通过卫星网络和地面网络相互补充形成的星地融合网络可以有效克服两个网络独立运行时的缺点，提高卫星和地面网络的资源利用率，为用户提供高质量的无线服务。采用正交多址接入技术(Orthogonal Multiple Access， OMA)的星地融合网络虽然能有效地降低用户间的干扰，但用户独占时间/频谱资源块的分配方式会极大地限制资源利用率和接入网络的用户数量。 非正交多址接入技术(Non-Orthogonal Multiple Access，NOMA)通过功率域复用和串行干扰消除技术(Successive Interference Cancellation， SIC)可以同时同频发送多个信号，具有比OMA技术更高的资源利用率和用户公平性，受到学术界和工业界的极大关注。然而，相比于地面网络，卫星网络的信道衰落更复杂，对NOMA技术在星地融合网络的引入带来了挑战。此外，星地融合网络具有场景多样化和环境复杂等特点，如何准确地评估和分析相关性能是NOMA--星地融合网络面临的又一难题。本文在验证NOMA应用于卫星通信网络的可行性后，重点对引入NOMA技术后的星地融合网络各应用场景的资源分配和性能分析展开研究，具体工作包括： 1、研究了引入NOMA技术的卫星通信网络在下行和上行通信场景中提升用户公平性和资源利用率的方法。首先，在下行通信网络场景中，在保证用户采用NOMA技术的速率优于其采用OMA技术的前提下，提出了以系统合速率最大化为目标的功率分配优化算法，根据该功率优化算法推导了系统的遍历容量和能量效率及各NOMA用户的中断概率和平均误码率表达式。其次，在上行卫星通信系统中，获得了用户信干噪比与非精确信道估计、天线指向误差和用户位置的关系式。基于该信干噪比关系式，分析了 NOMA技术和OMA技术下各用户的遍历容量表达式。仿真结果表明：与OMA技术相比，引入NOMA技术后，下行卫星通信系统可以获得比OMA技术下更优的系统吞吐量和能量效率。此外，仿真结果还表明NOMA-上行卫星通信系统在系统容量方面具有更大的容量优势，以及训练序列长度、用户位置、链路衰落程度和用户位置都对系统性能有较大的影响。 2、研究了引入NOMA技术的星地协作网络在视距链路中断和中继节点存在的场景中提升资源利用率的问题和在中继节点不存在的场景中提升衰落用户通信质量的方法，提出了基于NOMA技术的星地协作网络模型和基于协作NOMA技术的星地协作网络模型。首先，通过中继节点的放大转发，建立了基于NOMA技术的星地协作网络模型，分析推导了各NOMA用户的中断概率和渐进中断概率与功率分配因子的关系表达式。然后，利用链路质量好的NOMA用户可以解码链路质量差用户信号的特点，将星地视距链路良好的用户与视距链路深衰落的用户配对作为一个NOMA组，建立了基于协作NOMA技术的星地协作网络模型，分析推导了系统的中断概率和遍历容量与功率分配因子的关系表达式。仿真结果表明：选用合适的功率分配因子，基于NOMA技术的星地协作网络模型中用户的通信性能均优于其OMA技术下的用户性能。同时，基于协作NOMA技术的星地协作网络模型在低发送功率配置下可以达到提高接入网络的用户数量和提高链路条件差用户性能的双重目的，进一步提高了资源利用率。 3、研究了引入NOMA技术的星地认知网络提升系统资源利用率及提升深衰落认知用户传输速率的问题，提出了一种基于NOMA技术的星地认知网络拓扑结构和一种基于NOMA技术的认知星地协作网络。在联合考虑卫星授权用户干扰温度和地面认知网络最大发送功率的限制条件下，首先，分析了基于NOMA技术的星地认知网络中，认知网络在共信道干扰下的系统容量与功率分配因子的关系表达式。然后，在基于NOMA技术的认知星地协作网络中，认知源节点采用NOMA技术广播信息并根据信道特性自适应地调节功率分配因子，认知中继节点通过中继-源节点功率比参数合理设置其传输功率并进行译码转发，以最大化认知用户的传输速率。仿真结果表明，与OMA技术相比，选用合适的功率分配因子，基于NOMA技术的星地认知网络可以取得更高的系统遍历容量和资源利用率。当功率比在一定范围内时，与采用OMA技术的协作中继方案相比，基于NOMA技术的认知星地协作网络的传输速率可提高13.7%左右；当两种方案传输速率相同时，该方案可节约功率30%左右。 关键词：星地融合网络；非正交多址接入；认知技术；协作传输；功率分配；中断概率，遍历容量

 By combing the terrestrial network and the satellite network, an important network architecture, referred as hybrid satellite terrestrial networks, has been proposed and expected to provide high quality of service for users and efficient use of spectrum resources of satellites and terrestrial networks. Although the orthogonal multiple access (OMA) scheme used in the hybrid satellite terrestrial networks can effectively reduce interference between users, it does restrict the improvement of resource utilization efficiency and the number of served users since only one user is served at any time/frequency slot. Having the ability to provide higher resource utilization efficiency and user fairing than that of OMA scheme, power-domain non-orthogonal multiple access (NOMA) has recently received significant attentions from research and industry. The key idea of this scheme is to superpose multiple signals in the power domain at the transmitter and use successive interference cancellation (SIC) at the receiver, and thus, the NOMA scheme can serve multiple users simultaneously on the same time/frequency block and provides an improved resource utilization efficiency and user fairing at the cost of reasonable increased complexity. However, compared to terrestrial networks, the channel fading of satellite networks is more complicated, which brings challenges to introduce the NOMA scheme into the hybrid satellite terrestrial networks. In addition, the diversity of scenes and the complex environment of the hybrid satellite terrestrial networks are another difficult problem for accurately evaluating and analyzing the relevant performance of the NOMA based hybrid satellite terrestrial networks. After verifying the feasibility of applying the NOMA scheme in satellite communication networks, this thesis focuses on the resource allocation and performance analysis of the application scenarios. The specific work includes: 1.The methods of improving user fairness and resource utilization in the NOMA based downlink and uplink satellite networks are analyzed. Firstly, in the downlink scenario, we obtain the power allocation coefficients by maximizing the sum rate while meeting the predefined target rates of each NOMA user. Then, based on that power allocation factor, the ergodic capacity and energy efficiency of the proposed system, as well as the outage probability and average symbol error rate of each NOMA user are derived. Secondly, in the uplink communication scenario, we analyze the relationship between users' SINRs and antenna pointing error, the location information of the user, and the inaccurate channel estimation. Based on these derivations, we derive the analytical expression for the achievable ergodic capacity of the considered network. The simulation results show that compared with OMA technology, NOMA based downlink satellite communication system can obtain better system throughput and energy efficiency, the NOMA based uplink satellite network has greater capacity advantage in system capacity and key parameters, such as the length of training data, user locations, fading configuration, and transmission power have significant influence on the performance of considered system. 2.By applying the NOMA scheme in hybrid satellite terrestrial networks, the methods of improving resource utilization efficiency in the scenario where relay node exists and users' line-of-sight links are unavailable and scenario where relay node does not exist are studied, models of NOMA based hybrid satellite terrestrial network and cooperative NOMA based hybrid satellite terrestrial network are proposed. Firstly, assuming the relay node adopted an amplify and forward strategy, we investigate and derive the closed-form expressions for the outage performance of the considered NOMA users in the NOMA based hybrid satellite terrestrial network. Secondly, since that a user with better channel condition in the NOMA scheme can decode the information for user with worse channel condition, we pair users with different direct link qualities as a NOMA group and provide the model of the cooperative NOMA based hybrid satellite terrestrial network, the relationships between the outage probability and the ergodic capacity of the considered system and the power allocation factor are analyzed. Simulation results show that if selecting an appropriate power allocation factor, the communication reliabilities of NOMA users in the NOMA based hybrid satellite terrestrial network are better than that with the OMA technology, which reveals that the introduction of NOMA technology can further improve the resource utilization. Moreover, we also can find from the simulation results that, in the cooperative NOMA based hybrid satellite terrestrial network, under the low transmit power configuration, the proposed solution can achieve the dual purpose of increasing the number of users accessing the network and improving the user performance of the link condition. 3.By applying the NOMA scheme in hybrid satellite terrestrial networks, the methods of enhancing resource utilization efficiency for cognitive network and quality of communication for deep fading user are investigated, models of NOMA based hybrid satellite terrestrial cognitive networks and NOMA based cognitive satellite terrestrial cooperative networks are proposed. Firstly, by jointly considering the constricts of limited transmission power of cognitive network and limited interference can suffered at the primary network, we analyze the relationship between the performance of the considered network and power allocation coefficient. Secondly, in the NOMA based cognitive satellite terrestrial cooperative network, a cooperative relay transmission scheme based on NOMA technology is proposed. Specially, on one hand, the source node with the proposed strategy can utilize NOMA technology to broadcast information and adaptively adjust power allocation factor according to the channel characteristics to maximize the transmission rate of the deep fading cognitive user. On the other hand, the transmission power of relay node with decode-and-forward is reasonably set by relay-source power ratio parameter. Simulation results show that compared with OMA technology, with appropriate power allocation factor, the proposed NOMA based hybrid satellite terrestrial cognitive network can achieve higher system capacity, the transmission rate of the NOMA based cognitive satellite terrestrial cooperative network will improve about 13.7% within a certain limit of relay-source power ratio. Moreover, the total power of the NOMA based cognitive satellite terrestrial cooperative network will reduce 30% in the same transmission rate, thus minimize the power consumption. Key words: Hybrid satellite terrestrial networks; non-orthogonal multiple access (NOMA); cognitive technology; cooperative transmission; power allocation; outage probability; ergodic capacity.