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Resource Block calculation

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Hi,

I just wanted to know how number of resource block calculation is done,
i mean to say:

System BW Number of RBs

1.4 6
3 15
5 25
10 50
and so on

posted Sep 6, 2017 by Sushant Bose

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1 Answer

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Best answer

Hi,

Each in LTE we have one resource block = 12 subcarriers * 7 OFDM sybolms
Each subcarrier is 15khz hence in total 12*15= 180khz each resource block

For example, lets take 3MHZ BW as per LTE spec it have 15RBs

lets calculate this .... 180khz*15 = 2700khz = 2.7MHZ

Among our 3MHZ BW 2.7MHZ only used for actual data transmission. Remaining 0.3MHZ can be used to guard subcarriers.

Hence in any BW all the spectrum cant be used for data transmission.

Regards,
Suchi

answer Sep 7, 2017 by Suchakravarthi Sripathi
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+1 vote

I would like to understand the relation between the TB size calculation in the TS36.213 document and in the Vienna Simulator https://www.nt.tuwien.ac.at/research/mobile-communications/vienna-lte-a-simulators . I’m going to make an example so maybe you can help me to see this relation:

Method 1 (from the TS36.213)

Calculation Procedure for downlink(PDSCH) is as follows :
i) refer to TS36.213 Table 7.1.7.1-1
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iii) refer to TS36.213 Table7.1.7.2.1
iv) go to column header indicating the number of RB (Let’s assume that RB is 50)
v) go to row header ‘1’ which is I_TBS
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And this is method 2 (in the simulator):
i) This is the formula:
TB_size_bits = max(8*round(1/8*(the_RB_grid.sym_per_RB_nosync .* num_assigned_RB .* modulation_order .* coding_rate * 2))-24,0);
ii) if the_RB_grid.sym_per_RB_nosyn= 80
iii) num_assigned_RB=50
iv) modulation_order = 2
v) coding_rate=0.0762
vi) That gives TB_size_bits = 11952 bits

Do you know how I can go from one method to another or if there is any relation?

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