4G/LTE - Throughput

Throughput Calculation - TDD

TDD throughput calculation is very similar to FDD case as you see below. The key difference is 'number of subframes /sec' parts as marked in red. Another difference is about TBS each subframe as marked in blue. In normal DL or UL subframe, TBS/subframe can be calculated in the same way as in FDD. But in case of special subframe, the method is a little bit different. I will explain on this later.

PHY layer throughput in bits =   Transport Block Size (bits) / subframe

                                         x number of transport blocks / subframe

                                         x (number of subframes carrying TB) / sec

                                       =  ???? bits/sec

        , where number of transport blocks /subframe is 1 for TM1,TM2 and 2 for TM3, TM4

Calculation Procedure for downlink(PDSCH) is as follows :

i) refer to TS36.213 Table 7.1.7.1-1

ii) get I_TBS for using MCS value (Let's assume MCS is 23. in this case, I_TBS is 21 )

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 100)

v) go to row header ‘21’ which is I_TBS

vi) you would get 51024 (if the number of RB is 100 and I_TBS is 21)

vii) (This is Transfer Block Size per 1 ms for one Antenna)

viii) Figure out the 'number of subframe' based on UL/DL Configuration and Special Subframe Configuration. (= N_SF)

If we use 2 antenna, the throughput is 51024 bits * 2 transport blocks * N_SF/sec 

Calculation Procedure for uplink(PUSCH) is as follows :

Same as the downlink as above except that you have to refer to 36.213 Table 8.6.1-1 at step i)

Uplink Analysis Paremeter Calculation

Click here for TS 36.213 Tables for TBS

Number of subframes carrying TB

Following Table shows the number of DL, UL and Special Subframe (Sync Subframe) within a radio frame (10 ms). Figure out 'Number of Subframe Carrying TB'. However there is a tricky part here. D and U part are straight forward and they can carry TB as we expected, but 'S' subframe is different. I may or may not carry TB (PDSCH) depending on Specifical Subframe Configuration. We will look into TB allocation for 'S' subframe in next table.

Special Subframe Configuration for TB allocation

Special Subframe Configuration marked in Green can carry PDSCH, but the ones marked in Gray cannot carry PDSCH. You have to take this into acount when you are calculating 'Number of subframes carrying TB'