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An Adaptive Subcarrier Sharing Scheme for OFDM-Based Cooperative Cognitive Radios

An Adaptive Subcarrier Sharing Scheme for
OFDM-Based Cooperative Cognitive Radios

MODULES :
·        Node  Formation
·        Primary System Rate and Outage Probability
·        Secondary System Rate and Outage Probability
·        Data transmission
DESCRIPTION:
NODE FORMATION:
The channels over the nodes are modeled as frequency non-selective Rayleigh block fading.The instantaneous channel gain for each subcarrier over different nodes.
Primary System Rate and Outage Probability:            
In other words instantaneous data rate with BER-SC increases, consequently outage probability decreases. With cooperation ST behaves as an adaptive DF relay so as to provide diversity gain to the primary system. we propose an adaptive subcarrier sharing scheme for OFDM-based cooperative cognitive radio system, wherein cognitive (secondary) system helps the primary system to achieve its target rate of communication in exchange for opportunistic spectrum sharing.

Secondary System Rate and Outage Probability:
          Secondary transmitter uses adaptive mode of transmission to relay the primary signal with higher throughput while maintaining the BER constrain. In this work, a joint optimization problem is formulated for selective subcarrier
pairing and power allocation, wherein secondary system uses fraction of its subcarriers to boost the performance.

Data Transmission:
          data transmission is performed hop by hop usually using the form of flooding in flat routing scheme, but only CHs perform the task of data transmission in clustering routing scheme, which can decrease hops from data source to the BS, accordingly decrease latency. In addition, only CHs perform the task of data transmission in clustering routing scheme, which can save a great deal of energy consumption.




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