LTE-based 5G Broadcast over Geosynchronous Satellite

Description

BOG (LTE-based 5G Broadcast over Geosynchronous Satellite) is a technology defined in 3GPP Release 19 that enables the delivery of 5G broadcast/multicast services over geosynchronous satellite. It leverages the LTE-based 5G terrestrial broadcast (also known as LTE-based 5G Broadcast or FeMBMS) and adapts it for satellite transmission, allowing broadcast content to be distributed over wide areas, including regions where terrestrial networks are not deployed. The specifications for BOG are found in 3GPP TS 36.102 (User Equipment (UE) radio transmission and reception for satellite), TS 36.108 (Base Station (BS) radio transmission and reception for satellite), and TS 36.181 (Satellite access network architecture).

In a BOG system, the satellite acts as a broadcast transmitter, sending LTE-based signals to UEs on the ground. The satellite operates in a geosynchronous orbit, which means it appears stationary relative to a point on Earth, simplifying the network architecture and avoiding the need for frequent handovers. The broadcast transmission uses the same physical layer as LTE-based 5G Broadcast, including the use of a single-frequency network (SFN) and the physical multicast channel (PMCH) for carrying multicast/broadcast content. However, the satellite channel introduces unique challenges such as large propagation delay, Doppler shift (though minimal for GEO), and different link budgets. Therefore, 3GPP has defined specific adaptations in the radio interface, such as modified cyclic prefix lengths, enhanced synchronization signals, and adjusted modulation and coding schemes to ensure reliable reception.

The architecture for BOG includes the satellite, a satellite gateway (also called a satellite earth station), and the core network. The satellite gateway connects the satellite to the 5G core network, which manages the broadcast service. The content is delivered from the application server to the core network, then to the satellite gateway, which transmits it to the satellite for broadcast. UEs receive the broadcast directly from the satellite without the need for a return link, making it efficient for one-to-many distribution. The UE must support the satellite frequency band and the necessary receiver capabilities. BOG can operate in various frequency bands allocated for satellite broadcast, such as the L-band or S-band.

BOG is part of the broader 3GPP effort to integrate satellite access into 5G networks, known as Non-Terrestrial Networks (NTN). While NTN typically focuses on bidirectional communication, BOG specifically targets broadcast services, which are important for delivering content like live events, emergency alerts, and software updates to a large number of users simultaneously. The use of satellite for broadcast complements terrestrial broadcast by providing coverage in unserved or underserved areas, such as rural regions, maritime, and disaster zones. It also enables efficient nationwide or regional broadcast without the need for a dense terrestrial network.

In Release 19, BOG is introduced as a new feature, with the specifications defining the necessary radio and architectural aspects. It builds on the existing LTE-based 5G Broadcast ecosystem, allowing reuse of content encoding, service layer, and UE chipsets with modifications for satellite reception. The technology is expected to be deployed in the coming years, with trials and early commercial launches. BOG represents a significant step towards ubiquitous 5G broadcast coverage, leveraging the wide reach of satellites.

Purpose & Motivation

BOG was created to extend the reach of 5G broadcast/multicast services to areas where terrestrial networks are impractical or unavailable. Terrestrial broadcast networks, even with LTE-based 5G Broadcast, require a dense network of transmitters to cover large geographic areas, which is costly and difficult in remote regions. Satellite broadcast can cover vast areas with a single transmitter, making it ideal for rural, maritime, and disaster-stricken areas. BOG leverages the existing LTE-based 5G Broadcast technology, which was standardized in 3GPP Release 14 and later, to provide a cost-effective solution for satellite broadcast. It addresses the need for efficient one-to-many content delivery, such as live TV, emergency alerts, and IoT software updates, without consuming terrestrial network resources. By using geosynchronous satellites, BOG simplifies UE design and network synchronization, as the satellite appears stationary. This technology is motivated by the growing demand for ubiquitous 5G services and the need to bridge the digital divide.