WSN application – public transport
I recently talked to a person who is familiar with BMTC’s bus location system. The system uses GPS+GPRS to provide real time updates on the location of each bus operated by BMTC in Bangalore. Looks like the system is not working because of problems with cellular coverage, GPS accuracy, maintenance and the recurring cost of all the data traffic. He suggested a simpler alternative. Install a low power radio in each bus and at each bus stop. When a bus stops at a bus stop, the radio node on the bus sends a message conveying the unique id of the bus. The low power radio at each bus stop will be connected to a GSM modem. The information about each bus which stops at a bus stop will be sent to BMTC over the cellular network. BMTC customers can get the data about each bus on their cell phones. Each bus stop can also display information about every bus which stops there. The cost of equipping each bus with a low power radio is not much compared to a GPS/GPRS module. Over 6500 BMTC buses run everyday. The number of bus stops is far less which means the number of GSM modules required is also less. The data traffic will also be less. Data will be sent over the cellular network only when a bus arrives or leaves a bus stop instead of say every 5 to 10 minutes in the earlier system.
WiSense radios operating in the 865-867 MHz are well suited for this application. The nodes can run on couple of AAA batteries for more than a year. This radio can be installed inside the bus in a location where it is not tampered with. A GPRS modem can be easily integrated with a WiSense node.
WiSense nodes at bus stops can also be equipped to collect environmental data such as temperature, humidity, ambient light and common pollutants.
Many bus stops have a power connection for lights. The low power radio + GPRS node at these bus stops can be AC powered with battery backup.
The radio nodes on each bus can be solar powered if the node is attached to the roof of the bus. This will increase the cost since these nodes require a robust weather proof enclosure.