BlueMesh: Degree-Constrained Multi-Hop Scatternet Formation for Bluetooth Networks

In this paper we describe BlueMesh, a new protocol for the establishment of scatternets, i.e., multi-hop wireless networks of Bluetooth devices. BlueMesh defines rules for device discovery, piconet formation and piconet interconnection so to generate connected scatternets with the following desirable properties. BlueMesh forms scatternets without requiring the Bluetooth devices to be all in each other transmission range. BlueMesh scatternet topologies are meshes with multiple paths between any pair of nodes. BlueMesh piconets are made up of no more than 7 slaves. Simulation results in networks with over 200 nodes show that BlueMesh is effective in quickly generating a connected scatternet in which each node, on average, does not assume more than 2.4 roles. Moreover, the route length between any two nodes in the network is comparable to that of the shortest paths between the nodes.     

On the Analysis of the Bluetooth Time Division Duplex Mechanism

Efficient communication in Bluetooth networks requires design of intra and inter-piconet scheduling algorithms, and therefore, numerous algorithms have been proposed. However, due to complexities of the Bluetooth MAC, the performance of these algorithms has been analyzed mostly via simulation. We present analytic results regarding the exhaustive, gated, and limited (pure round robin) scheduling algorithms in piconets with bidirectional and unidirectional traffic. We show that a piconet operated according to the limited scheduling algorithm is equivalent to a 1-limited polling system and present exact results regarding symmetric piconets with bidirectional traffic. Then, the difficulties in analyzing the performance of the exhaustive and gated algorithms in a piconet with bidirectional traffic are demonstrated. In addition, we present exact analytic results for piconets with unidirectional traffic. We show that, surprisingly, in symmetrical piconets with only uplink traffic, the mean waiting time is the same for the exhaustive and limited algorithms. This observation results from the differences between piconets and traditional polling systems and can be extended for time-division-duplex systems with arbitrary packet lengths. Furthermore, we show that the mean waiting time in a piconet with only uplink traffic is significantly higher than its corresponding value in a piconet with only downlink traffic. Finally, we numerically compare the exact results to approximate results, presented in the past.     

Load-adaptive inter-piconet scheduling in small-scale Bluetooth scatternets

Bluetooth enables wireless communication via ad hoc networks. The basic topology (piconet) is a collection of slaves controlled by a master. A scatternet is a multihop network of piconets. We anticipate that most scatternets will be composed of only a few piconets. However, even in small scatternets, efficient data flow requires the design of inter-piconet scheduling algorithms. Thus, this article presents and evaluates a load adaptive scheduling algorithm tailored for small-scale scatternets. The main advantage of this algorithm is the use of the Bluetooth low-power hold mode, which allows greater flexibility than other low-power modes. A simulation model has been developed in order to evaluate the performance of the algorithm. We show that the results obtained by the model are very close to the analytic results. Then we evaluate the performance of various intra-piconet scheduling algorithms. Finally, we present simulation results regarding inter-piconet scheduling, and compare the proposed algorithm to algorithms using the sniff mode.     

基于随机共振和非中心F分布的频谱感知算法

为解决频谱感知算法在低信噪比（SNR）时检测概率较低且检测所需采样点数较多的问题,提出了基于随机共振和非中心F分布（SRNF）的频谱感知算法。通过引入直流随机共振噪声,建立了SRNF的系统模型,推导了服从非中心F分布的检验统计量表达式、虚警概率与检测概率以及判决门限表达式,并采用数值法求解最佳的随机共振噪声参数。仿真结果表明,在低信噪比时,所提基于SRNF算法的检测性能优于能量检测（ED）算法和基于F分布的盲频谱感知（BSF）算法,当虚警概率为5%、信噪比为–12 d B、采样点数为200时,所提算法的检测概率是95%,分别比BSF算法和ED算法高34%和67%;当信噪比为–12 dB、检测概率达到95%时,所提算法所需的采样点数是210,比BSF算法节省了340个采样点。此外,噪声不确定度对所提算法的影响小于ED算法。     

链形结构的蓝牙分散网拓扑构成算法与性能仿真

提出了一种新的链形结构的蓝牙分散网拓扑构成算法：所有蓝牙节点均以0．5的概率进入查询或查询扫描状态，同时地进行点对点的连接，形成尽可能多的临时皮网，再反复通过各种形式的合并与重组形成更大的皮网与多个皮网形成的组，直至最终形成仅有一个组的链形结构的分散网。仿真与性能分析表明：该算法实现简单，形成的分散网具有较少的皮网数目、较小的各节点角色的平均数与较小的节点最大度数、网络创建时间较短、拓扑动态维护方便、各节点无需均在通信范围内等优点。该算法适用于蓝牙分散网的拓扑构成。     

Hybrid Multi-FPGA Board Evaluation by Permitting Limited Multi-Hop Routing

Multi-FPGA Boards (MFBs) have been in use for more than a decade for implementing systems requiring high performance and for emulation/prototyping of multimillion gate chips. It is important to develop an MFB architecture which can be used for emulation or prototyping of a large number of circuits. A key feature of an MFB is its routing architecture defined by its inter-Field-Programmable Gate Array (FPGA) connections. There are two types of inter-FPGA connections, namely–fixed connections (FCs) connecting a pair of FPGAs through dedicated wires and programmable connections (PCs) which connect a pair of FPGAs through a programmable switch. An architecture which has a mix of both these type of connections is called a hybrid routing architecture. It has been shown in the literature [7] that a hybrid MFB architecture is more efficient for emulation than an architecture with only one type of connections. The cost of an MFB and delay of the emulated circuit on it depends on the number of PCs used for emulation. An objective of a designer of an MFB for circuit emulation is to minimize the required number of PCs. In this paper, we describe algorithms to evaluate the requirement of PCs for many hybrid routing architectures.The requirement of PCs can be reduced if some programmable connections are replaced by a connection using only FCs by routing through FPGAs. Such a routing is called multi-hop routing. We present an optimal and a heuristic algorithm for estimation of PCs when limited number of hops through FPGAs are permitted. The unique feature of our evaluation scheme is that it is generic and treat routing architecture as a parameter. We have used benchmark circuits as well as synthetic cloned circuits for testing our algorithms. Our heuristic algorithm is very fast and gives optimal results most of the time. Our algorithms can be used for actual routing during circuit emulation.     

Energy-Scalable Protocols for Battery-Operated MicroSensor Networks

In wireless sensor networks, the goal is to gather information from a large number of sensor nodes and communicate the information to the end-user, all under the constraint of limited energy resources. Network protocols minimize energy by using localized communication and control and by exploiting computation/communication tradeoffs. In addition, data fusion algorithms such as beamforming aggregate data from multiple sources to reduce data redundancy and enhance signal-to-noise ratios, thus further reducing the required communications. We have developed a sensor network system that uses a localized clustering protocol and beamforming data fusion to enable energy-efficient collaboration. We compare the performance of two beamforming algorithms, the Maximum Power and the Least Mean Squares (LMS) beamforming algorithms, using the StrongARM SA-1100 processor. Results show that the LMS algorithm requires less than one-fifth the energy required by the Maximum Power beamforming algorithm with only a 3 dB loss in performance, thus showing that the LMS algorithm is better suited for energy-constrained systems. We explore the energy-scalability of the LMS algorithm, and we propose an energy-quality scalable architecture that incorporates techniques such as variable filter length, variable voltage supply and variable adaptation time.     

Coexistence of IEEE 802.11b and Bluetooth: An Integrated Performance Analysis

IEEE 802.11b wireless networks and Bluetooth networks provide complimentary services using the same unlicensed radio frequency band. As the benefits of utilizing these services become increasingly apparent, the likelihood of mutual interference also increases. The well-known frequency hopping algorithm and adaptive frequency hopping algorithm do not fully consider the interference level of the operating environment. In this paper an algorithm called interference-aware adaptive frequency hopping (IAFH) is presented and implemented on Bluetooth devices to mitigate the interference between IEEE 802.11b and Bluetooth wireless networks. An analytical model of IAFH is developed to evaluate the performance of 802.11b stations and Bluetooth devices in a mutual interference environment. The analysis comprises the collision probability, packet error rate, and throughput performance for both IEEE 802.11b and Bluetooth wireless networks. Simulation results confirm that 802.11b station and IAFH-enabled Bluetooth devices experience lower packet error rates and better throughput as compared to the frequency hopping and adaptive frequency hopping algorithms.     

VAE/MPM/GA Technique for DoA Estimation Using Optimized Antenna Arrays

Many algorithms have been proposed to estimate the direction of arrival for the targets, but through using a large number of snapshots. In real time applications such as automotive radar, this is unacceptable as it causes delay and heavy processing. Instead, if only a small number of snapshots or, optimally, a single snapshot is available for DoA estimation, it will be fast and efficient. Single snapshot algorithms have a drawback as they require a large number of antenna elements, which considered a limiting factor. In this paper, a single snapshot DoA estimation technique is introduced by using optimized antenna arrays. The proposed algorithm is based on utilization of virtual array extension, matrix pencil method, and the genetic algorithm. The use of virtual array extension greatly improves the MPM performance. Furthermore, it exhibits a high DoA estimation accuracy by using a reduced number of antenna elements. The genetic algorithm is employed to determine the minimum number of antenna elements, which are required to estimate the DoAs with minimal root mean square error.

     

Distributed self-healing and variable topology optimization algorithms for QoS provisioning in scatternets

Bluetooth is an enabling technology for Personal Area Networks. A scatternet is an ad hoc network created by interconnecting several Bluetooth piconets, each with at most eight devices. Each piconet uses a different radio channel constituted by a frequency hopping code. The way the devices are grouped in different piconets and the way the piconets are interconnected greatly affect the performance of the scatternet in terms of capacity, data transfer delay, and energy consumption. There is a need to develop distributed scatternet formation algorithms, which guarantee full connectivity of the devices, reconfigure the network due to mobility and failure of devices, and interconnect them such a way to create an optimal topology to achieve gainful performance. The contribution of this paper is to provide an integrated approach for scatternet formation and quality-of-service support (called SHAPER-OPT). To this aim, two main procedures are proposed. First, a new scatternet formation algorithm called self-healing algorithm producing multihop Bluetooth scatternets (SHAPER) is developed which forms tree-shaped scatternets. A procedure that produces a meshed topology applying a distributed scatternet optimization algorithm (DSOA) on the network built by SHAPER is then defined. Performance evaluation of the proposed algorithms, and of the accordingly created scatternets, is carried out by using ns2 simulation. Devices are shown to be able to join or leave the scatternet at any time, without compromising the long term connectivity. Delay for network setup and reconfiguration in dynamic environments is shown to be within acceptable bounds. DSOA is also shown to be easy to implement and to improve the overall network performance.     

Adaptive energy conserving algorithms for neighbor discovery in opportunistic Bluetooth networks

In this paper, we introduce and evaluate novel adaptive schemes for neighbor discovery in Bluetooth-enabled ad-hoc networks. In an ad-hoc peer-to-peer setting, neighbor search is a continuous, hence battery draining process. In order to save energy when the device is unlikely to encounter a neighbor, we adaptively choose parameter settings depending on a mobility context to decrease the expected power consumption of Bluetooth-enabled devices. For this purpose, we first determine the mean discovery time and power consumption values for In different Bluetooth parameter settings through a comprehensive exploration of the parameter space by means of simulation validated by experiments on real devices. The fastest average discovery time obtained is 0.2 s, while at an average discovery time of I s the power consumption is just 1.5 times that of the idle mode on our devices. We then introduce two adaptive algorithms for dynamically adjusting the Bluetooth parameters based on past perceived activity in the ad-hoc network. Both adaptive schemes for selecting the discovery mode are based only on locally-available information. We evaluate these algorithms in a node mobility simulation. Our adaptive algorithms reduce energy consumption by 50% and have up to 8% better performance over a static power-con serving scheme     

Source-adaptive multilayered multicast algorithms for real-timevideo distribution

Layered transmission of data is often recommended as a solution to the problem of varying bandwidth constraints in multicast video applications. Multilayered encoding, however, is not sufficient to provide high video quality and high network utilization, since bandwidth constraints frequently change over time. Adaptive techniques capable of adjusting the rates of video layers are required to maximize video quality and network utilization. We define a class of algorithms known as source-adaptive multilayered multicast (SAMM) algorithms. In SAMM algorithms, the source uses congestion feedback to adjust the number of generated layers and the bit rate of each layer. We contrast two specific SAMM algorithms: an end-to-end algorithm, in which only end systems monitor available bandwidth and report the amount of available bandwidth to the source, and a network-based algorithm, in which intermediate nodes also monitor and report available bandwidth. Using simulations that incorporate multilayered video codecs, we demonstrate that SAMM algorithms can exhibit better scalability and responsiveness to congestion than algorithms that are not source-adaptive. We also study the performance trade-offs between end-to-end and network-based SAMM algorithms     

基于阵列天线和稀疏贝叶斯学习的室内定位方法

由于多径和非同源等因素的影响,传统基于蓝牙信号强度的室内定位方法的性能精度和稳定性都不高。针对基于蓝牙信号的复杂室内环境定位问题,该文提出基于低成本阵列天线的室内定位方法,该方法利用单通道轮采极化敏感阵列天线对蓝牙信号进行采样,然后结合暗室测量获得的准确阵列流形和极化快收敛稀疏贝叶斯学习(P-FCSBL)算法实现信源的角度估计,最后通过角度实现定位。该方法充分利用极化信息和角度信息来实现目标和多径信号的分离,同时对单信源的同时采样保证了估计的稳定性。最后通过实测数据处理验证了该方法的有效性。     

Wavelength converter placement under different RWA algorithms in wavelength-routed all-optical networks

Sparse wavelength conversion and appropriate routing and wavelength assignment (RWA) algorithms are the two key factors in improving the blocking performance in wavelength-routed all-optical networks. It has been shown that the optimal placement of a limited number of wavelength converters in an arbitrary mesh network is an NP-complete problem. There have been various heuristic algorithms proposed in the literature, in which most of them assume that a static routing and random-wavelength assignment RWA algorithm is employed. However, the existing work shows that fixed-alternate routing and dynamic routing RWA algorithms can achieve much better blocking performance. Our study further demonstrates that the wavelength converter placement and RWA algorithms are closely related in the sense that a well-designed wavelength converter placement mechanism for a particular RWA algorithm might not work well with a different RWA algorithm. Therefore, the wavelength converter placement and the RWA have to be considered jointly. The objective of this paper is to investigate the wavelength converter placement problem under the fixed-alternate routing (FAR) algorithm and least-loaded routing (LLR) algorithm. Under the FAR algorithm, we propose a heuristic algorithm called minimum blocking probability first for wavelength converter placement. Under the LLR algorithm, we propose another heuristic algorithm called weighted maximum segment length. The objective of the converter placement algorithms is to minimize the overall blocking probability. Extensive simulation studies have been carried out over three typical mesh networks, including the 14-node NSFNET, 19-node EON, and 38-node CTNET. We observe that the proposed algorithms not only outperform existing wavelength converter placement algorithms by a large margin, but they also can achieve almost the same performance compared with full wavelength conversion under the same RWA algorithm.     

Pattern-Flipping Chase-Type Decoders with Error Pattern Extracting Viterbi Algorithm over Partial Response Channels

Towards the goal of achieving better error correction performance in data storage systems, iterative soft decoding of low density parity check (LDPC) codes and soft-decision decoding of Reed-Solomon (RS) codes have started receiving increasing research attention. However, even with increased computing power, complexities of soft-decision decoding algorithms are still too high for real products which require high throughput and small hardware area. Another problem is that the performance gains of those approaches are smaller for magnetic recording channels than they are for memoryless additive white Gaussian noise (AWGN) channels. We propose a new soft-decision decoding algorithm (based on the Chase algorithm), which takes advantage of pattern reliability instead of symbol reliability or bit reliability. We also present a modified Viterbi algorithm that provides probable error patterns with corresponding reliabilities. Simulation results of the proposed algorithms over the partial response (PR) channel show attractive performance gains. The proposed algorithm dramatically reduces the number of iterations compared to the conventional Chase2 algorithm over the PR channel.     

基于不完整约束自然梯度算法的多道盲解卷

针对多输入多输出(MIMO)系统的Bussgang算法可能收敛到错误的解，而且收敛速度慢的缺点。章提出了不完整约束的自然梯度算法，该算法是由不完整约束条件与自然梯度算法的结合而推导出来的。通过计算机仿真对这两种多道盲解卷算法进行了比较，仿真试验表明：提出的算法收敛速度快，并且比Bussgang算法稳定。     

一种基于人眼图像灰度分布特征的虹膜定位算法

提出了一种基于人眼图像灰度分布特征的虹膜定位算法。该算法不必检测到所有的虹膜边界点,只需要分别在虹膜的内外边界上各检测到3个点即可。然后利用落在同一个边界上的3个点,根据“非共线的3点确定1个圆”的几何原理,计算出边界圆的参数,从而确定虹膜内外边界。对CASIA虹膜图像数据库进行了大量的实验,结果表明,该算法与经典的虹膜定位算法（如Daugman的算法和边缘检测算子结合Hough变换的算法）相比,定位结果更加准确,定位速度大幅度提高。     

基于增量式鲁棒非负矩阵分解的短文本在线聚类

对社会化媒体产生的大量短文本进行聚类分析具有重要的应用价值,但短文本往往具有噪音数据多、增长迅速且数据量大的特点,导致现有相关算法难于有效处理.提出一种基于增量式鲁棒非负矩阵分解的短文本在线聚类算法STOCIRNMF.STOCIRNMF基于非负矩阵分解构建短文本聚类模型,通过l_2,1范数设计模型的优化求解目标函数提高鲁棒性,同时应用增量式迭代更新规则实现短文本的在线聚类.在搜狐新闻标题和微博短文本数据集上进行相关实验,结果表明STOCIRNMF不仅比现有代表性算法具有更好的聚类性能,而且能够有效对微博话题进行在线检测.     

基于V-结构&对数似然函数定向与禁忌爬山的贝叶斯网络结构算法

针对爬山算法搜索空间过大和易陷入局部最优的问题,该文提出基于V-结构&对数似然函数定向与禁忌爬山的贝叶斯网络结构算法(VTH)。该算法利用定向最大支撑树约束搜索空间,在最大支撑树定向过程中,提出V-结构与对数似然函数(VLL)结合的定向策略;在评分搜索过程中,提出禁忌爬山(VTH)评分搜索策略,该策略将禁忌表清空机制与爬山搜索的局部择优准则结合,在提高全局寻优能力的同时也能保证搜索效率。该算法与其他算法在Asia, Car, Child和Alarm 4种标准网络中进行仿真实验,对比汉明距离、F1值、平衡评分函数(BSF)值、运行时间4个指标,验证了该算法的有效性。     

Design and Analysis of an Efficient Evolutionary Image Segmentation Algorithm

Evolutionary image segmentation algorithms have a number of advantages such as continuous contour, non-oversegmentation, and non-thresholds. However, most of the evolutionary image segmentation algorithms suffer from long computation time because the number of encoding parameters is large. In this paper, design and analysis of an efficient evolutionary image segmentation algorithm EISA are proposed. EISA uses a K-means algorithm to split an image into many homogeneous regions, and then uses an intelligent genetic algorithm IGA associated with an effective chromosome encoding method to merge the regions automatically such that the objective of the desired segmentation can be effectively achieved, where IGA is superior to conventional genetic algorithms in solving large parameter optimization problems. High performance of EISA is illustrated in terms of both the evaluation performance and computation time, compared with some current segmentation methods. It is empirically shown that EISA is robust and efficient using nature images with various characteristics.