The work-around is based on passing the data through the UL Channel Decoder twice.

In the first pass, decode the RI and any ACK present on the PUSCH, also perform a blind decode of the CQI data as if rank was 1. This is a very low latency pass as it does not use the turbo decoder.

In the second pass, decode any TB data on the PUSCH, and also perform a blind decode of the CQI data as if rank was 2. The software can use the decoded RI data from the first pass to decide which of the two CQI decodes to use. Also, the two-pass method is only required when you know you have downlink MIMO for a given UE.

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
31422 LogiCORE LTE UL Channel Decoder - Release Notes and Known Issues N/A N/A
AR# 39957
Date Created 05/25/2011
Last Updated 12/15/2012
Status Active
Type General Article
IP
  • 3GPP LTE UL Channel Decoder