Target Data Rate Research Articles

Real-Valued Spreading Sequences for PSSS Based High-Speed Wireless Systems

In past years, Parallel Sequence Spread Spectrum (PSSS) has attracted significant attention as a modulation technique for wireless communication systems targeting data rates of 100 Gb/s and beyond. PSSS allows designing high-speed baseband processors, which can be partially implemented in the analog domain. It uses multiple analog-to-digital converters (ADCs) to sample the received baseband signal in parallel, significantly relaxing the sampling rate and ADC complexity. However, due to the sidelobe effects of bipolar <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> -sequences, PSSS shows lower performance than standard digital modulation schemes. This paper proposes real-valued PSSS spreading sequences with attenuated autocorrelation sidelobes. Such sequences show excellent bit error rate (BER) performance. Moreover, our sequences do not have length restrictions of 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sup> – 1, like in the case of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> -sequences, and reduce the chip area required to implement PSSS transceiver. The proposed sequences also reduce the peak-to-average power ratio (PAPR) of PSSS.

Estimation Techniques for MIMO-OFDM-A Review

In the context of Third-Generation Partnership Project Long-Term Evolution (3GPP LTE), the target data rates are 100 Mb/s in downlink and 50 Mb/s in uplink, and other system features include flexible bandwidths and moderate power consumption of mobile terminals. While the previous 3GPP generations, namely, 3G UMTS and 3.5G HSPA, rely on code-division multiple access (CDMA), LTE adopts orthogonal frequency-division multiple access (OFDMA)-based technologies for its uplink and downlink. Due to high peak-to-average power ratio (PAPR) of OFDMA signals, the single- carrier frequency division multiple access (SC-FDMA), also known as discrete Fourier transform (DFT)-spread OFDMA, has been selected for the uplink transmission in 3GPP LTE systems. SC-FDMA has similar throughput performance as OFDMA but with lower PAPR to increase power efficiency and is less sensitive to frequency synchronization errors, which makes it favorable for mobile terminals.

Outage Analysis and Reliability Enhancement of Hybrid VLC-RF Networks Using Cooperative Non-Orthogonal Multiple Access

Visible light communication (VLC) is a promising communication technology that benefits from several advantages over other wireless communication techniques. However, the capacity of VLC systems is limited by the low modulation bandwidth of light-emitting diodes (LEDs) used as transmitters. To circumvent this bottleneck, non-orthogonal multiple access (NOMA) is popularly used in VLC systems. However, due to high inter-user interference at the receivers, NOMA suffers from poor outage performance, especially if the number of users is large. We propose to boost the outage performance of a NOMA-based VLC system by incorporating multi-user cooperative diversity over radio frequency (RF) links, thereby transforming it into a hybrid VLC-RF system. Such a system with cooperative NOMA (CoNOMA) has enhanced reliability compared to a conventional non-cooperative NOMA system. We formulate the expressions for the outage probability of the proposed system and analyze the outage performance for various power allocation schemes used in NOMA. We study the effects of increasing the number of users and the target data rate on the system’s overall outage performance. We also model the reliability of the multi-user CoNOMA system using Markov chains and evaluate the various reliability parameters for each user. We show that the outage performance and reliability of the VLC system are significantly enhanced by employing cooperative diversity using CoNOMA.

Two-Stage Adaptive Relay Selection and Power Allocation Strategy for Cooperative CR-NOMA Networks in Underlay Spectrum Sharing

In this paper, we consider a novel cooperative underlay cognitive radio network based on non-orthogonal multiple access (CR-NOMA) with adaptive relay selection and power allocation. In secondary networks, dedicated relay assistance and user assistance are used to achieve communication between the base station and the far (and near) user. Here, a two-stage adaptive relay selection and power allocation strategy is proposed to maximize the achievable data rate of the far user while ensuring the service quality of near user. Furthermore, the closed-form expressions of outage probability of two secondary users are derived, respectively, under interference power constraints, revealing the impact of transmit power, number of relays, interference threshold and target data rate on system outage probability. Numerical results and simulations validate the advantages of the established cooperation and show that the proposed adaptive relay selection and power allocation strategy has better outage performance.

Switching Signal Decoding Order in Uplink NOMA System With Imperfect SIC

The decoding order of successive interference cancelation (SIC) is a key issue in SIC implementation for non-orthogonal multiple access (NOMA) systems. This letter focuses on the dynamic SIC decoding order and proposes a switching SIC scheme, which dynamically determines the SIC order according to the ratio of the instantaneous received power to target data rate of each user. The outage performance is theoretically analyzed for our proposed scheme under the imperfect SIC conditions. Both the analysis and simulation demonstrate the effectiveness of our proposed scheme. It avoids searching possible SIC orders but achieves almost the same outage performance as the ideal exhaustive-search-SIC that considers all possible SIC orders to decode a signal.

An optimal energy harvesting scheme for simultaneous lightwave information and power transfer over multi-layer turbulence-induced underwater channel

In this paper, we propose an optimal and energy-efficient time-splitting based simultaneous light-wave information and power transfer for underwater optical wireless communications. We consider a multi-layer turbulence-induced underwater optical channel with each layer experiencing independent and non-identically distributed oceanic turbulence. A concave optimization problem to maximize the energy harvesting for a target data rate is formulated for two cases, that is, the deterministic and the stochastic energy harvesting rate. Specifically, the analytical expression of optimal time-splitting ratio is derived. Furthermore, it is shown that the value of time-splitting ratio less than 0.5 is preferred for an efficient performance. Simulation results validate the analysis and demonstrate that the proposed scheme significantly improves the data rate and the energy harvesting for underwater optical communications.

Analysis of the energy harvesting non-orthogonal multiple access technique for defense applications over Rayleigh fading channel conditions

The energy harvesting (EH) technique has ignited a rising research interest due to its ability to enhance the battery power of user equipment by harvesting energy by using a simple radio frequency circuit. In this paper, the simultaneous wireless information and power transfer non-orthogonal multiple access (NOMA) technique is investigated over Rayleigh fading channel conditions. EH NOMA improves the power efficiency, and it results in better throughput as compared to conventional NOMA techniques. In this paper, we investigate the achievable data rate and the outage probability performance of the near user, also called the relay user (RU), and the far user (FU). It can clearly be shown that the RU data rate is saturated and at 1 bits/s/Hz will become constant, while the FU data rate increases with an increase in transmitted power. It is seen by analysis that the RU data rate would saturate due to EH. It is further shown that with a transmitted power of 18 dBm, the net output of the FUs is readily shown to be based around a value of 2.80 bits/s/Hz. In comparison, it is shown that the FU’s instantaneous information rate dropped below the target data rate.

Performance Analysis and Beamforming Design of a Secure Cooperative MISO-NOMA Network.

This paper studies the cell-edge user’s performance of a secure multiple-input single-output non-orthogonal multiple-access (MISO-NOMA) system under the Rayleigh fading channel in the presence of an eavesdropper. We suppose a worst-case scenario that an eavesdropper has ideal user detection ability. In particular, we suggest an optimization-based beamforming scheme with MISO-NOMA to improve the security and outage probability of a cell-edge user while maintaining the quality of service of the near-user and degrading the performance of the eavesdropper. To this end, power allocation coefficients are adjusted with the help of target data rates of both the users by utilizing a simultaneous wireless information and power transfer with time switching/power splitting protocol, where the near-user is used to forward the information to cell-edge user. The analytical results demonstrate that our beamformer analysis can achieve reduced outage probability of cell-edge user in the presence of the eavesdropper. Moreover, the provided simulation results validate our theoretical analysis and show that our approach improves the overall performance of a two-user cooperative MISO-NOMA system.

Theoretical investigation of 120 Gb/s all-optical AND and OR logic gates using reflective semiconductor optical amplifiers

The performance of all-optical (AO) logic AND and OR gates, which are realized for the first time using reflective semiconductor optical amplifiers (RSOAs) as nonlinear elements, is theoretically investigated at 120 Gb / s. The switching modules that incorporate the RSOAs and exploit their potential for AO signal processing are the Mach–Zehnder interferometer and the delayed interferometer for the AND and OR operations, respectively. A performance comparison between an RSOA and a conventional semiconductor optical amplifier (SOA) is made by examining and assessing the quality factor against the operational critical parameters, including the effect of the amplified spontaneous emission. The obtained results confirm that these Boolean functions based on RSOAs can be executed at the target data rate with better performance than if conventional SOAs were used instead.

Reconfigurable Intelligent Surface Empowered Downlink Non-Orthogonal Multiple Access

Power-domain non-orthogonal multiple access (NOMA) has become a promising technology to exploit the new dimension of the power domain to enhance the spectral efficiency of wireless networks. However, most existing NOMA schemes rely on the strong assumption that users’ channel gains are quite different, which may be invalid in practice. To unleash the potential of power-domain NOMA, we propose a reconfigurable intelligent surface (RIS)-empowered NOMA scheme to introduce desirable channel gain differences among the users by adjusting the phase shifts at the RIS. Our goal is to minimize the total transmit power by jointly optimizing the beamforming vectors at the base station, the phase-shift matrix at the RIS, and user ordering. To address challenge due to the highly coupled optimization variables, we present an alternating optimization framework to decompose the non-convex bi-quadratically constrained quadratic problem under a specific user ordering into two rank-one constrained matrices optimization problems via matrix lifting. To accurately detect the feasibility of the non-convex rank-one constraints and improve performance by avoiding early stopping in the alternating optimization procedure, we equivalently represent the rank-one constraint as the difference between nuclear norm and spectral norm. A difference-of-convex (DC) algorithm is further developed to solve the resulting DC programs via successive convex relaxation, followed by establishing the convergence of the proposed DC-based alternating optimization method. We further propose an efficient user ordering scheme with closed-form expressions, considering both the channel conditions and users’ target data rates. Simulation results validate the ability of an RIS in enlarging the channel-gain difference when the users’ original channel conditions are similar and the superiority of the proposed DC-based alternating optimization method in reducing the total transmit power.

Performance Analysis for Downlink NOMA Over $\alpha$-$\mu$ Generalized Fading Channels

This work presents a performance analysis for downlink non-orthogonal multiple accesses (DL-NOMA) systems where the channel gains follow the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> fading distribution. Specifically, closed-form expressions are derived for DL-NOMA in terms of the outage probability (OP), bit error rate (BER), and ergodic capacity (EC). The OP analysis considers two main scenarios, the first is when the individual user's rate is required to satisfy a certain quality of service (QoS), while the second is when the individual user's NOMA rate is less than that of the conventional orthogonal multiple access (OMA) rate. Moreover, the derived BER performance is generalized for the case of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M$</tex-math></inline-formula> -ary quadrature amplitude modulation (MQAM). The results demonstrate the interplay between the system performance, the power allocation coefficients, target data rates, and the channel fading parameters. Moreover, the OP results reveal that NOMA users with OMA data rate experience higher outage compared to NOMA with fixed target data rate. The accuracy of the derived expressions is validated using extensive Monte Carlo simulation.

Joint User Pairing and Resource Allocation in a SWIPT-Enabled Cooperative NOMA System

This paper studies a novel design of user pairing and resource allocation in a simultaneous wireless information and power transfer (SWIPT)-enabled cooperative non-orthogonal multiple access (NOMA) system with coexisting power-splitting (PS) and time-switching (TS) users. In this system, near NOMA users (NUs) that are close to a source can assist the communications between the source and far NOMA users (FUs) using the energy harvested by either PS or TS strategy. The design aims to maximize the sum-rate of the system by optimizing user pairing and power allocation between NUs and FUs as well as performing PS and TS control at NUs, while guaranteeing the target data rates and the minimum harvested energy requirements of users. Since the joint design is formulated as a non-convex mixed-integer non-linear programming (MINLP) problem that is challenging to tackle, we propose a two-step user pairing and resource allocation algorithm. Specifically, we decouple the original problem into an inner resource allocation problem and an outer user pairing problem. For the inner problem, we propose successive convex approximation (SCA) and block coordinate descent (BCD)-based algorithms to perform power allocation as well as PS and TS control iteratively, with the algorithms’ convergence being theoretically proved. By exploiting the characteristics of the outer problem of user pairing, this problem is well tackled by the Hungarian algorithm. Simulation results demonstrate the proposed joint design yields better performance gains than the existing schemes.

Large Antenna Array with Hybrid Beamforming System for 5G Outdoor Mobile Broadband Communication Deployments

Millimeter wave (mmWave) communication requires large antenna arrays to increase the capability of cellular networks of the fifth generation with good beam-forming gains and a substantial reduction in path losses for both transmitting and receiving terminals. As large antenna arrays require one radio frequency chain per antenna element, the fully digital beamforming technique results in high cost and high-power consumption, and it is therefore not feasible. However, in analog solutions, adaptive gain control cannot be used as it reduces the likelihood of advanced processing and contributes to poor efficiency. Hybrid schemes are possible exciting solutions that overcome the deficiencies of pure digital or analog beam forming. The following are the three key contributions of the proposed work: a typical link budget specification for target data rate 3.10 Gbps in downlink and 0.6 Gbps in uplink is provided, micro strip patch antenna with a single element is designed to operate at 28 GHz and then converted into a standard linear array and a Kalman-based hybrid analog/digital precoding is used with a downlink rate of 4.64 Gbps/cell and an uplink rate of 1.84 Gbps/cell in multi-user environments. And the influence of both base station (BS) and 5G User equipment (UEs) beam steering capability is also explored. From the simulation result, it is evident that the proposed work offers a substantial increase in spectral efficiency approximately 9.28 bps/Hz at 20 dB with 10 channel paths.

Optimized Precoders for Massive MIMO OFDM Dual Radar-Communication Systems

This paper considers the optimization of a dual-functional radar and communication (RadCom) system with the objective is to maximize its sum-rate (SR) and energy-efficiency (EE) while satisfying certain radar target detection and data rate per user requirements. To this end, novel RadCom precoder schemes that can exploit downlink radar interference are devised for massive multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. First, the communication capacity and radar detection performance metrics of these schemes are analytically evaluated. Then, using the derived results, optimum beam power allocation schemes are deduced to maximize SR and EE with modest computational complexity. The validity of the analytical results is confirmed via matching computer simulations. It is also shown that, compared to benchmark techniques, the devised precoders can achieve substantial improvements in terms of both SR and EE.

Impact of Residual Hardware Impairment on the IoT Secrecy Performance of RIS-Assisted NOMA Networks

Non-orthogonal multiple access (NOMA) technology is expected to effectively improve the spectrum efficiency of fifth-generation and later wireless networks. As a new technology, reconfigurable Intelligent surfaces (RIS) can achieve high spectral and energy efficiency with a low cost in wireless networks. These are achieved by integrating a great quantity of low-cost passive reflective units (RUs) on the plane. In this article, in order to meet the needs of high efficiency, low power consumption, and wide coverage, we combine RIS-assisted NOMA technology with the internet of things (IoT). Because in the actual wireless communication system, the residual hardware impairment (RHI) characteristics of the actual transceiver equipment will have an important impact on system secrecy performance. Therefore, the study will propose a single eavesdropper RIS-assisted downlink NOMA system with RHI (E-RHI-RIS-NOMA). The study will also investigate the impact of RHI on the physical layer security (PLS) performance of the system and the closed-form expression of the user's secrecy outage probability (SOP) is derived. Finally, the simulation results show that 1) the main factors affecting the SOP are the quantity of RUs in RIS, the transmit SNR, and the target data rate, 2) it is proved that the hardware impairment of the transceiver harms the system's secrecy outage performance while the severity of the impact of RHI on the system performance depends on the transmit SNR and target data rate. Moreover, RHI at different nodes has a different influence on system secrecy performance. 3) the system performance of RIS relying on NOMA is improved compared with orthogonal multiple access (OMA) and conventional NOMA.

Outage Performance of Downlink NOMA With Network-Coded Interference Cancellation

In this paper, we study a downlink non-orthogonal multiple access (NOMA) transmission system, where a novel network-coded interference cancellation (NCIC) scheme is proposed to promote the outage performance. In order to further improve the outage performance, an adaptive NCIC (A-NCIC) scheme is also studied, which dynamically switches between successive interference cancellation (SIC) and the proposed NCIC schemes according to the power allocation factors and target data rates. The expressions of the outage probability are derived to evaluate the performance of the proposed scheme. The simulation results demonstrate the remarkable performance of the proposed NCIC scheme over the conventional SIC-based NOMA on the outage probability.

Coverage Evaluation for 5G Reduced Capability New Radio (NR-RedCap)

The fifth-generation (5G) wireless technology is primarily designed to address a wide range of use cases categorized into the enhanced mobile broadband (eMBB), ultra-reliable and low latency communication (URLLC), and massive machine-type communication (mMTC). Nevertheless, there are a few other use cases that are in-between these main use cases such as industrial wireless sensor networks, video surveillance, or wearables. In order to efficiently serve such use cases, in Release 17, the 3rd generation partnership project (3GPP) introduced the reduced capability NR devices (NR-RedCap) with lower cost and complexity, smaller form factor, and longer battery life compared to regular NR devices. However, one key potential consequence of device cost and complexity reduction is coverage loss. In this paper, we provide a comprehensive evaluation of NR RedCap coverage for different physical channels and initial access messages to identify the channels/messages that are potentially coverage limiting for RedCap UEs. We perform the coverage evaluations for RedCap UEs operating in three different scenarios, namely Rural, Urban and Indoor with carrier frequencies 0.7 GHz, 2.6 GHz and 28 GHz, respectively. Our results confirm that for all the considered scenarios, the amounts of required coverage recovery for RedCap channels are either less than 1 dB or can be compensated by considering smaller data rate targets for RedCap use cases.

A 32 Gb/s PAM-16 TX and ADC-Based RX AFE with 2-tap embedded analog FFE in 28 nm FDSOI

This paper presents a 32 Gb/s 16-level pulse amplitude modulation (PAM-16) source-series-terminated transmitter (TX) and a receiver (RX) analog front-end (AFE) in 28 nm FDSOI. The 8-way time-interleaved successive-approximation register (SAR) analog-to-digital-converter (ADC) in the RX AFE has an embedded 2-tap analog feed-forward equalizer. The design objective is to optimize the energy efficiency for the target data rate and the moderate-loss channel. For this purpose, the optimum modulation order that has the least ISI sensitivity for the given equalization capability is decided with a modeling study. All the equalization is performed in the analog domain to avoid the circuit complexity and power consumption disadvantages of the digital equalization in the selected high-order modulation. Thanks to the spectral efficiency of PAM-16 and the analog-only equalization, the figure-of-merit is improved significantly. Post-layout simulations show that the TX consumes 26.85 mW while the RX AFE consumes 49.36 mW at 32 Gb/s with PAM-16, which corresponds to 2.38 pJ/bit for the whole system.

Radio Resource Dimensioning for Low Delay Access in Licensed OFDMA IoT Networks.

In this paper, we focus on the radio resource planning in the uplink of licensed Orthogonal Frequency Division Multiple Access (OFDMA) based Internet of Things (IoT) networks. The average behavior of the network is considered by assuming that active sensors and collectors are distributed according to independent random Poisson Point Process (PPP) marked by channel randomness. Our objective is to statistically determine the optimal total number of Radio Resources (RRs) required for a typical cell. On one hand, the allocated bandwidth should be sufficiently large to support the traffic of the devices and to guarantee a low access delay. On the other hand, the over-dimensioning is costly from an operator point of view and induces spectrum wastage. For this sake, we propose statistical tools derived from stochastic geometry to evaluate, adjust and adapt the allocated bandwidth according to the network parameters, namely the required Quality of Service (QoS) in terms of rate and access delay, the density of the active sensors, the collector intensities, the antenna configurations and the transmission modes. The optimal total number of RRs required for a typical cell is then calculated by jointly considering the constraints of low access delay, limited power per RR, target data rate and network outage probability. Different types of networks are considered including Single Input Single Output (SISO) systems, Single Input Multiple Output (SIMO) systems using antenna selection or Maximum Ratio Combiner (MRC), and Multiuser Multiple Input Multiple Output (MU-MIMO) systems using Zero-Forcing decoder.

Secrecy Outage Probability of Energy-Harvesting Cooperative NOMA Transmissions With Relay Selection

Three relay selection techniques, aiming at achieving secure non-orthogonal multiple access in cooperative energy-harvesting (EH) communications, are proposed and compared. In the cooperative relaying system, the source node communicates with multiple users through amplify-and-forward EH relays in the presence of a passive eavesdropper. The relay selection is a two-stage strategy, where the first stage aims at achieving the users’ target data rate, and the second aims at optimizing the secrecy outage probability. New explicit analytical expressions for the secrecy outage probability are derived for three operating scenarios: i) when the channel state information (CSI) of the eavesdropper is unknown, and a two-stage conventional relay selection scheme is considered, ii) when CSI of the eavesdropper is known, and a two-stage optimal relay selection scheme is used, and iii) when multiple relays participate in forwarding the signal to the end users. Monte-Carlo simulations are provided to confirm the derivations, and the effects of the main system parameters on its secrecy are investigated. In particular, it is shown that the optimal relay selection scheme outperforms the conventional and the multiple-relays schemes in terms of secrecy outage probability, and that this superiority becomes more obvious when the number of the relays increases.