It is recommended to read OFDMA/SC-FDMA sections to clearly understand throughput calculation in LTE.
Let’s assume, the UE is in good radio condition and its capability is available for 150 Mbps for downlink and 50 Mbps for uplink. In good radio condition 64QAM modulation will be used for downlink. Actually the calculation is too simple, just need to calculate total number of bits in whole physical resource blocks and exclude overhead such as physical channels, reference and synchronization signals etc.
Characteristics of OFDMA/SC-FDMA system:
🔘 LTE Radio Frame duration = 10ms
🔘 Sub-frame duration = 1ms
🔘 Time Slot duration = 0.5ms
🔘 Symbol duration = 0.5ms / 7
🔘 Symbol count = 7 in normal CP
🔘 Subcarrier bandwidth = 15 KHz
🔘 Subcarrier count in one PRB = 12
🔘 Transmission Time Interval = 1ms (minimum scheduling time for user, 2 PRB at once)
Downlink Throughput
System availability:
🔘 Modulation = 64QAM (6 bits can be carried on each RE with this modulation)
🔘 Antenna = 2T2R MIMO
🔘 Bandwidth = 20MHz (100 PRB and 1200 subcarriers are exist in 20MHz)
1. Number of bits in one PRB = subcarriers * symbols * bits = 12 * 7 * 6 = 504 bits (0.5ms)
2. Minimum scheduling for user = 504 bits (0.5ms) + 504 bits (0.5ms) = 1008 bits per ms
3. Number of bits in whole bandwidth = #PRB * bits = 100 * 1008 = 100800 bits per ms
4. Transmission is 2T2R MIMO = 2 * 100800 = 201600 bits per ms by two transmission
5. Other channels, occupy 25% of whole resource = 151200 bits per ms = 151.2 mbps
Uplink Throughput
System availability:
🔘 Modulation = 16QAM (4 bits per RE, most of the commercial UE support max 16QAM)
🔘 Antenna = 1T1R SISO
🔘 Bandwidth = 20MHz (100 PRB and 1200 subcarriers are exist in 20MHz)
1. Number of bits in one PRB = subcarriers * symbols * bits = 12 * 7 * 4 = 336 bits (0.5ms)
2. Minimum scheduling for user = 336 bits (0.5ms) + 336 bits (0.5ms) = 672 bits per ms
3. Number of bits in whole bandwidth = #PRB * bits = 100 * 672 = 67200 bits per ms
5. Other channels, occupy 25% of whole resource = 50400 bits per ms = 50.4 Mbps