The Research On The Power Allocation And Channel Selection Of The Waveform Design In The Spectrum Sharing System

This paper based on cognitive radio systems studies about the power allocationand channel selection of the spectrum sharing and the transmit waveform design.First, this paper introduces the technical basis of the study of the spectrum sharingand the related transmit waveform design. This paper presents the several kinds ofspectrum sharing strategies. Based on the spectrally modulated spectrally encodedframework, this paper presents the strategy that combining both overlay and underlayspectrum sharing strategies. This paper introduces the power allocation algorithm,especially water-filling algorithm, the key idea is to allocate more power to the sub-carrier channel whose gain is higher. In case of low signal-to-noise ratio, using a water-filling algorithm can greatly increase the channel capacity. This paper introduces theidea of proactive spectrum sharing, and states the HMM （hidden markov model）-related technical background to predict the channel state though the HMM.Secondly, Secondly, For orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems, in which overlay and underlay spectrum sharingmodes were both applied, a subcarrier power allocation scheme maximizing thetransmission capacity of CR systems was proposed. In the proposed scheme, the powerallocation was modelled as a convex optimization problem by taking both the totalpower budget of CR system and the interference constraint introduced to the primaryuser into account. Compared with the pure overlay and underlay schemes, bothanalytical and numerical results all showed that the OFDM based hybrid spectrumsharing CR system with the proposed power allocation could achieve capacityimprovement.Finally, according to the literature, this paper transforms a variety of wirelessbusiness models into the ON-OFF model. And in consideration of the response delaycaused by the hardware platform, this paper predicts using the channel state by theHMM to reduce the collision of the secondary users and the primary users. Thenumerical results shows that compared with the traditional energy detection, thecollision probability of the proactive spectrum detection based on HMM are less. Base on the proactive spectrum sharing, given consideration to maximize throughput and thefairness principles, this paper optimize the transmit waveform design and allocate thechannel state for the secondary users. The numerical results shows that compared withthe traditional energy detection, the sum capability of the primary users and thesecondary users based on the proactive spectrum allocation is promoted and thefairness of the secondary users is guaranteed.