Queries on LTE interference computation in Uplink

[Sab NT]

Hi everyone,

I am quite new to LTE trying to understand the module in ns3. I went through the design documentation for LTE for interference calculation but have some doubts regarding how it happens in the uplink. 1. Similar to downlink, in uplink also, the SINR can be calculated through control channel (SRS) or data channel (PUSCH). It is mentioned that the scheduler has different filters to specify what type of CQI it considers which I checked in the scheduler code in switch-case statements. But where is the filter value set in the module, can some one please point out. Is there any config setting which can change the default value of the filter?

2. In downlink SINR calculation includes Rx signals received from neighboring cells's enb as a source of interference. For uplink does it consider same way, i.e. does it take the Rx signals from UEs from neighboring cells as a source of interference in the SINR computation? 

3. For interference calculation in every TTI, does it consider any moving average from previous calculation or every TTI computes independently based on Rx signals in the interval? 

Sorry for any ambiguity in questions as I am trying to learn LTE.  Any help will be greatly appreciated.

Thanks in advance.

[Marco Miozzo]

Hi,

see in-line.

best,

marco.

On Thu, Mar 10, 2016 at 3:29 PM, Sab NT <sab...@gmail.com> wrote:

Hi everyone,

I am quite new to LTE trying to understand the module in ns3. I went through the design documentation for LTE for interference calculation but have some doubts regarding how it happens in the uplink. 1. Similar to downlink, in uplink also, the SINR can be calculated through control channel (SRS) or data channel (PUSCH). It is mentioned that the scheduler has different filters to specify what type of CQI it considers which I checked in the scheduler code in switch-case statements. But where is the filter value set in the module, can some one please point out. Is there any config setting which can change the default value of the filter?

The scheduler interface include an attribute system calld UlCqiFilter for managing the filtering of the CQIs according to their nature, in detail:

• SRS_UL_CQI for storing only SRS based CQIs.
• PUSCH_UL_CQI for storing only PUSCH based CQIs.
• ALL_UL_CQI for storing all the CQIs received.

It has to be noted that, the FfMacScheduler provides only the interface and it is matter of the actual scheduler implementation to include the code for managing these attibutes (see scheduler related section for more information on this matter).

 

2. In downlink SINR calculation includes Rx signals received from neighboring cells's enb as a source of interference. For uplink does it consider same way, i.e. does it take the Rx signals from UEs from neighboring cells as a source of interference in the SINR computation? 

Yes.
 

3. For interference calculation in every TTI, does it consider any moving average from previous calculation or every TTI computes independently based on Rx signals in the interval? 

Each TTI is evaluated independently; however, some phenomena can be evaluated in a different way (e.g., fading, shadowing, etc.).
 

Sorry for any ambiguity in questions as I am trying to learn LTE.  Any help will be greatly appreciated.

Thanks in advance.

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[Sab NT]

Hi Marco,

Thank you very much for your prompt reply.  I would like to confirm two more things:

1.  As you mentioned for the UlCqiFilter "it is matter of the actual scheduler implementation" , does the scheduler store all the CQI  (from SRS and PUSCH)  as a default behavior at present? 

2. As per present implementation, does the resource allocation for uplink transmission happen based on 'all' uplink CQI reports or based 'on one of the' reports (either from SRS or PUSCH)? Also could you please give pointers to the code modules where I can check the resource allocation in the uplink based on the CQI/MCS value? Is it in the scheduler code (e.g. pf-ff-mac-scheduler.cc) as done for downlink or somewhere else.

Thank you very much for your help.

[Sab NT]

Hi,

Found the answers of my last queryafter I started reading the scheduler code. The default value of UlCqiFilter is set in constructor of FfMacScheduler class as ALL_UL_CQI. And in scheduler code it updates the UE CQI values with the new sinr values obtained for uplink through SRS or PDSCH.  

Now I have will go through the resource allocation for uplink and will ask if I have doubts. Thank you for your help.

[Batool]

Hi all,

1) I am new for ns3 and I want to work on channel estimation, I know there are three channel reports (CQI, PMI, and RI) in LTE, the problem is that I did not find all of these report in ns3 . Is the current ns3 support all of these report or not ?

2) I wonder which channel estimation method is used in the current ns3.

Thanks you    

[Marco Miozzo]

Hi,

the LTE ns3 module supports only CQI, you may find more info on the channel estimation methods at the following link:
https://www.nsnam.org/docs/release/3.16/models/html/lte-design.html#phy

best,

marco.

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[Ali Ali]

Dear Marco,

I am very grateful for your reply. So, Marco do you know which release of lte that ns3 support because I know that the three report CQI, PMI  and RI for release 10 of lte.

Thanks 

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[Marco Miozzo]

Most of the code is designed based on R8, but there are functionalities also of R9 and R10.

The fact that PMI and RI are not supported are due to the MIMO model, more info the link I passed you.

best,

marco.