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11.2.6.1 IrDA Infrared
Infrared data communication is unidirectional and has a short nominal range of about 10 m only. Communication between mobile devices such as personal data assistants (PDAs) using infrared technology is limited to areas within a line-of- sight as IrDA infrared cannot penetrate walls and furniture. The advantage of Bluetooth over Infrared is that it does not have this line-of-sight constraint, since a Bluetooth transmission is omnidirectional. Due to Bluetooth’s greater nominal range of up to 100 m, Bluetooth transceivers do not have to be located near to each other for data transmission as compared to infrared transceivers.
11.2.6.2 IEEE 802.11b and 802.11g
Commonly known as Wireless LAN, 802.11b serves data transmission of up to 11 Mb/s, while 802.11g is extended from 802.11b and serves data transmission of up to 54 Mb/s. Despite the high data transmission of Wireless LAN, it requires too much power from the mobile phones and the high transfer rate is unnecessary for small data transfer applications of mobile phones. Thus, in this project, Bluetooth is a more suitable wireless technology as it consumes far lesser battery power. Furthermore, the amount of data transfer in the project is not sufficiently large to warrant the use of Wireless LAN.
11.2.6.3 New Emerging Wireless Technologies
Zigbee, UWB (ultra wide band) and NFC (near field communication) are some of the new emerging short-range data transfer wireless technologies. From the application point of view, they differ mainly in term of data throughput, transmission distance and power consumption. In term of support and availability, those given for Bluetooth are much more extensive than these new emerging protocols. Some of these new wireless technologies may also be used to complement Bluetooth, for example, the connection initialisation phase of Bluetooth (approximately 3 s) can be reduced to milliseconds using NFC (NFC 2005).
11.3 Design Issues
The target application of Bluetooth Notification System for the Bus Commuter is to overcome any barriers bus commuters may have in identifying an approaching bus to determine whether it is a service that goes to their desired destination and is therefore suitable for boarding.
Those who are visually impaired, physically disabled or elderly will often experience this barrier to independent use of the public transport system. This identification or notification system can also be extended to those who are facing difficulty in using other public transport systems, such as taxis. Under the current transport system, such a commuter may have difficulty in flagging down an
368 11 Accessible Bus System: A Bluetooth Application
approaching bus on time. At the same time, a visually impaired commuter or an elderly person with poor vision is often unable to determine if the right bus is approaching them. In addition, if a visually disabled commuter has boarded the bus, they may have difficulty in determining when the bus has reached their desired destination. These commuters often have to rely on fellow commuters around them for guidance. Thus, their ability to travel independently is greatly hampered.
11.3.1 System Architecture
A solution based on Bluetooth technology is proposed to remove these particular accessibility barriers.
The proposed system as shown in Figure 11.1 consists of three Bluetooth components:
1.A Bluetooth embedded system installed on the bus
2.A Bluetooth server module located at the bus stop
3.A Bluetooth-enabled phone carried by the commuter pre-installed with Java application software
When the user or commuter approaches the bus stop, a connection will be established between their mobile and the bus stop server via Bluetooth connection. Each bus stop is associated with a unique identification (ID) code. The bus stop server will notify the user with the ID of the bus stop. Other information (bus route, frequency etc.) can be accessed from this server as well.
Via the mobile phone, the user will key in the bus number that they are waiting for, as shown in Figure 11.2. Upon receiving this message, the bus stop server will, via Bluetooth, detect the bus once it is within the Bluetooth messaging range and transmit a notification message to the user’s mobile phone to alert the user that the bus they require is coming. An audio message is then played to inform the user that
Figure 11.1. Proposed system architecture
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369 |
Figure 11.2. Bus commuter keys in bus number that they are waiting for into their mobile phone
Figure 11.3. Bus commuter receives notification message that the requested bus is approaching
their bus is now approaching, as illustrated in Figure 11.3. Through the Bluetooth system on the bus, the bus driver can also be notified of commuters waiting for it at the bus stop so that the driver will stop and collect them.
On the other hand, when the commuter (who has boarded the bus already) wants to alight from the bus at a specific bus stop, they can enter their desired destination bus stop ID into their mobile phone. Once the bus has reached the designated bus stop, the bus driver is alerted and is able to let the commuter alight.
11.3.2 Hardware Requirements
Based on the proposed architecture, a hardware prototype was developed. The list of hardware used is given in Table 11.3.
11.3.3 Software Requirements
A suitable software development kit is required to program the Bluetooth protocol stack via the USB Bluetooth adaptor, which is to be connected with the PC server.
Java Bluetooth API, or JSR-82 (JAVA 2005), is used as the preferred implementation of the Bluetooth protocol stack. The key reasons for this preferred choice are
370 11 Accessible Bus System: A Bluetooth Application
Table 11.3. List of hardware used in the project
Components |
Description |
|
|
PC Server (Bluetooth Server) |
The PC server that waits for client (mobile phone) |
|
connection to send the requested bus number |
Bluetooth Adaptor (Bluetooth Server) For Bluetooth connectivity, the PC server needs to be connected to the USB Bluetooth adaptor. The adaptor provides the radio hardware for proper Bluetooth connection
Ericsson Bluetooth Radio Kit |
The Ericsson Bluetooth radio kit is used to poll for |
(Bluetooth Server) |
Bluetooth addresses of devices in the vicinity |
Mobile Phone (Bus commuter) |
A phone that supports JSR-82 (Java Bluetooth API) and |
|
JSR-135 (Java Multimedia API) for Bluetooth connection |
|
and to play audio notification when the requested bus |
|
approaches the bus-stop. The models used in the project |
|
were Nokia 6630 and 6230 |
Ericsson Bluetooth Radio Kit (Bus) |
The Ericsson Bluetooth radio kit gives the unique |
|
Bluetooth address present in each bus. This allows the |
|
Bluetooth bus-stop server to identify the requested bus |
|
number |
|
|
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371 |
Table 11.4. List of Bluetooth software development kits. Blue Cove (highlighted) was chosen for the project
Company |
Java platforms |
Operating systems |
Price |
|
|
|
|
Atinav |
J2ME, J2SE |
Win-32, Linux, Pocket PC |
US $ 4999 for |
|
|
|
10 licences |
Avetana |
J2SE |
Win-32, Mac OS X, Linux, |
E 25 for 3 licences |
|
|
Pocket PC |
for Win-32, |
|
|
|
Free for Linux |
Blue Cove |
J2SE |
WinXP SP2 |
Free |
|
|
|
|
JavaBluetooth.org |
Any platform that |
Win-32, Mac OS X, |
Free |
|
supports javax.comm |
Linux |
|
Rococo |
J2ME, J2SE |
Linux, Palm OS |
E 2500, |
|
|
|
free with limited functions |
|
|
|
for students |
Bluez |
J2SE, C |
Linux |
Free |
|
|
|
|
that JSR-82 is independent of the manufacturer’s Bluetooth radio design and it is independent of operating platform.
This implies that it has a standard, fixed set of APIs that is non-proprietary as long as the Java Virtual Machine is installed. However, it is known that, this has not turned out to be completely true for applications that run on different makes of devices. Different device vendors will have slightly different implementation of mobile information device profile (MIDP) (Yuan 2003).
Currently, there are a number of established Java Bluetooth protocol stacks for various operating systems. Table 11.4 shows some of the more common stacks and the corresponding programming languages to access the stacks.
BlueCove, an open-source Java Bluetooth stack for Microsoft Windows XP Service Pack 2 as illustrated in Figure 11.4, was chosen due to its relatively free licence (under open source agreement). Microsoft Bluetooth API stack is incorporated in Windows XP SP2. This stack is a socket-style (WinSock) C API that allows any C-based applications to operate a generic USB Bluetooth adaptor. However, there
Figure 11.4. Architecture of Blue Cove in a Microsoft Windows environment