Search

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this article, the cooperation between coherent control and noises in open spin systems is studied, aiming to demonstrate that such cooperation can provide new possibilities for parametrization in quantum metrology. The cooperative scheme proposed here outperforms the standard scheme, with higher precision achieved. More specifically, the effect of cooperative interaction between coherent control and noises in conventional single‐spin systems described by Lindblad master equations is illustrated, with the magnitude of a magnetic field taken as the parameter to be estimated and encoded in the noisy dynamics besides the Hamiltonian. The scenarios of both spontaneous emission and dephasing noise have been analyzed, where the associated quantum Fisher information has been given. Furthermore, it has been demonstrated that in the realm where quantum metrology is mostly applied in practice, the precision limit under the cooperative scheme in the presence of noises can surpass the ultimate precision limit under the unitary dynamics. On the other hand, multiple‐spin systems have also been considered. It is shown that the coupling between different spins can help realize non‐local parametrization under the cooperative scheme, with the ground state made entangled. This thus leads to the improvement of precision limit, which has been proved and visualized in this article. [ABSTRACT FROM AUTHOR]

There are different theories that try to give a satisfactory answer to the question of why people should obey the law. One of these proposals is the principle of fair play (or fairness). It says that if a person, who is part of a social cooperation scheme, benefits from the efforts of the other participants he/she is bound to do his part; otherwise, he/she acts unfairly. Several scholars have recognized the value of the principle, but others have demonstrated with good arguments that it has many difficulties to justify a general duty of obedience in complex schemes such as the State. The main objective of the paper is to assess, by using the literature review method, the virtues and weaknesses of the principle of fair play as a theory of political obligation. The obtained conclusion is that this theory could be an appropriate proposal as long as it satisfies some requirements. [ABSTRACT FROM AUTHOR]

With the increasing demands for mobile users to obtain content, the heterogeneous networks (HetNets), which consolidate the backbone networks with mobile edge networks, have been regarded as a promising paradigm to provide mobile users with high quality of experience (QoE). However, the limited network resources and caching capacity become a new challenge to deliver content in HetNets. Therefore, in this paper, a cooperative scheme between edge server and content provider in HetNets is proposed to improve the performance of content delivery. Firstly, a novel framework of content delivery with backbone networks and mobile edge networks is introduced. The edge servers are deployed at the edge of networks and close to users. Secondly, a Q-learning based scheme for content caching is developed to securely cache contents with the cooperation between edge server and content provider. Thirdly, the cooperative interaction between edge server and content provider is modeled as the double auction game. Each player can obtain the maximum utility from the equilibrium strategy. Finally, simulation results show that the proposed scheme can improve the efficiency of content delivery and bring more utilities to edge server and content provider than the conventional schemes.

The millimeter wave (mmWave) communication has drawn intensive attention with abundant band resources. In this paper, we consider the popular content distribution (PCD) problem in the mmWave vehicular network. In order to offload the communication burden of base stations (BSs), vehicle-to-vehicle (V2V) communication is introduced into the PCD problem to transmit contents between on-board units (OBUs), and improve the transmission efficiency. We propose a full-duplex (FD) cooperative scheme based on coalition formation game, and the utility function is provided based on the maximization of the number of received contents. The contribution of each member in the coalition can be transferable to its individual profit. While maximizing the number of received contents in the fixed time, the cooperative scheme also ensures the individual profit of each OBU in the coalition. We evaluate the proposed scheme by extensive simulations in mmWave vehicular networks. Compared with other existing schemes, the proposed scheme has superior performances on the number of possessed contents, and system fairness. Besides, the low complexity of the proposed algorithm is demonstrated by the switch operation number, and CPU time. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel cooperative scheme of joint optimal resource allocation, such that the overall performance of the coexisting radar-communications (CRC) system can be improved. In our proposed scheme, target detection and multiuser communication are performed by radar and communication subsystems at the same time, as well as a control center, which is responsible for joint resource management. We aim to minimize the ISLR for target detection and maximize the sum-rate for communications simultaneously by jointly optimizing the band assignment and transmit power allocation. Since the resulting optimization problem involving two performance metrics and a binary constraint is a multiobjective nonconvex problem, a two-tier iterative decomposition (TT-ID) approach is devised to obtain the globally optimal solution. However, compared with the conventional radar signals, the autocorrelation function of the devised radar signal may still have relatively high sidelobes. In particular, when the data transmission becomes the primary purpose of the CRC system, the sidelobe performance gets worse. As a consequence, some weak targets are most likely overshadowed by the adjacent strong targets through the matched filtering at the radar receiver. To address this, a spectral estimation algorithm based on the Bayes Cauchy–Gaussian (Bayes–CG) model is employed to further reduce the range sidelobes of the matched filter output at the radar receiver according to the prior distribution of the desired autocorrelation. Finally, several numerical results are provided to show the merits of the proposed method.

In this letter, we investigate a scenario where both multistatic radar and point-to-point communication systems are present with a partial or total spectrum-sharing constraint. We propose a new adaptive radar receivers placement mechanism that jointly maximizes the signal-to-interference-plus noise ratio of each communication transmitter–radar receiver channel while minimizing the geometric dilution of precision. The proposed joint approach performs well in the presence of communication interference on the radar side. In fact, the proposed approach helps to increase the capability to properly demodulate the communication data at each radar receiver resulting in the less radar measurement errors due to communication interference while enhancing the target positioning accuracy. [ABSTRACT FROM AUTHOR]

Traditional accounts of the fair play principle suggest that, under appropriate conditions, those who benefit from the cooperative labor of others acquire an obligation of repayment. However, these accounts have had little to say about the nature of such obligations within morally or legally problematic cooperative schemes, taking the matter to be either straightforward or unimportant. It is neither. The question of what sorts of fair play obligations obtain for those who benefit from illicit cooperative activity is a matter of great complexity and consequence with implications for, inter alia, global economic justice. In this essay, I explore the nature of this obligation within illicit cooperative schemes, specifically those with so-called negative externalities, or deleterious effects on non-members of the scheme. I conclude that the willing beneficiaries of such schemes acquire a fair-play obligation to recognize and respond to their culpability. This reconceptualization of the fair play principle opens up new avenues for exploring the obligations of those who benefit from acts of collective wrongdoing. [ABSTRACT FROM AUTHOR]

In the past decades, cooperative communications schemes have gained significant attention in wireless networks. The cooperative scheme leads to longer transmission time which can considerably degrade the system performance. We evaluate the saturation throughput and saturation delay of the Markov chain model with direct/cooperative schemes to support QoS in WLANs. Simulation results show that differentiating the contention window size is better than differentiating the arbitration interframe space in terms of throughput and delay. [ABSTRACT FROM AUTHOR]

Recently, the multi-hop cellular networks have been widely studied in order to enhance the cell performances such as the cell capacity. While most of these works merely use the multi-hop methods instead of direct transmission without considering the co-channel inter-cell interference, signal transmission mode and the effects of the number of antennas. With the consideration of above important elements, this paper proposed an improved cellular system with multi-relay amplifies-and-forward (AF) cooperative transmission scheme and the corresponding capacity expression is derived under the corresponding environment. By using the potential space diversity and selecting relays based on maximizing the capacity, the cellular system capacity can be improved effectively. The simulation results show that with the assistance of optimal selected relays, the improved cooperative cellular system capacity with multi-relay AF transmission scheme performs better than single-hop cellular system. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel cooperative scheme of joint optimal resource allocation, such that the overall performance of the coexisting radar-communications (CRC) system can be improved. In our proposed scheme, target detection and multiuser communication are performed by radar and communication subsystems at the same time, as well as a control center, which is responsible for joint resource management. We aim to minimize the ISLR for target detection and maximize the sum-rate for communications simultaneously by jointly optimizing the band assignment and transmit power allocation. Since the resulting optimization problem involving two performance metrics and a binary constraint is a multiobjective nonconvex problem, a two-tier iterative decomposition (TT-ID) approach is devised to obtain the globally optimal solution. However, compared with the conventional radar signals, the autocorrelation function of the devised radar signal may still have relatively high sidelobes. In particular, when the data transmission becomes the primary purpose of the CRC system, the sidelobe performance gets worse. As a consequence, some weak targets are most likely overshadowed by the adjacent strong targets through the matched filtering at the radar receiver. To address this, a spectral estimation algorithm based on the Bayes Cauchy–Gaussian (Bayes–CG) model is employed to further reduce the range sidelobes of the matched filter output at the radar receiver according to the prior distribution of the desired autocorrelation. Finally, several numerical results are provided to show the merits of the proposed method. [ABSTRACT FROM AUTHOR]