What is Tx?
Tx (Transmit) in wireless communications refers to the process of sending data through the air from one device to another. The transmit chain in a 5G device or base station includes baseband digital processing (coding, modulation, MIMO precoding), digital-to-analog conversion, up-conversion to RF, power amplification, filtering, and antenna radiation. Tx performance — characterised by output power, EVM, ACLR, and SEM — determines the coverage range, data rate, and spectral compatibility of the wireless system.
How Does Tx Work?
The Tx chain begins with baseband processing: channel coding (LDPC/Polar), modulation mapping (QPSK to 256-QAM), layer mapping, precoding (for MIMO/beamforming), resource element mapping, and OFDM signal generation (IFFT + CP insertion). The resulting complex baseband signal is converted to analog (DAC), up-converted to the target RF frequency using a mixer and LO, amplified by the PA, filtered to meet SEM requirements, and radiated by the antenna. Key Tx specifications include: maximum output power (23 dBm typical for UE, up to 200W per TRX for macro gNB), EVM (must meet modulation-specific limits), ACLR (minimum dB requirement per band), and spurious emissions.
Use Cases
5G NR UE and base station transmitter design, transmit power control and optimization, EVM and ACLR compliance testing, coverage range determination, and energy efficiency optimization for base stations.
3GPP / Standards Reference
3GPP TS 38.101 (NR UE Tx requirements), 3GPP TS 38.104 (NR BS Tx requirements)
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
