Spectrum Efficiency Calculator
Peak spectral efficiency and data rate for 2G GSM, 3G HSPA+, 4G LTE, and 5G NR.
Spectral Efficiency Formula
Spectral efficiency (SE) measures how efficiently a channel uses its bandwidth, in bits per second per Hz (bps/Hz). Peak SE for a MIMO system is calculated as:
SE = Nlayers × bits/symbol × code rate × (1 − overhead)
Peak Rate (Mbps) = SE × Bandwidth (MHz)
Shannon limit: C = B · log₂(1 + SINR)
The Shannon limit gives the theoretical maximum capacity for a given bandwidth and SINR. Practical systems fall below this limit due to modulation constraints, channel coding overhead, guard intervals, and pilot signals.
Frequently Asked Questions
What is spectral efficiency?▾
Spectral efficiency is the information rate that can be transmitted over a given bandwidth, measured in bits per second per hertz (bps/Hz). Higher spectral efficiency means more data can be transmitted in the same amount of spectrum. 4G LTE achieves around 16 bps/Hz with 256QAM 4×4 MIMO, while 5G NR can reach over 30 bps/Hz with 256QAM 8-layer MIMO.
How does MIMO improve spectral efficiency?▾
MIMO (Multiple-Input Multiple-Output) uses multiple antennas to transmit independent data streams simultaneously on the same frequency. Each spatial layer multiplies the peak data rate — 4×4 MIMO delivers up to 4 times the throughput of a single antenna at the same bandwidth, provided the propagation channel supports it.
What is modulation order and why does it matter?▾
Higher-order modulation encodes more bits per symbol: QPSK = 2 bits/sym, 16QAM = 4, 64QAM = 6, 256QAM = 8, 1024QAM = 10. More bits per symbol increase peak throughput but require a higher SINR. 256QAM typically needs SINR > 20 dB, while QPSK works at very low SINR (close to 0 dB).
What is the difference between peak rate and average throughput?▾
Peak rate is the theoretical maximum under ideal conditions — full buffer, maximum MIMO rank, best modulation, no interference. Real-world average throughput is typically 30–60% of peak due to scheduling gaps, retransmissions, interference, mobility, and cell loading.