This document presents a system that integrates RFID and wireless sensor networks (WSN) to track buses in bus stations. RFID tags on buses are read by RFID readers located at entrance and exit gates. Motion sensors detect bus arrivals and departures, activating the readers. Reader data is sent via Zigbee wireless modules to a central computer. This allows real-time bus tracking and schedule monitoring without human intervention. Displays inside and outside the station provide passengers with schedule information. The system aims to improve bus operations and passenger experience by providing timely tracking and schedule data.

1. European and Mediterranean Conference on Information Systems 2010 (EMCIS2010)
April 12-13 2009, Abu Dhabi, UAE
Bus Management System Using RFID In WSN
Ben Ammar Hatem, Faculty of Engineering, University of Moncton, NB,
Canada,ehb7342@umoncton.ca
Hamam Habib Faculty of Engineering, University of Moncton, NB, Canada,
habib.hamam@umoncton.ca
Abstract
In this paper we present a novel approach to integrate RFID (Radio Frequency IDentification)
in WSN (Wireless sensor network). WSN is used to support RFID identification process by
extending the read range of an RFID system. Besides, by the use of the WSN we can monitor the
environment of an object and optimize RFID reader’s performance and energy. Then,
methodology to integrate RFID technology, wireless sensor network to form an intelligent bus
tracking application is studied. The proposed system can monitor bus traffic inside spacious bus
stations, and can inform administrators whether the bus is arriving on time, early or late. This
information is then displayed on the different wireless displays inside and outside the bus station.
Keywords: RFID, WSN, Zigbee, integration, tracking, buses
1. INTRODUCTION
Nowadays, travel time information becomes a major component of Advanced Traveler
Information System (ATIS) [1]. The travel time of buses varies depending on several external
parameters such as traffic, snow and accidents. In fact, buses are stuck in traffic and are thus
hampered by the passage of junctions. This makes the management of the bus schedule in the bus
stations a difficult task. Most bus station follows fixed schedules, and don’t uses intelligent
systems for vehicle tracking and control. Many supervisors are deployed at the station to control
the entrance and the exit of buses and prepare the trip sheets containing the schedules manually
which is time consuming and inaccurate. Moreover, transport departments have no visibility over
utilization of its fleet on real-time, which results in underutilization of resources. So, all these
naturally results in avoidable stress, costly errors and sub cost optimal fleet utilization and finally
dissatisfaction and inconvenience to millions of commuters. The provision of timely and accurate
transit travel time information is so important. New technology can help the administrator to
monitor the buses traffic while increasing the satisfaction of transit users and reducing cost
through efficient operations asset utilization. Well-known examples of identification technologies
include Closed-Circuit Television (CCTV) and Global Positioning System (GPS). CCTV can be
deployed at each entrance gate and image processing techniques can be utilized to identify the
arrival of buses [2, 3], where image recognition was performed to detect the bus in the traffic.
Results from this testing has shown poor performance in tracking based detection (~20%
precision). During the past, GPS integrated to Geographic Information Systems (GIS) was used
to monitor buses traffic [4]. GPS receiver communicates with at least 4 satellites before giving the
position of the bus. It gives a very good precision; however, line of sight between the receiver and
the satellites is required otherwise the GPS signal is attenuated. This is a main limitation of this
technology especially when it comes to monitor bus traffic inside an underground bus station.
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2. European and Mediterranean Conference on Information Systems 2010 (EMCIS2010)
April 12-13 2009, Abu Dhabi, UAE
Due to the limitation of these technologies, RFID can be used to track buses. This technology can
be effectively applied for real-time tracking and identification [5]. RFID was developed in the
1940s by the US department of defense (DoD) which used transponders to differentiate between
friendly and enemy aircrafts [6]. Since this time, RFID technology has been evolving to change
the way people live and work. Many previous research projects have explored the possibility of
integrating RFID in different areas, from toll collection [7], agriculture [8], access control [9],
supply chain [10], logistics [11], healthcare [12], and library [13]. RFID technology can response
to our tracking needs that’s why we used RFID in our design to identify buses entering and
leaving the bus station. In this context, this paper presents the developments and the results of a
research project on bus tracking based on the use of RFID technology and WSN. These two
techniques are combined to support identification process by extending the read range of an RFID
system and improving its performance.
2. RESARCH METHOD
The main idea of our research is to integrate RFID technology and WSN to build an intelligent
bus tracking system. Two scenarios of integration have been implemented. In the first one, we
have extended the read range of the RFID system by adding wireless facility to RFID readers.
Each RFID reader is equipped with a wireless module which can transmit data to and from the
reader. RFID reader acts as sensor node: it reads the identification of an object and sends it to the
host application via an ad-hoc network. The second scenario of integration provides RFID readers
with sensing ability. Several motion sensors are installed near each reader to detect the presence
of a tagged object and to command the reader activity. This approach is tested through an
application which can track buses traffic in the bus station. When designing this system, the
following constraints have been considered:
- Modularity and expandability constraints: the system must be modular in design. Both
hardware and software should be divided into small components or modules to ensure
easy scalability for further feature expansions. Modules must be produced independently
from each other, so that changes or the crash of one module cannot affect the other ones.
- Economic constraint: We should take into account performance to cost ratio so as to
design a cost-effective solution
- Environmental constraint: In our design and implementation, we should keep in mind the
impact on environment. Low power consumption devices should be used to keep the
power of the system very low. Energy optimization should be involved in all the design’s
steps.
3. RFID TECHNOLOGY
Traditional RFID system consists of three main components (Figure 1):
Figure 1: General RFID architecture
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- RFID Reader: sends an electromagnetic wave which carries a signal to identify
objects. Then, the reader receives the information returned back by these objects.
- RFID tag: attached to these objects, reacts to receiving the signal sent by the reader in
order to forwarding to it the requested information.
- A computer/database: stores and processes information collected by the reader.
Traditional RFID readers are imitated in their mobility and their potential applications they are
usually connected to the host application via a serial port or via Ethernet.
4. INTEGRATION OF RFID AND WSN
4.1 Wireless Sensor Network
Installing cables to ensure communication between RFID readers and the host application is very
challenging especially in spacious space. Also replacing defective wiring can be extremely
difficult and more costly compared to wireless communication. To address these issues, we
propose to connect wirelessly RFID reader to the host application. There are many wireless
technologies that can be used such as Bluetooth (802.15.3) and ZigBee (802.15.4) to extend the
range of an RFID reader.
Bluetooth has been standardized by IEEE 802.4.15. It allows the creation and maintenance of
short range Personal Area Network (PAN). Bluetooth transfers data at the rate of 1 Mbps, the
range of Bluetooth device is about 10 meters. The main defect of this technique is its high energy
consumption and therefore cannot be used by sensors that are powered by a battery.
IEEE 802.15.4/Zigbee standard [14] offers even better features that meet the needs of WSNs in
terms of energy saving. While ZigBee offers lower data rates it consumes much less than
Bluetooth. A low data rate does not handicap our wireless network where the operation frequency
is low. Besides, one of the main advantages of ZigBee is its ability to "mesh". Mesh networks
enable messages travelling from node to node and arrive to their destination even if one node
fails. It also provides easy maintenance, and can cover large areas [15]. This makes ZigBee an
excellent choice for our WSN. Moreover, the low cost allows the technology to be deployed at
various spot in the bus station to ensure a reliable data transmission. Xbee PRO serie 1 module
has been selected. It is characterized by a range of 10 to several hundred meters and a speed of 20
to 250 kbit/s4.2 Sensing the environment of the reader
4.2 Sensing the environment of the reader
The RFID reader is always inactive. Once a labelled object approaches to the reader, the first
motion sensor detects its movement and an event is sent to the software application via a Zigbee
module by using UART (Universal Asynchronous Receiver and Transmitter). The event is
handled by the RFID middleware and a command is sent back to the RFID reader to enter in the
read mode. Then, the RFID reader reads RFID tag attached to the object and sends its
identification (ID) to a Zigbee module which will relay it to the central computer. Once the object
passes the second sensor, the reading is stopped and the reader returns to the idle mode (figure 2).
Alien ALR-9800 RFID reader has been chosen in our implementation. It provides a flexible
general-purpose input-output (GPIO) system which enables tight integration with external
sensors. Two motion sensors has been wirelessly connected to the reader’s GPIO to detect the
presence of an object. The AMN1 motion sensor was selected because it provides a better
detection range (5m). Motion sensors are accessed by the RFID middleware (which is
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4. European and Mediterranean Conference on Information Systems 2010 (EMCIS2010)
April 12-13 2009, Abu Dhabi, UAE
implemented in the host application) and are used to control the reader activity and to optimize its
energy.
RFID Reader host application
Motion sensor 1 Motion sensor 2 GPIO UART Usb / RS232
Zigbee module Zigbee module Zigbee module Zigbee module
(End device) (End device) (End device) (coordinator)
1 : object detected 1 : GPIO event
1 : Start reading
1 : object detected
1 : GPIO event
1 : Stop reading
Figure 2. Reader’s energy optimization
5. BUS MANAGMENT SOLUTION
Our aim was to develop a real-time schedule tracker system which can inform administrators
whether the bus is running on time, ahead or behind schedule. This information is then displayed
on different displays at the bus station to offer better services to the passengers. It also gives
operator the opportunity to make dynamic changes to the schedule time so he/she can optimize
the utilization of its fleet (buses). To enable such automation in the bus station it is necessary to
identify the arriving and departing buses. In this section, we present system architecture to
monitor buses traffic, integrating WSN and RFID.
5.1 Design approach
Entrance and exit doors are equipped with an RFID reader, antennas and motion sensors. Each
bus has a UHF tag, which is applied inside the windshield. With this system, we can monitor the
buses traffic in real-time and without human intervention. Each time, a bus enters or exits the
station, the RFID reader sends its identification to the central computer where the event is
displayed on a Map. So the supervisor no longer needs to move on place to check the arrival of
bus.
Besides, this system provides a dynamic display inside and outside the station. It advertises
customers to move outside the station to check the arrival of the bus. Each quay (bus stop) is
equipped with a display which is connected wirelessly to a control station. A software application
on the control station keeps track of the entrance and the exit of buses and updates the displays
related to those buses with helpful information.
Figure 3 shows the main components of our system.
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5. European and Mediterranean Conference on Information Systems 2010 (EMCIS2010)
April 12-13 2009, Abu Dhabi, UAE
Led Matrix display in the
waiting room
Timer Database
Entrance gate
Antennas
Central Computer
Wireless Sensor
Motion RFID Reader
Netowrk
sensor
UHF tag
Exit gate
Quay display
Figure 3. Bus station schedule management solution using RFID and WSN
Displays are used to provide passenger with real-time information about buses such as time
remaining and the next trip. They must be deployed on each quay in the bus station and must
ensure effective display of information. LCD and LED technology could be used. LCD displays
provide powerful display capability with up to 16 million colors but they are typically higher cost
than LED based displays. As we are limited to displaying simple alpha numeric characters, LED
display has been selected. We choose UHF Gen2 (Ultra High Frequency generation 2) RFID
which operates between 860MHz to 960MHz bandwidth [16]. UHF is better suited for reading
tag attached to buses. It uses backscatter technique to communicate with the tag and provides
higher read range compared to HF and LF technology. In our design, we used Alien circular
antenna to read RFID tags regardless of orientation. Two antennas are used in each gate, to
communicate with tags. One ensures the emission of energy to the tag and the other receives
energy back from the tag.
5.2 Software contribution
Bus station schedule management software application eliminates any human involvement. It
dynamically manages the time table and bus dispatch for optimum ride ship. It wirelessly controls
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6. European and Mediterranean Conference on Information Systems 2010 (EMCIS2010)
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displays and can also generate auto statistic report. It will automatically alert administrator in case
of any bus’s late arrival. The software includes six modules: Wireless Sensor Network
Communication, WSN Middleware, RFID Middleware, Display Management, Database
Interface, and User Interface. Figure 4 shows the architecture of our software.
Dynamic Graphique User interface
Database XML
interface
interface Application code
DB description
Inside Displays
RFID Middleware Display Management
Quay Displays
Wireless Sensor Network Middleware
Wireless Sensor Network Communication
Figure 4. Architecture of the RFID based Schedule bus management software
The Wireless Sensor Network Communication layer implements Zigbee API communication
protocols which encode/decode data in a formatted packet and supports data buffering, overflow
and transition error control. The API mode is then used to identify the packet’s origin and to
detect packet loss. Wireless remote configuration is also permitted by this mode so we can
remotely manage our network to ensure best operation.
The Wireless Sensor Network Middleware allows our application to communicate with different
types of wireless devices. It serves as a gateway between the application and hardware devices
and it is responsible for delivering all Zigbee traffic to the application. Displays and readers
communicate with the WSN middleware to deliver data to and from the application.
An RFID middleware manages RFID readers and accesses to their GPIO. It also manages
received data from RFID readers by filtering and transforming them into useful data. By
implementing the RFID middleware, management and the configuration of RFID devices are
separated from the application.
The database contains general information about buses and range of RFID identification numbers
referred to them. The database stores also different information about displays and Zigbee
modules. Each display is identified by an ID number queried by the microcontroller which
constitutes the Display’s processor. Zigbee transceivers are identified by their MAC addresses
(64bit number). The database interface provides access to the data using SQL (structured query
Language) and enables the data to be easily presented.
Display management module for the update and the configuration of remote displays using XML
schema.
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7. European and Mediterranean Conference on Information Systems 2010 (EMCIS2010)
April 12-13 2009, Abu Dhabi, UAE
6. CONCLUSION
RFID reader integrated with WSN will benefit from communications and sensing capabilities.
The integration of the RFID and WSN will facilitate the extension of an RFID network
eliminating the need the need of wired installation while reducing cost and saving time. The mix
of these two promoting technologies has been explored in this article to provide a smart solution
managing the bus schedule in the bus stations and offering helpful information to passengers. It is
believed that by the implementation of this system, problems such as underutilization of buses
fleet and long waiting time at the bus station will be reduced. So, both passenger and bus station
administrators will benefit from the system as real time information are provided. It is expected
that integration of RFID and WSN will provide new opportunities for applications related to the
identification of object over a large area. Possible applications of RFID with wireless capability
include parking solution, agriculture and forklift trucks in the supply chain.
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