Design Article
Simple embedded wireless resolves rural public transport scheduling
Mahesh Kiwalkar, Cypress Semiconductor
10/9/2008 2:51 PM EDT
More than half the population in developing countries lives in the rural and suburban areas. Because car ownership is very low, the population relies heavily on the available public transportation system. Bus transport largely serves this demand of passenger transportation and thus plays a significant role in the overall rural economy. Several efforts have been made to improve this system but it is still largely plagued with low frequency, punctuality, and schedule inconsistency.
Because time translates to money in trade, relying on the accuracy of the bus transport schedule affects the daily income of many of the day laborers in these areas. This problem is further compounded as students depend on this sole mode of transport to attend classes at school.
The biggest issue is there is no set schedule in place for most of these routes. With many villages in remote areas, the closest destination could be 40 to 50 miles away. The unavailability of a schedule puts the load on the passenger to time his or her arrival at the bus stop empirically. When the passenger gets to the stop there is no way of telling whether the bus passed the stop or is yet to arrive.
Because this is a question of earning daily wages or missing school, it plays a critical part in daily life. Often times the next estimated bus arrival is few hours later or probably next day altogether. Vital information is whether the passenger missed the bus and if that was the last bus visit for the day for that particular route. The options are waiting for another bus, making the arduous walk to the destination, or returning home—all three of which are better than a fruitless wait at the bus stop.
What is needed
So let's look at what could possibly solve this issue. Key points needed in the solution would be:
Proposed solution
The critical information mentioned above can be made available through simple, reliable, low cost embedded wireless, shown below.
Essentially the solution is based on a hub and node architecture. A wireless hub consisting of a low cost wireless transceiver and a microcontroller are embedded in the bus stop infrastructure. The hub will typically sleep for most of the time. The interface to the average passenger is a simple set of green LEDs—the number of LEDs depending on the number of buses that visit that stop per day and their frequency of visit.
The wireless node (transceiver-microcontroller) is embedded in each of the buses which visit the bus stop. Before the node transceiver modules are installed in the buses, they should be assigned non-identical IDs, which allows the hub firmware to differentiate between two nodes.
Irrespective of the schedule they follow, when the bus arrives at the bus stop, the hub wakes up and queries the node for data. A two way handshake takes place to authenticate the node. The node then relays data information to the hub such as bus number, arrival time, and frequency of the visit for the day.
The hub matches the data and switches on the corresponding LED to indicate the arrival of that particular bus and that particular trip of the day. The system firmware switches off all the LEDs at midnight for the next daily cycle. Having such a wireless embedded system will thus make the bus transportation system more comfortable and reliable for its rural passengers.
Feasibility and viability
Cost and power consumption are the two parameters of paramount importance for the feasibility of such a system in rural areas. Majority of the bus stops in rural areas do not have electrical power infrastructure readily available. Providing power to the bus stops exclusively for this system will not be a financially justifiable investment for the local government. Thus the wireless hub must run off batteries. To maximize the life of the hub system before having to change the batteries, the current draw of the system should be very small. Additionally the wireless technology employed should have the ability to sleep for a long time, because, between consecutive bus arrivals, the hub and nodes will be in a sleep mode.
Keeping it simple, the solution can be a low data rate application and information packets can be just a few bytes. A simple point-to-point wireless technology is all that is needed. Range of about 10 meters is sufficient. A reliable hub-node communication protocol will drive the application. To minimize cost, bill of materials (BOM) should be minimal especially since there are no demanding firmware or memory requirements. Having a solution operating in the 2.4 GHz ISM band will allow its unrestricted worldwide implementation. Providing LEDs gives a simple visual interface and does not need the passenger to be literate.
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