Adaptive Power Allocation Scheme Research Articles

Adaptive power allocation strategy for hybrid energy storage system based on driving pattern recognition

The power allocation strategy of hybrid energy storage systems plays a decisive role in energy management for electric vehicles. However, existing online real-time power allocation strategies primarily rely on expert knowledge to make rules. Due to the real time changes in driving patterns, it is necessary for the power allocation strategy to possess adaptive capabilities to ensure optimal energy efficiency. Therefore, an adaptive power allocation strategy is proposed in this paper, which takes into account the driving patterns of electric vehicles. Firstly, driving pattern recognition is performed using the K-means clustering method to extract features of driving profiles. Then, the fuzzy logic control strategy is adopted to make the rules of filter frequency, and the rules is adaptive adjusted based on the results of driving pattern recognition. To achieve smoother power output from lithium-ion batteries and prolong their lifespan, the digital low pass filter is used to accomplish the fuzzy logic control strategy, and the filtering frequency is online optimized by the above fuzzy controller. According to the digital low pass filter, the load power demand is decomposed high-frequency component and low-frequency component. The decomposed high-frequency component of power demand is supplied by supercapacitors, while the low-frequency component is provided by lithium-ion batteries. To validate the effectiveness of the proposed method, comparative experiments are conducted between the proposed strategy and another four strategies. The experimental results demonstrate that the proposed strategy can effectively smooth the power output of lithium-ion batteries and reduce total energy losses.

A bi‐level planning strategy of a hydrogen‐supercapacitor hybrid energy storage system based on APA‐MOHHO

AbstractA bi‐level planning strategy of a hydrogen‐supercapacitor hybrid energy storage system (H‐S HESS) has been proposed in this study for wind power fluctuation suppression. The proposed system consists of a supercapacitor array and a hydrogen energy storage unit, and the bi‐level planning strategy consists of an Energy Management Level and a Capacity Configuration Level. In the upper level, with Hilbert–Huang transform frequency analysis, a novel energy management strategy based on adaptive power allocation (APA) is designed. The lower level applies multi‐objective Harris hawks optimizer to solve the optimal parameters of each device in the system. Based on the data measured from a 2‐MW wind system in a hydrogen‐electric coupled DC microgrid demonstration project, the optimal system capacity configuration scheme is obtained. The annualized cost of the system is $150,212, which is 41.1% lower than the scheme without optimization. The fluctuation unsuppressed rate of H‐S HESS is 0.64% under the APA strategy, which is only 0.14% higher than the conventional HESS (supercapacitor + lithium‐ion batteries) with the same annualized cost of system. The proposed strategy reduces the frequency of HESS operational power fluctuations, improves capacity configuration accuracy, and significantly decreases the cost gap between the proposed H‐S HESS and conventional structures.

Reliability performance analysis for OTFS modulation based integrated sensing and communication

In this paper, we develop an orthogonal time frequency space (OTFS) modulation based integrated (radar) sensing and communication (ISAC) technique, namely OTFS-ISAC, for the high mobility multiuser system. In particular, at the transmitter, it can alternate the modes between sensing and communication using time division multiplexing so that it takes advantage of radar assistance to design the OTFS frame structure for reducing the overhead of guard symbols. At the receiver, based on the embedded pilot-aided channel estimation, it employs zero-forcing (ZF) equalization. For performance analysis, we derive the error probability of channel estimation based on radar sensing, and find the outage probability of downlink communication. Then, we introduce an adaptive power allocation scheme at the transmitter to optimize the outage probability of the communication link. Our simulations show that, by properly selecting N, M, and the pilot symbol strength, the proposed OTFS-ISAC scheme can reduce the overhead of guard symbols while achieving promising reliability performance of the downlink transmission with relative low channel estimation error.

An Optimal Distributed Energy-Efficient Resource Scheduling for D2D-U Enabled Cellular Networks

Rational sharing of unlicensed spectrum and efficient use of device-to-device (D2D) communication are two effective ways to improve energy efficiency (EE) and spectrum efficiency (SE) in 5G new radio system. In this paper, we extend the D2D technology to unlicensed spectrum and study the EE of user terminals in unlicensed D2D (D2D-U) system. To cope with the inherent distributed structure of the D2D-U enabled networks and the time-varying wireless fading channels, a distributed adaptive joint power and spectrum allocation scheme is proposed based on the differentiated projection method to maximize the EE of user terminals. The theoretic analysis and numerical results are provided to validate the performance of the proposed scheme, which not only significantly reduces the signaling overhead, but also achieves the global optimality as the centralized scheme.

Proactive Eavesdropping Over Multiple Suspicious Communication Links With Heterogeneous Services

To legitimately eavesdrop communications of suspicious users such as criminals, proactive eavesdropping has been proposed as an effective approach. Current works considered that suspicious communication links (SCLs) carry homogeneous services, which is unrealistic due to randomness of user behaviors. Thus, this paper investigates proactive eavesdropping over multiple SCLs with heterogeneous services. The relative eavesdropping non-outage probability and the relative eavesdropping rate are adopted as eavesdropping utilities for delay-sensitive (DS) and delay-tolerant (DT) suspicious services, respectively. The jamming power allocation problem to maximize the weighted sum eavesdropping utility under the average transmit power constraint at the monitor is investigated under the non-adaptive fixed power allocation and the adaptive power allocation schemes adopted by the SCLs. The problem belongs to sum-of-ratios optimization and is transformed to an equivalent parameterized subtractive-form with some extra auxiliary variables. Two nested optimizations are proposed to solve the equivalent problem based on the Lagrange duality method and the damped Newton method. Simulation results demonstrate the superiority of the proposed algorithms compared to various benchmark algorithms in existing literature. It is shown that the impacts of the power allocation schemes of the SCLs on the eavesdropping performance may be different for the DS and DT suspicious services under different system setups.

Outage performance for full-duplex relaying satellite-terrestrial multi-antenna NOMA systems with imperfect SIC

Due to the masking effect, a reliable line-of-sight transmission between a satellite and terrestrial nodes is not always guaranteed, and a half-duplex (HD) relaying is commonly performed in literature to assist such transmission. However, the system efficiency could be seriously degraded with the HD relaying as a two-time slot is required for a dual-hop information transmission. Therefore, in this paper, a full-duplex (FD) relaying, which can enable signal receiving and transmitting simultaneously, is considered for a satellite-terrestrial non-orthogonal multiple access (NOMA) system consisting of a multi-antenna satellite source, a FD relay, and two multi-antenna destination nodes. Specifically, the satellite source adopts a maximum ratio transmission scheme to transmit a NOMA signal to the relay, and the relay deploys a decode-and-forward protocol to forward the information to two destination nodes simultaneously, which employ the maximal ratio combining strategy to process the received signals. Assuming the satellite link experiences Shadowed-Rician fading and the terrestrial links undergo Nakagami-m fading distribution, both analytical and asymptotic expressions of outage probability (OP) for two destination nodes are presented in the presence of residual self-interference and imperfect successive interference cancellation. In addition, an adaptive power allocation (APA) scheme is performed, and the system throughput under the delay-limited transmission mode is also analyzed. Finally, Monte-Carlo simulations are adopted to verify the accuracy of those derived analytical expressions. Numerical results show that the OP performance with the FD mode outperforms that with the HD one, and adopting the APA scheme can result in the best OP performance.

Adaptive optimal power allocation scheme based on intelligent user association for NOMA-VLC systems

In this paper, the joint problem of user association and power allocation for non-orthogonal multiple access (NOMA)-visible light communication (VLC) systems is investigated. First, a novel intelligent user association (UA) method for multi-user NOMA-VLC is proposed to improve the multiplexing efficiency. Second, a new adaptive optimal power allocation scheme based on the UA method is presented and three corresponding mathematical optimization problems are established, aiming to optimize the system throughput while each user's illumination requirement, quality of service demand, eye safety, and transmission power limit are satisfied simultaneously. Third, for the error propagation at the NOMA receiver, the perfect and imperfect interference cancellations are considered in the established power allocation models. Finally, the numerical results demonstrate the superiority of the proposed scheme on the VLC network capacity under perfect and imperfect interference cancellation. Furthermore, it is also found that the proposed scheme could achieve higher system throughput by modifying users' field-of-views (FOVs).

Double adaptive power allocation strategy in electric vehicles with battery/supercapacitor hybrid energy storage system

This paper proposes a new energy management strategy (EMS) for electric vehicles (EVs) with battery/supercapacitor hybrid energy storage systems (HESS). Firstly, the battery/supercapacitor HESS configuration and obtaining the load current from the driving cycle are comprehensively explained. Secondly, fixed and adaptive frequency-based (AFB) EMS are discussed in detail. In the proposed method, the current demanded by the load is separated into low and high-frequency components with the help of an adaptive low-pass filter (A-LPF). In addition, adaptive battery current (ABC) is generated according to the supercapacitor (SC) state of charge (SoC), and a double adaptive power allocation strategy is performed. The proposed method is compared with the AFB-EMS for load currents, load powers, DC link voltages, filter cut-off frequencies, battery, and SC SoCs on the UDDS driving cycle. When the obtained results were evaluated together, it was observed that the proposed method completed the driving cycle with a higher battery SoC and realized the adaptive cut-off frequency in a narrower band.

Age of Information in Energy Harvesting Aided Massive Multiple Access Networks

Given the proliferation of the massive machine type communication devices (MTCDs) in beyond 5G (B5G) wireless networks, energy harvesting (EH) aided next generation multiple access (NGMA) systems have drawn substantial attention in the context of energy-efficient data sensing and transmission. However, without adaptive time slot (TS) and power allocation schemes, NGMA systems relying on stochastic sampling instants might lead to tardy actions associated both with high age of information (AoI) as well as high power consumption. For mitigating the energy consumption, we exploit a pair of sleep-scheduling policies, namely the multiple vacation (MV) policy and start-up threshold (ST) policy, which are characterized in the context of three typical multiple access protocols, including time-division multiple access (TDMA), frequency-division multiple access (FDMA) and non-orthogonal multiple access (NOMA). Furthermore, we derive closed-form expressions for the MTCD system’s peak AoI, which are formulated as the optimization objective under the constraints of EH power, status update rate and stability conditions. An exact linear search based algorithm is proposed for finding the optimal solution by fixing the status update rate. As a design alternative, a low complexity concave-convex procedure (CCP) is also formulated for finding a near-optimal solution relying on the original problem’s transformation into a form represented by the difference of two convex problems. Our simulation results show that the proposed algorithms are beneficial in terms of yielding a lower peak AoI at a low power consumption in the context of the multiple access protocols considered.

Secure Multiantenna Transmission With an Unknown Eavesdropper: Power Allocation and Secrecy Outage Analysis

This paper investigates the power allocation problem for secure multiple-input single-output transmission with the injection of artificial noise (AN), in the presence of an unknown eavesdropper (Eve). Two power allocation schemes, the optimal adaptive power allocation (OAPA) and suboptimal fixed power allocation (SFPA) schemes, are proposed to enhance the physical layer security of the considered system. Since the noise power at Eve is unknown, both power allocation schemes are designed for the worst-case scenario in which the noise power at Eve is assumed to be zero, aiming to minimize the secrecy outage probability (SOP). To characterize the performance of the proposed power allocation schemes, approximate closed-form expressions for average SOP under a preset noise power level are derived by applying Gauss-Chebyshev quadrature. We also address the worst-case secrecy outage performance for the proposed OAPA and SFPA schemes. Our analytical and numerical results show that, compared with the exhaustive search method that requires Eve’s prior information, the proposed OAPA scheme exhibits comparable secrecy outage performance without Eve’s prior information. Additionally, the SFPA scheme, also without Eve’s prior information, is capable of achieving almost the same worst-case SOP as the OAPA scheme, with a much lower implementation complexity.

Coded-Caching Using Adaptive Transmission

In this letter, we study the effect of adaptive transmission on the performance of coded-caching based networks. Particularly, concentrating on the reduction of backhaul peak load during the high traffic periods, we develop adaptive rate and power allocation schemes maximizing the network successful transmission probability, which is defined as the average probability that the cache nodes decode their intended signals correctly. Moreover, we study the effect of different message decoding and buffering schemes on the system performance. As we show, the performance of coded-caching networks is considerably affected by rate/power allocation as well as the message decoding/buffering schemes.

Dual-Polarized IRSs in Uplink MIMO-NOMA Networks: An Interference Mitigation Approach

In this work, intelligent reflecting surfaces (IRSs) are optimized to manipulate signal polarization and improve the uplink performance of a dual-polarized multiple-input multiple-output (MIMO) non-orthogonal multiple access (NOMA) network. By multiplexing subsets of users in the polarization domain, we propose a strategy for reducing the interference load observed in the successive interference cancelation (SIC) process. To this end, dual-polarized IRSs are programmed to mitigate interference impinging at the base station (BS) in unsigned polarizations, in which the optimal set of reflecting coefficients are obtained via conditional gradient method. We also develop an adaptive power allocation strategy to guarantee rate fairness within each subset, in which the optimal power coefficients are obtained via a low-complexity alternate approach. Our results show that all users can reach high data rates with the proposed scheme, substantially outperforming conventional systems.

Adaptive Beamforming and Power Allocation for mmWave Communication in High‐Speed Railway

AbstractMillimeter wave (mmWave)‐based massive multiple‐input multiple‐output (MIMO) beamforming technology is one of the key technologies in the fifth‐generation (5G) network. In this paper, we apply mmWave to high‐speed railway (HSR) communication scenario to meet its increasingly growing demands for tremendous data rate and reliable mobile services. The HSR mmWave communication system uses a control/user (C/U) plane separation structure; that is, control information and user information are transmitted through the high‐frequency micro base station (BS) and the low‐frequency macro BS, respectively. Then, an optimized beam width and power allocation scheme is proposed, which is combined with the mobile relay (MR) technology to utilize the architecture of the large‐scale antenna beamforming. In the proposed scheme, we introduce a power factor related to the change of train speed. According to the power factor, the service beam width is adjusted dynamically and the transmit power of the beams from two simultaneously served mmWave access points (APs) is jointly calculated. Simulation results show that, compared with the traditional uniform beam width scheme, the proposed adaptive beam width and power allocation scheme can maximize the total service volume within the maximum transmit power range.

Enhancing physical layer security via a UAV friendly jammer for NOMA‐based IoT systems with imperfect CSI

AbstractIn this article, we investigate physical layer security in downlink Internet of Things networks under imperfect channel state information (CSI), in which a controller (Alice) intends to serve two user devices (D1 and D2) simultaneously by using nonorthogonal multiple access (NOMA). Cooperative jamming (CJ) is introduced as a powerful solution for guaranteeing secure transmission. To be specific, we integrate an unmanned aerial vehicle (UAV) jammer that generates artificial noise to confuse multiple noncolluding eavesdroppers (Eves). Considering only D1 requires secure transmission, we develop an adaptive power allocation scheme to maximize the secrecy rate at D1 while meeting the desired quality of service (QoS) threshold at D2. Furthermore, a strategy can be utilized to obtain the optimal location of the UAV jammer is derived for further performance enhancement. Besides, we also examine the impact of the channel uncertainties on system performance. Numerical results are provided to confirm the superiority and applicability of the proposed CJ scheme over benchmark schemes in terms of secrecy performance and effective energy efficiency.

Power Allocation and Outage Analysis for Secure MISO Cognitive Radio Networks With an Unknown Eavesdropper

This paper investigates the power allocation problem for secure secondary transmission in a multiple-input single-output cognitive wiretap system with artificial noise (AN). The secondary transmitter exchanges confidential information with the secondary destination in the presence of an unknown eavesdropper. Since the eavesdropper's channel state information (CSI) is unavailable, we propose an optimal adaptive power allocation scheme, and derive a closed-form expression of the optimal power allocation factor that minimizes the secrecy outage probability (SOP). A suboptimal fixed power allocation scheme is also proposed to reduce the system complexity. Moreover, exact closed-form expressions of SOP under both schemes are derived. Numerical results are provided to corroborate the accuracy of our analytical results and the superiority of the proposed schemes to the benchmarks.

Power Adaptation for Improving the Performance of Time Switching SWIPT-Based Full-Duplex Cooperative NOMA Network

This letter investigates an adaptive power allocation (APA) scheme for the simultaneous wireless information and power transfer (SWIPT) enabled full duplex (FD) cooperative non-orthogonal multiple access (NOMA) network under time switching (TS) protocol. The proposed APA involves the joint design of power allocation coefficient at the base station and the TS factor at the relay. We derive expressions for the outage probabilities (OP) experienced by the downlink users under APA as well as fixed power allocation (FPA) strategies, considering imperfect successive interference cancellation. By providing the asymptotic OP analysis, we establish that the proposed APA scheme: (i) resolves the zero diversity order problem inherent in FD-NOMA systems under FPA and (ii) significantly improves outage and throughput performance of SWIPT enabled FD-NOMA systems.

Outage Constrained Power Efficient Design for Downlink NOMA Systems With Partial HARQ

In this paper, we aim to design an adaptive power allocation scheme to minimize the average transmit power of a hybrid automatic repeat request with chase combining (HARQ-CC) enabled non-orthogonal multiple access (NOMA) system under strict outage constraints of users. Specifically, we assume that the base station only knows the statistical channel state information of the users. To achieve power efficient design and cope with the reliable transmissions of users, a partial HARQ-CC scheme is proposed. We first focus on the two-user case. To evaluate the performance of the two-user partial HARQ-CC enabled NOMA system, we first analyze the outage probability of each user. Then, an average power minimization problem is formulated. However, the attained expressions of the outage probabilities are nonconvex, and thus make the problem challenging to solve. Hence, we propose to use a successive convex approximation (SCA) based algorithm to solve the problem iteratively. Meanwhile, we prove that the proposed algorithm can converge to a Karush–Kuhn–Tucker point of the original problem. For more practical applications, we also investigate the partial HARQ-CC enabled transmissions in the multi-user scenario. The user pairing and power allocation problem is considered. With the aid of matching theory, a low complexity algorithm is presented to first handle the user pairing problem. Then the power allocation problem for each user pair is solved by the proposed SCA-based algorithm. Simulation results show the efficiency of the proposed transmission strategy and the near-optimality of the proposed algorithms.

Cooperative Secure Transmission in MISO-NOMA Networks

In this paper, we investigate cooperative secure transmission in non-orthogonal multiple access (NOMA) networks where a source (Alice) intends to transmit confidential messages to one legitimate user with high-level security requirement (LU1), and serve another normal one (LU2) simultaneously. In order to enhance the transmission security, a cooperative jammer (Charlie) is employed to confuse multiple non-colluding eavesdroppers (Eves). Taking both secrecy outage restriction of LU1 and the desired quality of service (QoS) requirement of LU2 into consideration, we propose an adaptive power allocation strategy for maximizing secrecy rate. Numerical results are provided to validate that our proposed scheme significantly outperforms the conventional NOMA secure transmission scheme.

Joint Adaptive Sampling Interval and Power Allocation for Maneuvering Target Tracking in a Multiple Opportunistic Array Radar System.

In this paper, a joint adaptive sampling interval and power allocation (JASIPA) scheme based on chance-constraint programming (CCP) is proposed for maneuvering target tracking (MTT) in a multiple opportunistic array radar (OAR) system. In order to conveniently predict the maneuvering target state of the next sampling instant, the best-fitting Gaussian (BFG) approximation is introduced and used to replace the multimodal prior target probability density function (PDF) at each time step. Since the mean and covariance of the BFG approximation can be computed by a recursive formula, we can utilize an existing Riccati-like recursion to accomplish effective resource allocation. The prior Cramér-Rao lower boundary (prior CRLB-like) is compared with the upper boundary of the desired tracking error range to determine the adaptive sampling interval, and the Bayesian CRLB-like (BCRLB-like) gives a criterion used for measuring power allocation. In addition, considering the randomness of target radar cross section (RCS), we adopt the CCP to package the deterministic resource management model, which minimizes the total transmitted power by effective resource allocation. Lastly, the stochastic simulation is embedded into a genetic algorithm (GA) to produce a hybrid intelligent optimization algorithm (HIOA) to solve the CCP optimization problem. Simulation results show that the global performance of the radar system can be improved effectively by the resource allocation scheme.

Optimized Antenna Selection and Adaptive Power Allocation for Physical Layer Network Coding with Selective Soft-Message-Forward Cooperation

To improve the systematic bit error rate (BER) performance and power efficiency, an optimized antenna selection and adaptive power allocation scheme is proposed for physical layer network coding (PNC) with selective soft-message-forward (SSMF) cooperation. In this scheme, two adaptive power allocation (APA) schemes are proposed for the multiple access (MA) and broadcast (BC) stages, respectively. In the MA stage, the APA scheme aims to maximize the Euclidean distance of network coding symbols received by relay node. In the second BC stage, the relay node takes the maximization of the minimum mutual information of two source nodes as objective function. Then it uses the narrow range method (NRM) to select the optimal antenna set and equally allocates power to them. To further reduce the systematic complexity, an antenna set pre-selection is proposed. It minimizes the antenna number in the initial antenna set of the NRM based on the deletion standard which does not reduce the mutual information in the BC stage. Simulation results indicate that our APA schemes surpass the existing equal power allocation (EPA) scheme with a binary phase-shift keying modulation. Compared with current EPA scheme, the proposed APA schemes for the BC, MA and global stages obtain about 1 dB, 2 dB and 3.5 dB performance gains at BER of 10−3 with two antennas in the relay node, respectively.