Search

Caching popular contents at edge networks (such as small-cell base stations) has been proposed to deal with the ever-growing mobile traffic. At the meantime, recommendation system is able to shape user demands for further prompting caching gain. In this paper, we study a multi-antenna multi-cell edge network employing transmit beamforming with caching-aware recommendation and user association. We first establish a framework for the joint problem of beamforming, user association, content caching and recommendation to minimize the content transmission delay of mobile users, by specifying a set of necessary conditions for all four component functions of the network. The resulting optimization problem corresponds to a non-convex, multi-timescale, and mixed-integer programming problem, which is hard to handle. To deal with the difficulty in solving the joint optimization problem by the direct formulation, we equivalently decompose it into three sub-problems. Then, we develop a computationally-efficient iterative algorithm to obtain the sub-optimal solution, where the three subproblems are tackled iteratively. Simulation results are conducted to demonstrate that the proposed algorithm can obtain lower transmission delay than baseline schemes. [ABSTRACT FROM AUTHOR]

This article proposes a new discrete-time predictive sliding mode control (DPSMC) for a parallel micropositioning piezostage to improve the motion accuracy in the presence of cross-coupling hysteresis nonlinearities and input constraints. Unlike the traditional linear discrete-time sliding mode control (DSMC), the proposed DPSMC is chattering free and has a faster convergence rate thanks to the design of a nonlinear discrete-time fast integral terminal sliding mode surface. Moreover, by combining with the receding horizon optimization, the sliding mode state is predicted to follow the expected trajectory of a predefined continuous sliding mode reaching law, which also allows the proposed controller to explicitly deal with constraints. The stability of the closed-loop system is analyzed under the model disturbances and constraints, and proves that the proposed DPSMC can offer a smaller quasi-sliding mode bandwidth than the traditional DSMC. The effectiveness of the proposed controller is validated by a series of numerical simulations and experiments. Results demonstrate the advantages of proposed DPSMC over the traditional DSMC method. [ABSTRACT FROM AUTHOR]

Due to the pervasive deployment of Wi-Fi devices, Wi-Fi-based human intrusion detection has attracted intensive attention in recent years. By analyzing temporal changes of signal caused by human movement, the existing solutions can achieve passive human intrusion detection. However, the detection of intrusion direction, from which the person intrudes the area of interests, is still a challenging task. Considering the influence of intrusion direction on the energy and spatial statistical distributions of multiple reflections, in this study, we propose WIDD, a Wi-Fi-based passive human intrusion direction detection system. Concretely, WIDD first extracts the angle of arrival (AoA) and amplitude distributions of the multipath signal and conducts the Jarque-Bera (JB) test to analyze the normality of the obtained distributions. A novel joint hypothesis testing algorithm is proposed to monitor changes in amplitude and AoA distributions of reflections and realize the human intrusion detection based on the analysis result. At last, it finds the reflection affected by the human intrusion most via the divergence evaluation and extracts the corresponding AoA to realize the intrusion direction detection. The comprehensive experimental evaluation demonstrates that WIDD provides human intrusion direction detection accuracy of about 0.943 and 0.931, under the scenario where the transmitter and receiver are separated by the glass and brick wall, respectively, outperforming the state-of-the-art solutions and shedding bright lights on ubiquitous human detection in practice. [ABSTRACT FROM AUTHOR]

Content caching is recognized as a promising solution to release the heavy burden of backhaul links and decrease the content transmission latency in Fog radio access networks (Fog-RANs). However, the content caching design is still a challenging problem with considering the user request patterns, the content delivery strategies, and the limited caching capacity. Recommendation has the capability of reshaping users’ content requests for further prompting caching gain. The joint recommendation, caching, beamforming holds the potential to improve the system performance of Fog-RANs. In this paper, a joint recommendation, caching, and beamforming scheme is proposed for multi-cell multi-antenna recommendation aware Fog-RANs. Aiming at minimizing the content transmission latency, we formulate a joint recommendation, caching, and beamforming optimization problem. The minimization problem is a very challenging two-timescale mixed integer nonlinear programming problem, which is hard to solve in general. By exploring structural properties of the problem, we propose an alternative optimization algorithm with low complexity through decomposing the original problem into three sub-problems. Extensive simulations show that our proposed method can significantly reduce the content transmission delay. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a hybrid mobile cloud/edge computing system with coexistence of centralized cloud and mobile edge computing, which enables computation offloading and data caching to improve the performance of users. Computation offloading and data caching decisions are jointly optimized to minimize the total execution delay at the mobile user side, while satisfying the constrains in terms of the maximum tolerable energy consumption of each user, the computation capability of each MEC server, and the cache capacity of each access point (AP). The formulated problem is non-convex and challenging because of the highly coupled decision variables. To address such an untractable problem, we first transform the original problem into an equivalent convex one by McCormick envelopes and introducing auxiliary variables. To the end, we propose a distributed algorithm based on the alternating direction method of multipliers (ADMM), which can achieve near optimal computation offloading and data caching decisions. The proposed algorithm has lower computational complexity compared to the centralized algorithm. Simulation results are presented to verify that the proposed algorithm can effectively reduce computing delay for end users while ensuring the performance of each user. [ABSTRACT FROM AUTHOR]

Circular-shift linear network coding (LNC) is a class of vector LNC with low encoding and decoding complexities, and with local encoding kernels chosen from cyclic permutation matrices. When $L$ is a prime with primitive root 2, it was recently shown that a scalar linear solution over GF($2^{L-1}$) induces an $L$ -dimensional circular-shift linear solution at rate $(L-1)/L$. In this paper, we prove that for arbitrary odd $L$ , every scalar linear solution over GF($2^{m_{L}}$), where $m_{L}$ refers to the multiplicative order of 2 modulo $L$ , can induce an $L$ -dimensional circular-shift linear solution at a certain rate. Based on the generalized connection, we further prove that for such $L$ with $m_{L}$ beyond a threshold, every multicast network has an $L$ -dimensional circular-shift linear solution at rate $\phi (L)/L$ , where $\phi (L)$ is the Euler’s totient function of $L$. An efficient algorithm for constructing such a solution is designed. Finally, we prove that every multicast network is asymptotically circular-shift linearly solvable. [ABSTRACT FROM AUTHOR]

To improve the pressure capability of ordinary ferrofluid seals with a large gap, a novel type of converging stepped ferrofluid seals was proposed. The leakage positions and the magnetic field distributions in the sealing gaps of the new device are studied computationally by means of the finite-element method. The theoretical pressure capabilities of the seal are calculated based on a new expression introduced for the particular new seal geometry and for different sealing gaps. Computational results for effects of the radial and axial sealing gaps on the pressure capabilities of the seal are compared to the experimental results obtained from measurements employing a prototype of the proposed new seal. A good agreement between theoretical and experimental results is obtained. It is found that the pressure capabilities of the new seal depend on the height of the radial sealing gap and on the width of the axial sealing gap. [ABSTRACT FROM AUTHOR]

We study a class of linear network coding (LNC) schemes, called circular-shift LNC, whose encoding operations consist of only circular-shifts and bit-wise additions. Formulated as a special vector linear code over GF(2), an $L$ -dimensional circular-shift linear code of degree $\delta $ restricts its local encoding kernels to be the summation of at most $\delta $ cyclic permutation matrices of size $L$. We show that on a general network, for a certain block length $L$ , every scalar linear solution over GF($2^{L-1}$) can induce an $L$ -dimensional circular-shift linear solution with 1-bit redundancy per-edge transmission. Consequently, specific to a multicast network, such a circular-shift linear solution of an arbitrary degree $\delta $ can be efficiently constructed, which has an interesting complexity tradeoff between encoding and decoding with different choices of $\delta $. By further proving that circular-shift LNC is insufficient to achieve the exact capacity of certain multicast networks, we show the optimality of the efficiently constructed circular-shift linear solution in the sense that its 1-bit redundancy is inevitable. Finally, both theoretical and numerical analysis imply that with increasing $L$ , a randomly constructed circular-shift linear code has linear solvability behavior comparable to a randomly constructed permutation-based linear code, but has shorter overheads. [ABSTRACT FROM AUTHOR]

It has been an active research issue for many years to construct new bent functions. For k odd with \gcd (n, k)=1 and a\in \mathbb F3^{n}^{*} , the function f(x)=Tr1^{n}(ax^{(({3^{k}+1})/{2})}) is weakly regular bent over \mathbb F3^{n} , where Tr1^{n}(\cdot) is the trace function from \mathbb F3^{n} to \mathbb F3 . This is the well-known Coulter–Matthews bent function. In this paper, we determine the dual function of f(x) completely. As a consequence, we find many classes of ternary bent functions not reported in the literature previously. Such bent functions are not quadratic if k>1 and have (((1+\sqrt 5)/2)^w+1-((1-\sqrt 5)/2)^w+1)/\sqrt 5 or (((1+\sqrt 5)/2)^n-w+1-((1-\sqrt 5)/2)^n-w+1)/\sqrt 5 trace terms, where 0

Vector linear network coding (LNC) is a generalization of the conventional scalar LNC, such that the data unit transmitted on every edge is an L -dimensional vector of data symbols over a base field GF( q ). Vector LNC enriches the choices of coding operations at intermediate nodes, and there is a popular conjecture on the benefit of vector LNC over scalar LNC in terms of alphabet size of data units: there exist (single-source) multicast networks that are vector linearly solvable of dimension L over GF( q . This paper introduces a systematic way to construct such multicast networks, and subsequently establish explicit instances to affirm the positive answer of this conjecture for infinitely many alphabet sizes p^{L} with respect to an arbitrary prime p$ . On the other hand, this paper also presents explicit instances with the special property that they do not have a vector linear solution of dimension L$ over GF(2) but have scalar linear solutions over GF( q'$ ) for some , where $q'$ can be odd or even. This discovery also unveils that over a given base field, a multicast network that has a vector linear solution of dimension $L$ does not necessarily have a vector linear solution of dimension $L' > L$ . [ABSTRACT FROM AUTHOR]

Recently, as it can greatly increase the capacity of cellular networks through spatial diversity, cooperative communications has been obtaining more and more attention. As a widely used schema, user (user equipment, UE) cooperation presents its advantage. However, due to the users' selfish nature, UE may be unwilling to serve as a relay node if they cannot obtain a corresponding reward. On the contrary, to save energy for longer standby time, particularly when there is energy shortage, many source users would like to purchase the relay service from other idle UE. Therefore, reconciling the demand of both sides is a challenging problem to be resolved. In this paper, a realistic double-auction scenario is constructed between multiple source UE and multiple idle UE in a cellular network. We take the avaricious psychology of network entities into consideration by determining the ask and bid prices through a markup, which is the function of their residual energy. To solve this double-auction-based optimal relay assignment problem, we transform it into maximum matching (MM) and maximum weighted matching (MWM) problems, respectively, and we solve them by corresponding algorithms. Experimental results show that the proposed algorithms dramatically maximize the system performance involving successful source–relay pairs, system throughput, and social welfare (SW), compared with other idealized truthful double-auction scheme that only consider the system throughput. [ABSTRACT FROM PUBLISHER]

Atmospheric-pressure discharge plasma is a promising tool for many applications due to its enhanced plasma chemistry. In this paper, a low-temperature atmospheric-pressure nitrogen plasma jet generated by bare metal electrode’s discharge is reported. The typical electrical and optical characteristics of the atmospheric-pressure plasma jet (APPJ) are studied. Optical emission spectrum shows that excited OH, NO, N2(C-B), N2+ (B-X), N2(B-A), and O emissions are produced by the plasma jet. When the applied voltage is 2.5 kV, the vibrational and rotational temperatures of the APPJ are, respectively, 2275 and 325 ± 5 K. Hydrophilic treatment of the superhydrophobic aluminum surface is also presented, and the results show that the wettability of the APPJ-treated areas is obviously improved, which was mainly due to the slight morphological changes and the incorporation of oxygen-containing functional groups. A pumpless antigravity water transport on APPJ-induced wettability contrast patterning surface is also presented to show the potential applications of the APPJ hydrophilic treatment of metals. These results demonstrate the application prospects of bare electrode’s discharge plasma jet, especially in metal-based smart surface fabrications. [ABSTRACT FROM PUBLISHER]