OFDM (Orthogonal Frequency-Division Multiplexing) - definition

OFDM (Orthogonal Frequency-Division Multiplexing) is an advanced technique modulation and multiplexing, used in digital transmission systems, which involves the simultaneous transmission of data using multiple mutually orthogonal carriers at different frequencies. Each of these carriers is modulated independently, usually using QAM or PSK modulation, which allows multiple pieces of information to be transmitted in parallel within a single transmission channel.

A characteristic feature of OFDM is the use of the orthogonality of the carrier signals, which means that their frequencies are selected so that they do not interfere with each other, despite the partial overlap of the spectra. This makes it possible to use the available bandwidth very efficiently, while limiting inter-channel interference (ICI). OFDM-based transmission is immune to multipath, i.e. the phenomenon of delay and interference caused by signal reflections, which makes it particularly suitable for environments with high propagation variability, such as wireless networks.

The technique is widely used in modern telecommunications systems, including the standards Wi-Fi, LTE, 5G NR, DVB-T/T2, DAB and DSL broadband technologies. One of the key implementation elements of OFDM is the use of the Fast Fourier Transform (FFT) and its inverse (IFFT), which allow for efficient signal conversion between the frequency and time domains.

OFDM offers great flexibility in the choice of transmission parameters, such as the number of carriers, bandwidth or modulation type, allowing the system to be dynamically adapted to channel conditions and user requirements. However, it requires precise frequency and time synchronisation, as well as advanced error correction methods to ensure high reliability and quality of data transmission under real-world conditions.

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