基于云无线接入网络的认知协作传输方法研究

To confront the explosively increasing demand of communication services, the next-generation cognitive cooperative transmission will widely use kinds of advanced communication technologies and densely deploy kinds of networks in order to alleviant the ever-increasing severe spectrum scarcity problem and ensure the high and reliable rate for information. By incorporating the cognitive cooperative transmission to cloud radio access network, this project investigates the cognitive cooperative relay transmission based on the cloud radio access network.in following three aspects: (1) In order to solve the bottleneck problems, such as the low utilization of spectrum, long waiting time for the cognitive users, and so on, which limits the practical application, this project builds a cognitive cooperative relay transmission model based on the spectrum sensing results and propose the hybrid orthogonal multiple access/non-orthogonal multiple access (NOMA) mode. (2) An incremental relaying transmission scheme with best relay selection is proposed to improve the reliability of the NOMA cognitive cooperative.relay system in cloud radio access network, where the direct transmission link or the cooperative transmission link is adaptively selected according to the quality of channels. (3) The “Interference Probability” is proposed to be a novel performance metric to evaluate the NOMA cognitive cooperative relay transmission with imperfect channel state information and a back-off power control scheme is explored to decrease the interference of licensed users caused by cognitive transmission. The innovative research will provide powerful support for achieving the reliable transmission based on cloud radio access network.

随着智能移动业务的迅猛发展，在云无线接入网络（C-RAN）中采用传统的正交多址接入模式和点对点传输已无法满足未来密集部署用户的高可靠、高速率、低时延体验。针对C-RAN网络频谱资源利用率低下、多用户传输的可靠性无法保证、多节点协作传输无法实际应用等难题，从三方面开展基于C-RAN的认知协作传输研究：（1）构建基于频谱感知结果的C-RAN认知协作传输模型，提出混合正交多址接入/非正交多址接入（NOMA）模式，解决频谱资源利用率低、认知用户传输等待时间长等制约实际应用的瓶颈问题；（2）提出基于最佳中继选择的递增中继传输策略，提高C-RAN网络中NOMA认知协作中继传输的可靠性；（3）提出将干扰概率作为实际非理想信道条件下NOMA认知协作中继传输的新增指标，探索降低认知用户对授权用户干扰的后向功率控制方法。研究成果将对早日实现C-RAN网络的可靠传输提供有力支撑。

本项目充分挖掘云无线接入网络（C-RAN）的潜力，将协作传输技术和认知无线电技术应用于C-RAN的分布式无线网络，结合功率域非正交多址接入（NOMA）技术，通过获取分集增益和最大的可接入带宽，满足5G移动通信中海量用户多样化业务的高可靠传输需求。首先，次用户根据频谱感知结果自适应地选择OMA或NOMA方式传输网络消息，考虑频谱感知结果出错的情况，推导了不同频谱感知结果下系统的中断概率，结果表明基于频谱感知结果的混合OMA/NOMA传输机制可以显著提高频谱资源的利用率。其次，研究了认知NOMA传输网络中的最佳中继选择机制，提出次用户协助的自适应NOMA传输策略，分析了瑞利衰落信道下主用户接收机采用选择合并时系统的中断性能。最后，考虑实际认知NOMA传输中，非理想的串行干扰消除（SIC）和非理想信道状态信息（CSI）不可避免，研究了覆盖式认知协作NOMA网络的中断概率和信道容量，为系统的设计者提供性能参考。本项目所获得的结果将为认知NOMA协作网络的系统设计提供理论依据和技术支持。