Research On Radio Resource Management In Integrated Satellite And Terrestrial Networks

Fueled by the proliferation of users’ various mobile devices and applications, wireless mobile data traffic volumes are exponentially increasing, which results in the high capacity demands for mobile and wireless networks. Mobile satellite networks (MSS), as the indispensable component of next generation network (NGN), are facing this challenge as well. The problem with MSS is that the satellite communication relies on the Line of Sight (LOS) connection between mobile users and satellite, which is difficult to maintain, especially in urban or indoor coverage scenarios. Therefore, MSS are finding the way out by utilizing terrestrial networks to complement the satellite coverage, leading to the integration of the two networks and the vision of worldwide seamless coverage.The integrated satellite and terrestrial network (ISTN) is heterogeneous, consisting of the space-based network and terrestrial network in topology. Space-based network would be satellites locating in different orbits or even constellations while the terrestrial network is the cellular network implemented with terrestrial wireless standards. Both networks are controlled by MSS in an integrated architecture. The essential feature of ISTN is that MSS greatly enhances its coverage in traditional areas where its signal is blocked and improves the utilization of otherwise under-utilized MSS spectrum by deploying terrestrial cellular networks. The realization of this feature, however, largely depends on the ability of MSS to efficiently manage and allocate the radio resources such as system spectrum, power, bandwidth, access control to provide seamless and transparent Quality of Service to mobile users, despite of the differences between the two networks.This thesis focuses on achieving this goal by studying on the radio resource management methods in ISTN in an integrated architecture. The main work and contribution could be summarized as follows:To start with, ISTN network architecture and basic radio resource management methods are given. Centralized architecture is chosen for the deployment of terrestrial networks, forming an integrated network with MSS. Detailed analysis and description on the impact of cross-tier interference on system spectral efficiency and energy efficiency are provided, laying the foundation for the energy efficient interference coordination in Chapter3. A general fair QoS mapping mechanism is proposed, which utilizes the property of adaptive bandwidth adaption to provide admission gain for connection admission control in Chapter4. To ensure seamless vertical handover in ISTN, MIH based vertical handover mechanism is built, which adds MIH support to satellite interface and serves as solid foundation for future work.Next, considering that ISTN deploys satellite cell, macro cell, micro cell to satetisfy the various traffic requirements, management of cross-tier interference due to the overlap coverage needs to be studied to mitigate the negative impact of interference on the system capacity. Current interference mitigation strategies are incapable of simultaneously optimizing both spectral and energy efficiency. Therefore, an energy efficient interference management scheme is presented, which proposes channel matrix relaxation and stream power allocation to perform beamforming and power allocation. The scheme is capable of enhancing spectral efficiency while at the same time lowering the baseband processing power, thus optimizing the energy efficiency as well. Moreover, to accurately accommodate the various sources of power consumption in the nework, a detailed modulated power model is developed, based on which the energy efficient advantages of proposed scheme is verified from the perpective of energy consumption and and energy efficiency.Then, connection admission control (CAC) allocates resources to connections according to connection characteristics and network conditions. In ISTN, there exist different types of connections, i.e., new connections, horizontal handovers and vertical handovers. Considering QoS requirements of multiple services and connections, this thesis transforms the CAC scheduling problem into a Multi-Server Queue Scheduling problem and proposes N-NPPQ rule, namely, N-Non Preemptive Priority Queue, to dynamically serve new and handover connections; A reservation pool based admission control scheme is further proposed to distinguish the vertical and horizontal handovers. The reservation pool is constructed by utilizing the pseudo inverse property of satellite spotbeam and the handover probability of connections. With the proposed scheduling and admission control methods, connection blocking due to unfair allocation of system resources is reduced and resverd resource utilization is improved.Lastly, transparent vertical handover between terrestrial and mobile satellite network consists of different stages such as network discovery, handover triggering and handover decision, handover execution, among which triggering and decision are essential to achieve seamless and transparent handover in ISTN. Current studies lack detailed support for the vertical handover of mobile satellite networks as an independent wireless access network. Meanwhile, problems such as handover failures and unnecessary handovers and long handover decision delay exist in current triggering algorithms and multi-attribute based vertical handover decision algorithms. In view of these deficiencies, this thesis proposes a multi-threshold triggering and reputation based vertical handover shceme. The scheme calculates three handover failure and unnecessary handover pertinent thresholds to trigger handovers; it also builds a reputation system to facilitate the vertical handover decision to reduce handover delay. Simulation is conducted in the overlapping coverage area of ISTN and the proposed scheme is evaluated from the perspective of handover failures, unnecessary handovers, handover blocking, network load and handover decision delay, etc.