1、1Design and implementation of wireless sensor network data transfer protocolAbstract： This paper discussed the problem of wireless sensor network data transmission protocols， and combined with the characteristics of WSN and the actual needs， the design and implementation of a data transmission prior
2、ity queue and priority transmission scheme of ACK， provide an end-to-end transmission for the important information， and achieve the timely， reliable transmission of control information. Keywords： WSN ； Reliable transmission； Priority queue；Data transfer protocol 1 Introductions wireless sensor netw
3、orks （WSN） as a new information acquisition and processing mode， to build a bridge of information space and physical space， which are widely used in national defense， national security， environmental monitoring， traffic management， health care， manufacturing， anti-terrorism disaster other fields. WS
4、N is essentially a special kind of self-organization network， with the following characteristics： 1） network 2size， high node density； 2） node energy， computing and storage capacity strictly limited； 3） the nodes prone to failure ， network topology changes frequently； 4） node has no unified identity
5、； 5） the general location of the node deployment does not change on the one hand， relying on battery-powered sensor nodes and usually work in unattended environments， very difficult to replenish their energy Therefore， energy optimization throughout all levels to communicate， work patterns， task coo
6、rdination， data management， etc.； the other hand， wireless sensor networks are designed for specific applications， different applications have different expectations of quality of service requirements， network design should first consider the quality of service applications. Meanwhile， the sensing d
7、ata collected by the sensor node have a strong correlation， this correlation may exist such that the data redundancy in the time and space， reduce this redundant design of wireless sensor networks become considered a priority. Articles designed and implemented a practical and reliable data transfer
8、protocol， to achieve the priority transmission intelligent building energy wireless sensor network information to ensure the stability of energy-saving systems， reliable and 3efficient operation. 2 Routing protocol for Wireless Sensor Networks 2.1 LEACH low-energy adaptive clustering hierarchy （LEAC
9、H） is a kind of adaptive clustering routing algorithm， the algorithm put forward a model 4 low power continuous operation. The LEACH protocol can be divided into 2 stages， namely initial stage and completed stage. In order to minimize energy consumption， ready phase lasts longer than the initializat
10、ion phase length. The sum of the initialization phase and ready phase duration is called a wheel in the initialization phase， the LEACH protocol randomly select a sensor node as a cluster head nodes， random to ensure that the cost of high energy consumption data transmission between cluster head and
11、 base station evenly spread to all sensor nodes. Method for selecting specific for， a value between a sensor node randomly selects 01， if the selected value is less than a threshold T （n） ， then the nodes become cluster head nodes. T （n） value according to formula （1） calculation： Wherein， N： the to
12、tal number of sensor nodes in the network； k： in the first round of the network nodes in the class； r： number of rounds has been completed； G： In the remaining N/kr wheel does not 4become a sensor head node class consisting of a collection of nodes. After the class header node is selected， once clus
13、ter head node is selected， will take the initiative to broadcast to all nodes in the network， according to the strength of the received broadcast signal nodes choose their classes to join and send a message to inform the appropriate poly class header. After class formation， cluster head distribution
14、 channel using time division multiplexing approach to the right to use the class node. In the ready stage， cluster head start accepting data collected within the class of each node， then using data fusion and data compression technologies converge， will integrate the data transmission to the base st
15、ation or sink node. Ready phase lasts for some time， the duty cycle of the network into the next round， re-select the cluster head. 2.2 SPIN Sensor Protocol for Information via Negotiation （SPIN） is a data-centric communication adaptive routing protocol. SPIN protocol goals is through negotiation sy
16、stem and resource use adaptive mechanisms between nodes ， the explosion of information exists to solve the classic problem of overlap and diffusion method ， the sensor nodes transmit data to consult 5each other before sending the description of sensor data attributes， instead of transmitting all the
17、 data （ such as images ） to conserve energy. SPIN has three packet types ， namely ADV， RED and DATA. ADV new data for broadcasting ， when a node has data to share when it is available ADV packet （including metadata ） outside broadcasting ； REQ to request data ， when a node wishes to receive the DATA
18、 packet ， the packet transmission REQ ； DATA contains attach metadata header （Meta-Data Header） packet capture sensor data . DATA before sending a packet ， a sensor node first outside broadcast ADV packet ； If a neighbor node after receiving ADV willingness to receive the DATA packet ， the node send
19、s a REQ to the packet ， then the node again neighbor node sends dATA packets. Similarly proceed ， DATA packets can be transmitted to a remote sink node or base station. 2. 3 Directed Diffusion Directed Diffusion is a data-centric routing protocol， sink node sends its flags to all sensor nodes， i.e.，
20、 by assigning different values ?to indicate different task attribute descriptors， each sensor node after receiving the flag stored in the respective buffer. Each entry contains a 6time stamp flag field and several gradient domain， ie the ability to minimize costs and adaptive principles to guide the
21、 direction of data proliferation. When a flag is spread throughout the network， from the source node （ie， Hobbies sensor nodes in your area） to the gradient between the sink node is set up， shown in Figure 1. 3 Design and implementation of a reliable transport Send data： if the data needs to be sent
22、， first put it into the send queue queuing polling， then its assembly header， and then send them via MAC layer processing. Removed from the queue after sending data to its next hop node receives ACK returned， thus completing the first transmission of the packet. Receive data： When a node receives a
23、pass up the underlying data， according to the type of packet processing functions into different， if a node receives a packet is a common Data package， the data in the receive queue， and then handed over to the appropriate with layers for processing， depending on the choice of local processing or fo
24、rwarding destination. Retransmission of the data： In the conventional IEEE 802.15.4 protocol， the transmission data packet to the next 7hop of the next hop needs to reply ACK， ACK is not received when the timeout data retransmission is performed， the maximum number is 3.if 3 retransmissions fail， di
25、scarded packets. Thus， the conventional transmission protocol packet is not classified， considering only a single transmission queue. In addition， the node hop provides up to three times the retransmission can not be guaranteed accurate transmission of critical information packet. Therefore， the nee
26、d to improve the agreement， the priority of the packet classification， use the priority queue management thinking， while providing end-to-critical information package guarantees to meet the application requirements of wireless sensor networks building energy systems for data transmission. 3.1 Priori
27、ty queue transmission According to the three kinds of data type， the data is divided into three priority， High Priority （HP） ， MiddlePriority （MP） ， Low Priority （LP）. Each node has high， low， three priority FIFO queue， denoted as HP， MP， LP， and with same length buffer， each queue according to the
28、distribution of different importance to different weights. When a packet arrives， first should be filtered through a packet classifier， are prioritized according to the different types， 8and then was added to different queue tail. Priority from the column as shown in figure 2. For any priority queue
29、， when the queue length L exceeds a threshold of THR， not immediately start the congestion indication bit C， but with probability P position， then the network is congested or slight congestion； when the threshold L exceeds the set of thr， show that the network has serious congestion， as soon as poss
30、ible in order to ease congestion， packets are discarded strategy must be. Queue scheduling to access the channel， from high to low priority order of priority scheduling， ensure the high priority data. At the same time in order to protect high priority information transmission channel， the informatio
31、n given high priority access channel， priority， the information transmission with fewer backoff delay. 3.2 Priority ACK mechanism In the IEEE 802.15.4 standard， each of the MAC data frame will require the recipient replies to ACK frame， ACK frame transmission of will in the network cause energy wast
32、e. Therefore， the need for IEEE 802.15.4MAC protocol ACK mechanism to improve. When the network is stable， the common data periodic is composed of a wireless sensor network to the outside world 9report， this information is often a certain redundancy. For example， the wireless sensor network in an ho
33、ur or even a longer period of time temperature data collection， indoor light intensity data， a small amount of packet loss not have a great impact on the whole system. At the same time， in the absence of such interference， wireless link state good， general data transmission success rate is very high
34、， does not need each dive has a ACK confirmation reply. Therefore， to confirm the data packet using the following strategy： （1） low priority packets： no ACK verification； （2）： priority packets hop by hop ACK confirmation； （3） a high priority packet： hop by hop ACK confirmation and end-to-end ACK con
35、firmation. For the high priority packets， if confirmed information from the destination is not received in a certain period of time， then start retransmission mechanism. 4 The actual test design and test environment Node uses ATmega128 as a processor， RF chip adopts CC2420 chip， power supply module
36、using 9 V DC voltage power supply or battery powered directly by 3.3V. Verification system as shown in figure 3. The circular nodes （such as 7011） is a common node， triangle nodes （such as 1951） as relay nodes， a node 10（8919） for the gateway node. The common node in the collection of each room temp
37、erature and humidity， light intensity sensing information， through a relay node in a multi hop way to send data to the gateway node， protocol conversion gateway node transmits data to the server and stored in a local database. On the server side， the user can send the user management end of the grap
38、hical interface command， sent through the network joint point for ordinary nodes， can change the ordinary node configuration， access node information and other functions. Send the test data packets as shown in Figure 4， the top 4 is the adapter， converted to binary for the top 16， including No.12 an
39、d No.13 indicate priority packet. HP=“11“， MP = “01“， LP= “00“， corresponding to the chart is “18“， “08“， “00“. Figure 5 is results of the packet loss rate test， the use of end acknowledgment mechanism can ensure reliable transmission of high priority data； while allowing the packet loss priority and low priority data is lower than the conventional data transmission protocol； when hops 6， due to the complexity of the actual application environment， network performance is not stable， increase the packet loss rate of data transmission significantly. Therefore， the proposed
