09-11-2012, 02:19 PM
A Low Cost GSM/GPRS Based Wireless Home Security System
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Abstract
Home security system is needed for occupants’
convenience and safety. In this paper, we present the design
and implementation of a low cost, low power consumption,
and GSM/GPRS (Global System for Mobile Communication
/General Packet Radio Service) based wireless home security
system. The system is a wireless home network which contains
a GSM/GPRS gateway and three kinds of wireless security
sensor nodes that are door security nodes, infrared security
nodes and fire alarm nodes. The nodes are easy installing.
The system can response rapidly to alarm incidents and has a
friendly user interface including a LCD (Liquid Crystal
Display) and a capacitive sensor keyboard. The wireless
communication protocol between the gateway and the nodes is
also suitable for other home appliances. Furthermore, some
methods are taken to ensure the security of system information.
INTRODUCTION
THERE is a growing interest in intelligent home network as a
way to offer a comfortable, convenient and safe environment
for occupants [1]. In order to enhance the occupants’
convenience and safety, home security system is indispensable
in the field of intelligent home network. The requirements of a
home security system include low cost, low power
consumption, easy installation and rapid response to alarm
incidents.
According to connecting mode, home network can be
divided into two kinds: wireless network and non-wireless
network [2]. The wireless technology has some remarkable
benefits comparing with non-wireless technology. For example,
it makes the installation and maintenance easier and reduces
the system cost. Bluetooth [3], ZigBee [4], [5], 802.11 [6] and
wireless USB [7] are the most popular technologies in the field
of home wireless network. [3] introduces a method to form a
home network which provides flexible and dynamic services
via Bluetooth. However, the system mentioned in [3] is high
power consumption and high cost so that it is not convenient to
use in security system. [4] and [5] present how to apply
ZigBee/IEEE802.15.4 to establish a home network that is costeffective
and low power consumption.
THE HOME SECURITY SYSTEM
The general structure of the home security system is shown
in Fig. 1. The system includes two parts: wireless security
sensor nodes and a GSM/GPRS gateway. There are three kinds
of sensor nodes in this system: door security nodes, infrared
security nodes and fire alarm nodes. The GSM/GPRS module
is the interface between the gateway and the GSM/GPRS
network.
The Door Security Node
Door security node adopts magnetic sensor. The sensor
doesn’t need external power supply and has an ON/OFF signal
output according to the distance from magnet to dry spring.
The distance threshold is 16 mm. As the sensor is normally in
ON state, the circuit in Fig. 7 is designed to use a 1MΩ
resistor R1 to limit the circuit current so as to reduce power
consumption. The implementation of a door security node is
shown in Fig. 8.
THE WIRELESS COMMUNICATION
When alarm incidents occur, the nodes will send alarm
information to the GSM/GPRS gateway immediately. If there
is no alarm incident, the gateway and sensor nodes use a
query-reply communication mode. When a node is queried, it
returns its state to the gateway. The communication packet
format between the gateway and node is given in Fig. 13. The
packet consists of Preamble (P), Start of Packet (SOP), Packet
Length (PL), Payload Data (PD) and the CRC16 bits.
Payload data have two bytes. The first byte represents the
identity of security node, the second byte represents the state
of node (0x00000001: “Open” State; 0x00000010: “Close”
State; 0x00000100: “Alarm” State) or query command
(0x00001111) from gateway. Before the payload data is
transferred, it is encrypted with a pseudo security key. The
payload data is decrypted with the same pseudo security key
after received. The security key is generated by GSM/GPRS
gateway and is sent to each node when installing.
CONCLUSION
This paper presents the design and the implementation of a
wireless home security system. PSoC devices and wireless
transceiver modules are adopted. The system has a friendly
user interface and employs some methods to reduce the power
consumption.
Communication of the system is complete wireless, which
makes the system easy to install and use. The system is low
cost, low power consumption and easily operable. In addition,
the wireless transceiver modules enable the system to transfer
other information such as voice and picture rather than just
alarm signals. As a result, the system can lightly be expanded
to other applications.
The system is secured with a login password. As a future
work, we are currently working to establish a more secure
system by researching a proper wireless security protocol.