1、1Design of wireless sensor network database based on message transferAbstract: In this paper, according to the needs of the application, discussed the necessity of constructing the database of wireless sensor network, and analyzes the difference in function of the traditional database management sys
2、tem, and the problems faced in the implementation; the architecture of the system is analyzed in detail, including the database and network node on the function composition, and between nodes cooperate to complete the key technology of query. Keywords: WSN; database design; Message triggers; 0 Intro
3、ductions Most application mostly uses the collected sensor data, centralized treatment by using the wireless network transmission. This method has many disadvantages: firstly, wireless sensor network is not taking the application demand access to data, at the same time, no or little use of processin
4、g capacity of nodes to process data, it result a large number of redundant data in network transmission, wireless 2communication has large burden; secondly, it can not adapt to the dynamic topology and the life cycle requirements, but can not support different applications. With the increase of sens
5、or network scale, the problem will become more prominent. In view of this situation, researchers put forward the concept of wireless sensor network database, wireless sensor networks are built to support multiple applications to improve the performance of the data center, data management, and ease o
6、f use, various applications directly use SQL language simple to query data. 1 Structure of the sensor network database Sensor network database is to store data (including the list of sensors and their associated attributes, such as location) composite applications and sensor data. Some of the curren
7、t structure of the sensor network data management system has the following four categories: centralized structure, semi-distributed architecture, distributed architecture, the hierarchical structure. (1) Centralized architecture Data acquisition method of wireless sensor network is to collect data f
8、rom each sensor and sent periodically to the base station, carried by the base Off-line analysis processing, the 3sensor node itself and the collection of data without any treatment, simply send or forward-aware data. This centralized architecture, the access network and the sensor sensing the query
9、 data is relatively independent. (2) Semi-distributed architecture The current sensors generally have certain computing and storage capacity, and therefore, certain calculations may be performed on the raw data, which promotes the development of semi-distributed model. In the semi-distributed model,
10、 the sensor data are aggregated into some kind of record (rather than raw data), which is then transmitted to a central server for further query processing. Currently, most studies have focused on the semi-distributed model. Representative system Fjord, cornell university Cougar, etc. (3) Distribute
11、d architecture Since the distribution of nodes, you can use the data storage system and the distributed database query techniques. This model in computing and communications are all carried out on the sensor. This configuration of distributed model is that it assumes that all the sensors have the sa
12、me conventional computer communications and computing power, it is only suitable for a large communication overhead event keyword-based 4query system. This is at least the current very realistic. (4) Hierarchical structure The structure contains two levels of sensor network layer and the network lay
13、er. And the integration of network data processing, adaptive query processing and query based on content etc. In sensor networks, each sensor node has a certain computing and storage capacity. Each sensor node to complete the 3 tasks, accept commands from the agency, local computation, the data will
14、 be sent to agents, each agent to complete 5 tasks: to accept a query from a user, the sensor node sends control commands and other information, receiving data from the sensor nodes, processes the query, the query results are returned to the user. The agent node received from the sensor node data, a
15、 plurality of agent nodes distribution to process the query and returns the results to the user, the computation and communication tasks are distributed to each proxy node. 2 The technology of wireless sensor database Wireless sensor network database data distribute “store“ on each node to establish
16、 a connection between the storage nodes via ad-hoc networks, forming a distributed database. Static data on all nodes and dynamic data be into the data retrieval 5applications. Currently, foreign research mainly has TinyDB and COUGAR system in this regard. Both systems have in common, but TinyDB bet
17、ter account of the energy savings, and the query selection, aggregation, grouping and other operations have better support. We will combine TinyDB system to discuss the design and implementation of wireless sensor network databases. Wireless sensor network database is divided into two parts: one to
18、run the database on the front of the base station, which serves as the application to access the data interface; Second embedded query execution engine running on each node, and the node activity is responsible for the implementation of the query administration. 2.1 The front end design of wireless
19、sensor network database Wireless sensor network front-end database run in wireless sensor network base station, the base station can be PC; it can also be a special XScale based Micro server and other equipment. Wireless sensor network database provides a query interface and command SQL like interfa
20、ce to the application, only need to use the SQL language to get interested in the data from the sensor network. The query language has the following format: Data in wireless sensor networks need to get from the database on 6each node, each node maintains its own separate various attribute data. Data
21、 on the nodes can be divided into three categories: one is a constant properties, including the node ID, packet location; introspection second property, such as voltage, time stamp, the parent node in the network topology, etc.; third species is the sensor sensing data. Data Access Components node i
22、s responsible for providing a unified interface to access these properties, the internal organization of the component attribute node for the data on the table, each record in the table to save the property name, type, and property values. If it is a constant value, then the property value recorded
23、directly; If the amount is property, the record can obtain the corresponding components of the data. Fig.3 is equivalent to a small node data access components within the data repository nodes can effectively according to the appropriate data field names to find and locate. 2.3 Interact with clients
24、 and wireless sensor networks Wireless sensor network operating system exchange with the data under network layer, because the physical connection and wireless sensor network is accomplished through DART interface of computer serial port and nodes, so below a layer of data exchange message needs to
25、be converted into a message (Packet) 7to send and receive, and also need proper protocol to ensure that a message receiving and transmitting stable and reliable. Specific implementation details as follows: Class “MoteIF” package and convert sending and receiving data, it has two members object “send
26、er” and “receive” to complete transform of message and the packets, but also encapsulates a specific data source “PhoenixSource”, “PhoenixSource” inherited from the data source “PacketSource” (of this class to achieve reliable communication with the computer serial port or TCP/IP SOCKET between pack
27、ets), and has automatically add and delete messages in which the characteristics. The database is an event-driven database system, so in the course of these two data communication without exception, also used the event listener mechanism, from the top layer of view, “TaraxDBNetwork” object to “MoteI
28、F “registered listeners become “QueryResuItMsg” or “UartMsg” the listener when a message is received, the event “MessageListener” trigger, “messageReceived” method to achieve it is called; from the layer below it, when the object receives the packet receive event “PacketListenerlF” trigger, “packetR
29、eceived” methods it implements is invoked. The two layers of data transmission and reception process shown in Figure 3. Since the sensor 8between the client and the network database system, and all the nodes on the network communicate by message passing, and then define the various types of messages
30、 on the database system, representing different meaning. For the same type of message at the node and were used nesC structure and Java class represents the client, in order to maintain this consistency, use the Message Interface Generator (MIG) software tools to achieve the transformation of the st
31、ructure and the Java class represents nesC between them. And attached a flexible read and set the message for each member variable method, which can reduce re-parse the message format customized programming burden. Figure 4 four message classes, a parent of three sub-classes respectively correspond
32、nesC end node data structure, the parent TOS MSG Message used to send a message, send a query for the three sub-classes respectively, receive the results of and commands sent. 3 Conclusions In the above discussion, we analyze the realization technology of system structure and data of a wireless sens
33、or network database query. Wireless sensor network database is becoming a hotspot in the research of database. With database support, we can better promote the application of wireless 9sensor network. This architecture in this paper, has good scalability, data processing algorithm can be better. Ref
34、erence 1 J Hill, D Culler.Mica:. A Wireless Platform for Deeply Embedded Networks J IEEE Micro, 2002,22 (6) :12-24. 2 V Raghunathan, C Schurgers, S Park, et al. Energy-Aware Wireless Microsensor Networks J. IEEE Signal Processing Magazine, 2002,19 (2) :40-50. 3 Samuel Madden, Michael J Franklin, Joseph M Hellerstein, et al.TAG: A Tiny Aggregation Service for Ad-Hoc Sensor Networks A Proc of the 5th Annual Symp on Operating Systems Design and Implementation (OSDI) C. .2002. 4 University of California at Berkeley. TinyOS EB/OL. Http:/webs.cs.berkeley.edu/tos, 2004-05.
