| Since the mobile communication appeared forty years ago,it has been an indispensable part of people's life.In the 5G era,the explosive growth of mobile data traffic,massive access equipment,and all kinds of new business and application scenarios,expands the scope of mobile communications services.But at the same time it also brings new challenges to mobile communication.One of these challenges is the inter-cell interference problem.In a LTE-A or a 5G heterogeneous network,the problem has become more serious because of the ultra dense deployment of pico eNodeBs and the application of flexible duplex technology such as dynamic TDD.The massive access of the pico eNodeBs has greatly improved the total throughput of the network and the cell-edge user performance,but also brings more inter-cell interference in the areas where these picocells overlap with other picocells.In addition,because LTE-A and 5G systems apply flexible dynamic uplink and downlink subframe configurations,different picocells may be in different transmission states simultaneously,which also brings new uplink and downlink cross interference.In order to solve the interference problems and improve system performance and user experience,it is necessary to consider more effective interference coordination schemes for LTE-A and 5G heterogeneous networks.At first,this paper analyzes three kinds of interference problems in the downlink of the two-tier heterogeneous network,namely cross-layer inter-cell interference,co-layer inter-cell interference and inter-user interference.In order to solve these interference problems,the current research status of several interference coordination schemes for heterogeneous networks is analyzed.This paper discusses almost blank subframe scheme in the time domain,the frequency reuse and subcarrier allocation schemes in frequency domain,the CoMP,beam-forming and spatial blanking schemes in space domain,and power control interference coordination scheme,and then analyzes the main application scenarios,advantages,and problems of these schemes.Interference coordination schemes,which operate independently in single domain such as time domain,frequency domain,space domain and power control,can only reduce interference under the specific conditions.Because of the more complex network topology and the more complicated communication environment in LTE-A and 5G networks with the deployment of massive MIMO,the ultra dense networks and the application of dynamic TDD,the system performance will decreases inevitably without efficient interference coordination schemes.Therefore,a joint interference coordination scheme in time domain and space domain is proposed in this paper which is for the two-tier heterogeneous network.This scheme proposes a reasonable mechanism to execute the reduced-power ABS,CoMP,and cell-cluster interference mitigation schemes jointly,and can suppress the interferences efficiently in the network.Secondly,a simulation system for the heterogeneous network is designed in the paper.The performance of the proposed scheme is simulated and compared with other traditional schemes,which show that the significantly improvement of the proposed scheme in the system performance.Finally,an adaptive multi-domain joint interference coordination scheme for 5G heterogeneous networks is proposed in this paper.The scheme is aimed at practical engineering applications,and can adaptively select the optimal interference coordination schemes from the candidate schemes according to the dynamic change of the wireless network environment.The proposed scheme can reduce the cross-layer inter-cell interference,the co-layer inter-cell interference and inter-user interference simultaneously in the network and improve the system performance.The simulation result shows the performance of the proposed scheme compared with other schemes and proves that the proposed scheme achieves the outstanding gain in the cell spectrum efficiency and the user signal to interference noise ratio in the network. |
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