DSpace at VNU: Wireless sensor network for multi-storey building: Design and implementation

The performance results confirm that Micochip ZigBee WSN based home automation system is practically applicable in multi-storey building environment.. This paper describes a practical de

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

monitor-ing system in multi-storey buildmonitor-ing A buildmonitor-ing 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 INTRODUCTION

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

sys-tems 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

connec-tion soluconnec-tions However the implementaconnec-tion of these systems

requires cable installation at the same time with house

build-ing This problem causes inconvenient for users, especially

when their houses have been built, few of them accept

wired-solutions 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

wire-less 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

do 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

5 ∼ 15 minutes A typical communication consists of 46 bytes

of payload [3]

ZigBee introduces a wireless technology of cost, low-power, reliability, multi-hop networking which provides high reliability, larger coverage and easy integration into new and existing home control products [4] Due to these characteris-tics, 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 ver-ified 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 effi-cient, 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 3 describes the hardware design, Section 4 describes briefly the software design The practical implemen-tation and evaluation of the system is described in Section 5 Finally, a conclusion is drawn in Section 6

II SYSTEMDESIGN

In our work, we use ZigBee technology for implementing our architechture The ZigBee based controlling and moni-toring 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 1

A Building controlling and monitoring network The building controlling and monitoring network is de-signed 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

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

inoperabil-ity 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

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 HARDWARE 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

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 2 Platform node structure

The structure of the platform node is shown in Fig 2 The general node is composed of a power supply module, a mi-crocontroller, a ZigBee transceiver, an interface for in-system serial programming and some other extended interfaces

Fig 3 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

8-bit microcontroller with the advantages of high

computa-tional 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 4

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

coor-dinator node with Internet access module and GPRS access

module

Fig 4 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 5

shows the result of gateway node design

C Sensor and actuator node design

To create sensor and actuator nodes, different sensor

in-terface 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 6

Fig 5 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 inte-grated 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 wall-mounting-box of home electric switch

Fig 6 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 SOFTWARE 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

respec-tively, 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

in-cludes 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

transmis-sion Application layer runs user programs and application

interfaces Fig 7 shows an example project structure in the

ZigBee protocol stack

Fig 7 The structure in the ZigBee protocol stack

V SYSTEM IMPLEMENTATION

A prototype system has been implemented in our

Interna-tional University building As shown in Fig 8 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

commu-nication 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

Fig 8 Implementation of automation building system

preprogrammed with the PANID (Personal Area Network Identifier), although it is possible for the coordinator to dy-namically 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 PERFORMANCE EVALUATION

Several measurements are carried out to evaluate the per-formance of the Zigbee wireless sensor network on building automation system to confirm the reliability and feasibility of the system

A Power Consumption 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 consump-tion 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 1 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

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

Mea-surement 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 0 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

com-pared 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 2 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 9 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 ac-quisition, building security monitoring, human-tracking, light

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 CONCLUSION

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

secu-rity 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

Wifi-existing environment

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