In this paper, we propose an optimal time and powerallocation scheme in a wireless power supply full-duplex (FD) relay system, where we consider the number of relay antennas in the energy harvesting stage. At the sam...
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In this paper, we propose an optimal time and powerallocation scheme in a wireless power supply full-duplex (FD) relay system, where we consider the number of relay antennas in the energy harvesting stage. At the same time, the energy efficiency optimization problem of the system is structured, where optimization issues related to time allocation factors and powerallocation are established. For the FD dual-antenna and the FD single-antenna energy harvesting system, energy efficiency function is proven to be a concave function over the time-switch factor, and the optimal time-switching factor is theoretically obtained using the Lambert function. Then, according to the given value range of the optimal time switching factor, the optimal power distribution scheme is obtained by analyzing the derivative function of the system energy efficiency and using the properties of the Lambert function. The time-switching factor and transmission power are optimally selected at the wireless power supply FD relay. Results reveal that the performance of energy efficiency of the dual-antenna energy harvesting at the FD relay outperforms that of the single-antenna. Moreover, our results demonstrate that FD relay systems always substantially boost the energy efficiency compared with half-duplex (HD) relay systems.
OFDM technology will become the key technique in broadband wireless communication system in future due to its advantages in suppressing effectively the fading channels and of high rate of spectrum usage efficiency. Th...
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OFDM technology will become the key technique in broadband wireless communication system in future due to its advantages in suppressing effectively the fading channels and of high rate of spectrum usage efficiency. The adaptive modulation technology in OFDM system can choose proper modulation methods and signal power for every sub-channel, which improves greatly the system performance. To study on the adaptive modulation technology in OFDM system is significant for the development and applications of the broadband wireless communication system in the future. This essay proposes an adaptive modulation technology suitable for the OFDM system with fixed rate. The algorithm combines the sub-band division with the greedy allocationalgorithm to simplify the algorithm complexity. Through gathering the adjacent sub-channels together and allocating the same number of bits to them, the signaling overhead in practical application can be reduced effectively. Through choosing different sub-band width, the complexity of the algorithm can be adjusted flexibly. And good compromise can be made between the algorithm complexity and the performance. Compared to the existing molecular band adaptive allocationalgorithm, in the condition of the same performance, new algorithm has lower complexity. The new algorithm proposed in this essay has high application flexibility and is suitable for practical applications.
Non-orthogonal multiple access (NOMA) is a promising multiple access scheme to enhance the spectrum efficiency of fifth generation networks. In this study, the authors study a downlink multiple-input single-output (MI...
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Non-orthogonal multiple access (NOMA) is a promising multiple access scheme to enhance the spectrum efficiency of fifth generation networks. In this study, the authors study a downlink multiple-input single-output (MISO) system combined with NOMA, where a single beamforming (BF) vector is shared by a group of users. A joint BF and power allocation algorithm is proposed to maximise the sum rate of the users with better channel conditions while guaranteeing the quality of service at the user with poor channel conditions. The formulated problem for sum rate maximisation can be shown as non-deterministic Polynomial-time-hard, and therefore an effective solution based on branch and bound (BB) techniques is proposed. Numerical results are provided to verify that the proposed NOMA-BF system with the BB algorithm improves the sum capacity significantly compared with the NOMA-BF system with zero forcing.
This paper presents a new structure of multicopter with its propellers installed in three different *** aim is to achieve complete independent control of position and attitude of the *** can allow us to control the po...
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ISBN:
(纸本)9781538629185
This paper presents a new structure of multicopter with its propellers installed in three different *** aim is to achieve complete independent control of position and attitude of the *** can allow us to control the position with its desired attitude controlled *** such,this new multicopter can hover at any fixed point with its attitude changed *** can not be achieved for the existing *** key feature of this new design is that it provides the practical engineering area with a revelation,i.e.,it is actually not necessary to install robots on the aircraft to accomplish the planned aerial mission because this new multicopter is essentially a six degree-of-freedom aerial *** this novel design,the dynamic model is further established by using the Newton-Euler *** the basis of this,the work of controller design is also carried *** motion feature which the general multicopter can not be achieved is finally verified by numerical simulation.
This work develops a novel framework to analyse the outage probability of narrowband signal transmissions between arbitrary shaped spatial regions. Since the sampling of the spatial regions populated with antennas is ...
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ISBN:
(纸本)9781509009411
This work develops a novel framework to analyse the outage probability of narrowband signal transmissions between arbitrary shaped spatial regions. Since the sampling of the spatial regions populated with antennas is a form of mode excitation, we consider communication between the regions in terms of orthonormal basis functions encoded in wave modes to describe the outgoing/incoming signals in the transmit/receive region. Based on this framework, we first show that analogous to MIMO system, the mutual information (MI) over Rayleigh fading channel for narrowband communication between spatial regions is equivalent to a Gaussian random variable. We then derive an accurate closed-from expression of the outage probability using the definition of MI. In addition, we propose a descending transmit power allocation algorithm. Simulation results indicate that the proposed algorithm outperforms the conventional equal powerallocation scheme even at low SNR (signal to noise ratio) regime.
In this study, the authors propose a continuous rate and power allocation algorithm for multiuser downlink multiple-input-multiple-output orthogonal frequency-division multiplexing systems with coordinated multi-point...
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In this study, the authors propose a continuous rate and power allocation algorithm for multiuser downlink multiple-input-multiple-output orthogonal frequency-division multiplexing systems with coordinated multi-point transmission. The optimisation problem is formulated as a weighted sum-rate maximisation problem subject to per-antenna power constraints across multiple cooperating base stations (BSs). The practical consideration of the per-antenna power constraint limits the average transmit antenna power which indirectly controls the inherent issue of high peak powers in OFDM. The proposed algorithm employs a successive convex approximation (SCA) technique to dynamically allocate powers to multiple co-channel user terminals. They provide a convexity proof of the transformed optimisation problem and they show that the proposed algorithm converges to a unique solution. They compare the proposed SCA algorithm with two alternative approaches: (i) iterative waterfilling (IWF) and (ii) zero-forcing beamforming (ZFB) with semi-orthogonal user selection under both per-antenna and per-BS power constraint scenarios. Their simulation results highlight that the proposed SCA algorithm outperforms the existing IWF and ZFB in noise-limited environments under both power constraint scenarios.
Water-Filling (WF) is widely applied in powerallocation in multichannel wireless communications. By mathematically linearising the optimal WF expression, the authors observe an intrinsic parallel-shift property of WF...
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Water-Filling (WF) is widely applied in powerallocation in multichannel wireless communications. By mathematically linearising the optimal WF expression, the authors observe an intrinsic parallel-shift property of WF, based on which a fast and efficient WF algorithm is proposed. Compared with the conventional WF algorithms, it greatly simplifies WF execution by removing the Lagrange multiplier (or water-level) searching process. The authors further apply the proposed parallel-shift WF to solve the powerallocation problem in orthogonal frequency division multiplexing (OFDM)-based underlay cognitive radios (CRs), with the objective of maximising the secondary user's throughput over all OFDM sub-channels under the transmit power and the interference constraints. To this end, the existing algorithm adopts an iterative binary searching process to find the solution, where the conventional WF algorithm with Lagrange multiplier searching is invoked in each iteration. In contrast, the authors propose a new power allocation algorithm to remove the iterative binary searching process. It runs the simplified parallel-shift WF only once, and then directly calculates the final solution using a power adjustment process (with the parallel-shift property as the underlying enabling mechanism). Numerical results show that both the proposed parallel-shift WF and the OFDM-based CR power allocation algorithms can run multiple times faster than the existing counterparts, and the gap on the running time increases with the total number of OFDM sub-channels in the system.
In this study, the authors study the downlink joint user scheduling and powerallocation in a single-cell distributed antennas system. Considering that all users are delay sensitive and without any assumption on the f...
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In this study, the authors study the downlink joint user scheduling and powerallocation in a single-cell distributed antennas system. Considering that all users are delay sensitive and without any assumption on the feasibility of the system, they formulate an optimisation problem to minimise the total power consumption while maximising the number of satisfied users. Given a user scheduling result, a deflation-based joint user removal and power allocation algorithm and a conservative power allocation algorithm are proposed. Owing to the complexity in full enumeration of all user scheduling results, they further propose a joint heuristic user scheduling and power allocation algorithm, in which a priority parameter is defined to determine the user scheduling order and the conservative power allocation algorithm is applied to execute the powerallocation. The user with the worst quality of experience is iteratively removed away from the active user set until all the remaining users are guaranteed with their quality of service requirements. Simulation results show that the authors proposed heuristic algorithm obtains a near optimal system performance in both user outage ratio and total power consumption.
Green communications are becoming an inevitable trend for future wireless network design, meanwhile, as a promising technique, distributed antenna systems (DAS) cater for this evolution. In this paper, we focus on the...
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ISBN:
(纸本)9781479935130
Green communications are becoming an inevitable trend for future wireless network design, meanwhile, as a promising technique, distributed antenna systems (DAS) cater for this evolution. In this paper, we focus on the problem of devising globally optimal antenna selection and power allocation algorithm in downlink DAS to achieve energy efficiency (EE) maximization. We formulate it as a mixed-integer nonlinear programming (MINLP), which maximizes EE subject to rate requirements, transmit power, and antenna selection constraints. By equivalent transformation, an iterative antenna selection and power allocation algorithm is proposed based on nonlinear fractional programming theory, and branch and bound methods. Our algorithm ensures global optimality and thus, it provides an important benchmark for performance evaluation of other heuristic algorithms targeting the same problem. Simulation results show that the computation complexity can be dramatically reduced comparing with exhaustive search, as well as demonstrate that a significant gain can be obtained in terms of EE against the schemes without antenna selection.
a low complexity resource allocation scheme is proposed for an underlay scheme over OFDM-based multi-user cognitive radio system. The resource allocation problem in an OFDM-based CR system includes subcarrier, power a...
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ISBN:
(纸本)9781479953592
a low complexity resource allocation scheme is proposed for an underlay scheme over OFDM-based multi-user cognitive radio system. The resource allocation problem in an OFDM-based CR system includes subcarrier, power and bit allocation that is a combinational optimization problem. In the proposed scheme, subcarrier and powerallocation is accomplished in two separate stages. The powerallocation problem under the interference channel model is a constraint optimization problem. It is notable that one of problem complexity source is coupling between the power budget and interference temperature constraints sets. In this algorithm the power budget constraint is used to determine initial point within iterative algorithm. Additionally, a margin parameter that depends on similarity of the interference channel branches is introduced. The simulation results for two statistical models, namely Rayliegh and Nakagami, show that the proposed algorithm performance is close to an optimal solution with lower complexity.
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