Research On Several Key Technologies For 5G Mobile Communication

With the increasing number of mobile users and the appearance of new wireless medium services in recent years,the fifth generation(5G)mobile communication,which can improve the spectrum efficiency and data rate,has become the hot research topic.Time division duplex(TDD)and frequency division duplex(FDD)are the traditional half-duplex mode.TDD can transmit and receive the signal in different time slot at the same frequency.FDD can transmit and receive the signal in different frequency at the same time slot.Full-duplex(FD)communication,which allows co-time co-frequency transmission and reception,can improve the spectrum efficiency and thus has been the key technology of 5G mobile communication.Traditional orthogonal multiple access(OMA)can allocate the independent time-domain,frequency-domain and code-domain resources to the mobile user.The transmission resources of different mobile users are orthogonal to each other.As the key technology of 5G communication,non-orthogonal multiple access(NOMA)allows different mobile users to use the same time-domain and frequency-domain resources.The information of different users can be transmitted together.The transmission resources of different mobile users are non-orthogonal.NOMA can improve the spectrum efficiency and increase the number of access users.At the same time,5G networks should support the huge number of access users,which can not be satisfied in traditional networks.The dense deployment of Femtocell can increase the spectrum efficiency of 5G networks,improve the service quality of mobile users,and decrease the base station load.We will utilize the FD communication,NOMA and Femtocell technologies to improve the capacity and spectrum efficiency of 5G mobile communication system.The contribution of this dissertation can be summarized as follows:1.We propose the two-stage contention full-duplex medium access control(TF-MAC)protocol for wireless FD networks,which consists of request to send(RTS)/full-duplex clear to send(FCTS)/clear to send(CTS)based handshaking mechanism and FD back-off algorithm.RTS/FCTS/CTS based handshaking mechanism can replace the long data frame collision with the short control frame collision and solve the hidden node problem in FD communication.It can support two-node wireless FD bidirectional link,three-node wireless FD asymmetric link and traditional half-duplex link.Based on the handshaking mechanism,we propose the FD back-off algorithm,which can decrease the collision probability and increase the establishment probability of FD link.By using the cascaded two-dimensional Markov chain,we analyze the proposed TF-MAC protocol and derive the closed-form expression for the normalized throughput of wireless FD networks.The simulation results validate the effectiveness of the proposed TF-MAC protocol,and demonstrate that TF-MAC protocol can improve the performance of wireless FD networks.2.To investigate the performance of cooperative NOMA system,we first analyze the spectrum efficiency of cooperative NOMA system.Then,the energy efficiency function of cooperative NOMA system is formulated.To reduce the complexity and channel state information(CSI)exchange of cooperative NOMA system,the user pairing scheme is proposed.Finally,simulation results validate the superiority of cooperative NOMA system and the effectiveness of user pairing scheme.Furthermore,for the cooperative NOMA system,the spectrum efficiency decreases as the user number increases.The energy efficiency first increases and then decreases as the transmit power increases.The larger the constant circuit power is,the larger optimal transmit power corresponding to the maximum energy efficiency is.3.In orthogonal frequency division multiple access(OFDMA)based Femtocell network,to improve the spectrum efficiency and avoid the interference from the Femtocell user equipments(FUE)to Macrocell user equipments(MUE)and other FUE,we propose the two-level game based joint power control and subcarrier selection distributed algorithm,which is based on non-cooperative game and evolutionary game.The proposed distributed algorithm consists of two kinds of game theories.The power control and subcarrier selection of FUE can be achieved by non-cooperative game and evolutionary game,respectively.By alternating iterations of power control and subcarrier selection,the system can converge to the Nash equilibrium(NE).Simulation results validate the effectiveness of the proposed two-level game distributed algorithm.The algorithm can optimize the FUE transmit power and make the subcarrier utilized in equilibrium.4.In multi-source multi-relay cooperative network,to avoid the interference among the relays assisted the same source and maximize the relay utility,we propose the joint power control and source selection distributed algorithm,which is based on the two-level game.By using the alternate iterations between the non-cooperative game of power control and the evolutionary game of source selection,the proposed distributed algorithm can optimize the relay transmit power,suppress the interference effectively,and choose the optimal source.Furthermore,we prove that the two-level game model has the unique NE.Simulation results show that the system can achieve efficient resource allocation by adopting the proposed distributed algorithm.