Research On Coexistence Mechanism And Resource Allocation Scheme For Dual-band Cognitive Small Cell Networks

The future 5G mobile communication network requires high transmission data rate and low transmission latency.The explosive increasing of mobile intelligent terminal equipments results in the exponential growth of the data flow in the mobile communication network.Meanwhile,the licensed spectrum has almost been occupied,in order to meet the challenges of high mobile data traffic and alleviate the shortage of the licensed spectrum resource,the unlicensed spectrum is considered as a potential expansion of mobile communication network.A reasonable resource allocation method which could improve the spectrum utilization is also an effective way to solve the problem of the current mobile communication network.In this paper,we firstly study the dual-band coexistence mechanism and resource allocation problem between cognitive small cell networks,macro cellular networks and WiFi networks.Secondly,we focus on the problem of the coexistence mechanism and dual-band resource allocation among multi operator base stations in the unlicensed band.Firstly,we study the satisfaction-based dual-band resource allocation scheme in cognitive small cell networks,which could share the licensed band with macrocell based on the sensing result and simultaneously use licensed and unlicensed bands by carrier aggregation technologies.In the licensed band,we jointly optimize the cognitive cell association,spectrum sensing and power allocation under related interference constraints,to maximize the capacity of the whole cognitive small cell network.In the unlicensed band,considering the dynamic traffic load and the transmission probability of the WiFi network,a channel access scheme based on enhanced LBT mechanism is proposed to improve the utilization of the unlicensed band while guaranteeing the QoS of WiFi users.The traffic load of WiFi network is analyzed by a statistical method,and the optimal transmission time of the cognitive small cell in the unlicensed band could be calculated.Finally,we propose a satisfaction-based dual-band resource allocation(SDRA)algorithm,which combine with the cellular selection,spectrum sensing,power allocation and transmission time in unlicensed band to maximize the overall satisfaction of the cognitive small cell network and the WiFi network.Secondly,we focus on a multi-operator LTE-U cognitive small cell network(which is based on the LTE-U technology,licensed and unlicensed bands could be used with carrier aggregation technologies,hereinafter referred to as LTE-U).To deal with the coexistence problem in unlicensed band,in this paper,we propose a LBT based LTE-U base station bidding access mechanism in unlicensed band.Considering the time variation of channels,the transmission performance of full duplex(FD)mode is not always better than half duplex(HD)mode.Therefore,we propose a resource allocation scheme with FD/HD hybrid transmission mode based on bidding mechanism for multiple operators in unlicensed bands.The Lyapunov optimization method is used to jointly optimize the dual band resource scheduling problem,system packet drop rate and delay,guarantee the stability of the data queue,maximize the spectrum utilization rate of licensed and unlicensed bands,and improve the overall efficiency of the whole network.