Two-layer Layered Division Multiplexing Research Articles

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.

Coverage Study of ATSC 3.0 Under Strong Co-Channel Interference Environments

In addition to the traditional TDM/FDM, the advanced television systems committee (ATSC) 3.0 next generation digital TV standard has adopted state-of-the-art coding and modulation, as well as the new layered division multiplexing (LDM) technology. The ATSC 3.0 system is able to provide higher data throughput, more robust reception, better spectrum efficiency, and flexible service combinations in one RF channel with different robustness and reception conditions. Due to the adoption of a two-layer LDM, the coverage for ATSC 3.0 is very different from the legacy one-transmitter-one-coverage ATSC 1.0 system. With the new enabling technologies, the ATSC 3.0 can greatly increase the coverage/service areas, reduce the distance between co-channel assignments, and introduce local program insertion and targeted advertisement. This paper addresses the ATSC 3.0 coverage and co-channel interference issues, by using the two-layer LDM technology with different operating parameters. Simulations demonstrate that, similar to the 4G long term evolution, the ATSC 3.0 co-channel assignment could be reduced to two times the service coverage radius. This means an improvement of the spectrum efficiency by up to four times in comparison with today’s system. It is also proved through simulations that significant TV program gains can be obtained with this new system. The deployment of single frequency networks can further improve the coverage and reduce the interference.

Joint Base Station Clustering and Beamforming for Non-Orthogonal Multicast and Unicast Transmission With Backhaul Constraints

The demand for providing multicast services in cellular networks is continuously and fastly increasing. In this work, we propose a non-orthogonal transmission framework based on layered-division multiplexing (LDM) to support multicast and unicast services concurrently in cooperative multi-cell cellular networks with limited backhaul capacity. We adopt a two-layer LDM structure where the first layer is intended for multicast services, the second layer is for unicast services, and the two layers are superposed with different beamformers. Each user decodes the multicast message first, subtracts it, and then decodes its dedicated unicast message. We formulate a joint multicast and unicast beamforming problem with adaptive base station clustering that aims to maximize the weighted sum of the multicast rate and the unicast rate under per-BS power and backhaul constraints. To solve the problem, we first develop a branch-and-bound algorithm to find its global optimum. We then reformulate the problem as a sparse beamforming problem and propose a low-complexity algorithm based on convex-concave procedure. Simulation results demonstrate the significant superiority of the proposed LDM-based non-orthogonal scheme over orthogonal schemes in terms of the achievable multicast-unicast rate region.

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.

Using LDM to Achieve Seamless Local Service Insertion and Local Program Coverage in SFN Environment

Layered division multiplexing (LDM) is a spectrum efficient non-orthogonal multiplexing technology that has been adopted in the Advanced Television Systems Committee (ATSC) 3.0 Physical Layer Standard as a baseline technology. This paper studies a two-layer LDM with one layer used for providing a global service through a single frequency network (SFN), and the other for providing local coverage/services, such as location targeted advertising or local content insertion. The pilot boosting effect on SNR and co-channel interference is also analyzed. The LDM upper layer can be used to deliver time-division multiplexed mobile-HD and 4k-UHD services. The LDM lower layer with a negative SNR threshold can reliably provide seamless local coverage/service from each SFN transmitter without coverage gaps among adjacent SFN transmitter service areas. No directional receiving antenna is required for the local service reception and receivers simply tune into the stronger signal. In such LDM systems, while the upper layer is operating in a traditional SFN mode, the lower layer operates in a special form of distributed MIMO or gap-filler mode to provide targeted local coverage. For implementing the two-layer system introduced in this paper, only ATSC 3.0 baseline technologies are used, i.e., there is no need to modify the ATSC 3.0 standard. Given the upper and lower layers’ data rate requirements and the SNR thresholds, the lower layer power, with respect to the upper layer (injection level), can be optimized to maximize upper and lower layer performance and coverage. Since the advertisement time of the local service is typically less than 20% of the program time, nonreal time could be used to play-back the local content at five times the transmission bit rate for better (audio/video) service quality.

Multiple Service Configurations Based on Layered Division Multiplexing

In this paper, we present multiple service configurations based on layered division multiplexing (LDM), which is adopted as a baseline technology of the Advanced Television Systems Committee 3.0 standard. Based on a two-layer LDM technology, a variety of multiple-physical layer pipe (PLP) configurations as well as physical layer framing is introduced depending on the choices of service scenario, time interleaving, and cell addressing. A performance analysis is provided when three different broadcasting services—robust audio, indoor/mobile, and high data rate services—are delivered through different PLPs when a number of broadcasting service scenarios is presented.

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.