Digital Video Broadcasting via Satellite: DVB-S2/S2X Standards for HDTV and Broadband Satellite Networks

Rajesh Uppal 2 weeks ago Comm. & NW, Space Comments Off on Digital Video Broadcasting via Satellite: DVB-S2/S2X Standards for HDTV and Broadband Satellite Networks 415 Views

The evolution of digital video broadcasting via satellite has seen significant advancements with the introduction of the DVB-S2 and DVB-S2X standards. These standards have revolutionized HDTV broadcasting and broadband satellite networks by enhancing efficiency, reliability, and performance. This blog post explores the key features, technological advancements, and applications of DVB-S2 and DVB-S2X in modern satellite communications.

Overview of Satellite Broadcast Networks

A satellite broadcast network consists of a transmitting hub station and multiple receive-only earth stations, utilizing one or more channels (transponders) of a communications satellite. The network relies on a star topology and point-to-multipoint connectivity. The links are unidirectional, transmitting from the hub to the earth stations.

The hub is generally a large earth station, while the receive-only earth stations can be very small, with typical antenna sizes around 0.5 meters. The low cost of these small earth stations (less than 100 Euros) makes them affordable for end-users who wish to receive television or audio programs directly from a satellite, known as Direct to Home (DTH) service. The hub can be located either at the broadcaster’s facilities or at another location operated by the satellite operator. The uplink from the hub is called a feeder link, and the hub is often referred to as the feeder earth station.

An evolution of this architecture involves introducing interactivity with a low data rate return link from the earth stations to the hub, enabling interactive TV (iTV) or video-on-demand services.

DVB Standards: From DVB-S to DVB-S2/S2X

The European Telecommunications Institute (ETSI) is a non-profit organisation that creates standards for different areas of telecommunications. A standardised radio interface enables a mass market for consumer reception devices. Having in mind the many past issues resulting from the different analogue TV standards and its multiple variations, most of the actors (broadcasters, service providers, operators, equipment and chips manufacturers, etc.) worked together at the end of the 1980s to define a digital video broadcasting (DVB) standard. This standard has been broken down into different versions depending on the specific properties of the transmission channel
which conditions the physical layer characteristics: DVB-T for terrestrial digital TV, DVB-C for cable, DVB-S for satellite. Later standards have been introduced: DVB-RCS for the return channel, DVB-S2 (the second generation of DVB-S), DVB-H for handheld terminals, DVB-SH for satellite handheld terminals, etc.

Although the DVB-S standard was designed initially for satellite digital television services, the physical layer of the DVB-S can carry streams of packetised data of any kind. Mass-market production, and the availability of different equipment and related building blocks, makes the
standard appealing for a lot of applications other than the transmission of TV signals, such as Internet traffic.

DVB standards are essential for delivering satellite television services worldwide. The first DVB transmission specification, DVB-S, became the most popular system for digital satellite television. DVB-S supported compressed digital TV requiring a carrier bandwidth smaller than a transponder’s typical bandwidth, allowing options such as Multiple Channel Per Carrier (MCPC) and Single Channel Per Carrier (SCPC). However, FDMA access required satellite transponders to operate with some back-off, which could affect service quality unless larger earth stations or modern satellites with higher EIRP were used.

The DVB-S standard uses QPSK modulation and concatenated convolutional and Reed–Solomon channel coding. It has been adopted by most satellite operators worldwide for television and data broadcasting services.

However, as usual with FDMA, the satellite transponder must be operated with some back-off, i.e. at reduced EIRP with respect to the maximum EIRP at saturation, which may penalise the quality of the service, unless the end customer uses a larger (and more costly) earth station, or modern satellites with very large EIRP are considered. To benefit from the maximum satellite EIRP, it is preferable to avoid FDMA access by the feeder links, and use the full channel bandwidth with a single carrier (as with Option 1) conveying a time division multiplex (TDM) of programmes from several broadcasters. With a regenerative satellite and on-board processing, it is possible tomultiplex the programmes on board the satellite.

The system also supports direct-broadcast satellite television from providers such as Sky, Astra, Dish Network, Globecast and Bell TV. Digital satellite transmission technology has evolved significantly in several areas since the first publication of the DVB-S standard in 1994. With advances in technology, and the need for higher speeds and throughputs, the DVB-S standard needed to be advanced.

DVB-S2: Advancements and Features

DVB-S2 (Digital Video Broadcasting – Satellite – Second Generation), developed around 2003, introduced advanced techniques for channel coding, modulation, and error correction, enabling new commercial services like HDTV.

Rain fade, antenna pointing errors, local noise, and interference, can all interfere and cause satellite performance to degrade. To overcome slowdowns or outages from these conditions, operators apply or reserve “link margin” or some amount of capacity that is essentially “set aside” and used as needed when conditions degrade. This works but is highly inefficient. Rather than sitting idle, ACM allows this link margin to be used to transmit data, when conditions are optimal, thus addressing both efficiency and availability.

Higher Spectral Efficiency: DVB-S2 employs more sophisticated modulation schemes such as QPSK, 8PSK, 16APSK, and 32APSK. This allows more data to be transmitted within the same bandwidth.
Low Density Parity Check (LDPC) Forward Error Correction: Improved error correction over noisy transmission channels. LDPC codes are used for error correction, offering improved performance over the previous Reed-Solomon and Viterbi codes used in DVB-S.
Variable Code Modulation (VCM): Provided variable levels of error protection by applying different combinations of modulation and FEC to various parts of a data stream.
Adaptive Coding and Modulation (ACM): Extended VCM by providing a feedback path for near real-time adjustments based on signal propagation, optimizing link margin for data performance gains during optimal conditions. This feature dynamically adjusts the modulation and coding parameters based on the reception conditions. It ensures optimal use of the available bandwidth and improves the quality of service, especially in varying weather conditions. Key improvements included: DVB-S2 provided a 30% improvement in spectral efficiency over DVB-S and was published as an ETSI standard in 2005. Such gains are achieved by informing the satellite uplink station of the channel condition (e.g. the value of carrier powerto-noise and interference power ratio, C/N þ I) of each receiving terminal via the satellite or terrestrial return channels.
Enhanced Modulation Options: Added 8-PSK, 16-APSK, and 32-APSK modulation schemes for better spectral efficiency, allowing more data transmission within the same bandwidth.
Support for MPEG-2 and MPEG-4 Streams: Included support for both MPEG-2 TS and MPEG-4, enhancing coding efficiency and providing robust transmission features.MPEG is a standard for compressing moving pictures. MPEG 2 TS is designed for streaming live events. MPEG 2 supports data rates from 1.2 Mbps to 15 Mbps. MPEG-4 provides improved coding efficiency. It can encode mixed media such as video, audio and speech. Robust transmission is provided with advanced error resilience features.Backward Compatibility: DVB-S2 is designed to be backward compatible with DVB-S, allowing seamless transition and interoperability between the two standards.

In the case of interactive and point-to-point applications, the VCM functionality is combined with the use of return channels to achieve adaptive coding and modulation (ACM). This technique provides dynamic link adaptation to propagation conditions, targeting each individual receiving terminal. ACMsystems promise satellite capacity gains of more than 30%. Such gains are achieved by informing the satellite uplink station of the channel condition (e.g. the value of carrier powerto- noise and interference power ratio, C/N þ I) of each receiving terminal via the satellite or terrestrial return channels. It became the preferred choice for vendors, enhancing efficiency and supporting high-definition services.

Key Features of DVB-S2

High Definition Television (HDTV): DVB-S2 supports the efficient transmission of HDTV content. The increased spectral efficiency and advanced error correction techniques ensure that HDTV signals are delivered with high quality and reliability.
Broadband Satellite Services: DVB-S2 is not just limited to video broadcasting; it also supports broadband internet services. Its robust modulation and coding schemes make it suitable for two-way satellite broadband services, providing internet connectivity in remote areas.
Scalability: The flexibility in modulation and coding allows DVB-S2 to scale efficiently, catering to various applications from standard definition to ultra-high definition television (UHDTV).

DVB-S2X: Further Enhancements

DVB-S2X, introduced in 2014, extended DVB-S2 with additional technologies and features, improving performance for core applications like Direct to Home (DTH), contribution, VSAT, and Digital Satellite News Gathering (DSNG). The specification also provides an extended operational range to cover emerging markets such as mobile applications. DVB-S2X is focused on emerging markets such as 5G.

Key features included:

Greater Modulation and Coding Granularity: Supported more precise network tuning.
Enhanced Modulation Schemes: DVB-S2X introduces higher-order modulation schemes such as 64APSK and 256APSK. These enable even higher data rates and improved spectral efficiency.
Smaller Filter Roll-Off Options: DVB-S2X supports roll-off factors as low as 5%, compared to 20%, 25%, and 35% in DVB-S2. This results in more efficient use of satellite transponder bandwidth. Options of 5%, 10%, 20%, and 35% allowed more efficient spectrum usage.
Channel Bonding: This allows multiple transponders to be bonded together, creating a larger aggregate channel. It is particularly beneficial for UHDTV and other high-bandwidth applications. Enabled bonding of up to 3 channels, delivering high aggregate data rates.
Improved ACM: Enhancements in adaptive coding and modulation provide more granular adjustments, further optimizing bandwidth usage and improving service quality.
Beam Hopping: DVB-S2X supports beam hopping, which allows satellite beams to be dynamically allocated to different regions based on demand. This increases the overall efficiency and flexibility of satellite networks.
Super Frame Option: – Super Frame option is a development intended to help address beam hopping, as in a maritime vessel or airplane passing from satellite beam to satellite beam. It also supports switching in multi-spot-beam satellites, such as most of the HTS (High Throughput Satellites) being launched today. Supported beam hopping and multi-spot-beam satellites, crucial for applications like maritime and in-flight connectivity.
Enhanced Scrambling Options: Provided better handling of co-channel interference.
Very Low SNR Operation: Supported operation with C/N ratios down to -10dB, enhancing performance in low signal environments.

DVB-S2X, published in 2015, has been rapidly implemented by satellite vendors, enabling cost-effective scaling of satellite networks and integration with terrestrial and 5G mobile services.

Broadband Satellite Network Overview

A broadband satellite network is an advanced communication system that comprises one or several gateways (or hubs) and numerous satellite terminals equipped with both receiving and transmitting capabilities. This network utilizes one or more transponders of a communication satellite, offering a variety of network topologies, including star, multi-star, mesh, or hybrid star/mesh configurations. These topologies ensure bidirectional links, making the network versatile for different types of connectivity.

The specifications of the satellite terminals and gateways can significantly vary depending on the targeted market. For the consumer market, cost-effective and highly integrated satellite terminals are crucial, with gateways being larger earth stations. Conversely, the professional market demands higher-end satellite terminals capable of aggregating traffic generated by Local Area Networks (LANs).

Key Features and Standards

Broadband satellite networks are designed to deliver services similar to terrestrial Internet networks. These networks predominantly adhere to the Digital Video Broadcasting (DVB) standards, particularly the satellite versions DVB-S and DVB-S2. Initially intended for video and audio streams, these standards have been extended to support IP datagrams. The DVB-Return Channel Satellite (DVB-RCS) standard further specifies the return traffic flows from DVB-RCS terminals to gateways.

Characteristics of DVB-S/S2/DVB-RCS Networks

A DVB-S/S2/DVB-RCS network exhibits the following key characteristics:

Uplink Utilization: The uplink from the RCS terminal (RCST) employs Multi-Frequency Time Division Multiple Access (MF-TDMA) as per the DVB-RCS standard and MPEG profile.
Downlink Compatibility: The downlink from the satellite to the RCST is fully compatible with DVB-S/S2 standards.
Traffic Support: The system supports symmetric predictive traffic and bursty traffic generated by numerous users through dynamic allocation.
Interworking with Terrestrial Networks: The satellite system integrates with terrestrial networks such as PSTN, ISDN, and private IP networks of service providers (SPs).
Service Integration: The system supports integrated IP-based data services and native MPEG video broadcasting.
Connectivity: Star connectivity networks facilitate single-hop connectivity between satellite and terrestrial network users via the gateway. Mesh connectivity networks support single-hop connectivity between satellite network users, requiring an on-board processor (OBP) for flexible routing and potential data replication for multicast services.

Components of the Broadband Satellite Network

Management Station (MS)

The MS comprises the Network Management Centre (NMC) and the Network Control Centre (NCC). The NMC oversees all network elements and service provisioning, while the NCC manages control of the interactive network, processing satellite access requests from users.

Gateway (GW)

The GW bridges satellite and terrestrial networks, such as telephony (PSTN, ISDN) and internet/intranet networks. It offers service guarantees based on different QoS criteria and subscription levels. A GW can include interactive receive decoders (IRD), IP routers, multi-conference units (MCU), and voice and video gateways or gatekeepers.

Return Channel Satellite Terminal (RCST)

The RCST, compliant with the DVB-RCS standard, consists of an indoor unit (IDU) and an outdoor unit (ODU). The IDU contains the DVB-S/S2/DVB-RCS modem and the interface to the local network, while the ODU includes the RF transmitter, RF receivers, and the antenna. The RCST supports both single-hop and double-hop communications for various network configurations.

On-Board Processor (OBP)

For networks utilizing on-board processing, the OBP is vital for satellite mesh systems. It combines DVB-RCS and DVB-S/S2 standards to enable cross-connectivity between uplink and downlink beams. The OBP demultiplexes, demodulates, and decodes uplink carriers to generate a multiplex of MPEG-2 packets compliant with DVB-S/S2 standards. This multiplexing allows efficient downlink frequency conversion and transmission.

Network Interfaces

The satellite network components communicate through various interfaces:

T Interface: Connects the RCST IDU with user terminals or LANs.
N Interface: Links the NCC and RCST for control and signaling.
M Interface: Connects the NMC and RCST for management purposes.
U Interface: Connects the satellite payload with the RCST physical interface.
P Interface: Links two RCSTs for peer layer signaling and user data traffic.
O Interface: Connects the NCC and OBP for OBP control and management.

Multibeam Satellite Systems

The DVB specification TS 101 154 outlines the use of video and audio coding in broadcast and broadband applications. Regular updates to this document accommodate new market requirements and technological advancements. The 2019 revision of DVB-S2X introduced beam hopping, enhancing the efficient use of satellite resources for applications like VoIP, cellular backhaul, IoT, maritime, and in-flight connectivity.

Industry Standards

Standards from the European Telecommunications Standards Institute (ETSI) and the Internet Engineering Task Force (IETF) define the implementation details of IP networking protocols and network architecture, expediting the development of satellite systems for broadcasting and networking services.

By adhering to these standards and integrating advanced technologies, broadband satellite networks provide robust, versatile, and high-performance communication solutions that cater to both consumer and professional markets.

Applications in Modern Satellite Communications

HDTV and UHDTV Broadcasting: DVB-S2 and DVB-S2X are crucial for delivering high-definition and ultra-high-definition television content. Their efficient use of bandwidth ensures high-quality video transmission even in bandwidth-constrained environments.
Broadband Internet Services: The advanced features of DVB-S2/S2X make them ideal for providing broadband internet access in remote and underserved areas. This is particularly important for bridging the digital divide and ensuring global connectivity.
Enterprise and Government Networks: DVB-S2/S2X are used in enterprise and government networks for secure, reliable, and high-capacity communications. They support a wide range of applications, from corporate communications to military operations.
Disaster Recovery and Emergency Communications: In disaster recovery scenarios, satellite communications are often the only reliable means of communication. DVB-S2/S2X provide the necessary robustness and flexibility to support emergency response efforts.

Conclusion

The DVB-S2 and DVB-S2X standards represent significant advancements in satellite communication technology. Their ability to deliver high-definition television and broadband internet services with improved efficiency and reliability makes them indispensable in modern broadcasting and connectivity solutions. As satellite technology continues to evolve, DVB-S2 and DVB-S2X will remain at the forefront, driving innovation and expanding the reach of digital communications worldwide.

References and Resources also include:

https://www.bcsatellite.net/blog/dvb-s2-and-dvb-s2x-what-are-they/