Research On Uplink Performance Improvement In Heterogeneous Networks

In recent years,the explosive growth and uneven distribution of mobile intelligent terminals have promoted the emergence of heterogeneous networks.It can improve the system capacity and alleviate interference problems caused by the explosive growth of mobile data services in hot areas.However,with the rapid development of Internet technology,the uplink traffic is increasing gradually,which leads to new challenges.On the one hand,the traditional uplink-downlink coupled user association mode is inappropriate;on the other hand,the inter-cell interference of the uplink will affect the transmission quality of the uplink.Therefore,this paper mainly studies the performance improvement of the uplink.Aiming at the problem of user association,this paper first reviews the coupled uplink-downlink user association schemes,and points out the advantages and disadvantages among various methods.Due to the different transmission power of different base stations in heterogeneous networks,the application of uplink-downlink coupled user association mode will lead to poor quality of service in the uplink.Therefore,this paper considers the decoupled uplink-downlink user association mode that can effectively improve the transmission performance of the uplink by associating the uplink with the nearest base station.Aiming at the problem of the inter-cell interference in the uplink,this paper proposes a new power control and frequency allocation scheme under the decoupled uplink-downlink user association mode.The main purpose of power control is to mitigate the interference of the same frequency.This paper extends the well-known power control schemes(i.e.distributed power control,distributed power control with active link protection)in conventional cellular networks to heterogeneous networks,and propose the dynamic distributed power control algorithm.This algorithm guarantees that active users continue to have acceptable received SINR and reduces energy consumption.In addition,a modified reverse frequency allocation scheme is proposed in this paper,which combines the co-channel interference problem of the uplink in the hotspot area.Its main purpose is to increase the distance between the same frequency users and allocate different spectrum resources for densely distributed users.Therefore,it is modeled the optimization problem based on the maximum sum rate of uplinks.This frequency allocation scheme can not only alleviate the co-channel interference of the uplink,but also improve the spectrum utilization.