Vehicle Counting System

Vehicle Counting System

Frequencies	915 MHz,925 MHz
Frequency Range	915 MHz - 925 MHz
Mode	RAW
Modulation	FSK
ACF	—
Emission Designator	—
Bandwidth	10 MHz
Location	Australia
Short Description	Data transmitted from a vehicle counting system installed in car parks. The data is frequency hopping over 10 MHz.
I/Q Raw Recording	—
Audio Sample	—

A small unit is fixed to the road where the cars will drive. It is probably interrogated by the 'zone controller' unit using something similar to RFID. A directional antenna from the zone controller is pointed at the road sensor (the frequency of this is currently unknown). Data is transmitted from the zone controller regularly, even when no traffic is present.

The communication format is unknown, it uses frequency hopping over 10 MHzMegaHertz (MHz) 10^6 Hz.

It appears to be similar to the system described in this website http://www.trafficparking.com.au/vehicle-counting-systems.php and the equipment appears to be provided by http://www.smartparking.com/ (but that website doesn't have much information).

Characteristics

The system appears to be using frequency hopping FSKFrequency-Shift Keying signals that have a very high data rate. Each burst is 5.625 msmilliseconds (.001 of a second) long with a minimum of 0.850ms between bursts. Each burst is a FSKFrequency-Shift Keying burst at 200 kBdkilobaud, kilosymbols per second (ksym/s) with a shift of 200 kHzKiloHertz (kHz) 10^3 Hz. Each burst sends a frame of 1125 bits at a raw data rate of 200 kbpsKilobits per second (kbps).

Signal Analysis

Frequency Hopping, FSKFrequency-Shift Keying bursts zoomed in. Zoom in of one of the bursts. We see the baudrate is ~200 kBdkilobaud, kilosymbols per second (ksym/s). Further zoom in. We manually calculate the symbol rate from the smallest frequency shift and see that the symbol rate is indeed 200 kBdkilobaud, kilosymbols per second (ksym/s).

Frequencies

915 MHzMegaHertz (MHz) 10^6 Hz - 925 MHzMegaHertz (MHz) 10^6 Hz

Raw IQQuadrature signals form the basis of complex RF signal modulation and demodulation, both in hardware and in software, as well as in complex signal analysis.

The IQQuadrature signals form the basis of complex RF signal modulation and demodulation, both in hardware and in software, as well as in complex signal analysis. capture was taken from directly below the transmitter of the vehicle counting system. SDRSharp_20160314_074631Z_920726432Hz_IQ Flinders Uni Vehicle Counting System.zip

Additional Images

A vehicle counting system zone controller installed at Flinders University The on road sensor used in the vehicle counting system at Flinders University.