The Federal Highway Administration of the U.S. Department of Transportation has initiated the Open Source Application Development Portal (OSADP) [1] for releasing connected vehicle applications. Software developers, researchers and ITS practitioners can utilize this portal to address the application needs for state and local transportation agencies. As of now, several ITS applications have been released through OSADP which use the V2X data in some way to offer assistive services, data analysis, and monitoring option through smartphones. For example, LANE-CHANGE [2] application aids in lane change maneuver using cooperative adaptive cruise control. MMITSS-AZ [3] provides real time adaptive signal control for allocating green signal time for emergency and transit vehicles. The MMITSS-AZ application also provides a smartphone application for disabled pedestrians to make a pedestrian signal request for crosswalk. A vehicle monitoring service for weight station is presented in SRI 1.0 [4]. Various analysis applications (e.g. motion analysis, security analysis, driving behavior analysis, etc.) are also presented in CloudThink Motion Logger [5], security analysis [6], SmarTrAC [7]. None of the above applications use Bluetooth connectivity of smartphones with DSRC devices to visualize the vehicular trajectories and speed on a map. In addition, none of these applications use multi-hop V2X communication.Our application has four major components: (i) a transmission application, (ii) a receiver application with a Bluetooth server, (iii) an Android application, and (iv) a set of communication protocols.
A.OBU transmission application The transmission application, specifically the OBU transmission application sends a vehicle’s position, speed, heading direction, mac address, and timestamp. The mac address is sent to categorize and separate packets in the recipient end. The following steps are followed to develop the transmission application: Registering a provider with a PSID (Provider Service Identifier) and PST (Provider Service Table) entry. Building WSM (Wave Short Message) packets using channel, channel rate, channel power, version, security, PSID, priority, and message data. Preparing message data that contain time, latitude, longitude, speed, latitude direction, and longitude direction. Transmitting the WSM packets using txWSMPacket()function.
B.OBU receiver application with a Bluetooth server The receiver application receives packets from other OBUs within its range. The receiver application also acts as a Bluetooth server to send the received packets to the connected smartphone. The following steps are followed to develop the receiver application: Registering a user with a PSID and a PST entry. Creating a Bluetooth server using RFCOMM socket. Receiving packets using rxWSMPacket() fuction. Developing a server thread for writing the received packet data to a smart phone.
C.Smartphone application The smartphone application is the visual representation of surrounding vehicles- their positions, speeds and directions. The application also tracks the position and other dynamics of the vehicle to which the smartphone is connected. For visual representation, google map API is used. The following steps are followed to develop the smartphone application. Creating a client socket using RFCOMM client socket. Creating Bluetooth discoveries to connect with Bluetooth devices. Creating a client read thread that reads the GPS data from OBUs and updates the map by drawing trajectory line, updating marker and camera
D.Communication protocols We developed both single hop and multi-hop communication protocols to transfer packets between DSRC devices. A brief description of each of these protocols is given below: Single hop: A source DSRC device exchanges packets directly to a target DSRC device within its range using the single hop communication protocol. In this scenario, both the source and target DRSCs must be present within a range of 300m radius.Multi-hop: When the source and target DSRC devices are not within the transmission range, they communicate through one or more intermediate forwarding nodes (intermediate DSRCs). An internal routing table is maintained that stores the mac address, position, distance, and a timestamp for each surrounding vehicle (i.e. DRSC).
Our current application describes the architecture and communication protocols for an Android application that enables visualization of real-time vehicle movements on Google map using DSRC and Bluetooth communication. Our future efforts will focus on developing a DSRC-based taxi-hailing application [8] that will utilize both single-hop and multi-hop communication protocols developed through this current research project. It is anticipated that this taxi-hailing application will be further integrated with the IDTO application package [9] and deployed through NYC Connected Vehicle pilot project. Code Shoppy
