Abstract: a network is known as WIRELESS SENSOR

Abstract: A network consisting of sensors such as
temperature, pressure and sound are densely distributed to monitor physical or
environmental conditions such a network is known as WIRELESS SENSOR NETWORK
(WSN). The sensor data is transmitted to network coordinator which is the heart
of the wireless personal area network. In the latest developments, actuators
and sensors are combined to form a wholesome system. ZigBee is newly developed
technology that works on IEEE standard 802.15.4. The low data rates, low power
consumption and low cost are its features. WSN is includes the ZigBee co-ordinator,
ZigBee router and ZigBee end device. The sensor node’s information in the
network is sent to the coordinator, the coordinator collects the sensor’s data,
stores the data in memory, processes the data, and routes the data to the
appropriate node.

Keywords: Wireless Sensor Network, ZigBee, Routing,
Protocols, Coordinator

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I.INTRODUCTION

Nowadays,
wireless sensor network technology has developed a lot, providing wide range of
applications. These wireless sensor networks can be used where the humans
cannot reach, also in many areas like smart hospitals, smart homes and even in
traffic monitoring. 1The IEEE 802.15.4 ZigBee standard provides a low cost,
low power consumption standard for wireless communication. Unlike the other
networks such as Wi-Fi which use more bandwidth and consumes more power .The
WSNs are reverse of that. 3The main aim is to provide a communication which
is of low cost and to the devices deprived of infrastructure.

In
big Warehouses, it is difficult to find the empty places .The locations of the
empty racks are displayed at the entrance points by the help of the LCD. This information
is provided and routed via star network. The sensing units consist of IR and
PIR sensors..

II. LITERATURE SURVEY

1. Nidhi Patel, WSN is extremely flexible in nature. It also
offers excellent features such as low cost, fault tolerance, high sensing
fidelity. These are mainly used for developing remote sensing applications.

Sensor network introduces certain constraints like fault
tolerance, scalability, cost, hardware, topology change, environment and power
consumption which we should aim to overcome.

2.Sandeep Kaushik, Monitoring and
controlling platform was established by the system based on ZigBee and
Bluetooth. Both wireless standards have their own advantage and applications
and drawbacks based on certain parameters but ZigBee seems to be more
economical and effective network on comparison with Bluetooth. ZigBee offers
lower power consumption and high range.

Hence
for food storage system network based on ZigBee is more suitable than Bluetooth
network

3.Geetha A, A
wireless sensor system making use of extremely low powers have been designed at
a reduced cost. Most reliable system which is very quick. Installation is also
quite fast. It can be used to improve the system scalability and can be used to
extend accurate position of underground miners in future by making use of
ZigBee wireless positioning devices     

 

4.Action Nechibvute,To achieve a seamless transition from wired to
wireless communication, there is need for efficient integration of the WSNs
into existing automation. This is also required for achieving simple
deployment, commissioning, and maintenance.

WSN-enable
automation systems will get more popular mainly due to lower cost increased
flexibility and scalability which cannot be obtained from traditional all-wired
automation systems.

II. TEHNOLOGY USED AND ZIGBEE PROTOCOL

2ZigBee
is a wireless network which has been developed recently to work on low power,
low data rate, low cost personal area network. Hence because of this its
importance and application has increased immensely in recent years. This
network is based on the IEEE 802.15.4 standard.
This IEEE 802.15.4 works on low data rate standard for MAC layer and physical
sub layers. ZigBee is hence used to provide low cost and low power connectivity
for certain equipment which require very long battery life for about several
months to years and which of those not requiring data transfer rates as high as
those enabled by Bluetooth. Larger networks can also be implemented using
ZigBee on comparison with Bluetooth’s network.

ZigBee
is a standard developed for wireless radio networks in monitoring and control
fields. To meet the following principal needs this standard was developed by
ZigBee alliance:

·        
 Low cost

·        
 Less power consumption

·        
 Uses radio bands

·        
 Cheap and easy installation

·        
 Flexible and extendable networks

·        
 Smart  network set-up and message routing

 

The characteristics of physical and MAC layers are defined by ZigBee
standard 802.15.4 for low rate wireless personal area networks (LR-PWAN). The
node architecture is divided into a number of structural blocks called layers.
Each layer offers services to its upper layers and gets services from its lower
layers. Each network node’s architecture is comprised Physical (PHY) layer and
Medium Access Control (MAC) sub layer. There exists a layer called Service
Specific Convergence Sub layer (SSCS) on top of all these layers which
interfaces the MAC sub layer to the logical link control sub layer and other
upper layers such as the networking layer which facilitates network
configuration, modification , message routing, and application layer, which
provides intended function of device. These LR-PWAN standards are undefined for
other layers but defined only for PHY and MAC layer.

 

Fig 1: Layers of IEEE
802.15.4

 

Two
services are provided by the physical layer, They are:

1. PHY data service and

2. PHY management service interfacing to the Physical Layer Management
Entity (PLME).

The transmission and reception of PPDU (PHY Protocol Data Units) across
the physical radio channel is enabled by this PHY data service. Some of the
tasks performed by physical layer of IEEE 802.15.4 are as follows:

 

·        
Energy
Detection (ED)

·        
Activation
and deactivation of the radio transceiver

·        
 Link Quality Indication (LQI)

·        
 Clear Channel Assessment (CCA)

·        
 Channel Frequency Selection

 

Functions performed by the protocol is that
it allows instantaneous channel selection, a channel check function in search
of a beacon, link quality indication, receiver energy detection and channel
switching as well.

 

Two services provided by the MAC sub layer,
are

1. The MAC data service. This supports the
sending  and receiving of (MPDU) MAC
Protocol Data Units  across the PHY data
service.

2. The MAC management service interfacing
to the MAC sub layer Management Entity (MLME) Service Access Point (SAP)
(MLME-SAP).

 

Beacon
management, channel access control through the Carrier Sense Multiple Access
with Collision Avoidance (CSMA/CA) scheme, collision-free time slots
management, frame validation, acknowledged frame delivery and node association
and release are some of the features of MAC sub layer

IV. SYSTEM ARCHITECTURE:

Low
cost and low data rate networks using zigbee are growing in demand. The
wireless sensor networks are used all spheres of the technical world now. In
logistics, the technology has helped in the management of large warehouses. The
e-commerce industry is also looking towards WSNs.The various configurations
such as mesh, star and distributed are used in many useful purposes.

A. Proposed System:

Our
main objective is to eliminate the manual checking of free spaces for storage
of new items. The system also takes care of the size of items. The doors are
enabled with a 20x4lcd display to how the status of the racks. This data is
communicated by the ZigBee Xbee pro s2 from the co-ordinator to the entrance node.
The data at the co-ordinator is collected continuously.

Our
system does not use an extra microcontroller at the sensor nodes. Hence the
system is low cost, less complex and less power. The systems use the IR sensors
for the detection of empty or occupied racks .The systems used in this system
are ARM7 LPC2148 controller,20×4 LCD display,DS1307 Real Time Clock, IR sensors
and PIR sensors. For communication we use the ZigBee Xbee pro s2.

B. Block Diagram:

Fig
2: System Bock Diagram

The
figure describes the general block diagram of the entire system. Here we have
taken one co-ordinator and three routers. The two routers are placed at the
racks and update the status of the racks to the coordinator. The third node at
the entrance is used to show the information through a LCD .The communication
is set up by using the ZigBee. The LPC2148 is used at the co-ordinator to
process and store the data. The controller at the gate is attached with the
level sensors to detect the size of the item.

V. SOFTWARE IMPLEMENTATION

We are using embedded C for programming in Kiel
software and Flash Magic for dumping the code into LPC2148. Digi XCTU is used
for ZigBee network formation. Hercules software is used for user displaying the
router information at the coordinator.

The
network is formed by using the same PAN number at all nodes. The coordinator node
operates in API mode and routers operate in AT mode. This is done by using Digi
XCTU software. Identical sampling rate is set to send the information from the routers.
Here we were updating the status for every 5seconds.

The
received data at coordinator is in packet form which is of 17bytes. The
received packet consists of 1byte start delimiter whose value is 7E , 2bytes of
length ,one byte to indicate the frame type,64bit source address ,received  data and a checksum value.

The
possible ways of communication is shown in Fig 3.

Fig
3: possible ways of communication

Here we
are using the star network for communication.

The
UART ports are used for user interface. These were initialised using UART
register, an interrupt is raised the when there is a transmission and
reception. The timer interrupt is used (using the timer registers) for RTC. MAX
232 is used for UART connection between ZigBee and LPC2148, MAX232 performs TTL
logic conversion.

The
pins are selected for a particular operation using pin select register in LPC2148.At
routers, pins DOI1 and DOI2 of Xbee are used for data transmission from the
sensors. This operation is demonstrated by the help of a flowchart in figure 4

 

Fig
4: Flowchart of the System

 

VI. RESULTS

The
figure 5 shows the result at the coordinator using Hercules software.

Fig 5: Router status at coordinator

Once
the data is received it is converted into hex value, using the address the
source is found and status is updated and the information is sent to entrance
node which will be displayed in LCD as shown in the figure 6.

Fig 6: LCD
display at entrance

CONCLUSIONS

A
wireless sensor network as we know has many excellent features such as fault
tolerance, low cost, high sensing fidelity and is also greatly flexible in
nature. All of these features can be wisely used for developing applications in
remote sensing. This wireless system is used to establish monitoring and
controlling platform using ZigBee. The central monitoring unit will receive the
monitoring data from all the sensor units and stores them in the database.
ZigBee is preferred because it is more economical and effective compared to
Bluetooth. And offers low power consumption and high range network. But there
are certain constraints when we consider sensor networks which should be
overcome. Some of these may include constraints introduced by scalability,
hardware, topology change, environment and power consumption. Some new wireless
ad hoc networking techniques must be incorporated as we know all these
constraints are highly stringent and specific for sensor networks