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Cognitive Radio Ad hoc Network (CRAHN) was a versatile, intuitive radio and network technology that can sense the available channels in the wireless spectrum and will adjust the transmission parameters in a way that it can have multiple communications to run in parallel and also will help to improve the behavior of radio spectrum. In the CRAHN there are many issues that needs to addressed major of them being spectrum scarcity due to the fact that the range of this network will be very short for which we cannot allocate much spectrum as there will be a possibility of not using it or reserving it for Primary Users (PU’s) who may not be active at all times and if we allocate more spectrum at peak times it could be advantage but at majority times it will be unused. We have done a comparative study on various available protocols and found that AODV is close to address the above issue. In AODV (Ad hoc on Demand Vector Routing) is a category of Reactive protocol where it will not keep track of any route. The route will be just established whenever any intermediate node has some data to send. Once the data gets successfully transmitted then it will no longer record the address. This property is carried out with the help of maintaining sequence numbers between every pair of nodes. The existing system CRAODV-S mainly focused on security based on trust values, where the mechanism of assigning this value was given based on the Secondary Users(SU’s) activities. If the trust value was a bit high than the threshold value then it will be chosen for transmitting messages compared to the remaining nodes with less trust value. This trust value will not be assigned to Primary Users as they will be trusted parties for the network. Based on this trust value the nodes can be categorized as healthy nodes and malicious nodes. The routing also depends on the trusted value of the neighbors for forwarding or receiving a message. In our proposed model CSR-AODV for better security and integrity we have implemented cryptographic techniques in terms of security by using RSA-32 bit and integrity using SHA-III for minimizing the loss of data. Security characteristic is provided by selecting the best optimal route from source to destination and when any intermediate route or node fails then to establish another route for this message transmission is carried out using random key generation. The performance of CSR-AODV and CRAODV-S is assessed for three kinds of routing structure in terms of average throughput, end to end delay, packet delivery ratio and routing overhead for satisfying different requirements from users. The routing structures on which the experiment was carried out are a) Single radio multi-channels b) Equal number of radios and channels and c) Multi-radios multichannels. The simulation result shows that our proposed model gave significant improvement in all performance metrics except for the case of average throughput in single radio multi channel. So this model will be an ideal choice for CRAHN. Key words: CRAHN, AODV, Trust Values, CRAODV-S, Security, RSA 32 bit, Integrity, SHAIII. Introduction Cognitive Radio Networks are capable of effective utilization of the spectrum band that has become a scarce resource of late for wireless networks. They use Cognitive Radios for this purpose. The term ‘Cognitive Radio’ was introduced by ‘Joseph Mitola’. So it is also called as ‘Mitola Radio’ . The cognitive radio has two characteristics – Cognitive Capability which is sensing vacant spectrum by using sophisticated methods such as autonomous learning and reconfigurability which enables using different spectrums for sending and receiving data by using different data access technologies. With the help of these two characteristics, cognitive radio makes use of spectrum holes which are the unused unlicensed band of frequencies . When a primary user comes back, the secondary user should vacate the channel without interfering .
The proposed project met with the objectives, that was to investigate and compare the network performances of CSR-AODV and CRAODV-S routing protocols in CRAHN and analyze performance based on the parameters of average throughput, end to end delay, packet delivery ratio and finally routing overhead. To evaluate the above stated performances we have implemented them in 3 types of routing structures, the structures that are considered are single radio link consisting of multiple channels, equal number of radio links and channels and multi-radio links with multiple channels. After thorough experimentation on the discussed models and performance parameters, data was collected and observed. Based on the results of experimentation we can conclude that CRAODV-S routing protocol was proved to be more efficient for implementing in single radio link and multiple channels structure. The performance improvement was due to increase in optimal total average throughput. CSR-AODV routing protocol was proved to be more efficient for implementation in the remaining two routing structures compared to CRAODV-S.
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