Compressive sensing-based wind speed estimation for low-altitude wind-shear with airborne phased array radar

An important issue in low-altitude wind-shear detection is to estimate the wind speed of wind field. In this paper, a novel method for wind speed estimation with airborne phased array radar is proposed by combining space time adaptive processing and compressive sensing. The proposed method is able to achieve accurate wind speed estimate in the condition of limited number of sampling pulses, as demonstrated by numerical examples.     

Secure and efficient anonymous authentication scheme for three-tier mobile healthcare systems with wearable sensors

The mobility and openness of wireless communication technologies make Mobile Healthcare Systems (mHealth) potentially exposed to a number of potential attacks, which significantly undermines their utility and impedes their widespread deployment. Attackers and criminals, even without knowing the context of the transmitted data, with simple eavesdropping on the wireless links, may benefit a lot from linking activities to the identities of patient’s sensors and medical staff members. These vulnerabilities apply to all tiers of the mHealth system. A new anonymous mutual authentication scheme for three-tier mobile healthcare systems with wearable sensors is proposed in this paper. Our scheme consists of three protocols: Protocol-1 allows the anonymous authentication nodes (mobile users and controller nodes) and the HSP medical server in the third tier, while Protocol-2 realizes the anonymous authentication between mobile users and controller nodes in the second tier, and Protocol-3 achieves the anonymous authentication between controller nodes and the wearable body sensors in the first tier. In the design of our protocols, the variation in the resource constraints of the different nodes in the mHealth system are taken into consideration so that our protocols make a better trade-off among security, efficiency and practicality. The security of our protocols are analyzed through rigorous formal proofs using BAN logic tool and informal discussions of security features, possible attacks and countermeasures. Besides, the efficiency of our protocols are concretely evaluated and compared with related schemes. The comparisons show that our scheme outperforms the previous schemes and provides more complete and integrated anonymous authentication services. Finally, the security of our protocols are evaluated by using the Automated Validation of Internet Security Protocols and Applications and the SPAN animator software. The simulation results show that our scheme is secure and satisfy all the specified privacy and authentication goals.     

A secure search protocol for lightweight and low-cost RFID systems

In radio frequency identification (RFID) systems, search protocols are used to find a specific item in a large number of tagged products. These protocols should be secure against RFID attacks such as traceability, impersonation, DoS and eavesdropping. Sundaresan et al. (IEEE Trans Dependable Secure Comput, 2015) presented a server-less search protocol based on 128-bits PRNG function and claimed that their method can address all vulnerabilities of previous protocols. In this paper, we prove that Sundaresan et al.’s protocol is vulnerable to traceability attack with the high probability. In addition, we present an improved protocol to solve the proposed problem and analyze its security level informally and formally based on AVISPA tool and BAN logic.     

Range extension cooperative MAC to attack energy hole in duty-cycled multi-hop WSNs

Effective techniques for extending lifetime in multi-hop wireless sensor networks include duty cycling and, more recently introduced, cooperative transmission (CT) range extension. However, a scalable MAC protocol has not been presented that combines both. An On-demand Scheduling Cooperative MAC protocol (OSC-MAC) is proposed to address the energy hole problem in multi-hop wireless sensor networks (WSNs). By combining an on-demand strategy and sensor cooperation intended to extend range, OSC-MAC tackles the spatio-temporal challenges for performing CT in multi-hop WSNs: cooperating nodes are neither on the same duty cycle nor are they necessarily in the same collision domain. We use orthogonal and pipelined duty-cycle scheduling, in part to reduce traffic contention, and devise a reservation-based wake-up scheme to bring cooperating nodes into temporary synchrony to support CT range extension. The efficacy of OSC-MAC is demonstrated using extensive NS-2 simulations for different network scenarios without and with mobility. Compared with existing MAC protocols, simulation results show that while we explicitly account for the overhead of CT and practical failures of control packets in dense traffic, OSC-MAC still gives 80–200 % lifetime improvement.     

Seeking powerful information initial spreaders in online social networks: a dense group perspective

The rapid growth of online social networks (OSNs) has ultimately facilitated information spreading and changed the economics of mobile networks. It is important to understand how to spread information as widely as possible. In this paper, we aim to seek powerful information initial spreaders with an efficient manner. We use the mean-field theory to characterize the process of information spreading based on the Susceptible Infected (SI) model and validate that the prevalence of information depends on the network density. Inspired by this result, we seek the initial spreaders from closely integrated groups of nodes, i.e., dense groups (DGs). In OSNs, DGs distribute dispersedly over the network, so our approach can be fulfilled in a distributed way by seeking the spreaders in each DG. We first design a DG Generating Algorithm to detect DGs, where nodes within the DG have more internal connections than external ones. Second, based on the detected DGs, we design a criterion to seek powerful initial spreaders from each DG. We conduct experiments as well as statistical analysis on real OSNs. The results show that our approach provides a satisfactory performance as well as computational efficiency.     

Optimal probabilistic encryption for distributed detection in wireless sensor networks based on immune differential evolution algorithm

The problem of binary hypothesis testing is considered in a bandwidth-constrained low-power wireless sensor network operating over insecure links. To prevent passive eavesdropping from enemy fusion center (EFC), the sensor observations are randomly flipped according to pre-deployed flipping rates before transmission. Accordingly, a constrained optimization problem is formulated to minimize the fusion error of ally fusion center (AFC) while maintain EFC’s error at high level. We demonstrated that the fusion error is a non-convex function of the flipping rates, thus an immune based differential evolution algorithm is designed to search the optimal flipping rates, such that the EFC always gets high error probability at the cost of a small degeneration of the AFC’s fusion performance. Furthermore, the optimal thresholds of the fusion rules are calculated based on the statistics of the sensor data, which further degenerates the detection performance of the EFC, since it is not aware of the statistics of the sensor observations after data flipping, resulting in its threshold does not match the observations. Simulation results demonstrated that the AFC can appropriately acquire the original nature state, while the EFC is prevent to detect the target regardless of the signal-to-noise and sensor numbers.     

一种新型平面阿基米德螺旋天线的分析与设计

对一种新型的平面阿基米德螺旋天线--锯齿状平面阿基米德螺旋天线进行了研究。首先给出了该天线的几何结构,介绍了其主要特点和应用领域,设计并制作了一个2.9~6.2GHz的锯齿状平面阿基米德螺旋天线。测试表明,与普通平面阿基米德螺旋天线相比,该天线能够缩小尺寸,展宽频带,很好地改善天线的低频特性。     

基于神经网络的S参数估计法

该文讨论了神经网络用于微波电路的一种新的训练算法,是基于误差反传算法与模拟退火算法相结合的。本算法可以解决BP网的局部最小问题。并且不用对神经网络模型的结构作任何改动。通过一个具体算例的计算验证了这种算法。     

基于GaAs的新型稀磁半导体材料(Ga,Mn)As

介绍了一种基于 Ga As的新型稀磁半导体材料 ( Ga,Mn) As,包括 ( Ga,Mn) As的制备方法、结构特性、磁性质及磁输运性质。最后 ,展望了 ( Ga,Mn) As的应用前景