EasiDEF:一种水平化轻量级物联网数据交换协议

物联网系统中数据交换协议私有化的问题日益突出,异构应用系统之间缺少水平、无缝地交换数据和共享信息的方法.而现有互联网中广泛采用的XML(eXtensible Markup Language)等数据交换协议存在数据冗余和解析复杂的问题,并不适用于资源受限的物联网前端设备.因此文中提出了一种新型的水平化轻量级物联网数据交换协议EasiDEF.该协议根据环境监测类物联网的应用数据特点,将数据类型分为单次请求数据和周期连续上报数据两种常见形式.针对单次出现的数据请求采用三级压缩机制,包括:(1)一种XML文件的序列化方法.该方法基于XML标准设计,保证了数据交换的通用性和水平化.同时序列化的操作使得在低功耗设备中应用XML成为可能;(2)一种将XML文件的字符串标签转化为占用空间小的数值标签的字典映射机制,其中字典的设计面向典型的物联网应用;(3)一种基于LZW(Lempel-Ziv-Welch)的改进数据压缩算法EasiLZW,该算法基于物联网应用字典压缩数据,保证协议的轻量性.而针对周期连续上报数据类型,对连续数据传输提出了一种增量式压缩算法.在保证协议低开销的前提下,EasiDEF可有效压缩XML文件,降低数据传输量.实验结果显示EasiDEF比传统方法提升了5～10倍的压缩效果,能够在物联网的资源受限环境中支持水平化的数据交换.     

A Task Execution Framework for Cloud-Assisted Sensor Networks

As sensor networks are increasingly being deployed, there will be more sensors available in the same region, making it strategic to select the suitable ones to execute users＇ applications. We propose a task execution framework, named sTaskAlloc, to execute application energy efficiently by two main parts. First, considering that the energy consumption of an application is inversely proportional to the utilization rate of sensors, we present a hot sensor selection algorithm, HotTasking, to minimize the energy consumption of new added applications by selecting the most suitable sensor. Second, when a sensor is shared by multiple applications, proposed MergeOPT （a concurrent tasks optimization algorithm） is used to optimize energy consumption further by eliminating redundant sampling tasks. Experimental results show that sTaskAlloc can save more than 76% of energy for new added applications compared with existing methods and reduce up to 72% of sampling tasks when a sensor is shared by more than 10 applications.     

SeaHttp: A Resource-Oriented Protocol to Extend REST Style for Web of Things

Web of Things （WoT） makes it possible to connect tremendous embedded devices to web in Representational State Transfer （REST） style. Some lightweight RESTful protocols have been proposed for the WoT to replace the HTTP protocol running on embedded devices. However, they keep the principal characteristic of the REST style. In particular, they support one-to-one requests in the client-server mode by four standard RESTful methods （GET, PUT, POST, and DELETE）. This characteristic is however inconsistent with the practical networks of embedded devices, which typically perform a group operation. In order to meet the requirement of group communication in the WoT, we propose a resource-oriented protocol called SeaHttp to extend the REST style by introducing two new methods, namely BRANCH and COMBINE respectively. SeaHttp supports parallel processing of group requests by means of splitting and merging them. In addition SeaHttp adds spatiotemporal attributes to the standard URI for naming a dynamic request group of physical resource. Experimental results show that SeaHttp can reduce average energy consumption of group communication in the WoT by 18.5%, compared with the Constrained Application Protocol （CoAP）.     

EasiSMP: A Resource-Oriented Programming Framework Supporting Runtime Propagation of RESTful Resources

In order to simplify programming for building sensor networks, macro-programming methods have been pro- posed in prior work. Most of them are designed for the dedicated networks and specific scenarios where devices are mostly homogeneous. Nevertheless the methods rarely consider those shared networks which are composed of heterogeneous de- vices, e.g., sensors, actuators, mobile devices, and share resources among themselves. In this paper, we present EasiSMP, a resource-oriented programming framework for these shared networks and generic application scenarios. In this framework, the devices and their functionalities are abstracted into RESTful virtual resources （VRs） each of which is labelled by a uni- form resource identifier （URI）. The post-deployment VR can be globally accessed and reused to propagate new resource（s） at runtime. To support the resource propagation, programming primitives are proposed and a virtual resource engine （VRE） is studied. To perform evaluation, EasiSMP is deployed into a relic monitoring network. Experimental results show that programming using Ea-siSMP is concise, and the average deployment overhead is decreased by up to 27% compared with the node-level programming.