Jiang Huilin

An improved graph coloring based small cell discovery scheme in LTE hyper-dense networks

Efficient discovery of multiple small cells is important to features such as small cell on/off, load balancing, CoMP (Coordinated Multi-point Transmission), e-ICIC (enhanced-Inter-Cell Interference Coordination) in LTE (Long Term Evolution) hyper-dense networks. However, severe interference in the Hyper-Dense Networks imposes great difficulty on efficient discovery of small cells. This paper proposes an improved graph coloring based scheme to facilitate the discovery of multiple small cells in Hyper-Dense Networks. Our proposed scheme is to divide small cells that are near to each other into different groups and let each group take turns to transmit synchronization signals so that interference between small cells are reduced. Graph coloring theory is employed in the division of small cells to guarantee that small cells within a certain distance are divided into different groups. Simulation results shows that using the proposed scheme detection probability of top 10 small cells is greatly improved compared to conventional scheme.

Impact of BS sleeping and user association scheme on delay in ultra-dense networks

Ultra-Dense Network (UDN) is a promising technology to cope with explosively increasing traffic demands. Delay is an important performance indicator in UDN. In this paper, we analyze the impacts of average sleeping time of BS and association radius on the mean delay in UDN. The explicit relationship between delay and the average sleeping time and association radius is presented. An M/G/1/N processor sharing vacation queueing is introduced to model small cell BS with sleeping strategy and user association, and the steady state probability of BS for each state and the association probabilities of UE are derived. The average transmission rates are obtained by using the statistical analysis under user association and dynamic traffic load. The mean delay is quantitatively studied from the perspective of probability characteristics based on all the possible association states and the corresponding transmission rates. The impacts of average sleeping time and association radius on the mean delay are analyzed and validated by simulation and numerical results.

Joint user association and ABS proportion optimization for load balancing in HetNet

In this paper, a user association scheme for load balancing in a downlink Heterogeneous cellular network (HetNet) incorporating almost blank subframe (ABS) for interference management is proposed. The joint user association and ABS optimization problem is formulated as maximizing a Logarithmic utility function. Since the joint optimization problem is non-convex and NP-hard, the block coordinate descent (BCD) method is employed to decouple the joint problem into two sub-problems (user association and ABS allocation) and solved in an iterative manner to obtain a suboptimal solution. Simulation results show the effectiveness of the proposed algorithm.

Joint Load Balancing and Coverage Optimizing Based on Tilt Adjusting in LTE Networks

The coverage optimization and Load Balancing (LB) for LTE networks based on adjusting Antenna Tilt Angle (ATA) of the cell are investigated. The network coverage is presented by the Coverage Factor (CF), which is defined as the ratio of the served user number to the total user number. The level of LB is evaluated by the Load Balancing Index (LBI). Both of the CF and the LBI are optimized by adjusting the tilt angle based on the Modified Particle Swarm Optimization (MPSO) algorithm. Simulation results show that the CF of our algorithm can obtain \(98\,\%\). The LBI, the network bandwidth efficiency and the system throughput are appreciably improved.The coverage optimization and Load Balancing (LB) for LTE networks based on adjusting Antenna Tilt Angle (ATA) of the cell are investigated. The network coverage is presented by the Coverage Factor (CF), which is defined as the ratio of the served user number to the total user number. The level of LB is evaluated by the Load Balancing Index (LBI). Both of the CF and the LBI are optimized by adjusting the tilt angle based on the Modified Particle Swarm Optimization (MPSO) algorithm. Simulation results show that the CF of our algorithm can obtain \(98\,\%\). The LBI, the network bandwidth efficiency and the system throughput are appreciably improved.

A MRO scheme for dual connectivity in LTE small cell enhancement scenario

Dual connectivity is a promising architecture for the future hyper-dense wireless cellular network to meet the rapidly increasing demand of wireless data transmission. In this architecture, the control plane (C-plane) and the user plane (U-plane) are split and a User Equipment (UE) simultaneously connects to two different cells: the Primary Cell (PCell) which is in charge of the C-plane, and the Secondary Cell (SCell) which provides high data rate. In this paper, the Mobility Robustness Optimization (MRO) problem of the PCell in intra-frequency dual connectivity Long Term Evolution Small Cell Enhancement (LTE SCE) scenario is investigated. We propose a MRO scheme where the handover (HO) parameters for a UE are adjusted according to its speed, the HO historical records and the user-cluster distance. Simulation results show that the proposed scheme has a significantly better mobility performance compared with that of the baseline scheme.