| Spectrum access is the core part of wireless cognitive network research, the mainidea of which is that the cognitive users share the spectrum of the lisenced users toimprove the spectrum utilization ratio, satisfy the rapid-developing spectrum demandand ease the contradiction of spectrum-scarcity and lower-utilization of the lisencedspectrum.In this paper we focus on the problem of efficient spectrum access and carryout research with the targets of transmission availability, channel successfultransmission ratio, degree of spectrum share and demand matching ratio respectively.The main contributions include:Considering the features of wireless cognitive networks, such as small-scale traffic,limited storage and computing ability and rapid-changing spectrum availability, thispaper analyzes the problem of useful information query for wireless cognitive networks.We propose the Maximum Point-Different Region Query algorithm (MP-DRQ) whichcan query the dynamic data quickly. It achieves the research target of improvingtransmission availability and spectrum utilization. The concept of current maximumpoint is proposed。The channel space is divided into dominate region, dominated regionand free region according to current maximum point(s). It fits for the dynamic dataquery problem. Simulation results show that the query time with MP-DRQ can bereduced comparing with those of BNL and D&C.Considering the spectrum allocation problem without any prior knowledge, wepropose the Pheromone based Spectrum Allocation algorithm (PSA), which is based onthe analysis about the effect of history information on spectrum allocation. It achievesthe research targets of improving successful transmission ratio and optimizing spectrumusage. PSA gets inspiration from the concept of pheromone in the ant colonyoptimization theory. The timely broadcast information with successful transmissionratio can be regarded as pheromone during the spectrum allocation procedure. Adjustthe spectrum allocation strategy with the update of pheromone. This process will notstop until the algorithm converges to a spectrum allocation strategy which can satisfythe demand. The simulations show that PSA has the obvious performance advantage ofimproving the successful transmission ratio, comparing with random spectrumallocation, fixed spectrum allocation and greedy spectrum allocation.Considering how to make more users to share the spectrum in the relay-tradingmode, we analyze the spectrum sharing problem in the relay-trading mode. Based on itwe propose the spectrum sharing strategy for relay trading. The target of this algorithmis to maximize the degree of spectrum share and the method is to set the power whichsatisfies the minimum transmission rate. We construct a cooperative sharing group anddefine the contribution metric to measure the relay contribution and sharing qualification of each group. We find the power bounds which can satisfy the minimumtransmission rate. Learning from the water filling algorithm, we set and adjust thepower for many cycles, which can make more users satisfied. Simulation results showthat the relay trading mode with SSS-RT can improve the degree of spectrum sharingobviously.Considering the spectrum trading problem with multi-service-attribute, we proposethe Heterogeneous Service Oriented Spectrum Trading (HSO-ST) algorithm based onthe analysis of effect of multi-service-attribute on spectrum trading, the target of whichis to maximize the matching ratio of secondary users with the priority restriction. Firstlywe give a detailed definition of spectrum service character and construct the servicespace according to spectrum supply set. Based on the relationships of spectrum demand,spectrum supply and service space, we build the bipartite matching graph according toattribute matching degree, and obtain the maximum bipartite matching with HSO-ST.Simulation results show that the matching ratio with HSO-ST can be improved by atleast10%comparing with other spectrum trading strategies. |
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