Research On Cooperative And Coordinated Enhancement Mechanism In Heterogeneous Networks

As mobile Internet becomes the trend of the future Internet, mobile communication networks are considered the first choice for mobile terminal to access the Internet due to its widespread deployment as well as PC will be replaced with the mobile equipment to play the role of user terminal. This suggests that those traffics accessing the Internet via wired links will be transferred to wireless communication system, which poses challenges to the access capacity of mobile communication system. Meanwhile, statistics show that80%～90%of the system throughput originates indoors and in the hotspot nomadic scenarios in the future, which implies that the indoor, low-mobility and hotspot communications are becoming more and more important in the mobile Internet era. In order to enhance the system performance in these scenarios, some low power nodes are introduced on the basis of tranditional macrocell in next mobile communication system, called heterogeneous networks (HetNets).Corresponding to the evolution of network architecture, the network protocols and handling mechanism in traditional networks should be modified and enhanced to fit for the HetNets. Cooperative and coordinated communication is one of the most important enhancing technologies in HetNets. On one hand, it includes macrocell and low power node in HetNets. The former is deployed systematically and works in open model, the latter may be deployed by users themselves and could work in close or open or hybrid model. Severe interference will take place when macrocell and low power node operate in co-channel deployment. In this case, coordinated operation via message exchange between nodes is an effective means of mitigating interference. On the other hand, the introduction of low power nodes provides the architectural basis for the practical application of cooperative communication. The nodes are distributed densely in HetNets, which makes it possible to cooperate among multiple nodes. In particular, the emergence of relay node in HetNets promotes the process of implementation of relay cooperative communication. In summary, cooperative and coordinated mechanism has important significance for HetNets because it can enhance the performance of HetNets effectively.In this paper, we study on how the cooperative and coordinated mechanism improves the performance of HetNets, including interference coordination and power allocation. First, severe interference is one of the main challenges in HetNets. In this paper, we will study time and frequency domain interference coordination in HetNets. In the process, we design a hotspot gravitation mobility model for the evaluation and simulation of HetNets. Secondly, one difficulty in the process of practical application of cooperative and coordinated mechanism is how to reduce the signaling overhead caused by message exchange. This problem will be studied in this paper taking the scene of relay power allocation as the instance. The main contributions and innovations are listed as follows:1) Proposes a uniform field theory based framework for hotspot mobility modeling and designs a concrete realization for HetNets, called hotspot gravitation mobility model.HetNets are designed for the special scenes including indoor, hotspot and coverage holes, where the distribution of users and traffic is heterogeneous. As a matter of fact, people’s daily movements are usually limited among some places, which suggest that human traces exhibit a high degree of regularity and aggregation in large temporal and spatial scale. In other word, One’s daily movement is comprised of various hotspots. So, hotspots are the more general scenes than the scenarios of uniform distribution in realistic world and mobility models for hotspot scenarios need to be further studied. Inspired by the similarity between man’s behavior in realistic world and the particle’s motion under the action of field in physics, we propose a novel framework based on unified field theory for hotspot mobility modeling in this paper, in which people’s movements can be taken as the results of action of certain field. Considering the field as gravitation field, a concrete realization of this framework, called hotspot gravitation mobility model (HGMM), is designed. Simulation results show that the trajectory produced by HGMM could more accurately accord with the actual conditions that we observe in real world. HGMM is suitable for the performance evaluation and simulation of HetNets.2) Proposes a scheme of general time domain interference coordination for the scenario of macro-femto co-channel deployment.Time domain interference coordination (TDIC) is a typical interference coordination scheme based on resource partition, in which the transmission duration of interfering source is reduced in order to improve the performance of interfered node. We design a dual-parameter controlled scheme based on single-parameter controlled TDIC, called general time domain interference coordination. The advantage of the proposed scheme is demonstrated on achievable operation region, throughput, implementation and flexibility via theory analysis. Also, simulation results show that the proposed scheme performs better.3) Proposes a hybrid approach of time and frequency domain interference coordination in macro-femto co-channel deployment, and designs the corresponding resource allocation algorithm.Frequency domain interference coordination (FDIC) is another typical resource partition based interference coordination scheme, in which one of the interfering nodes is transferred to another free spectral band to avoid interference. Analyzing and comparing the drawbacks and merits of FDIC and TDIC, we could find the complementary relationship of these two methods. Therefore, we propose a hybrid domain interference coordination (HDIC) scheme by combining FDIC and TDIC. The key of the proposed scheme is resource allocation. Thus, a two-round algorithm of resource allocation is designed. Simulation results show that HDIC performs better than TDIC and FDIC on the system capacity and the number of users that satisfy their datatate demand.4) Proposes a power allocation method in amplify-and-forward relay system with energy constraint, in which the results of power allocation could keep available as long as possible when the source node moves.On the path from theory to practice of cooperative and coordinated communication, one of the challenges is how to reduce the signaling overhead caused by information exchange to decide the parameters. We will take the AF relay scene with power constraint as example and study the power allocation problem between source and relay to maximize the lifetime of allocated results when the source node moves. However, it is too complex and difficult to achieve the optimal solution. Therefore, a suboptimal solution is proposed. Numerical simulation results show that there only exists extremely small error between suboptimal and optimal solutions. So, it could be taken as a quasi-optimal solution of the problem.Innovation1) provides the basis for the performance evaluation andsimulation of subsequent research. Innovation2) and3) study on the main challenge in HetNet, namely interference coordination, in the simulation of which the hotspot mobility model proposed in innovation1) is applied. In innovation4), we try to deal with the universal problem in cooperative and coordinated communication. Although only a special scenario is selected as the example to study on, the research approach is also suitable for other scenarios, such as the time parameter selection in innovation2).