Research On Self-Organizing Networks In LTE-A Heterogeneous Networks

Heterogeneous network (HetNet) deployment is investigated by 3GPP LTE-A as a promising paradigm for further enhancing network performance. The main idea of HetNet is to overlay low-power low-cost stations on the coverage holes and hotspot areas to complement the conventional macrocell for coverage extension and capacity enhancement. Self-organizing network (SON), which aims at enhancing network efficiency as well as reducing capital expenditure and operational expenditure, is also adopted by 3 GPP LTE-A as a new operation and maintenance mechanism. This paper researches on the applications of SON in HetNet, and three use cases are studied.The first use case is to addresses the problem of cooperative communication in eNB-HeNB network. In this paper, the eNB-HeNB network is regarded as a cognitive radio network, and the R-C-P strategy, i.e. joint relay selection, channel assignment and power allocation strategy, is studied. A heuristic node grouping algorithm is proposed to derive a suboptimal solution to R-C-P problem. The proposed algorithm can improve system fairness level while not reducing the throughput.The second use case is to addresses the problem of load balancing for multi-hop cellular network with fixed relays in the context of SON. The designed SON algorithm, namely RSPC-RL, is based on two ideas:relay node reference signal power control and multi-agent reinforcement learning. In the proposed RSPC-RL algorithm, the relay node is modeled as an agent that learns an optimal policy of reference signal power control from its interaction with environment to balance the load distribution of the network through dynamically changing its coverage area. Numerical results show the significant performance gain brought about by the proposed algorithm RSPC-RL.The third use case is to addresses the problem of handover decision in the heterogeneous networks. Current researches on this topic concentrate mainly on the two-tier networks. This paper investigates the handover decision scheme for a more complex network:three-tier macrocell/relay/femtocell network. The unique characteristics of the inter-tier handover in three-tier networks are analyzed in this paper and an effective handover algorithm is proposed to reduce the frequent and unnecessary handovers based on the ideas of dwell probability and handover priority. Simulation results show that the proposed algorithm significantly reduces the number of handovers while maintaining the call dropping rate at the same level.