Pattern Division Multiple Access Research Articles

Investigating power scaling factor for pattern division multiple access

Pattern division multiple access (PDMA) is a one type of multi-domain non-orthogonal multiple access (NOMA) that support massive connectivity and can improve spectral efficiency. The unique pattern is used by each user to map its transmitting data into a group of resource, which consist of frequency, code and spatial domain or combination of these resources. Power scaling and phase shifting are used to resolve ambiguity as consequence non uniform distribution of the received combined constellation. In this paper, we propose investigation on power scaling factor for each user in PDMA matrix to increase sum rate transmission and propose combine successive interference cancellation (SIC) based on diversity order and power scaling factor for each user. The simulation results confirm that the proper implement power scaling factor in pattern type 2 show best performance in Rician fading channels.

Residual Transceiver Impairments Aware Expectation Propagation Algorithm Receiver for PDMA Systems

Pattern division multiple access (PDMA) is a promising non-orthogonal multiple access technology for the next generation wireless communication systems. In PDMA systems, the inherent residual transceiver impairments introduced by nonideal hardwares incur significant performance degradation. In this paper, we propose a residual-transceiver-impairments-aware (RTIA) expectation propagation algorithm (EPA) receiver to mitigate the detrimental influences of the nonideal hardware imperfections for uplink PDMA systems. The user-specific transmitter distortion powers are considered in the message passing procedure of the EPA detection. The parallel interference cancellation (PIC) scheme is incorporated into the proposed RTIA-EPA receiver to further improve the system performance and reduce the computational complexity. Simulation results illustrate that the proposed RTIA-EPA and RTIA-EPA-PIC receivers achieve significant performance gains over the conventional residual-transceiver-impairments-agnostic counterparts with negligible computational complexity overhead.

Research on improved multiple users detection algorithm in pattern division multiple access system

Receiver detection algorithm has always been a research hotspot in communication system and the key point to determine the performance of 5G system. Both industry and academia have been committed to finding detection algorithms with lower complexity and higher detection performance. This paper will study how to solve the problems of low detection performance and high complexity of classical algorithms. Taking Pattern Division Multiple Access (PDMA) as an example, this paper improves the existing receiver detection algorithms such as Minimum Mean Square Error-Serial Interference Cancellation (MMSE-SIC), Message Passing Algorithm (MPA) and Expectation Propagation Algorithm (EPA), and puts forward corresponding improved algorithms with specific formulas, i.e. Enhanced-MMSE-SIC, Turbo-like MPA (MPA-Turbo) and Turbo-like EPA with hybrid parallel interference cancellation (EPA-Turbo-PIC). Link-level simulation results and analysis show that the proposed improved algorithms have performance advantages over the corresponding traditional algorithms.

A novel power allocation strategy for cooperative PDMA systems

Cooperative communication technology is of great importance for increasing the user reachable rate, further improving throughput and reducing the outage probability of non-orthogonal multiple access (NOMA) systems. This paper mainly studies the power allocation optimization method based on amplify-and-forward (AF) pattern division multiple access (PDMA) to obtain the maximum achievable throughput. We formulate an optimization problem of user power allocation in a downlink PDMA system with cooperative relaying, the exact expressions of system throughput and user outage probability of the AF-PDMA system are derived, and a novel power allocation optimization method based on uniform distribution and restricted constraints is proposed. The effectiveness of the restricted constraints and optimization method is verified by theoretical analysis and simulation. The studies we have performed showed that the proposed scheme with uniform distribution and restricted constraints can be significantly improved in terms of the system throughput in comparison to the case with a genetic algorithm (GA) and fixed power allocation scheme. Concerning the proposed method, the search space is reduced to 1/3 of the original feasible region, and the runtime of the algorithm accounts for only 20% of the GA runtime.

Investigation of pattern division multiple access technique in wireless communication networks

Recently, <span>pattern division multiple access (PDMA) is a non-orthogonal multiple access system that is now being developed in next-generation telecoms to address the requirement for mass connectivity. The core premise of non-orthogonal multiple access is to simultaneously serve multiple users with varying power levels across the same spectrum resources such as time, frequency, code, as well as space with minimal inter-user interference. A simulation analysis of significant technology enhancements focusing on PDMA aims to describe the benefits of the two plans now being examined by the third-generation partnership project for 5G technologies, namely filtered orthogonal frequency division multiplexing (F-OFDM) and windowed orthogonal frequency division multiplexing (W-OFDM), and to compare them to alternative modulation processes such as 16, 32, and 128 modulations. The research results explained the PDMA is less bit error rate used in multiple access technologies compare with W-OFDM and F-OFDM.</span>

Performance analysis of PDMA-based hybrid satellite–terrestrial networks with decode-and-forward relaying

As one of the most promising non-orthogonal multiple access (NOMA) technologies in 5G communication, pattern division multiple access (PDMA) has theoretically higher spectrum utilization and a larger communication capacity than conventional orthogonal multiple access (OMA) technologies. In this letter, PDMA is applied to hybrid satellite–terrestrial networks with decode-and-forward (DF) relaying in the downlink, and an in-depth study on the performance of outage probability (OP), ergodic capacity and system throughput is performed. For a more comprehensive analysis, hybrid satellite–terrestrial relay networks (HSTRNs) with conventional OMA technology are used in the comparative analysis. Analysis and simulation results show that PDMA-based hybrid satellite–terrestrial relay networks outperform the other system in terms of OP and ergodic capacity.

Uplink grant‐free pattern division multiple access transmission scheme by exploiting poly complementary sequence

AbstractNon‐orthogonal multiple access (NOMA) technology is a key technology of the future cellular mobile communication system. It provides services for users under different channel conditions through signal superposition transmission and spectrum multiplexing. Pattern division multiple access (PDMA) is a new NOMA technology based on the overall optimization of multi‐user communication system. Since the performance of PDMA mainly depends on the gain of the pattern matrix, we propose a design scheme of uplink PDMA pattern matrix for ultra‐reliable low latency communication (uRLLC). For the interference between users is a common problem in NOMA system, first, we use poly complementary sequence (PCS) as the spread codebook to spread the PDMA transmission signal and reduce interference. Meanwhile, an uplink power control scheme is proposed. It allocates wireless resources reasonably by jointly considering the interference between users and resource blocks within users (JUR), the corresponding outage probability formula is also derived. Simulation results show that compared with the previous researches, the pattern matrix design scheme and JUR power control scheme proposed in this article have greatly improved the transmission performance. The addition of PCS spread spectrum technology can significantly reduce the block error rate and outage probability.

Optimal Power Allocation for Cooperative Pattern Division Multiple Access Systems

This study focuses on the power allocation (PA) problem in code division multiple access (PDMA) networks with amplify-and-forward (AF) relays. We provide two wireless communication technical performance indexes, which are system throughput and outage probability. A multiobjective version of particle swarm optimization is proposed to solve Pareto-optimal solutions for optimal PA problems. A novel programming model is built based on improvement of constraint functions, and the accuracy and efficiency of solution can be improved via compact constraints. The technique for order preference by similarity to an ideal solution is proposed to balance the performance indicators, which include outage probability and system throughput. It has been calculated that the proposed approach for optimal PA is verified and performs better than a genetic algorithm approach.

Downlink Power Allocation Optimization in Pattern Division Multiple Access

Non-orthogonal multiple access (NOMA), in particular pattern division multiple access (PDMA), has been recently considered as the critical multiple access technologies deployed for 5G applications. However, optimizing power allocation (PA) at the base station (BS) to increase the sum throughput of the downlink (DL) PDMA system still remains a challenge. Although this problem has been explored to some extent by assuming that the BS can obtain perfect channel state information (CSI), this assumption is unfeasible in harsh environments. Therefore, to effectively improve the sum throughput of communications in the real world, we propose using PDMA with optimized PA. With perfect CSI, iterative power allocation (IPA) that can iteratively update the Lagrange multipliers is proposed. Using the Karush-Kuhn-Tucher (KKT) conditions, a PA solution with closed-form expressions is derived from increasing the sum throughput. With imperfect CSI, the outage probability is considered when maximizing the sum throughput. The probabilistic mixture problem can be converted into a non-probability problem, and thus, PA under imperfect CSI can be optimized with the proposed IPA algorithm. The simulation results demonstrate that the proposed scheme outperforms the existing schemes and can be effective in harsh environments.

Research on PDMA communication system based on complete complementary sequence

Pattern division multiple access (PDMA) is a new non-orthogonal multiple access (NOMA) technology. It is proposed to meet the challenge of 5G large-scale connectivity and high-frequency spectral efficiency. Compared with traditional orthogonal multiple access (OMA), PDMA can support more users through the allocation of non-orthogonal resources. Due to perfect aperiodic correlation, complete complementary sequence (CCS) greatly improves the spectrum efficiency of the system. It has been widely used in wireless communication and radar sensing, and it still has research value in 5G. In order to apply the advantages of CCS to NOMA communication system, this paper proposes a system model of CCS spread spectrum coding based on PDMA. CCS is used as spread spectrum code to improve the performance of PDMA communication system. At the same time, on the basis of spread spectrum technology, this paper analyzes the average power allocation algorithm and water-filling power allocation algorithm, and a dynamic power allocation algorithm based on the transmission rate and practical application is proposed. The simulation results show that the system model can effectively improve the performance of the system.

Activation Detection Algorithms for Pattern Division Multiple Access Uplink Grant-free Transmission

As a key technology of 5G, non orthogonal multiple access (NOMA) technology can significantly improve the spectrum efficiency compared with the traditional orthogonal multiple access technology. In addition, grant-free transmission technology can further reduce the transmission delay of the system and effectively improve the number of service users in the cell. In this paper, the pattern division multiple access (PDMA) technology (a typical NOMA technology) is taken as an example, PDMA technology based on Grant-free transmission (GF-PDMA) is studied, the uplink GF-PDMA pilot’s structure is designed and a user activation detection algorithms based on the received pilot’s power is proposed. The simulation results reviews that the algorithm proposed in this paper can fully meet the detection requirements of PDMA.

The Design of Receiver with Low Complexity for PDMA System

As one of promising non-orthogonal multiple access scheme, pattern division multiple access (PDMA) scheme is considered to be one competitive multiple access technology for the fifth generation (5G) communications. The detection algorithm is the key technology to improve the system performance. Due to the PDMA patterns sparse nature, belief propagation (BP) become one effective receiver algorithm to achieve close to maximum likelihood (ML) detection performance with lower complexity. However, the complexity order is still exponential with the row weight of the PDMA pattern and the modulation index. A novel receiver based on expectation propagation (EP) algorithm is proposed in this paper to reduce the complexity order from exponential to linear. This paper makes a comparison on the two algorithms above in terms of system performance and complexity. Link-level simulation results show that the proposed EP receiver achieves nearly the same performance as the BP receiver with orders less complexity.

Learning-Aided Resource Allocation for Pattern Division Multiple Access-Based SWIPT Systems

In this letter, a learning-aided resource allocation scheme based on the constrained Markov decision process (CMDP) is proposed to improve the average network energy efficiency (EE) with the constrained quality of service (QoS) in the pattern division multiple access (PDMA)-based simultaneous wireless information and power transfer (SWIPT) system. In order to solve the formulated CMDP resource allocation problem, the Lagrange duality is adopted to transform CMDP into an unconstrained Markov decision process (MDP). Due to the instability of the practical system, the Deep Q Network (DQN)-based CMDP scheme is proposed to obtain the optimal solution. The simulation results verify the proposed scheme converges faster than the benchmark in terms of increasing average network EE.

Performance analysis of cooperative PDMA with AF relaying over Rayleigh fading channels

This study investigates the performances of cooperative pattern division multiple access (PDMA) technology with a half-duplex amplify-and-forward (AF) relaying over Rayleigh fading channels. To characterise the performances of the AF-PDMA system, the closed-form expressions of the exact outage probabilities, system throughput and diversity order are derived, respectively. The particle swarm optimisation algorithm based on penalty function is used to obtain the optimum power allocation coefficients by maximising the system throughput. By setting different values on the target data rate for users to analyse the AF-PDMA system throughput performance, simulation results demonstrate the performance enhancement of the considered AF-PDMA compared with orthogonal multiple access with AF relaying and PDMA with decode-and-forward relaying.

Demonstration of Pattern Division Multiple Access With Message Passing Algorithm for Multi-Channel mmWave Uplinks via RoF Mobile Fronthaul

Orthogonal multiple access (OMA) such as orthogonal frequency division multiple access (OFDMA) has been the predominant access technology adopted by the current generation of mobile communication. Representing an evolutionary step in radio access networks, non-orthogonal multiple access (NOMA) is considered to be a promising technology to meet the goals of increased capacity, enhanced flexibility, and reduced latency. Pattern division multiple access (PDMA) is a NOMA scheme using resource-element mapping as the multiple-access signature in the symbol level. This article introduces PDMA in a millimeter-wave (mmWave) radio access system with systematic experimental demonstration. One key advantage of PDMA is that it can facilitate advanced parallel interference cancellation (PIC) in the decoding process. A message passing algorithm (MPA) is developed and implemented in this article to enhance the decoding performance of PDMA. A novel PDMA system integrated with MPA is experimentally demonstrated in a multi-user mmWave radio access system that uses radio-over-fiber (RoF) mobile fronthaul, achieving reduced sensitivity penalty and improved modulation spectral efficiency compared to conventional power-domain NOMA (PD-NOMA) with successive interference cancellation (SIC). Experimental results show that PDMA is capable of supporting disparate channel conditions, adapting to various patterns, and providing improved system flexibility.

MULTI USER BASED PERFORMANCE ANALYSIS IN UPCOMING 5G TECHNIQUES

The 5G technology will provide high spectral efficiency and low latency for users around the world. To address the requirements the non-orthogonal schemes such as sparse code multiple access (SCMA), multiuser shared access (MUSA), pattern division multiple access (PDMA) are considered in this article. The Symbol error rate (SER) performance is calculated and plotted for different number of users, the analysis of PDMA and SCMA is examined for same factor graph. The average SER is calculated for three NOMA techniques for different users in the hexagonal shape cell under different Signal to Noise Ratio values. The SCMA shows 3% improvement in average SER value when compare to PDMA and MUSA techniques.

Energy efficient transmission in dynamic PDMA‐based systems with RF energy harvesting

AbstractNonorthogonal multiple access (NOMA) and energy harvesting technologies are two promising approaches to increase spectral and energy efficiency, respectively. In this paper, a pattern division multiple access (PDMA) uplink transmission network in which users are able to harvest energy from the received radio frequency power is considered. In order to maximize the energy efficiency, we perform resource allocation in the power, subcarrier, and time domains. Also, for each time slot, the pattern matrix is determined dynamically. To enhance the detection reliability, successive interference cancellation and maximal ratio combining at each receiver are utilized. For resource allocation, the actual harvested and available energies of the users are considered. Moreover, in order to perform a comprehensive analysis, further to PDMA, the energy efficiency of the power domain NOMA (PD‐NOMA) is also investigated and the results are compared. It is shown that the energy efficiency and the average total transferred data of PDMA are higher than that of PD‐NOMA.

Multiple Codebook-Based Non-Orthogonal Multiple Access

Observing that employing a single codebook (CB) per user transmission block in the conventional CB-based non-orthogonal multiple access (NOMA) schemes doesn't exploit code and interference diversity and has limitations in some unfavorable channel conditions, this letter presents multiple CB-based NOMA (MC-NOMA) in which multiple CBs are employed by a user in a round robin manner. Performance of schemes such as sparse code multiple access (SCMA) and pattern division multiple access (PDMA) is improved by MC-NOMA without incurring any additional receiver complexity and loss in spectral efficiency. Furthermore, to fully exploit code and interference diversity for MC-NOMA, CBs assignment algorithm is presented.

Design of MIMO‐PDMA in 5G mobile communication system

As a novel non-orthogonal multiple access scheme for fifth generation mobile networks, pattern division multiple access (PDMA) can support more connectivity and significantly improve spectral efficiency compared with conventional orthogonal multiple access (OMA). In order to further to improve the system transmission reliability and spectrum efficiency for PDMA, a novel PDMA framework combined with multiple-input multiple-output (MIMO) technology by using space–frequency block coding scheme for downlink transmission is proposed in this study. The performance analysis expressions of system capacity for MIMO-PDMA and MIMO-OMA are derived. The detailed MIMO-PDMA design diagrams for transmitting and receiving end are presented and the equivalent space and frequency channel matrix for each user are derived to facilitate the performance evaluation of the proposed framework. The simulation results are provided to demonstrate that the integration of the two technologies can achieve better performance compared with traditional PDMA and MIMO-OMA.

Low Complexity Iterative Receiver With Lossless Information Transfer for Non-Binary LDPC Coded PDMA System

In this work, we first proposed a non-binary low-density parity-check (NB-LDPC) coded pattern division multiple access (PDMA) scheme with the order of the Galois field equal to the size of modulation alphabet which can avoid the symbol-to-bit or bit-to-symbol probability conversion between the detector and decoder as in binary coded system. Specifically, we considered a 4-ary LDPC over Galois field (GF(4)-LDPC) coded PDMA system with quadrature phase shift keying (QPSK) modulation. At the receiver side, Gaussian approximation based message passing (GAMP) detection algorithm instead of standard message passing (SMP) is employed to achieve a tradeoff between the computational complexity and the detection performance. When iterative detection and decoding (IDD) algorithm is used, the symbol-wise extrinsic information of the detector and GF(4)-LDPC decoder can be exchanged without information loss. At last, we proposed a symbol-wise EXIT (S-EXIT) based iterative optimization algorithm to improve the system performance. Both the S-EXIT chart based analysis and numerical simulation results show the validity of the proposed scheme above.