The Design of Supermarket Electronic Shopping Guide System Based on ZigBee Communication Yujie Zhang, Liang Han, and Yuanyuan Zhang College of Electrical and Information Engineering, Shaanxi University of Science and Technology, Xi an, China Abstract. Based on the ZigBee networking technology and protocol analysis, The paper designs a ZigBee Network Model with the features of communication and location which mainly rests on CC2431 ZigBee network location property and further propose a mobile electronic supermarket shopping guide system which can locate expected goods, navigation and offer the latest information on supermarket product. Keywords: Wireless Networking Technology, Positioning Engine, ZigBee, CC2430, CC2431. 1 Introduction With the development of economy and society, the emergence of large supermarkets provides people with a convenient place to buy necessities. To some extent, it facilitates the purchase and save time. However, the enormous size of the supermarket with the increase quantities and types of goods makes customer inconvenient to find out what they need and get the latest goods information. This paper presents a mobile electronic supermarket shopping guide system, which can be fitted in the shopping cart locating expected goods and offering the latest information on supermarket product. 2 ZigBee Technologies ZigBee is a standard network protocols based on IEEE 802.15.4 wireless [1], communicating in the 2.4G band with high efficiency and low rate. ZigBee Network supports Full-Function Device (FFD) and Reduced Function Device (RFD) two physical devices, which are made up of Coordinator, routers and terminal equipment [2]. A Coordinator and a router are full function devices (FFD), completing a large number of services set by ZigBee protocol and communicating with any node of the network. While Terminal equipment can be either a FFD or a streamlining of the agreement node (RFD) only communicating with the FFD. S. Lin and X. Huang (Eds.): CSEE 2011, Part I, CCIS 214, pp. 219 224, 2011. Springer-Verlag Berlin Heidelberg 2011
220 Y. Zhang, L. Han, and Y. Zhang 3 Systems and the Network Model 3.1 Location The achievement of this wireless location system mainly depends on CC2431 ZigBee network environment and the built-in wireless location engine [3]. There are three types of nodes Central node, blind nodes and reference nodes. Central node is constituted of the coordinator (FFD), initiating a network. Blind node made up of terminal device (RFD) is a key to locate, which can calculate the current coordinate. The coordinates of Reference node comprising the router are known in their respective networks, (FFD) which can help the blind node position. CC2431 location engine is on the basis of RSSI technology [4], RSSI refers to the strength of the wireless signal the node receives. The signal propagation loss can be calculated by the strength of known transmitter node and receive node. Then it can be changed into the distance using empirical models. Then the location of the node can be known by existing algorithms and the fixed coordinates. Blind node receives the packet signal from the reference node, which access to reference node coordinates parameters and the corresponding RSSI value, and then send them into the location engine. We only need to write the required parameters into the positioning engine. The result can be read out after waiting for completion of the engine. The theoretical RSSI value can be shown as equation (1) [5]. RSSI=-(10n lgd+a) (1) Among them, the RF parameters A and n are used to describe the network operating environment. RF parameter is defined as 1 m from the transmitter at the absolute value of the received signal strength. RF parameter n is defined as the path loss index, which indicates the rate of decay with the distance increases during the signal energy to the transceiver. d is the distance between the transmitter and the receiver. Fig. 1. Location diagram Positioning operation use the " best" reference nodes the highest RSSI value. For example, in the area as shown in Figure 1 (a), in the X, Y directions a reference node is placed every 30 m. Firstly, find a reference node with the highest RSSI values. Since each reference node of the horizontal and vertical coordinates has the maximum length of 63.75m, thus identify a 64 m 64 m range in the center of "best" reference nodes. As the RSSI value of this node is known, the distance d1 is available
The Design of Supermarket Electronic Shopping Guide System 221 between the blind nodes to this node. Locate the reference nodes except the "best" node and calculate these distances away from the blind node (d2 ~ d8) in the same way. After completion of this calculation, Blind node position is fixed in the global grid as is shown in figure 1(b). Finally, get the value of all fixed coordinates into the location engine and read out the results of the final position. 3.2 Network Model The net is made up of the structural design of components based on the mesh network [6] basic network topology, as is shown in figure 2. It has self-establishment and maintenance functions without human intervention. Each node can communicate with at least one node, supporting jump multi-level routing. Fig. 2. Network topology Net structure of the system is shown in Figure 3, the supermarket will be divided into several region, each region based on MESH-based network topology to establish sub-networks. Central node (also known as the gateway) initiates the regional subnetworks. At the same time it completes the communication between server and the wireless network. Each shopping Cart is fitted a mobile device with a blind node to complete the positioning. Blind nodes can be discovered independently adding and exiting networks, receive and send data, but not for router. What s more, reference nodes are established in specific locations, reference nodes in their network coordinates are known, so it can help the blind node position and routed the data. Central node for each partition of the data can be summarized by the way of wire transfer to the server. Mobile devices first add into the sub-network which carrying the blind nodes after power, reference node will notice the blind node using self coordinates by sending data packet. Blind node receives the data packet signal from the reference node, obtains the reference node coordinates and the corresponding RSSI value, sending it into positioning engine. Then the currently own position after the positioning engine calculation can be read out, that is the initial coordinates. After customers enter a query term, the initial coordinate was sent into the server with customer inquiries through the reference node and the central node. Server can obtain the aim coordinates after the sever search the query term that can calculate the best path using these two coordinate values and map of supermarket. Then server can replay this path to the mobile device in form of a set of coordinates. Customer mobile follows this path, because blind node can independently join and leave different sub network, so it can constantly refreshing the current coordinates to achieve the navigation function. In this network model, blind nodes can communicate with the server in any location, so customers can get the latest product information anytime, anywhere in the supermarket.
222 Y. Zhang, L. Han, and Y. Zhang Fig. 3. Network Model 4 System Configuration and Implementation 4.1 System Hardware Structure According to the above network, model system is divided into mobile device, the reference node module, the gateway node module and the server these parts. (1)Mobile device: It is composed of the touch screen (four-wire resistive screen), flash memory, power and blind node, and such Peripherals devices, which is the core produced by Samsung company ARM9 microprocessor SC2410.Touch-screen can realize the information into the query and query results display, and navigation interface display functions. FLASH memory can store of the map of the regional supermarket. Blind node designed by the CC2431 to achieve the positioning, it is shown in figure 4 (a). Fig. 4. Hardware structure (2) Reference node (gateway node): This part was made up with the CC2430, power supply, reset circuit and an antenna minimum system which is the basic unit in Network communication and positioning system. Structure is shown in Figure 4 (b). 4.2 System Node Software This system nodes are all using OSAL real-time operating system implementation, OSAL layer can provide information management, task synchronization, time
The Design of Supermarket Electronic Shopping Guide System 223 management, interrupt management, task management, memory management, power management and non-volatile storage management service. (1) Gateway node: It is positioning System Coordinator which connected with the server through the RS-232. Firstly, it offers the reference node and blind node configuration data and sends it to the corresponding node [8]. Secondly, the data feedback by each node was received and sent to the server. Work flow chart is shown in Figure 5. Fig. 5. Gateway Node software process (2) Reference node: Itself coordinates are known in positioning system which as the router. Its service is to provide an accurate data packet that contains position (X, Y) coordinates and the RSSI value of itself to blind node [8]. This node must be configured correctly in the area. Work flow chart is shown in Figure 6. (3) The blind node: It is a mobile node in positioning system, belong to the terminal device. Through receiving the coordinates of all reference nodes and RSSI value in positioning the region, it can calculate the self-coordinate using positioning algorithm [8].Work flow chart is shown in Figure7. Fig. 6. Reference node software process Fig. 7. Blind Node software process
224 Y. Zhang, L. Han, and Y. Zhang 5 Conclusions The paper designs a ZigBee Network Model with the features of communication and location which mainly rests on CC2431 ZigBee network location property and further proposes a mobile electronic supermarket shopping guide system which can locate expected goods and offer the latest information on supermarket product. Combining the positioning technology, communication technology and computer technology is a new and meaningful field for study accompanied by good economic and social benefits we just update the related goods information on the server and check them on mobile devices. The employment of the system can comfort customer and facilitate management of supermarket. References 1. Qu, L., Liu, S., Hu, X.: Technology and Application of ZigBee. Press of Beihang University 2. Li, W., Duan, C.: Professional training on Wireless Network and Wireless location of ZigBee. Press of Beihang University (2006) 3. Yao, Y., Fu, X.: Network Location of Wireless Sensor based on CC2431. Information and Electronic Engineering 4. Gao, S., Wu, C., Yang, C., Zhao, H., Chen, Q.: Teaching of ZigBee Technolog. Press of Beihang University 5. Chai, J., Yang, L.: Location System of Patients based on ZigBee. Measuring and Engineering of Compter 6. Ren, F., Huang, H., Lin, C.: Network of Wireless sensoring. Journal of Software 7. Sun, T., Yang, Y., Li, L.: Development Status of Wireless Sensor Network. Application of Electronic 8. Sun, M., Chen, L.: Application of ZigBee in field of Wireless Sensor Network. Modern Electronics Technique