Cooperative caching algorithm of UAV and user in UAV-assisted cellular network

Aiming at the problem of mass data content transmission and limited wireless backhaul resource of UAV in UAV-assisted cellular network,a cooperative caching algorithm for cache-enabled UAV and user was proposed.By deploying caches on UAV and user device,the popular content requested by user was cached and delivered,which alleviated the backhaul resource and energy consumption of UAV,reduced the traffic load and user delay.A joint optimization problem of UAV and user caching was established with the goal of minimizing user content acquisition delay,and decomposed into UAV caching sub-problem and user caching sub-problem,which were solved based on alternating direction method of multiplier and global greedy algorithm respectively.The iterative way was used to obtain convergent optimization result,and the cooperative caching of UAV and user was realized.Simulation results show that the proposed algorithm can effectively reduce user content acquisition delay and improve system performance.     

基于随机几何理论的流行度匹配边缘缓存策略

异构网络边缘缓存机制是解决传统回程传输链路负载过大的可靠技术之一,但已有的缓存策略往往不能与被请求数据的流行度相匹配。为了解决这一问题,该文提出一种流行度匹配边缘缓存策略(PMCP),该策略能够根据流行度参数匹配对应的文件缓存概率以最大限度提升通信可靠性并降低回程带宽压力。基站的平面位置通过随机几何建模,文件的被请求概率则通过齐夫分布建模。蒙特卡罗仿真结果表明缓存机制能够有效降低回程带宽压力,且所提出缓存策略的可靠性优于对比策略。     

小小区网络中基于本地存储协作传输策略的增益

网络的密集化是满足未来移动通信系统高吞吐量需求的有效手段,但当业务负载高时其吞吐量受到小区间干扰的严重制约。在基站端存储流行文件可以降低回传链路的成本和文件的下载时间,也为无需高容量回传链路进行基站协作提供了可能。本文分析了在小基站部署存储器后基站协作所能带来的吞吐量增益,推导了基于存储的基站协作策略的平均吞吐量,并与无干扰管理的基准小小区网络的吞吐量进行比较。分析和仿真结果表明,本地存储带来的性能增益在网络负载较高时和文件请求分布集中时非常明显。      

Caching in heterogeneous satellite networks with fountain codes

In this paper, we investigate the performance of caching schemes based on fountain codes in a heterogeneous satellite network. We consider multiple cache-aided hubs, which are connected to a geostationary satellite through backhaul links. With the aim of reducing the average number of transmissions over the satellite backhaul link, we propose the use of a caching scheme based on fountain codes. We derive a simple analytical expression of the average backhaul transmission rate and provide a tight upper bound on it. Furthermore, we show how the performance of the fountain code-based caching scheme is similar to that of a caching scheme based on maximum distance separable codes.     

移动边缘计算中基于联邦学习的视频请求预测和协作缓存策略

随着互联网社交平台的崛起和移动智能终端设备的普及,自媒体短视频、直播等视频业务蓬勃发展,人们对高质量视频服务的需求也急剧上升。与此同时,连接到核心网络的大量智能设备增加了回程链路的负载,传统的云计算难以满足用户对视频服务的低延迟要求。移动边缘计算(MEC)通过在网络边缘部署具有计算和存储能力的边缘节点,通过在更靠近用户的边缘侧提高计算和存储服务,降低了数据传输时延进而缓解了网络阻塞。因此,基于MEC架构,该文充分利用网络边缘资源,提出了基于联邦学习的视频请求预测和视频协作缓存策略。通过利用多个边缘节点对提出的深度请求预测模型(DRPN)视频请求预测模型进行联邦训练,预测视频未来的请求情况,然后量化缓存内容所带来的时延收益并协作地以最大化该时延收益为目的进行缓存决策。该文分析了真实数据集MovieLens,模拟了视频请求缓存场景并进行实验。仿真结果表明,相比于其他策略,所提策略不仅能有效降低用户等待时延,在有限的缓存空间中提高内容多样性,从而提高缓存命中率,降低缓存成本,还能降低整个系统的通信成本。     

QoE-aware video cooperative caching and transmission mechanism based on TWDM-PON and C-RAN

The quality of user experience suffers from performance deterioration dramatically due to the explosively growing data traffic.To improve the poor performance of cell-edge users and heavy-load cell users,which caused by dense network and load imbalance respectively,an QoE-aware video cooperative caching and transmission mechanism in cloud radio access network was proposed.Cooperative gain-aware virtual passive optical network was established to provide cooperative caching and transmission for video streaming by adopting collaborative approach in optical domain and wireless domain.Furthermore,user experience for video streaming,bandwidth provisioning and caching strategy were jointly optimized to improve QoE,which utilized the methods of dynamic caching in optical domain and buffer level-aware bandwidth configuration in wireless domain.The results show that the proposed mechanism enhances the quality of user experience and effectively improves the cache hit rate.     

基于可重构路由器上缓存的流媒体协作分发策略

提出一种新颖的基于可重构路由器上缓存的协作分发策略来加速流媒体。通过网络存储即多个边缘路由器节点对热点视频数据进行合作缓存,就近为用户提供服务,从而使得流媒体服务器的性能要求尤其是带宽需求得到巨大的降低,骨干网传输的流量也明显减少,同时用户响应延迟也得到明显的改善。此外,实现了一个原型系统来评价基于路由器上缓存的流媒体协作分发策略的性能,结果表明该方案相比于现有的方案在改善网络性能以及用户体验方面取得很大的提升。     

Fair inter‐TAP routing and backhaul assignment for wireless mesh networks

Although limiting the number of backhauls, specifically chosen transit access points (TAPs) that forward traffic from other TAPs, reduces the overall costs of a wireless mesh network (WMN), an egress bottleneck is induced, which aggregates traffic and limits the bandwidth. To avoid such problems while working to minimize budgetary expenses, we balanced traffic flow on ‘to‐be‐determined’ backhauls and adjacent links, a mixed nonlinear‐and integer‐programming problem that minimizes the aggregated flow subject to budget, backhaul assignment, top‐level load‐balanced routing, and link capacity constraints. Two algorithms are proposed, weighted backhaul assignment (WBA) and greedy load‐balanced routing (GLBR), that operate in conjunction with Lagrangean relaxation (LR), used for constructing LR‐based heuristics and also as a means of quantification and evaluation of the proposed algorithms. Experiment results show that the proposed algorithms achieve near‐optimization, outperforming related solutions. Copyright © 2008 John Wiley & Sons, Ltd.     

Caching resource management of mobile edge network based on Stackelberg game

Mobile edge caching technology is gaining more and more attention because it can effectively improve the Quality of Experience (QoE) of users and reduce backhaul burden. This paper aims to improve the utility of mobile edge caching technology from the perspectie of caching resource management by examining a network composed of one operator, multiple users and Content Providers (CPs). The caching resource management model is constructed on the premise of fully considering the QoE of users and the servicing capability of the Base Station (BS). In order to create the best caching resource allocation scheme, the original problem is transformed into a multi-leader multi-follower Stackelberg game model through the analysis of the system model. The strategy combinations and the utility functions of players are analyzed. The existence and uniqueness of the Nash Equilibrium (NE) solution are also analyzed and proved. The optimal strategy combinations and the best responses are deduced in detail. Simulation results and analysis show that the proposed model and algorithm can achieve the optimal allocation of caching resource and improve the QoE of users.     

Self‐organising cluster‐based cooperative load balancing in OFDMA cellular networks

Mobility load balancing (MLB) redistributes the traffic load across the networks to improve the spectrum utilisation. This paper proposes a self‐organising cluster‐based cooperative load balancing scheme to overcome the problems faced by MLB. The proposed scheme is composed of a cell clustering stage and a cooperative traffic shifting stage. In the cell clustering stage, a user‐vote model is proposed to address the virtual partner problem. In the cooperative traffic shifting stage, both inter‐cluster and intra‐cluster cooperations are developed. A relative load response model is designed as the inter‐cluster cooperation mechanism to mitigate the aggravating load problem. Within each cluster, a traffic offloading optimisation algorithm is designed to reduce the hot‐spot cell's load and also to minimise its partners’ average call blocking probability. Simulation results show that the user‐vote‐assisted clustering algorithm can select two suitable partners to effectively reduce call blocking probability and decrease the number of handover offset adjustments. The relative load response model can address public partner being heavily loaded through cooperation between clusters. The effectiveness of the traffic offloading optimisation algorithm is both mathematically proven and validated by simulation. Results show that the performance of the proposed cluster‐based cooperative load balancing scheme outperforms the conventional MLB. Copyright © 2013 John Wiley & Sons, Ltd.     

基于NOMA的全双工多层异构网下行链路覆盖分析

针对异构网（Heterogeneous Network,HetNet）无线回程,现有研究主要集中于提升网络吞吐量,而对回程覆盖性能研究较少.由此,本文构造了一种在小小区基站（Small cell Base Station,SBS）上结合全双工（Full-Duplex,FD）和非正交多址接入（Non-Orthogonal Multiple Access,NOMA）技术的大规模多输入多输出（Multiple Input Multiple Output,MIMO）辅助多层HetNet模型.利用信干比（Signal-to-Interference Ratio,SIR）来模拟有源SBS的分布,得出不同类型接收端的干扰;然后推导了移动用户（Mobile User,MU）下行链路覆盖概率闭合表达式.仿真和数值结果表明,SBS下行链路覆盖概率会随着小小区下行链路功率共享系数的增加而减小;此外,通过对比NOMA和正交多址接入（Orthogonal Multiple Access,OMA）以及FD和半双工（Half-Duplex,HD）对下行链路覆盖性能的影响,本文提出的方案能显著提升网络性能.     

Dynamic Cooperative Base Station Selection Scheme for Downlink CoMP in LTE-Advanced Networks

Coordinated Multi-Point (CoMP) transmission is a technique proposed to enhance the spectral efficiency and system throughput in an interference limited cellular networks. In CoMP joint processing (JP) scheme multiple base stations (BSs) are coordinately transmit data streams to each user. As more than two base stations are involved, abundant spatial resources are exploited and more backhaul spectrum for JP cooperation is required. The backhaul architecture for CoMP JP is crucial to provide low latency, unlimited capacity, less power consumption, and perfect synchronization among the BSs. However, satisfying all these constraints is impossible as the number of cooperative BSs increases for each user. In this paper, a dynamic cooperative base station selection scheme is proposed to reduce the backhaul load for CoMP user by selecting the appropriate number of coordinated BSs from the CoMP cluster to ensure the certain quality of service (QoS). In particular, for cell edge user the number of cooperative BSs per user has been selected in order to achieve reduced overhead and the allocation of backhaul capacity is performed under the max–min fairness criterion. Simulation results show that the proposed selection scheme achieves significant performance improvement than other transmission modes in terms of the average sum rate per backhaul use and minimal total power consumption.     

Hierarchical task offloading in heterogeneous cellular network:modeling and optimization

To improve the efficiency of computation offloading,a hierarchical task offloading framework based on device-to-device (D2D) communication,mobile edge computing and cloud computing was proposed,in which cooperative D2D relay technology was introduced to assist users to access remote computing resources.Considering the negative effects of uplink channel congestion,limited edge computing capability,D2D reuse interference and backhaul delay of cloud computing in the multi-user scenario of the proposed framework,a game theory based offloading scheduling and load balancing scheme was developed by fully taking advantage of the computing and communication resources in the proposed framework.The simulation results demonstrate that the proposed scheme can effectively reduce end-to-end delay and offloading energy consumption,and also has good stability even when the network resources are limited.     

Design of in-network caching scheme in CCN based on grey relational analysis

In-network caching is one of the most important issues in content centric networking （CCN）, which may extremely influence the performance of the caching system. Although much work has been done for in-network caching scheme design in CCN, most of them have not addressed the multiple network attribute parameters jointly during caching algorithm design. Hence, to fill this gap, a new in-network caching based on grey relational analysis （GRA） is proposed. The authors firstly define two newly metric parameters named request influence degree （RID） and cache replacement rate, respectively. The RID indicates the importance of one node along the content delivery path from the view of the interest packets arriving The cache replacement rate is used to denote the caching load of the node. Then combining hops a request traveling from the users and the node traffic, four network attribute parameters are considered during the in-network caching algorithm design. Based on these four network parameters, a GRA based in-network caching algorithm is proposed, which can significantly improve the performance of CCN. Finally, extensive simulation based on ndnSIM is demonstrated that the GRA-based caching scheme can achieve the lower load in the source server and the less average hops than the existing the betweeness （Betw） scheme and the ALWAYS scheme.     

面向接入回传一体化的毫米波空地网络建模与分析

无人机(UAV)作为空中基站有望成为传统地面网络的有力补充,以提供灵活覆盖和容量增强的解决方案.然而,大多现有研究忽略空中基站的无线回传这一实际因素对网络性能和用户体验的影响.为此,考虑接入回传一体化的空地毫米波蜂窝网络场景,其中无人机提供热点流量传输服务,地面基站(TBS)提供无人机回传链路并且服务非热点区域用户,以...     

Design and implementation of CLASS: A Cross-Layer ASSociation scheme for wireless mesh networks

This paper focuses on the design and implementation of CLASS, a Cross-Layer Association scheme for IEEE 802.11-based multi-hop wireless mesh networks. The widely-used association strategy in traditional IEEE 802.11 wireless LANs allows a Mobile Station (MS) to scan wireless access links and then associate with the Access Point (AP) that has the best Received Signal Strength Indication (RSSI) value. Unlike traditional wireless LANs, IEEE 802.11-based wireless mesh networks consist of a multi-hop wireless backhaul. As such, the performance experienced by an MS after association with a specific Mesh Access Point (MAP) depends heavily on the conditions of both the access link (e.g., traffic load of associated stations, the frame error rate between an MS and an MAP) and the mesh backhaul (e.g., end-to-end latency and asymmetric uplink/downlink transportation costs). That is, selecting the MAP that yields the “best” performance depends on several factors and cannot be determined solely on the RSSI of the MS-MAP access link. CLASS uses an end-to-end airtime cost metric to determine the MAP to which an MS should associate. The airtime cost metric is based on the IEEE 802.11s, and comprises the access link airtime cost and the backhaul airtime cost. The proposed association scheme considers the frame error rate for various packet sizes, the available bandwidth on the access link after the association of the new MS, and the asymmetric uplink and downlink transportation costs on the backhaul. All experimental results are based on actual Linux-base testbed implementation. We also implement a general Cross-Layer Service Middleware (CLSM) module that is used to monitor network conditions and gather relevant metrics and factor values. Experimental results show that the proposed association scheme is able to identify the MAP which yields the highest end-to-end network performance for the mobile stations after their associations.     

面向软件定义无线接入网的高效协作内容缓存算法

为了缓解海量的移动业务数据与容量受限的无线接入网回传链路之间的矛盾,本文提出一种面向软件定义无线接入网（SD-RAN）的协作内容缓存网络架构.在宏蜂窝基站（MBS）的控制管理下,小蜂窝基站（SBS）可以在存储单元有序存储一些高流行度的内容.针对SBS存储单元空间受限问题,进一步提出SD-RAN网络架构下的协作内容缓存算法.该算法中,每个SBS缓存空间被分割成两部分：（1）用于存储全网流行度最高的公共内容以保证各小蜂窝小区本地命中率.（2）用于存储流行度较高的差异化的内容以促进MBS内SBS之间的协作.在此基础上,解析推导具有最优平均内容获取开销的分割参数闭合表达式.仿真结果表明该算法在不同系统参数条件下能显著降低SD-RAN的平均内容获取开销.     

Load balance in hierarchical routing network

In this article, the problem of load balance in hierarchical routing network is studied. Since conventional shortest path first (SPF) algorithm over aggregated topology in hierarchical routing network may result in worse routing performance, a traffic sharing path selection algorithm and a variable weight scheme are put forward for hierarchical routing network, which can equilibrate the utilities of link resources and reduce the blocking probability of connections with the improvement on survivability. Simulations are conducted to evaluate proposed variable weight and traffics balance (VWTB) algorithm, which combines traffic sharing and variable weight. From the simulation results, it can be found that the proposed VWTB algorithm can balance the traffics and equilibrate the utilities of link resources significantly.     

Cooperative caching for content dissemination in vehicular networks

The explosive growth of mobile data traffic has made cellular operators to seek low‐cost alternatives for cellular traffic off‐loading. In this paper, we consider a content delivery network where a vehicular communication network composed of roadside units (RSUs) is integrated into a cellular network to serve as an off‐loading platform. Each RSU subjecting to its storage capacity caches a subset of the contents of the central content server. Allocating the suitable subset of contents in each RSU cache such that maximizes the hit ratio of vehicles requests is a problem of paramount value that is targeted in this study. First, we propose a centralized solution in which, we model the cache content placement problem as a submodular maximization problem and show that it is NP‐hard. Second, we propose a distributed cooperative caching scheme, in which RSUs in an area periodically share information about their contents locally and thus update their cache. To this end, we model the distributed caching problem as a strategic resource allocation game that achieves at least 50% of the optimal solution. Finally, we evaluate our scheme using simulation for urban mobility simulator under realistic conditions. On average, the results show an improvement of 8% in the hit ratio of the proposed method compared with other well‐known cache content placement approaches.     

虚拟化云无线接入网络下基于在线学习的网络切片虚拟资源分配算法

针对现有研究中缺乏云无线接入网络(C-RAN)场景下对网络切片高效的动态资源分配方案的问题,该文提出一种虚拟化C-RAN网络下的网络切片虚拟资源分配算法。首先基于受限马尔可夫决策过程(CMDP)理论建立了一个虚拟化C-RAN场景下的随机优化模型,该模型以最大化平均切片和速率为目标,同时受限于各切片平均时延约束以及网络平均回传链路带宽消耗约束。其次,为了克服CMDP优化问题中难以准确掌握系统状态转移概率的问题,引入决策后状态(PDS)的概念,将其作为一种“中间状态”描述系统在已知动态发生后,但在未知动态发生前所处的状态,其包含了所有与系统状态转移有关的已知信息。最后,提出一种基于在线学习的网络切片虚拟资源分配算法,其在每个离散的资源调度时隙内会根据当前系统状态为每个网络切片分配合适的资源块数量以及缓存资源。仿真结果表明,该算法能有效地满足各切片的服务质量(QoS)需求,降低网络回传链路带宽消耗的压力并同时提升系统吞吐量。