Function specific antennas in cognitive radios

Abstract

Air interface operation of the CRs can be classified into two main functions. One is the sensing or RF Spectrum scanning function and the second is communication or transceiver function. These two functions are performed by a single physical air interface i.e., antenna or antenna arrays and their allied RF circuitry, through interleaving or TDM. This sharing of a single resource between the two essential functions causes interruptions in communication reducing net throughput despite availability of the spectrum holes and bandwidth. The achieved throughput therefore remains much below the theoretically possible throughput. This paper aims at introducing a technique of parallel and independent execution of the two essential functions using two separate dedicated antennas or antenna arrays. The duty cycle of sensing function will be shorter by addition of intelligence or learning added to it thereby economizing on power and other resources. This technique is different from other proposed techniques, available in the literature, suggesting usage of multiple antennas to achieve spatial diversity, temporal diversity or resolution enhancements i.e., all the antennas or the array performing either sensing or communication through interleaving. Simulation of technique presented herein resulted in two fold gains firstly, increased throughput nearing theoretical possible and secondly continuum in operation or communication of CR peers.