The EkoBus system deployed in the cities of Belgrade and Pancevo is made available for experimentation on IoT data level. The system utilizes public transportation vehicles in the city of Belgrade and the city of Pancevo to monitor a set of environmental parameters (CO, CO2, NO2, temperature, humidity) over a large area as well as to provide additional information for the end-user like the location of the buses and estimated arrival times to bus stops.
An overview of the EkoBus architecture
Every IoT node (sensor) in the system is described by its set of capabilities (characteristics, parameters, availability...), which are published and stored in the Resource Directory (RD). Resource Directory stores dynamic information about all available resources in the system at a given time, so that they are available to the end users (applications). Resources make measurements and periodically send the results to the server application for further analysis and database storage. Web and Android application collect information from the resources and perform their visualization (location of the vehicles and atmospheric measurements). It is also possible to request information about the arrival time of the next bus on a certainline to a certain bus stop via SMS or USSD and to receive that information via SMS. The SMS module is responsible for this feature. Analysis of the stored data is used for various traffic calculation and prediction. Accordingly, additional information is available from the MYSQL database: Static data: geo locations and names of the stations, geo locations of curves and semaphores on the bus route, bus timetables, IMEI of the GPRS modules which are mounted on the buses, average time that bus spends at the specific station, initial average time of bus travel between two consecutive stations; Dynamic data: calculated average time of bus travel between two consecutive stations for the different part of day and week.
Therefore methods and tools for experimentations are:
• Web interface – Web application is responsible for displaying bus locations, bus arrival time information and data received from environment and gas sensors in a web browser, and can be extended in order to provide public survey i.e. feedback from the end user; or additional services Application is calling methods exposed by Data control centre (bus information web service). The data is obtained in XML format.
• Mobile application is similar to the web application, providing the visualization of the current location of all vehicles in the system as well as the measurements for the end-user with mobile phone.
• SMS/USSD – end-user can query the system using USSD or SMS
• Database and offline analyzer – database data that can be used for new offline traffic analysis procedures. Module for offline data analysis is responsible for updating the data in database with statistics obtained during previous measurement period. This information is used by the Traffic management agency of the City of Belgrade and Pancevo to optimize the public transport system.
The following is offered to the experimenters:
• Access to historical data stored in the database. It is made available via dedicated Resource End Points utilizing simple REST interface that allows extraction of the measurements for a given period.
• Direct access to IoT nodes is not available. It is also not possible to change the code or configuration of the IoT nodes.
• In Belgrade and Pancevo, 5 and 60 devices are deployed respectively.