In cognitive radio networks, unlicensed secondary users are expected to sense RF spectrum to find idle bands and access those idle bands without creating any harmful interference to licensed primary users. However, spectrum sensing for secondary users in diverse/heterogeneous frequency bands is challenging as secondary users are considerably constrained by limited power, memory and computational capacity. Fortunately, the advent of cloud computing has the potential to mitigate these constraints due to its vast storage and distributed computational capacity. When sensed data is small, secondary users can process the data by themselves. However, for big data when secondary users sense wide-band channels, the processing and analysing would take more time than the round-trip-time needed for processing and reporting back by cloud computing platform. Thus, using the context, secondary users can decide whether it is efficient to offload the data into cloud computing platform or analyse by themselves.
Furthermore, cloud also stores the geolocations of idle channels into the spectrum database in a distributed manner. When secondary users want to access RF spectrum opportunistically, they search the spectrum database for idle channels by reporting their own locations using a dedicated link. Cloud controller compares the location of secondary users with that of idle channels and reports the list of channels that are within the tolerance distance. To reduce delay while accessing spectrum database, distributed cloud computing can be deployed based on the user density, which can be easily monitored by the cloud controller. Alternatively, distributed cloud controller can offer a list of RF spectrum for a given location and time so that the secondary users can access available idle channels for opportunistic communications as a hotspot or Radio-as-a-Service feature. There are several benefits of integrating cloud computing with cognitive radio networks. Thus, cloud-assisted cognitive radio network is expected to be the backbone of future wireless systems operating in heterogeneous wireless bands.
