Research On Spectrum Access And Resource Allocation Based On D2D Communication

With the development of wireless communication,how to access more users under the condition of without changing the original network architecture and limited spectrum resources has become the primary consideration for operators.Heterogen-eous networks(Het Nets)is good at increasing system capacity,reducing exposure area,reducing path loss and delay,and improving quality of service,making it the primary topology for next-generation wireless communication networks.Device-to-device(D2D)communication is often used as a load balancing mechanism in Het Nets to provide services for more users.However,D2D communication also brings new interference,how to minimize interference while obtaining optimal network performance becomes a challenge.This thesis focuses on the D2D load balancing dynamic spectrum access,power optimization,and channel resource allocation problems in Het Nets.Firstly,according to the different number of users who initiate communication requests in the cell,this thesis proposes three dynamic spectrum access schemes:MU-DU-inter,MU-DU-under andMU-D_h _l-iu.The micro base station divides D2D users into high-priority D2D users and low-priority D2D users.D2D users identify channel state information and use different spectrum access methods to access the network automatically.In addition,this thesis uses the Continuous-Time Markov Chain(CTMC)to represent the change of user communication state.Through simulation verification,the proposed scheme can effectively improve the spectrum utilization rate,increase the number of accessible users,and reduce the data transmission time while ensuring the network throughput.Secondly,this thesis proposes a power allocation algorithm based on imperfect channel state information,and it is named Incomplete Channel State Information Power Allocation(I-CSIPA)algorithm.The power allocation problem between D2D users and cellular users is transformed into an optimization problem with the goal of maximizing the Signal to Interference plus Noise Ratio(SINR)of D2D links and cellular links,and the optimization problem is solved by Lagrange dual function and gradient descent method.It is verified by simulation that the proposed algorithm in this paper can effectively improve the throughput of the network without increasing the total interference.