Research On Interference Elimination Under Ultra-dense Heterogeneous Networks

Ultra-dense heterogeneous networks,as one of the key features of the future 5G network,mainly meet the needs of the continuously increasing communication demand by densely deploying small cells.The increasing deployment of small cells has also led to the development of traditional cellular networks towards heterogeneous,randomized,and complicated network architectures.Therefore,the new network architecture also brings a series of new challenges.First of all,the system-level simulation based on the traditional network lattice cannot capture the characteristics of the network well and cannot obtain accurate analysis results.At same time,inter-cell interference in heterogeneous cellular networks is exacerbated by the more intensive deployment of base stations and the adoption of same frequency networking in order to maximize the utilization of spectrum.In this paper,we give the modeling analysis of ultra-dense heterogeneous cellular networks by Poisson point process and Poisson cluster point process and derive the user's outage probability.Based on this indicator,we compared and analyzed the accuracy of modeling base stations distribution at different point process.The simulation results show that the use of completely randomized homogeneous Poisson point process can not reflect the correlation between base stations.However,the use of Poisson cluster process can reflect the distribution of base stations in the hot spot area,and well complements the completely random coverage hole,which makes users have a lower outage probability.Secondly,in order to solve the problem of the cross-layer interference between the small cells and macro cells in the ultra-dense heterogeneous cellular network due to the small cell range extension technology used by the small cell.In this paper,two-layers of ultra-dense heterogeneous cellular network as an example for time-domain interference coordination technology analysis.The indexes such as user outage probability,user spectrum efficiency and average ergodic capacity of cellular network under the base station distribution model subject to Poisson point process are derived.Considering that almost blank sub-frame ratio setting is too complicated in adopting the time-domain interference coordination technique.An improved algorithm for allocating dynamic almost blank sub-frames the best cell offset value is proposed.The simulation results show that the proposed algorithm can improve the average ergodic capacity of the entire network compared with the static almost blank sub-frame allocation scheme using the blank sub-frame ratio according to the experience set as the fixed value.Finally,the base station modeling based on the homogeneous Poisson point process is used to study the inter-cell interference technology of multi-cell cooperation.Aiming at the problems of base station grouping and cooperative user selection during joint transmission of users in multi-cell cooperation and the low spectrum efficiency of edge users when using time-domain interference coordination,a time-domain interference coordination scheme based on multi-cell cooperation is proposed.This scheme not only improves the low signal-to-interference ratio of users in coverage enhancement area by jointly transmitting,but also reduces the backhaul signal overhead.Experimental results show that using the multi-cell cooperation scheme based on bias value reduces the outage probability compared with non-inter-cell interference coordination technique.At the same time,the spectrum efficiency of users located in the coverage enhancement area is improved and the overall network average ergodic capacity is increased.