CSI Framework

CSI Framework is one of the most complicated structure and process in NR. I have posted three separate notes with different aspect of this topic. I thought I need to write a page which can consolidate the three separate notes and this page is the one.

Where to Start ? How to Move forward ?

What makes it super difficult to understand 5G CSI Framework is due to its extreme flexibility. Actually flexibility itself would not make things difficult of understanding, but in most cases 'flexibility' tend to make configuration very complicated. It is this Complexity to give us hard time to understand 5G CSI. Unfortunately, there is no way to make the 'complexity' simple. What I am trying to do in this section is to give the readers some tips on how to break down the framework and how to tackle each of those broken-down components and move on. This is just based on my personal experience, it may or may not apply to you. Just my two cents.

Following is where I started and how to move forward.

  • i) Understand the meaning of < 38.211-Table CSI-RS locations within a slot > to the point where you can visualize the table onto NR resource grid. (This note on CSI-RS would help you with this)
  • ii) Learn how to convert the CSI RS on Resource Grid (the outcome of the step i) to RRC Configuration
  • iii) With the practice of step i) and ii), try to configure CSI-RS for TRS before you move further. You may need some study and practice on step [1] and [2] in Overall CSI Framework Structure. I am recommending this because this configuration would not require ReportConfig
  • iv) Understand the meaning of this table <Type 1 Single Panel : Based on 38.214 v15.3-Table Supported configurations of (N1,N2) and (O1,O2)> and learn how to visualize it.  (This note would help you with this)
  • v) Learn how to convert the visualized structure (the outcome of step iv) into RRC message. (This note would help you with this)
  • vi) [This is optional] If you are interested in more details on the configuration of the antenna panel (e.g, Mathematical structure of each pannel structure), check on this, this, this and this.
  • vii) Once you get familiar with all the steps mentioned above, check if you can configure by yourself (or at least understand) a full RRC parameters for a CSI report (You have to go through step [1][2] and [3] in Overall CSI Framework Structure.
  • viii) Once you got familiar with steps mentioned above, move forward to multi-pannel and codebook type II.
  • ix) If you want to see how the various CSI configurations are tested and get some working protocol log, check out this (Amarisoft TechAcademy)

Overall Structure of the CSI Framework

Overall procedure for CSI-RS operation can be described as follows and I put the link for the notes which lead you to the details of each step.  

[1] NW



Configure/Define CSI Reference signal at physical resource grid. See CSI-RS page for the details




[2] NW




Combine one or more CSI-RS into a higher level structure for a specific purpose. See CSI-Report page for the details.




[3] NW


Define/Configure the Report Criteria (Report Period, Quantity, Trigger condition, Codebook Configuration etc). See CSI-Report page for the details of Report Period, Quantiy and overall structure of CSI Framework. See CSI Codebook page for the details of CSI Codebook (Precoding Matrix).




[4] UE

Perform Measurement and Report


UE perform the measurement as instructed by Network and report the result to the network.




[5] NW

Adjust PHY/MAC parameters


Based on the report from UE, NW would adjust PHY/MAC parameters like MCS, Antenna Configuration, CSI Codebook etc.



Get some hands-on Test


Of course, this is not a part of the protocol itself. But if you get to have some chance to try various working scenario, it would be the best way to learn. You can take a peek into a test setup and working protocol log here (Amarisoft TechAcademy)