scholarly journals Effective capacity analysis of reconfigurable intelligent surfaces aided NOMA network

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Geng Li ◽  
Huiling Liu ◽  
Gaojian Huang ◽  
Xingwang Li ◽  
Bichu Raj ◽  
...  
Keyword(s):  
Multiple Access ◽  
Signal To Noise Ratio ◽  
Analytical Approximation ◽  
Effective Capacity ◽  
Green Communication ◽  
Time Service ◽  
Delay Sensitive ◽  
Sixth Generation ◽  
System 2 ◽  
Evaluation Metric

AbstractThe future sixth generation (6G) is going to face the significant challenges of massive connections and green communication. Recently, reconfigurable intelligent surfaces (RIS) and non-orthogonal multiple access (NOMA) have been proposed as two key technologies to solve the above problems. Motivated by this fact, we consider a downlink RIS-aided NOMA system, where the source aims to communicate with the two NOMA users via RIS. Considering future network supporting real-time service, we investigate the system performance with the view of effective capacity (EC), which is an important evaluation metric of delay sensitive systems. Specifically, we derive the analytical expressions of the EC of the near and far users. To obtain more useful insights, we deduce the analytical approximation expressions of the EC in the low signal-to-noise-ratio approximation by utilizing Taylor expansion. Moreover, we provide the results of orthogonal multiple access (OMA) for the purpose of comparison. It is found that (1) The number of RIS components and the transmission power of the source have important effects on the performance of the considered system; (2) Compared with OMA, NOMA system has higher EC due to the short transmission time.

scholarly journals Effective Capacity Analysis of Reconfigurable Intelligent Surfaces Aided NOMA Network

2021 ◽  
Author(s):  
Geng Li ◽  
Huiling Liu ◽  
Gaojian Huang ◽  
Xingwang Li ◽  
Bichu Raj ◽  
...  
Keyword(s):  
Multiple Access ◽  
Signal To Noise Ratio ◽  
Analytical Approximation ◽  
Base Station ◽  
Effective Capacity ◽  
Green Communication ◽  
Time Service ◽  
Delay Sensitive ◽  
Sixth Generation ◽  
Evaluation Metric

Abstract The future sixth generation (6G) is going to face the significant challenges of massive connections and green communication. Recently, reconfigurable intelligent surfaces (RIS) and non-orthogonal multiple access (NOMA) have been proposed as two key technologies to address the above problems. Motivated by this fact, we consider a downlink RIS-aided NOMA system, where the base station seeks to communicate with two NOMA users with the aid of a RIS. Considering future network supporting real-time service, we investigate the system performance with the view of effective capacity (EC), which is an important evaluation metric of sensitive to delay sensitive system. Based on this basis, we derive the analytical expressions of the EC of the near and far users. To obtain more useful insights, we deduce the analytical approximation expressions of the EC in the low signal-to-noise-ratio (SNR) approximation by utilizing Taylor expansion. In order to compare, we provide the results of orthogonal multiple access (OMA). It is found that 1) The number of RIS components and the transmission power of the base station have important effects on the performance of the considered system model. 2) Compared with OMA, NOMA system has higher effective capacity due to the short transmission time.

scholarly journals Delay-Sensitive NOMA-HARQ for Short Packet Communications

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 880
Author(s):  
Faisal Nadeem ◽  
Mahyar Shirvanimoghaddam ◽  
Yonghui Li ◽  
Branka Vucetic
Keyword(s):  
Markov Model ◽  
Error Rate ◽  
Multiple Access ◽  
Time Slot ◽  
Packet Error Rate ◽  
Packet Delivery ◽  
Delivery Delay ◽  
Delay Sensitive ◽  
Optimal Power ◽  
Short Packet

This paper investigates the two-user uplink non-orthogonal multiple access (NOMA) paired with the hybrid automatic repeat request (HARQ) in the finite blocklength regime, where the target latency of each user is the priority. To limit the packet delivery delay and avoid packet queuing of the users, we propose a novel NOMA-HARQ approach where the retransmission of each packet is served non-orthogonally with the new packet in the same time slot. We use a Markov model (MM) to analyze the dynamics of the uplink NOMA-HARQ with one retransmission and characterize the packet error rate (PER), throughput, and latency performance of each user. We also present numerical optimizations to find the optimal power ratios of each user. Numerical results show that the proposed scheme significantly outperforms the standard NOMA-HARQ in terms of packet delivery delay at the target PER.

scholarly journals Secrecy-Oriented Optimization of Sparse Code Multiple Access for Simultaneous Wireless Information and Power Transfer in 6G Aerial Access Networks

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Jingmin Zhang ◽  
Xiaokui Yue ◽  
Xuan Li ◽  
Haofei Zhang ◽  
Tao Ni ◽  
...  
Keyword(s):  
Multiple Access ◽  
Optimization Methods ◽  
Access Networks ◽  
Spectrum Efficiency ◽  
Sparse Code ◽  
Power Splitting ◽  
Power Transfer ◽  
Sixth Generation ◽  
Successive Convex Approximation ◽  
Iot Devices

This article focuses on the simultaneous wireless information and power transfer (SWIPT) systems, which provide both the power supply and the communications for Internet-of-Things (IoT) devices in the sixth-generation (6G) network. Due to the extremely stringent requirements on reliability, speed, and security in the 6G network, aerial access networks (AANs) are deployed to extend the coverage of wireless communications and guarantee robustness. Moreover, sparse code multiple access (SCMA) is implemented on the SWIPT system to further promote the spectrum efficiency. To improve the speed and security of SWIPT systems in 6G AANs, we have developed an optimization algorithm of SCMA to maximize the secrecy sum rate (SSR). Specifically, a power-splitting (PS) strategy is applied by each user to coordinate its energy harvesting and information decoding. Hence, the SSR maximization problems in the SCMA system are formulated in terms of the PS and resource allocation, under the constraints on the minimum rates and minimum harvested energy of individual users. Then, a successive convex approximation method is introduced to transform the nonconvex problems to the convex ones, which are then solved by an iterative algorithm. In addition, we investigate the SSR performance of the SCMA system supported by our optimization methods, when the impacts from different perspectives are considered. Our studies and simulation results show that the SCMA system supported by our proposed optimization algorithms significantly outperforms the legacy system with uniform power allocation and fixed PS.

scholarly journals Nearest Neighbor Decoding and Pilot-Aided Channel Estimation for Fading Channels

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 971
Author(s):  
A. Taufiq Asyhari ◽  
Tobias Koch ◽  
Albert Guillén i Fàbregas
Keyword(s):  
Channel Estimation ◽  
Fading Channels ◽  
Multiple Access ◽  
Nearest Neighbor ◽  
Signal To Noise Ratio ◽  
Multiple Input Multiple Output ◽  
Comparative Performance ◽  
Single Output ◽  
Multiple Input ◽  
Flat Fading

We study the information rates of noncoherent, stationary, Gaussian, and multiple-input multiple-output (MIMO) flat-fading channels that are achievable with nearest neighbor decoding and pilot-aided channel estimation. In particular, we investigate the behavior of these achievable rates in the limit as the signal-to-noise ratio (SNR) tends to infinity by analyzing the capacity pre-log, which is defined as the limiting ratio of the capacity to the logarithm of the SNR as the SNR tends to infinity. We demonstrate that a scheme estimating the channel using pilot symbols and detecting the message using nearest neighbor decoding (while assuming that the channel estimation is perfect) essentially achieves the capacity pre-log of noncoherent multiple-input single-output flat-fading channels, and it essentially achieves the best so far known lower bound on the capacity pre-log of noncoherent MIMO flat-fading channels. Extending the analysis to fading multiple-access channels reveals interesting relationships between the number of antennas and Doppler bandwidth in the comparative performance of joint transmission and time division multiple-access.

scholarly journals Design and spectral analysis of mixed-carrier communication for sixth-generation networks

2020 ◽  
Vol 476 (2238) ◽  
pp. 20200165
Author(s):  
Ahmed F. Hussein ◽  
Hany Elgala
Keyword(s):  
Signal To Noise Ratio ◽  
Design Procedure ◽  
Optical Power ◽  
Spectrum Management ◽  
Visible Light Communications ◽  
Experimental Proof ◽  
Millimetre Wave ◽  
Trade Offs ◽  
Sixth Generation ◽  
Carrier Communication

The fifth-generation (5G) wireless cellular network is expected to be ready for commercialization within this year. The huge spectrum enabled by the millimetre-wave (mm-Wave) technology is expected to introduce a hype in data usage per user. The 5G is also expected to concurrently support a wide variety of services; however, the practical trade-offs associated with concurrent services require further investigations. In this work, a physical layer (PHY) design to support visible light communications is considered to efficiently support concurrent services that are essential to serve the needs of the sixth-generation (6G) network. A novel communication technique, i.e. mixed-carrier communication (MCC), is proposed. MCC enables simultaneous wireless services such as broadband access, low-rate internet-of-things connectivity, device-free sensing, and device-based localization. This study presents, firstly, a thorough investigation of the design procedure of the novel MCC PHY, secondly, the spectral profile of MCC towards proper spectrum management and interference analysis, and thirdly, performance evaluation based on modelling, simulation and an experimental proof-of-concept. The design steps recommend that the system performance degrades beyond a signal-to-noise ratio (SNR) threshold. For instance, SNR of 25.1 dB and 2.6652 optical power ratio between the communications signal and the driving envelope, for 64-quadrature amplitude modulation (64-QAM), are recommended to avoid performance degradation due to clipping. Simulation results show an interference-immune performance of a properly managed spectrum. For a bit-error-rate (BER) of 10 −3 , an SNR penalty of 2–5 dB is observed for different interference scenarios. The experimental measurements illustrate a high-quality signal of 21 dB SNR at 50 cm and 10 −3 BER using 64-QAM.

Orthogonal Power Division Multiple Access: A Green Communication Perspective

2016 ◽  
Vol 34 (12) ◽  
pp. 3828-3842 ◽  
Author(s):  
Weijia Han ◽  
Yan Zhang ◽  
Xijun Wang ◽  
Jiandong Li ◽  
Min Sheng ◽  
...  
Keyword(s):  
Multiple Access ◽  
Green Communication

Performance of Multi-User Transmitter Pre-Processing Assisted Multi-Cell IDMA System for Downlink Transmission

2015 ◽  
Vol 14 (03) ◽  
pp. 1550030 ◽  
Author(s):  
B. Partibane ◽  
V. Nagarajan ◽  
K. S. Vishvaksenan ◽  
R. Kalidoss
Keyword(s):  
Multiple Access ◽  
Signal To Noise Ratio ◽  
Minimum Mean Square Error ◽  
Multiple Access Interference ◽  
Base Station ◽  
Least Square ◽  
Complex Signal ◽  
Delay Spread ◽  
Downlink Transmission ◽  
Mmse Detector

In this paper, we present the performance of multi-user transmitter pre-processing (MUTP) assisted coded-interleave division multiple access (IDMA) system over correlated frequency-selective channels for downlink communication. We realize MUTP using singular value decomposition (SVD) technique, which exploits the channel state information (CSI) of all the active users that is acquired via feedback channels. We consider the MUTP technique to alleviate the effects of co-channel interference (CCI) and multiple access interference (MAI). To be specific, we estimate the CSI using least square error (LSE) algorithm at each of the mobile stations (MSs) and perform vector quantization using Lloyd's algorithm, and feedback the bits that represents the quantized magnitudes and phases to the base station (BS) through the dedicated low rate noisy channel. Finally we recover the quantized bits at the BS to formulate the pre-processing matrix. The performance of MUTP aided IDMA systems are evaluated for five types of delay spread distributions pertaining to long-term evolution (LTE) and Stanford University Interim (SUI) channel models. We also compare the performance of MUTP with minimum mean square error (MMSE) detector for the coded IDMA system. The considered TP scheme alleviates the effects of CCI with less complex signal detection at the MSs when compared to MMSE detector. Further, our simulation results reveal that SVD-based MUTP assisted coded IDMA system outperforms the MMSE detector in terms of achievable bit error rate (BER) with low signal-to-noise ratio (SNR) requirement by mitigating the effects of CCI and MAI.

scholarly journals On the Performance Balancing for Uplink NOMA Systems

2020 ◽  
Vol 13 (6) ◽  
pp. 454-459
Author(s):  
Nam-Soo Kim ◽  
Keyword(s):  
Outage Probability ◽  
Multiple Access ◽  
Signal To Noise Ratio ◽  
Ergodic Capacity ◽  
Base Station ◽  
Cellular Systems ◽  
Mobile Cellular ◽  
Noise Ratio ◽  
Outage Probabilities ◽  
Error Floors

Outage probability and capacity are the representative performance measures for the quality of service (QoS) in mobile cellular systems. Recently, power back-off scheme is proposed in uplink non-orthogonal multiple access (NOMA) systems. The power back-off scheme improves the performance of a near user, however, decreases that of a far user. In comparison, the scheme indicates the error floors with an outage probability of 2.4×〖10〗^(-1) and 9.1×〖10〗^(-2) with power back-off 5 dB and 10 dB, respectively under the specified condition. To address these drawbacks, we propose an equal average signal-to–interference plus noise ratio (SINR) scheme that derives the same average SINR from active users at the base station (BS) in uplink non-orthogonal multiple access (NOMA) systems. Numerical results show that required signal-to-noise ratio (SNR) for the outage probability of 1×〖10〗^(-3) of the near and far users are close enough within 1 dB, which means an outage balance between two users. And it is noticed that the outage probabilities in the proposed scheme decrease as the increase of the received SNR without error floors. Also, different from the power back-off scheme, we noticed that the capacities of the two users in the proposed scheme are coincident and increase with SNR. The outage probabilities and ergodic capacity of the near and far users are derived in closed-form expressions. The analytical results are conformed by Monte Carlo simulation.

scholarly journals Non-Orthogonal Multiple Access Assisted Device-to-Device Communication: Best Helping Base Station Approach

2018 ◽  
Vol 12 (2) ◽  
pp. 803
Author(s):  
Huu-Phuc Dang ◽  
Minh-Sang Nguyen ◽  
Dinh-Thuan Do
Keyword(s):  
Data Transmission ◽  
System Performance ◽  
Multiple Access ◽  
Signal To Noise Ratio ◽  
Base Station ◽  
Selection Scheme ◽  
Channel Condition ◽  
Expected Performance ◽  
Realistic Assumption ◽  
Device To Device

<span>It can be studied in this paper that a cooperative non-orthogonal multiple access (NOMA) helps device-to-device (D2D) communication system through base station (BS). In particular, we investigate BS selection scheme as a best channel condition for dedicated devices where a different data transmission demand on each device is resolved. The analysis on amplifying-and forward (AF) relay is proposed to evaluate system performance of the conventional cooperative NOMA scheme. Under the realistic assumption of perfect channel estimation, the achievable outage probability of both devices is investigated, and several impacts on system performance are presented. The mathematical formula in closed form related to probability has also been found. By implementing Monte-Carlo simulation, the simulation results confirm the accuracy of the derived analytical results. Also, the proposed D2D cooperative NOMA system introduces expected performance on reasonable selected parameters in the moderate signal to noise ratio (SNR) regime.</span>

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