Spectral Allocation Algorithm Based On Fuzzy Logic And Communication Priority

Spectrum as a precious resource is needed for wireless communications. When taking the traditional way of radio spectrum management, the spectrum utilization is low. Cognitive radio technology is considered to be an effective way to solve this problem. Dynamic spectrum allocation is a key technology of cognitive radio, it can make dynamic management of idle spectrum in spectrum resource, and provides an effective way for using the spectrum resource efficient.We take centralized spectrum allocation model and in the condition that the number of idle spectrum bands is less than the number of cognitive users. Two novel algorithms of spectrum allocation based on fuzzy logic are presented in this paper.Signal coverage area of the cognitive radio base-station (CR-BS) is transformed into each cognitive user’s traffic priority to be divided in the first algorithm. Taking into account the cognitive user’s spectrum utilization efficiency, velocity and the distance between the primary user’s receiver and cognitive user’s transmitter, we design a3input fuzzy logic system (FLS) to conduct fuzzy logic operation for spectrum access probability of each cognitive user. The CR-BS revenue is defined as the product of each cognitive user spectrum traffic priority and spectrum access probability. The goal of the spectrum allocation algorithm is to maximize the CR-BS revenue. The results achieved of the algorithm can maximize the CR-BS revenue. The calculation complexity of our algorithm is low. Simulation confirmed the feasibility of this algorithm.In addition, when the primary user system using spectrum leasing strategy for the cognitive user system, in order to gain high revenue and ensure the primary user’s QoS, the second algorithm will use the sealed lirsl-price auction and fuzzy logic to allocate spectrum bands.In the second algorithm, the cognitive user’s spectrum allocation function indicates that the cognitive user can obtain the spectrum band or not. The value of I indicates that the cognitive user can obtain the spectrum band，otherwise not available.The minimum lease revenue of the idle spectrum band is determined by the primaryuser’s base-station (PU-BS). By using the valuation function which is founded by theminimum lease revenue of the idle spectrum band, cognitive user’s transmit powerand packet arrival rate, then cognitive user can obtain the expected revenue of thespectrum band. Then cognitive user submits his communication cost to the CR-BS.Taking into account the cognitive user’s transmit power and the distance between thepirmary user’s receiver and cognitive user’s transmitter, we design a2-input FLS toconduct fuzzy logic operation for the interference factor of each cognitive user. Thenthe difference of cognitive user’s communication cost minus his interference factor isobtained as trafifc priority. The product of spectrum allocation iunction and trafficprioirty of each cognitive user is obtained, then the sum of the products above can bedeifned as the PU-BS revenue. The goal of spectrum allocation algorithm is tomaximize the PU-BS revenue and ensure the primary user’s QoS and revenue. Whenthe communication cost is high and the interference factor is small，then the PU-BSrevenue is high，and the revenue and QoS of the primary user is high too.Based on the sealed first-price auction theory, using FLS to model theinterference between primary user and cognitive user is the innovation of the secondalgorithm. The number of the FLS input conditions can be increased as the number ofthe considered physical factors be increased. This model has good scalability but thedisadvantage is that the fuzzy rules can’t be obtained easily. Simulation confirmed thefeasibility of this method and the desired performance is achieved.