LTE Resource Block

[yuxiang shen]

Hello everyone!

I'm a new ns3-user and now working on LTE simulation. What i want to get from the simulation is to get the number of resource blocks each eNB needs to support a given data demand(e.g. 1Mbit/s) of attached UEs. I have several questions:

1. How to set the data demand of users? (The teacher told me that i don't have to consider EPC, it's just LTE)

2. Which traces record the number of resource blocks being used by different eNBs?

Anyone have an idea about my questions? I really appreciate your help.

[Nicola Baldo]

Hi Yuxiang,

On Tuesday, August 12, 2014 9:56:43 AM UTC+2, Yuxiang Shen wrote:

Hello everyone!

I'm a new ns3-user and now working on LTE simulation. What i want to get from the simulation is to get the number of resource blocks each eNB needs to support a given data demand(e.g. 1Mbit/s) of attached UEs. I have several questions:

1. How to set the data demand of users? (The teacher told me that i don't have to consider EPC, it's just LTE)

please read the LTE module user documentation for this. There have been also several discussions on this list about how QoS support is provided by the LTE MAC scheduler - I highly recommend you to search for these previous posts and read them.

 

2. Which traces record the number of resource blocks being used by different eNBs?

same here: please read the LTE module user docs as well as the many previous posts on this topic.

Note that the problem you are dealing with is not as trivial as you expect, hence reading previous posts where a similar topic was already discussed would be highly beneficial for you.
 

[Yuxiang Shen]

Hi Nicola,

Thank you for your answer! I'm now reading the LTE Module documentation for getting more details. But i'm not clear about how to find the previous posts... Should i search for topics with keyword "LTE" , "QoS Support" or some better ideas? Thanks again.

[Yuxiang Shen]

Hello Nicola,

i still have a basic question: like all the examples in LTE, if i have written these codes like ActivateDataRadioBearer, does it mean that not i have the data transmission(data traffic) in my system? I have seen some other posts, someone says there is still no traffic in the system. I'm looking forward to your answer. Thanks a lot.

On Wednesday, August 13, 2014 11:54:00 AM UTC+2, Nicola Baldo wrote:

[Tommaso Pecorella]

Do

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At

The

Same

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https://groups.google.com/forum/?hl=en#!topic/ns-3-users/4Amc-IWYLHo

[Yuxiang Shen]

I'm so sorry~I have just surprised found someone who has the same problem as me. I tried to contact him privately. 

[Tommaso Pecorella]

Hi,

it's always a good thing to share the efforts.

For the sake of other people that (in the future) may have the same problem, mind to post your thoughts and considerations once you have a good solution ?

Thank you very much,

T.

On Thursday, August 14, 2014 9:01:51 AM UTC+2, Yuxiang Shen wrote:

I'm so sorry~I have just surprised found someone who has the same problem as me. I tried to contact him privately. 

On Wednesday, August 13, 2014 7:43:45 PM UTC+2, Tommaso Pecorella wrote:

Do

[Yuxiang Shen]

Hello,
of course~ now i am reading the documentation. If i could get some idea, i'd like to share it.

[Yuxiang Shen]

I'm a bit confused with EPS bearers and Applications. If i would make some change in my program, which one is the right?(Should i increase EPS bearers or Applications?) I'm using the PssScheduler(sorry, not PfFf) and as in the example, i set the datarate like(gbrDl and so on). However, there are also no changes in the output. Thank you for taking the time.

On Tuesday, August 12, 2014 9:56:43 AM UTC+2, Yuxiang Shen wrote:

[Nicola Baldo]

On Tuesday, August 26, 2014 2:23:47 PM UTC+2, Yuxiang Shen wrote:

 I just use a loop to generate the same applications between UE and remoteHost for 10 times. Is it a possible and right way to increase the traffic? But unfortunately, i have seen no changes in the Trace outputfiles... 

could work if setup properly, but I recommend changing the traffic generation rate of the application instead.

[Nicola Baldo]

On Tuesday, August 26, 2014 3:40:42 PM UTC+2, Yuxiang Shen wrote:

I'm a bit confused with EPS bearers and Applications.

I see

 

If i would make some change in my program, which one is the right?

Mmmmh a tough question, isn't it?
 

(Should i increase EPS bearers or Applications?) I'm using the PssScheduler(sorry, not PfFf) and as in the example, i set the datarate like(gbrDl and so on). However, there are also no changes in the output.

It seems to me that you lack a bit of background in LTE and EPC. Please read a good LTE book/tutorial to clarify what an EPS bearer is and how Traffic Flow Templates work. Then re-read the LTE module design and user documentation for how to configure applications and EPS bearers according to your simulation objectives.
 

[Yuxiang Shen]

Hello,
According to TS213 Table 7.1.7.1-1 and Table 7.1.7.2.1-1, i could get the Number of physical resource blocks(NPRB) for each user through MCS and Transport Block Size, which are available in the DlMacStats output. When i use round robin scheduler. i try to calculate the NPRB according to mcsTb1 and sizeTb1, and also check the result by logging the RrFfMacScheduler(In the logging file i could see which RBGs are assigned to which user in each subframe). It seems correct but i'm not sure. Could anyone tell me whether this is the right way to find the resource allocation?
From the LTE documentaion i know that RR Scheduler "works by dividing the available resources among the active flows". So regardless of the datarate(the traffic i set through packetsize and interpacketintercal), all the resource blocks will be used. Is there any way that each eNB uses only part of resource blocks rather than all of them?

Thank you for taking the time.

[Yuxiang Shen]

Hello,
meanwhile i have also noticed, when i use PssFfMacScheduler, all the available RBs will be assigned to a single user. By looking at the DlMacStats it seems that in each subframe(1ms) every enb can only serve one user and assign all the resource(again, regardless of the traffic ,always the whole resources!). Is it normal or which mistake i have ignored? I really appreciate your help.

[Nicola Baldo]

Hi Yuxiang,

On Wednesday, September 3, 2014 3:31:28 PM UTC+2, Yuxiang Shen wrote:

According to TS213 Table 7.1.7.1-1 and Table 7.1.7.2.1-1, i could get the Number of physical resource blocks(NPRB) for each user through MCS and Transport Block Size, which are available in the DlMacStats output. When i use round robin scheduler. i try to calculate the NPRB according to mcsTb1 and sizeTb1, and also check the result by logging the RrFfMacScheduler(In the logging file i could see which RBGs are assigned to which user in each subframe). It seems correct but i'm not sure. Could anyone tell me whether this is the right way to find the resource allocation?

yes the method you proposed makes sense.
 

From the LTE documentaion i know that RR Scheduler "works by dividing the available resources among the active flows". So regardless of the datarate(the traffic i set through packetsize and interpacketintercal), all the resource blocks will be used. Is there any way that each eNB uses only part of resource blocks rather than all of them?

other schedulers allocate RBs differently, in particular some of them (CQA, PSS, TBFQ) do it according to the datarate. See the LTE module docs for details.

if you are interested in applying some of these schedulers to a subsect of the RBs, then you should check Piotr's GSoC2014 work:
http://www.nsnam.org/wiki/GSOC2014LteFFR

[Nicola Baldo]

On Friday, September 5, 2014 10:17:31 AM UTC+2, Yuxiang Shen wrote:

meanwhile i have also noticed, when i use PssFfMacScheduler, all the available RBs will be assigned to a single user. By looking at the DlMacStats it seems that in each subframe(1ms) every enb can only serve one user and assign all the resource(again, regardless of the traffic ,always the whole resources!). Is it normal or which mistake i have ignored? I really appreciate your help.

PSS might result in that behavior in some case, but it does not mean that it always works like this. Please read the docs of the PSS scheduler for more details.

[Yuxiang Shen]

Hello Mr. Baldo,
thanks a lot for your detailed information. i'm now reading the ffr alogirithm. I  have also found some information that i have ignored in the test-suite documentation. The reason why only one user is served in each subframe may be that i don't introduce fading model in the program and cause all the subchannel with same CQI and also the user with same priority. Thanks for your help, i will work on it further.

[Yuxiang Shen]

Hello Mr. Baldo,
I have tried the FFT Algorithm(that's a great work) which you have recommended. eNBs now have only part of available RBs, but it's sadly not the solution of my problem, because they still use all the available RBs(Only the number of available RBs for each eNB has changed). My question is whether some RBs could be unused.  E.g. i have only low traffic, why should i use all of the resource blocks to send the data? Could i just use some of them to support the relative low traffic? I think the similar problem is dicussed in another post, which also remains unsolved.
https://groups.google.com/forum/#!searchin/ns-3-users/infiel/ns-3-users/0Wo3coHvRwA/58nYPETx7SkJ
Thanks a lot for your help. I really appreciate it that you recommend me some other documentations to solve the problem.

Best,
Yuxiang

On Friday, September 5, 2014 10:53:31 AM UTC+2, Nicola Baldo wrote:

[Nicola Baldo]

If you really have low traffic, then you will see unused RBs.
Are you sure you have low traffic in your simulation?

[Yuxiang Shen]

Hi, i happen to find that i could get some output information by logging the Mac Scheduler,(e.g. now i'm using PfFfMacScheduler). In the Logfile i get something which may tell me the allocation of the resouce blocks(but i'm not sure...) I remember someone has mentionend in the previous posts, that i should increase the traffic to see some changes. Now i'm using the program based on lena-simple-epc.cc.  I just use a loop to generate the same applications between UE and remoteHost for 10 times. Is it a possible and right way to increase the traffic? But unfortunately, i have seen no changes in the Trace outputfiles...
Could anyone give me some idea? I really appreciate it.

[Rohit Kumar]

Hi.. I would really appreciate if you could let me know the answer of where to find the number of resource blocks allocated to each UE.

It's really important.

Thanks