UAV deployment and caching scheme based on user preference prediction

In order to design an efficient edge caching policy considering spatial heterogeneity and temporal fluctuations of users’ content requests,a proactive caching scheme was proposed with UAV’s deployment location design based on user preference prediction.Firstly,each user’s preference characteristics were predicted based on file similarity and user similarity,and the request time and user location were also predicted when a content request occurs.Thereafter,on the basis of the predicted geographical location,request time and user preference,each UAV’s deployment location and the corresponding content placement were determined by virtue of clustering method based on SOM and AGNES.Simulation results show that the proposed scheme outperforms other three comparison schemes in terms of hit ratio and transmission delay.Furthermore,the results also reveal that content preference is correlated with different user features by different weights.Accordingly,different impact weights should be matched with different user features.     

无人机协作通信系统中基于区块链的频谱共享机制

为解决无人机与蜂窝网络在协作频谱共享中的激励与安全问题,提出了一种基于区块链的频谱共享机制。首先,为保证无人机在协作过程中的可靠性和真实性,采用基于信誉的赢家判决方法和维克里（Vickery）拍卖的付款规则,在保证无人机通信最小速率前提下提出最大化蜂窝网络传输容量的优化方案。其次,为避免集中机构带来隐私泄露等危险,提出基于区块链的拍卖框架,使用区块链存储并更新无人机的信誉值,并使用智能合约功能来验证和执行拍卖。最后,通过仿真验证区块链的防篡改性,表明所提机制具有激励兼容性并能提升蜂窝网络的传输容量,且与其他方案相比具有较低的协作中断百分比和较好的公平性。     

A QoE centric distributed caching approach for vehicular video streaming in cellular networks

Distributed caching‐empowered wireless networks can greatly improve the efficiency of data storage and transmission and thereby the users' quality of experience (QoE). However, how this technology can alleviate the network access pressure while ensuring the consistency of content delivery is still an open question, especially in the case where the users are in fast motion. Therefore, in this paper, we investigate the caching issue emerging from a forthcoming scenario where vehicular video streaming is performed under cellular networks. Specifically, a QoE centric distributed caching approach is proposed to fulfill as many users' requests as possible, considering the limited caching space of base stations and basic user experience guarantee. Firstly, a QoE evaluation model is established using verified empirical data. Also, the mathematic relationship between the streaming bit rate and actual storage space is developed. Then, the distributed caching management for vehicular video streaming is formulated as a constrained optimization problem and solved with the generalized–reduced gradient method. Simulation results indicate that our approach can improve the users' satisfaction ratio by up to 40%. Copyright © 2015 John Wiley & Sons, Ltd.     

Multi-tier cooperative caching in fog radio access network

Aiming at the problem of reducing the load of the backward link in the edge buffer and fog wireless access network technology,a multi-tier cooperative caching scheme in F-RAN was proposed to further reduce the backhaul traffic load.In particular,by considering the network topology,content popularity prediction and link capacity,the optimization problem was decomposed into knapsack subproblems in multi-tiers,and effective greedy algorithms were proposed to solve the corresponding subproblems.Simulation results show that the proposed multi-tier cooperative caching scheme can effectively reduce the backhaul traffic and achieve relatively high cache hit rate.     

Edge-first-based cooperative caching strategy in information centric networking

In order to optimize the replica placement in information centric networking,an edge-first-based cooperative caching strategy (ECCS) was proposed.According to the strategy,cache decision was made during the interest forwarding stage.The decision result and statistic information would been forwarded to upstream routers step by step.Utilizing the information,upstream nodes could update their cache information table immediately to achieve cooperative caching.The experimental results indicate ECCS can achieve salient performance gain in terms of server load reduction ratio,average hop reduction ratio,average cache hit ratio,compared with current strategies.     

大规模无线通信网络移动边缘计算和缓存研究

面向未来6G移动通信的大规模网络移动边缘计算与缓存技术,首先,介绍了大规模无线网络下移动边缘计算和缓存的架构与原理,并阐释了移动边缘计算和缓存技术在大规模无线网络中的必要性和普适性.接着,从计算卸载、边缘缓存、多维资源分配、用户关联和隐私保护这5个关键问题出发,综述和分析了移动边缘计算和缓存赋能大规模无线网络时会引入的...     

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.     

D2D协作边缘缓存系统中基于传输时延的缓存策略

为了满足5G系统低时延高可靠的需求,针对单缓存终端直传(D2D)协作边缘缓存系统,提出了一种基于传输时延的缓存策略.运用随机几何理论,将请求用户和空闲用户的动态分布建模为相互独立的齐次泊松点过程,综合考虑内容流行度、用户位置信息、设备传输功率以及干扰,推导出用户的平均传输时延与缓存概率分布的关系式.以平均传输时延为目标...     

Node centrality metric based caching mechanism in content-centric network

In order to reduce the cache redundancy as well as increase the cache hit ratios in content-centric networks,the node centrality metric based caching mechanism (CMC) was proposed.CMC utilized controllers to obtain the topology of the whole network and the idle rate of cache space.According to the connection relation of the topology,the degree centrality,closeness centrality and betweenness centrality of nodes were calculated.When CMC choose the caching nodes,it took the three metrics and the idle rate of cache space into account.Simulation results show that CMC can effectively increase the cache hit ratios and reduce the content fetching hops and average request delay compared with the traditional routing algorithms in CCN.     

P2P缓存系统中总开销最小的协作缓存策略

为降低P2P缓存系统中的全局开销,提出一种基于总开销最小的协作缓存策略。该策略综合考虑P2P缓存系统中的传输开销和存储开销,使用跨ISP域间链路开销、流行度、文件大小、存储开销来衡量文件的缓存增益。需要替换时,首先替换掉缓存增益最小的内容。实验结果表明,所提策略能够有效降低系统的总开销。     

无人机接替场景中相似度感知的边缘计算缓存算法

无人机边缘计算将无人机的移动性和边缘计算的源端处理优势相结合,可以在基础设施薄弱区域中提供计算、传输和存储服务,近两年得到了广泛关注。然而,无人机平台的计算、能量和存储容量有限,面对不断增长的内容服务请求,无人机边缘节点只能缓存部分流行度较高的内容。此外,为了保证服务的连续性,无人机之间往往需要接替提供缓存服务。现有的边缘缓存算法大多根据内容的请求历史来预测流行度,使得接替无人机上对新请求的内容服务启动缓慢,缓存命中率较低,限制了边缘计算缓存的性能。在此背景下,充分考虑无人机的移动性和内容请求的动态性,设计了一种针对接替无人机的动态缓存架构,并综合考虑接替无人机上缓存内容的流行度、相似性以及接替距离,提出了一种相似度感知缓存算法(Similarity-Aware Caching,SAC)。仿真结果表明,该缓存算法可以有效提升无人机接替场景中的缓存命中率和接替成功率。     

A framework of data caching for improving decoding efficiency of opportunistic network coding

Throughput performance of wireless networks can be enhanced by applying network coding (NC) technique based on opportunistic listening. The packets sent or overheard by a network node should be locally cached for the purpose of possible future decoding. How to manage the cache to reduce the overhead incurred in performing NC and, meanwhile, exploit performance gain is an interesting issue that has not been deeply investigated. In this paper, we present a framework for packet caching policy in multihop wireless networks, aiming at improving decoding efficiency, and thus throughput gain of NC. We formulate the caching policy design as an optimization problem for maximizing decoding utility and derive a set of optimization rules. We propose a distributed network coding caching policy (NCP), which can be readily incorporated into various existing NC architectures to improve NC performance gain. We theoretically analyze the performance improvement of NCP over completely opportunistic NC (COPE). In addition, we use simulation experiments based on ns‐2 to evaluate the performance of NCP. Numerical results validate our analytical model and show that NCP can effectively improve the performance gain of NC compared with COPE. Copyright © 2013 John Wiley & Sons, Ltd.     

Optimal chunk caching in network coding-based qualitative communication

Network processing in the current Internet is at the entirety of the data packet, which is problematic when encountering network congestion. The newly proposed Internet service named Qualitative Communication changes the network processing paradigm to an even finer granularity, namely chunk level, which obsoletes many existing networking policies and schemes, especially the caching algorithms and cache replacement policies that have been extensively explored in Web Caching, Content Delivery Networks (CDN) or Information-Centric Networks (ICN). This paper outlines all the new factors that are brought by random linear network coding-based Qualitative Communication and proves the importance and necessity of considering them. A novel metric is proposed by taking these new factors into consideration. An optimization problem is formulated to maximize the metric value of all retained chunks in the local storage of network nodes under the constraint of storage limit. A cache replacement scheme that obtains the optimal result in a recursive manner is proposed correspondingly. With the help of the introduced intelligent cache replacement algorithm, the performance evaluations show remarkably reduced end-to-end latency compared to the existing schemes in various network scenarios.     

Algorithm design on energy efficiency maximization for UAV-assisted edge computing

For the unmanned aerial vehicle (UAV)-assisted edge computing system,a two-stage alternative algorithm was proposed to solve the formulated complex non-convex problem.Firstly,the formulated non-linear fractional programming problem was reformulated to the equivalent parametric problem by using Dinkelbach method.Secondly,two sub-problems were further considered based on it.By employing the Lagrange duality method,the closed-form solutions for the central processing unit frequencies and the number of data bits were derived.Finally,based on the solutions obtained,the conditions that the source node prefers to offload/share its data and the relay chooses to forward the computation results,as well as the approaches to achieve high energy efficiency were revealed.Numerical results demonstrate that the proposed design can achieve a performance improvement of up to 20 times over the conventional schemes.     

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.     

车联网中基于MEC的V2X协同缓存和资源分配

针对车联网的多媒体业务快速增长,大量的数据交换为移动网络带来沉重负担的问题,构建了一种车联网中基于移动边缘计算的V2X协同缓存和资源分配框架.提出了V2X协同缓存与资源分配机制,实现网络内计算、缓存和通信资源的有效分配;利用图着色模型为卸载用户分配信道;采用拉格朗日乘子法对功率与计算资源进行分配.仿真结果表明,在不同的...     

基于5G无人机通信的多智能体异构网络选择方法

5G无人机通信网络和各种不同无线接入技术的结合使无线异构网络呈现多样化的发展趋势。然而,用户繁多且不同的业务请求对网络要求也不同,造成网络接入选择问题。提出了一种基于5G无人机通信的多智能体异构网络选择方法,将用户分为多个智能体,从用户端和网络端两个方面出发,将用户侧的时延和传输速率需求与网络侧的负载均衡需求综合考虑作为即时回报的相关参数,通过基于Nash Q-Learning的算法进行学习,得到异构网络环境下的网络选择决策模型。仿真结果表明,所提异构网络选择方法针对不同业务类型用户的需求均能选择合适的网络,同时均衡网络的负载,充分利用异构无线网络的资源。     

基于TG-PF的LTE-A中继蜂窝网络下行分层调度方法

设计了一种中继蜂窝网络的分层调度模型,将中继蜂窝小区的资源调度过程分为高层调度和低层调度两部分,分别由基站和中继站完成。所设计模型中,高层调度和低层调度分别采用PF算法和保障吞吐量的比例公平（TG-PF算法）,该算法充分利用了最大载干比（Max C/I）算法和比例公平（PF）算法的优势,能够有效地提升小区边缘的吞吐量,以满足中继蜂窝小区的系统吞吐量和调度公平性要求。仿真结果表明,所提方法能够以较低的调度公平性牺牲换取小区边缘吞吐量的较大提升。     

细胞神经网络超混沌系统同步及其在保密通信中的应用

本文研究四阶细胞神经网络超混沌系统同步方法,提出了一种基于细胞神经网络超混沌同步系统的扩展谱保密通信系统;这个保密通信系统不仅只需传递一个标量信号,而且由于采用了超混沌系统,所设计的保密通信系统具有更高的保密性。