Software Radio - Smart CAR

Software Radio

This layer works in two modes: Transmission and Receiving modes.

Transmission mode:

Generate sinusoidal signals of the appropriate frequencies that corresponds to the taken decision.

Receiving mode:

Microcontroller sends 56 bits every 1/3 second. If the transmitted bit is "1", microcontroller sends a 1 KHz signal for 3/4 msec, and if the transmitted bit is "0", microcontroller sends a 3 KHz for 3/4 msec. So the total frame time is 56 bits x 0.75 msec = 42 msec.

in DAS, we used 8 KHz ADC to sample the incoming signal, so the total number of samples we have is 42 msec x 8KHz = 336 samples.

this layer perform the following functions:

	Detect start of transmission, This is done by detecting the frequencies components at 1 KHz and 3 KHz and assume transmission if the difference between these two components exceeds a Threshold.
	After Detecting start of transmission we store the next 336 samples in a buffer.
	Partition this buffer to 6 samples' windows
	Perform Fast Fourier Transform (FFT) on each window and estimate the transmitted bit. if the main frequency is 1 KHz then the received bit is estimated to be "1". If the main frequency is 3 KHz then the estimated bit is "0".

you can find the FFT code we used in downloads section.

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