Nortel帧中继网上多业务集成传输的研究与实现

采用帧中继网络同时传输语音和数据是一种低投入、高效益的途径。北方电讯的Passport4460是一种带语音模块的路由交换设备，它具有先进的数据压缩和带宽管理功能，使语音、传真、视频和传统数据等各类流量可以通过选择不同的网络链路进行传输。基于该设备，研究了帧中继网络上语音和数据集成传输的关键技术，并给出了其实现方案。     

Traffic management strategy for delay-tolerant networks

Messages in delay-tolerant networks (DTNs) are generally classified by relative priority into low, medium, and high priority classes, thus creating challenges in structuring scheduling and drop policies of a traffic management system. This study proposes a novel traffic management strategy for DTNs. The proposed scheme improves message deliveries of different priority classes by utilizing message properties such as estimated total number of replicas, elapsed time, and remaining time-to-live. A delete mechanism of delivered messages is also incorporated to use buffer space efficiently. The performance of the proposed strategy is verified via implementation of a simulation model along with existing scheduling and drop policies and is tested with two well-known real-world trace datasets. The results demonstrate that the proposed strategy yields improved message deliveries of high priority as well as medium and low priority classes.     

Scalable DeNoise-and-Forward in bidirectional relay networks

In this paper a scalable relaying scheme is proposed based on an existing concept called DeNoise-and-Forward, DNF. We call it Scalable DNF, S-DNF, and it targets the scenario with multiple communication flows through a single common relay. The idea of the scheme is to combine packets at the relay in order to save transmissions. To ensure decodability at the end-nodes, a priori information about the content of the combined packets must be available. This is gathered during the initial transmissions to the relay. The trade-off between decodability and number of necessary transmissions is analysed and simulations show, that S-DNF is able to provide a better trade-off than traditional schemes at high SNR.     

多向中继网络中的协作复用技术

为提升多向中继网络的频谱效率,提出一种基于协作复用的传输技术,多个配置单天线的中继节点对空间复用信号进行放大转发,接收节点收到足够数量的样本即可译码,减少了发送时间,提高了传输的有效性。针对三节点数据交互的情形,分析了该技术的频谱效率。结果表明,在高信噪比区域,相对于传统的和基于协作分集的传输方案,该技术的频谱效率分别提升了100%和200%。     

中继网络一种改进的QAPF调度算法研究*

本文针对QAPF调度算法存在的吞吐量与公平性矛盾的问题,提出了一种改进的QAPF调度准则(RQAPF),该准则利用队列门限值降低了队列状态信息对调度准则的影响,保证了用户的公平性。但与QAPF调度准则相比,降低了系统吞吐量,进一步提出了具有载波配对的RQAPF调度算法(SubPairRQAPF),仿真表明该算法在满足系统公平性要求的同时能够提高频谱利用率。     

Traffic control in ATM networks

This paper presents a framework to study the problem of traffic control in ATM networks. Bursty traffic sources are modelled by Interrupted Bernoulli Processes. Probability of violation and dimensioning issues are addressed for the leaky bucket mechanism and the (L,M,T) mechanism, proposed by the authors. We present two schemes to demonstrate that improved statistical multiplexing can be achieved if the traffic control mechanisms are not used in isolation for each session, rather they are used on groups of sessions. In the first scheme, traffic control is performed on the aggregate traffic of a group. In the second scheme, traffic control is performed on single sessions with information about the status of all the sessions of the group being available and used at each traffic control mechanism. Numerical examples that illustrate the improvement in statistical multiplexing as a result of the above schemes are presented.     

无线协作网络中的能量有效性中继选择算法

研究了无线协作网络中的中继选择问题,允许中继具有缓存数据的能力,提出了一种带有buffer的能量有效性中继选择算法,以延长网络生命周期并提高系统吞吐量。该算法综合考虑链路信息,中继的队列状态以及节点的剩余能量信息,通过加权效用公式选择最优接收数据中继与最优发送数据中继。考虑源节点与中继节点间的功率分配,以降低因源节点到中继节点以及中继节点到目的节点间的信道速率不一致所引起的系统丢包率。仿真实验结果表明,该算法有效地延长了网络的生命周期,随着中继个数的增加网络吞吐量有明显的提高,考虑功率分配后,有效降低了系统丢包率。     

Optimal power allocation for cognitive relay networks: amplify-and-forward versus selection relay

We consider a cognitive relay network which is defined by a source,a destination,and cognitive relay nodes and primary user nodes.In this network,a source is assisted by cognitive relay nodes which allow coexisting with primary user nodes by imposing severe constraints on the transmission power so that they operate below the noise floor of primary user nodes.In this paper,we mainly study the power allocation strategies of this system to minimize the outage probability subject to total and individual power c...     

在认知中继网络中基于放大转发与最佳中继的最优功率分配算法

由于受认知无线电与中继通信技术的启发,提出了一种认知中继网络模型.该模型由源节点、目的节点、认知中继节点及主用户(primary user,PU)构成.认知中继节点以与PU共存的方式为源节点辅助传输信息到目的节点,只要保证其对PU通信造成的干扰在PU干扰门限值以下.假设源节点、目的节点和认知中继节点之间的瞬时信道边信息(channel side information,CSI)和认知中继节点到主用户之间的均值信道增益已知的前提下,研究该模型中的认知中继节点分别采用放大转发(amplify-and-forward,AF)和基于AF的中继选择(selection AF,S-AF)下的功率分配策略,该策略以最小化系统中断概率为目标,同时也满足认知中继节点的发射功率约束(包括总发射功率和个体发射功率约束)和对主用户的干扰功率约束.最后,通过数值仿真来验证推导出的功率分配策略.仿真结果表明:本文提出的最优功率分配策略,无论在AF,还是S-AF下,均能明显的改善系统的中断性能和平均吞吐量;同时在S-AF下最优分配策略可以得到更高的平均吞吐量,因此中断概率更小.     

基于帧中继网络的电子商务信息安全系统

本文介绍了基于帧中继网络的信息安全体系;提出帧中继网络系统安全整体结构;简要介绍帧中继网络安全面临的威胁;描述了帧中继加密系统的组成与功能、系统的典型应用、实现原理及密码技术。     

A clustering deployment scheme for base stations and relay stations in multi-hop relay networks

Suitable deployment for the base stations and the relay stations is one of the most important features for the portable devices to obtain a high data transmission rate in multi-hop relay networks. In this paper, a novel clustering algorithm is proposed to select the appropriate deployment locations for the base stations and relay stations from the candidate positions by accounting for the traffic demands and using the uniform cluster concepts. Based on the different candidate positions, the proposed scheme makes an adaptive decision for selecting the deployment sites of the base stations and relay stations. A reasonable network throughput and coverage ratio can be obtained by balancing the network load among the clusters. Our simulation results indicate the superior performance of our proposed deployment scheme in achieving the appropriate performance for the network throughput and coverage ratio. Additionally, a suitable deployment budget can be utilized in multi-hop relay network systems.     

基于QoS的MIMO中继网络容量分析

设计了一种MIMO中继网络模型,研究并分析了带有服务质量(QoS)需求的中继网络容量,推导了MIMO中继网络容量的近似表达式.仿真分析表明,在一定的信噪比条件下,随着中继节点数的增加,网络的可达容量性能明显得到改善,且在低信噪比(SNR)区域,所提方案也可以获得较高的容量增益.     

基于能效的多天线中继网络波束形成设计

为了提高放大转发多天线中继网络的能量效率,提出了一种基于能量效率的波束形成算法,在满足中继功率约束条件的同时,最大化系统归一化信噪比.最终得到的优化问题是一个非凸的优化问题,难以求解.将其简化为一个一维的优化问题,可以利用求导的方法进行求解.仿真结果表明:与基于信噪比的波束形成算法和未使用波束形成的放大转发方式相比,所提算法可显著提高系统的能量效率.     

基于多用户QoS的中继系统功率分配算法

研究了非再生中继满足不同用户速率需求的公平性功率分配问题。提出了基于用户期望速率比例公平性功率分配算法,由于源端无法预先接收用户期望速率信息,该算法在实际操作中存在一定的不可操作性。进一步提出了预均分公平性功率分配算法,可弥补基于用户期望速率比例公平性功率分配算法的不足。仿真结果表明,两种算法都实现了保证用户服务质量(QoS)的最优功率分配以最小化用户速率与期望速率差值,节约网络资源的优化目标。     

Multi-hop multicast path construction in modern wireless relay networks

In recent years, multicast over wireless access networks has become a popular research topic. However, if relay nodes are supported in such a network, forming an efficient multicast topology becomes a challenging task. Since existing works fail to solve this problem satisfyingly, we in this paper propose a multi-hop multicast routing scheme for modern wireless relay networks. First, we formulate this important problem as Multi-Hop Multicast Maximization (MHMM), which involves forming a resource allocation of the base-station and relay stations in order to maximize the number of recipients with the given resource budget and channel conditions. To solve MHMM, we propose a heuristic called Multi-Hop Path Selection (MHPS). We prove that MHMM is NP-complete, and also analyze MHPS’s computational complexity and its worst-case performance. The results of simulations conducted to evaluate the heuristic’s performance demonstrate that, under variant conditions, MHPS utilizes bandwidth resources and relay nodes effectively such that it significantly outperforms all existing approaches. Moreover, its performance difference to the optimum is bounded. To the best of our knowledge, MHPS is the only scheme that focuses on this important issue and achieves such a satisfactory performance.     

IPv6 based relay gateway protocol in hybrid networks

During the past few years, WMAN (Wireless Metropolitan Area Network) and WLAN (Wireless Local Area Network) provided fast, convenient and reliable solution for all kinds of users. With the development of the communication technology, the future wireless networks will allow mobile users access Internet anywhere, anytime. Therefore, it is a natural trend to combine different wireless networks to provide a seamless roaming for users. It is feasible for mobile terminal which have multiple modes to handoff between different networks. A relay gateway protocol for the WLAN-mode nodes (mono-mode WLAN nodes and dual-mode nodes) in the hybrid network of IEEE 802.16 WMANs and IEEE 802.11 WLANs is proposed to provide wider mobility. Dual-mode mobile nodes with good service can provide WLAN links to nearby WLAN-mode nodes with bad service or out of the WLAN coverage. Simulation results show that the relay gateway scheme can improve network performance of the hybrid networks. Moreover, the relay gateway method can bring additional service coverage and increase the capacity of WMANs and WLANs.     

通信网络中基于协作中继重传策略

针对信息包在通信网络中多播传输进行了研究,提出通信网络中基于协作中继重传策略。当信息包直传失败时,源节点协作多个中继节点对多个丢失的信息包进行编码重传。在重传阶段根据反馈机制结果采取随机接入方式优先对有机会编码的丢失信息包进行组合,然后通过牺牲之前重传过程中传输失败的节点为信息提供空间分集增益,从而减低重传次数。最后在不同信道环境下,该策略与未协作NCARQ和传统ARQ进行Monte Carlo仿真。仿真结果表明,在多中继信道条件优于源-目的信道的情况下,利用协作网络编码进行重传有效地提高网络吞吐量,且该策略利用协作空间分集降低了由于相干性而导致性能不佳的状况。     

协作译码转发中继网络中的安全能效分析

基于物理层安全理论,研究了存在窃听用户情形下协作译码转发中继网络中的安全能效问题。安全能效,即消耗单位能量所能传输的保密信息量。在满足各节点发射功率约束和中继处最小译码速率要求下,通过功率控制实现系统的安全能效最大化。针对目标函数非凸问题,利用分式规划和DC(Difference of Convex functions)规划理论把目标函数分解为子函数通过迭代来进行优化求解。仿真结果表明,能效优化可以显著提升系统的安全能效。