Characteristics of Cognitive Networks
The cognitive networks are introduced to fulfill the need of apparent lack of spectrum below the current policy of spectrum management. In America, the right use of wireless frequencies is controlled by the Federal Communication Commission (FCCA). Most of the unused bands to benefit from wireless communications were approved by the FCC. Among new wireless frequencies some of them were officially granted to gangs by FCC, particularly in the Industrial, Scientific, and Medical bands (ISM bands). However, bands in the form of white spaces are filling up quickly, and despite their popularity, yet majority of the wireless spectrum has become licensed. Now primary wireless broadband access the FCC to broadcast their spectral bands and mostly are allotted specific spectrum while unlicensed bands are also rapidly filling. This situation is interpreting a crisis spectral. The latest polls show that many licensed bands remain unused nearly 90 % of the time. There are many complications in recycling the licensed bands and re-lease therefore FCC is considering dynamic frequency assignment as an alternative to reduce the unused spectrum. For this licensed primary bands users may be negotiated on certain terms and conditions to use the spectrum during quite moments while not interrupting the transmission. All depends on the main users that would be willing to share the spectrum on many factors, including the consequences for their own communications.
Importance of Cognitive Radios Networks
Cognitive radios, wireless devices with reconfigurable hardware and software are able to provide these secondary devices with the ability to feel and intelligently adapt their spectral environment. Cognitive radio is one such possibility that is capable to challenge and to understand the limitations and protocols designs and transmission schemes exploit its abilities. Various scenarios, assumptions and other types of cognitive behaviors are observed to get better upper limit for different networks. However, networks accessorized with cognitive radios are capable of having intuitional performance as compared to the networks where they are absent. Different measures have been taken since the cognitive radio shows some capacity to perform miraculously in the networks with their cognitive ability to detect and adapt the wireless environment and opportunistic behavior in the secondary license that are agile cognitive radios allowed to share spectrum with primary users. Cognitive networks are especially designing to improve the networks performance by having awareness of the environment and ability to adapt it.
A hypothesis is made that secondary users if want to share spectrum with main user it can be possible in cognitive networks. The cognitive behavioral users use the primary spectrum can be grouped into three categories each of which operates in varying degrees of knowledge of wireless environment for the secondary users.
Making it sure that the primary users will remain a predetermined level with the support of secondary users. It means that primary users cannot switch to the cognitive users however cognitive networks will be adaptable to the primary spectrum that is the legacy system for primary users.
No interference will be offered by secondary users in a way of primary users and both will act in perpendicular form and will consume the spectrum in two ways; TDMA mode and FDMA mode as well as any other in which both keep promises of no interference.
To conclude, higher the knowledge and basic data about the cognitive terminals will allow attaining higher rates to achieve through cognitive networks. However, the increase in cognitive networks often means higher level of complexity. Future of cognitive networks is dependent on the level of knowledge about the licensing of spectrum and the restrictions poses to the networks.