Research On Key Wireless Technologies For Moving Networks

With the population of smart mobile devices and the increasing on-the-road time,the traffic demand from vehicular user equipments/devices(VUEs)grows exponentially.Deployed on top of vehicles,moving network nodes(MNNs)provide ubiquitous and constant services to VUEs and a significant number of moving access points for extravehicular user equipments/devices(EUEs).Thus,moving networks,integrating MNNs into generalized hetero-geneous networks,is one of the key scenarios for the 5-th generation(5G)and future mobile communication system.Based on the random and irregular spatial distribution of heterogeneous networks,the mobility of the MNN results in the nomadic network topology which greatly changes conventional fixed networ-k architecture.There are great challenges in the development procedure of the next generation mobile com-munication network:establishing a system analytical framework before the de-ployment of moving networks to quantify and analyze the basic network per-formance,applying the wireless network key technologies in the new scenario,further analyzing the spatial distribution of network performances.To solve the questions above,based on stochastic geometry and mobility model,this paper proposes a basic system analysis framework for moving networks which solves problems about quantifying and analyzing the system performance metrics of EUEs and VUEs.Based on the proposed framework above,the coordinated multipoint(CoMP)technology is introduced in moving network and the high CoMP probability and performance enhancement are analyzed when the MNNs coordinated serve the user with the macro base stations(BSs).The signal-to-interference ratio(SIR)meta distribution framework for moving networks is established to further analyze the influence from the MNNs on spatial distri-bution of system performances.This paper provides theoretical insights for practical deployment of moving networks.The detailed research contributions are as follows:(1)In the scenario of moving networks,this paper establishes a system analysis framework for moving network based on stochastic geometry and a mobility model,and analyzes the basic network performance metrics like out-age probability.By using the stochastic geometry,a heterogeneous network model is proposed by assuming the macro BSs and moving nodes follows in-dependent homogeneous Poisson point processes.The approximated distance between the EUE and its serving MNN is derived based on a mobility model.Based on the proposed system model,this paper derives the outage probability for EUEs in single-tier networks.Then,the access probability for EUEs con-necting to the MNN tier is derived for heterogeneous cellular networks.An integral expression of the outage probability for the EUEs served by MNNs is obtained.For VUEs,this paper obtains the probability of accessing MNNs and the coverage probability when VUEs are served by MNNs.Simulations verify the valid analysis and prove that the moving network can improve the perfor-mance for both EUEs and VUEs.Under general network parameters,this paper observes that the access probability of VUEs and EUEs connecting to MNNs are up to 90%and 70%,respectively.Compared with the fixed network,increasing the ratio of MNN and macro BS intensity can decrease the outage probability of EUEs,especially with high vehicle penetration losses.moving networks out-performs fixed networks in term of the coverage probability of the VUEs and can provide more stable communication service.(2)This paper proposes a CoMP scheme in moving networks.The possi-bility for macro base stations and MNNs to serve EUEs by performing CoMP and the corresponding performance are analyzed.Based on the system frame-work above,the bias-based CoMP scheme is integrated in the system model.The coordination disk centered at the typical EUE is given based on the CoMP scheme.Expressions for CoMP probability and coverage probability are de-rived when the typical EUE receives joint transmission by passing MNN and the macro BS.Simulations verify the valid analysis and show the high probability for CoMP in moving networks.This paper also includes a performance com-parison among the analyzed scheme and two related works.CoMP with MNNs provides better coverage performance for passing EUEs.It can be found ex-treme densely deployment may decrease the network performance.The CoMP in moving networks increases the intensity of MNNs with the highest perfor-mance.(3)Besides performance analysis based on the spatial average,this paper provides the spatial distribution of signal-to-interference ratio in moving net-works by meta distribution.To describe the randomness of the BSs,a tractable network model is proposed based on stochastic geometry.The mobility of MNNs is described by an analytical mobility model.The traditional definitions of conditional success probability and meta distribution is extended in moving networks.In single-tier MNs with high mobility,this paper determines the mo-ments of the conditional success probability for the calculation of the MD and the mean local delay.A closed-form approximation of the variance is proposed for general speeds.The beta approximation for the meta distribution is derived by the approximated variance.Simulations verify the valid analysis.The results show that the mean local delay is finite and the variance is reduced to 0 in the high-mobility case of single-tier MNs.The single-tier model is then extended to a two-tier heterogeneous MN model.Tractable expressions of the mean success probability and the variance for each tier and the overall network are obtained.The theoretical simulations reveal that MNNs can reduce the variance among EUEs while keeping the mean success probability constant.In heterogeneous cellular networks,increasing the density of MNNs reduces the variance,in con-trast to the marginal effects of the density in static networks.