Hierarchical Modulation System Research Articles

Joint Design for Modulation and Constellation Labels in Multiuser Superposition Transmission

Hierarchical modulation (HM), a promising non-orthogonal multiple access scheme, is able to provide different levels of protection for data streams and achieve a larger rate region that cannot be realized by traditional orthogonal schemes. In this paper, we propose a novel HM system with non-uniform constellation inputs and analytically derive the bit-interleaved coded modulation (BICM)-capacity for each hierarchical layer. Different from the power optimization method for the superimposed uniform constellation, we directly optimize the constellation positions in conjunction with the optimal binary labels design for HM in additive white Gaussian noise channels. For maximizing the BICM-capacity, a fairness balanced criteria is developed for the HM system by considering both power constraints and QoS constraints. Multi-start interior-point algorithm is then proposed to carry out the constellation optimization problems, and the corresponding methods are also proposed to reduce optimization complexity. Numerical results verify the performance gains of optimized HM compared with the optimized quadrature amplitude modulation based HM and other orthogonal transmission methods.

Mathematical modelling and analysis of hierarchical modulation in AWGN and Rayleigh channel

In digital video broadcasting either multi-frequency or single frequency network is used to transmit local and global broadcasting contents respectively. Multi-frequency network consumes large spectrum to transmit local information alone. Therefore an efficient technique is required to embed both local and global content in single constellation. In this paper, hierarchical modulation or multilayered modulation is employed to satisfy this requirement in which the task is achieved by layered constellation. The base layer carries the high priority global contents and the low priority information is carried by the enhancement layer. The performance of the system is highly determined by the detection rules and the coder chosen. The performance of hierarchical modulation system is analysed by framing decision rules for both high priority and low priority streams. In addition to derivation of probability of error of the system, the analysis of bit error rate of coded and uncoded system is done. Convolutional encoder with code rate 1/3, 1/2 and 2/3 is used in this paper.

A Novel Design and Modeling of UEP-Based Compressed Video Broadcasting With Multilevel Coded Modulation

A novel coded modulation system design that maximizes the average quality of multimedia data, received by a given set of target users, is proposed for compressed video broadcasting based on unequal error protection. An integrated source and channel coding system with graceful degradation is introduced, where the multilevel coded modulation (MLC) with capacity-approaching codes is combined with an existing source compression technique. By assigning critical information that is required for decoding compressed data to the levels of MLC with higher reliability, we demonstrate that graceful degradation can be naturally incorporated into practical video broadcasting systems. Furthermore, a new measure of achievable average receiver quality, i.e., the quality of the received videos averaged over the users located within the coverage area of a given broadcasting service, is introduced. Based on the proposed measure, an optimal rate allocation algorithm for MLC, utilizing the code rate design based on channel capacity rule, is developed. In the case of MPEG-4 video coding, our numerical results reveal that a well-designed MLC system can achieve higher average quality experienced by target users than the conventional coded modulation as well as hierarchical modulation systems for a given coverage area.

Performance Analysis and System Design for Hierarchical Modulated BICM-ID

Hierarchical modulation (HM) enables unequal priority transmissions using a signal constellation of non-uniformly spaced constellation points, which is an important property for broadcast systems. Using bit interleaved coded modulation (BICM) and iterative decoding (ID), the performance of HM systems can be further improved. In this paper, we study HM system with BICM-ID or HM-BICM-ID. Since the performance of BICM-ID depends on signal mapping rules, we derive a mapping rule based on distance properties to minimize the bit error rate (BER). Furthermore, we perform the BER performance analysis for HM-BICM-ID based on binary erasure channel (BEC) modeling, which provides BER prediction without time-consuming simulations. Based on the derived BER prediction scheme, we can also perform system design and optimization for applications of HM-BICM-ID. For example, we are able to optimize the constellation priority parameter in a broadcast system to maximize the throughput.

A Framework for the Transmission of Multimedia Traffic using HM and RS Coding over Nakagami-M Channels

Hierarchical modulation (HM) provides different levels of error performance for the high and low priority bits modulated. This differentiation can be aligned to various classes of multimedia traffic demanding different levels of error rate performance. In a previous cross-layer design scheme, which combined conventional modulation at physical layer with RS coding at the application layer, an unequal error protection mechanism was used at the application layer for guaranteeing quality of service for various classes of multimedia traffic. Instead of using only a single layer, in this paper we present a more flexible two layer cross-layer design framework for unequal error protection, combining RS coding at the application layer with HM at the physical layer. Furthermore, in order to improve error performance of the system, a signal space diversity (SSD) scheme is also incorporated into the physical layer of the framework. Without consuming additional transmit power and bandwidth, the use of the SSD HM in the cross-layer design system resulted in significant gains when compared to the non-SSD, standard HM system. It is shown that the cross-layer design system with SSD HM has a 10dB gain over the non-SSD HM system in a Nakagami m=1 channel with a frame error rate target of 10−4.