Embedded wireless technology solves the scheduling problem of the public transportation system in rural areas
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More than half of the population in developing countries live in rural and suburban areas. Due to the extremely low rate of car ownership, people are very dependent on the current public transport system. The public transport system meets the passenger transport demand to a large extent and therefore plays an important role in the overall rural economy. Despite continuous efforts to take measures to improve the rural public transport system, problems such as long departure intervals, delays and inconsistent schedules still plague people deeply.
time is money. Since the time of the bus system cannot be guaranteed, this will inevitably affect the daily income of local commuters. In addition, students in rural areas can only rely on public transport to go to school, so this problem becomes more prominent.
The main problem is that most rural bus lines do not have fixed schedules. Since many villages are in remote areas, the closest distance to the station may be as long as 40 to 50 miles. Since there is no bus timetable, passengers must use experience to judge when to go to the bus station to wait for the bus. Even if the passengers arrive at the station, they don’t know whether the bus has passed by or not arrived.
This question is very critical in daily life. It is related to whether one can earn a day’s wages and whether it will delay school courses. Usually, you have to wait for several hours, or even the next day before you can wait for the next bus. Passengers must know whether they have missed this bus, and whether they missed the last bus of the day on the route. Only by figuring out this information can people decide whether to wait for the next bus, walk to their destination, or return home—all three options are better than waiting fruitlessly at the bus stop.
The solution needed
Now, let’s take a look at how to solve this problem. Such a solution should include the following points:
* Information transmission: a way to provide key information such as vehicle arrivals and shift frequency is required.
* Wireless connection: Because this solution is suitable for moving vehicles, wireless communication is indispensable.
* Interface: A simple visual interface that ordinary passengers with little culture can understand.
* Inexpensive but robust system: The system must be economically feasible and can ensure continuous operation under rural infrastructure conditions such as power shortages.
* Maintenance and recurring costs: The maintenance and recurring costs of the system should be close to zero.
Solution suggestion
We can provide the above-mentioned key information through the simple, reliable, and low-cost embedded wireless solutions shown below.
The solution actually uses an architecture that includes hubs and nodes. Wireless hubs and microcontrollers including low-cost wireless transceivers are embedded in the bus station infrastructure. The hub is dormant most of the time. The interface for ordinary passengers is a set of simple green LEDs. The number of LEDs depends on the number of buses arriving at the station every day and the frequency of the shift.
The wireless node (transceiver-microcontroller) is embedded in every bus that passes through the station. Before the node transceiver module is installed on the bus, it is equipped with different IDs to ensure that the hub firmware can identify different nodes.
No matter how the bus is dispatched, when the bus arrives, the hub will wake up the node and inquire for data. Through a two-way handshake, the node is verified. The node then sends information such as the vehicle number, arrival time, and shift frequency of the day to the hub.
The hub matches the data and turns on the corresponding LED to display the arrival of the vehicle and its specific shifts on the day. The system firmware will turn off all LEDs at midnight and enter the next day’s cycle. This wireless embedded system improves the comfort and reliability of passengers in the rural public transport system.
Feasibility Analysis
Cost and power consumption are two extremely important factors that determine whether the above system is feasible in rural areas. Most bus stations in rural areas do not have readily available electrical infrastructure. If you want to supply power to the system at the bus station, it often fails the financial approval of the local government. Therefore, wireless nodes must rely on battery power, and in order to maximize battery life, the current consumption of the hub system should be kept extremely low. In addition, the wireless technology we use should be able to stay in a sleep state for a long time, because the hub and the node are in sleep mode between the two trains. In short, the solution can be a low data rate application, and the information packet to be transmitted is only a few bytes. Simple point-to-point wireless technology is sufficient, and the connection distance is only 10 meters. Reliable hub-node communication protocol can meet application requirements. In order to minimize costs, the bill of materials (BOM) should be as simple as possible. After all, the requirements for firmware and memory are very low. The solution runs on the 2.4 GHz ISM frequency band, which ensures that it can be used everywhere in the world. The LED interface should be very simple and intuitive, so passengers don’t need to be literate to understand the meaning.
The main standard in the field of short-range wireless technology is 2.4GHz technology, such as Wi-Fi, Bluetooth, Zigbee and WirelessUSBTM [编者注：注意与 3.1 至 10.6 GHz的 认证无线 USB 相区别]. The solution we recommend is deliberately designed to be extremely simple so that it is feasible in rural areas. In terms of cost and complexity, Wi-Fi and Bluetooth are redundant. The data rate and distance provided by WirelessUSB (250 kbps) are very suitable for this particular application.
Figure 2: Hardware-assisted anti-jamming protocol helps to save power
As shown above, the anti-interference protocol uses the received signal strength indicator (RSSI) built into the radio to monitor the interference strength of other RF signals, and uses quality of service (QoS) detection methods to determine whether a channel hop is required. Compared with Bluetooth, this is an important performance advantage of WirelessUSB 2.4GHz, ensuring that it will only jump to other channels when strong interference is detected. This kind of smart logic greatly reduces unnecessary power consumption than Bluetooth.
In addition, the cost of a Bluetooth wireless device is often doubled compared to a WirelessUSB wireless device and microcontroller (MCU) with the same function. For example, the programmable radio frequency system on chip (PRoC LP) introduced by Cypress Semiconductor requires a single device and few discrete components to realize a complete RF system solution. This high level of integration helps to significantly reduce BOM costs and significantly save space on the printed circuit board. The chip uses frequency agile direct sequence spread spectrum (DSSS) technology to reduce interference. This kind of MCU based on reprogrammable flash memory in the system can change the firmware according to future needs.
Future outlook
As mentioned earlier, a simple low-cost embedded wireless solution can solve the scheduling problem of the bus system in rural areas of developing countries, which helps to save time and money for commuters. Once the public transportation system infrastructure adopts this simple, intuitive, and highly reliable solution, it can also lay the foundation for further development in the future. For example, because the current consumption is very low, we can install solar panels in the bus station, which eliminates the need for electricity or regular battery replacement.
The data collected from each bus can be recorded in the log to optimize the route and schedule. According to the arrival time data of each bus stop, we can adjust bus stops, bus routes and timetables accordingly to meet specific needs. The solution can be further extended to be applied to school buses and suburban taxis.
In urban areas where infrastructure construction is not a problem, bus stations can be connected to the Internet and log data can be sent to the central base station. Through the geographic information system (GIS) software of the base station, the arrival time of subsequent bus stops can be mapped to the route. If commuters can obtain relevant information through the public transport website, they can then decide when to wait for a bus at a certain bus stop.
Rural and suburban public transportation systems will greatly benefit from the aforementioned low-cost embedded wireless solutions. This solution will significantly improve the credibility of the public transportation system and encourage more passengers to choose public transportation instead of self-driving cars, thereby helping to solve the problem of traffic congestion in urban areas.
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