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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 one. 

However, it is not necessary that eNB will always change the transmission mode based on RI value, it could be implementation specific decision. 
Questions are welcome.
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Comments

  1. Unknown18 May 2015 at 05:05

    why some vendors recommend tm3 for TDD?

    ReplyDelete
  2. Abhishek Kumar18 May 2015 at 22:49

    Dear Ahmed,

    Good question. Here is my logic behind it . As we know TM does depend on the channel conditions. In TDD UL and DL are on same frequency , hence channel characteristics are same . Because of that a feedback is not needed from the UE when a suitable Uplink signal is present that the base station can use to estimate the channel (using uplink SRS).

    ReplyDelete
  3. Unknown30 May 2016 at 02:15

    Hi,could u tell the reasons for poor MIMO Utilization?

    ReplyDelete
  4. Unknown18 May 2017 at 07:23

    Rank indicator 2 definition

    ReplyDelete
  5. Unknown28 September 2017 at 00:38

    I got issue for throughput. UE still get RI 1 even RF conditions are good (RSRP and SINR) and the network MIMO are configured.

    ReplyDelete
    Replies
    1. PavanKumar Raju9 March 2018 at 18:16

      Hi...are you able to resolve your issue ? Can you shed some inputs on how did you debug ? Thanks in advance.

      Delete
    2. Unknown11 March 2018 at 13:53

      You can check this on the device side whether proper UE Category is set on the device. Once I faced this issue and it came out that the UE Category was wrongly set as '1' on the device hence didn't report Rank2.

      Delete
  6. Unknown12 October 2017 at 21:43

    which scenario Rank 3 & Rank 4 Coming in picture?

    ReplyDelete
  7. Unknown26 February 2018 at 22:17

    hi,

    i have an issue regarding RI Vs TM.
    my 99% sample of Transmission mode is TM3.
    but RI shows RI1 55% and RI2 45%.
    so how TM is dependent RI.

    ReplyDelete
    Replies
    1. owais30 March 2018 at 05:55

      WELL how TM is dependent RI.??

      Poor SINR Poor RI, vendor set the SINR thershold for switching RI + hyst means "N" times consecutive request for TM change then convert
      suppose 15dbm set the criteria for TM3 condition tx diversity as UE get 15dbm or greater the range signal run the hyst count "N" , as fullfill N times request convert TM2 to TM3

      also have option to set SINR + FER thershold for TM switching

      Delete
  8. Unknown23 April 2018 at 05:24

    Can any one explain me about transmission modes

    ReplyDelete
  9. Unknown22 April 2019 at 09:08

    HI, How can I measure Rank Indicator through the Nemo Analyze tool?

    ReplyDelete
  10. Unknown13 June 2019 at 23:01

    What will be Rank Indicator for Multi User Massive MIMO or Single User Massive MIMO ?

    ReplyDelete
  11. Gaurav12 September 2019 at 08:26

    what is the difference between reported RI and Observed rank indicator?

    ReplyDelete
  12. Unknown8 October 2019 at 08:40

    Hi All,
    Could you please share is there any requirement for cells that Rank 2 will be start working?is there any requirement of CQI or any others threshold for coverage or quality?

    ReplyDelete

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