Simulation Of A Cooperative Protocol For Common Control Channel Implementation
No Thumbnail Available
Date
2014
Authors
Aishah Thaher
Shymaa Khalaf
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Abstract Cognitive Radio Network (CRN) is a group of opportunistic users communicating with each other using the spectrum holes, a spectrum hole is a part of the licensed spectrum not used by the owner for a period of time, the concept of cognitive radio networks was introduced to increase the spectrum usage of such underutilized bands, the opportunistic users are called secondary users (Cognitive Users) and the licensed owners of bands of spectrum are called primary users. In a CRN, the Cognitive Users (CUs) communicate only in those frequencies in which the primary users (PUs) are inactive. So, the CUs should scan for the unused bands (channels) from time to time, this process is called spectrum sensing, after this stage, every CU has a list of free channels, the list of free channels may differ from one CU to another, two CUs can communicate if there is at-least one common channel in their free channel lists, since the unused spectrum is shared among a group of independent users, there should be a way to control and coordinate access to the spectrum, this can be achieved using a centralized control or by a cooperative distributed approach. In a centralized architecture, a single entity, called the Cognitive Base Station (CBS), controls the usage of the spectrum by CUs , the Cognitive Base Station (CBS) gathers the information like the list of free channels of each node either by sensing its entire domain or by integrating the individual CUs sensed data, it maintains a database of all the collected information, when two CUs want to start a session, they request the CBS for channel allocation, the CBS looks into the list of free channels of each CU in its database and assigns a channel which is common to both of them[1], the database has to be updated regularly since the list of free channels will change with PUs traffic, the negotiations between the CBS and CUs are usually assumed to be carried on a dedicated control channel . Intuitively, a separate dedicated channel for control signals would seem a simple solution. But a dedicated CCC has several drawbacks. Firstly, a dedicated channel for control signals is wasteful of channel resources. Secondly, a control channel would get saturated as the number of users increases similar to a multi-hop network.Thirdly, an adversary can cripple the dedicated control channel by intentionally flooding the control channel. So it was suggested to choose one of the free channels as the control channel, when PU of the chosen channel returns, a new control channel is picked, But nothing was mentioned about how the first node contacts the CBS and how would it be informed about the chosen control channel for the first time. In the second type of network architecture which is a distributed (multi-hop) scenario, the CUs have to cooperatively coordinate to coexist and access the free channels, the information sensed by a CU should be shared with other users in the network to enable certain essential tasks like route discovery in a CRN. Since, each CU has multiple channels to choose from, a distributed CRN is a multi-hop multi-channel network with dynamic channel set for each user. In a multi-channel network, the control information like the choice of the communicating channel is negotiated on a pre-defined common control channel. Again, dedicating a control channel for the entire network is not a good idea for the above mentioned reasons and choosing a free channel as the control channel might not work because the chosen channel might not be free with all the users. Addressing and solving the Network setup problem is the motive of this Project, the proposed mechanism is extended to a multi-hop scenario in which a CU searches for another CU.