Layered Division Multiplexing 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.

Multi-Objective Robust Beamforming for Integrated Satellite and Aerial Networks Supporting Heterogeneous Services

An integrated satellite and aerial network (ISAN) is considered a promising candidate to provide seamless connectivity for future wireless communication systems. In this paper, we propose a multi-objective based robust beamforming (BF) scheme for an ISAN to support heterogeneous services with high flexibility, where the satellite network serves various heterogeneous satellite terminals through multicast non-orthogonal multiple access (MC-NOMA), while the aerial network offers services to many internet of things devices using layered division multiplexing (LDM). Specifically, we first formulate a multi-objective optimization problem (MOOP) to achieve a good trade-off between sum rate maximization and total transmit power minimization. To tackle this mathematically intractable problem, we exploit the weighted Tchebycheff approach to transform the MOOP into a single-objective problem. Since only the angular information based channel state information is available, we exploit the angular discretization method and sequential convex approximation to design a robust BF algorithm to obtain the Pareto optimal solutions. Finally, simulation results demonstrated that our proposed scheme can achieve a optimal trade-off between multiple performance metrics with high spectrum and energy efficiency, so as to support heterogeneous services in the ISAN and fill the gap of only single type of serivce in the existing ISAN works.

Biased-Power Allocation and Shared-Antenna Selection Techniques for Spatial Modulation-Based Layer Division Multiplexing Systems

This study proposes two approaches for improving the effectiveness of spatial modulation integrated into layer division multiplexing (SM-LDM) in broadcasting systems: biased-power allocation (Bi-PA) and shared antenna selection (SAS). Even though different data rates are employed in SM-LDM systems, Bi-PA enhances bit error rate (BER) fairness across layers. The ideal power ratios are adaptively determined by balancing signal-to-interference plus noise ratios with a preference for the lower layer (LL) that involves a higher modulation order. SAS alleviates the complexity of successive interference cancellation and enhances spectral and energy efficiencies. Both the LL and upper layer (UL) share the antenna selection decision and transmit using a single antenna. The UL carries a space shift keying signal while the entire power is allocated for the LL. We analyze the spectral efficiency for the SAS-based SM-LDM system with finite alphabet inputs. Numerical results demonstrate the advantages of the proposed approaches. Compared to pre-assigned-PA (Pre-PA), Bi-PA shows nearly identical BERs for both layers and solves the error floor problem. The sharing property and common layer transmission of SAS-based SM-LDM yield a significant BER reduction relative to conventional SM-LDM. It provides gains ranging from 7 to 15 dB for LL at BER equal to 10−3, while UL performance ranges from slight gain to minor loss. Furthermore, both Bi-PA and SAS techniques enhance the achievable LL rate and sum-rate at low and intermediate signal-to-noise ratio values. They can achieve an improvement of up to two bits in LL rate and less than one bit in sum-rate at a signal-to-noise ratio of −0.5 dB. These findings show that both proposed techniques have a considerable impact on enhancing the fairness, BER performance, and feasible rates of SM-LDM systems, making them promise for broadcast system designs.

Inter-Tower Communications Network Signal Structure, and Interference Analysis for Terrestrial Broadcasting and Datacasting

This paper presents the Inter-Tower Communications Network (ITCN) signal structure using different combinations of multiplexing schemes, namely time-division multiplexing (TDM)/frequency-division multiplexing (FDM) and layer-division multiplexing (LDM). Data capacity is analyzed for mobile and fixed broadcasting services, as well as datacasting, inter-tower communication data, and SFN In-band Distribution Links (IDL). Multiple-input multiple-output (MIMO) is investigated for ITCN and IDL to increase the data throughput and to improve spectrum efficiency. The proposed technology can be Digital television (DTV) standard agnostic. It can be implemented on all existing DTV standards while keeping backward compatibility with legacy broadcast services and legacy TV receivers. A hybrid broadcast SFN overlay with ITCN/IDL data network using LDM might be the best solution considering backward compatibility, data capacity, and co-channel interference.

Implementation of Wireless Backhaul and Inter-Tower Communications With MIMO in ATSC 3.0

Wireless backhaul, i.e., in-band distribution links (IDL) and inter-tower communications networks (ITCN) were previously proposed as key enabling technologies for the next-generation digital broadcasting systems, e.g., the Advanced Television Systems Committee (ATSC) 3.0 system. Both ITCN/IDL can be operated in the spectrum-efficient in-band full-duplex (IBFD) mode and the same frequency band is shared between the broadcast service signal and the ITCN/IDL signals. It is desirable to integrate multi-input multi-output (MIMO) into ITCN/IDL transmission to increase the throughput and reduce the portion of spectrum occupation by ITCN/IDL. However, due to the backward compatibility constraint, conventional symmetrical MIMO techniques cannot be applied directly to the existing broadcast infrastructure without affecting legacy receivers. In this paper, the practical implementation of a non-symmetrical MIMO for ITCN/IDL while maintaining backward compatibility is considered. In addition to the existing broadcasting antenna, the non-symmetrical MIMO comprises an additional low-power RF feeder cable and one or more highly directional antennas to achieve low-cost MIMO implementation for high throughput data distribution and inter-tower communications. When the broadcast service signal and the MIMO signal are multiplexed in Time Division Multiplexing (TDM) format, the signal structure is ATSC 3.0 standard compliant. When the broadcast service signal and the MIMO signal are multiplexed in Layer Division Multiplexing (LDM) format, modification of the ATSC 3.0 standard, i.e., introducing a new pilot encoding scheme, is required. Moreover, MIMO self-interference cancellation (SIC) is investigated for IBFD operation.

In-Band Full-Duplex Communications in ATSC 3.0 Single Frequency Network

Wireless in-band backhaul, a.k.a. in-band distribution links (IDL), is a spectrum-efficient and cost-effective enabling technology to the realization of Advanced Television Systems Committee (ATSC) 3.0 in the single frequency network (SFN) mode, where all the transmitter towers are synchronized to transmit the same broadcast signal in the same frequency band. Inter-tower communications network (ITCN) transforms the broadcast towers into a mesh network, thereby introducing datacasting capability to the traditional broadcast network. Both the ITCN and IDL can be operated in the most spectrum-efficient in-band full-duplex (IBFD) mode. In these situations, the ITCN/IDL receivers at the SFN towers receive the signal of interest (SOI) not only severely corrupted by the self-interference signal from its co-located transmitter, but also the co-channel interference signals from neighbouring transmitters. Moreover, the ITCN/IDL signals may be combined with the broadcast signal in the Layer Division Multiplexing (LDM) format to achieve better overall spectral efficiency. Therefore, the LDM inter-layer interference must also be mitigated. In this paper, the interferences for the ITCN/IDL signal in the SFN environment are analyzed, and a novel iterative successive signal cancellation scheme is proposed to effectively mitigate the interferences in the ITCN/IDL signal detection process in ATSC 3.0 SFNs.

Time Synchronization and Signal Detection in Non-Orthogonal Unicast and Broadcast Networks

The next generation digital TV (DTV) broadcast, namely Advanced Television System Committee (ATSC) 3.0, relies on substantial single frequency networks (SFN), each of which requires a studio to transmitter link (STL) to transmit data from the broadcast gateway (BG), leading to significant construction costs. Therefore, the wireless in-band distribution link (IDL) technology is proposed, which uses layered-division multiplexing (LDM) to transmit the STL data via wireless links from the BG to the SFN transmitters within the same spectrum as the broadcast services. In this paper, we propose the time synchronization and signal detection algorithm for wireless IDL systems with both unicast and broadcast signals. We introduce two multiplexing schemes, N-LDM and 3-LDM, and demonstrate their superiority over traditional frequency division multiplexing (FDM). To overcome the challenge of multi-access interference and synchronization errors caused by multipath, we develop a unique word (UW) design algorithm for transmitted signals and a double threshold correlation detection algorithm (DTCDA) that outperforms traditional ones. We employ a second threshold to enhance detection performance at low signal-to-noise ratios, and utilizes successive interference cancellation (SIC) to mitigate multiple-access interference. More importantly, our approach requires no knowledge of the unicast user number or channel state information. Simulation results validate the effectiveness of the proposed scheme.

RIS-Aided LDM System: A New Prototype in Broadcasting System

Layer-division multiplexing (LDM) system has developed with significant improvement in spectrum efficiency and service diversity. LDM technology, that superposes multiple signals with different transmit powers, has been adopted by ATSC 3.0 to deliver robust high-definition services. However, due to the high mobility of devices, the wide signal coverage, and the uneven geographical channel condition, there exists under-utilized energy and significant potential of enhancing communication capacity in the LDM system. In this paper, we employ reconfigurable intelligent surface (RIS) to improve the reception quality in the LDM system, especially the SINR performance of the terminals in the edge area. We formulate a problem of maximizing the minimum SINR among all the terminals by jointly optimizing the power control and pairing mechanism, which is a Mixed-integer Nonlinear Programming (MINLP) problem. To solve it, we use the convex-concave procedure (CCCP). We further explore the high-mobility scenario with the limited channel state information (CSI) and the missing knowledge of detailed prediction of terminals’ mobility. We use Brownian Motion to model the possible variation of the terminals’ positions in the high mobility scenario to guarantee the successful reception probability. The analysis shows the RIS can bring obvious SINR gain to the LDM system, and the mobility modification could greatly help improve the successful reception probability.

Performance Analysis and Power Allocation for Spatial Modulation-Aided MIMO-LDM With Finite Alphabet Inputs

In this paper, we study a spatial modulation (SM) aided multiple-input multiple-output (MIMO) layered division multiplexing (LDM) system for broadcast/multicast service delivery in future broadcast/multicast systems. Comprehensive performance analysis and the injection level (IL) optimization are investigated for the SM-aided MIMO-LDM system over correlated Rayleigh fading channels. First, the symbol detection pairwise error probability (PEP) and the average symbol error rate (SER) union bound under joint maximum-likelihood (ML) detection are derived. Second, the spectral efficiency (SE) of the SM-aided MIMO-LDM system with finite alphabet inputs is analyzed. Since the theoretical SE lacks closed-form expression and involves prohibitive computational complexity, we then derive the closed-form lower bounds and tight approximations for the theoretical SE, in which the computational complexity is relieved by several orders of magnitude compared to direct calculation of the theoretical SE. Third, based on the SE analysis, a weighted sum (WS) SE maximization problem with quality of service (QoS) constraints is formulated to optimize IL for the SM-aided MIMO-LDM system. We first demonstrate that WS SE is a unimodal function of IL, and then develop an efficient golden section search (GSS) based algorithm. Simulation results are provided to validate the theoretical analysis. It is shown that our derived SER union bound well matches the simulated SER in the high SNR region. The tightness of the derived closed-form lower bounds and approximations for theoretical SE and the effectiveness of the developed IL optimization algorithm are also verified by simulation results.

Learning to Broadcast for Ultra-Reliable Communication With Differential Quality of Service via the Conditional Value at Risk

Broadcast/multicast communication systems are typically designed to optimize the outage rate criterion, which neglects the performance of the fraction of clients with the worst channel conditions. Targeting ultra-reliable communication scenarios, this paper takes a complementary approach by introducing the conditional value-at-risk (CVaR) rate as the expected rate of a worst-case fraction of clients. To support differential quality-of-service (QoS) levels in this class of clients, layered division multiplexing (LDM) is applied, which enables decoding at different rates. Focusing on a practical scenario in which the transmitter does not know the fading distribution, layer allocation is optimized based on a dataset sampled offline. The optimality gap caused by the availability of limited data is bounded via a generalization analysis, and the sample complexity is shown to increase as the designated fraction of worst-case clients decreases. Considering this theoretical result, meta-learning is introduced as a means to reduce sample complexity by leveraging data from previous deployments. Numerical experiments demonstrate that LDM improves spectral efficiency even for small datasets; that, for sufficiently large datasets, the proposed mirror-descent-based layer optimization scheme achieves a CVaR rate close to that achieved when the transmitter knows the fading distribution; and that meta-learning can significantly reduce data requirements.

Experimental Assessment of New Generation Radio Networks Based on Layered Division Multiplexing

Despite the recent advances in broadband penetration and accessibility, broadcasting networks continue to be the most efficient way for delivering media content to large areas independently of the user density. Nevertheless, a convergence of broadcasting services into the broadband networks is foreseen. In this context, Layered Division Multiplexing (LDM) allows the joint provision of unicast, multicast, and broadcast services in mobile cells infrastructure. Despite the success of LDM in broadcasting infrastructure, its practical application in Long Term Evolution networks providing Evolved Multimedia Broadcast Multicast Services (LTE eMBMS) and 5G-MBMS is more difficult. In this paper, we experimentally quantify the cell-interference and its impact on the network performance and Quality of Service. Our experiments reveal that the inter-cell interference margin for LTE eMBMS is about 3 dB higher compared to traditional LTE networks. If a layered architecture is incorporated this higher inter-cell interference would cause a reduction of approximately 19% of the Enhanced Layer (Lower Layer) coverage.

Performance Analysis and Optimization of LDM-Based Layered Multicast

The explosion of mobile communication devices and diversification of emerging media content put forward higher requirements for mobile communication networks in various aspects such as overall throughput, fairness and user experience. Fortunately, non-orthogonal multiplexing (NOM) techniques such as layered-division-multiplexing (LDM) and the flexible compatibility of physical layer design in fifth generation mobile networks (5G) open up the possibility to tackle the challenges. In this paper, we propose to use LDM-based layered multicast to improve network performance, where the multicast content is delivered with differentiated quality in different LDM signal layers. For various performance optimization purposes such as maximum throughput, proportional fairness, minimum dissatisfaction index, and maximum service satisfaction index, a unified analysis framework is developed. Under this framework, we formulate a joint optimization problem of layer-user pairing and power allocation. In order to solve this problem, an optimization algorithm based on subproblem decomposition is proposed, which arranges each multicast subscriber of the multicast content to receive the most suitable LDM layer, and finds the optimal transmit power and data rate for each layer. Simulation results demonstrate the superiority of LDM-based layered multicast over existing multicast approaches while guaranteeing the coverage and the lower limit of user experience.

Field Evaluation of Transmit Diversity Code Filter Sets in ATSC 3.0 Single Frequency Networks

Advanced Television Systems Committee (ATSC) 3.0, a recently developed terrestrial broadcasting standard, supports a Single Frequency Network (SFN), which extends service coverage and enhances received field strength without additional frequency resources. In SFN, multiple transmitters emit identical ATSC 3.0 broadcasting signals, which may cause constructive or destructive interference on a receiver side. The worst situation occurs when two signals from different transmitters are received with the opposite phase and similar power within a sample time, causing the cancellation of the received signal. In order to prevent such signal cancellation, ATSC 3.0 adopted transmitter diversity code filter sets (TDCFS), which is a frequency domain pre-distortion scheme to minimize cross-correlation among multiple transmitter signals in SFN. This paper sets up an ATSC 3.0 SFN consisting of two transmitter sites, transmitting high definition (HD) for mobile service and 4K ultra high definition (UHD) for fixed service. Layered division multiplexing (LDM) and time division multiplexing (TDM) are used to simulcast the two services with different robustness in the same radio frequency (RF) channel. Then, performance is evaluated using a threshold of visibility (ToV) and a successful reception rate. The time and frequency channel responses are changed at the same reception area when TDCFS is applied so the results show that reception performance is improved in the worst situation in SFN.

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.

An improving performance cellular DTV broadcasting with hybrid non-orthogonal LDM and orthogonal eMBMS configuration

In this article, we focus on the hybrid of orthogonal and non-orthogonal broadcasting. The hybrid configuration is raised and proposed for improving cellular digital television broadcasting (CDTB) technology. The hybrid scheme is configured as layered division multiplexing (LDM) multiplexed with an evolved multimedia broadcast multicast service (eMBMS) standalone layer is superimposed. The LDM and eMBMS are sub-sections of power division-non orthogonal multiple access (PD-NOMA) and long-term evolution (LTE) respectively. We assume perfect knowledge of the channel state information (CSI) over the Rayleigh fading multipath channel. The bit error rate (BER) and outage probability performance criteria are investigated. The impact of injection level using the fractional transmit power allocation (FTPA) algorithm is discussed. The proposed hybrid can operate in conditions without a subscriber identity module (SIM) card for uplink beamforming and internet protocol (IP). The broadcast network provider selection is feasible by the user equipment (UE) device. Performance analysis is derived based on the exact closed-form expressions, which allows the theory of hybrid proposed LDM/eMBMS consistent with results. Evaluations and performance will be done based on the Monte Carlo iterative methodology. The results show that the performance and efficiency will be increased when a proposed hybrid LDM/eMBMS configuration is compared with LDM and eMBMS services individually.

A Novel Coordinated Multipoint Scheme With Zero Guard Interval for ATSC 3.0 Single Frequency Networks

Advanced Television Systems Committee (ATSC) has issued ATSC 3.0 as the standard for the next-generation of Digital Terrestrial Television (DTT) broadcasting. ATSC 3.0 introduces several new features including Layered Division Multiplexing (LDM) that is a form of Non-Orthogonal Multiple Access (NOMA). ATSC 3.0 supports the legacy Single Frequency Networks (SFN), where the Guard Interval (GI) is considered to overcome the multipath as well as the asynchronous reception from different transmitters. Considering the huge distances between the DTT broadcasters, the GI overhead could be comparable to the data size, making the control/data ratio unfavorable. This paper proposes the association of Coordinated MultiPoint (CoMP) in SFN with NOMA-LDM. A novel formation of the channel matrix is provided that jointly includes the asynchronous channel's cross correlations for further joint detection of the signals at the receiver. The purpose is to enhance the coverage and spectral efficiency while avoiding hectic guard intervals or directional antennas. The capacity region is derived in an information theoretic framework based on exploiting the asynchronous channels' memory and correlation. We show that the spectral efficiency can exceed that of the non-coordinating schemes, provided that the proper receiver is equipped with the proposed channel matrix formation. Our extensive simulations validate that our proposed association of CoMP-SFN with NOMA-LDM provides a considerable boost in the coverage and channel reliability, while increasing the spectral and power efficiency.

Multi‐antenna diversity gain in terrestrial broadcasting receivers on vehicles: A coverage probability perspective

This paper theoretically and empirically explores the reliability gain that can be obtained by installing multiple antennas in on-vehicle broadcasting receivers. Analytical derivations reveal that maximal-ratio-combining-based diversity allows a multi-antenna receiver (MR) to achieve significantly better coverage probability than a single-antenna receiver (SR). In particular, the notable MR gains for low-power reception and high-throughput services are highlighted. We also discuss various aspects of mobile MRs, including geometric coverage, volume of the users served, and impact of receiver velocity. To examine the feasibility of MRs in the real world, extensive field experiments were conducted, particularly with on-air ATSC 3.0 broadcast transmissions. Relying on the celebrated erroneous second ratio criterion, MRs with two and four antennas were verified to achieve notable reliability gains over SRs in practice. Furthermore, our results also prove that layered-division multiplexing can cope better with receiver mobility than traditional time-division multiplexing when multiple services are intended in the same radio frequency channel.

Layered-Division Multiplexing in 5G New -Radio for Terrestrial Broadcast Services

The 5G system can deliver simultaneouslyunicast services, multicast services and broadcast services using the conventional high-power high- tower (HPHT) infrastructure and with the same spectrum.The Third Generation Partnership Project (3GPP) LTEevolved -multimedia broadcast- multicast service (eMBMS) have new features designed for Terrestrial Broadcast services in Release 14. A broadcast service means only receive mode, only downlink no uplink or inserting a SIM card not needed. In free to air reception without a SIM card or without user device registration with the network the content can be received. This specification is standardized in release 15. In this study a two layer Layered-Division Multiplexing (LDM) is used in 5G new radio (NR).A significant performance could be analyzed in a 5G- NRMBMS by using two layer LDM system for delivering terrestrial broadcast services. The performance analysis demonstrated by computer simulations. Using two-layer LDM in 5G-NRMBMS system a high-qualityservice can be provided to both handheld and fixed devices

Enhanced LDM for Next-Generation Digital Broadcasting Transmission

In the traditional layered division multiplexing (LDM) system, by simply adjusting the injection level, the reception performance of the core layer (CL) mobile services will be decreased significantly, resulting in the deterioration of system coverage performance. Thus, it is necessary to improve the performance of the enhanced layer (EL) service reception without affecting the reception threshold of CL service. To achieve this, in this paper, an enhanced LDM (En-LDM) scheme that supports multi-service transmission is proposed for the next-generation broadcasting network. In this scheme, at the transmitter end, part of the low-density parity-check (LDPC) coded data stream of fixed service conveyed in the EL will be extracted out through puncturing, and then, it will be transmitted over the CL of the LDM signal along with the original CL data in a frequency domain multiplexing (FDM) manner. At the receiving end, the punctured data of the EL fixed service will be recovered with a higher signal-to-noise ratio (SNR). Compared to the traditional LDM scheme, the proposed En-LDM scheme can significantly improve the reception performance of fixed services without decreasing the SNR threshold of mobile services. Moreover, the En-LDM can achieve a higher channel capacity than that of the traditional LDM for both the fixed services and the overall services. The superiority of the proposed En-LDM scheme over the traditional LDM scheme is validated by the simulation under the additive white Gaussian noise (AWGN) and fading channels.

Capacity Analysis and Improvement of LDM-Based Multiple-PLP Configurations in ATSC 3.0

This article analyzes the capacities of various layered-division multiplexing (LDM)-based multiple physical layer pipe (M-PLP) configurations in Advanced Television Systems Committee (ATSC) 3.0. Further, this article proposes an extended multi-layer LDM that consists of a core layer and one or more enhanced layer(s) combined with different injection levels. The proposed multi-layer LDM can be combined with time-division multiplexing (TDM) and/or frequency division multiplexing (FDM) to multiplex more than two PLPs. This article provides the structures of a transmitter and receiver for the multi-layer LDM and various M-PLP configurations based on the proposed multi-layer LDM. In addition, by extending to a multi-layer LDM, the low rate low-density parity-check (LDPC) codes are proposed to improve the transmission efficiency of an extremely robust service with lower data rate, such as robust audio, in the core layer of the multi-layer LDM. Simulation results show that the M-PLP configurations based on more than two layers can obtain the improved reception performance compared to the M-PLP configurations based on only two layers supported by the PHY standard in ATSC 3.0. However, since the performance degradation of layered time-division multiplexing (LTDM) with fewer layers is not significant compared to multi-layer LDM, LTDM can be a good solution to efficiently transmit M-PLPs.