密集小蜂窝缓存部署、接入与回传一体化关键技术研究

Dense small cell networks and edge cache are two key techniques for the success of very high speed wireless communication systems. Besides, wireless backhaul has recently been considered as a vital alternative to meet the high transmission demand between small cells and core networks. This project focuses on studying a unified framework for cache deployment, access and backhaul design in dense small cell networks. By the optimal cache deployment and resource allocation for the access and backhaul links, the quality of service can be greatly enhanced in dense small cell networks .. The first part of this project is to study the deployment of cache in backhaul-aware small cell networks. There exist two main problems to be investigated. 1) In order to meet the diverse requirements of users, the required cache storage size is designed by taking consideration of heterogeneous flow densities and heterogeneous backhaul costs in different small cells. 2) In order to improve the quality of service in terms of success transmission ratio of users, an effective small cell cache placement mechanism is constructed to support differentiated user associations with cooperative multicell transmissions. . The second part of this project is to study resource allocation between access links and backhaul links in cache-enabled dense small cell networks. There are two main problems to be investigated. 1) When the access links of small cells and backhaul links are scheduled with orthogonal sub-channels, we aim at designing an optimal spectrum and power allocation scheme to maximize the throughput of access links and backhaul links. 2) When the sub-channels used by access links of small cells and backhaul links are not orthogonal, non-orthogonal multiple access is adopted for transmissions on the common spectrum bands. We plan to design an optimal power allocation scheme on different spectrum bands to maximize the spectrum efficiency.

密集小蜂窝组网与边缘缓存是未来移动通信系统的关键技术，无线回传技术又是小蜂窝与核心网间高速传输的保证，本项目研究密集小蜂窝组网中缓存部署、接入与无线回传一体化技术。通过缓存部署与资源优化，构建一个接入、回传与缓存资源相匹配的密集小蜂窝网络。首先，研究受回传带宽影响的密集小蜂窝缓存部署方案，包括两个研究方面：1）综合考虑小蜂窝异质流量密度与异质回传代价，设计缓存空间按需配备方案，以满足用户多样化需求；2）构建支持差异化用户接入与多小区协作传输的小蜂窝缓存业务存储机制，以提高用户成功传输概率。其次，研究支持缓存的密集小蜂窝网络接入与回传资源优化配置方案，包括两个研究方面：1）小蜂窝接入与回传信道部署在正交频段时，设计频谱分配与功率调度方案实现接入与回传流量的平衡；2）小蜂窝接入与回传信道部署在非正交频段时，采用非正交多址技术对回传频带进行有管控的复用，并通过频谱与功率分配最大化资源利用率。

密集小蜂窝网络是未来移动通信的重要形式，非正交多址接入技术是解决未来大规模接入的关键技术。针对密集小蜂窝网络与非正交多址接入融合场景，本项目深入研究密集小蜂窝网络的系统性能评估与优化方案，旨在高效利用功率资源满足用户多样化传输需求。研究成果分为两个主要方面：一、密集小蜂窝网络性能评估与性能提升方案研究。（1）在密集小蜂窝采用非正交多址接入场景下，研究了密集小蜂窝网络最佳分布式认知接入技术与最优无干扰保护半径设计，提出方案可以有效提升小蜂窝网络的频谱效率；（2）基于随机几何工具，研究了非正交多址接入密集小蜂窝网络最优上行功率控制问题，提出了利用非正交多址接入技术的小区远、近用户双功率补偿因子设计方案，提出方案可以提升小蜂窝网络的成功传输概率；（3）在有/无缓存辅助的情况下，推导了混合自动重传辅助的密集小蜂窝网络的中断概率，根据推导结果进一步研究了小蜂窝用户的最佳功率优化分配方案，提出方案可以降低小蜂窝网络的中断概率。二、小蜂窝网络非正交多址接入方案的优化设计。（1）当小蜂窝接入侧采用非正交多址技术时，在复杂干扰环境下研究了新的收发机设计方案，在满足全体用户服务质量的前提下，提出的分组协同优化方案可以显著降低蜂窝系统的总发射功耗。（2）针对协作多点传输的多小区/多天线蜂窝网络，研究了非正交多址接入的协作多小区蜂窝系统的功率最小化问题，提出了新颖的多天线非正交多址系统预编码优化设计架构，提出方案可以降低多小区蜂窝系统的发射功耗。（3）在智能反射面辅助的场景下，研究了非正交多址接入单小区/多小区蜂窝系统的功率分配与相位偏移联合优化问题，提出了用户发送功率、智能反射面相位偏移与基站接收机的三维联合优化方案，提出方案可以提升单小区/多小区蜂窝系统的功率效率。本项目研究成果可以高效管控密集小蜂窝网络的复杂干扰问题，显著提升小蜂窝网络的传输性能，为未来密集小蜂窝网络采用非正交多址接入技术组网打下坚实的理论基础。