Wireless Sensor Network For Multi-Storey Building:Design and Implementation Minh-Thanh Vo, Van-Su Tran, Tuan-Duc Nguyen, Huu-Tue Huynh International University of Vietnam National University, Vietnam Email: vmthanh@hcmiu.edu.vn Abstract—In recent years, Wireless Sensor Network(WSN) is considered as a potential solution for home automation because of its reliability, low-cost, low-power consuming characteristics Several researches have been carried out using WSN for home automation, however most studies have been experimented in small houses or in one storey of a building There has been little discussion about design and implementation of WSN automation system in multi-storey buildings This paper describes a practical design and implementation of WSN for controlling and monitoring system in multi-storey building A building automation system using Micochip ZigBee WSN was developed and set up in the International University (IU) building for system evaluation The performance results confirm that Micochip ZigBee WSN based home automation system is practically applicable in multi-storey building environment Index Terms—WSN; multi-storey building; implementation I I NTRODUCTION In recent years, home automation system is becoming more and more popular People want to live in intelligent living spaces equipped whith home automation systems, these systems not only provide them convenience, comport, security but also reduce their daily living cost by energy saving solutions The demand for home automation products has been increased rapidly, which promise a potential market trend in near future The traditional home automation systems use wired connection solutions However the implementation of these systems requires cable installation at the same time with house building This problem causes inconvenient for users, especially when their houses have been built, few of them accept wiredsolutions because the installation of new cable system can destruct the original interior decoration Recent development of wireless technologies has innovated home automation field [1] It allows the installation of home automation system is independent with house building So far, several wireless technologies are emerging for the home automation applications The widely-used indoor wireless technologies include Bluetooth, Wi-Fi and WSN Wi-Fi and Bluetooth are short range in home wireless technologies with high data rate transmission However, high speed data rate transmission means that much power will be consumed Home automation system requires low cost, low power consume, and not require high speed data rate For this reason the low speed wireless technologies are more suitable than the rapid ones [2] A home automation network has characterized by relatively few nodes (20 ∼ 200) within a 80 - 600m2 area in which each node communicates relatively infrequently-every 978-1-4673-2088-7/13/$31.00 ©2013 IEEE ∼ 15 minutes A typical communication consists of 46 bytes of payload [3] ZigBee introduces a wireless technology of low-cost, lowpower, reliability, multi-hop networking which provides high reliability, larger coverage and easy integration into new and existing home control products [4] Due to these characteristics, ZigBee technology is considered as a potential solution for home automation There has been many researches in the field of home automation using ZigBee wireless technologies [5][6][7][8] However most of these researches limit the experiments in home environment, the practical implementation of WSN based home automation in multi-storey building should be verified Beside, the set network interoperability and functionality of these home automation systems should be further enhanced to better meet user requirements This paper describes a practical design and implementation of automation system in multi-storey building using ZigBee wireless sensor network with features: low cost, energy efficient, easy to install, highly scalable A prototype automation system for monitoring and controlling in multi-storey building with more than thirty sensor nodes and controlling nodes has been developed and tested successfully in the IU-Building The remainder of this paper is structured as follows: in Section 2, a building automation system design is described briefly Section describes the hardware design, Section describes briefly the software design The practical implementation and evaluation of the system is described in Section Finally, a conclusion is drawn in Section II S YSTEM D ESIGN In our work, we use ZigBee technology for implementing our architechture The ZigBee based controlling and monitoring system in multi-storey smart building consists of three main parts: building control and monitoring network, gateway node, and the internal remote control, as shown in Fig A Building controlling and monitoring network The building controlling and monitoring network is designed using ZigBee wireless sensor network technology The system consists of sensor nodes, actuators nodes, router nodes, and one coordinator node Coordinator is responsible for forming and maintaining the network Routers have the functions of routing and receiving messages, the remain nodes carry out sensing and controlling functions These nodes are 175 Fig System Architecture Design distributed in different rooms and floors of IU-building in multi-hop cluster-tree topology All communication between devices propagates through the coordinator and routers to the destination devices B Gateway Node The gateway node is designed to improve the inoperability of the building automation system and existing external networks Remote users can access the system through the Internet and mobile networks This feature enables users to carry out the control and monitoring tasks when they are away from the building The gateway node supports three network interface functions, one for connecting to ZigBee wireless sensor network, one for connecting to Internet network through building Local Area Network or ASDL line, the remain for communication with mobile network by GPRS modem The gateway is integrated with a security access program to check and process the communications through this node Database containing the status of all connected devices is integrated in gateway node By this way, all device status of each device in the system is continuously stored and updated Remote users can control and check status of all devices in the building perform functions of building automation applications In this project, temperature sensor, humidity senor, motion sensor, smoke sensor and door status sensor are used for monitoring functions Wireless power outlet, light switch control are implemented actuating functions Fig Platform node structure The structure of the platform node is shown in Fig The general node is composed of a power supply module, a microcontroller, a ZigBee transceiver, an interface for in-system serial programming and some other extended interfaces C Internal Remote Control To perform the remote control functions inside the building, a special node is designed with mobility support protocol, which enable this node can rejoin into the network when it moves to a new location This feature enables users to use the remote control node to control different devices in any place of the building III H ARDWARE DESIGN A Platform node design The designs of all the nodes in the system are based on the same platform node structure The purpose of these designs is to improve functioning interchangeability of all nodes in the system Different sensor and actuator modules can be added to 176 Fig Platform node hardware In this platform node, 2.4 GHz IEEE 802.15.4 Transceiver Module MRF24J40MA of Microchip are used to designed the platform node due to their low cost, low power consumption and small size characteristics PIC8F4620, a nanoWatt 8bit microcontroller with the advantages of high computational performance at an economical price, high-endurance, Enhanced Flash program memory is selected to used in this design Different sensors and actuators are then integrated with external circuits to form specific sensor or actuator node Fig.3 shows the result of platform node design B Gateway node design The home gateway consists of a coordinator node, GPRS access module, Internet access module, and power supply module as As shown in Fig The power supply module is used to supply regulated voltage for the all components in gateway node with different voltage levels To simplify the communication protocols in gateway node, each module has one microcontroller unit (MCU) to process the communication and controlling tasks, ZigBee node is designed with high speed MCU and large memory UART serial interfaces are used to connect coordinator node with Internet access module and GPRS access module Fig Fig Gateway node hardware 1) Environment and security sensor nodes: The sensor nodes have the function to monitor the building security and environment conditions Several sensor nodes have been developed including temperature, humidity, motion sensor, smoke sensor and door status sensor All sensor nodes are designed using rechargeable battery power supply To increase recycle time life of battery, energy saving mode is applied to control the operation of each node 2) Wireless Light Switch node: A light switch was integrated with a ZigBee platform node In this prototype the user can control and monitor the state of the light switch (On or Off) manually or remotely The light switch node is designed with small size so that these nodes can be put into the wallmounting-box of home electric switch Gateway node structure GPRS access module consist of an MCU and an GPRS interface module SIM300C of SIMCOM company, it is used to communicate with GSM network AT command can be used to send and receive SMS messages The received text messages are interpreted by the microcontroller and then sent to ZigBee wireless sensor network to relevant devices The status of devices in the building can also be known by the user if the user sends status request message The Internet access module composes of an MCU and ENC28J60 chip which functions as an internet interface circuit During the operating stage, user can access the ZigBee controlling and monitoring network through Internet access module Fig shows the result of gateway node design C Sensor and actuator node design To create sensor and actuator nodes, different sensor interface and control circuits are designed When one of these circuits is connected with a platform node, a specific sensor or actuator node is formed as shown in Fig 177 Fig Hardware of sensor and actuator nodes 3) Wireless power outlet node: A prototype automatic power outlet node is developed and integrated with ZigBee node platform This node is used to monitor and control all the devices which are supplied power by this wireless power outlet This node is also designed with small size, so that it can replace the wall-mounting power outlet which is very common used in the market IV S OFTWARE DESIGN The software design of ZigBee wireless sensor network is developed basing on Microchip Zigbee protocol stack This protocol stack supports each type of node procedure respectively, but mainly below the network layer communication protocol To complete the function of each node type, it is necessary to modify the procedures of application and network layer The software design of the whole automation system includes five element software: the coordinator software, router software, end device software, internet gateway software, GPRS gateway software The design of each element focuses on two layers, software layer is responsible for translating stack protocol to achieve the data processing and transmission Application layer runs user programs and application interfaces Fig shows an example project structure in the ZigBee protocol stack Fig Implementation of automation building system preprogrammed with the PANID (Personal Area Network Identifier), although it is possible for the coordinator to dynamically scan for existing network PAN IDs in the same frequency and generate a PAN ID that does not conflict All devices connected to the ZigBee home automation network are assigned a fixed 64 bit MAC address At the stage of the network initialization, the coordinator assigns itself the short address 0x0000 When each device joins in the system, it will be assigned a dynamic 16 bit short address that is fixed for the lifetime of the network After the initialization stage, data can be routed from any node to upper user terminals through wireless connections, and vice versa The gateway node also is intitilized and configured to have static IP address supports for connecting to Internet network through building Local Area Network or ASDL line GPRS module is a plug and play device, when the power is turn on, it will automatically connect to mobile network and ready for sending message VI P ERFORMANCE EVALUATION Several measurements are carried out to evaluate the performance of the Zigbee wireless sensor network on building automation system to confirm the reliability and feasibility of the system A Power Consumption Fig The structure in the ZigBee protocol stack V S YSTEM IMPLEMENTATION A prototype system has been implemented in our International University building As shown in Fig The system includes one coordinator node placed in 6th floor, six router node and more than 25 end device nodes placed in different locations of 5th, 6th, 7th floors of the building The communication range of one hop can exceed 30 meters in cluttered indoor environments To run and test the system, the first step is to configure ZigBee wireless sensor network The coordinator node is Low energy consumption is an important criterion in the WSN implementaion to make sure it is able to operate in long time with minimum maintenance The power consumption measurement is only carried for the end device as the coordinator and routers are practically mains powered at the coordinator node During the measurement, the end device is programmed to be in a timer sleep mode condition The node is configured to wake up at every 120 seconds interval for second just to send the data to the coordinator node For the rest of the time, the end device is in a sleep condition Based on the measurement results, The end device node’s power consumption is 27.3mA with RF transceiver active, and 178 0.1mA in deep sleep mode, the lifetime of the battery can be calculated as follow Power consumption during active mode : = 27.3 mA x 1s /(60 x 60) = 0.0076 mAH Power consumption during sleep mode : = 0.1 mA x 120 Seconds/(60x60) = 0.0033 mAH Total power comsumption = 0.0076 + 0.0033 0.0109 mAH Battery capacity = 170 mAH Expexted battery lifetime: = 170/0.0109 = 15596 hours 649 days = 1.7 years From the caculation result, the end device nodes can be able to operate for a continuous 1.7 years without the need of installing a new battery using a rechargeable battery with capacity of 170 mAH It means that it can be used longer life time is expected if a larger capacity battery is used We can improve the power consumption performance by selecting the right power output based on the area to be covered and customizing the firmware carrying out the tasks in the Zigbee module B Coverage Performance Coverage is another important criterion of wireless sensor network as it shows how large area of monitoring can be covered and to guarantee the delivery of data from the sensor nodes to the coordinator node at reliable signal strength Measurement is carried out in a indoor environment assumed close to actual application The coverage performance measurement is based on the average value of LQI produced by the sink node when receiving data The link quality indicator (LQI) is an indication of the quality of the data packets received by the receiver The NWK layer can use the LQI levels of the devices in the network to decide which path to use to route a message In general, the path that has the highest overall LQI has a better chance of delivering a message to the destination The LQI value is an unsigned 8-bit integer ranging from to 255 with the maximum value representing the best possible link quality The LQI value in ZigBee transceiver is calculated based on the Received Signal Strength Indicator (RSSI) value which is based on the receiver Energy Detection (ED) measurement for each incoming packet The LQI can be calculated as following equation[9] LQI = 255 * (RSSI + 81) / 91 LQI is chosen an indicator of coverage performance compared to RSSI because it does take into account the effect of noise during the data transmission and not solely on the signal strength produced by the module Fig.9 shows the coverage performance based on the LQI value between to 50m distance from the base station In order to further evaluate the maximum distance that can be reached, one best direction is chosen and the distance of end device from the base station is extended When the distance can not be further extended due to the coverage constraint that means the distance is greater than 50m, the routers between the end device nodes and the coordinator are expected to be used Fig Coverage area interm of LQI C Delay Performance Average End-to-End delay indicates the length of time taken for a packet to travel from the source to the destination It represents the average data delay an application experiences during transmission of data The end-to-end delay is the time taken for a data packet to reach the destination node The delay for a packet is the time taken for it to reach the destination And the average delay is calculated by taking the average of delays for every data packet transmitted The parameter comes into play only when the data transmission has been successful In our measurement, we evaluate the quality of network by Time delay correspond with the distances Fig 10 shows an example of delay performance of the automation buiding system, delay testing packets were sent from coordinator node to a destination node and then these packets were sent back to the coordinator node the lengths of time taken for these packets sent and received were measured and averaged The measurements were carried out with different distances form 2m to 50m The measurement results show that delay is acceptable at the distance not greater than 40m Fig 10 Delay performance of automation building system D Functional Testing Different building monitoring and control tasks have been tested which include indoor temperature and humidity data acquisition, building security monitoring, human-tracking, light 179 control, internal-building remote control of home appliances, external-remote control of home appliances through Internet and mobile network Some tests have also been performed to investigate the performance of the automation system in Wifi existing environment, the results show that the system work well in the environment with or without Wifi VII C ONCLUSION In this paper, a wireless sensor network based multi-storey building automation system has been designed, implemented and tested The system can be used for several applications such as indoor environmental data acquisition, building security monitoring, and human-tracking light control Moreover, the system can remotely control of home appliances through Internet and mobile network The system is expected to be developed for many other applications such as intelligent community administration system, remote industrial control system, and remote patient monitoring system The performance results confirm that WSN based home automation system is practically applicable in multi-storey building environment, the system can also work well in Wifiexisting environment R EFERENCES [1] D Culler, D Estrin, and M Srivastava, “Overview of sensor networks,” IEEE Computer Magaziner, pp 41–49, 2004 [2] J Lee, Y 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zigbee smart energy implementation for energy efficient buildings,” in Vehicular Technology Conference (VTC Spring), 2011 IEEE 73rd IEEE, 2011, pp 1–5 [9] I W Group et al., “Standard for part 15.4: Wireless medium access control (mac) and physical layer (phy) specifications for low rate wireless personal area networks (lr-wpans),” ANSI/IEEE, vol 802, no 4, 2003 180 ... this design Different sensors and actuators are then integrated with external circuits to form specific sensor or actuator node Fig.3 shows the result of platform node design B Gateway node design. .. create sensor and actuator nodes, different sensor interface and control circuits are designed When one of these circuits is connected with a platform node, a specific sensor or actuator node is formed... functions, one for connecting to ZigBee wireless sensor network, one for connecting to Internet network through building Local Area Network or ASDL line, the remain for communication with mobile network