Barrier coverage with line-based deployed mobile sensors

Barrier coverage of a wireless sensor network is a critical issue in military and homeland security applications, aiming to detect intruders that attempt to cross the deployed region. While a range of problems related to barrier coverage have been investigated, little effort has been made to explore the effects of different sensor deployment strategies and mechanisms to improve barrier coverage of a wireless sensor network after it is deployed. In this paper we study the barrier coverage of a line-based sensor deployment strategy and explore how to exploit sensor mobility to improve barrier coverage. We first establish a tight lower bound for the existence of barrier coverage under the line-based deployment. Our results show that the barrier coverage of the line-based deployment significantly outperforms that of the Poisson model when the random offsets are relatively small compared to the sensor’s sensing range. To take advantage of the performance of line-based deployment, we further devise an efficient algorithm to relocate mobile sensors based on the deployed line so as to improve barrier coverage. The algorithm finds barrier gaps and then relocates mobile sensors to fill the gaps while at the same time balancing the energy consumption among mobile sensors. Simulation results show that the algorithms can effectively improve the barrier coverage of a wireless sensor network for a wide range of deployment parameters. Therefore, in wireless sensor network applications, the coverage goal, possible sensor deployment strategies, and sensor mobility must be carefully and jointly considered. The results obtained in this paper will provide important guidelines and insights into the deployment and performance of wireless sensor networks for barrier coverage.     

Multiple point of interest discovery and coverage with mobile wireless sensors

Environmental monitoring has become a typical application of wireless sensor networks. The concept of monitoring certain Points of Interest (PoIs) instead of the whole sensor field helps in reducing the costs of the deployment and improving the performance in terms of coverage. However, the problems of multiple PoI discovery, coverage and data report are still solved separately and there are no works that combine the aforementioned problems into a single deployment scheme. In this work, we present a novel approach for mobile sensor deployment, where we combine multiple PoI discovery and coverage with network connectivity preservation in order to capture the dynamics of the monitored area. Furthermore, we derive analytical expressions for circular movement parameters and examine the performance of our approach through extensive simulation campaigns.     

Approximation algorithms for deployment of sensors for line segment coverage in wireless sensor networks

The coverage problem in wireless sensor networks deals with the problem of covering a region or parts of it with sensors. In this paper, we address the problem of covering a set of line segments with minimum number of sensors. A line segment ? is said to be 1-covered if it intersects the sensing region of at least one among the sensors distributed in a bounded rectangular region R. We assume that the sensing radius of each sensor is uniform. The problem of finding the minimum number of sensors needed to 1-cover each member in a given set of line segments in R is NP-hard. We propose two constant factor approximation algorithms and a PTAS (polynomial time approximation scheme) for the problem for 1-covering a set of axis-parallel line segments. We also show that a PTAS exists for 1-covering a set of arbitrarily oriented line segments in R where the lengths of the line segments are bounded within a constant factor of the sensing radius of each sensor. Finally, we propose a constant factor approximation algorithm for k-covering axis-parallel line segments such that sensors maintain a minimum separation among them.     

室内无线综合覆盖

移动通信和计算机网络的发展使得越来越多的无线业务需要室内信号覆盖,我国目前的覆盖方式是由每个运营商为其经营的业务信号单独建设室内覆盖系统,这种方式覆盖业务少,反复施工,浪费资源.文章提出建设无线综合覆盖的理念和实施方法,即"用一个宽带无线覆盖系统满足当今乃至未来可预见的各运营商对无线业务、容量和技术的要求,以及服务于整个楼宇用户的各种类型的无线应用需求".     

无线传感器网络综述

简要介绍了无线传感器网络体系结构、特点和应用领域。总结了无线传感器网络媒体访问控制协议、节能路由算法和节点定位的研究成果,探讨了存在的问题和今后发展的方向。     

Plug-and-play sensors in wireless networks

The availability of these self-configuring networks of wireless sensor data will accelerate the ongoing trend toward automation ranging from the factory floor to the office to the warehouse and outdoors. Lower installation costs, lower operating costs, and the improved factory efficiency will provide significant cost savings. Technicians will be able to walk near a machine and obtain data on its existing state and its history, enabling better monitoring of the equipment condition and avoiding expensive downtime. Open standards like Bluetooth and IEEE 1451 are key to supporting the proliferation of these technologies     

Energy management in wireless sensor networks with energy-hungry sensors

The energy problem in wireless sensor networks remains one of the major barriers preventing the complete exploitation of this technology. Sensor nodes are typically powered by batteries with a limited lifetime, and even when additional energy can be harvested from the external environment, it remains a limited resource to be consumed judiciously. Efficient energy management is thus a key requirement, with most strategies assuming that data acquisition consumes significantly less energy than data transmission. When this assumption does not hold, effective energy management strategies should include policies for an efficient use of energy-hungry sensors.     

云南喀斯特地貌无线网络覆盖

【】针对云南喀斯特地形地貌无线网络覆盖困难、投资效益低的问题,提出网络建设优先级策略、制式选择策略和分层覆盖策略。根据网络流量、渠道分布、3G终端分布三个维度对不同网格进行评价并排出优先级,对不同优先级的网格实行不同建设策略,同时结合覆盖区域地形地貌、市场预期,细化各区域最优频段部署方案,必要场景实施分层覆盖,在确保快速提升云南喀斯特地貌无线网络覆盖的同时,保证投资效益。     

Information coverage for wireless sensor networks

Coverage is a very important issue in wireless sensor networks. Current literature defines a point to be covered if it is within the sensing radius of at least one sensor. In this paper we argue that this is a conservative definition of coverage. This definition implicitly assumes that each sensor makes a decision independent of other sensors in the field. However, sensors can cooperate to make an accurate estimation, even if any single sensor is unable to do so. We then propose a new notion of information coverage and investigate its implications for sensor deployment. Numerical and simulation results show that significant savings in terms of sensor density for complete coverage can be achieved by using our definition of information coverage compared to that by using the existing definition.     

Location-unaware coverage in wireless sensor networks

In scenarios where sensors are placed randomly, redundant deployment is essential for ensuring adequate field coverage. This redundancy needs to be efficiently exploited by periodically selecting a subset of nodes (referred to as a “cover”) that actively monitor the field, and putting the remaining nodes to sleep. We consider networks in which sensors are not aware of their locations or the relative directions of their neighbors. We develop several geometric and density-based tests that enable a location-unaware sensor to intelligently determine whether it should turn itself off without degrading the quality of field coverage. These tests rely on distance measurements and exchanged two-hop neighborhood information. We design an algorithm (LUC) that exploits these tests for computing covers. Based on this algorithm, we propose two distributed protocols (LUC-I and LUC-P) that periodically select covers and switch between them so as to extend the network lifetime and tolerate unexpected failures. Our protocols are highly efficient in terms of message overhead and processing complexity. We implement LUC-I in TinyOS and evaluate it using the TOSSIM simulator. Experimental results indicate that our approach significantly prolongs the network lifetime and achieves comparable performance to location-aware protocols.     

TD-SCDMA无线网络覆盖解决方案

介绍了由无线接入网络(RAN)组成的TD-SCDMA网络拓扑结构和由大唐移动开发的基于TD-SCDMA标准的基站产品及其特点,介绍了各种典型的网络组网应用场景及其特点,并针对这些场景,提出了相应、灵活的组网覆盖解决方案.结论是大唐移动TD-SCDMA产品及其方案在未来中国TD-SCDMA网络的建设中有广阔的市场前景.     

Sleep scheduling with expected common coverage in wireless sensor networks

Sleep scheduling, which is putting some sensor nodes into sleep mode without harming network functionality, is a common method to reduce energy consumption in dense wireless sensor networks. This paper proposes a distributed and energy efficient sleep scheduling and routing scheme that can be used to extend the lifetime of a sensor network while maintaining a user defined coverage and connectivity. The scheme can activate and deactivate the three basic units of a sensor node (sensing, processing, and communication units) independently. The paper also provides a probabilistic method to estimate how much the sensing area of a node is covered by other active nodes in its neighborhood. The method is utilized by the proposed scheduling and routing scheme to reduce the control message overhead while deciding the next modes (full-active, semi-active, inactive/sleeping) of sensor nodes. We evaluated our estimation method and scheduling scheme via simulation experiments and compared our scheme also with another scheme. The results validate our probabilistic method for coverage estimation and show that our sleep scheduling and routing scheme can significantly increase the network lifetime while keeping the message complexity low and preserving both connectivity and coverage.     

室内无线综合覆盖(续)

“用一个宽带无线覆盖系统满足当今乃至未来可预见的各运营商对无线业务、容量和技术的要求，以及服务于整个楼宇用户的各种类型的无线应用需求。”从这样的设计理念出发，江森自控的覆盖方案首先考虑的是各种频率的信号在系统中的共存，即如何抑制各信号间的干扰，在克服干扰的前提下，使系统中并存的各信号辐射都尽可能小，从而实现整体辐射最小，保证绿色的室内无线环境。     

Enhanced algorithms for deploying the minimum sensors to construct a wireless sensor network having full coverage of critical square grids

With the rapid technological development of sensors, many applications have been designed to use wireless sensor networks to monitor a certain area and provide quality-of-service guarantees. Therefore, the coverage problem had an important issue for constructing wireless sensor networks. Recently, a coverage problem of constructing a minimum size wireless sensor network to fully cover critical squares in a sensor field, termed CRITICAL-SQUARE-GRID COVERAGE, has received much attention. CRITICAL-SQUARE-GRID COVERAGE is shown to be NP-Complete, and an approximation algorithm, termed Steiner-tree-based critical grid covering algorithm (STBCGCA), is proposed accordingly. In STBCGCA, a sensor is selected to cover critical squares only if at least one of the critical squares is fully covered by the sensor. However, a critical square grid can be cooperatively covered by two or more sensors; that is, one sensor covers one part of the critical square, and the other sensors cover the other part of the critical square. This motivates us to propose two efficient algorithms based on STBCGCA, termed critical-grid-partitioned (CGP-STBCGCA) and reference-point-covered (RPC-STBCGCA), that select sensors that can cooperatively cover critical squares in an attempt to minimize the size of the wireless sensor network. The theoretical analysis shows that sensors deployed by CGP-STBCGCA and RPC-STBCGCA can form a connected wireless sensor network that fully covers all critical grids. In addition, a performance guarantee for CGP-STBCGCA is provided. Simulation results show that the ratio of the average number of deployed sensors in STBCGCA to that in CGP-STBCGCA and RPC-STBCGCA in about 90 % of the cases was between 1.08 and 2.52 for CRITICAL-SQUARE-GRID COVERAGE.     

Two thermocouples low power wireless sensors network

This paper presents technologies and experiments of a wireless sensors using two thermocouples network. It was established that the energy consumption during sensor measurements is usually up to 10 times lower compared to the energy consumption at the time of establishing wireless connection for most protocols. For this reason, new simplified wireless connection protocol was created.Extremely low energy wireless sensor hardware and software equipment was designed. The newly created universal measurement module allows the use not only thermocouples, but also various types of analogue sensors, thermocouples, pressure bridges, Resistance Temperature Detectors (RTD) and digital sensors communicating through SPI or I2C interface. The newly designed specific power supply scheme allows to supply the sensor and radio module with the voltage from 1.2 V to 3.6 V batteries. When conducting periodic measurements every second, the use of newly designed hardware and software equipment enables the wireless sensor to be operated for up to 3 years from two 1200 mAh capacity batteries.     

优化无线网络的覆盖时间算法

通过无人机(Unmanned Aerial Vehicles,UAVs)扮演空中基站以提高无线网络的覆盖率已成为最有前景的技术。为此,研究了多个无人机部署问题。首先,推导了基于海拔高度和天线增益的UAVs的下行链路覆盖概率函数,然后依据圆形堆积理论,计算了UAVs的位置,进而在保证UAVs的最大覆盖时间的同时,最大化覆盖区域,并推导了在保证目标覆盖概率时所需的UAVs数。实验结果表明,依据全向天线的波束宽度和覆盖要求,调整UAVs海拔高度,可消除UAVs间的干扰,并最大化覆盖时间。     

Compound event barrier coverage in wireless sensor network

In wireless sensor networks (WSN),more and more people utilize barrier coverage to monitor compound events.The data of compound event barrier coverage (CEBC) comes from different types of sensors.It will be subject to multi-constraints under complex conditions in real-world application.Aiming at the merging problem of compound event confidence,a computational model based on joint probability density was proposed.In order to solve the optimization problem of compound event barrier coverage under multiple complex constraints,an active set multiplier policy (ASMP) was proposed.The algorithm can calculate the coverage ratio efficiently and allocate the sensor resources reasonably in compound event barrier coverage.The algorithm can simplify complex problems to reduce the computational load of the network and improve the efficiency of the network.The simulation results demonstrate that the ASMP algorithm is more efficient in the allocation of sensor resources and network optimization.     

新的无线传感器网络覆盖控制算法

首先,设计了节点自适应传感半径调整算法(AASR,adaptive adjustment of sensing radius),通过节点自适应选择最佳的覆盖范围,有效地进行节点覆盖控制,减少节点能量虚耗,提高覆盖效率。其次,从调整效果、能量消耗和覆盖冗余度3个方面对节点自适应传感半径调整算法进行了模拟实验和分析。仿真结果表明,AASR能够有效提高节点生存时间,减少能量消耗,提高覆盖率。