Secrecy Transmission-Oriented Resource Management Algorithms For Heterogeneously Integrated Networks

In recent years,various types of wireless access technologies have experienced rapid development,however,single wireless access technology cannot fully meet the service requirements of users due to the diversity of heterogeneous wireless access technologies and user requirements,hence it is heavily necessary for various types of wireless network technologies to gradually achieve effective coordination and integration,which resulting in heterogeneous networks.In this thesis,the radio resource management algorithms of heterogeneous network are studied,and the main contents are as follows:Firstly,the architectures and characteristics of heterogeneous network are reviewed briefly.On this basis,the key technologies of heterogeneous networks are described in detail which mainly include user association,vertical handover and radio resource management technologies.We consider the problem of user association and power allocation in the downlink transmission scenario of a heterogeneous network where exists eavesdroppers,and put forward an optimal joint user association and power allocation algorithm for secrecy information transmission.We consider the optimization constraints of data rate,maximum power,association variable,formulate the joint user association and power allocation problem of the heterogeneous network as a sum secrecy energy efficiency maximization problem,and then solve the problem for both single-user case and multi-user case respectively.In the case of single user,the maximum of secrecy energy efficiency is achieved by optimizing the transmission power of all base stations and selecting the corresponding energy efficiency of optimal base station to obtain the optimal joint user association and power allocation strategies.As for multi-user case,the optimization problem is a mixed-integer nonlinear optimization problem which is difficult to solve conveniently.Indeed,it can be shown that the original optimization problem can be equivalently transformed into two subproblems,i.e.,power allocation subproblem and user association subproblem.By applying iterative method and lagrange method algorithm to solve the power allocation subproblem,and using the Kuhn-Munkres algorithm to solve the user association subproblem,the optimal user association and power allocation strategy corresponding to the maximum secrecy energy efficiency can be obtained.We also consider a non-orthogonal spectrum access in the downlink transmission scenario of a heterogeneous network,and propose an optimal joint user association and power allocation algorithm based on energy efficiency maximization.We consider the downlink transmission of heterogeneous network,which consists of multiple overlapping access networks,and assuming that orthogonal frequency access schemes are applied to different networks,and non-orthogonal multiple access schemes are applied within each network,meanwhile,each eavesdropper may eavesdrop the information of the users.Based on the optimization constraints of data rate,maximum power and association variables,the joint power allocation and user association problem is formulated as an optimization problem which aims at achieving the maximum secrecy energy efficiency of the networks.As the formulalted optimization problem is a NP hard problem,which cannot be solved directly,we propose a heuristic algorithm,which starts from a complete matching between user pairs and base stations,and then for each pair of matching,the original power allocation and user association problem can be transformed into power allocation subproblem and user association subproblem equivalently.In particular,the power allocation subproblem is defined as for given user and base station association pair,maximizing the secrecy energy efficiency in terms of the transmit power of the base station,while user association subproblem is defined as selecting the optimal base stations for all the user pairs so that the sum secrecy energy efficiency of all the base stations can be maximized.Based on the given local optimal power allocation strategy,the Kuhn-Munkres algorithm can be used to solve the user association subproblem and to obtain the local optimal user association strategy.Finally,we compare the local optimal secrecy energy efficiency obtained for all user and base station pairs and choose the power allocation and user association strategy corresponding to the maximum network secrecy energy efficiency as the global optimal strategy.