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

This white paper explores the road to implementing broadband connectivity in future 6G wireless systems. Different categories of use cases are considered, from extreme capacity with peak data rates up to 1 Tbps, to raising the typical data rates by orders-of-magnitude, to support broadband connectivity at railway speeds up to 1000 km/h. To achieve these goals, not only the terrestrial networks will be evolved but they will also be integrated with satellite networks, all facilitating autonomous systems and various interconnected structures. We believe that several categories of enablers at the infrastructure, spectrum, and protocol/ algorithmic levels are required to realize the intended broadband connectivity goals in 6G. At the infrastructure level, we consider ultra-massive MIMO technology (possibly implemented using holographic radio), intelligent reflecting surfaces, user-centric and scalable cell-free networking, integrated access and backhaul, and integrated space and terrestrial networks. At the spectrum level, the network must seamlessly utilize sub-6 GHz bands for coverage and spatial multiplexing of many devices, while higher bands will be used for pushing the peak rates of point-to-point links. The latter path will lead to THz communications complemented by visible light communications in specific scenarios. At the protocol/algorithmic level, the enablers include improved coding, modulation, and waveforms to achieve lower latencies, higher reliability, and reduced complexity. Different options will be needed to optimally support different use cases. The resource efficiency can be further improved by using various combinations of full-duplex radios, interference management based on rate-splitting, machine-learning-based optimization, coded caching, and broadcasting.

White Paper on Broadband Connectivity in 6G

In this paper, we propose novel transmitter and receiver architectures for low complexity layered division multiplexing (LDM) systems. The proposed transmitter architecture, which is adopted as a baseline technology of the Advanced Television Systems Committee 3.0, shares time and frequency interleavers, FFT, pilot patterns, guard interval, preamble, and bootstrap among different layers, so that the implementation of LDM receivers can be realized with less than 10% complexity increase compared to conventional single layer receivers. With such low complexity increment, we show simulation and laboratory test results that the proposed LDM system has significant performance advantage (3–9 dB) over traditional TDM systems, and maintains its performance up to the velocity of 260 km/h in mobile reception.

Low Complexity Layered Division Multiplexing for ATSC 3.0

In this paper, we summarize and expound upon the choices made for the bit-interleaved coded modulation (BICM) part of the next-generation terrestrial broadcast standard known as ATSC 3.0. The structure of the ATSC 3.0 BICM consists of a forward error correcting code, bit interleaver, and constellation mapper. In order to achieve high efficiency over a wide range of reception conditions and carrier-to-noise (C/N) ratio values, several notable new elements have been standardized. First, 24 original low-density parity check (LDPC) codes have been designed, with coding rates from 2/15 (0.13) up to 13/15 (0.87) for two code sizes: 16 200 bits and 64 800 bits. Two different LDPC structures have been adopted; one structure more suited to medium and high coding rates and another structure suited to very low coding rates. Second, in addition to quaternary phase shift keying, non-uniform constellations (NUCs) have been chosen for constellation sizes from 16QAM to 4096QAM to bridge the gap to the Shannon theoretical limit. Two different types of NUCs have been proposed: 1-D NUCs for 1024- and 4096-point constellations, and 2-D-NUCs for 16-, 64-, and 256-point constellations. 2-D-NUCs achieve a better performance than 1-D-NUCs but with a higher complexity since they cannot be separated into two independent I/Q components. NUCs have been optimized for each coding rate for the 64 800 bits LPDCs. The same constellations are used for 16 200 bits LDPCs, although they have been limited up to 256QAM. Finally, a bit interleaver, optimized for each NUC/coding rate combination, has been designed to maximize the performance. The result is a BICM that provides the largest operating range (more than 30 dB, with the most robust mode operating below -5 dB C/N) and the highest spectral efficiency compared to any digital terrestrial broadcast system today, outperforming the current state-of-the-art DVB-T2 standard BICM by as much as 1 dB in some cases. ATSC 3.0 will also provide a considerable increase in the maximum transmission capacity when using the high-order NUCs such as 1024QAM and 4096QAM, which will represent a major milestone for terrestrial broadcasting since the highest order constellation currently available is uniform 256QAM. This paper describes the coding, modulation, and bit interleaving modules of the BICM block of ATSC 3.0 and compares its performance with other DTT standards such as ATSC A/53 and DVB-T2.

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Bit-Interleaved Coded Modulation (BICM) for ATSC 3.0

This paper provides an overview of the optional multiple-input multiple-output (MIMO) antenna scheme adopted in ATSC 3.0 to improve robustness or increase capacity via additional spatial diversity and multiplexing by sending two data streams in a single radio frequency channel. Although it is not directly specified, it is expected in practice to use cross-polarized $2 {\times }2$ MIMO (i.e., horizontal and vertical polarization) to retain multiplexing capabilities in line-of-sight conditions. MIMO allows overcoming the channel capacity limit of single antenna wireless communications in a given channel bandwidth without any increase in the total transmission power. But in the U.S. MIMO can actually provide a larger comparative gain because it would be allowed to increase the total transmit power, by transmitting the nominal transmit power in each polarization. Hence, in addition to the MIMO gains (array, diversity, and spatial multiplexing), MIMO could exploit an additional 3 dB power gain. The MIMO scheme adopted in ATSC 3.0 re-uses the single-input single-output antenna baseline constellations, and hence it introduces the use of MIMO with non-uniform constellations.

MIMO for ATSC 3.0

This paper presents optimized time interleaving which has been adopted for the Advanced Television System Committee 3.0 system as a physical layer tool to mitigate the effects of burst errors. The adopted time interleaver (TI) is very flexible and can have different configurations according to the number of physical layer pipes (PLPs) and service type, i.e., fixed, portable, and mobile. Notably, for single-PLP mode a sheer convolutional TI (CTI) is used, whereas for the multiple-PLP mode a hybrid TI (HTI) composed of cell interleaver, twisted block interleaver, and a convolutional delay-line is used. Optionally, the CTI and the HTI can be used in conjunction with extended time interleaving and a cell interleaver (only for HTI) to further improve robustness over long burst error lengths at the expense of latency.

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Physical Layer Time Interleaving for the ATSC 3.0 System

A new system concept for DTT, called “WiB”, is presented, where potentially all frequencies within the Ultra High Frequency (UHF) band are used on all transmitter (TX) sites (i.e. reuse-1). Interference, especially from neighbouring transmitters operating on the same frequency and transmitting different information, is handled by a combination of a robust transmission mode, directional discrimination of the receiving antenna and interference cancellation methods. With this approach DTT may be transmitted as a single wideband signal, covering potentially the entire UHF band, from a single wideband transmitter per TX site. Thanks to a higher spectrum utilisation the approach allows for a dramatic reduction in fundamental power/cost and about 37-60% capacity increase for the same coverage as with current DTT. High speed mobile reception as well as fine granularity local services would also be supported, without loss of capacity. The paper also outlines further possible developments of WiB, e.g. doubling the capacity via cross-polar Multiple In Multiple Out (MIMO), backward-compatible with existing receiving antennas, and adding a second, WiB-mobile, Layer Division Multiplexing (LDM) layer within the same spectrum, either as mobile broadcast or as mobile broadband.

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WIB: a new system concept for digital terrestrial television (DTT)

Multi-layer broadcast systems distribute services across time and frequency domain by means of power-division multiplexing. Successive interference cancelation is required, in general, in order to extract the content of all services. For a low-complexity implementation, the receiver can obtain the strongest (top-layer) signal assuming underlying signals to behave like thermal noise. The thermal noise assumption may not be valid under certain conditions and a more accurate characterization of the interference could bring improved performance. This paper analyzes the validity of the noise-like assumption considering the power ratio between signals and the required carrier-to-noise ratio for error-free reception. The main contribution of the paper is the proposal of a demapping algorithm that exploits the knowledge of the constellation of underlying signals. Generalized mutual information, performance evaluation, and complexity analysis are provided with the additive white Gaussian noise-like assumptions and with the proposed alternative in order to assess the potential performance improvements that can be achieved.

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Information-Theoretic Analysis and Performance Evaluation of Optimal Demappers for Multi-Layer Broadcast Systems

In a transmission method according to one aspect of the present disclosure, a cyclic shift is applied to each row of an interleaver matrix in which each of a plurality of rotation components of each section is replaced with a cell, in which two rotation components are set to a real component and an imaginary component, by using (cyclic shift value k × floor(Q/max{D,(N RF × N C )}/2)) cells allocated to the row, and a value of k mod N RF varies in at least two rows of one section portion of a combined complex interleaver matrix in the cyclic shift.

Peter Klenner

Papers

MIMO for ATSC 3.0

Physical Layer Time Interleaving for the ATSC 3.0 System

WIB: a new system concept for digital terrestrial television (DTT)

Information-Theoretic Analysis and Performance Evaluation of Optimal Demappers for Multi-Layer Broadcast Systems

Transmission method, transmission device, receiving method, and receiving device