LTE ressource allocation

[El Kinani Youssef]

Hi everybody,

I'm using the lena-simple-epc.cc to study how ressource are allocated in lte, and try to trace a blocking probability. I'm a little bit confused about the number of prbs that are allocated to each Ue, and I want to know why it varies 12,9,5,4. I'm using a scenario with 10 Ues that generates a 1Mbps udp traffic to a remote Host (OnoffApp), I set the bandwidth to 100. And I have attached the UlMacStats.txt file. Any explanation or link to docuentation will be helpfull.

Thanks in advance
Youssef

[Lorenza Giupponi]

Hi,

the number of PRBs allocated to the UEs is a decision made by the scheduler. It may easily happen that varies, depending on the scheduler policy,

Lorenza

2016-05-11 16:27 GMT+02:00 El Kinani Youssef <yousssef...@gmail.com>:

Le mercredi 11 mai 2016 15:22:19 UTC+1, El Kinani Youssef a écrit :

Hi everybody,

I'm using the lena-simple-epc.cc to study how ressource are allocated in lte, and try to trace a blocking probability. I'm a little bit confused about the number of prbs that are allocated to each Ue, and I want to know why it varies 12,9,5,4. I'm using a scenario with 10 Ues that generates a 1Mbps udp traffic to a remote Host (OnoffApp), I set the bandwidth to 100. And I have attached the UlMacStats.txt file. Any explanation or link to docuentation will be helpfull.

   I suspect that this is related to RBG, but why the number of RBs in a group changes like that. 

Thanks in advance
Youssef

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[El Kinani Youssef]

Hi
Thank you for your response, I want to know what is the best MAC scheduler to use for LTE (best in terms of reproducing approximately the reality). Also I want to know if there is a parametre that gives the number of Ues that failed to have ressources (Ues blocked in a specific time interval)?

Cheers
Youssef

[Lorenza Giupponi]

Hi,

schedulers are proprietary, so it is hard to say which one is more realistic. Proportional fair could be a basic option, this one https://www.nsnam.org/docs/models/html/lte-design.html#channel-and-qos-aware-scheduler is probably the smarter that is available. It depends on what you need to do.

If a UE is not given any PRB in a given TTI, it will be most probably given in the next one, it is not as if it was blocked, I am not aware of an output of the simulator with this information.

Lorenza

[El Kinani Youssef]

Thank you for your reply, It was very helpfull.

[El Kinani Youssef]

Hello,

So if there is only a limited number of Ues that can receive ressources in TTI, if yes where can I get this information ?


Thanks in advance
Best Regards
Youssef

[Lorenza Giupponi]

It depends on the specific scheduler, each one has a different policy and will affect the way users are allocated to TTIs. It may vary from one TTI to another depending on many things happening in the channel. The documentation on MAC, resource allocation and schedulers is here: https://www.nsnam.org/docs/models/html/lte-design.html#mac

[El Kinani Youssef]

Hi,

Thank you Lorenza for your helpfull replies, and now I have a good understanding of what's happening in ressource allocation. And regarding the blocking probability I was trying to calculate, I'm wondering even if there is a possibility that a Ue don't get any ressource, because as you said: if a Ue don't have a ressource in a TTI, he will probably get the ressources in the next TTI. So is this realistic ? Is this a matter of traffic differentiation (simulate different types of traffics instead of a CBR ) ?  This really seems weird, without mentionning the SRS periodicity that  blocks you from augmeting the number of Ues. Am I missing something, or dealing with the problem the wrong way ? Any help or advise  would be really great, because I need to know the blocking probability to compare the basic lte network, with a relay-based one?

Thanks in advance
Youssef

[lorenza....@gmail.com]

Hi,

Depending on the scheduler it can happen that a UE is not assigned RB in a given TTI, and then they are scheduled in the next TTI. It is realistic, it just depends on the scheduler policy, which again, is vendor dependent. It does not mean you are blocking a UE.

The number of UEs can be improved by playing with SRS,

Lorenza

Inviato da iPhone

[Danny Xu]

HI Youssef,

I saw your MAC.txt include PRB, how to do it ?

I use enablemactrace, it hadn't this cloumn.

Thanks

Danny

在 2016年5月11日星期三 UTC+8下午10:22:19，El Kinani Youssef写道：

[Shyam Parekh]

I can't find any reply to this query by Danny. I have the same question. Please help.

Shyam

[Zoraze Ali]

Hi Shyam,

He modified the uplink scheduling trace source (https://gitlab.com/nsnam/ns-3-dev/-/blob/master/src/lte/model/lte-enb-mac.cc#L367). Please, read the LTE user documentation.

Kind regards,

Zoraze

[Theresal T]

hi youssef..

i hope u will tell me how to get the output like in ur file ... i am not getting output like that while i am running the same code.. which version u r using ...pls suggest me which version is best to do LTE module