Max-Min Fair RIS-Aided Rate-Splitting Multiple Access for Multigroup Multicast Communications

Rate-splitting multiple access(RSMA)can cope with a wide range of propagation conditions in multigroup multicast communications through rate splitting optimization.To breakthrough the grouprate limited bottleneck,reconfigurable intelligent surface(RIS)technique can be introduced to assist wireless communications through enhancing the channel quality.In RIS-aided RSMA multigroup multicasting,how to provide fair and high-quality multiuser service under power and spectrum constraints is essential.In this paper,we propose a max-min fair RIS-aided rate-splitting multiple access(MMF-RISRSMA)scheme for multigroup multicast communications,where the rate fairness is obtained by maximizing the minimum group-rate.In doing so,we jointly optimize the beamformers,the rate splitting vector at the transmitter,as well as the phase shifts at RIS.To solve it,we divide the original optimization problem into two subproblems and alternately optimize the variables.The beamforming and rate splitting optimization subproblem is solved by using the successive convex approximation technique.The phase shift optimization subproblem is solved through the penalty function method to achieve a rank-one locally optimal solution.Simulations demonstrate that the proposed MMF-RIS-RSMA scheme can obtain significant performance gain in terms of the minimum group-rate.

Coded Multicasting for Content Delivery over Predictable Time-Varying Satellite Communication Networks

With the development of astronautic technology, communication satellites now have a tremendous gain in both quantity and quality, and have already shown their capability on multi-functional converged communication other than telecommunication. Under this circumstance, increasing the transmission efficiency of satellite communication network becomes a top priority. In this paper, we focus on content delivery service on satellite networks, where each ground station may have prefetched some file fragments. We cast this problem into a coded caching framework so as to exploit the coded multicast gain for minimizing the satellite communication load. We first propose an optimization-based coded multicast scheme by considering the special property that the satellite network topology is predictable and timevariant. Then, a greedy based fast algorithm is proposed, which can tremendously reduce the computation complexity with a small loss in optimality. Simulation experiments conducted on two Walker constellation satellite networks show that our proposed coded multicast method can efficiently reduce the communication load of satellite networks.

Generation of Low-Delay and High-Stability Multicast Tree

Delay and stability are two key factors that affect the performance of multicast data transmission in a network.However,current algorithms of tree generation hardly meet the requirements of low delay and high sta-bility simultaneously.Given a general network,the generation algorithm of a multicast tree with minimum delay and maximum stability is an NP-hard problem,without a precise and efficient algorithm.To address these challenges,this paper studies the generation of low-delay and high-stability multicast trees under the model of spanning tree based on stability probability,degree-constrained,edge-weighted for multicast(T-SDE).A class of algorithms was proposed which creates the multicast tree greedy on the ratio of fan-out to delay(RFD)and probability of stability of terminal to obtain a high performance in multicast.The proposed algorithms greedily select terminals with a large RFD and a high probability of stability as forwarding nodes in the generation of the multicast tree,where the larger RFD and higher stability of upstream nodes are beneficial to achieve a low transmission delay and high stability in multicast.The proposed RFD can be compatible with the original model,which can take advantage of network connectivity during the generation of a multicast tree.This paper carries out simulation experiments on Matlab R2016b to measure the performance of the proposed algorithm.Experimental results show that the proposed algorithm can provide a smaller height,higher stability,and a lower transmission delay of the resulting multicast tree than other solutions.The spanning tree of the proposed algorithms can support low transmission delay and high stability in multicast transmission.

Application Layer Multicast Model with Low Delay and High Stability

As an alternative of Internet protocol(IP)multicast,application layer multicast(ALM)is widely used with the advantage of simplicity and flexibility.However,the existing problems of large transmission delay and poor stability limit the application and development.In this article,to solve these problems,an ALM model based on node potential(NP)and topological index(TI)is proposed.The proposed model considers the factors of node capability and node distance in constructing and maintaining multicast tree to reduce transmission delay and increase stability,and thus it improves the application level in real-time multimedia multicast.The computer simulations prove that the proposed model reduces the ALM transmission delay,increases multicast tree stability effectively,and improves the ALM performance,and therefore it is suitable to apply in large-scale real-time multimedia environment.

Opportunistic Relaying Technique over Rayleigh Fading Channel to Improve Multicast Security

The performance of Rayleigh fading channels is substantially impacted by the impacts of relays, antennas, and the number of branches. Opportunistic relaying is a potent technique for enhancing the effects of the aforementioned factors while enhancing the performance of fading channels. Due to these issues, a secure wireless multicasting scenario using opportunistic relaying over Rayleigh fading channel in the presence of multiple wiretappers is taken into consideration in this study. So the investigation of a secure wireless multicasting scenario using opportunistic relaying over Rayleigh fading channel in the presence of multiple wiretappers is the focus of this paper. The primary goals of this study are to maximize security in wireless multicasting while minimizing security loss caused by the effects of relays, branches at destinations and wiretappers, as well as multicast users and wiretappers through opportunistic relaying. To comprehend the insight effects of prior parameters, the closed form analytical expressions are constructed for the probability of non-zero secrecy multicast capacity (PNSMC), ergodic secrecy multicast capacity (ESMC), and secure outage probability for multicasting (SOPM). The findings demonstrate that opportunistic relaying is a successful method for reducing the loss of security in multicasting.

Secure Wireless Multicasting through Nakagami-m Fading Channels with Multi-Hop Relaying

The additional diversity gain provided by the relays improves the secrecy capacity of communications system significantly. The multiple hops in the relaying system is an important technique to improve this diversity gain. The development of an analytical mathematical model of ensuring security in multicasting through fading channels incorporating this benefit of multi-hop relaying is still an open problem. Motivated by this issue, this paper considers a secure wireless multicasting scenario employing multi-hop relaying technique over frequency selective Nakagami-m fading channel and develops an analytical mathematical model to ensure the security against multiple eavesdroppers. This mathematical model has been developed based on the closed-form analytical expressions of the probability of non-zero secrecy multicast capacity (PNSMC) and the secure outage probability for multicasting (SOPM) to ensure the security in the presence of multiple eavesdroppers. Moreover, the effects of the fading parameter of multicast channel, the number of hops and eavesdropper are investigated. The results show that the security in multicasting through Nakagami-m fading channel with multi-hop relaying system is more sensitive to the number of hops and eavesdroppers. The fading of multicast channel helps to improve the secrecy multicast capacity and is not the enemy of security in multicasting.

5G车联网中安全高效的组播服务认证与密钥协商方案

5G车联网(5G-V2X)中,内容提供者通过以点对多的传输方式向属于特定区域的一组车辆提供服务消息。针对于车辆获取组播服务遭受的安全威胁与隐私泄露问题,该文提出一种认证和密钥协商方案用于内容提供者与车辆之间的组播服务消息传输。首先,采用无证书聚合签名技术批量验证群组内所有车辆,提高了认证请求的效率。其次,基于多项式密钥管理技术实现安全的密钥协商,使得非法用户或核心网络无法获取共享会话密钥。最后,实现了群组内车辆的动态密钥更新机制,当车辆加入或离开群组时,内容提供者只需要发送1条密钥更新消息即可更新会话密钥。基于形式化验证工具和进一步安全性分析表明,所提方案可以保证匿名性、不可链接性、前向和后向安全性以及抗共谋攻击等安全需求。与现有方案相比,计算效率提高了约34.2%。

MRNDA:一种基于资源受限片上网络的深度神经网络加速器组播机制研究

片上网络(Network-on-Chip,NoC)在多处理器系统中得到了广泛的应用.近年来,有研究提出了基于NoC的深度神经网络(Deep Neural Network,DNN)加速器.基于NoC的DNN加速器设计利用NoC连接神经元计算设备,能够极大地减少加速器对片外存储的访问从而减少加速器的分类延迟和功耗.但是,若采用传统的单播NoC,大量的一对多数据包会极大的提高加速器的通信延迟.并且,目前的深度神经网络规模往往非常庞大,而NoC的核心数量是有限的.因此,文中提出了一种针对资源受限的NoC的组播方案.该方案利用有限数量的处理单元(Processor Element,PE)来计算大型的DNN,并且利用特殊的树形组播加速网络来减少加速器的通信延迟.仿真结果表明,和基准情况相比,本文提出的组播机制使加速器的分类延迟最高降低了86.7%,通信延迟最高降低了88.8%,而它的路由器面积和功耗仅占基准路由器的9.5%和10.3%.

基于流水线计算的3D NoC测试规划研究

为了提高三维片上网络(3D NoC)资源内核的测试效率,提出一种在功耗约束条件下多播流水线并行测试同构核与单播测试异构核相结合的方法对IP核进行测试。为了减少测试数据因资源冲突而进行等待的时间,设计一种改进XYZ路由算法,并采用改进人工蜂群(ABC)算法求解最佳测试规划方案。以国际标准电路测试集ITC'02作为实验对象,结果表明,测试时间最大优化率达到15.45%,与其他测试规划方法相比该文方法能有效地提高并行测试效率。

基于遗传-蚁群优化算法的QoS组播路由算法设计

为了提高网络路由性能,提出并设计了一种基于遗传-蚁群优化算法的服务质量(quality of service,QoS)组播路由算法。首先,设计了自适应变频采集策略用于采集网络与节点信息,以此获得网络和节点的状态,为后续路由优化提供数据支持;其次,计算路径代价,将路径代价最小作为优化目标,建立QoS组播路由优化模型,并设置相关约束条件;最后,结合遗传算法和蚁群算法提出一种遗传-蚁群优化算法求解上述模型,输出最优路径,完成路由优化。实验结果表明,所提算法可有效降低路径长度与路径代价,提高搜索效率与路由请求成功率,优化后的路由时延抖动较小。

一种基于RTP/Multicast的流媒体传输系统设计

流媒体技术是当前研究和开发的一个热点。在开发基于多服务器的大规模流媒体服务器平台中，该文提出了一种基于RTP/Multicast的流媒体传输系统。这个传输系统实现了统一传输模型，即单播和组播配合实现对热门影片的组播，还实现了基于RTCP反馈的简单流量控制算法NFC。该系统已经实现，并在做进一步的完善。

WDM全光网络中Multicast的寻径与波长分配算法

在WDM全光网络中实现实时Multicast功能是计算机网络的应用要求,也是现代计算机网络的重要特征。该文提出了一种在WDM全光网络中实现实时Multicast的算法。该算法以辅助的波长图为基础,将寻径与波长分配统一进行,构造满足延迟约束的、具有较低成本的Multicast树,实现Multicast功能。

满足QoS约束的加速加权分布式动态Multicast算法

在计算机网络中高效实现具有延迟等ＱｏＳ约束的Ｍｕｌｔｉｃａｓｔ功能，是计算机网络应该提供的一种基本功能，是保证视频会议系统、多媒体教学系统、视频点播系统（ＶＯＤ）、网上拍卖等应用得以实现的基础．针对这一问题，提出了一种加速加权方法，根据已经经过的部分路径的延迟和剩余延迟，将成本加速加权，利用加权成本构造Ｍｕｌｔｉｃａｓｔ树．利用该算法，可以在计算机网络中以分布式方式建立接近最小成本、满足延迟约束条件、适于实时通信的动态Ｍｕｌｔｉｃａｓｔ连接，避免了传统方法将成本和延迟分别考虑、大量回溯的弊端．

适用于分布式虚拟环境的MULTICAST通信协议设计与分析

本文主要讨论了分布式虚拟环境（ＤＶＥ）的通信特点及其对网络通信协议的要求，提出了一个基于Ｍｕｌｔｉｃａｓｔ分组（ＭＧ）的通信思想，据此设计实现了一个适用于ＤＶＥ系统的通信协议（基于发送方的分组Ｍｕｌｔｉｃａｓｔ通信协议－－ＳＩＧＭＰ）．最后论文对Ｍｕｌｔｉｃａｓｔ通信和ＳＩＧＭＰ协议进行了详细的性能分析和讨论，推导出了对Ｍｕｌｔｉｃａｓｔ通信进行性能分析的一般方法．

Programming Technology of IP Multicast and Broadcast Based on Socket

Beginning with the simple introduction of socket which is the most commonly used application program interfaces in UNIX/LINUX communication domain, the concrete programming procedures to realize multicast and broadcast based on socket is provided, according to TCP/IP protocol in LINUX system. The acquiring and converting of broadcast destination address and multicast address, the setting of multicast options, the joining in and withdrawing from the multicast group, and the receiving and sending of datagram are all demonstrated in it, the related system calls and simple explication of C programming are also included.

多级互连网络中的multicast通信

ＭＰＰ系统中的并行通信是目前并行处理研究的热点，改善并行通信性能、提高网络吞吐率是促进ＭＰＰ性能发挥的关键问题．ｍｕｌｔｉｃａｓｔ通信是区别于点到点通信的一对多通信方式，因而功能更强大，使用起来更灵活方便，在并行处理中应用十分广泛．文中以基于开关元件实现结点间动态互连的多级互连网络为背景，研究了ｍｕｌｔｉｃａｓｔ通信路由算法的效率．针对现有路由算法的不足，提出了基于功能扩展的交换开关的ＳＢＭＴ路由算法，并进一步作出了性能分析和比较．

面向ICN组播的基于感染力的汇聚点部署方法

在组播系统中,汇聚点(RP)作为组播树的根节点,负责将源内容引入组播树。RP汇集了网络中的流量,容易成为网络性能瓶颈。为了提高网络容纳的组播组数量(组播容量),可以将更多的网络节点升级为RP。相比于传统的IP组播,信息中心网络(ICN)组播大幅降低了RP管理代价,从而允许部署大量RP。因此,本文基于ICN组播展开研究。但是,由于设备升级成本和系统稳定性等原因,ICN组播中RP数量仍然不能太多。现有基于P中值模型法的RP部署方法没有充分考虑到RP之间的负载压力,容易导致RP计算资源浪费和一些RP的负载过重,限制了组播容量。因此,本文提出了一种面向ICN组播的基于感染力的RP部署方法。该方法首先提出了一种组播感染力指标,用于刻画RP之间的负载压力。其次,利用组播感染力,提出了一种基于贪心策略的RP部署方法,优先将负载压力小的节点升级为RP。2组实验证明,在部署15个RP的情况下,本方法相比P中值模型法,将组播容量提高3.48倍;在组播容量都达到9000组时,本方法所需的RP数量仅为p中值模型法的29.4%。

A distributed on-demand bandwidth-constrained multicast routing protocol for wireless ad hoc networks

To meet the bandwidth requirement for the multicasting data flow in ad hoc networks, a distributed on- demand bandwidth-constrained multicast routing （BCMR） protocol for wireless ad hoc networks is proposed. With this protocol, the resource reservation table of each node will record the bandwidth requirements of data flows, which access itself, its neighbor nodes and hidden nodes, and every node calculates the remaining available bandwidth by deducting the bandwidth reserved in the resource reservation table from the total available bandwidth of the node. Moreover, the BCMR searches in a distributed manner for the paths with the shortest delay conditioned by the bandwidth constraint. Simulation results demonstrate the good performance of BCMR in terms of packet delivery reliability and the delay. BCMR can meet the requirements of real time communication and can be used in the multicast applications with low mobility in wireless ad hoc networks.

IP MultiCast技术在远程教学系统中的应用

介绍了一种先进的远程教学系统及系统所实现的各部分功能 ,着重介绍了IPMultiCast技术以及这种技术在音频 。

FEC编码在可靠Multicast中的应用分析

在Ｉｎｔｅｒｎｅｔ差错恢复技术及前向纠错（ＦＥＣ）编码的基础上，分析了可靠组播（Ｍｕｌｔｉｃａｓｔ）应用中采用ＦＥＣ进行差错恢复的性能，并提出一种基于ＦＥＣ的自适应可靠Ｍｕｌｔｉｃａｓｔ协议．结果表明，在通常的网络环境中，采用结合ＦＥＣ编码的混合ＡＲＱ差错恢复方式，能够降低可靠Ｍｕｌｔｉｃａｓｔ通信的平均分组传送次数，减小分组重传时间，从而提高数据吞吐量，而且在通信过程中根据网络状况动态地改变预发送纠错分组数。