Performance Research On In-cabin Ultra-Dense Networks Based On Coordinated Multiple-Point Joint Transmission

Numerous indoor hotspots have been formed with the widespread popularity of various smart terminals and the in-depth development of mobile service applications.Indoor hotspots are the places where the amount of indoor communication data in per unit area has increased significantly.In the field of aeronautical mobile communications,the demand for broadband data services by aircraft passengers is increasing,making the cabin an indoor hotspot.5G ultra-dense networks(UDN)technology reduces the signal transmission distance and performs high-density frequency space multiplexing by densely deploying low-power and high-integration small base stations,which can greatly improve spectrum efficiency and increase system capacity.UDN is the key technology to solve indoor hotspot coverage,and also provides a new solution for wireless coverage in the cabin.Although the dense deployment of small base stations can bring potential spectrum multiplexing gain and network capacity gain,the high-density overlapping coverage of small cells will cause serious inter-cell interference.The serious inter-cell interference makes UDN have a base station density limit,which restricts the further improvement of network performance.Therefore,the coordinated multiple-point joint transmission(CoMP-JT)technology is applied to the UDN.Through sharing channel information and user data information from multiple base stations which are servicing the same users at the same time,CoMP-JT turns the inter cell interference signal into useful signal so as to reduce interference between adjacent cells and continue the performance gain brought by densening the base stations.At the same time,to further consider the randomness of the base station distribution and the propagation characteristics of the signal in the near-field region,the stochastic geometric theory and a bounded double-slope path loss model are adopted in the network modeling and interference analysis of UDN.Based on this,from the general to the special,the thesis studies the UDN performance respectively in indoor hotspots and aircraft cabins as follows:(1)The relationship between system parameters such as the number of cooperative base stations,base station density and network performance under CoMP-JT is studied for the UDN deployment of indoor hotspots.Firstly,the randomness of the base station distribution is modeled by the three-dimensional homogeneous poisson point process(HPPP),and the probability density function of the distance between the base station and the user is derived,which provides the basis for the cooperation mechanism selecting multiple base stations closest to the user to joint transmission.Then the bounded dual-slope path loss model is used to model the interference of the user,and the expression of user downlink coverage and area spectrum efficiency(ASE)are further derived.Finally,combined with the numerical simulation results,the effects of parameters such as the number of cooperative base stations and base station density on the network performance are analyzed comprehensively,the base station density limit that maximizes ASE is obtained,and the factors affecting the density limit of the base station are discussed.The work above provides a theoretical reference for the UDN deployment of indoor hotspots.(2)The trade-off relationship between ASE and energy efficiency(EE)under CoMP-JT is studied based on the green communication concept for the UDN deployment in the aircraft cabin.Firstly,the small base station and the user are distributed in different two-dimensional planes,and the HPPP is used to model the base station distribution.Using the similar interference modeling in(1)and considering the backhaul energy consumption of CoMP-JT,the expressions of user's downlink coverage,ASE and EE are derived.Then combined with the numerical simulation results,the influence of parameters such as the number of cooperative base stations and base station density on the network performance is analyzed,and the base station density limit that maximizes ASE and EE is obtained respectively.Finally,in the feasible range of the base station density under the interruption rate limit,the trade-off relationship between ASE and EE is discussed in three cases.The marginal conversion rate of ASE and EE is obtained when there is a compromise between ASE and EE,and the marginal replacement rate of ASE and EE is comprehensively considered by introducing the Cobb-Douglas utility function with preference factor.When the marginal conversion rate and the marginal replacement rate are equal,the optimal base station density is determined to achieve Pareto optimality while guaranteeing the quality of service.