技术领域technical field
本发明涉及监测技术和通信技术领域，尤其涉及一种基于AODV路由协议的无线传感器网络按需时钟同步方法。The invention relates to the fields of monitoring technology and communication technology, in particular to an on-demand clock synchronization method for a wireless sensor network based on the AODV routing protocol.
背景技术Background technique
无线传感器网络是由随机布置在监测区域内的大量传感器节点通过短距无线通信形成的分布式自治网络系统。节点间相互协作完成物理信息的感知、采集、传输以及其他特定任务。通过基站等设备，无线传感器网络还可以与因特网和移动通信网等现有的网络连接，实现物理目标的远程监测。无线传感器网络从组网到配置、管理和运行都是由传感器节点相互协作完成，基本不需要人的干预和基础网络设施的辅助，因此在实现方式上具有快捷性和灵活性。与传统的传感器技术相比，无线传感器网络能够布置在更大范围的监测区域中，获取具有更高空间分辨率和更高时间分辨率的数据，因此在军事、工业、农业、环境监测、医药卫生、智能家居和智能交通领域具有广阔的应用前景。Wireless sensor network is a distributed autonomous network system formed by a large number of sensor nodes randomly arranged in the monitoring area through short-distance wireless communication. Nodes cooperate with each other to complete the perception, collection, transmission and other specific tasks of physical information. Through equipment such as base stations, wireless sensor networks can also be connected to existing networks such as the Internet and mobile communication networks to realize remote monitoring of physical targets. The wireless sensor network from networking to configuration, management and operation is completed by the cooperation of sensor nodes, which basically does not require human intervention and the assistance of basic network facilities, so the implementation method is fast and flexible. Compared with traditional sensor technology, wireless sensor networks can be deployed in a larger monitoring area to obtain data with higher spatial resolution and higher time resolution, so in military, industrial, agricultural, environmental monitoring, medical Sanitation, smart home and smart transportation have broad application prospects.
在无线传感器网络这样的分布式系统中，并没有全局时钟来为地理位置分散的传感器节点提供统一的时间基准，节点对时间的认知来至于各维护的本地时钟。由于节点本地时钟的计时速率快慢不一，在同一时刻，不同节点的本地时间值不尽相同。无线传感器网络时钟同步技术是使无线传感器网络中各节点对时间的认知达到并保持一致。In a distributed system such as a wireless sensor network, there is no global clock to provide a unified time reference for geographically dispersed sensor nodes, and the nodes' cognition of time comes from the local clocks maintained by each node. Because the timing rate of the local clock of the node is different, at the same moment, the local time values of different nodes are not the same. The wireless sensor network clock synchronization technology is to make each node in the wireless sensor network realize and maintain the same cognition of time.
无线传感器网络的时钟同步需求来至于两方面：The clock synchronization requirements of wireless sensor networks come from two aspects:
1.与数据相关的应用，如数据压缩融合、测距定位、波束成型以及目标跟踪等。这一类应用利用数据的时间相关性剔除冗余的数据以减少通信量，或根据采集时间来确定不同节点的数据间的时序关系，以便融合多节点的观测数据来提取高层次的物理量信息。实现节点的时钟同步是实施这些应用的前提条件，而且时钟同步精度会对他们的性能产生关键性的影响。1. Data-related applications, such as data compression and fusion, ranging and positioning, beamforming, and target tracking. This type of application uses the time correlation of data to eliminate redundant data to reduce communication traffic, or determines the timing relationship between data of different nodes according to the collection time, so as to fuse observation data of multiple nodes to extract high-level physical quantity information. Realizing clock synchronization of nodes is a prerequisite for implementing these applications, and the accuracy of clock synchronization will have a critical impact on their performance.
2.与协作相关的应用，如节点周期性睡眠-唤醒调度机制、协作传输以及安全协议等。这一类应用利用节点间的协作来优化网络性能或弥补传感器硬件功能的不足，这些应用也要求节点间实现并保持时钟同步。2. Applications related to cooperation, such as node periodic sleep-wake scheduling mechanism, cooperative transmission and security protocols, etc. This type of application utilizes the cooperation between nodes to optimize network performance or compensate for the lack of sensor hardware capabilities. These applications also require the synchronization of clocks between nodes.
目前，多数基于无线传感器网络的监测系统采用ZigBee协议标准构建，ZigBee是基于IEEE802.15.4标准的低功耗局域网协议。根据国际标准规定，ZigBee技术是一种短距离、低功耗的无线通信技术。其特点是近距离、低复杂度、自组织、低功耗、高数据速率。ZigBee技术主要适合于主要适用于广域环境的监测，自动控制和远程控制等领域，能够方便的与各种设备集成。At present, most monitoring systems based on wireless sensor networks are built using the ZigBee protocol standard. ZigBee is a low-power LAN protocol based on the IEEE802.15.4 standard. According to international standards, ZigBee technology is a short-distance, low-power wireless communication technology. It is characterized by close range, low complexity, self-organization, low power consumption, and high data rate. ZigBee technology is mainly suitable for the monitoring, automatic control and remote control of wide-area environment, and can be easily integrated with various devices.
尽管应用ZigBee技术构建无线传感器网络具有诸多优势，但由于其没有涉及有效的时钟同步算法，因此基于ZigBee协议构建的无线传感器网络中，各传感器节点采集的数据在时间标记上相对于标准时钟会有较大的偏差，因此限制了其在高精度时间标记的监测系统中的应用。Although the application of ZigBee technology to build a wireless sensor network has many advantages, because it does not involve an effective clock synchronization algorithm, in a wireless sensor network based on the ZigBee protocol, the data collected by each sensor node will have different time stamps relative to the standard clock. The larger deviation thus limits its application in monitoring systems with high precision time stamping.
近年来，研究人员针对无线传感器网络，已提出多种时钟同步算法。这些算法大致可分为三类：（1）基于发送者的同步模型， 典型算法有基于时延测量的DMTS 算法和基于洪泛的FTSP 算法；（2）基于发送者-接收者交互的同步模型，典型的是TPSN 算法；（3）基于发送者-接收者交互的同步模型，典型的是RBS 算法和Adaptive RBS 算法。纵观现有的这些算法及其它一些相关算法，我们可以发现它们都是以实现无线传感器网络全网高精度时钟同步为目标。考虑到实际的应用需求，一些实际的系统并不要求实现无线传感器网络的全网时钟同步，全网时钟同步过程在网络运行过程中略显繁琐，不仅增加了网络的通信开销，而且会降低数据分组的投递率。另外，这些算法都没有与现有的通信协议标准进行整合，因此在实际应用中具有局限性。In recent years, researchers have proposed a variety of clock synchronization algorithms for wireless sensor networks. These algorithms can be roughly divided into three categories: (1) Sender-based synchronization models, typical algorithms include DMTS algorithm based on delay measurement and FTSP algorithm based on flooding; (2) Synchronization model based on sender-receiver interaction , typically TPSN algorithm; (3) Synchronization model based on sender-receiver interaction, typically RBS algorithm and Adaptive RBS algorithm. Looking at these existing algorithms and some other related algorithms, we can find that they are all aimed at realizing high-precision clock synchronization of the entire wireless sensor network. Considering the actual application requirements, some actual systems do not require the whole network clock synchronization of the wireless sensor network. The whole network clock synchronization process is a bit cumbersome during the network operation, which not only increases the communication overhead of the network, but also reduces the data The delivery rate of the packet. In addition, these algorithms are not integrated with existing communication protocol standards, so they have limitations in practical applications.
在基于无线传感器网络技术的监测系统中，一方面由于传感器节点采用的晶振在生产工艺上存在差异，而节点的自身时钟由晶振提供，因此当网络长时间运行时，各节点的时钟将会逐渐产生差异；另一方面，由于无线传感器网络是一种分布式的网络，各节点在监测场景中分布式的布置，实际工程应用中很难保证节点启动的同步性，当系统投入到监测任务时，节点启动时刻的差异性会使各节点的时钟呈现出不同的初相位；此外，考虑到网络的可扩展性时，网络允许新的传感器节点能够随时加入，这些新的传感器节点无论在时钟频率和时钟的初相位方面与原有网络同样存在着差异。由以上因素导致的无线传感器网络各节点的时钟差异会使其采集的数据在时间标记上具有较大的偏差，这对于侧重于采样时间精度的基于无线传感器网络是不允许的。在实际应用中，主流的基于无线传感器网络的监测系统多数采用ZigBee协议构建，ZigBee协议的PHY层和MAC层采用IEEE802.15.4标准，网络层采用简化的AODV路由协议（jrAODV）。无论是IEEE802.15.4还是AODV路由协议均没有涉及多跳时钟同步功能。针对ZigBee协议在时钟同步功能方面的缺陷，本发明为无线传感器网络监测系统提供了一种基于AODV路由协议的按需时钟同步技术。In the monitoring system based on wireless sensor network technology, on the one hand, due to the difference in the production process of the crystal oscillator used by the sensor nodes, and the node's own clock is provided by the crystal oscillator, when the network runs for a long time, the clock of each node will gradually On the other hand, since the wireless sensor network is a distributed network, each node is arranged in a distributed manner in the monitoring scene, it is difficult to ensure the synchronization of node startup in actual engineering applications, when the system is put into monitoring tasks , the difference in the starting time of the nodes will cause the clocks of each node to show different initial phases; in addition, considering the scalability of the network, the network allows new sensor nodes to join at any time, regardless of the clock frequency of these new sensor nodes There are also differences in the initial phase of the clock and the original network. The clock difference of each node of the wireless sensor network caused by the above factors will make the collected data have a large deviation in the time stamp, which is not allowed for wireless sensor networks that focus on sampling time accuracy. In practical applications, most of the mainstream monitoring systems based on wireless sensor networks are constructed using the ZigBee protocol. The PHY layer and MAC layer of the ZigBee protocol adopt the IEEE802.15.4 standard, and the network layer adopts the simplified AODV routing protocol (jrAODV). Neither IEEE802.15.4 nor AODV routing protocol involves multi-hop clock synchronization function. Aiming at the defects of ZigBee protocol in clock synchronization function, the present invention provides an on-demand clock synchronization technology based on AODV routing protocol for wireless sensor network monitoring system.
发明内容Contents of the invention
本发明的目的是提供一种基于AODV路由协议的无线传感器网络按需时钟同步方法，能够解决监测任务中各节点所采集的数据在时间标记上具有较大偏差的问题，避免无线传感器网络中节点之间不必要的同步过程，从而降低时钟同步过程对于通信的开销，使网络的性能有较好的提升。The purpose of the present invention is to provide a wireless sensor network on-demand clock synchronization method based on the AODV routing protocol, which can solve the problem that the data collected by each node in the monitoring task has a large deviation in the time stamp, and avoid nodes in the wireless sensor network. The unnecessary synchronization process between them reduces the communication overhead of the clock synchronization process and improves the performance of the network.
本发明采用的技术方案为：The technical scheme adopted in the present invention is:
基于AODV路由协议的无线传感器网络按需时钟同步方法，包括以下步骤：An on-demand clock synchronization method for wireless sensor networks based on the AODV routing protocol, comprising the following steps:
A：首先在AODV路由协议的原始数据结构中增加新的数据项，包括如下部分：A: First, add new data items in the original data structure of the AODV routing protocol, including the following parts:
A1：在路由表项中增加变量 作为源节点和目的节点之间的时钟偏差估计，的类型为双精度浮点型；A1: Add variables in routing table entries As the clock skew estimate between source and destination nodes, The type of is a double-precision floating-point type;
A2：在路由表项中增加变量作为源节点和目的节点之间的传输延时估计，的类型为双精度浮点类型；A2: Add variables in routing table entries As an estimate of the transmission delay between the source node and the destination node, The type of is a double-precision floating-point type;
A3：在路由表项中增加变量作为源节点和目的节点是否完成同步的标志，的类型为布尔型；A3: Add variables in routing table entries As a sign of whether the source node and the destination node have completed synchronization, is of type Boolean;
其中，所述的路由表项为保存有源节点到目的节点的路径信息的数据结构；所述的源节点是指发送数据的传感器节点，同时作为待完成时钟同步的传感器节点；所述的目的节点为接收数据的传感器节点，同时作为具有标准时钟的传感器节点；Wherein, the routing entry is a data structure that saves the path information from the source node to the destination node; the source node refers to the sensor node that sends data, and at the same time serves as the sensor node to be clock synchronized; the purpose The node is a sensor node that receives data and acts as a sensor node with a standard clock at the same time;
B：在原始AODV协议定义的命令分组的基础上，增加时钟同步功能需求的字段，包括如下部分：B: On the basis of the command packet defined by the original AODV protocol, the fields required for the clock synchronization function are added, including the following parts:
B1：在原有的路径发现命令RREQ分组定义的基础上，增加源节点的本地时钟标记字段Source Time Stamp，Source Time Stamp的数据类型为双精度浮点类型；B1: On the basis of the original path discovery command RREQ packet definition, add the source node's local clock tag field Source Time Stamp, and the data type of Source Time Stamp is double-precision floating point type;
B2：在原有的路径响应命令RREP分组定义的基础上，增加前向传输时延字段Forward Transmission Delay，Forward Transmission Delay的数据类型为双精度浮点类型；B2: On the basis of the original path response command RREP packet definition, add the forward transmission delay field Forward Transmission Delay, and the data type of Forward Transmission Delay is double-precision floating point type;
B3：在原有的路径响应命令RREP分组定义的基础上，增加目的节点的本地时钟标记字段Destination Time Stamp，Destination Time Stamp的数据类型为双精度浮点类型；B3: On the basis of the original path response command RREP packet definition, add the local clock mark field Destination Time Stamp of the destination node, and the data type of Destination Time Stamp is double-precision floating-point type;
其中，所述的AODV协议定义的命令分组是指AODV协议为完成源节点到目的节点之间的路径发现过程以及路径维护过程定义的数据包的类型，包括RREQ分组和RREP分组；Wherein, the command packet defined by the AODV protocol refers to the type of data packet defined by the AODV protocol for completing the path discovery process between the source node and the destination node and the path maintenance process, including RREQ packets and RREP packets;
C：基于步骤A和步骤B定义的新的数据结构，进行时钟同步算法的执行；C: Execute the clock synchronization algorithm based on the new data structure defined in step A and step B;
C1：源节点在本地时钟读数为时刻构建RREQ命令，并令RREQ命令的Source Time Stamp字段等于，而后，源节点广播发送RREQ命令，在网络中搜寻目的节点；C1: The local clock of the source node reads Build the RREQ command at all times, and make the Source Time Stamp field of the RREQ command equal to , and then, the source node broadcasts and sends the RREQ command to search for the destination node in the network;
C2：由于步骤C1中源节点广播发送RREQ命令，所以，RREQ命令分为两种情况被接收：一种是：中间节点；另一种是：目的节点；所述的中间节点是指网络中除源节点和目的节点之外的其他传感器节点；C2: Since the source node broadcasts and sends the RREQ command in step C1, the RREQ command is received in two cases: one is: the intermediate node; the other is: the destination node; the intermediate node refers to the network except Other sensor nodes other than the source node and the destination node;
C2.1：当中间节点接收到来自源节点发送的RREQ命令时，首先判断在规定的时间间隔内是否为首次接收来自源节点的RREQ命令；C2.1: When the intermediate node receives the RREQ command sent from the source node, it first judges whether it is the first time to receive the RREQ command from the source node within the specified time interval;
若中间节点接收过来自源节点的RREQ命令，则立即丢弃该RREQ命令；If the intermediate node has received the RREQ command from the source node, it will immediately discard the RREQ command;
若中间节点未接收过来自源节点的RREQ命令，则建立到该源节点的反向路由，并设置路由表项中变量的值为FALSE，表明该中间节点虽然与源节点之间建立了可用路径，但未实现与该源节点的时钟同步，而后中间节点继续广播该RREQ命令；If the intermediate node has not received the RREQ command from the source node, then establish a reverse route to the source node, and set the variables in the routing table entry The value of is FALSE, indicating that although the intermediate node has established an available path with the source node, it has not achieved clock synchronization with the source node, and then the intermediate node continues to broadcast the RREQ command;
C2.2：当目的节点接收到来自源节点的RREQ命令时，首先根据本地时钟记录目的节点接收到RREQ命令的时刻为；而后建立目的节点到源节点的反向路由，并设置路由表项中变量的值为FALSE；表明目的节点虽然建立了到源节点的路径，但未实现与源节点的时钟同步；最后目的节点在本地时钟读数为的时刻构建RREP命令并发送至源节点，在构建RREP命令的过程中，令RREP命令的Forward Transmission Delay字段等于，Destination Time Stamp字段等于；C2.2: When the destination node receives the RREQ command from the source node, first record the time when the destination node receives the RREQ command according to the local clock as ; Then establish the reverse route from the destination node to the source node, and set the variable in the routing table item The value of is FALSE; it indicates that although the destination node has established a path to the source node, it has not realized the clock synchronization with the source node; finally, the local clock reading of the destination node is Build the RREP command at the moment and send it to the source node. During the process of building the RREP command, the Forward Transmission Delay field of the RREP command is equal to , the Destination Time Stamp field is equal to ;
C3：源节点在本地时钟读数为的时刻接收到来自目的节点的RREP命令时；C3: The source node's local clock reads When receiving the RREP command from the destination node at the time of ;
C3.1：首先建立到目的节点的路由，将路径信息写入相应的路由表项；C3.1: First establish a route to the destination node, and write the route information into the corresponding routing table entry;
C3.2：根据公式⑴推导出源节点和目的节点之间的时钟偏差估计和源节点和目的节点之间的传输时延估计，时钟偏差估计如公式⑵，传输时延估计如公式⑶所示，公式⑴如下：C3.2: Deduce the clock skew estimate between the source node and the destination node according to formula (1) and the transmission delay estimation between the source node and the destination node , the clock skew estimate Such as formula (2), transmission delay estimation As shown in formula (3), formula (1) is as follows:
⑴ ⑴
推导出的公式⑵如下：The derived formula (2) is as follows:
⑵ ⑵
推导出的公式⑶如下：The derived formula (3) is as follows:
⑶ (3)
C3.3：将时钟偏差估计和传输时延估计写入路由表项，并设置路由表项中变量的值为TRUE；表明源节点到目的节点的时钟同步参数有效；C3.3: Estimating clock skew and transmission delay estimation Write the routing table entry and set the variables in the routing table entry The value of is TRUE; it indicates that the clock synchronization parameters from the source node to the destination node are valid;
C4：当需要进行数据传输时，执行时钟校准函数公式⑷，实现源节点到目的节点的时钟同步，公式⑷如下：C4: When data transmission is required, implement the clock calibration function formula (4) to realize clock synchronization from the source node to the destination node. The formula (4) is as follows:
⑷ ⑷
D：当中间节点在时刻接收到来自源节点的RREQ命令，假设此时该中间节点已经包含了到目的节点的路径信息以及时钟同步参数和时，对步骤C的时钟同步算法进行开销优化；D: When the intermediate node is in Receive the RREQ command from the source node at any time, assuming that the intermediate node already contains the path information and clock synchronization parameters to the destination node at this time and When , optimize the cost of the clock synchronization algorithm in step C;
D1：依据步骤B2和步骤B3所述RREP命令中包含有前向传输时延字段Forward Transmission Delay和目的节点的本地时钟标记字段Destination Time Stamp，因此可以利用中间节点与目的节点的时钟同步参数和进行计算，得出源节点到目的节点的前向传输时延字段Forward Transmission Delay和本地时钟标记字段Destination Time Stamp，计算方法依据公式(5)和公式(6)；D1: According to step B2 and step B3, the RREP command contains the forward transmission delay field Forward Transmission Delay and the local clock mark field of the destination node Destination Time Stamp, so the clock synchronization parameters of the intermediate node and the destination node can be used and Calculate to obtain the forward transmission delay field Forward Transmission Delay and the local clock mark field Destination Time Stamp from the source node to the destination node, and the calculation method is based on formula (5) and formula (6);
⑸ (5)
⑹ ⑹
D2：中间节点在本地节点时钟读数的时刻发送RREP命令至源节点；D2: intermediate node clock reading at local node Send the RREP command to the source node at the moment of ;
D3：源节点在本地节点时钟读数的时刻接收来自中间节点的RREP命令，建立到目的节点的路径，并依据公式(2)和公式(3)计算与目的节点的时钟同步参数和，从而实现与目的节点的时钟同步，并达到时钟同步算法的开销优化。D3: source node clock reading at local node Receive the RREP command from the intermediate node at the moment, establish the path to the destination node, and calculate the clock synchronization parameters with the destination node according to formula (2) and formula (3) and , so as to realize the clock synchronization with the destination node, and achieve the overhead optimization of the clock synchronization algorithm.
本发明直接将时钟同步算法与AODV协议的路径发现算法整合，AODV路由协议本身是一种按需路由协议，因此基于AODV路由协议的时钟同步算法是一种按需时钟同步算法，可以按照节点自身的需求，实现与目标节点的时钟同步，时钟同步不再局限于以全网同步的方式实现。The present invention directly integrates the clock synchronization algorithm with the path discovery algorithm of the AODV protocol. The AODV routing protocol itself is an on-demand routing protocol, so the clock synchronization algorithm based on the AODV routing protocol is an on-demand clock synchronization algorithm. According to the requirements, the clock synchronization with the target node is realized, and the clock synchronization is no longer limited to the realization of the whole network synchronization.
时钟同步算法基于源节点和目的节点的直接交互进行实现，中间节点不再参与时钟同步计算，因此可以克服时钟同步偏差的逐跳累计，提高了多跳时钟同步的精度。The clock synchronization algorithm is implemented based on the direct interaction between the source node and the destination node, and the intermediate node no longer participates in the clock synchronization calculation, so it can overcome the hop-by-hop accumulation of clock synchronization deviation and improve the accuracy of multi-hop clock synchronization.
时钟同步算法通过AODV协议的路径发现过程实现，不再需要额外的诸如生成树的计算过程，因此相比较传统的技术，本项时钟同步技术在通讯开销方面具有不可比拟的优势。The clock synchronization algorithm is realized through the path discovery process of the AODV protocol, and no additional calculation process such as spanning tree is needed. Therefore, compared with the traditional technology, this clock synchronization technology has incomparable advantages in terms of communication overhead.
利用中间节点已有的时钟同步信息，一方面可以实现时钟同步算法通信开销的进一步优化，另一方面在拓扑结构快速变化的网络中，可以加快时钟同步算法的计算速度，实现节点与目标节点的快速同步，因此该项技术能够较好的适应拓扑结构快速变化的网络。Utilizing the existing clock synchronization information of intermediate nodes, on the one hand, the further optimization of the communication overhead of the clock synchronization algorithm can be realized; Fast synchronization, so this technology can better adapt to networks with rapidly changing topology.
AODV路由协议作为较成熟的无线传感器网络路由协议，已广泛应用在目前主流的基于无线传感器网络的监测系统中，本项技术以AODV路由协议为基础进行实现，因此具有较好的可集成性，易于在现有的硬件平台中集成。As a mature wireless sensor network routing protocol, the AODV routing protocol has been widely used in the current mainstream monitoring systems based on wireless sensor networks. This technology is implemented based on the AODV routing protocol, so it has good integrability. Easy to integrate in existing hardware platforms.
附图说明Description of drawings
图1为本发明基于AODV路由协议的按需时钟同步算法流程；Fig. 1 is the on-demand clock synchronization algorithm process based on the AODV routing protocol of the present invention;
图2为本发明的基于AODV路由协议按需时钟同步过程；Fig. 2 is the on-demand clock synchronization process based on the AODV routing protocol of the present invention;
图3为本发明基于接收者-发送者模型的时钟同步算法原理；Fig. 3 is the clock synchronization algorithm principle based on receiver-sender model of the present invention;
图4为本发明具有时钟同步功能的AODV协议路由表项结构图；Fig. 4 is the structural diagram of the AODV protocol routing entry with clock synchronization function in the present invention;
图5为本发明具有时钟同步功能的AODV协议RREQ命令结构；Fig. 5 is the AODV protocol RREQ command structure with clock synchronization function of the present invention;
图6为本发明具有时钟同步功能的AODV协议RREP命令结构；Fig. 6 is the AODV protocol RREP command structure with clock synchronization function of the present invention;
图7为本发明利用中间节点优化时钟同步算法的通信开销图；FIG. 7 is a communication overhead diagram of the present invention utilizing an intermediate node to optimize a clock synchronization algorithm;
图8为本发明应用于监测系统的结构图。Fig. 8 is a structural diagram of the present invention applied to a monitoring system.
具体实施方式Detailed ways
如图1和图2所示，本发明包括以下步骤：As shown in Figure 1 and Figure 2, the present invention comprises the following steps:
A：首先在AODV路由协议的原始数据结构中增加新的数据项，包括如下部分：A: First, add new data items in the original data structure of the AODV routing protocol, including the following parts:
A1：在路由表项中增加变量作为源节点和目的节点之间的时钟偏差估计，的类型为双精度浮点型；A1: Add variables in routing table entries As the clock skew estimate between source and destination nodes, The type of is a double-precision floating-point type;
A2：在路由表项中增加变量作为源节点和目的节点之间的传输延时估计，的类型为双精度浮点类型；A2: Add variables in routing table entries As an estimate of the transmission delay between the source node and the destination node, The type of is a double-precision floating-point type;
A3：在路由表项中增加变量作为源节点和目的节点是否完成同步的标志，的类型为布尔型；A3: Add variables in routing table entries As a sign of whether the source node and the destination node have completed synchronization, is of type Boolean;
其中，所述的路由表项为保存有源节点到目的节点的路径信息的数据结构；所述的源节点是指发送数据的传感器节点，同时作为待完成时钟同步的传感器节点；所述的目的节点为接收数据的传感器节点，同时作为具有标准时钟的传感器节点；Wherein, the routing entry is a data structure that saves the path information from the source node to the destination node; the source node refers to the sensor node that sends data, and at the same time serves as the sensor node to be clock synchronized; the purpose The node is a sensor node that receives data and acts as a sensor node with a standard clock at the same time;
B：在原始AODV协议定义的命令分组的基础上，增加时钟同步功能需求的字段，包括如下部分：B: On the basis of the command packet defined by the original AODV protocol, the fields required for the clock synchronization function are added, including the following parts:
B1：在原有的路径发现命令RREQ分组定义的基础上，增加源节点的本地时钟标记字段Source Time Stamp，Source Time Stamp的数据类型为双精度浮点类型；B1: On the basis of the original path discovery command RREQ packet definition, add the source node's local clock tag field Source Time Stamp, and the data type of Source Time Stamp is double-precision floating point type;
B2：在原有的路径响应命令RREP分组定义的基础上，增加前向传输时延字段Forward Transmission Delay，Forward Transmission Delay的数据类型为双精度浮点类型；B2: On the basis of the original path response command RREP packet definition, add the forward transmission delay field Forward Transmission Delay, and the data type of Forward Transmission Delay is double-precision floating point type;
B3：在原有的路径响应命令RREP分组定义的基础上，增加目的节点的本地时钟标记字段Destination Time Stamp，Destination Time Stamp的数据类型为双精度浮点类型；B3: On the basis of the original path response command RREP packet definition, add the local clock mark field Destination Time Stamp of the destination node, and the data type of Destination Time Stamp is double-precision floating-point type;
其中，所述的AODV协议定义的命令分组是指AODV协议为完成源节点到目的节点之间的路径发现过程以及路径维护过程定义的数据包的类型，包括RREQ分组和RREP分组；Wherein, the command packet defined by the AODV protocol refers to the type of data packet defined by the AODV protocol for completing the path discovery process between the source node and the destination node and the path maintenance process, including RREQ packets and RREP packets;
C：基于步骤A和步骤B定义的新的数据结构，进行时钟同步算法的执行；C: Execute the clock synchronization algorithm based on the new data structure defined in step A and step B;
C1：源节点在本地时钟读数为时刻构建RREQ命令，并令RREQ命令的Source Time Stamp字段等于，而后，源节点广播发送RREQ命令，在网络中搜寻目的节点；C1: The local clock of the source node reads Build the RREQ command at all times, and make the Source Time Stamp field of the RREQ command equal to , and then, the source node broadcasts and sends the RREQ command to search for the destination node in the network;
C2：由于步骤C1中源节点广播发送RREQ命令，所以，RREQ命令分为两种情况被接收：一种是：中间节点；另一种是：目的节点；所述的中间节点是指网络中除源节点和目的节点之外的其他传感器节点；C2: Since the source node broadcasts and sends the RREQ command in step C1, the RREQ command is received in two cases: one is: the intermediate node; the other is: the destination node; the intermediate node refers to the network except Other sensor nodes other than the source node and the destination node;
C2.1：当中间节点接收到来自源节点发送的RREQ命令时，首先判断在规定的时间间隔内是否为首次接收来自源节点的RREQ命令；C2.1: When the intermediate node receives the RREQ command sent from the source node, it first judges whether it is the first time to receive the RREQ command from the source node within the specified time interval;
若中间节点接收过来自源节点的RREQ命令，则立即丢弃该RREQ命令；If the intermediate node has received the RREQ command from the source node, it will immediately discard the RREQ command;
若中间节点未接收过来自源节点的RREQ命令，则建立到该源节点的反向路由，并设置路由表项中变量的值为FALSE，表明该中间节点虽然与源节点之间建立了可用路径，但未实现与该源节点的时钟同步，而后中间节点继续广播该RREQ命令；If the intermediate node has not received the RREQ command from the source node, then establish a reverse route to the source node, and set the variables in the routing table entry The value of is FALSE, indicating that although the intermediate node has established an available path with the source node, it has not achieved clock synchronization with the source node, and then the intermediate node continues to broadcast the RREQ command;
C2.2：当目的节点接收到来自源节点的RREQ命令时，首先根据本地时钟记录目的节点接收到RREQ命令的时刻为；而后建立目的节点到源节点的反向路由，并设置路由表项中变量的值为FALSE；表明目的节点虽然建立了到源节点的路径，但未实现与源节点的时钟同步；最后目的节点在本地时钟读数为的时刻构建RREP命令并发送至源节点，在构建RREP命令的过程中，令RREP命令的Forward Transmission Delay字段等于，Destination Time Stamp字段等于；C2.2: When the destination node receives the RREQ command from the source node, first record the time when the destination node receives the RREQ command according to the local clock as ; Then establish the reverse route from the destination node to the source node, and set the variable in the routing table item The value of is FALSE; it indicates that although the destination node has established a path to the source node, it has not realized the clock synchronization with the source node; finally, the local clock reading of the destination node is Build the RREP command at the moment and send it to the source node. During the process of building the RREP command, the Forward Transmission Delay field of the RREP command is equal to , the Destination Time Stamp field is equal to ;
C3：源节点在本地时钟读数为的时刻接收到来自目的节点的RREP命令时；C3: The source node's local clock reads When receiving the RREP command from the destination node at the time of ;
C3.1：首先建立到目的节点的路由，将路径信息写入相应的路由表项；C3.1: First establish a route to the destination node, and write the route information into the corresponding routing table entry;
C3.2：根据公式⑴推导出源节点和目的节点之间的时钟偏差估计和源节点和目的节点之间的传输时延估计，时钟偏差估计如公式⑵，传输时延估计如公式⑶所示，公式⑴如下：C3.2: Deduce the clock skew estimate between the source node and the destination node according to formula (1) and the transmission delay estimation between the source node and the destination node , the clock skew estimate Such as formula (2), transmission delay estimation As shown in formula (3), formula (1) is as follows:
⑴ ⑴
推导出的公式⑵如下：The derived formula (2) is as follows:
⑵ ⑵
推导出的公式⑶如下：The derived formula (3) is as follows:
⑶ (3)
C3.3：将时钟偏差估计和传输时延估计写入路由表项，并设置路由表项中变量的值为TRUE；表明源节点到目的节点的时钟同步参数有效；C3.3: Estimating clock skew and transmission delay estimation Write the routing table entry and set the variables in the routing table entry The value of is TRUE; it indicates that the clock synchronization parameters from the source node to the destination node are valid;
C4：当需要进行数据传输时，执行时钟校准函数公式⑷，实现源节点到目的节点的时钟同步，公式⑷如下：C4: When data transmission is required, implement the clock calibration function formula (4) to realize clock synchronization from the source node to the destination node. The formula (4) is as follows:
⑷ ⑷
D：当中间节点在时刻接收到来自源节点的RREQ命令，假设此时该中间节点已经包含了到目的节点的路径信息以及时钟同步参数和时，对步骤C的时钟同步算法进行开销优化；D: When the intermediate node is in Receive the RREQ command from the source node at any time, assuming that the intermediate node already contains the path information and clock synchronization parameters to the destination node at this time and When , optimize the cost of the clock synchronization algorithm in step C;
D1：依据步骤B2和步骤B3所述RREP命令中包含有前向传输时延字段Forward Transmission Delay和目的节点的本地时钟标记字段Destination Time Stamp，因此可以利用中间节点与目的节点的时钟同步参数和进行计算，得出源节点到目的节点的前向传输时延字段Forward Transmission Delay和本地时钟标记字段Destination Time Stamp，计算方法依据公式(5)和公式(6)；D1: According to the RREP command described in step B2 and step B3, the forward transmission delay field Forward Transmission Delay and the local clock mark field Destination Time Stamp of the destination node are included, so the clock synchronization parameters of the intermediate node and the destination node can be used and Carry out the calculation to obtain the forward transmission delay field Forward Transmission Delay and the local clock mark field Destination Time Stamp from the source node to the destination node, and the calculation method is based on formula (5) and formula (6);
⑸ (5)
⑹ ⑹
D2：中间节点在本地节点时钟读数的时刻发送RREP命令至源节点；D2: intermediate node clock reading at local node Send the RREP command to the source node at the moment of ;
D3：源节点在本地节点时钟读数的时刻接收来自中间节点的RREP命令，建立到目的节点的路径，并依据公式(2)和公式(3)计算与目的节点的时钟同步参数和，从而实现与目的节点的时钟同步，并达到时钟同步算法的开销优化。D3: source node clock reading at local node Receive the RREP command from the intermediate node at the moment, establish the path to the destination node, and calculate the clock synchronization parameters with the destination node according to formula (2) and formula (3) and , so as to realize the clock synchronization with the destination node, and achieve the overhead optimization of the clock synchronization algorithm.
下面结合附图和实例图，对本发明的技术方案作进一步的详细描述。本实例在以本发明技术方案为前提下进行实施,给出了详细的实施方案和具体的操作过程,但本发明的保护范围不限于下述的实施例。The technical scheme of the present invention will be further described in detail below in conjunction with the accompanying drawings and example diagrams. This example is carried out on the premise of the technical solution of the present invention, and a detailed implementation plan and specific operation process are provided, but the protection scope of the present invention is not limited to the following examples.
本实施例应用于无线传感器网络搭建的监测系统中，本系统的结构如图8所示，上位机的硬件部分采用工控机实现，软件部分由VC++结合SQL-Sever数据库搭建。上位机作为人机交互系统与无线传感器网络的交互需要借助网关实现，本系统中，网关同时作为无线传感器网络的汇聚节点与其他的传感器节点构成整个无线传感器网络。This embodiment is applied to a monitoring system built by a wireless sensor network. The structure of this system is shown in Figure 8. The hardware part of the upper computer is realized by an industrial computer, and the software part is built by VC++ combined with a SQL-Sever database. As a human-computer interaction system, the host computer needs to use the gateway to realize the interaction with the wireless sensor network. In this system, the gateway also serves as the convergence node of the wireless sensor network and forms the entire wireless sensor network with other sensor nodes.
无线传感器网络中，主控芯片采用TI公司MSP430微处理器，无线射频芯片采用TI公司的CC2420，CC2420通过SPI接口与MSP430通信，CC2420能够完美的支持IEEE802.15.4协议标准，应用2.4GHz频段，实现无线通信。按照IEEE802.15.4协议标准，在MSP430实现通信协议的MAC层部分，另外将AODV协议栈写入MSP430的FLASH中。In the wireless sensor network, the main control chip adopts TI's MSP430 microprocessor, and the wireless radio frequency chip adopts TI's CC2420. CC2420 communicates with MSP430 through the SPI interface. CC2420 can perfectly support the IEEE802.15.4 protocol standard and apply 2.4GHz frequency band to realize Wireless communication. According to the IEEE802.15.4 protocol standard, the MAC layer part of the communication protocol is realized in the MSP430, and the AODV protocol stack is written into the FLASH of the MSP430.
首先，结合图3，时钟同步模型采用发送者-接收者的交互模型，说明公式⑴、公式⑵、公式⑶和公式⑷的由来：First, in combination with Figure 3, the clock synchronization model adopts a sender-receiver interaction model to explain the origin of formula ⑴, formula ⑵, formula ⑶ and formula 4:
a)节点1在本地时钟读数为T1的时刻发送探测信息给节点2，探测信息中包含节点1的本地时钟读数T1；节点1作为源节点，节点2作为目的节点；a) Node 1 sends detection information to node 2 when the local clock reading is T1 , and the detection information includes the local clock reading T1 of node 1; node 1 is used as a source node, and node 2 is used as a destination node;
b)节点2在本地时钟读数为T2的时刻接收到节点1的探测信息后存储并处理；此时， ，其中，表示从节点1传输到节点2的传输延时估计，表示节点1和节点2之间的时钟偏差估计；b) Node 2 stores and processes after receiving the detection information of node 1 when the local clock reading is T2 ; at this time, ,in, Indicates the estimated transmission delay from node 1 to node 2, Indicates the clock skew estimate between node 1 and node 2;
c)节点2在本地时钟读数为T3的时刻发送响应信息给节点1，响应信息中包含节点2的本地时钟读数T3和探测信息的前向传输时延T2-T1；c) Node 2 sends a response message to node 1 when the local clock reading is T3 , and the response message includes the local clock reading T3 of node 2 and the forward transmission delay T2 -T1 of the detection information;
d)节点1在本地时钟读数为T4的时刻接收到节点2发送的响应信息，此时， ，表示从节点2传输到节点1的传输延时估计，表示节点1和节点2之间的时钟偏差估计。d) Node 1 receives the response information sent by node 2 at the moment when the local clock reading is T4 , at this time, , Indicates the estimated transmission delay from node 2 to node 1, Indicates the clock skew estimate between node 1 and node 2.
假设往返时延相等，即，由上述步骤可以得出：Assuming that the round-trip delay is equal, that is , it can be obtained from the above steps:
⑵ 和 ⑶ ⑵ and (3)
时钟同步算法为待同步的传感器节点提供两个参数：时钟偏差估计和传输时延估计。这两个参数用以实现将传感器节点的本地时钟校准为目的节点的标准时钟。校准函数为：⑷。The clock synchronization algorithm provides two parameters for the sensor nodes to be synchronized: the clock bias estimate and transmission delay estimation . These two parameters are used to calibrate the local clock of the sensor node to the standard clock of the destination node. The calibration function is: ⑷.
该技术的实现流程包括四个阶段，分别为：一、无线传感器网络协议栈配置阶段；二、无线传感器网络应用层配置阶段；三、无线传感器网络部署和实施阶段；四、无线传感器网络实施优化阶段。The implementation process of this technology includes four stages, namely: 1. Wireless sensor network protocol stack configuration stage; 2. Wireless sensor network application layer configuration stage; 3. Wireless sensor network deployment and implementation stage; 4. Wireless sensor network implementation optimization stage.
一、无线传感器网络协议栈配置阶段；1. The wireless sensor network protocol stack configuration stage;
无线传感器网络时钟同步技术的实现基于AODV路由协议，因此需要重新配置AODV路由协议栈，具体包括如下步骤：The realization of wireless sensor network clock synchronization technology is based on the AODV routing protocol, so the AODV routing protocol stack needs to be reconfigured, including the following steps:
1、在原始AODV路由协议的路由表项描述中增加源节点和目的节点之间的时钟偏差估计、传输延时估计和同步完成标志；其中，的类型为双精度浮点型，的类型为双精度浮点类型，的类型为布尔型。如图4所示为AODV路由协议的路由表项结构。1. Add the clock skew estimation between the source node and the destination node in the description of the routing table entry of the original AODV routing protocol , transmission delay estimation and sync complete flag ;in, is of type double precision floating point, The type of the double-precision floating-point type, is of type Boolean. Figure 4 shows the routing table entry structure of the AODV routing protocol.
2、在原始AODV路由协议的RREQ分组定义的基础上，增加源节点的本地时钟标记字段STS(Source Time Stamp)，STS的数据类型为双精度浮点类型。如图5所示的RREQ命令结构图。2. On the basis of the RREQ packet definition of the original AODV routing protocol, the local clock mark field STS (Source Time Stamp) of the source node is added, and the data type of the STS is a double-precision floating-point type. The RREQ command structure diagram shown in Figure 5.
3、在原始AODV路由协议的RREP分组定义的基础上，增加源节点到目的节点的前向传输延时字段FTD(Forward Transmission Delay)，FTD的数据类型为双精度浮点类型，目的节点的本地时钟标记字段DTS(Destination Time Stamp)，DTS的数据类型为双精度浮点类型。如图6所示的RREP命令结构。3. On the basis of the RREP packet definition of the original AODV routing protocol, the forward transmission delay field FTD (Forward Transmission Delay) from the source node to the destination node is added. The data type of FTD is double-precision floating point type, and the local Clock mark field DTS (Destination Time Stamp), the data type of DTS is double precision floating point type. The RREP command structure shown in Figure 6.
4、修改AODV路由协议的SendRequest方法，在函数对RREQ命令处理部分将本节点当前时钟读数写入RREQ命令中。4. Modify the SendRequest method of the AODV routing protocol. In the function processing part of the RREQ command, the current clock reading of the node is Write in the RREQ command.
5、修改AODV路由协议的RecvRequest方法，通过定义一个变量保存接受RREQ命令的时刻，根据时钟同步开销优化方法，即前文所述的步骤D，如图7所示，如果该中间节点包含到目的节点的路径信息和时钟同步信息，根据D1所述的（5）和（6）令和，而后使用 SendReply方法发送RREP命令至源节点。否则继续使用SendRequest方法在网络中搜寻目的节点，当目的节点接受到RREQ命令时，令和，而后使用SendReply方法发送RREP命令至源节点。5. Modify the RecvRequest method of the AODV routing protocol, and save the moment when the RREQ command is accepted by defining a variable , according to the clock synchronization overhead optimization method, that is, step D mentioned above, as shown in Figure 7, if the intermediate node contains the path information and clock synchronization information to the destination node, according to (5) and (6) described in D1 make and , and then use the SendReply method to send the RREP command to the source node. Otherwise, continue to use the SendRequest method to search for the destination node in the network. When the destination node receives the RREQ command, make and , and then use the SendReply method to send the RREP command to the source node.
6、在原始AODV路由协议的RecvReply方法中，增加时钟同步的计算过程，依据公式(2)和公式(3)计算源节点和目的节点的时钟偏差估计和传输延时估计，同时设置同步完成标志为TRUE。6. In the RecvReply method of the original AODV routing protocol, the calculation process of clock synchronization is added, and the clock offset estimation of the source node and the destination node is calculated according to formula (2) and formula (3) and transmission delay estimation , while setting the synchronization complete flag is TRUE.
7、修改AODV路由协议的SendData方法，在发送普通数据时，为普通数据包增加时间戳，依据公式(4)对时间戳进行处理，实现数据传输的时钟偏差消除。7. Modify the SendData method of the AODV routing protocol. When sending ordinary data, add a time stamp to the ordinary data packet, and process the time stamp according to formula (4), so as to eliminate the clock deviation of data transmission.
8、编译修改后的AODV协议栈，并将其写入传感器节点的主控芯片MSP430中。8. Compile the modified AODV protocol stack and write it into the main control chip MSP430 of the sensor node.
二、无线传感器网络应用层配置阶段；Second, the wireless sensor network application layer configuration stage;
按照应用需求，设置传感器节点采集数据的类型和周期，完成应用层的相关任务，并使用网络层修改后的AODV路由协议为代理进行数据的发送，实现监测任务。According to the application requirements, set the type and cycle of data collected by the sensor nodes, complete the relevant tasks of the application layer, and use the modified AODV routing protocol of the network layer as the agent to send data to realize the monitoring task.
1、依据传感器的检测对象特性，在软件的应用层为传感器节点配置数据的采样周期和汇报周期，一些开关量可以被设计为事件触发的汇报机制。1. According to the detection object characteristics of the sensor, configure the data sampling cycle and reporting cycle for the sensor node at the application layer of the software, and some switching values can be designed as an event-triggered reporting mechanism.
2、依据传感器的检测对象对同步精度的需求，设置主动时钟同步周期，对于时钟同步精度要求较高的节点可以设置较短的时钟同步周期，而对于时钟同步精度要求较低的节点可以设置较长的时钟同步周期。2. Set the active clock synchronization cycle according to the synchronization accuracy requirements of the detection object of the sensor. For nodes with higher clock synchronization accuracy requirements, a shorter clock synchronization cycle can be set, and for nodes with lower clock synchronization accuracy requirements, a shorter clock synchronization cycle can be set. Long clock synchronization period.
三、无线传感器网络部署和实施阶段；3. Deployment and implementation stage of wireless sensor network;
1、为不同的传感器节点设置唯一的物理地址，并将配置好的AODV协议栈以及应用层软件写入节点的FLASH存储器中，按照检测对象的位置部署传感器节点，实施检测任务。1. Set unique physical addresses for different sensor nodes, write the configured AODV protocol stack and application layer software into the FLASH memory of the nodes, deploy sensor nodes according to the location of the detection object, and implement detection tasks.
2、根据需求在网络中设置汇聚节点，此时汇聚节点具有标准时钟，各传感器节点通过AODV路由协议实现到汇聚节点的路径发现，同时完成与汇聚节点的时钟同步。2. Set the convergence node in the network according to the requirements. At this time, the convergence node has a standard clock. Each sensor node realizes the path discovery to the convergence node through the AODV routing protocol, and completes the clock synchronization with the convergence node at the same time.
四、无线传感器网络实施优化阶段；4. Implementation and optimization stage of wireless sensor network;
因为优化过程本身就包含在时钟同步算法的实现过程中，同时可以由图2和图7中看出。在图2中，S点作为源节点、D点作为目的节点，节点1到节点12均为中间节点，详细的优化过程在此不再详细介绍。Because the optimization process itself is included in the implementation process of the clock synchronization algorithm, it can be seen from Figure 2 and Figure 7 at the same time. In Fig. 2, point S is used as the source node, point D is used as the destination node, and nodes 1 to 12 are all intermediate nodes, and the detailed optimization process will not be described in detail here.
应用本项技术，可以解决监测任务中各节点所采集的数据在时间标记上具有较大偏差的问题。本系统中，汇聚节点作为具有标准时钟的节点，网络中其他各传感器节点均与汇聚节点实现时钟同步，因此各传感器节点采集的数据在时间标记上具有同步性，所采集的数据在时间标记上将会非常精确。The application of this technology can solve the problem that the data collected by each node in the monitoring task has a large deviation in the time stamp. In this system, the aggregation node is a node with a standard clock, and all other sensor nodes in the network are synchronized with the aggregation node. Therefore, the data collected by each sensor node is synchronized in the time stamp, and the collected data is synchronized in the time stamp. will be very precise.
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| CN201410711128.9ACN104540212B (en) | 2014-12-01 | 2014-12-01 | On-demand clock synchronization method for wireless sensor network based on AODV routing protocol |
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| US10531412B2 (en) | 2017-11-06 | 2020-01-07 | Sony Corporation | On demand route synchronization and beamforming in wireless networks |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101697502A (en)* | 2009-09-22 | 2010-04-21 | 哈尔滨工业大学 | Method for precisely synchronizing wireless sensor network under coal mine |
| US20110134906A1 (en)* | 2009-12-03 | 2011-06-09 | Qualcomm Incorporated | Method and apparatus for distributed processing for wireless sensors |
| CN104053223A (en)* | 2013-03-13 | 2014-09-17 | 中国科学院大学 | A Time Synchronization Method for Low-power Wireless Sensor Networks |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101697502A (en)* | 2009-09-22 | 2010-04-21 | 哈尔滨工业大学 | Method for precisely synchronizing wireless sensor network under coal mine |
| US20110134906A1 (en)* | 2009-12-03 | 2011-06-09 | Qualcomm Incorporated | Method and apparatus for distributed processing for wireless sensors |
| CN104053223A (en)* | 2013-03-13 | 2014-09-17 | 中国科学院大学 | A Time Synchronization Method for Low-power Wireless Sensor Networks |
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|---|---|---|---|---|
| US10531412B2 (en) | 2017-11-06 | 2020-01-07 | Sony Corporation | On demand route synchronization and beamforming in wireless networks |
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|---|---|
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| Publication | Publication Date | Title |
|---|---|---|
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