Digital Video Broadcasting - Terrestrial

Description

Digital Video Broadcasting - Terrestrial (DVB-T) is a DVB standard specifying the physical layer transmission system for terrestrial digital television. It uses Coded Orthogonal Frequency Division Multiplexing (COFDM) modulation to combat multipath interference and provide robust reception in challenging environments. Within 3GPP, DVB-T is referenced in the context of broadcast service delivery, particularly for MBMS/eMBMS over terrestrial broadcast networks or as a supplemental downlink technology for cellular networks.

The technology works by dividing the digital data stream into thousands of slower sub-streams, each modulated onto a separate subcarrier within the OFDM symbol. This provides resilience against frequency-selective fading and allows for single-frequency networks (SFNs) where multiple transmitters broadcast the same signal on the same frequency, improving coverage and spectral efficiency. Key components include the channel coding (convolutional and Reed-Solomon), interleaving, and the OFDM modulator with configurable parameters like 2k or 8k mode, guard interval, and modulation schemes (QPSK, 16QAM, 64QAM).

In a 3GPP-integrated scenario, DVB-T can be used as a broadcast bearer for delivering multimedia content to 3GPP devices equipped with DVB-T receivers. This enables hybrid broadcast-broadband services where the broadcast network delivers high-bandwidth content (like live TV) and the cellular network provides interactivity and personalization. For 5G, DVB-T is studied for supplemental downlink to boost downlink capacity in dense urban areas or for fixed wireless access, leveraging existing broadcast infrastructure.

Purpose & Motivation

DVB-T was developed to enable the digital switchover from analog terrestrial television (PAL, SECAM) across Europe and other regions. It solved the problem of inefficient spectrum usage and poor picture quality of analog TV, while providing immunity to ghosts and interference. The motivation was to free up spectrum (the digital dividend) for other services like mobile broadband, while offering viewers more channels and features like electronic program guides.

From a 3GPP perspective, the purpose of referencing DVB-T is to explore the use of broadcast spectrum and infrastructure for offloading high-demand downlink traffic, especially for popular live video content. This addresses the limitation of cellular spectrum scarcity during mass events. By potentially using DVB-T as a supplemental downlink in 5G networks, operators can enhance capacity and user experience without deploying additional cellular sites, leveraging the wide coverage of broadcast towers.

Key Features

• COFDM modulation with 2k/8k modes for flexibility
• Support for Single Frequency Networks (SFN) for efficient spectrum use
• Hierarchical modulation allowing two independent streams (HP/LP)
• Robust channel coding (convolutional + Reed-Solomon)
• Configurable guard intervals to combat long echo delays
• Support for MPEG-2 and later H.264/AVC and HEVC video coding

Evolution Across Releases

Defining Specifications