Inte-cell Interference Coordination In Ultra-dense Networks Based On Poisson Point Process

As one of key technologies used in the fifth generation mobile networks(5G),the ultra-dense networks(UDN)reduces the coverage radius to increase the spatial reuse efficiency of spectrum resources by deploying a large number of small base stations(SBSs)with low transmit power in a given area.The interference increases with the increase of the density of SBSs and becomes more complicate.Most of users associate with macro base stations(MBSs)because the transmit power of MBSs is greater than the transmit power of SBSs in the heterogeneous ultra-dense networks(HetUDN)where dense-deployment SBSs are overlapping in the coverage of the MBSs.This leads the MBSs are overload.The load is tradeoff between SBS-tier and MBS-tier by unloading the edge-users from the MBS-Cell to the SBS-Cell,but the received signal to interference plus noise ratio(SINR)of the users unloaded from MBS-tier is very low due to the serious interference from the MBSs.In 5G,the focus of inter-cell interference coordination(ICIC)has being shifting from the cross-tier to the intra-tier with the increasing of the spatial distribution density of the SBSs.To coordinate the inter-cell interference,especially the inter-cell interference in a one-tier networks and balance the users in the networks,approaches are proposed in this dissertation as follows:First of all,the downlinks of the UDN and the HetUDN are modelled according to some spatial Poison point process(PPP)in this dissertation.We analyse and derive the distribution of the distances from users to base stations(BSs),then calculate the mean of received signal strength,the mean of the signal to interference ratio(SIR)from different BSs to users,and the spectral efficiency(SE)of UDN and HetUDN.The modelling and analysis for inter-cell interference(ICI)in UDN and HetUDN can provide mathematical basis for inter-cell interference coordination and management.Secondly,a large number of edge-users are offloaded from the MBS-tier to the SBStier,which leads to the coverage range of MBSs reducing.The ICI between SBS-tier and MBS-tier can be mitigated by reducing the transmit power of MBS,and the interference can be coordinated between the edge-uses and inner-users in the same tier by fractional power control(FPC).For this purpose,three FPC strategies are proposed and modelled based on PPP,then the b-th moment of the success probability of users accessing to the networks is derived.Utilizing the Meta distribution of SIR,the coverage probability(the first moment of the success probability)and its variance,the fraction of users in the whole network can achieve successful transmission average with a given SIR threshold,and the mean local delay are got.Moreover,the three FPC strategies are evaluated by the area spetral efficiency(ASE)and energy efficiency(EE).Especially,in the third FPC case,the two-tiers HetUDN is changed into an one-tier UDN by special parameters setting.The numerical and Monte-Carlo simulation results show that the network performance can be greatly improved at a little cost in the case of the third FPC strategy.Finally,we proposed a distributed joint allocation of spectrum resources with power control between a user's closest BS(the tagged BS)and its second closed BS(the major interfering BS)according to the characteristic that the interference mainly comes from the second closed BS for any users in a Vonoroi cell(VC).The interference between edgeusers and inner-users is coordinated and the success probability of edge-users is increased by reduce the interfering from the second closed BSs of the edge-users in the VC in this case.The frame is modelled by PPP and the b-th moment of the success probability of users accessing to the networks is derived.Utilizing the Meta distribution of SIR,we can get the coverage probability and its variance,the fraction of users in the whole network can achieve successful transmission average with a given SIR threshold,and the mean local delay.Moreover,the strategy is evaluated by the ASE and EE.In this dissertation,the wireless UDN is modelled based on PPP,and three FPC strategies and a joint allocation of spectrum resources with power control are proposed to coordinate and manage the ICI for different tiers and the same tier,then balance the performance between the edge-users and inner-users.Utilizing the Meta distribution of SIR,these strategies are evaluated by the following network metrics: the coverage probability and its variance,the fraction of users in the whole network can achieve successful transmission average with a given SIR threshold,the ASE,and the EE.Numerical and Monte-Carlo simulation results show that the performance of edge-users can be greatly increased with a little effect on the performance of inner-users.Especially,the networks EE is significantly increased due to the power control strategies.