Layered Division Multiplexing System Research Articles

Analysis on Fairness and Efficiency of the 3-PLP LDM System Using a Normalized Channel Capacity

This article presents a novel approach to investigate efficient resource allocation in the layered division multiplexing (LDM) system, a key technology in next-generation broadcasting systems. The LDM system provides diverse services, resulting in different channel capacities for each service, unlike the conventional non-orthogonal multiple access scheme that aims for equal channel capacity among users. To achieve efficient resource allocation among services, we proposed a new method that normalizes the channel capacities allocated to different services while maintaining high fairness. Our proposed method involves normalizing the channel capacities of each service and finding the point where the sum of normalized channel capacities is maximized. This point can be obtained using the Lagrange multiplier method, ensuring a high normalized fairness index. Through simulations, we confirmed that the proposed approach maintains high fairness in the LDM system and achieves the highest normalized channel capacities compared to other transmission techniques. These findings provide valuable insights into resource allocation strategies for the LDM system, enabling a fair comparison of efficiency and performance within a multi-service environment.

SFN Gain Prediction by Neural Networks for Enhancing Layer 2 Coverage in LDM Systems

LTE-eMBMS systems efficiently deliver multicast/broadcast services using Layered Division Multiplexing (LDM) technology. In a two-layer LDM system, Layer 1, with higher power allocation delivers mobile services, and Layer 2 in a Single Frequency Network scheme provides local content. The challenge is to reduce the gap in the layers' coverage areas caused by the use of different constellations, and SFN gain for Layer 2. Hence, the precision in the coverage area estimation is crucial for the successful planning and deployment, particularly regarding the SFN gain contribution in Layer 2. For this purpose, a real digital TV broadcasting SFN system was used as a model to design a method based on Machine Learning algorithms, aiming to enhance the coverage area precision for the Layer 2 in eMBMS. The method is able to estimate SFN gain value with a Mean Absolute Error (MAE) of 0.72 dB and certainty in positive or negative contribution in 93% of the cases.

Spatial Modulation Aided Layered Division Multiplexing: A Spectral Efficiency Perspective

In this paper, spatial modulation (SM) is introduced to layered division multiplexing (LDM) systems for enlarging the spectral efficiency (SE) over broadcasting transmission. First, the SM aided LDM (SM-LDM) system is proposed, in which different layered services utilize SM for terrestrial broadcasting transmission with different power levels. Then a SE analysis framework for SM-LDM systems is proposed, which is suitable for the SM-LDM systems with linear combining. Moreover, the closed-form SE lower bound of SM-LDM systems with maximum ratio combining (MRC) is derived, which is based on this framework. Since the theoretical SE analysis of single transmit antenna (TA) LDM systems with MRC and spatial multiplexing (SMX) aided LDM systems with MRC lacks a closed-form expression, the closed-form SE is also derived for these systems. Monte Carlo simulations are provided to verify the tightness of our proposed SE lower bound. Furthermore, it can be shown via simulations that our proposed SM-LDM systems always have a better SE performance than single-TA LDM systems, which can even outperform the SE of SMX aided LDM (SMX-LDM) systems.

Using Layered-Division-Multiplexing to Deliver Multi-Layer Mobile Services in ATSC 3.0

Layered-division-multiplexing (LDM) is a physical-layer non-orthogonal multiplexing technology, which has been accepted as a baseline technology by the next generation terrestrial digital TV (DTV) broadcasting standard, advanced television systems committee (ATSC) 3.0. The typical scenario for an LDM-based ATSC 3.0 system is to deliver a robust high-definition TV (HDTV) service in the higher-power core-layer (CL) for mobile reception and a 4k ultra high definition TV or multiple enhanced full HDTV (1080p) services in the lower-power enhanced layer (EL) for fixed reception. So far, the capability of using the EL of an LDM system to deliver mobile services has not been investigated and well-understood. In this paper, we investigate the potential of using both layers of an LDM-based ATSC 3.0 system to delivery multiple mobile services that target different types of mobile devices. The mobile performance of the LDM system is then compared to its time-division-multiplexing and frequency-division-multiplexing counterparts, which will reveal the application scenarios for which using LDM would provide performance advantages. In addition, the availability of high-throughput fixed services carried in the LDM-EL to mobile receivers is also investigated by computer simulations. An advanced detection algorithm is proposed based on the LDM-CL inter-carrier-interference cancellation, which is shown to provide significantly better mobile performance. Finally, we show by simulation that using receive antenna diversity combining techniques can significantly improve the service detection performance of LDM mobile receivers, especially for services carried in the LDM EL.

Efficient Transmission of Multiple Broadcasting Services Using LDM and SHVC

In this paper, we present an efficient transmission method of multiple broadcasting services using layered division multiplexing (LDM) and scalable high efficiency video coding (SHVC) based on the next generation terrestrial digital broadcasting standard, advanced television systems committee 3.0. In a two-layer LDM system, each layer forms a physical layer pipe that carries base layer and enhancement layer video streams of SHVC, respectively. This combination of physical and presentation layers technologies can maximize channel utilization when multiple broadcasting services are delivered in a single radio frequency channel with different robustness and reception conditions. An intensive performance analysis is provided when the proposed combination of LDM and SHVC is compared with other approaches, such as time division multiplexing and/or high efficiency video coding simulcast broadcasting. Several performance measurements are also introduced, such as constant data rate measurement and constant quality measurement, which are used to evaluate the performance of video codecs in conjunction with different physical layer system parameters. A prototype hardware system with LDM and SHVC capable of selecting different parameter combinations is tested in the laboratory and in real field environments to verify the performance and feasibility of the proposed LDM and SHVC combination. Results show that the proposed LDM and SHVC combination provides significant gains on video service quality as well as reception robustness.

Efficient Decoding of LDM Core Layer at Fixed Receivers in ATSC 3.0

In order to decode an enhanced layer (EL) signal for a layered-division multiplexing (LDM) system at fixed receivers in ATSC 3.0, low-density parity-check (LDPC)/BCH decoding and successive interference cancellation should be performed to eliminate the core layer (CL) signal. For a high signal-to-noise ratio environment and sufficient low injection level of the EL signal, the CL bit-interleaved coded modulation decoder can easily achieve quasi error free for the whole LDPC codeword. However, for high injection levels, there may be still many erroneous bits in the parity part even after LDPC/BCH decoding since the ATSC 3.0 LDPC codes have the characteristic of unequal error protection due to the unequal weight distributions in their parity-check matrices. Therefore, ATSC 3.0 receivers should include re-encoding module for CL LDPC codes to completely recover the CL signal for LDM system. In this paper, we propose an efficient method to reconstruct CL signal in ATSC 3.0 LDM systems, which can be realized by a modified re-encoding after LDPC decoding of the CL signal. It significantly reduces the computational complexity and worst case latency without any loss of coding performance.

Layered-Division-Multiplexing: Theory and Practice

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.

Low Complexity Layered Division Multiplexing for ATSC 3.0

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.