What are the frequency bands assigned to cognitive radio in any CR in terms of standards bands for any application?
The concept of cognitive radio has been proposed with the objective of enabling devices to occupy the spectrum that has been left vacant by licensed users. Therefore, theoretically, any frequency band poorly or discontinuously used over time or space (or other dimensions) would be used for providing unlicensed access. However, in practice, there is very few standards adopting the CR technology. For instance, we find the IEEE 802.11af, IEEE 802.22 and IEEE 802.19.1. All the aforementioned standards are operating over TV white spaces (54 to 60 MHz, TV channel 2; 76 to 88 MHz, TV channels 5 and 6; 174 to 216 MHz, TV channels 7 to 13; 470 to 608 MHz, TV channels 14 to 36; and 614 to 698 MHz, TV channels 38 to 51). The basic idea behind that is that the transition of TV channels from analog to digital has freed up a considerable amount of unused portions of spectrum. In fact, TV bands have good propagation conditions, excellent building penetration and high spectrum efficiency. To my best knowledge, there is no other frequency bands attracting a similar interest.
The concept of cognitive radio has been proposed with the objective of enabling devices to occupy the spectrum that has been left vacant by licensed users. Therefore, theoretically, any frequency band poorly or discontinuously used over time or space (or other dimensions) would be used for providing unlicensed access. However, in practice, there is very few standards adopting the CR technology. For instance, we find the IEEE 802.11af, IEEE 802.22 and IEEE 802.19.1. All the aforementioned standards are operating over TV white spaces (54 to 60 MHz, TV channel 2; 76 to 88 MHz, TV channels 5 and 6; 174 to 216 MHz, TV channels 7 to 13; 470 to 608 MHz, TV channels 14 to 36; and 614 to 698 MHz, TV channels 38 to 51). The basic idea behind that is that the transition of TV channels from analog to digital has freed up a considerable amount of unused portions of spectrum. In fact, TV bands have good propagation conditions, excellent building penetration and high spectrum efficiency. To my best knowledge, there is no other frequency bands attracting a similar interest.
The main objective of CR is to use all frequency bands meanwhile the licensed users' services are not degraded. It means, all frequency bands are free to this technology but white spaces in some bands are more acceptable. In addition, underlay and overlay techniques forces different frequency bands.
what happens when the primary user switches from inactive t active state while the secondary user is in transmission?
As pointed out by the other researchers, CR by itself is a concept rather than a standard.
However, u can check 802.22 for TV white spaces, if u are looking for a full fledged standard with all of its specifications.
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