Assessment of Multiantenna Array Performance for Detecting Bluetooth-Enabled Devices in Traffic Stream

The use of Bluetooth technology for gathering travel time and origin-destination data is becoming increasingly popular due to the large volume of data that can be gathered at a relatively low cost. Currently, data collection can be limited by the relatively low detection efficiency of these devices. This paper investigates the use of multiple antennas at Bluetooth monitoring stations to improve the identification rate of passing vehicles. To test this approach, sensor array configurations with two to five Bluetooth readers were compared to a control consisting of a single reader at the same site. The relative effectiveness of horizontal versus vertical separation of the readers was also investigated. On average, a sensor array with two to five horizontally separated antennas detected between 56% and 123% more unique Bluetooth device MAC addresses than did the single Bluetooth reader in the same location. Vertically separated antennas (two to four) resulted in an average percent increase of 32% to 52% over the single antenna array, which is less than that achieved by a comparable horizontal array. This indicates that there is significant potential to increase the number of passing vehicles that can be identified using Bluetooth technology if multi-reader arrays are used in lieu of the current practice of using a single antenna configuration.