As the next generation digital TV (DTV) standard, the ATSC 3.0 system is developed to provide significant improvements on the spectrum efficiency, the service reliability, the system flexibility, and system forward compatibility. One of the top-priority requirements for the ATSC 3.0 is the capability to deliver reliable mobile TV services to a large variety of mobile and indoor devices. Layered-division-multiplexing (LDM) is a physical-layer non-orthogonal-multiplexing technology to efficiently deliver multiple services with different robustness and throughputs in one TV channel. A two-layer LDM structure is accepted by ATSC 3.0 as a baseline physical-layer technology. This LDM system is capable of delivering robust high-definition (HD) mobile TV and ultra-HDTV services in one 6 MHz channel, with a higher spectrum efficiency than the traditional time/frequency-division-multiplexing (T/FDM)-based DTV systems. This paper presents a detailed overview on the LDM technology, and its application in the ATSC 3.0 systems. First, the fundamental advantages of the LDM over the traditional TDM/FDM systems are analyzed from information theory point of view. The performance advantages of the LDM are then confirmed by extensive simulations of the ATSC 3.0 system. It is shown that, LDM can realize the potential gain offered by superposition coding over the TDM/FDM systems, by properly configuring the transmission power, channel coding, and modulation, and using different multiple antenna technologies in the multiple layers. Next, the efficient implementation of LDM in the ATSC 3.0 system is presented to show that the performance advantages of the LDM are obtained with small additional complexity. This is achieved by carefully aligning the transmission signal structure and the signal processing chains in the multiple layers. Finally, we show that the LDM can be further integrated with different multiple antenna technologies to achieve further transmission capacity.

Layered-Division-Multiplexing: Theory and Practice

This paper provides an overview of the physical layer specification of Advanced Television Systems Committee (ATSC) 3.0, the next-generation digital terrestrial broadcasting standard. ATSC 3.0 does not have any backwards-compatibility constraint with existing ATSC standards, and it uses orthogonal frequency division multiplexing-based waveforms along with powerful low-density parity check (LDPC) forward error correction codes similar to existing state-of-the-art. However, it introduces many new technological features such as 2-D non-uniform constellations, improved and ultra-robust LDPC codes, power-based layered division multiplexing to efficiently provide mobile and fixed services in the same radio frequency (RF) channel, as well as a novel frequency pre-distortion multiple-input single-output antenna scheme. ATSC 3.0 also allows bonding of two RF channels to increase the service peak data rate and to exploit inter-RF channel frequency diversity, and to employ dual-polarized multiple-input multiple-output antenna system. Furthermore, ATSC 3.0 provides great flexibility in terms of configuration parameters (e.g., 12 coding rates, 6 modulation orders, 16 pilot patterns, 12 guard intervals, and 2 time interleavers), and also a very flexible data multiplexing scheme using time, frequency, and power dimensions. As a consequence, ATSC 3.0 not only improves the spectral efficiency and robustness well beyond the first generation ATSC broadcast television standard, but also it is positioned to become the reference terrestrial broadcasting technology worldwide due to its unprecedented performance and flexibility. Another key aspect of ATSC 3.0 is its extensible signaling, which will allow including new technologies in the future without disrupting ATSC 3.0 services. This paper provides an overview of the physical layer technologies of ATSC 3.0, covering the ATSC A/321 standard that describes the so-called bootstrap, which is the universal entry point to an ATSC 3.0 signal, and the ATSC A/322 standard that describes the physical layer downlink signals after the bootstrap. A summary comparison between ATSC 3.0 and DVB-T2 is also provided.

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An Overview of the ATSC 3.0 Physical Layer Specification

A method and an apparatus for transmitting broadcast signals thereof are disclosed. The method for transmitting broadcast signals includes encoding DP data according to a code rate, wherein the encoding further includes LDPC encoding the DP data according to the code rate, bit interleaving the LDPC encoded DP data, mapping the bit interleaved DP data onto constellations, MIMO (Multi Input Multi Output) encoding the mapped DP data, and time interleaving the MIMO encoded DP data; building at least one signal frame by arranging the encoded DP data; and modulating data in the built signal frame by OFDM method and transmitting the broadcast signals having the modulated data, wherein the step of modulating includes inserting CPs in the built signal frame based on a CP set which includes information about locations of CPs, wherein the CP set is defined based on FFT size.

Apparatus for transmitting broadcast signals, apparatus for receiving broadcast signals, method for transmitting broadcast signals and method for receiving broadcast signals

This paper provides a review of the second generation of terrestrial digital video broadcasting standard (DVB-T2). DVB-T2 is the evolution of DVB-T and, together with DVB-S2 and DVB-C2, inaugurated a new transition from the first-generation digital broadcasting systems, similar to the transition from analog-to-digital systems. In this paper, the most relevant features of DVB-T2 are explained in detail, along with their benefits and trade-offs. This paper also presents a comprehensive review of the laboratory and field trial results available so far. Especial emphasis is placed in the results of the measurements carried out to test the mobile reception and the novel technologies as multiple input single output and time frequency slicing.

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DVB-T2: The Second Generation of Terrestrial Digital Video Broadcasting System

This paper introduces the concept of a non-uniform constellation (NUC) in contrast to conventional uniform quadrature-amplitude modulation (QAM) constellations. Such constellations provide additional shaping gain, which allows reception at lower signal-to-noise ratios. ATSC3.0 will be the first major broadcasting standard, which completely uses NUCs due to their outstanding properties. We will consider different kinds of NUCs and describe their performance: 2-D NUCs provide more shaping gain at the cost of higher demapping complexity, while 1-D NUCs allow low-complexity demapping at slightly lower shaping gains. These NUCs are well suited for very large constellations sizes, such as 1k and 4k QAM.

Non-Uniform Constellations for ATSC 3.0

Spectrally efficient transmission on the physical layer is a crucial attribute of state-of-the-art transmission systems. The latest broadcast and terrestrial point-to-point systems such as DVB-T2, DVB-C2 or LTE use LDPC- or Turbo-codes jointly with QAM constellations to achieve capacity approaching the Shannon limit. However, since the gap between the BICM capacity of conventional uniform QAM constellations and the Shannon limit increases for larger SNR, constellation shaping is required to closely approach the Shannon limit when leaving the low SNR region. We propose non-uniform QAM constellations with modulation orders until 1024k-QAM approaching the Shannon limit up to 0.036 b/s/Hz at 29 dB SNR, corresponding to a short-coming of 0.108 dB. To maintain low-complexity 1-dimensional demapping of each component, the symmetry of the constellations is kept. In addition, we propose quadrant symmetric non-uniform QAM constellations optimized in both dimensions, to improve the performance of the constellations at low SNR.

Optimization of high-order non-uniform QAM constellations

A coding and modulation apparatus and method are presented. The apparatus comprises an encoder that encodes input data into cell words, and a modulator that modulates said cell words into constellation values of a non-uniform constellation. The modulator is configured to use, based on the total number M of constellation points of the constellation and the code rate, a non-uniform constellation from one or several groups of constellations each comprising one or more constellations.

Coding and modulation apparatus using non-uniform constellation

A transmitter for transmitting payload data and emergency information using data symbols in a single-carrier or multi-carrier broadcast system comprises a modulator configured to modulate one or more transmission symbols with signaling data for use in detecting and recovering the payload data at a receiver and to modulate one or more transmission symbols with the payload data. An emergency information receiver receives emergency information carrying information of an actual emergency. An emergency information embedder embeds emergency information into one or more transmission symbols, wherein the emergency information is embedded within a predetermined time period after its reception by using a resource used for carrying signaling data and/or payload data if no emergency information shall be transmitted. A transmission unit transmits the transmission symbols.

Transmitter and transmission method for transmitting payload data and emergency information

A transmitter transmits payload data using Orthogonal Frequency Division Multiplexed (OFDM) symbols. The transmitter comprises a frame builder configured to receive the payload data to be transmitted and to receive first signalling data for use in detecting and recovering the payload data at a receiver, and to form the payload data and the first signalling data into frames for transmission, the first signalling data forming a part of the frames with the payload data. A modulator is configured to modulate a first OFDM symbol with the first signalling data and to modulate one or more second OFDM symbols with the payload data. A signature sequence processor provides a signature sequence, a combiner combines the signature sequence with the first OFDM symbol, and a transmission unit transmits the first and second OFDM symbols. The signature sequence provided by the signature sequence processor comprises at least one of a first synchronisation sequence or a second message sequence, the first synchronisation sequence and/or the second message sequence being combined by the combiner with the first OFMD symbol. The first synclironisation sequence is provided for a receiver to detect and to recover the first signalling data from the first OFDM symbol and the second message sequence provides message information to the receiver. The message information may be used to convey a specific message to a user such as an emergency warning relating to a natural disaster such as an earthquake or a tsunami warning.

Jan Zoellner

Papers

DVB-T2: The Second Generation of Terrestrial Digital Video Broadcasting System

Optimization of high-order non-uniform QAM constellations

Coding and modulation apparatus using non-uniform constellation

Transmitter and transmission method for transmitting payload data and emergency information

Transmitter and method of transmitting payload data, receiver and method of receiving payload data in an ofdm system