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LTE : What information is sent in buffer status report from UE to eNodeB ?

0 votes

I know buffer status report is sent from UE to eNodeB to request for UL resources. Can someone please explain how many types of buffer status reports have been defined till now and in what scenarios each one is used ?

posted Sep 9, 2016 by Harshita

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1 Answer

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Hi harshitha,

The following are BSR types :
Based on frequency of Transmission there are two types .. one is periodic and another is aperiodic.

Short BSR :
If the BSR is avilable for only one LCG then UE will send short BSR i.e only 8bits of BSR.For the required bytes of grant corresponding index in defined in MAC spec so UE will send index to enb (0 to 63).

Long BSR :
If the BSR is available for more than one LCG then UE will send Long BSR, That is MAX of 24bits which will represent the MAX of 4LCG BSR.

Padding BSR :

To send the BSR ENB will give grant , padding = (grant - (BSR +Header ) if padding is greater than BSR size then it will be called as padding BSR.

Periodic BSR is timer based BSR which will be configured by upper layers. aperiodic BSR is whenever UE has data it will send.

answer Sep 12, 2016 by Jaganathan
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+5 votes

Each carrier in LTE is 15khz so in a calculation i found that useful symbol time = 1/15khz = 66.6 mircosec

wrt to this
Each symbol duration is calculated like this
Normal Cyclic Prefix length = 4.69 microsec --- so each symbol in this = 66.6 + 4.69 = 71.29 microsec
Extended Cyclic Prefix length = 16.67 microsec ----so each symbol in this = 66.6 + 16.67 = 83.27 microsec

So Normal cyclic prefix Slot (7 symbols) duration = 71.29 * 7 = 499.03 microsec(0.49903 millis)
and Extended cyclic prefix Slot (6 symbols) duration = 83.27 * 6 = 499.63 microsec (0.49963 millis)

But slot duration is fixed as 0.5 ms ...

So does this slight difference creates any problem ???
How real time it works ???

+7 votes

I want to know formulated explanation..Basic is clear for me. How to implement it for LTE..any document and white paper links are welcomed. I am working on C Language.

0 votes

I did not get the use of different RV values that come from eNodeB to UE.

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