4G and 5G Spectrum & Modulation Basics

4G and 5G spectrum

4G LTE commonly uses sub-3 GHz spectrum, while 5G uses both FR1 (sub-6 GHz) and FR2 millimeter-wave bands, with FCC rule changes opening substantial mmWave spectrum for 5G and other advanced services. Small cells are often used to deploy both 4G and 5G, and FCC/local rules heavily affect how quickly and where those can be installed. telit

Modulation basics

"Modulation" is how information is placed onto a radio carrier by varying amplitude, frequency, or phase. In cellular systems, the important idea is that the network uses digital modulation schemes to move data efficiently over the assigned carrier frequencies. documentation.meraki

4G vs 5G modulation

4G LTE and 5G NR both use OFDM-family waveforms, with 5G NR using CP-OFDM broadly and DFT-s-OFDM in some uplink cases; the data symbols are commonly carried with QPSK, 16QAM, 64QAM, and 256QAM depending on conditions. So while "FM" is a classic analog concept, modern cellular is mostly about digital OFDM/QAM-based modulation, not broadcast-style frequency modulation. electronics-notes

Useful mental model

Think of FCC rules as answering three questions: Who may use the spectrum, how much energy can they radiate, and how do we prevent interference and unsafe exposure? The modulation method answers a separate question: how the bits are packed onto that radio wave. crows