Search

The fusion and interdependence of cyber and physical system has become the main characteristic of power system, which has brought new challenges to the risk assessment of the power information and communication network at the same time. Since the risk situation assessment of power information and communication network is a multilevel and multiple indicators issue with a deep correlation between the indicators, a comprehensive risk situation assessment model is constructed. First, the index system of risk situation assessment is constructed. Second, the model of comprehensive evaluation of risk situation is constructed based on fuzzy measure and choquet fuzzy integral. The subjective weighting calculation method combines with the objective calculation method to determine the fuzzy density of single index, and then calculate fuzzy measure based on the obtained fuzzy density. Employ choquet fuzzy integral operator to integrate comprehensive estimation value of index set. Finally, the maximum membership degree principle is adopted to obtain the comprehensive risk situation. By applying the evaluation method to the simulation analysis of a power communication network, the validity of the proposed method is shown.

In this paper, we investigate the sum-rate maximization of cellular users (CUs) and device-to-device (D2D) pairs for the D2D communications underlaying cellular networks over the Nakagami-m fading channel. We consider a resource-abundant scenario where the number of CUs is more than that of D2D pairs and discuss the joint optimization of signal-to-interference-plus-noise ratio (SINR) thresholds and CU-D2D pairing. We formulate the problem as mixed-integer non-linear programming, which is NP-hard in general. To solve the problem, we propose a two-step approach. First, we add virtual D2D pairs to make the number of D2D pairs equal to that of CUs and derive the near-optimal SINR threshold for each possible CU-D2D pairing by the simulated annealing algorithm. Second, the optimal CU-D2D pairing can be obtained by the Hungarian (HG) algorithm. The simulation results show that: 1) the proposed SINR policy outperforms the other policies by about 11.3%-63.4% and 2) compared with several state-of-the-art resource allocation policies, HG allocation can achieve an average sum-rate improvement of 10.9%-72.8%.

Since broadcast communication is considered the highly appropriate technique for the dissemination of safety messages in vehicular ad hoc networks (VANETs), it is vital to design a high-efficient medium access control (MAC) protocol for vehicles accessing wireless channel. However, the characteristics of VANETs, such as high-velocity vehicles, highly dynamic topology and very unstable communication link, lower the performance of existing MAC protocols. In this paper, we propose a novel Capture-aware TDMA-based MAC (CT-MAC) protocol, which can better utilize the channel resource than the existing MAC protocols by setting the optimal frame length with taking capture effect into account. To obtain the realistically optimal frame length, the closed form expression of probability of capture effect is derived under Nakagami-m fading channel which is proper to model the small-scale fading channel in VANETs. Besides, a discrete Markov chain is introduced to analyze the impact of capture effect on channel utilization. The theoretical analyses and the simulation results show that the reliability of broadcast and the efficiency of channel utilization are significantly improved.

Driven by a plethora of real machine learning applications, there have been many attempts at improving the performance of a classifier applied to imbalanced dataset. In this paper we propose a maximum entropy machine (MEM) based hybrid algorithm to handle binary classification problems with high imbalance ratios and large numbers of features in the datasets. At the training stage, we combine an efficient MEM algorithm with the SMOTE algorithm to build a classifier in a batch manner. At the application stage, the different-cost strategy is incorporated into the MEM algorithm to handle the imbalance learning problem in an online manner. Experiments are conducted based on various real datasets (including one China Mobile dataset and several other standard test datasets) with different imbalance ratios and different numbers of features. The results show that the proposed algorithm outperforms the state-of-the-art algorithms significantly in terms of robustness and overall classification performance.

To fully exploit the increasingly dense deployments of mobile base station (BS) infrastructure, this paper proposes a novel caching paradigm called explicit caching, which stores selective contents at BSs and exposes such contents to users for volunteer browsing and download. We formulate the explicit caching problem as a joint content recommendation and delivery problem, which aims to maximize the expected quality-of-experience (QoE) per user over the long term. Optimal algorithms are given to solve the problem with varying degrees of cross-layer information. The impacts of user interest profile, cache storage space, BS backhaul capacity, cross-layer information, user mobility, and user mobility prediction on the system performance are analyzed and discussed.

Hybrid cognitive radio (CR) networks can jointly utilize both licensed and unlicensed radio resources to gain better performance over pure licensed/unlicensed networks. This paper studies the system-level capacity of a hybrid cellular network that consists of licensed base stations (BSs) and unlicensed CR relays. Two limiting cases are considered, in which the CR relays are assumed to have infinite cache and no cache, respectively. We systematically derive the system capacity under different simplifying assumptions on interference and path loss. Our results reveal how the system capacity is related to various system parameters such as BS/relay density, bandwidth, power, and CR reliability. Such an insight can be useful for the planning of future heterogeneous cellular networks.

Motivated by the deployment of cognitive radio (CR) based relays in cellular networks, this paper studies the fundamental limits of heterogeneous cognitive Gaussian relay channels (HCGRCs). Unlike conventional relay channels, in HCGRC a source transmits to a relay in a licensed band, while the relay transmits to a destination in an unlicensed cognitive spectrum band. The licensed and unlicensed bands are characterized by different power, bandwidth and reliability constraints. Taking an information-theoretic perspective, the fundamental properties of the HCGRC are analyzed thoroughly in terms of capacity, spectral efficiency (SE), and energy efficiency (EE). With regard to each metric, we derive the optimal resource allocation strategy and discuss the impacts of CR spectrum reliability and relay location on the metric. We find that in HCGRC, improving the SE and EE are not necessarily conflicting objectives. Instead, both metrics can be optimized simultaneously with proper resource allocation.

Echo cancellation is one of the key technologies for digital repeater. Based on the Standard of China for DTMB (Digital Television Terrestrial Multimedia Broadcasting), a scheme of actualizing echo cancellation with adaptive filter is presented in this paper. Using matlab Simulink as the platform, we added PN sequence to digital TV signals, then, estimated the response of the coupling channel by using DLMS (Delayed Least Mean Square) algorithm. Finally, we generated a feedback signal to cancel echo with the estimation. In order to implement this scheme on hardware, we used retiming and folding technologies to save the hardware cost. The results of the computer simulation indicate a favorable performance in echo cancellation and low hardware cost.

This paper presents the design scheme and implementation of a RF Signal Record & Playback System, which is able to record and store RF data directly from an active antenna or generate RF signals from data stored on a solid state drive. It introduces the organization and building components of the system, with a key emphasis on the design of system hardware, PCI Express bus interface and the DMA mode. By using the DMA mode, the continuous transfer rate of the bus is up to 1200Mbit/s. The experiment indicates that the system eliminates the bottleneck of real-time data acquisition and can be applicable to various kinds of RF signal especially the GPS navigation signal.

A body length based population model was put forward to depict the dynamics of large icefish (Protosalanx hyalocranius), in the context of ecological risk analysis for northern China waters. The body length of large icefish individual governs its feeding preference to zooplankton, forage fishes, and phytoplankton, as renders body length distribution indispensible for modeling of the large icefish population. A normal distribution and a shifted lognormal distribution were found to fit the body lengths reasonably well for mean length below and above 80mm, respectively. Use of the fitted body length distributions was made to estimate the transition rate from omnivorous juveniles to adults that prey exclusively on forage fishes. With the body length distributions embedded, a large icefish population model was established and parameterized with typical vitality values in Daihai Lake in northern China. The model was simulated along with the modules for phytoplankton, zooplankton, and forage fishes, and the simulated dynamics exhibited consistence with the seasonal fluctuations observed in the field. The large icefish population model was deemed a useful demonstration for ecological risk assessment of populations with short lifecycles.

Most Medium Access Control (MAC) protocols used in wireless sensor networks consider only static nodes. However, there is an increasing interest in sensor network applications where some or all of the nodes are mobile. In this paper, the issue of mobility in sensor networks is addressed, first at a high level, and then in terms of the additional requirements that are placed on the MAC layer by the presence of mobile nodes in the network. Existing proposals for sensor network MAC protocols are then compared under three different mobility scenarios. Finally, the status of current research is summarized and the open research issues of MAC protocols are identified.

In this paper, we propose a modified algorithm based on complex ICA (independent component analysis) for cancelling the feedback interference in the WCDMA repeater under time-varying multi-path channels. The proposed algorithm made use of Non-Gaussian distribution character of the signals and separated feedback from received signals by estimating feedback path adaptively in the frame work of ICA. The algorithm was evaluated through computer simulation by being applied to the feedback cancelling filter of the WCDMA repeater. The simulation results demonstrated that the proposed one is superior to the conventional LMS algorithm in terms of the cancelling performance.

In this paper, we propose a non-contention ejection architecture to improve the performance of Network-on-Chip (NoC). In this architecture, the contention is avoided by allocating a dedicated channel for every packet which may be ejected simultaneously, which make sure that packets in the network can be ejected promptly, and thus the number of packets stayed in the network is decreased and the communication performance is improved. Results show that compared with traditional ejection architecture, the proposed architecture improves the communication performance greatly with reasonable area increase.

In this paper, we propose a hybrid method to provide Quality of Service (QoS) for Networks-on-Chip (NoC). This method combines the advantages of connection-based schemes and connection-less schemes. Thus, compared with traditional methods, this method guarantees the latency between one flit’s generation in the source node and its reception in the destination node, supports a wide range of traffic types such as latency critical, low bandwidth traffic and streaming data which only have bandwidth requirement, and has high link-bandwidth utilization. Moreover, the NoC which supports the proposed method is implemented. Simulation and synthesis results show that this method can guarantee the bandwidth and latency well and is relatively low-cost.

An appropriate design based on well-defined system parameters and architecture can make a huge difference in the performance. In particular, there is a need for improved digital Automatic Gain Control (AGC) for use in Orthogonal Frequency Division Multiplexing (OFDM) system. In this paper, we study the principle of the AGC loop, and adopt an appropriate AGC loop model which takes hardware resource and performance in considering. On this basis, we give a detail on how to design parts of AGC loop on FPGA, including implementation process and setting parameters. The performances of the locking time and gain jitter are given in theory. Then the achieving results on FPGA is shown to improve the design is feasible and effective.

Clustering is an effective approach to hierarchically organizing network topology and to prolong the lifetime of a wireless sensor network. Current clustering protocols usually utilize two techniques: selecting cluster heads with more residual energy and rotating cluster heads periodically to distribute the energy consumption among nodes in each cluster. Most of the researches in this field has focused on energy-efficient solutions, but caring less about the communication between Cluster Head (CH) nodes and Base Station (BS). When the sensor field is far away from the base station, the cluster heads are burdened with heavier relay traffic and tend to die much faster. To mitigate the problem, we propose an Energy-Efficient Hierarchical Routing Protocol (EEHRP) for long range transmission in the wireless sensor networks. It uses a number of gateway nodes, which do not engage in clustering, to connect the CHs and base station. They are responsible for transmitting packets received from the CHs to the base station, thus the CHs can preserve some energy in data forwarding and the gateway nodes can ease their burden by not participating in clustering. Simulation results show that EEHRP obviously increases the network lifetime and well balances the energy consumption among the sensor nodes.

In this paper, we focus on the digital predistortion for the linearization of power amplifiers (PAs) with intrinsic hard nonlinearities, such as Doherty PAs, envelope tracking (ET) PAs widely explored in the third generation (3G) communication systems. Conventional Volterra-series-based predistortion with high degree nonlinearities suffers from the difficulty of real-time implement and the problem of numerical instability. Accordingly, a block-oriented Hammerstein predistortion with cubic-spline static nonlinearity is proposed, and the separable nonlinear least squares (SNLS) method is used to identify the Hammerstein coefficients, which significantly reduces the dimension of search space. A normalization convergence scheme is also presented to ensure the global optimum. The experiments are carried out on uplink single-carrier WCDMA signals, the results show that both the static nonlinear distortion and the memory effect of the PA under test are compensated significantly, and fast convergence is achieved by the normalization scheme.

Ouring the past decade, wireless Ad-hoc network have been more and more popular in both military and civil areas, which due to its distinguishing characteristics as following: strongly network constructing, highly mobility, rapidly transmission. A SoC design for broad band wireless ad-hoc network node is proposed in this paper. In details, the system architecture design is given as well as the hardware design for customized IP core and the specific device driver. At the same time, a kind of data exchange technology which makes use of Network Bridge is designed to support the connection between Ethernet and ad-hoc network. The results of the hardware simulation and experiment show that the SoC system operates normally and has a good performance index.

To reduce the nonlinear distortion caused by RF power amplifier (PA) in wireless transmission system, digital predistortion is widely used for PA linearization. This paper mainly discusses on the memory polynomial predistortion based on QRD-RLS algorithm, which is analyzed in the MATLAB simulation. It is also discussed about the Systolic implementation of complex QRD-RLS algorithm based on CORDIC technique. At last, with System Generator, the system of digital predistortion based on QRD-RLS algorithm is designed on FPGA, and the system is verified in hardware platform

Digital predistortion (DPD) is a highly cost-effective technique to linearize high power amplifiers (HPAs) in wireless applications. The polynomial-type behavior models are widely used both for HPAs and predistorters, but they often suffer from the numerical stability problem when the higher order nonlinearities are included. When wideband signals are transmitted, the envelope impedances of HPAs can not always keep constant, therefore the envelope frequency components caused by the even-order nonlinearities become the main source of the memory effect of HPAs. In this paper, we propose a new polynomial predistorter model considering the influence of the envelope frequency components, which shows better performance in out-of-band spectral suppression; then, we propose a dual-orthogonal-basis polynomial model for complex Gaussian inputs, which alleviate the numerical instability of digital predistortion.

Node Localization plays an important role in the applications of wireless sensor networks (WSNs). The whole localization mechanism of WSN target nodes consists of three key steps, the identification and data exchange step, the range estimation step, and the position estimation step. Based on the RSSI (Received Signal Strength Indication) technology, the BP (Back Propagation)-loss channel model is proposed to approximate the channel transmission characteristic adaptively by resilient gradient descent method. Due to the constraint of low powered, and low cost property of WSN nodes, the concentrative localization algorithm is adopted. The RMIC (RSSI-margin and Improved Chan) algorithm and the optimal anchor nodes library selection scheme are presented to improve the localization accuracy. The simulation results show the performance improvement of the proposed localization mechanism. Range measurement and localization are realized on our WSN nodes, and the experiment data confirm the validity of the mechanism.

Digital Intermediate Frequency (IF) technology is widely used in wireless communication system in recent years. This paper introduces a digital IF module, which is applied to a Broadband Wireless Ad hoc Network (BWANET) system. IF module contains Digital Down Conversion (DDC) and Digital Up Conversion (DUC), filter design is one of its key technologies. The design of IF filter is based on technology of multi-rate signal processing, interpolation filter performs up-sampling of the data, while decimation filter finishes down-sampling of the data. After a comparative analysis, this paper presents an IF filter structure which requires minimum hardware resource usage. Hardware co-simulation, which is a new simulation method, is adopted for functional simulation in this paper; it greatly reduces the simulation time. The results of the hardware co-simulation and experiment show that the IF module operates normally and has a good performance index.

—To balance energy consumption for nodes in wirelesssensor network (WSN) is an important considering factor. Asimple model is set up to analytically evaluate the energyconsumption in WSN by using aggregation mechanism. It isshow that energy consumption of an aggregation nodeincreases so rapidly in the neighborhood of the sink node. Amodified hierarchical data aggregation strategy is proposed inorder to achieve balanced energy depletion by reducing thecluster head selection probability near the sink. Simulationresults show that, this method can reduce the energyconsumption efficiently and prolong the lifetime of the wholenetworks.

Energy-efficiency is a key problem in wireless sensor networks(WSNs) due to the severe power constraint of wireless nodes. When designing protocols for WSNs, it is important for us to consider not only network performance, but also energy consumption. It is difficult for a traditional layered design method to satisfy several objectives at the same time. In this paper, we introduced a cross-layer scheme for WSNs, by adopting the microeconomic concept of utility to balance energy consumption as well as QoS constraint among all nodes at the same time. The proposed scheme can improve the overall network performance.

Time-slot synchronization is very important for a TDMA-based Ad Hoc Network. In this paper, we propose a decentralized algorithm to synchronize the local time slot reference. The differences between the time slots of neighboring nodes with consideration of signal propagation delay are used to compute the slot adjustment. The methods on how to choose parameters are also discussed. Simulation experiments have been carried out for different scenarios, and the results show that this algorithm has fast convergence rate and modest computation burden, hence is suitable to run on terminals of Ad Hoc networks.

A time slot synchronous method to support real time oriented TDMA for multi-hop ad hoc wireless network is described. In this algorithm, each node repetitively corrects its local time slot reference by an adjustment, which is computed according to its time slot difference between those of its neighbor nodes. This algorithm is simultaneously co-computed by each node. Simulations show that fast convergence rate and modest computation are achieved.

The main goal of this paper is to evaluate the anti-interference performance of a Bluetooth piconet in a multi-Bluetooth piconets environment. An overview of the frequency hop selection mechanism is presented and the basic design based on 79-hop is described. We study correlation characteristics of the hopping sequences in typical scenarios and the simulation results show that the interference caused by the neighboring Bluetooth piconet is sensitive both to the address offset and the frequency offset between the victim and the inbreaker.

Time slot synchronization is very important for a TDMA- based ad hoc network. An existing method to achieve time slot synchronization in ad hoc network is the decentralized slot synchronization algorithm. However, interference nodes in the network may lead to un-convergence of this algorithm. In this paper, a method for eliminating the interference in decentralized slot synchronization is presented. To evaluate the performance of the proposed mechanism, the influence to the convergence of slot synchronization in the network is investigated. Simulation results indicate that, with this method, the interference is effectively eliminated from the computation of decentralized slot synchronization.