I. INTRODUCTIONIn today's world, there is a growing demand for wireless connectivity. But with today's technology, using what's available is inefficient. Much of the spectrum is underutilized, as shown in Figure 1. Due to the inefficient use of spectrum by current spectrum allocation methods, there is a need to develop new methods that enable efficient use of spectrum available. An alternative solution to this is the use of alternative technologies. Cognitive radio (CR) is an available option. The concept of cognitive radio was introduced by Mitoala [2]. CR in general can be defined as the use of licensed spectrum by an unlicensed user when the user is not using it. This is called a spectral gap. CR uses them for data/voice transmission [3]. CR as defined by Haykin is: “Cognitive radio is an intelligent wireless communications system that is aware of its environment (i.e. the outside world) and uses the construction understanding methodology to learn from the environment and adapt its internal states to statistical variations of incoming RF stimuli by making corresponding changes to certain operating parameters (e.g., transmit power, carrier frequency and modulation strategy) in real time, with two objectives main things in mind: highly reliable communication anytime, anywhere; efficient use of the radio spectrum. [4]To clearly understand the concept of CR systems, software defined radio (SDR) training. Traditional hardware-oriented radio systems limit cross-functionality and physical intervention is required for modification. This reduces flexibility and increases the cost of implementation and operation. An alternative to this is software...... middle of paper ......CR-BS environment.5) PS-MS ↔ PS-BS: This link being bidirectional at all times is a connection between MS and BS that must be done in one jump. PR-BS being the master, its function is to coordinate communications in its cellular coverage area and also provide PR-MS access to the backbone network.6) PS-MS ↔ CR-MS: This is necessary to enable interoperability between systems of different types. . Here, CR-MS will become a part of PS by reconfiguring itself.7) PS-MS ↔ CR-BS: This link also serves the same purpose as that between PS-MS↔CR-MS. Additionally, if CR-BS has the capability to run the PS protocol, the PR-MS access service can be provided through it.8) PS-MS ↔ PS-MS: This link may be helpful as an ad hoc network for wireless connection. . This is present in PS. Here, if both nodes have CR capability, this link will mirror that between CR-MS↔CR-MS.