In the fifth generation (5G) era, mobile networks will provide diversified services such as enhanced Mobile BroadBand (eMBB) and ultra-reliable low-latency communication (URLLC). Furthermore, the 5G architecture will be fog-like, enabling a functional split of network functionalities between cloud and edge nodes. In this article, we propose a non-orthogonal multiple access (NOMA)-enabled fog-cloud structure in a novel density-aware fog-based radio access networks (F-RAN) to tackle different aspects of high and low-density regions, in order to meet the heterogeneous requirements of eMBB and URLLC traffic. A framework of two different problem formulations is considered to cater the high throughput and low-latency requirements in a high and low-density mode respectively. In the first problem, we study the joint caching placement and association strategy aiming at minimizing the average delay. To deal with the first problem, we apply McCormick envelopes and Lagrange partial relaxation method to transform it into three convex sub-problems, which is then solved by proposing a distributed algorithm. The second problem is to jointly optimize transmission mode selection, subchannel assignment and power allocation to maximize the sum data rate of all fog user equipments (F-UEs) while satisfying fronthaul capacity and fog-computing access point (F-AP) power constraints. Moreover, for given transmission mode selection and subchannel assignment, the optimal power allocation is derived in a closed-form expression. Simulation results are provided to validate the effectiveness of the proposed NOMA-enabled F-RAN framework and reveal that the ultra-low latency and high throughput can be achieved by properly utilizing the available resources.

中文翻译：

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启用 NOMA 的雾无线电接入网络的性能分析

第五代（5G）时代，移动网络将提供增强型移动宽带（eMBB）、超可靠低时延通信（URLLC）等多样化服务。此外，5G 架构将像雾一样，在云和边缘节点之间实现网络功能的功能拆分。在本文中，我们在一种新型的基于密度感知雾的无线电接入网络 (F-RAN) 中提出了一种启用非正交多址 (NOMA) 的雾云结构，以解决高密度和低密度区域的不同方面问题，以满足eMBB和URLLC流量的异构需求。两个不同问题公式的框架被认为分别满足高密度和低密度模式下的高吞吐量和低延迟要求。在第一个问题中，我们研究了旨在最小化平均延迟的联合缓存放置和关联策略。针对第一个问题，我们应用麦考密克包络和拉格朗日偏松弛法将其转化为三个凸子问题，然后提出分布式算法求解。第二个问题是联合优化传输模式选择、子信道分配和功率分配，在满足前传容量和雾计算接入点 (F-AP) 功率约束的同时，最大化所有雾用户设备 (F-UE) 的总数据速率。此外，对于给定的传输模式选择和子信道分配，最佳功率分配以封闭形式导出。