In a conventional wireless environment, electromagnetic spectrum in the form of frequency bands is explicitly allocated to transmitters and receivers such that they possess a communication medium for the wireless transfer of information.
However, the part of the electromagnetic spectrum that can be used for such transmission involves a narrow band of frequencies. And when the demand for electromagnetic spectrum is very large, an issue referred to as spectrum scarcity occurs, which is where not all communications, connected car or not, can be accommodated.
In a V2X environment, a spectrum scarcity situation can be relatively dangerous, particularly in scenarios where connected cars need guaranteed access to wireless channel bandwidth in order to exchange safety information with each other and the infrastructure around them or if several of the vehicles within the same geographical proximity are operating in autonomous mode.
Consequently, dynamic spectrum access, or DSA, is an approach where portions of unused frequency bandwidth are temporarily “borrowed” by a transmitter and a receiver so that they can communicate information between each other.
In the connected car-V2X scenario, DSA can be used to opportunistically seek out frequency bands that are not used at the moment to send important information without having to wait for some other portion of the electromagnetic spectrum to free up frequency bands. This is especially important in situations such as car accidents and similar emergency scenarios, where these important events will trigger all connected cars and roadside units to start communicating with each other and quickly run out of available bandwidth unless dynamic spectrum access is employed.
Radio intelligence, or cognitive radio, is key to using DSA for connected cars. Cognitive radio systems supporting dynamic spectrum access provide the car the intelligence needed to find and select a frequency in the event of spectrum scarcity.