Research On Cognitive OFDM Network Resource Allocation Technology

With the rapid development of wireless communication,the increasing demand on spectrum makes spectrum resource scarce.At the same time,there are many available spectrum holes in the traditional static spectrum allocation.In order to improve spectrum efficiency,cognitive radio technology can detect and take advantage of the vacant spectrum resource from the space domain,time domain,and frequency domain.Meanwhile,orthogonal frequency division multiplexing(OFDM)is a special multi-carrier transmission scheme,which decomposes high-speed data stream into several parallel data streams against inter-symbol interference and frequency selectivity fading channel.Combined with the cognitive radio,cognitive OFDM network can improve the spectrum efficiency significantly.In this thesis,resource allocation algorithms for cognitive OFDM network are studied.Our thesis mainly focuses on the resource allocation problems for underlay-based multicast cognitive OFDM network,overlay-based unicast cognitive OFDM network and overlay-based multicast cognitive OFDM network.The contributions are as follows:For underlay-based multicast downlink cognitive OFDM network,the required minimum transmission rate at each secondary user,the primary user interference requirement,and the total power at cognitive base station(BS)are considered in the formulation of resource allocation problem,and we propose a resource allocation algorithm via Zoutendijk's feasible direction method to maximize the energy efficiency.The simulation results show that the proposed algorithm can effectively improve the energy efficiency and spectrum efficiency for multicast cognitive OFDM network.For overlay-based unicast uplink cognitive OFDM network,the minimum transmission rate requirement at each secondary user and the bit error rate(BER)requirement are considered in the formulation of resource allocation problem,and we propose a resource allocation algorithm based on penalty function method to minimize the total transmission power.The simulation results show that the proposed algorithm can reduce the total power consumption significantly.For overlay-based multicast downlink cognitive OFDM network,the maximum available power at the cognitive BS and BER are considered in the formulation of resource allocation problem,and we propose a resource allocation algorithm with the Harmony search algorithm to maximize the minimum transmission rate of each multicast group.The simulation results show that the proposed algorithm can improve the throughput of cognitive OFDM network.