Hierarchical QAM Research Articles

QAMA: Hierarchical QAM Based Downlink Multiple Access With a Simple Receiver

QAMA: Hierarchical QAM Based Downlink Multiple Access With a Simple Receiver

Hierarchical QAM and Inter-Layer FEC for Multi-View Video Plus Depth Format in Two-Way Relay Channels

Hierarchical QAM and Inter-Layer FEC for Multi-View Video Plus Depth Format in Two-Way Relay Channels

Broadcasting Scalable Video With Generalized Spatial Modulation in Cellular Networks

This paper considers the transmission of scalable video via broadcast and multicast to increase spectral and energy efficiency in cellular networks. To address this problem, we study the use of generalized spatial modulation (GSM) combined with non-orthogonal hierarchical M-QAM modulations due to the capability to exploit the potential gains of large scale antenna systems and achieve high spectral and energy efficiencies. We introduce the basic idea of broadcasting/multicasting scalable video associated to GSM, and discuss the key limitations. Non-uniform hierarchical QAM constellations are used for broadcasting/multicasting scalable video while user specific messages are carried implicitly on the indexes of the active transmit antennas combinations. To deal with multiple video and dedicated user streams multiplexed on the same transmission, an iterative receiver with reduced complexity is described. 5G New Radio (NR) based link and system level results are presented. Two different ways of quadruplicating the number of broadcasting programs are evaluated and compared. Performance results show that the proposed GSM scheme is capable of achieving flexibility and energy efficiency gain over conventional multiple input multiple output (MIMO) schemes.

Adaptive hierarchical coding and modulation scheme over satellite channels

In this study, a new scheme called adaptive hierarchical coding and modulation has been proposed, based on Adaptive Coding and Modulation (ACM) and hierarchical modulation (HM). The primary contribution of this study is summarised as the following aspects. Firstly, 16- to 64-APSK constellations with size and labelling optimisation method are proposed for HM, which can be adapted to transmitting multiple hierarchies with different QoS streams and to the non-linear satellite channels due to a lower peak-to-average power ratio compared to traditional hierarchical QAM modulation. Bit channel capacity and Chernoff error bound are introduced to optimise size and labelling of the constellation with interior-point algorithm and modified binary switch algorithm for a specific channel model to get a better performance. Secondly, combining with optimised constellations, coding and modulation modes set is obtained from using constellation design and optimisation method, with different modulation orders and code rates. And over satellite channels with rain and location attenuation, the proposed scheme is able to adapt itself to a changing channel condition and increase the transmission rate compared with ACM schemes of DVB-S2 and DVB-S2X standard.

Combined Inter-layer FEC and Hierarchical QAM for Stereoscopic 3D Video Transmission

We consider an inter-layer FEC (IL-FEC) technique combined with hierarchical QAM for an efficient and reliable transmission of stereoscopic 3D video. The transmit sources are left and right video streams, and one of them is considered a more important stream for guarantee of conventional 2D service. The source node transmits both left and right videos to a destination node by using the IL-FEC and hierarchical 16QAM schemes, in which video peak signal-to-noise ratio (PSNR) performance varies with the hierarchical value $$(\alpha )$$. In this paper, we present the suitable hierarchical values to achieve the target PSNR performances even in low SNR environment. Numerical simulation results show that the proposed system using IL-FEC and hierarchial 16QAM schemes with the suitable $$\alpha$$ value can gain about 7.3–9.3 dB in the average PSNR performance, compared with the system using IL-FEC and conventional 16QAM schemes.

Optimized unequal error protection of embedded video bitstream using adaptive-hierarchical QAM

In this paper, a reliable video communication system using adaptive Hierarchical QAM (HQAM) is designed to provide optimized unequal error protection (UEP) to embedded video bitstreams. Based on the relative importance of bits, video bitstream is partitioned into two priorities, namely High Priority (HP) and Low Priority (LP) substreams. Then, the optimal value of modulation (or hierarchical) parameter (ź) of HQAM, which controls the relative error protection of these substreams, is selected from a pre-designed look-up table. The proposed system adapts itself by adapting the optimal ź according to the varying channel condition, without changing the modulation level. This is in contrast to conventional WiMAX and LTE systems, in which dynamic switching among multiple modulations is used to adapt the varying channel conditions. This paper proposes HQAM with adaptive ź as an alternative to the multiple modulation schemes. Moreover, for fixed average transmission power, receiver demodulates symbols without the knowledge of ź. In order to further improve the video quality and to reduce the effects of erroneously received LP bits, the proposed system uses another level of adaptation, in which received LP bits are adaptively considered or discarded, before decoding the video, depending on the channel conditions (or optimized ź). Simulation results show that proposed system can achieve significant improvement in the video quality compared to QAM based EEP scheme and non-adaptive HQAM.

Priority-based Unequal Error Protection Scheme of Data partitioned H.264 video with Hierarchical QAM

In this paper, we propose a priority-based unequal error protection scheme of data partitioned H.264/AVC video with hierarchical quadrature amplitude modulation. In order to map data with higher priority onto the most significant bits of QAM constellation points, a priority sorting method categorizes different data partitions according to the unequal importance factor of encoded video data in one group of pictures by evaluated the average distortion. Then we propose a hierarchical quadrature amplitude modulation arrangement with adaptive constellation distances, which takes into account the unequal importance of encoded video data and the channel status. Simulation results show that the proposed scheme improves the received video quality by about 2 dB in PSNR comparing with the state-of-the-art unequal error protection scheme, and outperforms EEP scheme by up to 5 dB when the average channel SNR is low.

Double-layer video transmission over decode-and-forward wireless relay networks using hierarchical modulation.

We consider a wireless relay network with a single source, a single destination, and a multiple relay. The relays are half-duplex and use the decode-and-forward protocol. The transmit source is a layered video bitstream, which can be partitioned into two layers, a base layer (BL) and an enhancement layer (EL), where the BL is more important than the EL in terms of the source distortion. The source broadcasts both layers to the relays and the destination using hierarchical 16-QAM. Each relay detects and transmits successfully decoded layers to the destination using either hierarchical 16-QAM or QPSK. The destination can thus receive multiple signals, each of which can include either only the BL or both the BL and the EL. We derive the optimal linear combining method at the destination, where the uncoded bit error rate is minimized. We also present a suboptimal combining method with a closed-form solution, which performs very close to the optimal. We use the proposed double-layer transmission scheme with our combining methods for transmitting layered video bitstreams. Numerical results show that the double-layer scheme can gain 2-2.5 dB in channel signal-to-noise ratio or 5-7 dB in video peak signal-to-noise ratio, compared with the classical single-layer scheme using conventional modulation.

Layered Offset Hierarchical QAM Modulation for Intersymbol Interference Reduction

Layered offset hierarchical QAM modulation scheme is proposed to enhance the high priority stream error performance by reducing the intersymbol interference from the superimposed symbols of the low priority stream. The proposed scheme shifts the symbols of the two priority layers by half the symbol duration, whereas the detector performs multi-stage maximum-likelihood detection with interference cancellation. The simulations demonstrate the performance and design options offered by the proposed scheme compared to conventional hierarchical schemes where no time offset exists between the superimposed symbols.

A novel 3D constellation-masked method for physical security in hierarchical OFDMA system

This paper proposes a novel 3D constellation-masked method to ensure the physical security in hierarchical optical orthogonal frequency division multiplexing access (OFDMA) system. The 3D constellation masking is executed on the two levels of hierarchical modulation and among different OFDM subcarriers, which is realized by the masking vectors. The Lorenz chaotic model is adopted for the generation of masking vectors in the proposed scheme. A 9.85 Gb/s encrypted hierarchical QAM OFDM signal is successfully demonstrated in the experiment. The performance of illegal optical network unit (ONU) with different masking vectors is also investigated. The proposed method is demonstrated to be secure and efficient against the commonly known attacks in the experiment.

A Cross-Layer Unequal Error Protection Scheme for Prioritized H.264 Video using RCPC Codes and Hierarchical QAM

We investigate the rate-compatible punctured convolutional (RCPC) codes concatenated with hierarchical QAM for designing a cross-layer unequal error protection scheme for H.264 coded sequences. We first divide the H.264 encoded video slices into three priority classes based on their relative importance. We investigate the system constraints and propose an optimization formulation to compute the optimal parameters of the proposed system for the given source significance information. An upper bound to the significance-weighted bit error rate in the proposed system is derived as a function of system parameters, including the code rate and geometry of the constellation. An example is given with design rules for H.264 video communications and 3.5-4 dB PSNR improvement over existing RCPC based techniques for AWGN wireless channels is shown through simulations.

계층 16QAM의 SNR 추정 성능에 대한 연구

서로 다른 품질을 요구하는 데이터들의 동시 전송 또는 효율적인 영상전송시스템에 응용될 수 있는 계층 16QAM (Quadrature Amplitude Modulation) 시스템에 대한 SNR 추정성능에 대해 분석한다. 계층 16QAM은 계층 변조파라미터를 제어하여 성좌점들의 형태를 변형시켜 사용자에게 고품질과 저품질 데이터서비스를 동시에 제공할 수 있는 변조 시스템이다. AWGN (Additive White Gaussian Noise) 채널환경에서 계층 16QAM 시스템에서 계층변조파라미터와 성좌점별 특성을 고려한 SNR (Signal to Noise power Ratio) 추정성능 특성을 분석하였다. 시뮬레이션 결과, 계층 16QAM의 여러성좌점들 중에 SNR 추정이 상대적으로 정확하게 이루어지는 성좌점이 존재함을 확인하였고, 계층변조파라미터 값에 따라 SNR 추정이 유리한 영역이 달라진다는 것을 알아내었다. The SNR estimation performance of hierarchical 16QAM system, which is adopted to simultaneous transmission or efficient image transmission system, is analyzed. Hierarchical 16QAM is modulation system which has different constellation shape from conventional QAM and can provide users with high quality and low quality of data services simultaneously by controlling hierarchical modulation parameter. Assuming AWGN channel, SNR estimation performance characteristics are investigated considering hierarchical modulation parameter and type of constellation points. From simulation results, it is found that constellation point showing superior SNR estimation performance relative to other points is exist. Also, it is known that according to hierarchical modulation parameter, SNR estimation range with more accurate estimation performance is divided.

Unequal error protection scheme based hierarchical 16-QAM for 3-D video transmission

In this paper, an unequal error protection (UEP) scheme based on hierarchical quadrature amplitude modulation (HQAM) for three-dimensional (3-D) video transmission is proposed. The proposed scheme exploits unique characteristics of the color plus depth map stereoscopic video, where the color sequence has a more significant impact on the reconstructed video quality. The UEP scheme assigns more protection to the color sequence than the depth map so as to achieve high quality 3-D video. Different levels of protection are assigned through hierarchical 16-QAM. The color data with high priority (HP) are mapped onto the most significant bits (MSBs) of the 16- QAM constellation points and the depth map with low priority (LP) are mapped onto the less significant bits (LSBs). Simulation results demonstrate that the proposed UEP scheme outperforms the conventional equal error protection (EEP) schemes by up to 5 dB in terms of the received left and right views quality.

An Adaptive Hierarchical QAM Scheme for Enhanced Bandwidth and Power Utilization

Hierarchical quadrature amplitude modulation (HQAM) enables unequal priority transmission through the use of non-uniformly spaced constellations. In this paper, we propose an adaptive HQAM (A-HQAM) scheme where the ratios between the constellation distances are regularly adjusted based on the channel condition with the objective of maximizing the transmission efficiency. The source bit stream is divided into multiple sub-streams which are simultaneously transmitted, each on a different priority level. When using A-HQAM, the high priority sub-stream maintains an acceptable bit error rate performance over all channel conditions. As the channel condition improves, the required protection for the high priority sub-stream is reduced allowing for increasing the protection level of lower priority sub-streams. Hence, the number of sub-streams with acceptable BER performances is incrementally increased as the channel condition improves. Analysis and simulation results show that the proposed A-HQAM not only enhances the transmission efficiency but also provides reduced peak to average power ratio (PAPR). The proposed scheme offers reduced complexity by using one constellation size, unlike conventional adaptive schemes which require the use of several constellation sizes. Moreover, a practical A-HQAM implementation is presented which enables the receiver to successfully demodulate the received signal without knowing the varying transmission parameters.

Multi-Resolution Broadcast/Multicast Systems for MBMS

Multimedia Broadcast/Multicast Service (MBMS) supports downlink streaming and download-and-play type services to large groups of users. From the radio perspective, MBMS includes point-to-point (PtP) and point-to-multipoint (PtM) modes. This paper investigates and presents different multi-resolution broadcast systems for Wideband Code Division Multiple Access (WCDMA) cellular mobile networks, namely, multi-code, hierarchical QAM constellations and multi-antenna (MIMO) systems. Each one present performance gains over conventional single-resolution broadcast systems. A comparison is made between the three proposed multi-resolution systems. The use of High Speed Downlink Packet Access (HSDPA) to multicast video streaming as a multi-resolution system, associated or not to MIMO, can be employed by the MBMS PtP mode, but dependently on the deployment scenarios it can yield substantial reduction in resource demand and optimization of the allocated radio resources

Layered H.264 video transmission with hierarchical QAM

In multimedia communication systems, channel bandwidth and probability of error are the two main limitations that affect the quality of service. Therefore, in applications such as video over mobile networks, a video codec should cope with the erroneous situations of the channel as well as the bandwidth limitation. There are several techniques to make a video bitstream robust to the channel error. Layered video coding in conjunction with unequal error protection is a common method that provides error resilience. Hierarchical quadratic amplitude modulation is an efficient method that provides the unequal priority control for communication channels without adding any redundancy to the transmitted data. To generate the layers in the H.264/AVC video coding standard, the data partitioning technique has been included. Scalability is another efficient layering technique that is not entirely supported in the current specification of H.264/AVC. This paper proposes an SNR scalable scheme to adapt to the H.264/AVC codec. It contains new features that make it more efficient than the previous SNR scalable codecs. In this paper applying unequal error protection by hierarchical coding to both scalable and data partitioned bitstreams is analyzed. Simulation results show that the scalable scheme is more successful in conjunction with unequal error protection.

Prioritized transmission of data partitioned H.264 video with hierarchical QAM

In this letter, hierarchical quadrature amplitude modulation (HQAM) is used to provide unequal error protection (UEP) for layered (data partitioned) H.264 coded video. In a conventional HQAM system, the high-priority (HP) and low-priority (LP) capacities have a constant ratio, whereas in H.264 data partitioning, the corresponding parts do not necessarily have this constant ratio. This letter proposes a multilevel HQAM arrangement with adaptive constellation distances that provides a graceful degradation in the quality of the decoded video without requiring feedback from the receiver. The arrangement improves the quality relative to nonhierarchical transmission through poor signal-to-noise ratio (SNR) channels at the price of a modest quality reduction through good SNR channels.

New results on the BER of switched diversity combining over nakagami fading channels

New closed-form bit error rate (BER) expressions are derived for multibranch switched combining (SWC) systems with independent Nakagami faded diversity branches having integer Nakagami 717-parameters. Constellations considered include BPSK, M-PSK, M-PAM and M-QAM. The analysis is also applicable to the generalized hierarchical PAM and QAM modulation formats.

Pilot-assisted 16-level QAM for wireless video

This paper presents a twin-class transmission system for narrowband radio access channels suitable for handheld video phone and multimedia portable PC applications. The transmission system is comprised of a hierarchical 16-QAM modulation technique and a channel-coding scheme. The formation of dual-priority transmission is due to differing error resiliencies of the bits that make up a given symbol in a Gray-coded 16-QAM. On this basis, a twin-class pilot-assisted fade-estimation technique that can gracefully reduce the power loss caused by the transmission of pilot overhead is developed. The twin-class 16-QAM system is then used to transport a compressed video bitstream, which is partitioned to match the bit-error sensitivity of the transmitted symbol. The partitioning scheme is based on a separation of the variable-length (VL) coded discrete cosine transform (DCT) coefficients within each DCT block. This partitioning scheme is then applied to split the ITU-T H.263-coded bitstream. The scheme is suitable for constant bit-rate transmission (CBR), where the fraction of bits assigned to each of the two partitions can be adjusted according to the requirements of the unequal error protection scheme employed. The distribution of the VL-coded (VLC) information amongst the two partitions is performed adaptively. Finally, the performance of the partitioning scheme for transmission of video signals using our twin-class 16-QAM transmission system is evaluated under multipath fading conditions.

Classical and modern receiver architectures

This article is a review of several classical and modern wireless receiver architectures used in wideband wireless communication systems. The emphasis is on configurations suitable for integration on a single silicon chip. A full understanding of the design trade-offs discussed in this article is necessary for the proper introduction of a new modulation scheme presented in the article by Mirabbasi and Martin (2000) entitled, "Hierarchical QAM: a spectrally efficient DC-free modulation scheme".