SFN (Single-Frequency Network (in general, see also MBSFN) or System Frame Number (in 3GPP).)

SFN, in the context of wireless communication systems, stands for Single-Frequency Network. It is a technique used to improve the coverage and capacity of broadcasting systems, particularly in digital terrestrial television (DTT) and cellular networks. SFN is also associated with the term MBSFN (Multicast Broadcast Single-Frequency Network) in the broadcasting domain, which is an extension of SFN for efficient multicast services.

In an SFN, multiple transmitters or base stations located in different geographic areas transmit the same content simultaneously using the same frequency. Unlike traditional multi-frequency networks where each transmitter uses a different frequency, SFNs utilize a single frequency across all transmitters. The synchronized transmission of signals allows receivers within the SFN coverage area to combine the signals received from different transmitters, resulting in improved reception quality and coverage.

SFNs offer several advantages over multi-frequency networks:

1. Improved coverage: By utilizing multiple transmitters, SFNs can provide better coverage, especially in areas with challenging terrains or urban environments with obstacles that may block the signals from a single transmitter. The combined signals from multiple transmitters compensate for signal degradation and improve reception in shadowed areas.
2. Increased capacity: SFNs can enhance the capacity of the network by reusing the available frequency spectrum efficiently. Since multiple transmitters operate on the same frequency, the available spectrum can be utilized simultaneously in different geographic areas without causing interference. This allows for higher data rates and more users to be served within the network.
3. Reduced interference: SFNs are designed to minimize interference between transmitters operating on the same frequency. The transmitters are carefully synchronized to avoid signal overlap and prevent co-channel interference. By coordinating the transmission timing and power levels, SFNs can mitigate interference and maintain signal quality.

In the context of 3GPP (3rd Generation Partnership Project), SFN can also refer to System Frame Number. The System Frame Number is a parameter used in 3GPP specifications to identify the frame number within a radio frame structure. It is primarily used for synchronization and timing purposes in cellular networks, such as LTE (Long-Term Evolution) and 5G NR (New Radio). The SFN allows network elements and user equipment (UE) to synchronize their operations and maintain timing consistency within the network.

The System Frame Number is a cyclic counter that increments with each radio frame. It provides a reference point for scheduling, resource allocation, and various operations in the network. The SFN value is broadcasted by the network, and UEs use this information to align their activities with the network's timing. By synchronizing their operations based on the SFN, UEs can accurately transmit and receive data, ensuring efficient communication within the cellular network.

Overall, SFN (Single-Frequency Network) is a technique that enables the simultaneous transmission of the same content from multiple transmitters using a single frequency. It improves coverage, capacity, and reduces interference in broadcasting systems and cellular networks. In 3GPP, SFN also refers to the System Frame Number, which is a parameter used for synchronization and timing purposes within the cellular network.