Transport Block calculation in LTE Downlink
I found this ppt: http://www.ece.drexel.edu/walsh/Gwanmo-Nov11-2.pdf (slides 9-12) where I saw a bit of light regarding on how the method 1 calculates TB size:

For data, there are:

10 OFDM symbols per subframe x 12 subcarriers = 120 (we are counting the 6 RS symbols and excluding the PDCCH symbols)

Therefore,

120 symbols x 50 RBs x 2 bits/symbol (QPSK) = 12000 bits

For QPSK we know that the efficiency is 0.15 (approx.), so:

12000 x 0.15 = 1800 bits, as in table Table7.1.7.2.1 3GPP TS 36.312 for 50 RBs and I_TBS=1 (sorry, in my question I made a mistake and wrote I_TBS 9 the second time: can’t edit it in the forum)

However, in the simulator, using method 2, we are considering:

Number of non-sync symbols per RB= 12×7 – 4 (RS symbols)=80 OFDM symbols per slot

80 non-sync symbols x 50 RBs x 2 bits/symbol x 0.0762 x 2 slots =1219 bits

1219 bits -24 bits for the CRC = 1195 bits :)

Please, let me know if you don’t agree with these methods.

Thanks,

BTS.