Research On Interference Suppression In Femtocell Network Based On Spectrum Sensing

With the high speed development of modern wireless communication technology, inthe cellular network, there are almost50%of the phone business and more than70%of thedata business take place indoors, however, the survey find that the vast majority ofhouseholds and companies are faced with the problem of poor indoor signal coverage.Femtocell technology can be used to supplement the macrocell coverage indoors, toprovide users with high quality voice and data services. However, the introduction of thefemtocell causes serious interference of the existing macrocell. Aiming at the interferenceproblem in the two-tier heterogeneous network constituted by femtocell and macrocell, thispaper uses spectrum sensing technology of cognitive radio to detect the empty spectrumresources to allocate to the femtocell, achieves the purpose of suppressing interference andimproving the utilization of spectrum.On the basis of studying the interference scenarios in femtocell network and spectrumsensing theory, this paper proposes a two-tier cooperative spectrum sensing based ondouble threshold, derives the detection probability and false alarm probability of thefemtocell user, gives a two-bit-coding fusion rule of sensing information in femtocellnetwork and specific implementation of the algorithm. Simulation results show that thetwo-tier cooperative spectrum sensing based on double threshold proposed in this paper caneffectively improve the detection probability of single femtocell user, it also can effectivelyimprove the detection performance of the system through the two-bit-coding and fuse ofthe sensing information and strong resistance to noise.This paper also studies the particle swarm optimization, on this basis, this paper gives acooperative spectrum sensing model of multi users multi antennas femtocell system,derives global detection probability of multi femtocell users cooperative spectrum sensing.Under the premise of a given probability of false alarm, using particle swarm optimizationalgorithm in fusion center to optimize the weight allocated to each femtocell user’s sensinginformation, maximize the global detection probability of the system, detect the emptyspectrum resources to allocate to the femtocell, achieve the purpose of suppressinginterference and improving the utilization of spectrum. Simulation results show that theparticle swarm optimization to optimize weight of cooperative spectrum sensing canmaximize the global detection of the system, improve the utilization of spectrum.