基于能量有效性的协作节点配置问题研究

无线通信的能耗主要由功放能耗和电路能耗两部分组成。在大距离传输中,通信能耗由功放能耗主导,电路能耗往往被忽略不计。而在以短距离传输为主的传感器网络中,电路能耗成为不可忽略的一部分,甚至有可能超过功放能耗成为通信能耗的主导。本文就如何通过节点间协作降低网络的通信能耗展开研究,拟解决协作通信中的协作节点配置问题。本文将信源-协作节点间距离纳入协作通信系统模型,提出一种针对调制参数、协作中继数、信源-协作簇距离对协作通信能耗进行联合优化的策略,并在无线传感器网络环境下对该模型的能耗进行了仿真。仿真结果表明,在传输距离一定的情况下,通过协作节点的数量、调制参数和信源-协作簇距离的联合优化配置,可以更有效地提高协作传输的节能效果。      

Z number improved reference ideal method-based decision-making process for enforcing cooperation during data dissemination in mobile ad hoc networks

In mobile ad hoc networks (MANETs), cooperative communication and resource constraint are the two important core characteristics essential to guarantee trusted data dissemination. The cooperative communication between mobile nodes depends on the trust rendered by them towards the process of reliable data routing. However, stringent resource constraints of mobile nodes such as energy, memory, communications, and computations result in the introduction of selfish and malicious node that completely degrades the network performance in different dimensions. In this paper, Z number improved reference ideal method (RIM)-based decision-making process (NIRIMDMP) is proposed with the merits of maximizing deviation method (MDM) and best–worst method (BWM) to ensure reliable data routing by modeling the cooperation degree in terms of Z number. This NIRIMDMP adopted Z number to represent the information reliability and handle the problem of inherent uncertainty during the process of evaluating each mobile node in the routing process. In specific, MDM and BWM are included into the proposed NIRIMDMP to determine comprehensive attribute weights based on the calculated objective and subjective weights that could be possible derived in routing. It extended the merits of classical RIM using Z numbers to confirm reliable ranking of mobile nodes, even when the optimal solution exists amid extreme values taken into consideration for assessing the mobile nodes during decision making. Simulation investigations of the proposed NIRIMDMP confirmed improved throughput and network lifetime with reduced control overhead, energy consumptions, and delay independent of the amount of malicious and non-cooperative nodes.     

Cooperative MAC Design in Multi-Hop Wireless Networks—Part II: When Source and Destination are Two-Hops Away from Each Other

Ubiquitous and pervasive computing and networking are envisaged as part of the future 5G wireless communication landscape where devices which are multi-hops away from each other are connected in a cooperative way. In this paper, we investigate a challenging case in cooperative communications where source and destination are two-hops away from each other. From the perspective of MAC design, we propose a novel MAC protocol which enables two-hop cooperative communications by involving one or more one-hop neighbors of both source and destination as the relays for cooperative communication. To do so, a concept referred to as Multiple Relay Points (MRPs) has been introduced and the MRPs are selected by jointly considering the link quality of both hops. In addition to employing a static scheme which always uses a fixed number of relays for cooperative communication, we have also proposed an adaptive scheme which can optimally adjust the number of relays flexibly according to channel conditions. Through performance evaluation and comparison with the original IEEE 802.11 based scheme, we demonstrate that more reliable communications, reduced transmission power and significant throughput improvement can be achieved by using our two-hop cooperative MAC protocol, especially when operated in the adaptive mode.     

Context-aware cooperative testbed for energy analysis in beyond 4G networks

The complexity of heterogeneous wireless networks in synergy with battery powered mobile devices is driving new stringent requirements in terms of power efficiency to ensure that battery life, environmental and thermal criteria can be met. Modern mobile devices are equipped with multiple interfaces, which allow them to exploit the benefits offered by heterogeneous networking environments, but on the other hand, drain battery swiftly. In this paper, architecture for a context-based node and a testbed platform for the analysis of energy consumption of heterogeneous cooperative communications are presented. The demonstrative testbed comprises a WiFi Access Point, which provides WiFi coverage in the infrastructure mode, as well as nodes capable of communicating through short-range ultra-wideband WiMedia. The testbed includes a context aware module that provides and stores information related to different nodes in the system. The paper shows how context information can be used to save the energy of mobile devices and extend their battery lifetime using short-range communications. The testbed is used as a proof-of-concept for the practical implementation of the cooperative communications concept. The obtained results show that significant amount of energy can be saved using context information along cooperation among multiple interfaces, in comparison to direct communications.     

In-Network Computations of Machine-to-Machine Communications for Wireless Robotics

Wireless robotics enables wide applications of service robots to benefit human life. However, effective machine-to-machine communications would be the foundation of operation. With cloud-based architecture, we innovatively demonstrate in-network computation to significantly alleviate the requirement of communication bandwidth for multi-hop networking, to achieve spectrum-efficient M2M communications. We further characterize the coverage geographical of machines to impact effective operation of wireless robotics.     

分布式协同传输协议设计与系统实现

协同传输作为一种可靠通信技术,通过利用空间分集,能够克服无线通信收发双方经历的信道衰落、噪声干扰、路径损耗等,有效提升系统传输性能。目前有关协同通信技术的基础理论研究较多,但大多数理论研究并没有应用到实际的原理样机中,因此缺少实测数据作为支撑。本文首先设计实现了一种自适应分布式协同传输协议,该协议通过信道感知技术实时获取信道质量信息,自适应地选择协同节点和协同传输方式。通过将所设计的传输协议实现在自主研发的原理样机上,本文从误码率、丢包率和吞吐量三个性能指标上,分别测试了系统在室内、室外、地面、空中等应用场景下的实际传输性能。测试结果表明,相比于传统点对点直传方式,本文所提的自适应分布式协同传输技术能够显著提升节点间的可靠传输性能,实现分布式多节点的自主协同组网通信。      

Distributive High-Rate Space–Frequency Codes Achieving Full Cooperative and Multipath Diversities for Asynchronous Cooperative Communications

In user-cooperative communications, relay nodes are usually asynchronous. By realizing that the processing in the frequency domain is insensitive to the errors in the time domain, Mei and Shin recently applied the space-time-coded orthogonal frequency-division multiplexing (OFDM) technique to achieve full cooperative diversity for asynchronous cooperative communications, where orthogonal space-time block codes (particularly the Alamouti code) were used for relay nodes. In this paper, we consider asynchronous cooperative communications, and the channels from one node to another node are frequency-selective fading. We propose a high-rate space-frequency coding method and prove that it can achieve both cooperative and multipath diversities. Simulation results are shown to verify the performance of the constructed codes.     

Moving anchor node localization algorithm based on network connectivity

In order to better solve the contradiction between precision of localization and the number of anchor nodes in wireless sensor network,a mobile anchor node localization technology based on connectivity was proposed.First,the coverage characteristic of the network nodes was analyzed,and a critical value was found between the mobile step and the anchor node communication radius,mobile anchor nodes＇ coverage characteristic would change when near this critical value.Second,a mobile anchor node followed a planning path to form a positioning area seamless coverage was used.Finally,when there was no need for high-precision technology,node position would been estimated according with the connectivity of the network and the receiving information of the node.The simulation results show that the proposed algorithm can realize coarse-grained localization,and paths perform complete localization.     

协作通信技术在卫星移动通信中的应用

卫星移动通信信道是典型的衰落信道,其存在的阴影效应、多径效应、多普勒效应给系统性能带来了较大影响,严重时会导致系统通信中断。协作通信技术利用不同节点间的相互协作,可以带来空间分集优势,能够有效对抗信道衰落,提高通信质量。针对协作通信技术在卫星移动通信中的应用,提出了典型的应用思路和方式,并进行了性能仿真与分析。仿真结果表明,将协作通信技术引入卫星移动通信系统,能够有效提升系统的传输性能。     

An algorithm for fast rendezvous seeking of wireless networked robotic systems

The recent development of wireless network architecture and distributed control algorithm allows the onset of large scale robotic application such as monitoring, formation control and flocking, coordination, exploration of unknown environments, and surveillance. In such applications there are many autonomous robots which have capabilities of sensing and acting on the environment and that can communicate with the other robot by wireless communication network defining a Wireless Networked Robotic Systems (in the follows briefly WNR). Usually a robot implements a cooperative algorithm to get some common WNR objective. A widely studied cooperative algorithm allows every robot automatically converge to a common position (consensus or rendezvous) using only local information received from its one hop neighboring robots. Therefore WNR brings together the cooperative control algorithm and the communication capabilities. Despite of a large body of research produced by robotics research community, it is a challenging problem to explore the analysis, the design and evaluation of cooperative algorithm in a more realistic scenario of wireless networked robotic application where the networking and protocol features might affect the overall closed loop WNR performance. In this direction the paper deals with the analysis and design of m-order cooperative control algorithm for fast rendezvous seeking over WNR. Specifically we give a sufficient stability condition of the control algorithm in the presence of heterogeneous time delays affecting the communication through the hops of the WNR. Moreover we analyze the effect of the packet collision phenomena and the presence of background disturbance traffic on the resulting WNR performance. The above sufficient stability condition and analysis, joining with the implementation issues can give a guideline about the design of the rendezvous control algorithm and wireless protocol parameters when we deal with a realistic network environment of WNR. Simulation experiments carried out by a realistic simulation confirm the theoretical findings.     

Movement control algorithms for realization of fault-tolerant ad hoc robot networks

Autonomous and semi-autonomous mobile multirobot systems require a wireless communication network in order to communicate with each other and collaboratively accomplish a given task. A multihop communications network that is self-forming, self-healing, and self-organizing is ideally suited for such mobile robot systems that exist in unpredictable and constantly changing environments. However, since every node in a multihop (or ad hoc) network is responsible for forwarding packets to other nodes, the failure of a critical node can result in a network partition. Hence, it is ideal to have an ad hoc network configuration that can tolerate temporary failures while allowing recovery. Since movement of the robot nodes is controllable, it is possible to achieve such fault-tolerant configurations by moving a subset of robots to new locations. In this article we propose a few simple algorithms for achieving the baseline graph theoretic metric of tolerance to node failures, namely, biconnectivity. We formulate an optimization problem for the creation of a movement plan while minimizing the total distance moved by the robots. For one-dimensional networks, we show that the problem of achieving a biconnected network topology can be formulated as a linear program; the latter lends itself to an optimal polynomial time solution. For two-dimensional networks the problem is much harder, and we propose efficient heuristic approaches for achieving biconnectivity. We compare the performance of the proposed algorithms with each other with respect to the total distance moved metric using simulations.     

Using robot mobility to exploit multipath fading - wireless communications in networked robotics

Communication-aware motion control allows mobile networked robots to increase the average communication throughput. We exploit that in a multipath fading channel, robots can measure the SNR and adapt their motion to spend slightly more time at positions where the channel is good. Two new such cross-layer strategies are analyzed and evaluated: periodic stopping, where the stop duration is a function of the SNR, and controlled stopping, where the robot stops when the communication buffer is filling up. It is shown that the expected average channel capacity can be twice as high as when no cross-layer information is utilized. Experimental evaluation of the strategies confirms the theoretical results.     

多节点协作通信技术研究

为了解决用户节点无法安装多个天线的问题,提出了多节点协作通信技术来形成虚拟的多天线阵列。多节点协作是一种新的空间分集方法,不同节点彼此共享天线并相互转发信息来得到分集增益。通过研究多节点协作通信的关键技术,分析多节点协作的性能增益,指明了多节点协作的发展与应用方向。     

Development trends in robotics

Robotics has been a very fast growing field especially in the last years. In the late 1970s the first industrial applications of stationary unintelligent industrial robots were realised. Since the beginning of the 1990s a new generation of mobile, intelligent, cooperative robots has grown up. This new generation opens new applications areas, e.g. in production automation, in agriculture, in the food industry, in household, for medical and rehabilitation applications, in the entertainment industry as well as for leisure and hobby. Current developing trends are humanoid robots and robots supporting people in everyday life. Other intensive research areas are cooperative robots, bio inspired robots, ubiquitous robots and cloud robots. The following paper is divided into three parts: current state, future development trends as well as visions in robotics.     

Cooperative wireless communications: a cross-layer approach

This article outlines one way to address these problems by using the notion of cooperation between wireless nodes. In cooperative communications, multiple nodes in a wireless network work together to form a virtual antenna array. Using cooperation, it is possible to exploit the spatial diversity of the traditional MIMO techniques without each node necessarily having multiple antennas. Multihop networks use some form of cooperation by enabling intermediate nodes to forward the message from source to destination. However, cooperative communication techniques described in this article are fundamentally different in that the relaying nodes can forward the information fully or in part. Also the destination receives multiple versions of the message from the source, and one or more relays and combines these to obtain a more reliable estimate of the transmitted signal as well as higher data rates. The main advantages of cooperative communications are presented.     

Decentralized formation control for small-scale robot teams with anonymity

This paper presents decentralized formation controls for a team of anonymous mobile robots performing a task through cooperation. Robot teams are required to generate and maintain various geometric patterns adapting to environmental changes in many cooperative robotics applications. In particular, all robots must continue to strive toward achieving the team’s mission even if some members fail to perform their role. Toward this end, formation control approaches are proposed under the conditions that robot teams are initially not allowed to have individual identification numbers (IDs), a predetermined leader, and agreement on coordinate systems. Therefore, all members are required first to reach agreement on their coordinate system and obtain unique IDs for role allocations in a self-organizing way. Then, employing IDs within a common coordinate system, two formation control approaches can be realized: leader-referenced and neighbor-referenced formations. Both approaches are verified using an in-house simulator and physical mobile robots. We detail and evaluate each formation control approach, whose common features include self-organization, robustness, and flexibility.     

基于DF协议的功率分配和伙伴选择策略研究

在无线通信系统中,利用协作通信技术可以获得一定的分集增益,从而有效的提高系统性能。以容量最大化为优化目标,基于DF（解码转发）模式,研究了三节点协作通信中的功率分配与伙伴选择的问题,研究结果表明,当三节点间的信道衰落功率增益满足一定的条件时可以有效的提高系统的容量。     

Overview of networking protocols for underwater wireless communications

Underwater wireless communications can enable many scientific, environmental, commercial, safety, and military applications. Wireless signal transmission is also crucial to remotely control instruments in ocean observatories and to enable coordination of swarms of autonomous underwater vehicles and robots, which will play the role of mobile nodes in future ocean observation networks by virtue of their flexibility and reconfigurability. To make underwater applications viable, efficient communication protocols among underwater devices, which are based on acoustic wireless technology for distances over one hundred meters, must be enabled because of the high attenuation and scattering that affect radio and optical waves, respectively. The unique characteristics of an underwater acoustic channel -- such as very limited and distance-dependent bandwidth, high propagation delays, and timevarying multipath and fading -- require new, efficient and reliable communication protocols to network multiple devices, either static or mobile, potentially over multiple hops. In this article, we provide an overview of recent medium access control, routing, transport, and crosslayer networking protocols.     

Quanta - A platform for rapid control and monitoring of heterogeneous rbots

Rapid prototyping, real-time control and monitoring of various events in robots are crucial requirements for research in the fields of modular and swarm robotics. A large quantities of resources (time, man power, infrastructure, etc.) are often invested in programming, interfacing the sensors, debugging the response to algorithms during prototyping and operational phases of a robot development cycle. The cost of developing an optimal infrastructure to efficiently address such control and monitoring requirements increases significantly in the presence of mobile robots. Though numerous solutions have been developed for minimizing the resources spent on hardware prototyping and algorithm validation in both static and mobile scenarios, it can be observed that researchers have either chosen methodologies that conflict with the power and infrastructure constraints of the research field or generated constrained solutions whose applications are restricted to the field itself. This paper develops a solution for addressing the challenges in controlling heterogeneous mobile robots. A platform named Quanta - a cost effective, energy efficient and high-speed wireless infrastructure is prototyped as a part of the research in the field of modular robotics. Quanta is capable of controlling and monitoring various events in/using a robot with the help of a light-weight communication protocol independent of the robot hardware architecture(s).     

Computationally efficient equalization for asynchronous cooperative communications with multiple frequency offsets

In cooperative communications, time and frequency synchronization is an important issue needed to be addressed in practice. Due to the nature of cooperative communications, multiple frequency offsets may occur and the traditional frequency offset compensations may not apply. For this problem, equalization for the time-varying channel has been used in the literature, where the equalization matrix inverse needs to be retaken every symbol. In this paper, we propose computationally efficient minimum mean square error (MMSE) and MMSE decision feedback equalizers (MMSE-DFE) when multiple frequency offsets are present, where the equalization matrix inverses do not need to be retaken every symbol. Our proposed equalization methods apply to linear convolutively coded cooperative systems, where linear convolutive space-time coding is used to achieve the full cooperative diversity when there are timing errors from the cooperative users or relay nodes, i.e., asynchronous cooperative communication systems.