Vittoria Mignone

DVB-S2: The Second Generation Standard for Satellite Broad-Band Services

DVB-S2 is the second-generation specification for satellite broad-band applications, developed by the Digital Video Broadcasting (DVB) Project in 2003. The system is structured as a toolkit to allow the implementation of the following satellite applications: TV and sound broadcasting, interactivity (i.e., Internet access), and professional services, such as TV contribution links and digital satellite news gathering. It has been specified around three concepts: best transmission performance approaching the Shannon limit, total flexibility, and reasonable receiver complexity. Channel coding and modulation are based on more recent developments by the scientific community: low density parity check codes are adopted, combined with QPSK, 8PSK, 16APSK, and 32APSK modulations for the system to work properly on the nonlinear satellite channel. The framing structure allows for maximum flexibility in a versatile system and also synchronization in worst case configurations (low signal-to-noise ratios). Adaptive coding and modulation, when used in one-to-one links, then allows optimization of the transmission parameters for each individual user,dependant on path conditions. Backward-compatible modes are also available,allowing existing DVB-S integrated receivers-decoders to continue working during the transitional period. The paper provides a tutorial overview of the DVB-S2 system, describing its main features and performance in various scenarios and applications.

CD3-OFDM: a novel demodulation scheme for fixed and mobile receivers

This paper describes a novel channel estimation scheme identified as coded decision directed demodulation (CD3) for coherent demodulation of orthogonal frequency division multiplex (OFDM) signals making use of any constellation format [e.g., quaternary phase shift keying (QPSK), 16-quadrature amplitude modulation (QAM), 64-QAM]. The structure of the CD3-OFDM demodulator is described, based on a new channel estimation loop exploiting the error correction capability of a forward error correction (FEC) decoder and frequency and time domain filtering to mitigate the effects of noise and residual errors. In contrast to the conventional coherent OFDM demodulation schemes, CD3-OFDM does not require the transmission of a comb of pilot tones for channel estimation and equalization, therefore yielding a significant improvement in spectrum efficiency (typically between 5-15%). The performance of the system with QPSK modulation is analyzed by computer simulations, on additive white Gaussian noise (AWGN) and frequency selective channels, under static and mobile reception conditions. For convolutional coding rate 1/2, the results indicate that CD3-OFDM allows one to achieve a very fast adaptation to the channel characteristics in a mobile environment (maximum tolerable Doppler shift of about 80 Hz for an OFDM symbol duration of 1 ms, as differential demodulation) and an E/sub b//N/sub 0/ performance similar to coherent demodulation (e.g., E/sub b//N/sub 0/=4.3 dB at bit-error rate (BER)=2/spl middot/10/sup -4/ on the AWGN channel). Therefore, CD3-OFDM can be suitable for digital sound and television broadcasting services over selective radio channels, addressed to fixed and vehicular receivers.

Key technologies for next-generation terrestrial digital television standard DVB-T2

A new platform for HDTV transmissions, in the form of a new-generation terrestrial digital video broadcasting standard (DVB-T2), has been developed by the DVB Project and will be published by the European Telecommunications Standards Institute. A number of technical innovations have been included in DVB-T2 to boost throughput and ruggedness, enhance single-frequency network coverage, and ease both transmitter and receiver implementation. This article starts from the motivations that led the DVB project to create the new standard and then surveys the key technologies behind DVB-T2, including the LDPC/BCH forward error correction scheme, transmission scheduling, orthogonal frequency-division multiplexing with huge block size, multiple-antenna transmissions, and synchronization techniques. A comparison with the current DVB-T standard is also provided, showing that DVB-T2 is able to increase the payload throughput and allows HDTV transmission with current network planning.

DVB-NGH: The Next Generation of Digital Broadcast Services to Handheld Devices

This paper reviews the main technical solutions adopted by the next-generation mobile broadcasting standard DVB-NGH, the handheld evolution of the second-generation digital terrestrial TV standard DVB-T2. The main new technical elements introduced with respect to DVB-T2 are: layered video coding with multiple physical layer pipes, time-frequency slicing, full support of an IP transport layer with a dedicated protocol stack, header compression mechanisms for both IP and MPEG-2 TS packets, new low-density parity check coding rates for the data path (down to 1/5), nonuniform constellations for 64 Quadrature Amplitude Modulation (QAM) and 256QAM, 4-D rotated constellations for Quadrature Phase Shift Keying (QPSK), improved time interleaving in terms of zapping time, end-to-end latency and memory consumption, improved physical layer signaling in terms of robustness, capacity and overhead, a novel distributed multiple input-single output transmit diversity scheme for single-frequency networks (SFNs), and efficient provisioning of local content in SFNs. All these technological solutions, together with the high performance of DVB-T2, make DVB-NGH a real next-generation mobile multimedia broadcasting technology. In fact, DVB-NGH can be regarded the first third-generation broadcasting system because it allows for the possibility of using multiple input-multiple output antenna schemes to overcome the Shannon limit of single antenna wireless communications. Furthermore, DVB-NGH also allows the deployment of an optional satellite component forming a hybrid terrestrial-satellite network topology to improve the coverage in rural areas where the installation of terrestrial networks could be uneconomical.

DVB-S2 backward-compatible modes: a bridge between the present and the future

The second generation Digital Video Broadcasting (DVB) system for satellite broadcasting (DVB-S2) has been standardized including tools to allow backward compatibility (BC) with the operating standard DVB-S (EN 300 421, Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for 11/12 GHz satellite services. V.1.1.2, August 1997, http://www.etsi.org). Two conceptual ways of implementing BC have been defined: hierarchical modulation and layered modulation. The paper describes the standardized backward-compatible modes and presents the results of analytical investigations and simulations of the system in various configurations, as carried out by DIRECTV, Rai-CRIT and Thomson. Copyright

Air interfaces for satellite based digital TV broadcasting in the railway environment

This paper deals with the analysis of possible air interfaces to be employed in order to provide digital TV services to high speed trains via satellite. This turns out to be an extremely challenging issue, since in addition to traditional impairments characterizing the land mobile satellite channel, one has to face the presence of frequent tunnels, whose duration can easily reach several kilometers, and the presence of a variety of peculiar obstacles, such as electrical trellises and posts with and without brackets, which may result in frequent and deep fades. A large variety of possible solutions, based on standardized air interfaces with proper modifications, are analyzed by means of extensive software simulations, showing that effective solutions can be devised. Some consideration concerning the deployment of terrestrial gap-fillers to bridge the satellite connectivity inside long railway tunnels, large train station and within dense urban areas are also briefly addressed.

The Future of Satellite TV: The Wide Range of Applications of the DVB-S2 Standard and Perspectives

The first two generations of TV broadcasting are almost history, at least from the standardization perspective. Analog and digital satellite distributions both have addressed mass markets. The next-generation TV systems are close to primetime deployments: HDTV, 3DTV, interactive services, hybrid services, and additional innovations will dominate the next-generation TV. With the efficiency and maturity of DVB-S2, satellite distribution is a cost-efficient and well-established broadcast technology with significant potential for extensions. In this paper, the future perspectives of digital TV and HDTV broadcasting will be first explored, considering ongoing and future standardization activities that will be carried out. Particular attention to innovative solutions based on adaptive modulation and coding, source and channel coding, and error resilience techniques for satellite TV transmission is paid. In addition to broadcast TV, also the perspectives of hybrid and IPTV will be considered in a satellite scenario with their pros and cons, trying to understand if satellite IPTV will be in competition with “conventional” broadcast satellite TV services (like it already happens in terrestrial scenarios).

Coded Decision Directed Demodulation for Second Generation Digital Video Broadcasting Standard

Second generation terrestrial digital video broadcasting (DVB-T2) standard aims at providing high definition television and high rate services for the same spectrum allocation of current DVB-T standard. This goal is achieved by adopting new physical layer features that increase the spectrum efficiency. In this respect, the insertion of pilot tones in the orthogonal frequency division multiplexed (OFDM) signal, though allowing an efficient channel estimation, decreases the spectral efficiency. In this paper we evaluate performance of the coded decision directed demodulation (CD3) technique for channel estimation in DVB-T2. In fact, by iterating between decoding and channel estimation, with the latter obtained by using previously decoded symbols, CD3 is able to provide an accurate channel estimation with very few pilots, even in the presence of highly frequency dispersive and time-variant channels. Numerical results are provided for a comparison in terms of achievable throughput between DVB-T2 with CD3 and current DVB-T. Moreover, multiple antennas at the base station are also considered to provide spatial diversity and hence further improve system performance.

Transmission parameters optimization and receiver architectures for DVB-S2X systems

Summary The second-generation specification of the digital video broadcasting for satellite (DVB-S2) was developed in 2003 with the aim of improving the existent broadcasting standard DVB-S. The main new features introduced by DVB-S2 included increased baud rates, higher cardinality constellations (up to 32 points), and more efficient binary codes. The extension to DVB-S2, approved in 2014 with the name DVB-S2X, together with continuous technological evolution, moves further steps in this direction, with the use of constellations with cardinality up to 256 points, improved granularity of modulation and coding schemes, and the possibility to increase the baud rate. In this scenario, it is important to be able to ascertain what is the best transceiver structure, starting from the choice of the shaping pulse and the baud rate of the transmitted signals and ending with the most promising receiver architectures, with the aim of maximizing the spectral efficiency. In this paper, we will discuss some of the aspects of this investigation, namely, the optimization of transmission parameters and the description of an efficient receiver. We will then assess the performance of the proposed scheme in comparison with a classical DVB-S2 architecture. Some synchronization aspects will also be discussed, to account for the impairments introduced by the channel. Copyright

Advanced techniques for spectrally efficient DVB-S2X systems

We investigate different techniques to improve the spectral efficiency of systems based on the DVB-S2 standard, when the transmitted signal bandwidth cannot be increased because it has already been optimized to the maximum value allowed by transponder filters. We will investigate and compare several techniques to involve different sections of the transceiver scheme. The techniques that will be considered include the use of advanced detection algorithms, the adoption of time packing, and the optimization of the constellation and shaping pulses. The LDPC codes recently proposed for the evolution of the DVB-S2 standard will be considered, as well as the adoption of iterative detection and decoding. Information theoretical analysis will be followed by the study of practical modulation and coding schemes.