This paper is concerned with sparse code multiple access (SCMA) with protograph-based low-density parity-check (P-LDPC) codes over Rayleigh fading channels. To be specific, we first propose a two-step design method consisting of both low-density factor graph (LDFG) and energy-based constellation superposition (ECS) principles to construct a new type of non-uniform codebooks (CBs), which have superior robustness against inter-user interference. We also develop a new segment-wise interleaved transmission (SWIT) scheme, which features a systematic optimization among repetition coding, resource mapping, and cross-slot data coupling, to further improve the performance of P-LDPC-coded SCMA. Additionally, we conceive a decoding-threshold-guided multi-objective optimization (DT-MOO) method to construct protograph-based enhanced multi-user codes (EMUCs), which exhibit excellent error-rate performance under both turbo and non-turbo decoding compared to traditional single-user and existing multi-user codes. Theoretical and simulated results validate the superiorities of proposed non-uniform SCMA scheme with SWIT and EMUCs compared to state-of-the-art benchmarks. Owing to the above advantages, the proposed designs are competent to provide massive connectivity and energy-efficient transmission for simultaneous wireless information and power transfer (SWIPT) applications in 6G networks.

This work investigates iterative receiver and code design for protograph-coded overloaded sparse code multiple access (SCMA) systems. As a type of non-orthogonal multiple access (NOMA) technology, SCMA relies on an iterative detection and decoding (IDD) receiver to eliminate inter-user interference and channel noise. However, the existing IDD receiver requires a larger number of iterations to achieve successful convergence. To overcome this limitation, we propose aranked successive detection and decoding(R-SDD) receiver, which dynamically allocates computational resources to bottleneck users with the lowest reliability. This approach accelerates information convergence and improves error performance without increasing overall complexity. Moreover, we introduce afactor-graph-based(FG) interleaving scheme for the proposed SCMA systems, which outperforms the existing interleaver. To further enhance the error-correction capability for overloaded multi-user scenarios, we propose a new protograph design principle tailored for SCMA systems and develop two high-performance protograph low-density parity-check (LDPC) codes, achieving over 0.3 dB improvement compared with the state-of-the-art alternatives. Owing to the salient advantages of the new iterative receiver and code design, the proposed SCMA system offers a promising solution for future high-bandwidth, high-reliability communication networks.

The study of anytime codes over non-ergodic block-fading (BF) channels remains largely unexplored. To address this gap, we propose a novel root-protograph-based anytime (RP-anytime) coding framework and develop modified density evolution (DE) equations. Leveraging these equations, we introduce two performance metrics to evaluate the asymptotic behavior of RP-anytime codes under the assumption of infinite frame length: the average asymptotic bit error rate (BER), which characterizes anytime reliability, and the anytime outage region, which reflects the code’s ability to achieve full diversity. Using these metrics, we analyze the performance of the proposed RP-anytime codes and compare them with both root-protograph LDPC codes and conventional anytime codes. The results demonstrate the superiority of the RP-anytime structure in terms of reliability and diversity over non-ergodic BF channels. Furthermore, we employ a multi-objective differential evolution (MODE) algorithm to design optimized RP-anytime codes. Simulation results confirm that the newly designed codes achieve excellent anytime reliability, full diversity, and near-outage-limit error performance—significantly outperforming prior-art root-protograph LDPC codes and anytime codes.

This work studies the transceiver design and convergence performance analysis for the hierarchical modulation (HM) systems with protograph-based low-density parity-check (P-LDPC) codes. Specifically, we first conceive new source-constrained (SC) coding scheme and inter-layer-cascaded (ILC) decoding scheme tailored for the HM-based transmitter and receiver, respectively. Both the proposed SC coding and ILC decoding schemes form an enhanced version of bit-interleaved-coded HM (BIC-HM) systems, namely source-constrained HM (SC-HM) systems, providing a more reliable and flexible multi-data transmission solution. Moreover, according to the SC coding principle, we conceive a novel variable-node-degree-based (VND) multiplexing scheme to further improve the performance of the proposed SC-HM systems. Additionally, based on the ILC decoding framework, we devise a novel mutual information (MI) analysis tool, namely ILC-based extrinsic-information-transfer (ILC-EXIT) algorithm, to predict the decoding thresholds of the proposed P-LDPC-coded SC-HM systems. Theoretical and simulation results demonstrate that the proposed SC-HM systems significantly outperform the existing benchmarks in terms of error performance, decoding latency, and transmission-rate adaptation.

To enhance the adaptability and performance of multi-stream transmissions over non-ergodic block fading (BF) channels, this paper studies a multilevel-priority incremental-redundancy hybrid ARQ (MP-IR-HARQ) system with nested root-protograph-based low-density parity-check (NRP-LDPC) codes. Specifically, we analyze the performance of traditional RP-LDPC codes and reveal that they are unable to achieve full diversity in the IR-HARQ system over non-ergodic BF channels. To address this limitation, we propose a design methodology to construct a family of NRP-LDPC codes having the full-diversity property, throughput-limit-approaching property, outage-limit-approaching performance, and rate compatibility tailored for the IR-HARQ system. Additionally, we incorporate a multilevel-priority design composed of the adaptive modulation, adaptive detection, and successive decoding into the traditional IR-HARQ framework. The designed MP-IR-HARQ system can support the transmission of multiple data streams while providing unequal error protection (UEP) across them. The outage-boundary analyses, throughput analyses, and word-error-rate (WER) simulations demonstrate that the proposed NRP-LDPC-coded MP-IR-HARQ system can not only significantly outperform prior-art counterparts over non-ergodic BF channels, but also enable the multi-data-stream-based UEP transmission.

Recent research in price-based Mobile Edge Computing (MEC) has predominantly aimed at maximizing edge server revenue by efficiently allocating computing resources. While this operational approach has certainly strengthened the edge computing industry, the practical deployment scenario's impact on server hardware lifespan has not been fully explored. In this paper, we introduce a novel server pricing strategy that accounts for the influence of CPU temperature on the server's longevity, all while ensuring the quality of service requirements for time-sensitive User Equipments (UEs). Leveraging these insights, we establish an MEC system model with a single MEC server and multiple UEs, which we then formulate as a Stackelberg game. We derive two closed-form solutions considering various UEs' conditions, closely aligning with the expectations of time-sensitive UEs. Our simulation results showcase the effectiveness of our proposed method in safeguarding hardware equipment while minimizing revenue loss.

This paper is centered on multiple-input multiple-output visible light communication (MIMO-VLC) systems with protograph-based low-density parity-check (P-LDPC) codes. We propose a two-step design method, which is composed of spatial-domain (SpD)-based Gray-like (GL) principle and signal-domain (SiD)-based energy-optimization (EO) principle, to construct a novel class of generalized spatial modulation (GSM) schemes, referred to asGLEOGSM schemes, to enhance the system performance. We also introduce a novel internal-stopping (IS) principle into the conventional joint detection and decoding (JDD) architecture, the resultant IS-aided JDD (IS-JDD) algorithm significantly reduces the computational overhead. Inspired by the proposed IS-JDD architecture, we further conceive a low-complexity IS-aided extrinsic-information-transfer (IS-EXIT) algorithm to analyze the convergence performance of P-LDPC-coded MIMO-VLC systems. Both theoretical and simulation results verify that our proposed designs can remarkably outperform the existing benchmark schemes in terms of capacity, convergence and complexity.

Orbital angular momentum (OAM) is a mode division multiplexing (MDM) technique enabling simpler implementation and higher capacity than conventional multiple-input multiple-output (MIMO) over line-of-sight (LoS) channels. This paper studies the joint design of protograph low-density parity-check (PLDPC) codes and shaping index modulation (IM) in OAM systems. To begin with, we analyze the distribution of extrinsic log-likelihood-ratios (LLRs) for coded bits output from channel detector, and then propose a customized Box-Cox transformation (CBCT) to make the distribution achieve symmetry and Gaussian features. We also devise a CBCT-based protograph extrinsic information transfer (CBCT-PEXIT) algorithm to predict the convergence performance of PLDPC-coded OAM systems. Furthermore, with the aid of such an algorithm, we construct two new types of improved PLDPC codes tailored for OAM systems, including unpunctured codes and rate-compatible punctured codes. In addition, we present a two-step design method, which seamlessly combines the shaping technique and index rule into a novel modulation scheme, calledshaping index. Both theoretical analyses and simulation results demonstrate that the proposed PLDPC-coded OAM systems with shaping index significantly outperform state-of-the-art counterparts.

Anytime code is a new class of error-correcting code that has very long coding memory and is decodable with flexible decoding window size (decoding delay). It is designed for real-time reliable applications, such as tracking and controlling unstable systems. In this paper, we construct a family of rate-compatible (RC) Anytime code ensembles with code rate from 0 to 1 based on spatially coupled repeat-accumulate (SC-RA) codes and apply them to the automatic-repeat-request (ARQ) communication with incremental redundancy. Using density evolution (DE) analysis, we prove that each element code within the RC family has superior Anytime-reliable properties over the binary erasure channel (BEC) and the binary-input additive white Gaussian noise (BI-AWGN) channel. In addition, we develop an expanding-window IR-HARQ (incremental redundancy hybrid automatic-repeat-request) scheme for the proposed RC Anytime codes. Simulation results testify that our proposed RC Anytime codes have better decoding performance than the prior-art RC Anytime codes. Furthermore, when combined with the proposed expanding-window IR-HARQ scheme, our proposed RC Anytime codes show significant advantages over the conventional RC low-density parity-check (LDPC) codes and RC polar codes in the conventional CRC-based IR-HARQ communication systems.

The Intelligent Reflection Surface (IRS) is a crucial technology for the development of next-generation wireless mobile networks. However, its deployment is usually limited to Line-of-Sight (LoS) transmission paths of Base Stations (BSs) due to path-loss and beamforming restrictions. LoS wireless channels are known to have low-rank characteristics, which significantly reduce the capacity of IRS-assisted communication links. To overcome this issue, we propose a new IRS transmission scheme using vortex beams. These beams have low correlation properties between different modes, thus improving the channel capacity for served users. In this paper, we detail the channel capacity comparison of IRS systems using vortex beams and conventional plane waves. Additionally, a 2-bit phase quantized IRS prototype is designed and tested through full-wave Electro-Magnetic (EM) simulations and actual transmission experiments, allowing for the conversion of mode 1 vortex beams and plane waves at a pre-determined reflection angle (e.g., 30°). Our simulation results and prototype tests show that this design is effective in manipulating reflected vortex beams and plane waves in 3D space, meeting the demands of future intelligent wireless communications.

As a spectral-efficiency technique for unequal error protection (UEP), hierarchical modulation (HM) bit-interleaved coded modulation (BICM) with iterative decoding (ID) has attracted interests in the wireless communication community. In this article, we conduct an investigation on spatially coupled (SC) protograph low-density parity-check (P-LDPC)-coded M-ary quadrature amplitude modulation (QAM) HM-BICM-ID systems. We first develop an information-theoretic methodology to calculate (log2M)/2 types of constellation-constrained average mutual information (AMI), which can be used to characterize the performance limits of different layers in the HM-BICM systems. We further propose a two-stage design approach to construct a novel type of constellations, called as structural quadrant (SQ) constellations, and develop a quadrant-based harmonic mean analysis to evaluate the nonfeedback and iterative-feedback asymptotic performance of the proposed constellations. In addition, we conceive a performance-analysis tool, referred to as multistream-based extrinsic information transfer (MS-EXIT) algorithm, for predicting the decoding thresholds of all individual coded-bit streams in the proposed SC P-LDPC-coded HM-BICM-ID systems. Simulation results not only agree well with the theoretical analyses but also indicate that the proposed SC P-LDPC-coded HM-BICM-ID systems are remarkably superior to the state-of-the-art counterparts. Thereby, the proposed SC P-LDPC-coded HM-BICM-ID systems are competent to provide diverse Quality of Service (QoS) for future wireless applications, such as 6G-enabled Internet of Things (IoT).