Skip to main content

CQI/PMI and RI on same subframe, SRS and PUCCH format 1/1a/1b 2/2a/2b on same subframe, SR and CQI/PMI on same subframe




If SRS and PUCCH format 2/2a/2b messages coincide in same subframe, UE shall not transmit SRS.
If SRS and PUCCH format 1/1a/1b (ACK/NACK and/or +SR) coincide in same subframe, UE shall transmit SRS iff simultaneousSRSACKNACK is true. 
If SRS and PUSCH RARG (Random Access Response Grant) coincide in same subframe SRS will be dropped.
If SRS and retransmission of same transport block (as a part of contention based Random access procedure),  coincide in the same subframe SRS will be dropped.
If SR and CQI/PMI/RI coincide in same sub-frame, CQI/PMI/RI will be dropped only if UE send SR (which is triggered by BSR) otherwise CQI/PMI/RI will be reported by UE on the same subframe.

If CQI/PMI and RI is configured on same subframe and coincide, MAC will schedule RI on that subframe   and hence UE will report RI on that subframe instead of CQI/PMI (One possible reason could be Periodicity of RI is always greater than equal to CQI/PMI. Which means eNB will have RI input less frequent than CQI/PMI input from UE, hence priority is given to RI).
(Example: Configure the higher layer parameter cqipmiconfigindex and riconfigindex in a way such that CQI/PMI and RI coincide on same subframe and verify the reporting using UE logs as well as FAPI interface . cqipmiconfigindex=17 and riconfigindex=483 could be one valid configuration to simulate this scenario,  according to Table 7.2.2-1A and Table 7.2.2-1B of 36.213).

 Please share if you find this is useful information.
Questions are welcome.
Labels:

Comments

Post a Comment

Popular posts from this blog

Difference between SRS and DMRS

There are two types of reference signals used in LTE uplink, to estimate uplink channel quality. Which allow eNB to take smart decisions for resource allocation for uplink transmission, link adaptation and to decode transmitted data from UE . So to take first smart decision by eNB Sounding Reference Signal  (SRS) is being used. SRS is being transmitted by UE on the last symbol of subframe (in which subframe will come to know later). This SRS report the channel quality of over all bandwidth and using this information eNB assign the resource (to UE for uplink transmission )has better channel quality comparing to  other bandwidth  region. So is SRS optional in LTE? Yes. SRS is configurable and infact we do not need SRS at all in case eNB assign all resource block or full bandwidth or have no choice. Now on the basis of configuration and node wise there are two types of SRS (refer 36.211), cell specific (Common SRS) and UE specific (Dedicated SRS).  eNB...
20 comments
Read more

What is Rank Indicaton in LTE

Rank Indication is one of the important input to eNB , in selection of the transmission layer in downlink data transmission. Even though the system is configured in transmission mode 3 (or open loop spatial multiplexing) for a particular UE and if the same UE report the Rank Indication value 1 to eNB, eNB will start sending the data in Tx diversity mode to UE . If UE report Rank Indication 2 , eNB will start sending the downlink data in MIMO mode (Transmission Mode 3). Why we need this RI in LTE concept? When UE experience bad SNR and it would be difficult (error prone) to decode transmitted downlink data  it gives early warning to eNB by stating Rank Indication value as 1. When UE experience good SNR it pass this information to eNB by indicating rank value as 2. Because of this reason, you might have observed that some time data transmitted by eNB is in Tx diversity mode, though MIMO was configured and hence you may have observed less downlink throughput than expected ...
15 comments
Read more

Downlink Assignment Index (DAI)

DAI ( Downlink Assignment Index ) is an index, which is communicated to UE by eNB to prevent ACK/NACK reporting errors due to HARQ ACK/NAK bundling procedure performed by the UE. To understand how DAI works we need to learn how ACK/NAK reporting used to happen in LTE TDD. In LTE TDD, UE can send single ACK/NAK of multiple PDSCH sub frame in one bit for each code word CW0 and CW1. UE perform AND logical operation on each code word CW0 and CW1 (CRC Passed/Failed) of each PDSCH received and report the result in two bits (00, 01, 10, 11) on specific uplink subframe. Below is the table which shows that which all PDSCH subframes need to be bundled for reporting ACK/NAK on which Uplink subframe for each TDD UL DL configurations (Mentioned only for config 1 and config 2 in green color). For Example:            UL/DL Configuration 1: We can see that the k value for 2 nd subframe (Uplink) are 7,6 (according to Table 10.1.3.1-1 of s...
2 comments
Read more