LTE Throughput & Resource Grid Calculator
LTE throughput from the 3GPP TS 36.213 transport block size tables, checked against the resource grid of TS 36.211.
Free to use. Sign up free to save, download and print.
Worked example: 20 MHz FDD, MCS 28, two layers
Peak throughput: 150.752 Mbit/s
Loading the LTE Throughput & Resource Grid Calculator…
How it works
LTE throughput calculation from the transport block size
LTE throughput is set by the transport blocks a base station sends in each 1 ms subframe, and their size is read from a table in TS 36.213 rather than worked out from the modulation. The channel bandwidth sets the resource blocks, the MCS sets the modulation and a transport block size index, and the table gives the block for that index and the resource blocks allocated. From two layers on, two codewords are sent, each sized for the layers it carries.
The resource grid is the check. The control region, the cell specific reference signals and the synchronisation and broadcast channels come out of the downlink grid, and the demodulation reference signal out of the uplink. The effective code rate compares each block and its CRC bits with what is left: above 1 the block cannot be sent, and above 0.932 in the downlink a terminal may skip decoding it (TS 36.213 clause 7.1.7). In TDD the block in the downlink part of a special subframe is read at fewer resource blocks but sent in fewer symbols, so it is checked on that shorter grid too.
R = 100 × (N_sf × ΣTBS + N_S × ΣTBS_S)
N_RE = 12 × 14 × N_PRB − N_ctrl − N_RS − N_sync
CR = (TBS + CRC) / (N_RE × Qm × v)
CRC = 24 if TBS + 24 ≤ 6144, else 24 + 24 × ⌈(TBS + 24) / 6120⌉
- R
- throughput in bit/s, averaged over the 10 ms frame; 100 is the frames in a second
- TBS
- transport block of each codeword, in bits, from TS 36.213 Table 7.1.7.2.1-1 at I_TBS and N_PRB; a codeword on two to four layers is read at that many times N_PRB on small allocations and from Tables 7.1.7.2.2-1, 7.1.7.2.4-1 and 7.1.7.2.5-1 on large ones (clause 7.1.7.2)
- I_TBS, Qm
- transport block size index and bits per symbol (2, 4, 6 or 8) for the MCS, from TS 36.213 Table 7.1.7.1-1, Table 7.1.7.1-1A with 256QAM, or Table 8.6.1-1 in the uplink
- N_PRB
- resource blocks allocated: up to 6, 15, 25, 50, 75 or 100 in 1.4, 3, 5, 10, 15 or 20 MHz (TS 36.101 Table 5.6-1), less the PUCCH region in the uplink
- N_sf
- subframes in each frame carrying the direction: 10 in FDD, or the downlink or uplink count of the TDD configuration
- N_S, TBS_S
- TDD special subframes and the downlink transport block in their DwPTS, read at max(⌊0.75 × N_PRB⌋, 1) resource blocks, 0.375 × N_PRB for special subframes 9 and 10, and none for 0 and 5, with a normal cyclic prefix (TS 36.213 clause 7.1.7)
- N_RE
- data resource elements in a subframe: 12 subcarriers by 14 symbols in each resource block with a normal cyclic prefix, or 12 symbols with an extended one
- N_ctrl, N_RS, N_sync
- the control region; the reference signals outside it, or in the uplink the demodulation reference signal, one symbol per slot; and PSS, SSS and PBCH averaged over the frame (TS 36.211)
- v
- layers on the codeword
- CRC, CR
- the 24-bit transport block CRC (TS 36.212 clause 5.3.2) and a 24-bit CRC on each code block above 6144 bits (clause 5.1.2); and the effective code rate
Standards
- 3GPP TS 36.213 clause 7.1.7.2 and Tables 7.1.7.2.1-1, 7.1.7.2.2-1, 7.1.7.2.4-1 and 7.1.7.2.5-1: transport block sizes on one to four layers, and clause 7.1.7 for DwPTS
- 3GPP TS 36.213 Tables 7.1.7.1-1, 7.1.7.1-1A and 8.6.1-1: MCS tables, and clause 8.6.1 for uplink modulation
- 3GPP TS 36.211: resource grid and frame structure, including Tables 4.2-1 and 4.2-2, and clause 5.3.3 for uplink allocation sizes
- 3GPP TS 36.212 clause 5.3.2: transport block CRC
- 3GPP TS 36.101 Table 5.6-1: channel bandwidth to resource blocks
- 3GPP TS 36.306 Tables 4.1-1 and 4.1-2: UE category limits
- 3GPP TR 36.942 Annex A.1: throughput against SINR
Worked example
Worked example: 20 MHz FDD, MCS 28, two layers
A 20 MHz FDD downlink with all 100 resource blocks at MCS 28 of TS 36.213 Table 7.1.7.1-1 (64QAM, I_TBS 26) on two layers, with two reference signal antenna ports and a one-symbol control region.
| Step | Working | Result |
|---|---|---|
| Transport block, one layer | I_TBS 26 at 100 resource blocks | 75,376 bits |
| Two layers, two codewords | 2 × 75,376 | 150,752 bits |
| Data resource elements | 16,800 − 1,200 − 1,200 − 48.8 | 14,351.2 |
| Effective code rate | (75,376 + 336) / (14,351.2 × 6 × 1) | 0.879 |
| Peak throughput | 100 × 10 × 150,752 | 150.752 Mbit/s |
The code rate of 0.879 is under 0.932, so each block can be decoded. With a three-symbol control region the data resource elements fall to 11,951.2 and the code rate rises to 1.056, so the same transport block no longer fits and cannot be sent at this MCS.
How many resource blocks are in an LTE channel?
TS 36.101 Table 5.6-1 gives 6 resource blocks in 1.4 MHz, 15 in 3 MHz, 25 in 5 MHz, 50 in 10 MHz, 75 in 15 MHz and 100 in 20 MHz. A resource block is 12 subcarriers of 15 kHz, 180 kHz wide, by 7 symbols in each 0.5 ms slot with a normal cyclic prefix, or 6 with an extended one, so a 20 MHz carrier has 16,800 resource elements in each 1 ms subframe before any overhead.
What is the maximum LTE throughput in 20 MHz?
On one 20 MHz FDD downlink with all 100 resource blocks, two reference signal ports and a one-symbol control region, MCS 28 (64QAM) gives 75.376 Mbit/s on one layer and 150.752 Mbit/s on two, which is also the most a Category 4 terminal takes (TS 36.306). Four layers with four reference signal ports give 299.552 Mbit/s, and two layers at MCS 27 of the 256QAM table (TS 36.213 Table 7.1.7.1-1A) give 195.792 Mbit/s. On TDD configuration 2 with special subframe 7, the two-layer 64QAM figure is 112.474 Mbit/s. Each is a peak for one terminal given the whole carrier.
Why look the throughput up instead of calculating it?
Because that is what the base station does. TS 36.213 Table 7.1.7.2.1-1 gives the transport block size for every combination of transport block size index and allocated resource blocks, and the scheduler reads it. The table is not a smooth function, so a fitted formula is wrong in places.
What is the effective code rate check for?
It catches combinations that cannot be transmitted. Each transport block and its CRC bits must fit in the data resource elements times the bits per symbol and layers. Above a code rate of one it does not fit, and in the downlink above 0.932 TS 36.213 lets a terminal skip decoding it. On TDD the downlink part of each special subframe is checked as well, because its block can fail where a full subframe fits.
Can it tell me which MCS I will get at a given SINR?
No. 3GPP publishes the CQI and MCS tables but not a mapping from SINR to either, because that depends on the equipment. The calculator uses the throughput against SINR model in 3GPP TR 36.942 Annex A.1 instead.
Is this the throughput I will measure in the field?
No. The scheduled peak is what the grid carries if it is scheduled this way, and HARQ retransmissions and scheduler behaviour are not modelled. The rate at a stated SINR comes from a published 3GPP link model rather than a measurement. Treat both as what the configuration allows, not as a prediction.
Related
Related tools
-
LTE Link Budget & MAPL CalculatorPrivate Cellular -
LTE TDD Frame Configuration PlannerPrivate Cellular -
Private Cellular Network PlannerComing soon
Sign up free to keep your work.
Free to use. Saving, downloading and printing need a free account.