Research On User Association And Traffic Offloading In 5G Heterogeneous Network

The huge demand for mobile data services is driving the emergence and growth of the Fifth Generation Mobile Communication Technology(5G).5G key candidate technologies such as heterogeneous ultra-dense networks,large-scale antennas and full-spectrum access have been proposed to cope with the growth of 1000 times of wireless data services in the next ten years.No matter which technology is adopted,a user association mechanism is needed before formal data transmission to determine a serving base station.Reasonable user association plays an important role in offloading traffic,enhancing load balancing and spectrum efficiency.Therefore,based on the above 5G candidate technologies,this paper studies the user association and traffic offloading technologies.The main contents are summarized as follows:In view of the fact that the users are not evenly distributed,the inter-layer correlation between macro base station and small base station in 5G heterogeneous network and the correlation between base station and user distribution are studied.A new network modeling method fully considering 5G heterogeneous network spatial correlation is proposed.First,the first part of this paper models the network deployment and channel,and theoretically analyzes the performance metrics of association probability,average cell load and average ergodic rate under the user association criterion of maximum average received power.The simulation results show that the proposed network modeling method can show good performance in flexible traffic offloading.Mobile users in 5G heterogeneous networks will have frequent handovers.In the second part of this paper,the correlation of the associated distances between user and serving base station in multiple time slots is researched.A new analysis method that fully considers 5G heterogeneous networks time correlation is proposed,which is different from the traditional "typical user method".First,based on the stochastic geometry theory,the network deployment,transmission channel and user movement process are modeled respectively,then the multi-slot coverage probability and the SINR-based horizontal handover rate and vertical handover rate are deduced.The simulation results show that the maximum average received power(MARP)association strategy can improve the multi-slot coverage probability,and MARP is also more robust to the changes of BS density and MU speed than the nearest neighbor(ND)association strategy.In order to cope with the huge amount of data,the capacity increase of 5G heterogeneous networks can be further realized through the combination of millimeter-wave technology and large-scale antenna technology.The third part of this paper is from this perspective,to study the user association to the channel in the high-frequency unlicensed band,thus completing the traffic offloading on the licensed band.The article specifically chooses the 60GHz unlicensed band as the research band.Combined with the large-scale antenna beamforming technology,a channel access method based on location information and geometric relationship of user,base station and coexistence access point is proposed.A detailed signaling flow chart also be given in the end.In summary,this paper carrys out the research on user association and traffic offloading in 5G heterogeneous networks from the aspects of spatial correlation,time correlation and frequency spectrum expanding.The research results obtained in the above can provide reference for 5G network design.