In this post I will talk what is cognitive radio and how it works. It is a technology which probably will be used in fifth generation wireless communication system.
Why cognitive radio?
There are a very high demand for greater width band, because greater width band means greater speed. However a crescent width band will cause interference in others bands with others applications. In the figure below we have the frequency applications.
With cognitive radio, can use already established frequencies without causing interference and increase the wireless system efficiency. Also can identify free spaces in the radiofrequency spectrum to establish communication channels. The cognitive radio allow the increase of users without the need of more infrastructure to telecommunication.
What is it?
It is a radio defined by software which can “realize” the environment where it is and adjust the transmission to avoid interference. Since it is a radio defined by software, can change your settings with no change in hardware. It can adjust your transmission depending of already existing transmitters and available frequency spectrum to avoid interference. In the figure below we have a concept of cognitive radio network, where the blocks are spectra occupied by primary users.
The spectrum holes are available areas to secondary users which don`t have a frequency defined by regulations.
How it works?
The spectrum sensing verify the spectrum availability and the user`s presence. The spectrum mobility detect the primary users, keep the communication requirements and request decisions to the spectrum manager, which predict what frequency will be available in what time. The spectrum sharing establish connections in the spectrum holes to secondary users. The figure below shows cognitive radio’s flowchart.
The most important part is to detect transmitter and free areas in the spectrum. The signal is detected, pass through a band pass filter, then by an integer and verify the user`s presence or not.
Another way is use a linear match filter instead of an integer.